No Room at the (Good) Inns

The next day the clouds are still towering above the mountains. Their fluffy-seeming shapes are pregnant with supercooled water, yearning for something to freeze on, especially something thin and sharp like my propeller blades or the leading edges of my wings and stabilizers. I won't fly through them, but today their bases are higher, and I have mapped a few passes that will allow me to remain clear of terrain while still comfortably below the cloud bases. The bad weather is predominately on the other side of the mountains in the plains, and that I can deal with. I take a cab out to the airport and prepare for flight.

The airplane has waited patiently for me, and is ready to go. Fuel is on account, so all I have to do is verify that the tanks have been filled per my request and I have no paperwork to do with the FBO. I notify company of my intentions and various fallback plans and fire up the engines. Oil pressure rises, suction indicators clear, and the discharge light on the ammeter extinguishes. It showed a discharge as I drew current from the battery to start the engines, but now the needle flips past the zero to the positive side of the scale to show that the alternators are now charging the battery. No, I lie: in this airplane it's a digital ammeter, so it's just the flip of the sign, but my memory stores the information as if it were from as analogue instrument. At the end of the engine run-up I will ensure that the battery is charged, that the alternator output is sufficient, and that the load is balanced between the two alternators. A split could indicate a problem with one of them, or its accompanying voltage regulator. All is well and I depart, heading towards my chosen mountain pass.

I have entered GPS waypoints corresponding to the valley choices I have to make, but they are a back up to the very old fashioned visual flying I will do, identifying my valleys by the shapes of the rivers and the valleys. It's much easier to do by looking at the spacing and shapes of the peaks, but the clouds cover them. I can't use conventional navigation aids, because the rocks block their transmissions. This was before I got my tablet GPS toy, so I'm using paper charts. Once upon a time people did this without charts at all, and of course if I flew through this range all the time I would know it well enough not to need the map, but I can't know every mountain and don't expect myself to. The crucial piece of navigation on this route is to turn right into a valley that will not be immediately visible. This will be after I reach a very distinctive hook-shaped lake. When I do, it's unmistakable, and I make my turn, with the clouds darkening above. The valley widens and diverges into many valleys, but I don't have to choose one because the terrain is dropping away below, the mountains fading to mere foothills. Under the shadow of the clouds I notice how bright my strobes are. It's recommended to turn strobes off in cloud or dark night conditions, but it's broad daylight and I am not in cloud. And then I remember that this airplane doesn't have wingtip strobes. The bright flashes are lightning. The storm is far enough north that I am not concerned about it striking the airplane. I am not dodging clouds or in turbulence or heavy rain. I see photographs sometimes of lightning that show it looking like it looks in my eyes but I think you have to use a fancy camera with a long exposure. My pictures just look like dark clouds. I later drew a postcard to show what it looked like to me, but I must have forgotten to photograph that one before I sent it, because I don't see it with the others.

The thunderstorms are the signal that I have completed my trip through the mountains, and am on the plains. It isn't much further to my destination, and I land and taxi up to the FBO we use there. They are repaving their apron, but they know my by the airplane and value our business, so marshal me to a prime parking spot and greet me enthusiastically. It's nice to be known. I'm bringing this airplane here alone. The other crew member will meet me when the weather becomes suitable for our main job.

I call my usual hotels here, but it's the local rodeo week, and all the rooms are occupied. Every hotel I know is full. The FBO attendant steps up and keeps calling, working his way down the chain until we find an available room. It's in a motel. I watch a little anxiously out of the cab as we go down the highway to find it. The parking lot is right off the highway. The building isn't in terrible repair. I check in at the office, paying in advance, because that's what they require. They give me a metal key and direct me back outside. My room is on the ground floor, in the centre of the horseshoe facing the parking lot. It's not necessary to go through a lobby or past hotel security to reach it. The door is not very heavy and I think I could kick the deadbolt out of the wood myself. I close the door and the curtains, drop off my stuff and go for dinner.

At the end of the day I think about the fact that I feel safer alone in an airplane in a thunderstorm in the mountains than I do in a motel in Alberta oil country. Does this speak to the society I live in, or to the well-documented human failing when it comes to judging and acting on relative risks? I don't know.

Death Rates

I'm IFR in the flight levels on a clear VMC day. The IFR part means I'm following a set of rules and procedures ("Instrument Flight Rules") designed for pilots of aircraft in weather conditions that don't allow them to navigate by looking out the window. The flight levels part means I'm flying above about 18,000'. In Canada the "transition altitude," between altitudes designated by the local air pressure and those altitudes designated by a universal standard pressure setting, is 18,000'. One never flies at 18,000', but instead sets the altimeter to 29.92 and flies at flight level 180. I don't know how our transition level was determined. Our highest mountain is about 19,000', so it wasn't set relative to that. VMC is "Visual Meteorological Conditions," that is weather that permits navigation just by looking out the window.

So why am I IFR in VMC? Because in Canada everyone operating in the flight levels is required to do so under an IFR clearance. It's a safety regulation. I have to fly only as directed and cleared by ATC, in order to ensure separation from all other aircraft. And I'm up this high because this is where I need to work. There's only half as much air pressure up here as at sea level, which means only half as much oxygen per breath, so I'm wearing a mask that provides me with supplemental oxygen. The masks do a great job of that. Testing my blood oxygen level always shows me at 98 or 99% saturation, the same level I get sitting on my chesterfield at home. (The tester looks at my blood by shining a light through my fingernail: it doesn't take a blood sample). Only problem is that in providing a tight seal around my face and being secured to my head underneath my headset, the mask give me no opportunity to eat or drink during the flight. Air before food.

The mask also interferes with the seal between my headset earpieces and my ears, so it's a little noisier with the mask on. Even noisier when my noise cancelling cuts out because my headset batteries died. I'm not sure if the noise cancelling "works harder" to keep up, or if it has the same battery consumption regardless of the ambient noise, and this is just coincidence. I use rechargeable batteries, which when they are new last about fifty hours in the airplane before they die, but after many cycles have shorter lives. I have numbered all my rechargeables and track how long each set (the headset takes two AAs) lasts before it dies. When they can't go a full flight, they get retired to a plastic baggie in my kitchen. Eventually they will go to recycling, when I figure out where to recycle rechargeables. They last pretty well: there are only six batteries in the retirement baggie and I've been using rechargeables in my headset and flashlights for at least eight years.

I change batteries and then notice I'm off my heading. The autopilot has disconnected. I must have hit the button. I reset it and then turn to a new heading, but something doesn't look right. The GPS says I'm going where I want to be, but the heading indicator is way off. I reset it to the compass, and it follows for a while, but soon loses interest again. The heading indicator is powered by two engine driven vacuum pumps, one of which I reported close to needing replacement a few days ago. The suction gauge shows slightly less of a vacuum than ideal, but in the green range and no less than it has for a few weeks. The other part of the instrument shows both vacuum pumps on line. The attitude indicator, powered by the same system, still appears to be working. Legally I'm required to inform ATC of the failure of a heading indicator. I do so, and they seem confused. No, it isn't affecting my operation at all. I'm using an electronic guidance system, and I will be landing at an airport that I'll be able to see sixty kilometres away. I don't need it for the flight. Maybe people don't routinely comply with that regulation anymore.

Before I land, the stupid thing comes back to life. Charming. I'm far from base, but I call maintenance so they can order one, or pull one out of another plane or something for when I come back. They don't have any troubleshooting tips for a zombie heading indicator. It's working now, but it's not reliable, so I snag it. That is, I write in the journey log that it is not operating correctly. This will limit our operations to day VFR (the looking out the window counterpart of IFR) only, which is a huge pain in the neck, because it prevents me from continuing the work above FL180, even though its effect on safety is negligible. I have had transient problems with equipment that never recur, but usually they hint at trouble and then throw a full failure if ignored. I think I've only seen simple heading indicators (as opposed to the more expensive and complex HSI) fail twice before in about 7000 hours of flying. And one was a simple fix, turned out that there was an installation error that had made a screw come loose. I wonder if the suction line is leaking or blocked or something. Nothing I can do about it, anyway.

Photo Finish

I checked with maintenance regarding my recent post about the fire protection system. Our fire detector is photocell activated. The photocell is sensitive to a particular wavelength of light, supposedly characteristic of fire.

I didn't get to ask the obvious questions about why fire detection systems aren't overwhelmed with false positives from the sun, an awesome source of almost every electromagnetic wavelength, and able at some time of the day or some practical bank angle, to shine through every chink and opening in an engine cowling. An apprentice had a more pressing question about reinstallation of an exhaust manifold, and I was wearing silly girl shoes for a social event, so I teetered back out of the hangar to the office and left the maintenance to the maintainers.

Along with the answer to my question, and before the apprentice needed direction, I received the following story. A certain air carrier's night maintenance crew (they know who they are) conducted an inspection on at least one of the carrier's fleet. Their fire detection system used visible light, and the crew followed the manufacturer's instructions to test it by shining a flashlight on the detectors. The system failed the test. The crew was preparing to replace several thousand dollars worth of aviation grade electronic gear, when someone realized that that instructions were as old as the system, twenty years or so, and predated the invention of the LED flashlights the crew were using. The diodes were not emitting the necessary wavelength to trigger the detector, because when the instructions said "flashlight" an incandescent flashlight was assumed.

 The Wikipedia article on Fire Detection suggests that our photocell might be tuned to multiple wavelengths, possibly including UV and/or IR to compare the ratios. This still doesn't explain how an ordinary incandescent flashlight would trigger it, but the sun wouldn't, but does make the concept of photometric flame detection clearer. While looking for more information on flame detectors I discovered that there is a whole new generation of fire detection that uses machine intelligence to recognize the appearance of actual flames, something that is pretty fricking clear to humans. Combined with smoke detectors, something a commenter suggested on the previous post, there are enough different kinds of combustion detectors on aircraft to warrant a survey post on the topic, some time when my working day is shorter.

I was also entertained by the Wikipedia article on the Flashlight, which explains why Americans call them flashlights. The earliest zinc–carbon batteries could not provide a steady electric current so when combined with the inefficient carbon-filament bulbs, the result was a light that frequently blinked off so the battery could recover.

