Tuesday, August 30, 2005

Congratulations and Jealousy

I was working at my second commercial job when she got her first. She has just been hired by Air Canada. So it's possible, but I haven't done it. I'm beginning to doubt I ever will.

Monday, August 29, 2005

Nigerian Consultancy

I'm sure you're all familiar with the Nigerian scam wherein the widow of the late Foreign Minister Ufo Garatybo has a family fortune of TWENTY (20) MILLION UNITED STATES DOLLARS, but needs you to send her ten thousand dollars and all your bank accont details to help get it out of the country, for which service you will be rewarded with one tenth of the recovered cash. Recently I received the following e-mail from Nigeria requesting not money, but information on setting up an aviation service.

I am a B747 pilot flying presently for a cargo operator in africa in and out of europe.
i am also thinking of retireing soon in to banner flying in my country nigeria with my saving.
its going to be the first of that kind in nigeria with so much to make. how can i start?

Suddenly I'm an expert on banner towing in Nigeria? I sent him a quick generic reply, advising him to determine the applicable local laws, obtain a suitable airplane and banner towing installation, make arrangements with an airfield, and practice his slow flight.

And then he writes back. Apparently I am the world's foremost expert on banner towing in Nigeria.

Am happy u reply my mail, and i would just continue with u still i get started. The authourity does not have any laws set down now on banner towing. they are even talking to me to come together and set up one, i am putting a little of this and that from the FAA and the CAA to make up something for them. Give me a idea what it will cost to start.my bank would like to know. (2) the permission i have even with surport of the goverment, the elections are coming soon, they want thier banners towed. And with that speed , that no problem.

So I told him, "I have no idea of the cost of the required airplanes, maintenance, aviation fuel, facilities access, insurance, or government bribes in your country. If you don't, I suggest you shouldn't be trying to run an aviation business." I'm betting his next letter suggests that I invest in his sure-to-be-successful business. But perhaps I should instead sell him my consultancy kit "Setting up a banner towing operation in Nigeria." It will be dispatched immediately on receipt of his certified cheque or money order. I suppose I'd have to charge at least $1000 US for everything I know about banner towing in Nigeria.

If he's legitimate and/or persistant, Google will see that he finds this blog entry, but geez, Captain, if you ask random strangers on the internet for business advice, you deserve worse than a little mockery.

The individual previously named in this story turned out to be both legitimate and persistant, and has accepted my offer to remove his name from the posting. I have also removed the comments as it was the only way I could remove his name as the author of some of those comments. I hope that in the future he will take up my invitation to write about flying in Nigeria, for the blog readership.

Sunday, August 28, 2005

Ten Things Only A Pilot Cares About Her New Car

  1. The specified fuel capacity doesn't indicate whether it includes any unusable fuel.
  2. The fuel gauge is non linear and has no calibration, showing only the vaguest qualitative information on fuel remaining.
  3. The odometer, tripmeter, gas gauge and low fuel warning light are all combined in one multifunction display, giving a single point of failure for all information on fuel status.
  4. The manual does not list a speed for best range.
  5. It does, however, give a marvellous little chart showing the optimum speed for shifting gears, at different altitudes.
  6. The door open caution light is on the hot battery bus, meaning that it always illuminates when a door is open, even with the ignition off and the key removed.
  7. The low coolant temperature caution light always illuminates during the first few minutes of the trip, but according to the manual, action need only be taken if it remains illuminated for "a long time." It should be suppressed until after "a long time" so that the development of a problem presents a noticeable change to the caution panel, and so it doesn't irritate me when there is nothing I'm supposed to do about it.
  8. It has an event data recorder (i.e. a flight data recorder, for things that don't fly), that records the status of things like speed, brake and accelerator pedal depression and seatbelts, at the moment of airbag deployment. Cool. I never knew cars had those.
  9. The manual specifies a maximum carrying capacity of the car, but does not indicate how much options like an air conditioner add to the empty weight, nor does it specify if that max weight depends on a particular zero fuel weight.
  10. Use of a two-way radio in the vehicle could apparently affect seatbelt function. Even Airbus doesn't have fly-by-wire seatbelts.

