Loadmeters and Bus Ties

A twin otter has two wings, two engines, two starter-generators, two main bus bars, and two little electrical gauges on the dashboard. There is one engine on each wing, one starter-generator for each engine, and one bus bar powered by each generator, but don't be so silly as to assume each gauge corresponds to one generator.

The gauge on the left is the DC Voltmeter. The needle on its face deflects from left to right over a scale from 0 to 30 volts. This is an indication of the voltage available at the left bus bar (which is normally connected to the right bus bar, so don't worry about it). The power source suppling that potential could be either or both generators, the battery, or an external power source. Ya, you can plug the airplane into an external power source, like your laptop, but that is only useful while parked, unless you have a really long cord.

The gauge on the right is more complicated. It's the DC Loadmeter. Its needle deflects from the centre to the left or the right. The centre is marked as 0 and the left and right extremes as -1 and +1 respectively. If you don't do anything, the gauge shows the charge or discharge of the battery, with each .1 on the scale representing 10 amperes. It shows negative deflection when you are running off battery alone, positive numbers right after the generators come online, and then spends most of the time sitting around zero.

Next to the gauge is a little selector switch, which gives the pilots something to fidget with in cruise, so the passengers think we're doing something important. The switch automatically goes back to BAT when you release it, but you can twiddle it to the left or the right to select L GEN or R GEN. In that case, the needle indicates the loading on the appropriate generator, with each .1 representing 20 amperes. Full scale deflection corresponds to the full 200A output of that generator. The generator outputs are expected to be within 20A of one another unless something is broken.

You have the option of removing the connection between left and right bus bars, useful in certain abnormal situations, but if one of the generators isn't working (definitely an abnormal situation), opening the bus tie will render some of the electrical services unavailable. As a pilot you have to remember what runs off the left bus and what runs off the right bus, so that you know what you are going to lose when you open the bus tie switch. In general, stuff on the right side is powered off the right bus bar and stuff on the left side off the left bus bar: left and right pitot heat, intake anti-ice, bleed air, windshield heat. But, and look for this sort of thing as a sign of quality airplane design, the lights alerting you to the failure of a generator are powered by the opposite bus bar from the one supplied by the failed generator. I always wonder whether they got that right on the first try.

Making Lemonade

"Mr. Leblanc admits the Jetsgo brand has blemishes, but he also says awareness has picked up."
  -- Ottawa Business Journal

Sure, his airline ceased operations in the middle of spring break, stranding passengers all over Jetsgo's routes, but look at all the free publicity! So you see folks, it was all a publicity stunt. Running a jet off the runway didn't net him enough ink, but this was what he needed to make sure the whole country has heard of Jetsgo. Passengers really do want the cheapest airfare, whatever it takes.

Yellowknife Road Trip

"Eighty percent of success is showing up."

   -- Woody Allen

You can't get a job in this industry just by sending out your resume, or making telephone calls. Not unless you have time on type and a current PPC, so you could slide right into the left seat and fly it away. You've got to show up, ready to work.

My only useful PPC is now expired, but I have enough total time to keep the insurance companies happy, so I'm employable. The only way I've ever got a flying job was by asking someone I already knew for one, but I had to meet the people in the first place. I'm planning to go to Edmonton, Fort Smith and Yellowknife.

I've already arranged the time off work. Once I show up, I just need to come through with the other twenty percent in order to get a job.

Birds at Airports

Airports attract birds. I whimsically speculate that as the birds are cruising by, they notice the huge metal birds all gathered together on the aerodrome. "Wow," they think, "there must be a lot of food down there to support that many birds. We'd better go check it out." Really, I doubt their little feathered heads are capable of that kind of deductive reasoning. It's probably more related to the fact that the huge area between and around the runways is usually uncut grass, ideal for the propagation of rats, rabbits and bugs. On rainy days the worms wriggle out of the soaking ground to avoid drowning, and lots of worms end up squirming nakedly on the pavement. Birds just see all this as a dog-and-cat-free smorgasbord.

Many airports, including the one I'm sitting at now, have bird eradication programs. These consist of dogs, guys with pickup trucks, and guns. All the ingredients of a country & western song except for whiskey and cheating women. "Trained" dogs (how much training does a dog need to bark furiously and run after birds?) are apparently very effective. I saw a TV show on it once, so it must be true. Here (yes, I'm blogging at work, so I guess cheating women do factor in this equation) there are no dogs, just a couple of guys driving around in a really big pickup truck wielding guns that make a lot of noise and smoke, but don't, I believe, actually kill birds. I disagree with this approach.