Hotel Pet Peeves

There are commercial pilots who don't spend a generous proportion of their nights in hotels. But given that you're in charge of a machine that goes places, and that you are legally required to sleep, there's a good chance that if you're a pilot, you know about these.

I'll start with lamps. When you're at home you know where the light switches are, even if you still haven't completely memorized which switch in the group of three gets the kitchen and which one gets the porch or something else. When you're in a hotel, you can't be expected to know this, so hotels generally have the switches right on the lamps. I don't think they do this to avoid customer confusion over which light switch does what. I think they do it because it's cheaper to put standing lamps in a room and plug them in than it is to install ceiling lights and wire switches. And perhaps because they realize that if they make it a royal pain in the neck to go around and turn on the lights, fewer guests will do it, and they will save on their electrical bills.

So the switches are on the lamps. The thing with a lamp is that it is always either on or off. If it's off, it is dark, so you have to find its switch in the dark. If it's on, it's bright, so you have to find its switch by staring at a bright orb, or groping with your fingers near a hot surface. Lamp controls can be on the lamp base, anywhere on the cord, the collar where the bulb attaches, or somewhere nearby. You might have to press it, pull it, turn it, slide it, or flick it. Or you may just have to reach inside the fixture and retighten the bulb, because the last user gave up before finding the switch. Or stole the lightbulb. Many of the switches on hotel lamps are perfectly logical ways of turning a light on and off. It's just that by definition you have to operate them in unsatisfactory lighting conditions. I hate the little knobs you have to turn inside the fixture next to the bulbs. Sometimes they only turn one way, and I only figure that out after trying to push them. I can't imagine what they're like for the arachnophobic. (I quite like spiders myself. The other day I accidentally vacuumed one up and felt so badly I turned off the vacuum and left it there for a week so the spider could find its way out if it was okay. I'm pleased to report it's back at work building webs. Or at least this spider looks a lot like the first one).

Then there are design decisions made in bathrooms. I guess they aren't decisions. No one would decide. "I think a user of this bathroom should either have to squeeze under the towel rack in order to close the door, or have to straddle the door while sitting on the toilet in order to not have the door bang her in the knees." Or "it would be fun if you have to decide how much toilet paper you will need before sitting down, so let's put the toilet paper dispenser somewhere you can't reach it from the toilet." I stayed recently in a hotel with a beautifully renovated bathroom that had no place for amenities in the shower whatsoever. Being tall, I managed to balance a bar of soap on top of the shower head, but shampoo, conditioner, nowhere to put them. I think that was also the hotel that had a fancy little console in the desk with 110V AC, USB chargers and an iPod dock--but the telephone was next to the bed with a cord too short to reach the desk.

I should stop whining. My apologies to pilots who spend their official rest in ATCO trailers or primitive bivouacs, and who would kill for a lamp, shower or flush toilet. And I hope everyone in flooded areas--this week it's Calgary, but it maybe somewhere else when this posts--soon has a dry place to sleep, and gets to turn their lamps on.

Double Generator Failure

I found this in my drafts folder, I guess I was saving it for a busy day. I've been punting it a month into the future every month. Obviously I'm busy today, because it published.

I had a double generator failure once. I'll spoil any suspense now by saying it was not a big deal. The designers of this airplane knew that electricity was fickle, newfangled stuff and not to be trusted, so no essential system for VFR flight was electrical. We were VFR and it was a beautiful clear day after the invention of cellphones. The master was on, no visible circuit breakers were popped, and there was no smoke or fire smell. The reset for the generators was under the dashboard. With multiple people on board we could have reset them it in flight, but not knowing why they had popped, we elected to leave them off.
Our destination was a reasonable-sized controlled airport, not at an especially busy time, so we just pulled out a cellphone and called them to tell them we were coming. They cleared us to land, I can't remember whether it was by a steady green light on final or they just gave the clearance over the telephone. Possibly both. They seemed far more stressed about the event than I was. I never consider a communications failure to be a showstopper, especially when I manage to make contact another way. And why on earth had they dispatched firetrucks to follow us down the runway?

It was kind of fun mind you, and the firefighters were friendly. I think they like driving their trucks around, especially when thy don't have to pull anyone's charred remains out of a burning airplane, so they were happy when we thanked them and assured them that there was no problem.

At the time, it was the only twin I knew the systems on, so I didn't realize that some aircraft have electrically activated landing gear. ATC was worried that I might not be able to lower the wheels. The only electrical component of this one is the indication system, and extension can be verified by the thumps from the mains plus visual identification of the nose gear in the mirror on the nacelle. The air traffic controllers knew that in general a systems failure on an airplane could be a bad thing, and must have thought I was being cool and not admitting I could have a gear problem. Communication by cellphone in an operating aircraft is not simple. ATC they have this great button up there in the tower for letting the firetrucks out, so why not? So long as we didn't make the local news.

I can't even remember the reason for the failure. We had it checked out at a local shop and were certified good to go for the next leg of our adventure. I think I was reprimanded by the aircraft owner for saying "electrical failure" instead of just "comm failure." He was a need-to-know kind of guy and I'm more of an anything-that-might-be-relevant gal.

Advantage Cancelling

I should report in on my new headset. It is a fine thing. It is comfortable. I even find myself looking forward to putting it on in the morning, reminding myself of a horse I encountered once that was so eager to get out of the paddock for a ride that it walked right up and dropped its head in the halter I was carrying¹. I can hear ATC clearly, and adjust the volume per ear, and there's a jack for me to connect my MP3 player. (It also accepts Bluetooth, but I don't own any Bluetooth devices to test it with). The MP3 jack is interesting because there's a three-position switch controlling how it behaves. Off doesn't allow you to hear the music at all. The middle position allows you to hear the MP3 player and ATC both at once. And the top position automatically mutes the music when there is any activity on the intercom (i.e. from another crewmember speaking or an transmission on an ATC frequency being monitored. I use the top position and it's remarkable effective.

I have some notes here that I didn't post earlier on the research I did before I realized that I would have to buy whatever headset was available. I could have ordered a headset directly from the LightSPEED website. They have international shipping, but they irritatingly only listed American units for the specifications. I wish Americans would learn that only they and the Liberians know what sixteen ounces is, and list things in grams. Also they're one of the sellers that require me to create an account in order to buy something. Hey, I want to click on the item and give you my credit card number. I could have traded in my old headset for a LightSPEED Zulu for $587 with trade-in and shipping, but the new Zulu isn't available through the trade-in plan yet.

I found this video while comparison shopping the Bose and LightSPPED. It's a little out of date, because it's the Bose A20 now, not the X and the new Zulu not the original Zulu, but it's a good discussion of the issues to consider when buying any headset.

Sennheiser lists international units on its website, but it doesn't sell headsets from the website and won't show me the location of a dealer. Their dealer-finder app maxes out at 300 nm, and finds zero that distance from where I was when I needed one. I would have loved to try one as they are known for good technology, but they don't seem to be in the 21st century. I think the headset is heavier, though, too. And then there's this, not so much about the headset as about the very attractive young lady who is wearing it.

I have to wonder about "Certified for commercial duty" though. Is there any country in which functional headsets have to be separately certified for pilots to use them while being paid? Throw one piece of balderdash like that into your marketing statement and I suspect that everything else you have to say is a deceiving distortion, too. Dumb sort of advertising to use on a very informed group. Or so we think.

Q: What do you get when you cross an ape with a pilot?
A: An ape with a big watch.

I was musing though, that my new headset isn't as good as my first ANR headset, even though the technology is better. Back then I was the only one in the company with ANR and I had superhuman abilities. Now everyone has them, so ANR is no longer an advantage over others. It's pretty much essential. I have a coworker who doesn't use ANR, just an old fashioned bulletproof set of David Clarks, and I wonder how he does it. I couldn't go back to a passive headset. I met someone recently whose first boss discouraged his employees from wearing headsets at all, because he said you can't hear the engine properly with it on. His employees weren't bold enough to tell him the reason he couldn't hear the engine, or much else for that matter, was that he had been flying for forty years without a headset.

Also, I wrote down this quotation from someone because it made me laugh, and have now completely forgotten the context: "It was so quiet it was like wearing a Bose noise cancelling headset, but without the noise cancellation, and without the headset.

1. Unfortunately for eager-horse, I was there to catch a different horse. A horse sufficiently less eager to be ridden that it bit me, if I recall correctly.

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Meanwhile a reader in the USA writes:

I am wrapping up my dispatch training and am looking to talk to an active dispatcher. Do you know of anyone that might be able to answer a few questions for me?

If you can help, please drop me a line and I'll connect you two.

Pitt Meadows

I'm at an airplane washing station at Pitt Meadows airport near Vancouver. It's nicely designed with a hose on a reel, a water hook-up, a drain, and some really clever metal stanchions around things you shouldn't run into, like the hose area. These stanchions are everywhere: in front of electrical meters, fire hydrants, anything that would normally have poles or pylons to protect it from vehicles and snowploughs, but they are propeller blades. I don't think they are actually propeller blades, unless someone decommissioned a lot of identical, large-propellered airplanes here, but they look just right, complete with manufacturer's stickers. I can't remember if they were Hartzell or McCauley. They just looked right.

The airplane ends up not totally clean, but better. I rewrap the hose on the reel, winding each coil next to its neighbour from to one end to the other in each layer, and then I get lazy near the end and let it wrap more loosely. As I'm putting away the soap, I see a man come up and unroll and reroll my last messy bit. Sorry, man. I can appreciate his need to have every coil perfectly set on the reel. It really does look nice that way and I regret not having done it that way for you myself.

This is not a really big airport, no scheduled flights and just a little terminal with scenic flights, but for some reason it has a giant avionics shop. They sell Lightspeed headsets, the kind I was trying to get when I got the Bose, and they have the new Zulu 2. I try it, but you can wear one and then the other all you want on the ground without really being able to say which is better. You have to go for a flight, preferably a long flight, before you know whether a headset is doing the job well. The logistics of taking one for a test flight are awkward, though, seeing as the next time I take off, I'll probably not land until I'm back in Alberta. I'm pleased with the Bose, so I'll keep it and not start a crazy game of buying extra headsets.