So yeah, I replaced the car. It gets good gas mileage, holds me and all my stuff, and so far no one has driven into the back of it.

Saturday, August 27, 2005

Ever Have This Feeling?

I have no idea how I will find the time and energy to fulfil all the commitments in my life right now. I think I'll watch TV.

Friday, August 26, 2005

Complete Waste of Time

You've probably noticed a severe decrease in my blogging lately. Work has been busy, the weather has been grand, but neither has kept me off the internet. I've been absorbed fighting imaginary monsters and mixing imaginary martinis in the Kingdom of Loathing.

I've had the opportunity to build a cottage by combining cottage cheese with anticheese, to fight a possessed can of asparagus with a pet sabre-toothed lime at my side, and to slay stick figures with a giant discarded plastic fork. It is an utter waste of time.

I also had a job interview, with an enthusiastic CEO, but I don't meet the (foreign) government-mandated minima for the position.

Monday, August 22, 2005

Industry Update

This post consists mainly of the optimistic ramblings of a Canadian pilot interview preparation centre. These folks offered a free resume evaluation service some years ago, in order to build their contact database. At the time I thought they were wasting their time configuirng my 200-odd hour resume, but in retrospect it was quite a clever idea. They did a good job on my resume, gaining my trust, and now years later I'm far more likely to turn to them than any other company. What do they offer now? Inside information on the questions that are asked at airline interviews, and practice via a mock interview for actually handling the questions. Knowing what you're in for is a great head start.

Air Canada is leading the way as it receives new Embraer EMB170 jets every week and faces higher retirement rates. After years of no recruitment, AC is looking to hire between 600 - 800 pilots over the next 2 years. The Air Canada Interview Process includes a Personal Interview, a one hour computer based Cognitive Test, and a Medical. They no longer use a Simulator Evaluation to evaluate their candidates.

Likewise Air Canada Jazz is in a bit of expansion itself, taking delivery of new Bombardier CRJ705 Regional Jets (Jazz is the Launch Customer). Also some Jazz pilots have already interviewed and have accepted positions with Air Canada mainline. In combination with the new CRJ705 deliveries, this has resulted in the first pilot interviews at Jazz in a number of years. The Jazz Process involves a Personal Interview, and if successful, an invitation for a Dash 8 Simulator Evaluation to be conducted at a later date.

Skyservice is doing well in the Charter Industry and is actively interviewing and hiring pilots onto their Airbus A320/319 and Boeing B757/767 fleets. The Skyservice Process involves a Personal Interview with their Pilot Recruitment Team.

CanJet has started services across the country connecting it's main base Halifax to Vancouver through the major cities in between. With the hiring at Air Canada, and the acceptance of more used Boeing B737-500s, CanJet will be interviewing and hiring pilots from now until the end of the year. Canjet's Pilot Hiring Process involves a Personal Interview with their Pilot Recruitment Team.

WestJet is getting rid of it's older B737-200s in favour of their new Boeing B737 New Generation Airliners - the B737-600s, -700s, and -800s. The new Boeings continue to arrive in Calgary and the successful low-fare airline continiues to grow at a steady rate. WestJet will continue to hire pilots for the foreseeable future. The WestJet Process involves a unique Personal Interview with their Pilot Recruitment Team.

Canadian North of Calgary/Edmonton/Yellowknife continues their niche operation connecting cities and towns of the remote north with the southern centres of Calgary, Edmonton, and Ottawa. The Diamond Industry is booming in the north and Canadian North is taking advantage with their Boeing B737-200 Gravel-Kit Equiped Combis. These aircraft have a large cargo door installed on the upper forward left fuselage and thus have a configuration of near 50% passengers and 50% cargo. The Canadian North Interview Process involves a Personal Interview in Calgary, and if successful, followed by a Simulator Evaluation at a later date on the B737-200 Sim.