The birds aren't really scared of the guys in pick up trucks. The other day I watched a scene that could have been on America's Funniest Home Videos. The guys with the pickup truck kept driving towards a huge slow-moving great blue heron. The heron would then take off, fly around in a big circle, and land behind the pick up truck, or on another runway. Another day they had to close a runway for several minutes because a group of eagles had decided to park there, and really didn't care what anyone thought.

I don't think they should shoot the endangered birds, even though they are endangering humans. I think they should shoot crows and seagulls and let the eagles figure out that they might be next. Even if the guys in pickups were marksmen working all day shooting and killing birds, they wouldn't make a significant enough dent in their population to decrease the threat to aircraft. Likewise, killing a few isn't going to upset the delicate balance of nature. They should kill some so that the sticks that go bang make a significant impression on the ones that remain. When I was a kid my dad pointed a bamboo pole at a tree full of crows and they all took off and swirled away into the sky. "Why are they scared of the stick, Dad?" In that area the police did crow culls with shotguns. Crows, admittedly smarter than your average bird, had learned that when men point long sticks at your tree, you'd better get the firetruck out of there.

I like birds. I really do. I admire their flying skills. I would help an injured one. I want them to live. But I want them to enjoy that life in mortal terror of airplanes, runways and airports, so that they make their final flap among friends and family, and not in my face.

Radial Engines

When I mentioned that there was a type of airplane I want to fly before they are all gone, my readers instantly knew what type I was thinking of and where I'll have to go to fly one. The DC-3 was the original airliner. Read the memoirs of any golden age aviator and you'll find the DC-3. I'd rather fly a DC-3 than a triple seven, although the paycheque would be a lot bigger for the latter. Silly that, as there's more skill required to fly the old one than the automatic one. But that's economics.

I've spent some of the weekend trying to learn more about the care and feeding of radial engines, and I've ordered a book. I need to corner a Beaver pilot or two, because so far I'm not finding anything I didn't know. But I'll put down what I know, as I'll get a blog post out of it, and someone else might not know.

Radial engines are piston engines, with the cylinders arranged all in one plane, like the arms of a slightly spastic starfish. There are always an uneven number of cylinders, because the firing order goes around the circle skipping ever second cylinder, and an odd number ensures that works out. For example, if the engine has nine cylinders, like an old DHC2 Beaver, then the firing proceeds as 1-3-5-7-9-2-4-6-8. The crankshaft is a clever arrangement of articulating rods on a hub. I even managed to find a clever animation of how that works.

I know that a radial engine go through a lot of oil. We're talking a quart or two an hour. Although they don't exactly consume all of it. They use oil the way a small child uses food: flinging it everywhere. The joke is that a new pilot for a bush company can find all the camps just by following the trail of oil drips on the ground between them.

Some of that oil has a tendency to pool in the bottom cylinders when the engine is shut down. Oil doesn't compress the way air and fuel vapour do, so the result of starting the engine, or even turning it through by hand, could be a bent piston rod. It's called hydraulic lock and the only way to get rid of it is to remove the spark plugs of the lower cylinder(s) and let the oil run out. Sounds like a fun thing to do in the dark when it's forty below.

That's not all I know about radial engines, but it's all I have time to write.

An Almost Cunning Plan

Some ex-Skyward pilots who have just found work at Air Badger are on their way out this week from Thompson, where they know pretty much everyone in town, to here, where they hardly know anyone but each other. They will be staying pretty close to the airport where I work. Naturally I thought of taking a couple other local aviatrices to meet up with the guys for some welcome-to-town beers.

And then a plan comes to mind. What if we were to welcome them to town so enthusiastically that they were unable to make it to the Air Badger groundschool course the next day? Clearly we aviatrices would have to go in their stead. Someone's got to fill the pilot seats in Badger's fleet. That would teach them a lesson for being better qualified than us for jobs we wanted, eh?

My plan has at least three major flaws:

• I could never be that mean.
• These guys are from northern Manitoba. Who can afford that much beer?
• They read this blog.