While I'm here, I get a tour of Maxcraft Avionics. It's quite impressive. Good avionics service is hard to get. I've ferried a lot of airplanes with every kind of broken avionics sometimes to more then one airport to try to get them working. I've also done a lot of flights with gaping holes in the panel where avionics had been removed for repair, sent off somewhere. Big doesn't necessarily mean good, but they have the diagnostic equipment, the certification from every manufacturer I can think of and must have a good reputation. The paint jobs on the aircraft in their hangar suggest that they are trusted by the RCMP and Helijet for major refits, and by a private owner with an intercom problem. Aviation electronics can be really hard to get fixed properly; I'm not sure if it's a black art or a science. If these guys are as good as the facility is impressive, then a lot of people will be coming to Pitt Meadows.

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One more South Sudan link. The people, men and women, have been at war for twenty-one years and pretty much the only experienced, established institution they have is the Sudanese People's Liberation Army. Considering that the median age in Sudan is 18 years and life expectancy 58, over half of South Sudanese have been at war for their entire life, and most soldiers have probably never held another job. The process of demobilizing the army is further confounded by the fact that there are almost no civilian jobs, even if people had the concept of returning to them. I found this article on the reintegration process. It has lots of pictures so you can see what South Sudanese people look and dress like, too.

Can You Hear Me Now?

Morning comes early. I have no recollection of what that hotel room looked like. I was in it an conscious for maybe eight minutes total. I drag my bag down the corridor to the breakfast room with two minutes to spare before the agreed-upon departure time. The cab is already here. I shove a couple of apples and a bagel in my flight bag along with whatever I ordered last night to go, some kind of wrap, I think, and get in the cab.

I check oil and move the airplane from parking back to the pumps and do the run up there, while waiting for the fueller to arrive. He does, and I then finish my preflight inspection and set up charts for the trip and file a flight plan while it's being fuelled. Full all around and caps checked, we take off only a little behind schedule. The wind is calm, so I take off from the apron end of the runway, straight off and then a turn to the northeast as I climb enroute.

I bid adieu to the circuit traffic at Salmon Arm on the ATF and then make a general call on 126.7 to let folks know where I am. The radio doesn't sound quite right. I'm not hearing myself in my own headset the way I should be. The camera operator says he can't hear me. Oh oh. I check the plugs on my headset jack. They're fine. Just my luck to get a headset with a problem. I grab a spare headset. Oh my God it's been a long time since I wore a cheap headset. It's uncomfortable from the earseals, to the weight, to the way it fits on my head, to the amount of noise it lets in. How do people stand these things? I guess I've become a headset snob. From that point of view it's fortunate that the headset swap doesn't fix the problem, because I couldn't work in one anymore, and I'm glad my new headset isn't defective. So is the jack defective? Maybe there's nothing wrong with my old headset. I put my own headset back on and try plugging it in the jack for the other side, trying that intercom jack. No joy. The operator tries the same headset and jack swap in the back.

I can hear the operator, but he can't hear me at all. I'm literally writing notes on my little notepad, then tearing off the sheets and tossing them in the back. He suggests that the intercom may be set incorrectly. It has an electronic control panel that cycles between PILOT, CREW and ALL. I assume that those put the left seat, both front seats or all seats into the intercom circuit, but we test all positions anyway. I'm pretty much in despair about fixing it until I realize that there is a master volume knob for the whole stack and it is in two parts, concentric rings. The inner ring is set to a reasonable volume, but the outer ring, intercom volume, is somehow turned right down. I dial it up and all is well. I still have no idea how it got turned down in the first place. I haven't adjusted anything in that vicinity. I must have hit it with something. How can I have flown so many airplanes and take so long to sort that out. At least I'm in the middle of the mountains in the early morning and not in terminal airspace in a busy time.

We continue over the mountains then I start descent towards a small airport where I have been asked to land. The operator is concerned about some aspect of the camera software, so asks me not to land yet while he tests the system. I fly big circuits overflying the runway at circuit altitude while he sorts it out. It gives me a chance to verify the winds. There's no other traffic around, so my presence isn't interfering with anyone. Each time around it's "just a few minutes more" but eventually I'm given the okay to land. Because of the elevation, landing appears very fast, but it's at a normal airspeed.

We taxi in, looking for the fuel pump, which turns out to be about ten metres across gravel from a narrow taxiway, partially blocked by a tied-down Cessna. I inch by, not wanting to snag my wingtip on the tiedown, nor to put my spinning propeller over the gravel to the side of the taxiway. I go well past the parked airplane then over to the far side of the taxiway to turn around and pull up behind it, making the closest approach to the pump we can without blocking myself in behind the Cessna.

The hose isn't quite long enough to reach the furthest tank, so we ground handle the airplane a little to wiggle closer until it is. The pump isn't clearly labelled as avgas, and it's not a standard cardlock pump, so we call the telephone number in the CFS for information on fuel purchase. They confirm the fuel type, take the company name, aircraft ident and credit card information and then tell us the codes to turn on the pump. I also call Edmonton Centre to notify them of the photo blocks we will be flying in. Meanwhile the airplane and camera have become covered in fine yellow pollen. There are no obvious flowers around, it's a bit early for flowers this far north. I speculate that it's tree pollen and then remind myself that trees have cones not pollen. They're all conifers around here that I can see. I add some oil, too, and clean the windshield, then we start up and roll out to take pictures. A pretty quick turn: thirty-one minutes from engine off to restart.

We're working at about 8,000', I think, and it's cold outside, but we don't dare turn on the heater, lest the backfiring soil the camera lens, or even worse cause a fire in the aircraft. We just wear our parkas and tough it out. The outside air temperature is -7C but it's warmer than that in the airplane, with our two bodies and the multiple cameras and the thirteen computers computers that control them all generating heat. Still the low temperatures can't be good for all the electrical equipment. They aren't like us humans who have adapted to living at altitudes higher and temperatures lower than this. I'm not personally so adapted, so I am breathing supplemental oxygen and wearing leather gloves and a stretchy toque I pulled out of my flight bag. I have to admit to not being too disappointed when clouds prevent us from flying out the complete mission. We made a big dent in it, though. We land at a larger airport and then jump out and bask in the warmth of the sun while the airplane is fuelled.

I also manage to make contact with the examiner, who says that she needs seven days notice to do a PPC test, because Transport Canada needs opportunity to demand to do the ride themselves. I know that company has been working on this for at least that long, so I get the name of the person at Transport who can waive the seven day notice, and then toss the ball back into my boss' court. The examiner says that if that is worked out, tomorrow around 2 p.m. will be fine, and she gives me, when I request it, the route to plan for the flight test.

Fuelling complete, I go and park. The operator climbs underneath to check the camera and comes out raving about a fuel leak. He says there's fuel all over the belly. The fuelling was competent, no overflow, and even fuel running aft off the flaps should have reached the camera. The operator says it's staining the camera red. Wait, red?.

"The fuel we use is blue." I say. "Red is hydraulic fluid." I climb underneath to see.

"Yeah, I know," he says. "I thought something might make it look red."

I don't really see anything. There's the soot stain from the heater outlet, more of that yellow pollen, but nothing covering the belly. A thin oily stripe does run from the edge of a belly panel towards the camera array. It's consistent with dirty hydraulic fluid. He's cleaned the camera lens already. I don't know what that panel conceals. I don't see why a hydraulic line would be running that far aft, but perhaps a hydraulic leak further forward has pooled inside the fuselage then run out of this access panel. I grab a screwdriver and start loosening the panel. I rely on hydraulics to get the landing gear up and down, so regardless of what it does to the camera, I want to know what's going on here. The operator takes a turn removing screws. It's actually pretty tiring lying on your back twisting your arms overhead. We remove enough screws to peel back the panel and see what's inside. Nothing. There is no pooled fluid, no leaking line, no stains. It seems to be a coincidence that the dirty stripe starts just aft of this panel. Perhaps it was clean enough or enough in the airstream that the fluid was carried over it without staining, then it picked up some grime at the aft edge of the panel.

There are a few drops of red hydraulic fluid visible in the nosewheel hydraulic breather line. It's probably just a few millilitres, normal seepage, maybe from the altitude changes, the purpose of having a breather line in the first place. Text messages and photos go between us and the maintenance unit and they don't think it's anything serious. Except that for the mission of this aircraft is is serious. If it happened on gear retraction after takeoff, it has ruined our day's work, and it means the loss of more than a day, because the weather may not be right for this work tomorrow. We hope it happened on extension before landing.

I ask if he can check the photos now, but the resolution is so great that on the screen in the airplane they may look fine when they are really ruined. We'll have to see later. We haul our gear to the terminal then after more discussion I'm assigned to take off and cycle the gear several times to see if it happens again.

As I strap into the pilot seat I grin to myself. "Hey, first solo." I haven't flown this airplane by myself before. I taxi out "for a local test flight" and cycle the gear up and down, up and down, making sure it's locked in each position before restarting the cycle. I give myself a couple of simulated engine failures while I'm at it, to practice the procedure: gear down, approach power, engine failure, maintain direction, power to hold on the other engine, gear up, simulate feather, emergency checklist complete, give myself the engine back, start over. Instead of doing touch-and-goes I just overfly the runway. And then I land and taxi in. There's a little bit of fluid, but not much. He sends me up to do the same thing again. Cycle, cycle, cycle, cycle, up, down, up, down, up, down, make sure it's down, land. Now there is no seepage. So maybe we're good. We go shopping for airplane cleaning supplies, and call it a day.