After many lean years in Canada, the excitement in pilot voices as they inquire about Interview Preps and our Resume Design Services is welcome. The great thing though about the increase in Pilot Hiring is that as carriers like Air Canada take on these pilots, the entire industry from top to bottom will be affected. New openings will pop up everywhere including at Flight Schools, Skydive Companies, Medevac Charters, Corporate Charter Companies, Tier III Turboprop Operators, and even some of the other airlines as some of their crews opt for a career at AC.

Outside of Canada, foreign airlines continue to hire Canadian Pilots into their ranks. Cathay Pacific will be back in Vancouver in September to interview the next batch of candidates, and the expanding carriers in the Middle East (Emirates, Qatar Airways, Etihad Airways, and Gulf Air) continue to take on experienced Canadian airline pilots who fit into their company cultures.

It's encouraging, and not all hype. My mammals list isn't quite as embarrassingly out of date as the list at right seems to indicate, but close. I'd better get moving so I can give you a proper insider's view of this industry.

Saturday, August 20, 2005


They call it AIDS, short for Aviation Induced Divorce Syndrome, and it's a serious problem. Pilots are away from home a lot. They get lonely. They are regarded as prime catches by the sort of people who fish. Meanwhile their spouses are home alone a lot. They get lonely, too. The pilot comes home tired, which may mean cranky, or uncommunicative or apathetic. Lack of communication, lack of sex, infidelity. Marriage breakdown. The guys say, "don't get married, just pick a woman you hate, and buy her a house."

I wasn't going to write about this phenomenon, because, like night stops in Shanghai, crazy flight attendant parties, and inflight meals that don't come out of my own flight bag, I thought it was something removed from my aviation orbit. And then I found out that one of my own co-workers is a victim.

As she said, it can happen to women, too. A long time stable marriage, with a child, and then he suddenly left her for another woman. It was so shocking. I don't even know her that well. I almost wished she hadn't told me. Take it as a warning, if you will. Or take it as a reminder to act on your priorities and cherish every minute of happiness. My condolences to anyone who has been affected by a the break-up of a long time relationship, whether aviation-related or not.

I took a long time to post this, because I suspect the pilot in question reads my blog. I'll take it down right away if asked.

Friday, August 19, 2005

My Doctor Never Mentioned

Note any surgical scars, tattoos or other marks. These may be useful for identification in aircraft accidents.

   -- From TP13312 Section 1

I ran across this gem in a manual instructing doctors who conduct qualifying medical examinations on pilots. Every year I submit myself to a medical examination designed to determine if there is any reason to believe that I might become medically incapacitated in flight. They keep stamping and initialing my form, so far. I've noticed the doctors asking 'friendly' questions about my job and home life, designed to ferret out sources of stress or mental imbalance. I've passed several different forms of hearing tests, including the one when I was supposed to answer a question whispered by a doctor with a difficult accent who was holding a sheet of paper over his mouth so I couldn't lipread. But I've never noticed a CAME inventorying my scars, tattoos and blemishes for some master database designed for disentangling my remains from my crewmates'. Lovely thought.

Tuesday, August 16, 2005

Hat and Shades

Pilots turn up fairly often in comic strips. Gary Larson has them gleefully inducing turbulence. The stereotype is so clear that there's a lot of humour to be gleaned from a few twists. And of course everyone is more interested in something that is about themselves, so of course I notice pilot jokes. I like the way "pilot" is so clearly defined here by two accessories.

That's Pearls Before Swine by Stephen Pastis.

Saturday, August 13, 2005

How to Land an Airplane

Someone did a Google search on that topic and found this blog. Some airplanes are equipped with internet access, but I'm going to assume the searcher was preparing in advance, and not in desperate need of the information. It's too late now, as that was a few weeks ago.

Just in case, let me present a quick step-by-step primer. Remember a good landing is one you can walk away from. (It's a great landing if the airplane is reusable).

1. Find a suitable landing site

The best place to land is an airport. If you have any problems, prefer the airport with the best weather, the longest, widest runways and the most extensive emergency services. If you haven't got an airport, choose the longest, flattest, hardest surface available, without obstructions.