Looks like I'll have to revise the plan. I could kidnap them, but I don't have a basement to keep them in, nor a backyard to bury the bodies. Maybe I'll just meet them and be nice.

Also I met a guy at work today who flies for Air Hyena. They operate a type that I absolutely have to fly before I die, or they're all gone, and apparently I have the qualifications they want, so Tuesday I'm giving the chief pilot a call, and we'll see when I can get out to Hyena to follow up and convince him to hire me. If I don't mention calling Hyena in Wednesday's blog then I'm obviously not serious about this aviation thing.

Would You Refuse?

The day before Jetsgo shut down, thirteen Jetsgo pilots received memos telling them to ferry airplanes to Quebec City for so-called urgent maintenance. Airline founder Michel Leblanc had supervisors issue the fake AD notices, in order to gather the fleet in Quebec City before the public announcement. Leblanc said the ruse was necessary to ensure compliance with the order, and that half the pilots would have refused, had they known the true purpose of the ferry flights was to turn Jetsgo into Jetsgone.

M. Leblanc has extensive experience with defunct airlines, so I imagine his "half of them would have refused" statement is based on experimental evidence, not conjecture. I know it happens. I've even heard of a pilot flying an employer's airplane to an undisclosed airport and hiding it there, pending receipt of wages owed.

Had I been working for Jetsgo, with a $30,000 debt to pay off, and been told to ferry the airplane because the company was shutting down, I might have become so angry that I would be legally obliged to refuse the flight, for the sake of aviation safety. But if my emotions were under control, I'd probably be in the half of pilots that would do the flight. I'd hope my co-workers who refused would understand that I wasn't licking the boots of the management that had kicked us. It's just that knowing it might be a long time before I flew a jet again, I'd want to squeeze the last drop of flying out of the defunct job.

F_CK!

Q: What is a word that starts with "F" and ends with "UCK" that you might hear someone say during an emergency?
A: Firetruck.

Michael Oxner's relayed story about a forced landing reminds me of my favourite F-word. ATC always calls the firetrucks out at the first hint of an emergency because everyone agrees that the fewer seconds anyone spends in a burning aircraft, the better. The only drawback is that it tends to make the passengers think the situation is worse than it is. The firetrucks enter the runway just as you pass over the threshhold and race down the runway with you so they are right there when you stop.

The first time I had firetrucks called for me, I knew it was completely unnecessary, but we'd said the word "smoke" on the radio, giving ATC no choice but to press the firehall button. I chatted with the firemen (hey, what girl wouldn't?) and learned that they appreciate the drill, and would rather it be nothing, just as we pilots would. So I showed them the relevant features of the aircraft, like where the fuel was kept, where to cut through the fuselage without cutting fuel lines, and how to switch the fuel off, and got on with my paperwork.

Reading Dave Anderson's reaction to being told the firetrucks are being called makes me realize there are three benefits to ATC having itchy 9-1-1 trigger-fingers.

Rapid response to real emergency need.

Currency and practice for the firehall

Acclimatisation of pilots to the presence of firetrucks

Firetrucks become part of the routine, like the paperwork. (Don't think I work for a company where emergencies are routine. It only takes a couple. Pilots learn fast.)

Daytime Flying Only

This story takes place at a small airline operating out of a tiny aerodrome with no airport security. At check in, passengers exchanged their tickets for a boarding pass, but instead of printed paper boarding passes, the passengers received reusable laminated cards. The only thing printed on them was the logo of the airline. The passengers sat in the waiting area with their cards, and then, when the airplane was ready for boarding, exchanged their cards for admission to the airplane. This was perfectly legal and generally worked well for the airline.

One day, there were two flights boarding at once, and the busy customer service agents pressed a captain into service collecting boarding cards from the passengers for his flight. "The green cards are for your flight," she said. "Don't let anyone on who doesn't have a green card." Collecting cards is not rocket science, and the captain good-naturedly accepted the task and the instruction. The passengers were boarded and briefed, and the flight departed on time.

The first officer radioed dispatch as required, with time off blocks, time up, and a head count. There was a discrepancy between the dispatch numbers and the FO's numbers. after some recounting and a few radio calls back and forth it was discovered that one of the cards the captain had collected was not green, and the airplane was carrying a passenger who had bought a ticket for the other flight.