I now have about forty minutes to prepare for tomorrow's flight test and get to bed in order to have the required rest for tomorrow's report time. Forty minutes is probably more time than I pend on preflight paperwork for a normal flight, but for a normal flight I use the standard, precalculated weight and balance, use block fuel, round times roughly and only calculate takeoff and climb performance if it's an issue because of high temperatures or marginal runways. And then I generally round up to the next highest weight, temperature and altitude that has its own line, and just verify that it doesn't ask for more runway or lower obstacles than I have. For a flight test, I want the examiner to walk in and see about six pieces of paper with neat, meticulous calculations for each phase of flight. Yeah, that's not happening, considering it takes me at least fifteen minutes to figure out how to rearrange everything on board to accommodate an examiner in the front seat and stay within the weight and balance envelope. This airplane is nose heavy, and not usually flown with no one in the back. My next problem is that I can't find the airport I was told to plan to. The examiner mentioned that the approach was a VFR-only training approach and that she would give me the approach plate, but I need to at least plan fuel to get there. I find an airport with a similar name in the approximate area, and plan to that, eventually saying "screw it, I use block fuel and average winds every day, I'm not losing sleep to do calculations per segment for this artificial situation." I know, I know, a flight test is an artificial situation, but my need for sleep is real. It's already too late for me to get the required eight hours. Maybe I'll have some time to do more paperwork in the morning.

I suddenly remember as I'm drifting off to sleep that a single pilot PPC includes demonstration of competence with the autopilot. I've not mastered it, though. I've never had a chance to practice intercepting and descending on an ILS with this one, because the only airport I've been to that has one has controllers who prefer to vector me all over the place for a close-in base below the glideslope, or a visual diagonal final. I've done a PPC before where the autopilot went below the glideslope and I simply took control and finished it by hand, with no censure from the examiner. If I or the autopilot don't set this up correctly, I'll do the same. There are a few more "better figure out how to do that" moments before I drift off to sleep. It's really embarrassing but there has simply not been opportunity for a proper practice flight.

You guys have made a few guesses as to the nature of the Aviation-Themed Towel of Questionable Taste, which will be the booby prize in the sunglasses contest. No one has come close to guessing how bad it is. It has four different aspects of badness to it. Perhaps I should rename it, the Aviation-Themed Towel of Definitely Poor Taste. The only questions about it is why did someone send it to me, and why is it suddenly so popular?

Emergency Headset

I'm not sure if I mentioned that I have had some communications difficulties with ATC lately, missing calls, or having to have parts of calls repeated. I thought it was distraction, working with a new task or missing an unfamiliar callsign, but taxiing in at Vancouver I realized that moving the cord made a difference to whether or not I could transmit. What a time for my headset to die. I could get it repaired, but that would involve express shipping it to the manufacturer in Portland, Oregon and back. And I'd have no headset in the meantime.

Or no good headset. There are a couple of spare headsets in the airplane, but wow, sorry, if you've used a good noise cancelling headset for over ten years, passive no longer cuts it. I wonder how people managed with those things. I have to do a PPC ride and work in the flight levels. I can't not have it work.I was an early adopter of noise cancelling technology, reasoning that I only had the one set of ears. People laughed at my bulky earcups, but then they tried it and they bought them too.

I suppose there may be some readers unfamiliar with noise cancelling. It's also called active noise reduction (ANR), active noise cancellation, and probably some other things. Each manufacturer has its own jargon. It works by having a little microphone in each ear cup, sampling the sound that's getting in there, and then generating a noise that is the exact opposite of that noise, cancelling out the first noise. It works because sound is not a thing with form, but only exists as squished and stretched out parts in the air, so you play a sound that squishes and stretches the air in the exact opposite way, and the result is much less sound. There is no time travel technology associated, so it can't predict the future, therefore takes a moment to cut in, and works best on steady sounds, like engines, and therefore actually allows you to hear irregular sounds, like something going "clunk" or someone speaking, even better. The sound dampening provided by merely having something clamped over your ears is called passive protection, and the total hearing protection offered by a headset is the combination of active and passive. Less expensive headsets offer only passive noise reduction.

The noise cancellation still works on mine, but the wiring inside the cord has probably broken. Also the headband doesn't fit as securely and the earseals always fall off overnight. After five thousand hours of service, the headset owes me nothing. I was planning to replace it soon, but had hoped to have leisure to compare and test different headsets.

Fortunately there is a headset dealer at the Vancouver airport, less than a kilometre from where the airplane is parked. I bring my old one and then get straight to the point. "Hi, this is broken. I need a comfortable, high quality ANR headset that fits small. What do you have in stock?" The clerk asks me what my budget is. I know how much a good ANR headset costs, "A thousand dollars," I say, in a way that is intended to convey that I'll pay more if that's what it costs. (Yeah, none of the tools of my trade come cheap). I know that I can't buy new ears, that an airspace violation could cost me that much in fines, and a botched clearance could kill me. I can see the display case of headsets, but instead of going over to it and showing me what's available, he disappears to the back of the store without another word. Weird.

I look at headsets for a while. There are some David Clarks, but while they are the unrivaled leader in durability and movie appearances, they were late on the ANR bandwagon. I remember a guy who sold a homebrew ANR conversion for DCs, and it was better than what the company itself came out with. There's a Telex, but not the ANR model. I think the only ANR headset there is a Bose. Another salesman comes out to help me. I think the first guy figured he didn't know enough about the headsets to deal with me and went to get the expert. The Bose is comfortable, fits me, has good noise cancelling. You can't really tell if a headset is going to work for you until you've flown with it, but it's significant;y lighter than the old headset, and has an excellent reputation and warrantee, including a thirty-day satisfaction return policy. Ordinarily I'd buy a headset letting the seller know I was taking it for a test flight, but when I take off from here I don't know where I will land. I'll take this one based on reputation: I'm sure it will be good enough, and given a chance to test the newest model from other manufacturers, I can mail it back if they are significantly better for me.

I tell him I'll take one. But as I haven't pre-ordered, he doesn't have any in stock. And he's not getting more until September. Bose has a US military supply contract and therefore aren't super concerned about getting their headsets in small retailers' hands.

"What about this one?" I ask, of the display model. He quickly decides that it's worth selling it to me, and puts it in its box. Comes to over $1200 with the taxes. It's a Bose A20 with Bluetooth connectivity, an extra option I wasn't planning on spending $100 on, but that's what it has. Bluetooth is kind of a joke for me as my cellphone is so old it doesn't even have a jack for a handsfree headset, and I still have two perfectly functional non-Bluetooth MP3 players. Come to think of it, I bought the cellphone in a similar, "NEED PHONE NOW!" panic. Is this the way I live my life? I guess some people keep a constant awareness of products they might need, knowing which one they want most at any moment so that when their current one dies they can replace it with confidence. Actually, don't answer that. The normal way is to replace your stuff before it wears out, with newer and better. I like my stuff and hate discarding functional things. I'm going to see if I can get my camera repaired, for example.

So I stash the old headset in the back of the airplane and set up the new one. Comfy!

Also I've noticed that at least two numbers (37 and 107) have two takers each in the sunglasses contest. You don't have to read all the submissions, but to increase your chances, double-check your choice by using the "find" command on the comment list to see if it's already been picked. I'll leave the contest open until we run out of numbers or the first appropriate (not raining at destination) flight after I get a working camera, whichever comes first.

Digital Fuel Management

I've spent my career flying airplanes with instrument panels that haven't been substantially updated since the aircraft were designed in the 1950s or 1960s. Anything electronic is a newfangled after-market device not in the original aircraft specifications. Of course I haven't had any trouble using the newfangled stuff with which my various employers retrofit their aircraft. A new installation always comes with a manual, and you can usually find manufacturers' information online, too. I've enjoyed electronic tachs, EGTs, navcoms, and even a Sandel-OMFG-it's-everything-in-one-instrument, please don't let me push the button that makes it turn into a microwave oven just as I'm intercepting the glideslope (okay I had a little trouble with that one, but not as much trouble as the poor guy who owned it and had hired me to help him pass his IFR renewal with it). There's an instrument I've seen a few times, in airplanes I've flown once, or flown for short flights, and never bothered to learn how to use, but now there's one installed in an airplane I will fly for work, so I'd better learn to use it properly.

It's a Shadin Digital Fuel Management System, a fuel flow meter that, given information on how much fuel you started the flight with, should give excellent information on how much is left. See, normally you spend the flight comparing the known time and power setting with the fuel gauges and hoping everything you are looking at is as accurate as the agreement among them. You could have some weird fuel leak on the same day as you had a fuel gauge over-reading error and had your watch stop. It's not likely, but you could. That's the sort of not likely but it could happen scenario that pilots are paid to think about every day. The Shadin is another tool for tracking fuel consumption, and it's supposed to be extremely accurate, much better than fuel gauges, and it's digital, with readouts like fuel endurance so I don't have to peer at parallax, estimate needle widths, or even do any math.

Here's a post based on the manual for the Digiflo model, with notes on the slightly different Digidata model, which I think is on another member of the fleet. I start by verifying the fuel quantity the only way I really can, by visually confirming how much fuel is in the tanks. So this is on the ground, immediately after fuelling. Then I enter fuel on board into the device. It doesn't have a keyboard. In fact it's one of those nifty little pieces of electronics designed to fit in the dashboard hole made for a traditional round instrument, about the size of the bottom of a standard soup can. The picture below isn't quite the right product. Mine has three display windows, three push buttons, one three position toggle switch and a four position rotary knob. The top window normally displays whatever is selected by the rotary knob: NM/GAL, GAL. TO DESTINATION, GAL RESERVE or ENDURANCE HRS:MIN, and is flanked by the GAL REM. and GAL USED push buttons, which while held change the display appropriately. The bottom two windows display the fuel flow per engine.

The Digidata has the "ENTER/TEST" button in the left, a "REM/USED" toggle in the middle, a "FULL/ADD" toggle on the right, a rotary knob, and two display windows, one for the fuel flow and one for whatever is selected on the rotary knob. On that model, to display the fuel flow per engine you squeeze the REM/USED and FULL/ADD toggles together. I'm not sure if this is the right picture.