2. Tell them you're coming

Tune the radio to 121.50 and announce your intentions. Use plain English (or your local language) not pilot speak. Something like "My name is Albert and I have an emergency because I have never landed an airplane before," will get a lot of people's attention. Tell them to the best of your knowledge where you are, what sort of airplane you are flying, how many people on board, and exactly where you plan to land. If you happen to know your flight number (it might be on your boarding card, or on a post-it note on the dashboard, because pilots can never remember it either) or the callsign of the airplane, that would help a lot. ATC will line up all the firetrucks for you and move others out of your way. They can also help you find an airport. Don't let them distract you from your primary task of landing. If they tell you to do something you can't do, refuse.

3. Prepare the cabin

Stow all baggage. Have people remove items like eyeglasses and sharp jewellery from their person and aggressively tighten their seatbelts. Review evacuation procedures. Try to keep the passenger alertness level above complacency but below panic.

4. Configure the airplane for landing

You need to slow down to a suitable approach speed. Too fast makes it hard to land, too slow makes it hard to fly, so you want to make an effort here. The air traffic controllers may be able to help you out. Maybe there's a TOLD card on the dashboard, or a placard listing approach speeds at different weights. Pull back the throttle(s). You'll hear the engine sound decrease, and the airplane will start to descend. Pull back on the yoke a bit to stop it descending and it will slow down instead. See if you can find a thumb switch on the yoke, or a vertically mounted trim wheel somewhere in the cockpit so you don't have to use a lot of strength to pull back. You'll also want the gear and flaps down. There are particular speeds at which these things should be deployed, but wrinkled flaps and torn gear doors are tolerable. The gear handle looks like a little wheel and the flap handle like a spatula. They should also be labelled. As a rough approximation, put the gear down with the airspeed indication at six o'clock and put half the flaps down, then slow to a speed at about the four o'clock position. Once you're happy with the speed, adjust the power so that the airplane is descending at a rate that will bring it to the runway and the ground at the same time.

5. Align with the runway

Bank the airplane towards the runway and then level the wings when you're pointing straight at it. Keep the wings level. You can do a bit of steering with the rudder pedals to keep the nose pointed straight ahead. Keep it straight. If it looks like you are going to land before the runway, increase the power. If it looks like you will go too far, pull the power back further and put down more flaps. Keep the airplane pointed at the runway.

6. Flare

When you get so close to the ground that you're afraid the nosewheel is about to crash into it, reduce the power to nothing and pull back on the yoke to level out. Don't pull the nose way up, just level out. The longer you can hold the airplane level with the power at idle, the slower the airplane will be going when it hits the ground. Slow is good, especially if you have no experience braking or steering on the ground. You both steer and brake with your feet on most airplanes as you are slowing down, but if you've never done it before, chances are you'll overdo it and go off the runway. Don't do anything too hastily, and remember the firetrucks are right behind you.

Good luck, and be cautioned: this website is no substitute for a good flight instructor. Aviatrix takes no responsibility for results.

I'd love to know how far off this advice is for your airplane.

Friday, August 12, 2005

Pilot Bars

Pilot bars could refer to the epaulette stripes that denote whether you are captain (four bars) or first officer (three bars). It could also refer to establishments that serve alcohol and which are frequented by pilots. There's one or two within a short cab ride of all but the most desolate airport. Before you go into the latter kind of bars, you have to remove the former kind of bars, along with your tie, your wings, and any other company identification, because most companies have a policy forbidding pilots drinking alcohol while in uniform, or while displaying company insignia.

The typical pilot shirt has a company logo embroidered over the right pocket, so technically you can't go to the bar after work without having a t-shirt or something to replace the shirt. In reality, we ditch the tie and the bars and wear the same sweat-soaked shirts to drink our beer as we did to land the airplane. A friend of mine, observing the lame tactics, such as turning down our lapels or scrunching into the corner, that we employ while trying to hide our logos suggested that pilot bars should have a supply of big happy-face stickers at the door, for us to paste over our company logos.

Tuesday, August 09, 2005

Expert Opinions

As everyone except the TSB offers an instant opinion on the Air France runway excursion, I encountered another example of the media consulting a dubious expert.