Why did it happen? I don't know for sure, but I suspect that the captain's medical certificate was printed with the words RESTRICTED TO DAYTIME ONLY. MUST HAVE TWO-WAY RADIO FOR CONTROLLED AIRPORTS. Such a restriction is placed on the medical certificates of pilots who are colour blind. They cannot distinguish between a red light and a green light to determine the direction of flight of other aircraft at night, or to receive instructions via light signals from a tower controller. And a red card looks the same as a green one.

That airline operated daytime flights only. Such a restriction might have helped the captain get the job initially, proof that he would remain with the company, not going on to the next level of commercial aviation. And it would explain why he did not seek out a higher job, despite his experience and competency. I never asked him.

The passenger was neither angry nor anxious at the unexpected diversion in his travel plans. He embraced the experience as an added bonus in his travel arrangements, an extra destination for the same price. And the little airline made sure he made it to his international flight in time.

Intertwingledness

Not only does everyone in aviation know everyone else, but everything affects everyone else. It's not simply empathy that makes me regret airline troubles. Troubles at Skyward and Jetsgo not only eliminate those companies as potential employers, but increase competition for other jobs.

Skyward hasn't flown in weeks. Some of those pilots are hanging on in Thompson, but others have left town to look for other work. Badger Air hired a number of pilots who had been idled by Skyward's continued OC suspension. Ex-Jetsgo folk are unlikely to be looking at Badger, but they will be competing against people who have jobs I want for the next level jobs. It's an elaborate game of musical chairs, except there's hardly ever any music. Just every so often your chair collapses and you have to scramble for a new one.

A Third Post about Timing Holds

In two recent posts I've been dissecting hold timing. The goal is to fly a racetrack pattern such that, despite winds, it takes exactly one minute to fly the inbound leg. Clearly, if the first inbound leg takes you less than a minute, you need to fly longer outbound, and if the first inbound leg takes more than one minute, you need to fly for a shorter time outbound. The challenge lies in how much more or less.

As I mentioned before, I subtract two thirds of any excess inbound time from my outbound leg, and add one and a third times any shortfall. A colleague just hacks off half the excess and adds all the shortfall. He's good at math, and conscientious, so I pulled out Excel to find out what he knew that I didn't.

As I made up the table below I realized that if the first calculation gives me an inbound time of less than 20 seconds inbound, I fly for 20 seconds, which helps me not overshoot. I also don't make a correction based on the very first inbound leg, because that's part of the entry, and not to be trusted. I probably have more arbitrary rules like these that I haven't even noticed.

The values in the table below use the inbound leg distance calculations from my last hold post and the formula distance equals speed times time, with speed being the true airspeed of the airplane plus a tailwind or minus a headwind.

IB #1 time	OB #2 my way	OB #2 his way	IB #2 my way	IB #2 his way	OB #3 my way	OB #3 his way	IB #3 my way	IB #3 his way
10	126	110	43	35	149	134	54	47
20	113	100	52	44	125	116	58	53
30	100	90	55	49	106	101	59	56
35	93	85	61	54	93	90	60	59
40	87	80	61	56	86	84	61	59
50	73	70	60	57	73	72	60	60
60	60	60	60	60	60	60	60	60
75	50	53	64	66	48	50	59	57
83	45	49	65	69	42	44	59	57
91	39	45	65	71	36	39	59	56
113	24	33	62	75	23	26	60	56
150	20	15	80	71	7	9	64	59

The above data leads me to conclude that with light to medium winds, both methods work fine, mine a bit better, but not worth bragging about. For strong headwinds on the outbound, giving an initially very short times on the inbound, adding one and a third the shortfall works better than just adding the shortfall. For strong tailwinds on the outbound, subtracting the whole excess works faster than subtracting two thirds of it. Which makes perfect sense.

I initially set up my spreadsheet looking at aircraft of different speeds in different winds, but discovered that it makes no difference what combination of wind speed and airspeed produce a given inbound time, any initial inbound time corresponds to a particular outbound time that will give a one minute inbound. One could make a computerized hold timer that contained a database, such that when you hit stop on the inbound leg it automatically looked up the value and set up a countdown timer for the appropriate time on the outbound leg. Or you could have a printed table stuffed in with your approach plates, giving the same effect.

No one needs to, because as long as you are correcting in the appropriate direction, a few iterations will converge on the appropriate outbound time. I even tried setting up my spreadsheet so that the correction was a random number and if I limited the number so that the values didn't overshoot, after four turns in the hold, the timing was within a few seconds.