There are three options for entering fuel on board on the Digiflow. One is if I have filled all the tanks, in which case I move the FULL/ADD toggle to the FULL position and hold it there while pressing the ENTER/TEST button. I can then press the REM button to verify that it reads the full amount as fuel remaining. That's already set for the airplane. If I'm not filling the tanks I have to specify how much fuel I have added, by holding the REM button and pressing the TEST/ENTER button until it reaches the right level. For some reason there's a second way to do this, by holding the FUEL/ADD toggle in the ADD position and pressing the REM button to reach the right number. If I overshoot, I can press and hold the USED button and then press and hold the TEST/ENTER button until the right value is shown.

On the Digidata model I hold the REM/USED toggle in the REM position and hold down the ENTER/TEST button until the window displays the fuelled quantity. If I overshoot, I can remove some by holding the REM/USED toggle in the USED position and pressing the ENTER/TEST button to reduce the displayed quantity.

Once the amount is entered, I press the “ENTER/TEST” button and it should display in succession:

• 1. GOOd to verify that the display is OK
• 2. the K-factor (a calibration value for the fuel flow transducers)
• 3. the maximum usable fuel for the aircraft
• 4. software & revision version #
• 5. distance to a waypoint or destination

It achieves the fifth calculation because it can talk to--and I love this old meets new specification--the panel mount GPS or the LORAN C. Someone must have really loved his trusty LORAN C.

Fuel flow transducers are like little turbines spinning in the fuel lines, but if you thought "hmm, the speed of the turbine might not always be directly proportional to the fuel flow rate" then you would be right. If you not only did not pause to wonder that, but aren't sure whether it's worth pausing to wonder what it means, then you should pause instead to give thanks that there are engineers in the world, because it's important. The math to take into account the effect of 'viscous', 'transient' and 'turbulent' flows is probably fascinating. Maybe instead of stealing linguistics, I should have been stealing fluid dynamics. Those classes are probably harder to figure out when you drop in three quarters of the way through the semester, though. The manufacturer also assures us that if a transducer somehow gets stuck and stops spinning, it will not impede fuel flow to the engine.

The readout updates very rapidly and is easier to see than the EGT. I can see that once I get some familiarity with the airplane I will be setting mixtures by fuel flow, and then confirming that the EGT is within limits, rather than peering at the tiny digital or usually inaccurate analog EGT gauges. Also the display flashes if the fuel remaining is insufficient to reach the selected destination with 45 minutes reserve fuel.

En français:
un carburant - fuel
l'essence aviation (f) - aviation gasoline
le débit carburant - fuel flow
à court de carburant - low on fuel
avoir une panne d’essence - run out of fuel

Je veux apprendre à utiliser cet indicateur du débit carburant pour je n'ai jamais avoir une panne d'essence.

Hats Not Cats

The electrical system in those airplanes I once flew (someone suggest a nickname for it, eh?) underwent a few changes from version to version. I remember that the first one was the first airplane I flew equipped with generators, not alternators, the functional difference being that a generator will not charge the battery at low rpm, but it can be used to charge an absolutely flat battery (assuming the battery has the capability of holding a charge) while an alternator can charge at low rpm but needs there to be a bit of juice left in the battery to excite the field so it can work. You know what? I've recited that a hundred times, and can continue, but in order to ensure I really know what it means, I shall try to build an airplane electrical system from stone knives and bearskins. Let this be my apology for weeks of soul-searching, arts classes and lolcats.

Electricity is essentially the displacement of charges. Rub dissimilar materials and they may become oppositely charged and cling together. The differential may discharge in the form of a spark. It's as if every neutrally charged molecules were wearing a hat, but when you rub them together the hats all fly up in the air and the molecules with a greater millinery affinity grab more than their share. So when the dust settles you have the molecules of one substance wearing extra hats and the molecules of the other being hatless. This isn't a stable situation, and given the chance to correct it, the ones with extra hats will give up their headgear and the bareheaded ones will grab up stray hats. By this model, electric current would compare to a string of people with hats, all snatching the hat off the person to their left and putting it on, over and over again around in a circle.

A flow of electric current induces a magnetic field around a wire, and likewise movement of a wire through a magnetic field induces electric current in a wire. It's like passing hats creates a breeze, but a breeze itself lifts up people's hats. Can't have one without the other. The hat passing is driven by the power source, such as a battery. In a motor the magnetic field is used to create rotation--doing work with the breeze from the hats. In a generator, a breeze is used to make the hats move.

Rather than using just one wire for this effect, wire is wrapped in layers around a core, giving more electric-magnetic interaction in a more compact area, so making the whole thing neater and more efficient, like arranging your hat-wearing people on tiered benches so the same breeze can lift more hats or to increase the breeze in a small area. I think I'll stop talking about hats now, but if you like hats, then from here on read "movement of hats" for electric current and "breeze" for magnetic field.

In a generator an electromagnet creates a magnetic field around an armature (a spinny thing) wrapped with wire. The spinning movement induces an electric current along the wire. The force to spin the armature comes from the airplane's internal combustion engine, the thing that's driving the propeller. That's right, they use electricity to make a magnet, then they use the magnet to make more electricity. With this much information it seems as though the generator can't produce power unless it already has power, because otherwise what would power the electromagnet, but the trick is that having acted as the core of an electromagnet, the iron contains remanent magnetism. It's not a lot, just enough to induce a small current in the spinning armature, which is enough to increase the magnetic field so that it can generate a greater electric current and so on until it reaches a steady state. You can get more current by turning the engine faster, but you can't get more at low engine speeds. In fact you might not get enough at low engine speed, the weakness mentioned in the first paragraph of this entry. I've just learned from this site (which describes alternators and generators well, albeit without hats) that when you first connect a generator you need to polarize it before starting the engine. That also implies that if I disconnected a generator for some reason and then reconnected it, I could damage something by starting up without polarizing it. Another reason to keep screwdrivers out of the hands of your pilots.

The direction of the electrical current induced in a wire depends on the direction of its movement relative to the direction of the magnetic field. There are wacky things you can do with your fingers to figure out which way that is, but we're not reliving our grade eleven physics classes here, so you can put your fingers down. The point is, if you're spinning the armature, you can see that you'll get a relatively strong current as the wire cuts across the magnetic field, a current weakening to nothing as it moves to be parallel to the field, and then a strengthening current in the opposite direction. That is, it will produce an alternating current. An old airplane like this wants one-way direct current, so to prevent it from flipping back and forth, it's connected to the rest of the electrical system via a split ring device called a commutator, which reverses the connection every half turn. The end result of having both the connection reversed and the current reversed is steady current.

Generators are old-fashioned and more troublesome for maintenance, so the manufacturer allows you to replace the ones in this airplane with alternators. An alternator works on the same principle as the generator except that in the alternator, the wire windings in which the current will be induced are on the outside, and hold still, while the electromagnet that creates the magnetic field spins on the inside, connected to electrical power via a slip ring, which is simpler than a commutator. AC is converted to DC with a diode. A voltage regulator increases the current to electromagnet so that the alternator produces sufficient power for the aircraft electrical services, even at low rpm. That requires the alternator to draw power from the battery in order to get going, but it's worth it, because the alternator can then charge the battery immediately after start. A generator may be still discharging during low power taxi.

The POH copy I have here claims the aircraft has a 12V 33 ampere-hour battery and two 12V 50 A generators, one on each engine, but who knows if the airplane it belonged to still has generators. If it does, each generator has a voltage regulator and a there is a paralleling circuit to divide the load between the generators. If only one engine is running, a reverse current relay cuts its generator out of the circuit. Also, typically an alternator produces a higher voltage than the battery, so that it can charge the battery. I'm winding down now, so I'll see if I can write about voltage regulators, RCRs and paralleling circuits later.

Hyperphysics is an excellent site for this kind of thing, but I'm not too impressed with their 3D field diagrams.

Engine Startrekinsey Sequence

I'm not sure if this is a cohesive description of the engine start sequence or an unpublished chapter of Joyce's Ulysses in which we follow Aviatrix's stream of consciousness as she slides into aircraft manual-induced, chocolate-deprived madness. Either way, come for the engines, stay for the Star Trek references and sexual innuendo.

When I start my car, I put my foot on the brake, the key in the ignition, turn and hold the key until the engine sounds just right, then release the key and the engine continues. That's a little bit complex. You have to get a feel for when to release the key. When I first learned to drive there was another complication, in that I had to put my foot on the gas as well and give it just enough gas to start. But many of you start old manual transmission cars every day without even thinking about the process. And some of you start up an electric car by, I understand, pushing a button. I think they just push a button to start the starship Enterprise too, so this is clearly the way of the future.

Push button airplanes exist, and starting mine does begin with pressing a button, but it's a little more complicated than that, and I have to know and understand the whole sequence, including the stuff that does happen automatically. I'm sure I'll be quizzed on this all during the test, and if I'm going to feel helpless someday when I can't get the engine started, I'd best know exactly what is failing to happen.

Before Start

I need to be sure that the inlet and exhaust are free of debris, that the first stage compressor has no visible damage, that the P2T2 probe is clear, the propeller is on the blade angle locks, and that it moves freely. I should check the oil, make sure the speed levers and power levers move freely and are set in the low and just ahead of ground idle positions, respectively. If I'm using a GPU I should make sure it's supplying 24 V and 1000 A, and if I'm using batteries I should check that they have a good charge.

0 - 10% RPM

After the prestart checks are complete, I press and hold the start button. As a result:

• the #1 start control relay closes
• the starter relay closes
• the oil vent valve opens
• the anti-ice lockout valve closes
• the starter engages to rotate the engine

And let's see what that all means.

The #1 start control relay "is used to control the starter relay and the oil vent valve during ground starts, and the propeller unfeather pump during air starts." It "also opens the voltage regulator 'B' to starter-generator 'A' lead to prevent field feedback during starts." The first part I get: The #1 start control relay is the electrical string you pull on to get the next two things on the list to happen. If the second part of the description mentioned some kind of particle or anti-matter, I would swear that was from one of the episodes of Star Trek: The Next Generation where Wesley saved the ship again. I can surmise that for some reason the starter-generator has an 'A' lead, that the voltage regulator has a 'B' lead, and that these two are normally connected, but that that connection can lead to undesirable feedback during starts. I can further surmise that the voltage regulator is there to regulate generator output, but seeing as the generator isn't put on line until after it has finished being a starter, that there's no need for it to be connected during start.

