Land and Hold Short

Anyone who flies in private planes knows what a normal airport looks like: it has one or two runways, an FBO, and maybe a restaurant and a little terminal building used by a commuter airline a couple of times a day. The airport was originally built 5-10 kilometers outside of town, but it is now surrounded by bland new subdivisions. If you want to get anywhere interesting beyond the airport restaurant, you have to take a taxi, borrow a crew car, or bring a fold-up bicycle in the back of the plane. One of the real joys of private aviation, though, is finding the abnormal airports, the ones that are unusual, interesting, worthy destinations in their own right, or that allow you to walk straight out of your plane to places you want to go.

My personal favourite abnormal airport is Toronto City Centre (CYTZ, also known as Toronto Island). The airport is located on an island in Lake Ontario, separated from downtown Toronto only by a channel crossed by the world’s shortest ferry ride (about 400 feet). You can tie down your plane at the Esso FBO (for my Warrior, it’s CAD 20/night, first night free — that’s cheaper than parking a car in downtown Toronto), hop on the ferry, then walk 20 minutes to Union Station and get on the Subway to go anywhere in the city. Paul Tomblin has a lot of great pictures here. Fewer and fewer cities have downtown airports now, and Mayor Daly’s secret destruction of Chicago’s Meigs Field, at night, was a warning to all of us to fight to save these gems.

Tim Bray recently wrote about a different kind of abnormal aerodrome, the seaplane base in Vancouver’s inner harbour. Like Toronto/City Centre, this base is downtown, but it’s actually out on the water, so a rogue mayor cannot simply bring in bulldozers in the middle of the night and tear it up. Floatplanes are a central part of the Canadian myth, and the bush pilot in the float plane is probably the closest Canadian equivalent to the American cowboy on the horse — a medium or large inland lake full of cottages will often have at least one floatplane tied up to a dock, and many northern communities rely on planes for everything, from food and medicine to CDs and school textbooks.

Floats are more dangerous than wheels (ask the insurance companies), just like a horse is much more dangerous than a minivan, but that’s a risk many people are willing to take for the convenience of being able to land so many places. Flying across the strait to Victoria sounds like a whole lot more fun than taking the ferry, and I could probably spend a happy afternoon at the seaplane base just listening to the radial engines on the Beavers — I am Canadian, after all. I’ll have to make a proper visit to Vancouver some day.

With Halloween and the end of Daylight Savings Time closing in, it’s time to start getting my plane, my house, and myself ready for the winter. A lot of pilots put their planes away until spring but I like to keep mine up in the air year-round — after all, that’s one thing we pilots can lord over the boaters, who get maybe 3-4 months of use. Still, winter flying is a challenge in Ottawa, a city where it’s not unusual for winter temperatures to dip below -30 degC, especially since my plane is tied-down outside year round.

Winterizing the House

Winterizing a house in central Canada means disconnecting the hose and turning off the outside water tap (otherwise the pipe can freeze and rupture), putting up storm windows, adding new weather stripping under the doors, changing the furnace air filter, getting out the shovels and sand and salt, putting away the lawn and porch furniture, and making sure all the fire and CO detectors work. It’s really the first of the pre-Christmas rituals: when I’m putting up the storms, I find myself starting to think about what presents I’m going to buy people, and I start deciding that maybe it won’t be so bad hearing tinny, piped-in mall Christmas muzak after all.

Winterizing Myself

Winterizing a person is a bit of a different kind of challenge. Of course, you start by putting away all the summer clothes, the thin pants and shirts, the shorts, and so on, and pulling out the sweaters and thick chinos. The thick winter coats, boots, hats and mittens come out of the basement and up into the coat closet, replacing the rain coats, rain boots, and umbrellas of the summer. For the last couple of years, however, winterization has also meant spending 10-15 minutes every morning in front of a home light therapy lamp, to help my body and brain get going with the shorter, dimmer daylight that we have to live with until spring: I decided that I don’t want to drag myself through any more winters with a fuzzy brain and heavy limbs.

This year, however, I’m adding something new: I managed to start running again last spring, and this time, I don’t want to have to give it up for the winter. I’m still running in the early morning, before sunrise, but plan on switching to early afternoon in November to take advantage of the extra warmth. To help me through the cold temperatures, I paid a visit to the Running Room and spent way too much money on layers of winter running clothing. So far, I have not had to deal with temperatures below 0 degC, but I really want to make it all the way through to spring this time. I find myself running shorter distances, slower, than I was in the summer, but as long as I keep moving, I’ll be happy.