The Nanisivik airport serves the community of Arctic Bay, on the north coast of Baffin Island. It was originally built to serve a mine, but the mine shut down a few years ago, and, in wrapping up operations, cut off power to the airport. I've landed at plenty of airports not serviced with electrical power, but it's nice to have a functioning AWOS (automated weather observation something) and a vending machine with cold pop. The best part of this particular news story is the quote:

Rod Reid, a cargo handler at the airport, said he didn't feel it was safe for planes to land when the power was out.

All respect to cargo handlers, especially 1200 km north of Iqaluit, and he might even be a pilot working the ramp for an 'in' with a company, but was 'cargo handler' the highest level of expert commentary they could elicit on aircraft operations?

Monday, August 08, 2005

Legal Alternate: Part Two

A few days ago I began explaining the minimum weather requirements for an IFR alternate on a Canadian flight plan. See if you can remember what 400-1, 600-2, and 800-2 mean. Here's how to apply them.

Michael Oxner, who has a scanner and knows how to use it, has some approach plates online with beautiful explanations. I'll use his Moncton ILS or NDB RWY 29 (that will open in a separate window, if I did it right) as an example. The top right hand corner of the plate tells us the aerodrome elevation (the height of the highest point on the runways) and the touchdown zone (the first third or first 3000' of the runway, whichever is shorter) elevation for runway 29. They're both the same, at 232', which implies that the airport is flat. I like that in an airport.

Down near the bottom of the plate, opposite the category ILS you see 432 (200). The altitude 432' is the decision height while the (200) informs us that it's 200' above the touchdown zone, saving us from doing the arithmetic to subtract 232 from 432. The 1/2 RVR26 is the advisory visibility: 1/2 mile or RVR of 2600 feet, same thing.

To determine the required weather to file Moncton as an alternate, lets say that the runway 29 ILS is the only useable precision approach at the airport. That might be because there was no ILS for the runways 06/24, because the forecast wind was unsuitable for landing on any other runway, or because the other runway was unavailable for some other reason. So Moncton would have one useable precision approach. That requires weather of 600-2 or 300' and 1 above minima, whichever is greater. Adding 300 + 200 gives 500, and 1 + 1/2 = 1 1/2, so the standard 600-2 is greater, and applies. The forecast ceiling must be at least 600 feet above ground, and the forecast visibility two miles for this airport to be the alternate.

At St. Anthony, Newfoundland depicted at the bottom of the page, there are no precision approaches available, so we need 800-2 to use this as our alternate. But the MDA of 600' is 508 feet above the aerodrome. Adding 300 + 508 = 808, and 1 + 1 1/2 = 2 1/2, so the minimum weather is greater than 800-2.

Weather at the airport is always forecast to the nearest hundred feet, so when you need 808 feet, does that mean you need 800 or 900 feet? The changeover altitude is 20', meaning that a calculated required ceiling of 808 feet requires a forecast of 800', while a calculated requirement of 821 feet requires of at least 900'. Calculated visibility requirements of over 3 sm require no more than 3 sm forecast vis. There aren't many cases this pathological, but you can bet the guy who does your next PPC ride knows of one in your approach plate book.

I still didn't get to airports with GPS approaches or no approaches. There's so much in this tiny corner.

Sunday, August 07, 2005

Backing Up

Someone who has been watching carefully as jets leave the gates e-mailed me with two questions about airplanes leaving the gate.

Why is it that the nosewheel steering is disconnected prior to push-back?

Nosewheel steering is typically a mixture of hydraulic and mechanical connections allowing the captain to steer the nosewheel through thirty degrees or so on either side. When a towing bar is connected to the noseweel, and the aircraft is pushed backwards, or pulledto the side, the nosewheel can be turned a lot further, perhaps through ninety degrees. Damage could result to the steering if it were left connected. Obviously it is equally, if not more important to ensure that steering is properly reconnected after the ground handling.

Is it because of the lack of a rear-view camera that aircraft can't use reverse thrust to push themselves backwards instead of having to wait for tow-tractors?