Why do we do this? Why don't they protect airspace based on a one minute outbound, and tracking inbound, so no one would have to calculate anything? I think they even do that in Europe. Perhaps it's a bit like the practice of putting mirrors in elevator lobbies. It gives you something to do while you are waiting, thus making the wait seem shorter.

I've had enough of holds for now, even though I haven't touched correction angles or hold entries.

Pilots are Rude

Q: What do pilots use for birth control?
A: Their personalities.

This post from Douglas' Weblog complains about ATC rudeness not pilot rudeness, but it may have the same cause.

I once heard one flight attendant explaining to another about pilots. It went something like this. "You know how we say, 'Oh could you please pass me that?' or 'Would it be a problem for you to do that?' Well pilots don't do that. They talk very directly. They just say, 'put that here' or 'give me that' or 'anti-ice on.' You think they are being rude, but that is how they talk to each other and on the radio, because they have to talk fast."

Very enlightening. If any pilot scoffs at the idea of carry through from cockpit SOPs or radio language into social interaction, just mumble your reply. "Say again?" they'll ask. I've heard a controller say simply "unable," during a normal, non-radio conversation where "I'm sorry, that's not going to work out," would have sounded a lot nicer.

On the radio, politeness can be rudeness. There's a controller I know who prides himself on his friendliness, but in busy airspace I don't want to spend the extra second listening to him wishing me a 'great day' on the ATIS, while I'm waiting for it to cycle through and give me the active runway. He thinks it doesn't matter because it's at the end, but when we tune the ATIS we usually come in at the middle, and have to listen to the middle, the end and then the beginning. So one second of niceties anywhere is a wasted second I could be using to get my clearance, except that the radio is blocked by a handoff involving reciprocal best wishes for the future.

Expressing maximum information with minimum words and minimum ambiguity is a learned skill. If you want to waste time and go on and on about something, keep a weblog. And have a great day.

1960s Era Turboprop

A CBC story on an air crash near Varendei, Russia terms the Antonov-24 "a 1960s-era turboprop." While that's true, I've flown a 1960's era turboprop and I think our passengers would not have been so pleased about the airplane if we'd called it that. I think the average reader will come away from reading that "hundreds of the Soviet-designed aircraft are in service in Russia and the former Soviet republics," with the idea that operating airplanes of that age is a dangerous practice unique to impoverished areas of the world. There are a lot of good airplanes of that vintage operating in Canada. The shape of airplanes has changed a bit with fashion, but the 1960s-style fin on an airplane isn't as distinctive as the ones on a car.

Jetahol

Fuel prices are heading up through another roof, but Brazil has an answer.

Embraer just delivered the first commercial aircraft to run on ethanol. Apparently there are already 400 airplanes running on ethanol in Brazil, this is just the first in commercial production. CBC claims that the aircraft is a commercial jet, but the press release makes it clear that the EMB202 Ipanemao is a single-engine crop sprayer, with a 300 hp engine, presumably piston. Embraer also offers a retrofit kit, and plans more ethanol-burning aircraft. Brazil has a domestic supply of ethanol, made from a byproduct of sugar cane processing.

As a Canadian, I can't link to Embraer without mentioning Bombardier. The two companies are both adept at producing regional jets, attracting governement handouts, and whining internationally that the other offers unfair competition because of the level of government subsidy. Fortunately, Bombardier has a story today, too.

The Bombardier Board of Directors has given the go ahead to offer the C-Series. Based on customer response, and government subsidies, they may actually make the thing, basically a Canadian answer to the B737. No word yet on whether there will be a version that runs on fermented maple syrup.

More Hold Timing

I figured out my hold timing puzzle in the shower. I had made it far more complicated than I had to.

See, while I need calculus to determine the travel of the aircraft at an arbitrary time t, I don't need it at all to determine the total travel during a 180 degree turn. I am considering only the distance the aircraft moves in the direction parallel to the inbound radial; the distance along the curved track and the distance the airplane moves perpendicular to the inbound radial are not relevant for this calculation. Performing a 180 degree turn in still air, the aircraft covers zero distance in the direction parallel to the inbound radial, so I can consider that the airplane is standing still for one minute, under the influence of the wind w. Speed times time equals distance. During the one minute turn, the aircraft travels a distance in nautical miles of w/60. (The 60 is the result of multiplying by 60 and dividing by 3600, because t is in seconds and w is in knots).