Winterizing the Plane

Tomorrow I’ll bring the plane into the shop for some winter preparations. With multigrade oils, it’s no longer necessary to change to a different oil type for winter flying, and my muffler shroud has already been inspected for potential carbon monoxide leaks into the cabin heater (an annual inspection is mandatory in Canada), but I have two big problems that will make winter flying more than a bit unpleasant: my heater is jammed off, and my pilot-side floor vent is jammed open. I have flown with outside air temperatures as low as -37 degC; at full blast my heater can just barely keep the plane warm under those conditions; I don’t want to imagine it with the heater off and cold air blowing on my feet.

Most pilots also remove their wheel fairings for the winter. The official reason for doing so is to avoid having hidden ice build up inside, adding weight and throwing off the plane’s balance, but I think the main justification is that it’s just too hard to keep the tires inflated with the fairings in the way when it’s so cold out: who wants to take off mittens and fiddle with the valve underneath the fairing? I’ll probably take my fairings off again this winter and learn to live without the extra 7 knots that they provide.

Winter flying can be fun. The air is often brilliantly clear (compared to the soupy muck we get in the other three seasons), takeoff and climb performance is awe-inspiring, and airports are not crowded: sometimes you can fly into a largish airport like North Bay and find out that you’re their first 100LL fuel sale in three or four days. One big advantage of the cold up here is that it’s often too cold for aircraft icing, so it becomes reasonably safe to fly in cloud again: the most dangerous times for aircraft icing are October and April, not January or February. And sitting snug in a warm cockpit looking out at the brilliant frozen winter landscape underneath is awe-inspiring.

On the other hand, like winter running, winter flying means spending more time to do less. Taking covers off the wings, stabilator, cowling, and canopy before every flight and then putting them back on afterwards adds at least 15 minutes to every trip (more in a strong wind). Once the temperature is below about -5 degC, I have to remember to call the night before to have my engine heater plugged in, or else wait for 20 minutes while the Hermann Nelson kerosene heater blows hot air under my cowling. Sometimes, especially when I’m planning a family trip, I’ll have the plane towed into the club’s heater hangar overnight so that we can preflight and load up inside, but that often means an extra half hour before planes can be rearranged and the door opened. There are also other unexpected surprises, like finding out that the snow hasn’t been plowed off the apron.

Winter flying also means winterizing the pilot. I always dress so that I’ll be comfortable making a two-hour walk through the woods, and still alive after a night out there: in addition to a thermal base layer, extra socks, waterproof overpants, thick boots, hat, mitts, scarf, etc. I carry a solar blanket, and can also use my cowling cover as an insulated blanket. There’s a small hatchet (CAD 5.00 at Canadian Tire) for cutting firewood or smashing a window to get out of the plane, and a waterproof package full of matches, since my flint-striking and stick-spinning skills are…well, non existant. A big advantage of dressing that way is that I’m comfortably warm outside while preflighting the plane, except when I have to remove a mitten to check the fuel or oil. When I’m warm, I’m not tempted to rush the preflight even with a temperature of -25 or -30 degC and a wind whipping across the airport. Unfortunately, all those layers leave me feeling like a Malaria sufferer about 5 minutes after I enter a heated building, so I have the extra hassle of changing back and forth to remove the thermal underlayers.

Still, with all of that, I will be flying again for this, my third winter in the air, hopefully with the floor vent closed and the heater running nice and hot.

Following my 1:60 rules of thumb, here are some rules of thumb that apply to altitude. Some of these, like pressure altitude, are basic stuff from any ground school, but some are not well understood. Density altitude is especially useful, because it lets you forget about all the temperature-correction interpolations in the performance tables in your POH and just read the numbers you need directly.

Pressure Altitude

OK, if you don’t know this one, stop flying. The altimeter setting for the standard atmosphere is 29.92 inHg (inches of Mercury). For every inch below that, your pressure altitude goes up by 1,000 ft; for every inch above, your pressure altitude goes down by 1,000 ft. Of course, the easiest way to figure this one out is to temporarily change your altimeter to 29.92 inHg and read the pressure altitude directly, but the calculation isn’t really trick. For example, if your altitude is 2,000 ft and the altimeter setting is 29.40, the difference from standard is -0.52, so you have to add 520 feet to get your pressure altitude (PA) of 2,520 ft.

Standard Temperature at Altitude

Standard temperature at altitude, at least below the flight levels, is even easier than pressure altitude, and again, everyone knows this from ground school. At sea level, the standard temperature is 15 degC, and it decreases by 2 degC for every 1,000 ft. So the standard temperature for 5,000 ft is 5 degC, the standard temperature at 10,000 ft is -5 degC, and so on.

Density Altitude

Density altitude is the key to airplane performance. For example, whether you are at 8,000 ft with an altimeter setting of 31.00 inHg and an outside air temperature of -23 degC, or at 2,000 ft with an altimeter setting of 29.00 inHg and an outside air temperature of 19 degC, you are at the same density altitude — 4,000 ft — and will see the same cruise speeds, the same climb rate, the same fuel consumption, and the same takeoff and landing distances.