Not really. The guy driving the tractor has better visibility than the guys in the cockpit, but it's still pretty hard to tell what's behind a large aircraft being pushed back. Accidents happen that way, even with wing walkers and walkie-talkie-equipped crews.

Remember, an airplane taxiing isn't like a truck driving. The motive force comes from the movement of air. In crowded gate areas, aircraft are sometimes damaged or even overturned by the jet blast of other airplanes manoeuvring. In order for an airplane to back out of the gate, the thrust of the engines would have to be directed forward, through the plate glass window where you're standing watching the airplane. The ground idle danger zone for jet blast extends 450 feet behind a medium jet, and it takes more than idle to start taxiing from a standstill.

Some airplanes simply have no reverse. They go forward or they are pushed backwards. Some airplanes are designed to develop reverse thrust on the ground, but with limits, for cooling. I flew one that was restricted to one minute in low temperatures, and only as absolutely required up to 30 seconds in high temperatures. Reverse thrust is generally intended to be used to slow down the airplane on the runway, after landing not for ground manoeuvering.

"I'm okay with women flying airplanes, just so long as they don't have to reverse them into parking spaces." -- old timer captain

Right after I wrote this page, I discovered that Boeing has developed an electrically powered nosewheel to allow ground movement with no tug, with all engines shut down. Air Canada successfully tested it in June.

Thursday, August 04, 2005

Plane Crazy

Here's another theatrical presentation with an aviation theme, this one much less morbid than the last one I mentioned. Plane Crazy (link plays music) is a musical about the Coffee, Tea or Me? age of aviation, "When Stews Were Sexy and the World Was Sexist." In the mid-twentieth century, there was a space of almost twenty years between the introduction of the birth control pill and the discovery of AIDS, that happened to coincide with a period of rapid expansion of passenger air transportation. As the promotional text for the musical explains it,

Plane Crazy is set during an explosive time in history: The intersection between the dawn of the Jet Age, the introduction of the Pill, the genesis of the modern Feminist Movement, and the Golden Age of Advertising.

Stewardesses represented the first-wave shock troops in a changing world. This was an exclusive sorority of women who had freedom. Freedom to travel wherever they wanted. Freedom to have sex with whomever they wanted. And freedom to have a career without needing the support of a man.

Sounds like some interesting social commentary attractively wrapped in songs and sexuality. It sounds like fun. I hope it's successful.

I wrote this entry some time ago while the website was part of a fund-raising effort to get the show produced. Today I'm a little busy to do part two on IFR alternates, but I've just discovered that the musical is opening in New York next month, so the time is right. And writer Suzy Conn is in Toronto; she's a Canadian like me.

Wednesday, August 03, 2005

Approach throughThunderstorms

I first saw this story in a previous version when all that was known was that the aircraft had gone of the runway and was burning. I did not expect the outcome to be so favourable. Apparently the Air France flight continued an approach to Pearson through a thunderstorm, went off the runway, off the airport and ended up in the Etobicoke river ravine. I think I've been walking in that ravine, right by the airport. Today everyone got out alive with fourteen (update: 43) out of 309 on board suffering minor injuries.

The accident caught my attention especially because it reminds me of another accident. I reached a milestone in my flying career on 2 June 1999, and then returned home triumphantly only to see pictures of American Airlines flight 1420 on TV. It had gone off the runway in Little Rock, Arkansas after a landing in a thunderstorm. The timing had a strong effect on me. The captain had been killed in the crash, and the first officer's leg was broken. He had made a weak attempt to prompt the captain for a go around, not quite intelligible on the CVR, but did not insist. I imagined the FO in that situation. He hadn't given himself the authority to stop what was happening, and then through comfusion and pain he would realize that the captain was unresponsive and now he was in charge. All together eleven people died there.

Thunderstorms bring almost every unfavourable weather condition at once; low level windshear, poor visibility, wet runways, and high gusting crosswinds make up only the beginning of the list. I'm thankful for whatever combination of flight attendants, emergency services and fate kept this one out of the fatalities column.

Additional Update: Holy c#@p, I've just seen footage of this on the National. They're calling it a "miracle." It's definitely dramatic.