With this amazing escape from the need for definite integrals, I'll consider the case where we have a headwind on the outbound leg:

If there is a headwind on the outbound leg, the aircraft finishes its turn before passing abeam the fix, so the pilot travels that distance w/60, in order to draw abeam the fix, and then starts the timer. Thus the time taken to make up that distance is irrelevant. The pilot then flies outbound for one minute, covering a ground distance of (v - w) / 60 nautical miles, where v is the true airspeed and w is the wind speed. At the other end, of the hold, the turn to inbound ends up closer to the fix than it started, so the inbound track is w/60 shorter than the outbound track. Therefore the length of the inbound straightaway on the first turn is (v - 2w) / 60, and the time required to fly it will be speed divided by distance: 60 * (w + v) / (v - 2w).

Now the case where there is a tailwind on the outbound leg:

If there is a tailwind on the outbound track, the aircraft passes abeam the fix w/60 nautical miles before wings level, so the outbound distance (v + w) / 60 is increased by w/60. The outer turn drifts the aircraft a further w/60 nautical miles from the fix, so the inbound distance is (3w + v) / 60, and the time recorded for the first inbound leg will be 60 * (v - w) / (3w + v).

Initially I thought I could consider only one wind direction, without loss of generality, because the wind velocity could be positive or negative, but that doesn't work because the procedure changes.

Honestly, while I'm in a hold I think normal thoughts like "ack, the timer didn't start," "What was my EFC time again?" and "damn, I really have to pee." I only think about this stuff on the ground.

Next time I'm on the ground, I'm going to crunch some numbers through Excel and find out which is the best procedure to determine how long to fly outbound.

Inspiration

So I'm driving home after a long day at work. I've had two strong disappointments in the last twenty-four hours. I'm tired. I've had a headache since two pm. My headset doesn't usually hurt my head, but it was bothering me today. It didn't seem to matter how I adjusted the radio, it was either too loud and gave me a headache from the noise, or too quiet and gave me a headache from straining to hear. This isn't whining, I promise. This is context.

I'm driving home, and I'm thinking about my career, wondering if I have, in Peter Principle fashion, reached the pinacle of my career. I'm considering concentrating all my energies at excelling at my current job, instead of beating my head against the next level. They are tired, headachey end-of-the-day thoughts, because deep down I know I'm good at what I do. And then a song comes on the radio.

It's a country song, one so generic that I can't even Google it, because all the lyrics are cliches. Like many country songs, the verses are a series of vignettes, in this case about various people who had every reason to give up, but didn't: the couple who had been told by the nth doctor that they couldn't conceive, the lonely single mom waitress who can't make ends meet, you get the idea. And in each case the verse ends with the revelation that the couple is already pregnant, or the regular customer she's so fond of has already bought an engagement ring in order to make his proposal. They "just don't know it yet." The song urges the listener not to give up on hopeless causes, nor to underestimate the power of the heart. Standard country fare. But the coincidence of timing gets me, and it chokes me up.

I wouldn't blog about my fatigue-induced hallucinations that a song on the radio was speaking to me, except that when the song ended, the DJ announced, "This song brought to you by Badger Airlines." Really. Except he used their real name.

Update: one of my readers found the song online. It's by Canadian artist J.R. Vautour.

Hold Timing

Sometimes IFR aircraft (aircraft on flight plans that allow them to fly through clouds) have to stay in one place and wait, while they are flying. Typically they'd be waiting for their turn to land at the airport, and the way air traffic controllers say "take a number" is by issuing a hold clearance.

A "hold" is an oblong path: two parallel straightaways connected at the ends by semicircles. It is defined by a point called a "fix," a direction to that fix, an altitude, and whether the turns are to be made to the left or the right. The pilot identifies the fix using radionavigation equipment. The oblong is flown so as to put the fix at the end of one of the straightaways, just before a turn. Sometimes the length of the straightaway is defined in miles, but usually the length is defined in terms of time: the inbound leg is supposed to take one minute, or, if the hold is flown at an altitude above fourteen thousand feet, a minute and a half. With no wind, the opposite straightaway would require the same time. In wind, the timing of the outbound leg must be adjusted so as to satisfy the timing of the inbound leg.