If you have been muttering about wasting your time with the first two examples, here’s a chance to put them into practice: density altitude is, roughly, just pressure altitude +/- 120 ft for every 1 degC difference from the standard temperature at that pressure altitude. So if the pressure altitude is 5,000 ft and the outside air temperature is 30 degC, the difference from standard temperature (5 degC) is 25, and 25 * 120 is 3,000: that means that your density altitude is about 8,000 ft: your plane will be flying (and burning fuel) as if it was at 8,000 ft, not 5,000 ft; if you’re on the ground in the mountains, your plane will also take off and climb as if it were at 8,000 ft, so you might want to wait until the sun goes down and things cool off a bit.

Density altitude is also interesting in the winter, because it can drop thousands of feet below sea level, allowing your engine to produce far more than its rated horsepower. It’s easy to get spoiled watching your climb rate improve by 50% and your takeoff roll shrink to a few seconds, but remember that you’re also burning a lot more gas than you’re used to unless you throttle back a bit.

Takeoff Distance and Density Altitude

I’m not entirely sure about this one, so check your own manual, but in all of the POH’s I’ve looked at, takeoff distance is linear with density altitude: however many feet you add to your sea-level takeoff distance for 1,000 ft DA, you add double that for 2,000 ft DA, and so on. For my Warrior II loaded all the way up to 2,440 lb, the POH says that I need 1,100 ft of runway at sea level, 1,400 ft at 1,000 ft DA, 1,700 ft at 2,000 ft DA, and so on, so my magic number is 300 ft for every 1,000 ft of density altitude (of course, I always leave a big safety margin, and don’t fly out of short fields at full weight anyway).

Line of Sight and VHF/UHF Reception

If your thumb can do square roots, you can use it (or your pocket calculator) for figure out approximate VHF/UHF reception distance at any altitude, assuming the signal is strong enough and there are no mountains or tall buildings in the way. To get the reception range in nautical miles, multiply 1.23 * your altitude above the transmitter in feet. So, if a VOR/DME transmitter is at 1,000 ft MSL and you’re flying at 9,000 ft MSL, you can expect to receive it at 1.23 * sqrt(8,000), or 110 nm away.

Since VHF and UHF both work on line-of-sight, this is actually the calculation for how far away you can see something in clear air before the curvature of the earth blocks it. So on a clear night, this might also give you a clue about how far away you can expect to see a city’s lights. At 3,000 ft AGL, you might be able to start seeing them when you’re 1.23 * sqrt(3,000), or 67 nm away (of course, you may make out the glow reflected from clouds above the city sooner). Sometimes the atmosphere plays tricks and bends light a bit around the horizon so that you can see things even further, but I don’t claim to know enough science to explain that; if someone who knows writes in, I’ll add an update.

The Lying Altimeter

Finally, there is the issue of altimeter error. Temperature affects the density of the air (remember density altitude), which affects the pressure gradient, so on a hot day, the altimeter will say that the plane is lower than it actually is, and on a cold day, the altimeter will say that the plane is higher. The formula is 4 feet for every 1 degC deviation from the standard for every 1,000 feet above the station reporting the altimeter setting.

So, let’s say that you take off from an airport at 2,000 ft MSL (with its altimeter setting) and climb to 12,000 ft MSL to cross a 11,000 ft mountain chain. If the outside temperature is -30 degC, what’s your real altitude when the altimeter reads 12,000 ft? Standard temperature at 12,000 ft is -9 degC, so the difference will be 4 * 21 or 84 feet for every thousand. Since you are 10,000 feet above the station, you will actually be about 840 ft lower than your altimeter says — you’ll fly across the 11,000 ft mountains at 11,160 ft, give-or-take.

The ADF radio, vintage 1940’s AM radio-direction-finding technology, inspires a lot of love and hate among pilots. Some pilots twitch violently when they remember the trauma of partial-panel NDB approaches during instrument training, some love the simplicity of the little needle that just points at an AM transmitter, and still others simply think of the ADF mainly as a convenient way to listen to sports games and talk radio from broadcast AM stations. I doubt that anyone reading this posting, though, loves ADF quite as much as the people who frequent Alex’s Longwave Page.

Yes, this is a fansite for NDBs. Really. And as of 21 October 2004, the counter was up over 15,000, so Alex is not clearly not alone in his love of the NDB. Longwave fans keep logs of the NDB stations they’ve received and identified the same way that plane spotters keep logs of tail numbers: Alex’s own log has nearly 800 entries in it, ranging from northern Canada to Cuba, and visitors have added hundreds more to the visitor log. There is also a section for unidentified NDBs, where other readers can write in with information.