The starter relay "energizes the starter generator, during ground starts only." That makes sense, because during air starts the starter is not needed: rotation of the engine from the propeller is sufficient.

The oil vent valve is a clever little kludge to prevent the starter having to work against cold sluggish oil pressure as it rotates the engine. It opens up the oil system to allow it to ingest air during ground starts.

The fuel anti-ice lockout valve closes off the line through which the fuel system cycles cold fuel to a heat exchanger with the oil to prevent ice crystals forming in the fuel. At start the oil isn't warm anyway, so the valve is closed to keep the fuel pressure high.

So that's two things that happen when the start button is pressed, two more that happen because of one of those (or three if we count the A-B lead thing) and one one that happens because of the second wave. And that's all before anything even catches on fire.

10 - 55% RPM

When engine RPM reaches 10% the fire is supposed to start. Specifically:

• the 10% speed switch closes
• the #2 start control relay closes
• the series/parallel relay connects the batteries in series, if selected
• the SPR valve is energized
• the fuel solenoid valve opens
• the 'primaries only' fuel solenoid opens
• ignition turns on

And I know what most of that means.

The speed switches contain reverse tachyon tribarium warp core interfaces a DC regulating system, a signal conditioning amplifier, timing pulse generators and voltage discriminating circuits (it only allows straight voltages to go through, and the ones with suntans don't get to use the good wires). The speed switches contain STUFF, okay, including three relays. The 10% relay (which the voltage discriminating circuits probably think is an overestimate, or maybe a lifestyle choice) is normally open, the 55% relay is normally closed and the 90% relay is normally open. They receive electrical signals from the "tach gen" which for the purpose of my own amusement I will imagine stands for tachyon generator. Each relay changes its respective state when engine rotation reaches the corresponding speed. The 90% one isn't important to engine starting, but I didn't want to leave it out, as it's probably already getting enough hassle from the voltage discriminating circuits. Best I can tell from the ten pages of starter circuit diagrams, when the 10% speed switch closes, it energizes the #2 start control relay, and the #2 start control relay does the four other things on the list: ignition on, batteries to series, SPR energized and fuel solenoid on.

Hey who thinks I should be allowed chocolate now?

The series-parallel switch sounds like something Scotty would do at the last minute to keep the Enterprise from falling into a black hole.

"It's no use Captain. We haven't got enough juice to get the warp engines online."

"You've got to get them online Scotty, or we're all dead!"

"Well I suppose if I cross connected the dilithium crystals from the other nacelle, it could possibly give enough of a boost to get the warp core online. It's never been done before, laddie."

And then he does it, and it works and the he publishes a paper on the subject, and the manufacturer comes out with a bulletin saying never to do it because it voids the warrantee. It's just like that. In fact it's hard to believe that some desperate pilot didn't invent it while stranded on a reserve somewhere, except that this isn't a bush plane. The manufacturer has set it up so you can flick a switch and the batteries, usually connected in parallel, one to each starter-generator, automatically go into series when the power is needed most. My company, however, says that the power is not needed most at 10% but rather at about 18-28% where there are bad vibrations (seriously, that's the reason), so what I'm supposed to do is start the engine with the series-parallel switch in parallel, but if the engine rpm is at or above 18% and not increasing steadily by 1% per second through 25%, I should flick the switch into series then. I was so impressed by this in groundschool I immediately asked why I wouldn't do it every time. It's because it's very hard on the batteries and if you drain both of them together, you only have one shot, so you have to hit it with your best shot. Also if you do it at night you need to have a flashlight handy, because it will dim the lights and you won;t be able to see the engine instruments.

The SPR valve is another thing they didn't get quite right, according to company procedures. It sounds all cool and modern with the TLA and all, and it stands for Start Pressure Regulator which brings to mind the idea that it might be some sort of computer. Nope. It's the primer. Yeah, the primer. I have to prime this puppy. Primer is available between ten and fifty-five percent rpm, but I should prime it between zero and ten percent, then not prime it between ten and twenty-five, then go back to priming until 55% when the 55% speed switch opens and de-energizes it. The SPR bypasses the fuel control unit and fuel flow transmitter, going straight to the primary fuel nozzles.

The fuel solenoid valve is the thing that lets the fuel into the engine so the igniters have something to ignite. I'm sure that makes them very happy. You can close these valves mechanically with an emergency stop control, but then you can't open them again. Ever. Okay probably not ever. I assume maintenance can fix you up again. The primaries only solenoid allows fuel through only the primary starter nozzles, not the full manifold.

The igniters are not something that I have a lot of information on, but the ignition exciters supply "a nominal high voltage of 18,000' volts to the igniters" so the exciters seem to be serving as fluffers to the igniters. The igniters are some kind of high tech spark plug that lights the fuel. I know they are different than glow plugs, because I flew an airplane once on which some models had glow plugs and some models had igniters and this was apparently different enough that I was supposed to care. (Can you tell I didn't?) I pretended to at the time, and phasers on kill, I swear I will pretend to care about this, too. The igniters light my fire. Can't start a fire without a spark. What is wrong with me? I almost never quote song lyrics. Because I don't know any.

A light comes on when the igniters are working, and the EGT should rise, indicating that something is actually on fire in there, and that the hot exhaust is coming out the right end. When it happens, the pilot can release the start button. If it doesn't happen within ten seconds of reaching 10% rpm, or before reaching 20% rpm, the pilot should shut down the engine. She does this by pressing the stop button, pulling the stop and feather control and then continuing to motor the engine for ten seconds with the starter test switch.

55% RPM

When the 55% switch (which the book calls a 50% switch, but the book is for an older model of engine, so I have to assume that changed) opens, everything that the #1 and #2 start control relays did gets undone, except for the opening of the fuel solenoid:

• the starter relay closes
• the starter turns off
• the anti-ice lockout valve opens
• the oil vent valve closes
• the series/parallel relay goes back to parallel, if it was used
• the ignition turns off
• SPR becomes unavailable
• primaries only fuel solenoid closes

Whew, that feels good. It was actually worth it. It took too long, though. I spent a couple of hours on that, between course notes, two manuals and the engine supplement. And stalking around hoping chocolate would spontaneously appear.

Is there some kind of vitamin, found only in chocolate, from which deprivation makes it difficult to study without degenerating into lame Star Trek references, old song lyrics and crude jokes?

I'm also getting antsy, waiting for my training to be scheduled. I have a job offer already, but until I actually go online as a pilot, I don't really have a job. They scheduled the first two while I was there, and I know the second one had a PPC ride today. But it could have been delayed by aircraft or training pilot availability. That happens. Or they decided they hated me and are just going to ignore me. It's not paranoia when they really are out to get you. I e-mailed the chief pilot with a question about where I should send my paperwork, kind of the way I ask ATC for an altimeter setting when I haven't talked to them in a while.

The Short Bus

When I was working on my commercial licence I met a guy who flew the Screaming Whippet and one of the things I remember him saying about the aircraft was that it had a very complicated electrical system. I was looking forward to meeting this beast, but we were warned in ground school not to pre-read about it in the manual, because there were many options and modifications and that we'd get confused if we did. So it was unveiled on I believe the morning of the second day of class.

It's not so bad. Yeah, it has DC power and three different flavours of AC power, but I can understand the circuitry. There are two 24V lead acid batteries, two 28V starter-generators, and capacity to accept ground power (max 1000A), which can power electrical systems and/or charge the batteries. I've done this enough time that those are pretty standard numbers. The batteries each have their own relay connecting them to the system, then an additional relay connecting the combination, plus the GPU if connected to the battery bus. The battery bus is power distribution central on this airplane. It's located in a junction box behind the left pilot seat, and everything connects to it. Each starter-generator connects to it through a generator relay and a 325A current limiter. The DC battery bus provides power to the left and right essential buses, through 225A current limiters and also to a non-essential bus, through a 150A circuit breaker. The current limiters and circuit breaker are all located in the junction box. Each of those three DC buses described also has a bus tie switch. They are on the circuit breaker panels, under the windows on the left and right sides of the cockpit.

Most of the services are quite predictable, with the left side of the airplane being on the left bus and the right side on the right bus. There are also nine or ten (the tenth is optional) transferable items that can be switched from the left to the right DC bus in the event of a left DC bus failure. They are the turn and bank indicator, the fuel crossflow valve, the valves controlling wing and tail deicing, the windshield heat, the valve controlling left inlet anti-ice, the valve controlling right inlet anti-ice, the flap and gear position indicators, the valves controlling landing gear operation, the solenoid that applies vaccum to open the dump valve and (optionally) the pilot-side DC cockpit instruments. Flaps, nosewheel steering and all exterior lights, including landing lights are on the non-essential bus.

Each essential DC bus has one inverter, and each inverter is connected to 26V AC bus and a 115V AC bus, so four AC buses in total. The L and R 115V buses are connected together through a circuit breaker, as are the two 26V buses, so that with one inverter online, all four buses are powered. Only one inverter can be online at a time. The fuel pressure, oil pressure and some cockpit instruments are on the 26V AC bus. The fuel quantity gauge takes 115V AC. The cockpit edge lighting is powered from the 115V bus, but stepped down to 6V. Other instruments may be on one or the other depending on the airplane, you need to check the CB panels to see.

My brain is full. Remember this two weeks worth of system spam you've been receiving was a three day blitz for me. And I have SOPs and limitations to learn on top of this. I think I'll go jump on the treadmill for an hour. There's too much snow outside to go running, but it's too slushy to go skiing.

Today is Pi Day. You should celebrate by eating pie. You may heat it in an electric, gas or wood-burning, dung-burning or solar powered oven. Or another sort if you have one I didn't think of.

P.S. I got on the scale after jumping off the treadmill. Target weight minus five hundred grams. Booyah! No sugar, no alcohol and get some damned exercise. It works, people. Girl's got legs and she knows how to use 'em. Now to keep it off.