Pilots' web has a great picture.

Imagine the wind is such that the aircraft experiences a tailwind during the outbound leg. That will make it cover distance faster, so that when one minute has elapsed and it turns inbound, it is further from the fix than it would be in still air. But if there is a tailwind outbound, there is a headwind inbound, so the airplane not only has further to go, but covers the distance at a lower speed. Reaching the fix, the pilot will discover that the inbound leg took more than one minute. On the next leg, she flies outbound for a shorter time, to compensate. But how much shorter?

There are many rules of thumb. During my initial training, I learned that if the inbound leg took more than a minute, to take two thirds of the excess inbound time off of the outbound time on the next leg. If the inbound leg takes less than a minute, add one and a third the excess to the next outbound leg. A pilot I respect, who can talk mathematical rings around me, subtracts half the excess or adds all the shortfall. As long as you're correcting in the right direction at each turn in the hold, you'll eventually converge on an outbound time that gives you a one minute inbound. It's a cockpit not a calculus class.

This being the internet, not the cockpit, I have filled a few sheets of paper with calculations, and determined that the distance travelled in the direction of the inbound track during a ninety degree rate one turn away from the inbound track is equal to the definite integral from t=0 to t=30 of (v cos (3t) + wt) dt, where v is the speed of the airplane and w is the wind speed. That ground to a stunning halt when I realized that whatever part of my brain had once known how to integrate trigonometric functions has found a new life, possibly storing and cross referencing the details of Friends episodes.

If someone has a more cooperative calculus-related brain segment, and wants to help out here, here are a couple more things to know about the path in the hold.

According to AIP-RAC 10.2, we "are expected to make all turns to achieve an average bank angle of at least 25 degrees or a rate of turn of three degrees per second, whichever requires the lesser bank." That "three degrees per second" turn is a common requirement, known as a rate one turn. We even have a rule of thumb to determine the bank angle in degrees that will produce it: ten percent of airspeed (in knots) plus seven. So for an aircraft flying at an indicated airspeed of 175 knots (the maximum permitted in a hold for any propeller-driven aircraft), the bank angle for a rate one turn is 175/10 + 7, or 24.5 degrees. Therefore, for all propeller-driven aircraft the 180 degree turns at the hold ends will each take one minute.

Timing of the outbound leg starts abeam the fix or when the wings are level after the turn, whichever comes later. Timing of the inbound leg starts with wings level. I have deliberately neglected the effects of wind not parallel to the inbound track.

Sweet Wine or Sour Grapes?

I should find out by tonight if I'm going to be typed on the Z92. That means the next post to this blog will be either an incoherent jumble of keystrokes made by me bouncing off the walls in ecstatic delerium, or a highly technical treatise on timing holds, as I focus on something else to avoid lobbing my sour grapes around the internet.

Jetsgo Gone

I've been trying to post this since my first cup of coffee this morning, but Blogger refuses to accept it.

Discount carrier Jetsgo announced early this morning that it is suspending operations, and will be seeking bankruptcy protection. I was wondering what their business motivation was for advertising one dollar fares to a number of destinations. Now I know. It was desperation.

Transport Canada was looking at the company for a few problems, but nothing that would have shut them down. They just weren't able to compete. All jokes, snide remarks, and competition-bashing aside, it's not the employees' fault. If your last paycheque said Jetsgo and you've just found out that there won't be a next one, I'm sorry to hear about you losing your job, and wish you the best of luck at finding the next one. Anyone advertising an MD-80 job this month is going to have a lot of applicants.

Playing With Fire

From AIP-AIR Annex 1-4, Survival Advisory Information

In the hands of a trained person, pyrotechnics can be very good. In hands of a novice they can reduce chances of survival.

Maybe I have an odd sense of humour, but it makes me laugh. I imagine the various ways in which a novice could use a flare pack to reduce his life expectancy.

That entire survival section in the A.I.P (Aeronautical Information Publication) seems to have been written somewhat tongue in cheek. The attitude seems to be, "If they aren't smart enough to realize the essential minimum equipment, they won't be smart enough to realize that they are being openly mocked." How else do you get advice like this?

Training is also needed in how to melt snow in a container over a fire.

Hint: don't use pyrotechnics. Here are some tips and some more.