Tuesday, August 02, 2005

Legal Alternate: Part One

Regardless of when she gets to descend, and whether she's governed by the approach ban or visibility, or MDA/DH alone, a pilot who fails to obtain the required visual reference to land must conduct a missed approach, and go somewhere else. If conditions are rapidly improving, or she has some other reason to believe that it's worth the fuel and time to make another attempt to land at the same airport, she may return for a second approach, but typically she turns for her alternate.

In Canada, every IFR flight must depart knowing that the weather at a specified alternate destination is forecast to be better than needed for landing. Not just good enough, but better, and they do tell you exactly how much better, depending on what sort of instrument approaches serve the airport. The weather is quoted in terms of ceiling -- the altitude above ground level of the bottom of the lowest layer of clouds, not counting layers that cumulatively do not cover half the sky -- and visibility -- how far an observer or RVR can see along the ground. These numbers are compared to the decision height or minimum descent altitude. MDA and DH are quoted in feet above sea level, because that's what the pilot reads on the altimeter, but this calculation requires feet above ground level. This is called height above touchdown, or HAT. For approaches where it may be necessary to turn or overfly the runway and circle back in order to land, the slightly different height above aerodrome elevation, or HAA applies.

If the alternate airport has two or more usable precision approaches to separate runways (not just opposite ends of the same runway), then for the typical ILS approach, the ceiling must be at least 400 feet and the visibility at least one mile. The typical ILS approach has a decision height of 200 feet agl and an advisory visibility of 1/2 mile. If, for some reason, the published DH or advisory visibility is greater, then in order to file that airport as your alternate, the ceiling must be 200' greater than the HAT and the visibility must be half a mile greater than the advisory visibility. We call this weather requirement "four hundred and one" and write it as 400-1.

If the alternate airport only has precision approaches serving one runway, then the weather needs to be even better. I'm not entirely sure of the rationale for this, because while it definitely gives you a better safety margin to have an extra runway available if something happens to one of them, even perfect VFR weather isn't going to improve your chances of successfully landing at an airport whose only runway has been closed due to a massive fuel spill. But when there is only one usable precision approach, the minima are 600-2, meaning a ceiling of 600' agl, which must be at least three hundred feet above the lowest usable HAT, and a visibility of at least two miles, being at least one mile greater than the advisory visibility.

Should the alternate airport be equipped with non-precision approaches only, the weather minima change to 800-2. The ceiling thus must be at least 800' or 300 feet above the lowest usable HAT/HAA, and the visibility at least two miles, still at least one mile above the advisory vis.

That's just the intro to Canadian alternate minima, but that's enough for one day. Tomorrow I'll tell you what happens if there is no IFR approach or only a GPS approach, and show you how to compare round number ceiling forecasts to the very specific numbers on approach plates. Also, see if the Americans who don't know can guess what it means that the standard alternate minima can slide.

Monday, August 01, 2005

Precision and Non-Precision

I've been avoiding stating the difference between precision and non-precision approaches as I discuss minima because it's too long for a parenthetical remark, so now I'll give it its own post. They are two classes of instrument approach procedures, based on the equipment available in the vicinity of the airport, and in the aircraft. The same airport, indeed the same runway, may have both a precision and a non-precision approach. I believe all Canadian precision approaches include a corresponding non-precision approach, but I haven't searched all my approach plates to make sure.

A precision approach provides both horizontal and vertical guidance to the runway. In other words, it's tells you if you're deviating to the left or right and it tells you if you're too high or too low, before you ever see the runway or any of the ten items associated with the runway visual environment. By far the most common type of precision approach, and really the only one available to civilians is the ILS. (It stands for Instrument Landing System, but we only ever say "eye-ell-ess.") Imagine a beam that extends from the desired touchdown point on the runway back up the approach, and imagine the pilot using instruments in the cockpit to keep the aircraft centred in the beam. That's not quite how the ILS works, but it's an adequate model. If you haven't found the runway by the time you reach decision height, usually 200' agl, you fly the missed.