Anti-Ice Without Electrical Heating

Yesterday's post was mostly about electrical heating elements that prevent ice from accreting on various parts of the airframe. Today is about anti-icing measures that do not involve electrical heating, except in as much as the flow of electricity always causes some heating.

The leading edge of the wing and tail are covered in what is essentially a network of bicycle wheel inner tubes stretched out straight, covered in a neoprene sheet and connected to a nozzle. At the pilot's command, an electrically operated regulated 18 p.s.i. bleed air inflates the tubes, called boots and pops off the ice. Whether the pilot commands it or not, at all times that the boots are not being inflated, suction pulls the boots back snugly against the wing. The suction also comes from the 18 p.s.i. regulated bleed air, through the same distributor as the positive pressure. I'll explain how it can both suck and blow later. This system is yet another controlled by a three position switch. The OFF position leaves the solenoids controlling the distributor de-energized, and the wing boots connected to vacuum and sucked against the wing and tail. The AUTO position opens the solenoid allowing 18 p.s.i. regulated bleed air into the wing boots, inflating them for six seconds. Then that pressure is dumped overboard and the wing boots gets sucked back against the wing while the tail boots get inflates for four seconds. After that the system rests for 170 seconds and starts over. The third position is MANUAL and all the boots will remain inflated for as long as the pilot holds the switch in that position. Electrical control of the solenoid can be assigned to either the left or right essential bus.

Inside the engine inlet is a probe called the P2T2 probe (or the R2D2 probe, depending on who is talking). Its job ought to be transmitting pressure and temperature readings for that station to the engine computer, but considering that it is kept ice free with P3 bleed air, it seems that it wouldn't be an accurate indicator of the temperature and pressure there. What am I missing? And does its output have to be translated by a C3PO probe before it can be used? This web page has condescending British people telling someone else who dared ask that anyone at the ATPL level who has to ask questions about a P2T2 probe is lazy and stupider than a toenail. Maybe so, but I know how it's anti-iced. Mostly I know. I'm not sure if it is automatically supplied with bleed air at all times or whether that's part of the inlet anti-ice.

I like the way the anti-ice for the oil cooler works. It simply runs the line taking hot oil from the engine around the lip of the air intake before routing it to the oil cooler. No electricity required.

The fuel anti-icing (i.e. to prevent ice crystals from forming in the fuel thus blocking the filters or lines) also uses heat from the oil, but not quite so simply. As the high-pressure engine fuel pumps draws fuel through the filter towards the fuel control unit, some fuel is routed off to the side, through a heat exchanger, heated with scavenged hot oil and then metered through a temperature-controlled anti-icing valve and sent right back to where it started before the filter. I don't know the exact mechanism; it probably involves a bimetallic controller, but the colder the fuel, the wider the anti-icing valve opens and the more fuel has to take the scenic route through the oil-fuel heater. An additional valve in the system, just before the heater, closes when the engine speed is below about 50 or 55% rpm, to prevent any fuel from being diverted during engine start, the only time such low speeds should occur.

Back to the very low tech, the manufacturer claims that the static ports and fuel vents on the airplane are anti-ice. They have no heating, it's just that the fuel vents are concave and out of the airflow, so there is nothing for ice to build up on, and the static ports are also very flat and at the rear of the aircraft. Just in case they were to ice up, there is an alternate static source located in the unpressurized forward baggage compartment.

There are two more anti-icing systems on the standard aircraft, but they are both irrelevant to this fleet, one because the system it belongs to has been removed, and the other because it was an option not installed.

Also, can someone please tell the person who writes the scripts for my bank's drones to read at me while I try to set up automatic payment on my new credit card that (a) a new credit card is not an occasion for "congratulations," and (b) "I want to inform you some points" is not English.

And in current news, when a huge tragedy strikes, and it's too much to take in all at once, people focus on the corners of it that are most relevant to them. I woke up to e-mail chatter about international flight schedules, plus this video of the tsunami associated with Japan's earthquake hitting an airport. Even people with no international connections have something in Japan they can relate to. I laughed to see the internet hasten to assure us that Maru the Cat and his owner are fine. But what is a mass tragedy if not thousands of individual tragedies, and, thanks to stringent building standards combined with preparation and training, millions of people who can say, "I'm okay, and so is my cat."

Heating Elements: Making Coffee, Shedding Ice

You know you've been reading too many airplane manuals when you can't turn on the coffee maker without thinking, "horizontally-mounted unlabelled three-position rocker switch spring loaded to the centre position, with an adjacent amber indicator light illuminating when the heat cycle has been activated by momentary left pressure on the rocker switch," and then wondering about the circuitry of the heating cycle and of the timer that deactivates it if you walk away and leave it on.

The Screaming Whippet has electrical heating elements, but not for making coffee. Both left and right pitot tubes are electrically heated, from their respective DC power buses, and there is a switchable loadmeter in the cockpit for checking their operation. The pitot heats are operated by a vertically mounted three-position rocker switch, but the upper, pitot heat position is rarely used, in favour of the lower position which heats both the stall indication vane and the pitot tubes. The windshields are also electrically heated, through the largest (60A & 50A) circuit breakers on the airplane, via the left and right essential DC buses. With windshield heat selected to LOW, the panes in front of both the pilot and the copilot are heated together, with single thermostat, such that if the sun is to one side or the other of the airplane and one windshield reaches the 90-100 degree Fahrenheit temperature, it will cycle off despite the other one not being hot yet. With the windshield heat switch set to HIGH the windshields cycle separately, with twice as much power as before going to the captain's side. I'll have to check, but I think the FO may not get any more heat on HIGH.

Let's see, what else is electrically heated? The propellers are. On the leading edge of each blade there is a little grid of wires, kind of like the ones on your car's rear window defogger, except that these are under a rubber cover. There is an inner and outer element, although it looks like just one. And there's a really really long skinny cord so that it can wrap round and round and round the propeller without coming unplugged. No, I'm kidding about that. It's tricky to have an electrical cord on a propeller. There is instead a slip ring assembly with a brush block so that electrical contact can be made without a hardwired connection as the propeller goes round and round about two thousand times a minute. Each propeller heating element draws power through a 25A CB on its same-side 28V essential DC bus. The system operates on a timer, switching on all inner and then all outer elements on either propeller, and it's not crystal clear from the description whether that means a four stage cycle with only one propeller at a time or a two stage cycle with the inner for both props together and then the outer for both props. There's an ammeter that shows the current being supplied to the prop anti-ice; the manual says it should be about 14-18 A per propeller, which suggests to me that they are both on at once. You can switch the ammeter back and forth to show the left propeller or right propeller draw. But then it also says there is a separate timer for each propeller, so I'm not quite sure. When you turn it on, heating starts wherever it left off last, not at any predetermined position.

Propeller heat is on the same switch as nacelle inlet anti-ice, but in the case of a failure of one essential DC bus, only the inlet anti-ice can be switched to the other. Power can not be supplied to the propeller elements on the side with the failure.

I didn't mentioned the inlet anti-ice before the above paragraph, because it doesn't include an electrically heated element, but seeing as it's on the same switch as the propeller heat, I'll put it here. Inlet anti-ice refers to the engine inlet, the part at the front of the engine where air comes in to make the engine work. It is important that this area not become clogged with snow or ice. Instead of using electricity to heat this area, really hot air is blasted into it. This works well and being that the engine inlet is really close to the engine, it has a ready supply of really hot air. It's not exhaust: that's too hot and is at the other end of the engine. (A number of readers will now being going clue! because believe it or not "the exhaust comes out the back of the engine" is not a universal truth with airplanes). This is bleed air that has been heated by compression in the front part of the engine.

I will now quote some facts about the engine intake air from the training manual. Keep in mind this is a training manual, a collection of useful information felt essential for new pilots to learn before flying this airplane. It is not a maintenance and repair manual or a set of blueprints. The first paragraph of the description tells me that bleed air is obtained for this purpose from two different ports, one being "the main anti-icing bleed port" and the other the "cabin pressurization bleed port." It doesn't tell me the relative location of these ports in the engine or how the two sources are different, so I'm not sure why I should care, but in the second paragraph they want to be sure that I know that "the flow from the main anti-icing bleed port runs through an anti-ice valve to a tee: the tee has an orifice of 0.234 inch diameter." Sadly, I will now remember this, and possibly I will also remember that "the line supplying the left-hand side of the distribution duct has a 0.204 inch diameter orifice." Why? Why am I burdened with this information? I understand that the brain does not actually fill up with facts, so that having this one thrust upon me does not decrease the likelihood of my remembering the essential items to complete in case of an engine fire (stop it, close the firewall fuel shutoff, close the hydraulic shutoff, discharge the fire bottle), but still, it's distracting.

Manual-provided information of which I do approve includes more about the switches and annunciator lights. The switches (one for each side) each have three positions: ON, OFF and TEST. In the ON position, the electrically operated valve that allows bleed air to flow through those very specifically sized orifices to do its deicing job is commanded to open, and if the circuitry can verify that the valve did indeed open, the appropriate INTAKE HEAT ON annunciator is illuminated. In the OFF position, the valve should close. Assigning bleed air to this task comes at a cost: a drop in engine torque and a rise in exhaust gas temperature. That is to be expected because the compressed air would otherwise have been used to cool and contain the combustion area and to drive the power turbines. Because of the performance hit we would take if the valves did not motor to the off position when so commanded, electrical power to those valves can be taken from either essential DC bus. There is also a means of verifying that they actually did close: when the switch is depressed to the test position, if the circuitry can verify that the valve is closed, the INTAKE HEAT ON annunciator illuminates. That's kind of backwards, but pretty clever, really. And far more interesting than the diameter of the bleed air orifices. Hey, I just figured out why they included the diameter of the bleed air orifices in the manual. It's to ensure that the test function of the inlet anti-icing valves could be far more interesting than something.

There are more anti-icing measures on the Screaming Whippet, but there are several more anti-icing systems on the airplane, most of which have an electrical component, but I'll put them in a different post, because this one is mainly about heating elements.