A non-precision (NP) approach gives only horizontal guidance. That is, it tells you if you are off to the left or the right, but not how far above or below the glidepath you are. Of course it has to give some vertical guidance, which it does in the form of telling what altitude to start at, and what altitude to be at by each of a number of points, sometimes specified by DME (distance measuring equipment -- yes, aviation has some of the stupidest abbreviations) or passing overhead a radio beacon called an NDB (non-directional beacon). The lowest altitude you may descend to before sighting the airport is called the minimum descent altitude, or MDA. You stay at the MDA until you either see the runway or reach the missed approach point (MAP). If you see the runway, and it's possible to land safely from where you are, then you do so, otherwise you fly the missed.

One tricky thing about a NP approach is that the MAP may not be a specified point like "the beacon that broadcasts 'HI' in Morse code." It might be an amount of time past the beacon that broadcasts 'HI' in Morse cose, determined by how fast you're flying through the air, the wind strength and direction, and a little table in the corner of the approach plate. I think that sounds worse than it is, so I'll show an example.

I have here an expired approach plate for the ILS or NDB RWY 09 approach to the John G. Diefenbaker International Airport in Saskatoon, Saskatchewan. (Sorry, I don't have a scanner, and I don't know where to find it online). We'll imagine the pilot doesn't have an ILS receiver in her airplane, perfectly legal in Canada, so she'll be doing the NDB approach. The diagram shows the XE NDB (i.e. the beacon that broadcasts Morse -..- . in all directions) aligned with runway 09 and located on the ground 3.6 miles before the runway threshhold. According to the plate, once the pilot is cleared for the approach, and is within 100 nm of the airport, she may descend1 to 4500' asl. Within 25 nm of the XE NDB she may step down to either 3300', if she's coming from the west, or 3700', if she's coming from the east. Once she has reached the beacon, turned around, and established herself on the horizontal guidance of the approach, coming straight towards the beacon on a track of 087 degrees, she may descend to 3000'. All these numbers are on the approach plate, with little coded diagrams. As she passes overhead the beacon, she may begin descent to the MDA of 2020 feet (367 above the ground, according to the plate). If she had DME she'd probably use that to find the MAP, but if her employer would pay for DME, she'd probably have a functional ILS, too, so she has to use the little table.


She knows her true air speed for the approach is 120 knots, and we'll say she knows she is facing a fifteen knot headwind, so her groundspeed is 105 knots. That's faster than 90 knots, but slower than 110. From the table there's a 26 second spread over that 20 knot range, and five knots is a quarter of that, so six or seven seconds longer than the 110 knot case: giving a timing of 2:05. The pilot works this all out before starting the approach. On reaching the beacon she will start her stopwatch, reduce the power, and descend promptly to 2020 feet. For the best chance of landing, she must get there before her two minutes and five seconds have elapsed, because MDA or not, when the time is up, she's leaving. Most NP approaches are designed such that if you see the runway at MDA just as the time elapses you still have to go missed because they bring you out right above the threshold, too high to land. The trick is to chop and drop so that you are established at the MDA in time to see the runway.

This is where you want to look at the advisory visibility and calculate when you actually have to see the runway. The advisory visibility for the approach above is one mile. At 105 knots, she covers a mile in about 34 seconds, so she needs to be at MDA within 1:31 of the beacon to make this approach. When she crosses the beacon a 700 foot per minute descent rate should be enough to make that happen.

If the cloud bases are at 1900', no matter how fast she gets down and no matter how good the visibility underneath is, she's not going to see anything at 2020', and is really going to be wishing she had an ILS, because the DH for the ILS is 1853'2 and she'd be going home instead of heading to a motel in Lloydminster.

Technically, only ILS approaches have a DH. NP approaches may be based on a variety of navigational aids, but they all have an MDA and may have a time. GPS approaches for the time being are considered NP, but that may change.


1. I understand that in the United States she would need a separate descent clearance, but in Canada "cleared for an approach" allows her to descend.
2. Yes, 1853'. Not 1854' and definitely not 1852'. I may do another post on how they come up with these numbers.