Also I've been reading over the details of the job offer. I think this is a real job. Like I get paid extra for working on statutory holidays. Just to keep the Canadian content up, I'll tell you what they are: New Year’s Day, Good Friday, Victoria Day, Canada Day, Labour Day, Thanksgiving Day, Remembrance Day, Christmas Day, and Boxing Day. It seems that for International Ice Cream for Breakfast Day (first Saturday in February) I'll be on my own.

Juice Holding and Delivery

The airplane has a fairly simple fuel system. At least, I've seen worse. The fuel sits right in the wings, no fancy tanks, no bladders, just fuel everywhere, with the ribs acting as anti-slosh baffles and the five percent dihedral directing the fuel inboard. Yup, it leaks. There are flapper valves on three of the ribs to allow fuel to flow inboard but not outboard. Inboard of the engine nacelle, at the wing root, the inside of the wing is divided along the the chord into three sections: a forward collector tank, a centre hopper tank and an aft collector tank. Two submersible boost pumps are in the fuel in the hopper tank and the tanks are connected to each other and the main body of the wing though flapper valves, allowing fuel into but not out of the hopper tank. The boost pumps (only one per wing can be selected on at a time, so they are used on alternate days) send the fuel towards the engines, but on the way there some of the fuel is diverted down a side line to provide the motive force for a pair of jet pumps (the same as ejector pumps, look it up) to transfer fuel from the collector tanks to the hopper tank and always keep the hopper tank full to its fourteen gallon capacity.

Further downstream in that line is an electrically operated emergency shutoff valve, a filter, with a bypass line in case the filter gets plugged, a fuel heating loop through which an anti-icing valve will automatically meter fuel if need be, a fuel transmitter, engine driven fuel pumps, a fuel control unit, and the engine. There is no crossfeed system, but there's an electrically operated valve you can open that connects the two wing tanks through a pipe, and you can transfer fuel through it by sideslipping, or balance the two sides (they have to be within 500 lbs) by remaining in level flight with it open. Sophisticated, eh?

Fuel indication is through capacitance, with five capacitance probes in each tank. The cockpit fuel gauge reads in pounds and is corrected to read zero when only the thirteen pounds of unusable fuel remains. For reasons I haven't researched, failure of one of the probes causes fuel quantity to overread on the gauge, which requires 115V AC power for its operation. There is also a float switch in the hopper tank which illuminates an annunciator whenever there is less than 13 gallons in the hopper. The annunciator is labelled L/R XFER PUMP, because one reason for there to be less than 14 gallons in a hopper tank is that the corresponding boost pump failed, so the ejectors aren't transferring fuel from the collectors, and there is less than 600-700 lbs of fuel in the tank so that the hopper doesn't stay full anyway. If you turn on the other boost pump in that tank and the light goes out, then you had a bad boost pump. If the light doesn't go out, then it means one of
(a) you have two bad boost pumps and less than 700 lbs of fuel on that side,
(b) the boost pump is working and you have less than 75 lbs of fuel on that side, or
(c) the flapper valve that triggers the XFER PUMP light is stuck.
Option (c) is by far the most likely, and can be verified to near-certainly by knowing how much fuel you put in the airplane and crosschecking with the fuel gauge and the fuel flow totalizer. If no boost pump is working in a tank, the unusable fuel increases to 88 lbs, and the usable fuel will have been exhausted when the gauge reads 75 lbs. Because AC gauges freeze in place when power is removed, there is a test switch on the fuel gauge. When the test switch is depressed, the fuel gauge should indicate zero, if it's working correctly.

Here's some more about the boost pumps. The two pumps on any one side are exactly the same as far as I know, but one is called "main" and the other called "aux," just so you can tell them apart. The switch that controls them is a vertically mounted three position rocker switch, OFF in the middle, MAIN on the top and AUX on the bottom. For each wing the main pump runs on 28.5V DC electric from the corresponding essential DC electrical bus, and the aux pump draws power through the opposite bus. That way, with one essential bus failed, you can still have one operating boost pump in each tank.

There is a gauge showing fuel pressure between the engine-driven low and high pressure boost pumps. It requires 26V AC power and should read 20-30 p.s.i. while the engine is in operation.

And in case you're wondering, yes I am going to just spew airplane systems at you for the next little while. I'm writing multiple ones a day, so they'll last you a couple of weeks. This is what I have to know and do in order to get to the point where you're pushing the throttles forward. Feel free to e-mail me random quizzes on what I profess to know.

Variable Authority

Up to now in my career, I have flown airplanes that I steered on the ground through pure mechanical linkages powered by my own muscles. I was using levers to physically shove the nosewheel into pointing the way I wanted to turn the airplane. The Screaming Whippet one is too big for me to kick around by myself, or they don't want to make levers that big, so it uses electrically controlled, hydraulically activated, variable authority nosewheel steering. I have to remember that description in case I'm asked about it on the ride. (Ride is pilotspeak for flight test). I also have to remember a whole lot more about how it works.

First pass, what I remember and understand from the class and the reading without looking anything more up:

Nosewheel steering is on the non-essential DC electrical bus. It must be armed and activated to be used. You arm it with a toggle switch, the location and position of which I can't picture now and it becomes activated when the squat switch indicates that you are on the ground and one of the following things happens. Either a) the right speed lever is moved into the low position or b) a button on the side of the left power lever is pressed and held. (Yes, I have both speed and power levers: resolving units, you'd think you'd get a power lever by forcing the speed lever, but that would be a geeky joke and not the reality of this airplane). Once the system is activated, you steer with the rudder pedals, just like old times.

Moving a rudder pedal sends a signal to a potentiometer. There's a pile of potentiometers, I think it was four. One of them represents the input you gave to the rudder pedal, one the position of the nosewheel, one the target position and one for good luck. So maybe it was three. The difference between the target and the position is sent to a selector valve which shuttles the appropriate way to send hydraulic fluid to a piston operating rack and pinion steering to pivot the nose gear in the appropriate direction. The channels in the shuttle valve go straight through for left turns and criss-cross to reverse the pressure for right turns. When the commanded steering meets the actual steering, the system holds that input until a new input is received or the system is disarmed. In the later case it smoothly recentres. The maximum steering in this mode is ten degrees either side of centre, but you can get up to sixty-three degrees deflection in park mode, by pressing and holding the park button. This is for manoeuvring into a tight parking spot. I really hope I don't often have to parallel park this airplane.

There's an annunciator for the system being armed, an annunciator for it activated and a flashing one if it fails. Because it's an electrical system, there is a chance of transient weirdness, and transient weirdness is not something you want to see in large vehicle steering If there's a three degree disagreement between two of the potentiometers, representing some form of where it's requested to be and where it thinks it is going, the system disconnects. You can still steer with braking and power.

Now let me see if by re-reading the chapter I can fix that up, and add things I forgot.

There is a command potentiometer (my "input you gave the rudder pedal") on the left side of the rudder pedal linkage, and a fault protection monitor potentiometer (my "target position") on the right side. There are two more potentiometers on top of the steering actuator, a control follow-up potentiometer (my "position of the nosewheel") and another one for the fault protection monitor circuit. So I was right, there are four, and if monitoring faults is good luck, I got them all right. Well, let's see.

There is a "Nose Steer Computer/Amplifier" which "contains Servo Valve Solenoid drive circuitry to initiate steering based on Rudder Pedal Potentiometer and Nose Gear Follow-up Potentiometer Position." (Why yes, this training manual is apparently so old that it predates the late eighteenth century English move to distance itself from its Germanic roots and not capitalize all nouns).

Okay, reading the quasi-incunabulum more closely, I surmise that the follow-up potentiometer simply turns with the nosewheel steering column, and has the same type of electrical connections as the rudder pedal potentiometer. When the "wiper resistance," a term I am not familiar with, but which I'll read as "the combined effect of the electrical connection and the turning," of the two is the same, the steering is deemed to have turned as far as commanded. The hydraulic supply ports close, so the wheel is locked in the position it was steered to.

I think the Rudder Pedal Monitor Potentiometer must be at the same wiper resistance as the Rudder Pedal Potentiometer--perhaps one potentiometer can only be compares with one other potentiometer, so the latter needs the former to shadow it. My manual names former, and the fourth potentiometer, the Hydraulic Actuator Monitor Potentiometer only once, in the sentence, "In either case, if a difference greater than approximately 3 degrees exists between the Rudder Pedal Monitor Potentiometer and the Hydraulic Actuator Monitor Potentiometer, the protective circuitry within the computer will shut down the system." I can't quite follow that all the way, but I know it means that if the monitor circuit thinks that the commands sent to the hydraulic system are incorrect, it will disconnect the steering to avoid having an electrical irregularity steer an airplane off a runway.

Absent positive steering, you still have directional control of an airplane through braking and differential power, so this is better than definitive by incorrect steering inputs. The "in either case" above refers to the case of a wheel being locked in place despite commanded steering versus uncommanded steering occurring.

The arming switch is located on the left hand console.

I also need to remember the fault test switch and that the system acts as a shimmy damper when not activated, but left in what is known as castoring mode, and that on retraction it automatically centres because the centre position is the low point in the race ... ah I guess I don't understand that well enough to explain it clearly. Also variable authority. I'll say that again to make sure I remember it.

Today is, I believe, International Women's Day. There is one male on our course and the rest are females, who happened to all be connected. The man had a eureka moment when the women all had connections to one another, either having previously met, knowing people in common, or just the familiarity of being females in aviation. We were all talking about then and catching up. He suddenly realized what it must feel like to not be part of the "old boys' network," and the girls saw it at about the same time. We promised not to exclude him from our network, and of course had no intention to do so, but through the week I noticed that our conversations would drift into discussions of female interest topics like clothing, or career planning in the context of postponing or forgoing pregnancy and he would be unintentionally excluded by dint of not having experience or opinions. It must have been for him exactly as it is for me when my usually all male colleagues start discussing football, or someone getting drunk while hunting and rolling his truck. It's hard to get into a conversation when you can't identify with the decisions being made or discussed. I can sort of feel for the men who feel threatened about women in traditionally male-dominated fields, but I don't think it will hurt them to learn to say "aww" when they hear about strangers' babies any more than it has hurt the women to feign interest in football for social purposes.