Longwave transmissions can hug the earth and travel surprisingly far under the right conditions. If you still have an ADF on your plane, tuning in NDBs as you fly by them and watching the needle swing around is a good way to stay awake and provide a little extra situational awareness; after visiting this site, I might go a step further next time, and start tuning frequencies at random and trying to figure out (later, on the ground) what I’ve been receiving.

If anyone was still doubting whether the flying geek actually had replaced the flying doctor as the cliche of private aviation, well, doubt no longer.

I have complained to people that it’s hard to find good aviation blogs: they all seem to be rants about politics, hype about technology, or moaning about teenagers’ social lives. Fortunately, I have found one exception, Hamish Reid’s Yankee Alpha Foxtrot Bravo. [Update: Hamish does have an Atom feed.]

Hamish’s blog is very different from this one: it is personal and visual (including lots of pictures — Hamish is a photographer) where Land and Hold Short is general and text-heavy; it is about sunny California, while mine is about central Canada. Unfortunately, I cannot find any URL for an RSS or Atom feed. Hamish, if you’re reading this, please provide one, so that it’s easier to keep up to date on your entries.

Update: Hamish’s blog is available through an Atom feed at http://www.ylayali.com/yafb/atom.xml.

After reading my posting on the Rule of 60, Malcolm Teas kindly pointed me to a 1996 Usenet posting by Barry Silverman (originally written ten years ago, in October 1994) describing the French method of teaching pilot navigation. He also recommended a couple of books on mental math for pilots, for those of us who wear propeller beanies over our headsets — if you’ve read this far, you know you’re one of us.

The French method divides 60 by your true airspeed (there’s no escaping the number 60) to get a factor F, which you can use in mental calculations to estimate time enroute and wind correction angle without requiring an E6B or calculator: see the link to the original posting for details.

Malcolm also recommended two books for people who enjoy flying by numbers: Diversion Planning: How to Navigate Around the World with a Stopwatch and a Pencil (USD 8.95), written by a retired British RAF navigator named Martyn Smith, and Mental Math for Pilots (USD 27.95), written by Ronald D. McElroy, Pam Ryan, and Carol Core. To these, I’ll also add the Cross-Country Flying chapter of John S. Decker’s excellent (and free) online flying text, See How it Flies.

I recently ordered my first two CD-ROMs from John King and Martha King, who are very well known for their training down in the U.S.: Practical Risk Management for Pilots (USD 49.00) and Practical Risk Management for Weather (USD 49.00). Both require Windows (courses on Windows CD-ROM are sooooo 1980’s), but I won’t hold that against them. I have just finished working my way through both courses and printing out my certificates, and will share my opinions of both CD-ROMs (if you want to skip reading the rest, my conclusions are “definitely buy” and “don’t bother”). [Update: different opinion from Linda Pendleton on AvWeb.]

Practical Risk Management for Pilots

The first CD-ROM, Practical Risk Management for Pilots, is one of the best flying resources I’ve ever seen, and I tend to watch or read anything I can get my hands on. The production quality is clunky and the narrative and acting is downright horrible — to avoid embarrassment, I found myself working through the course mostly when no one else was home — but the content is very well though-out. The course is not about avoiding risk but about evaluating risk and deciding how much of it to take on; that’s the big difference between real risk management and the smug “what-an-idiot” accident-report analyses or trite sayings (”better to be on the ground wishing you were in the air…” or “a superior pilot uses his superior judgement…”) that usually masquerade as safety information for pilots, but actually do nothing to help us evaluate a flight and make decisions.

The Kings acknowledge that we have to accept a lot risk to fly at all — there is no such thing as a no-risk flight, and flying small planes is far more dangerous than driving — and their CD-ROM contains a series of videos, lessons, and exercises teaching us to analyze and classify risk the same way that we analyze the weather or our flight route. They sort the risks into categories, both pre-flight and in-flight, then offer the general rule of thumb that it’s OK to fly if the risks in only one category are marginal (i.e. if you’re just a little tired, but the weather’s excellent, the plane is good, and you’re under no pressure to complete the trip, then it’s probably still OK to fly). I like this kind of practical approach, and I’ve already started using it for my planning as icing season arrives here in Canada: learning how to manage risk systematically is like the difference between understanding weather reports and forecasts or just looking at the sky wondering if the weather’s going to be OK.

Practical Risk Management for Weather

I ordered both CD-ROMs at once, but even if I had not, after seeing how good the first one was I would have rushed out to buy the second one, Practical Risk Management for Weather. Unfortunately, this CD-ROM is an enormous disappointment. The vast majority of the material is rehashed from the first CD-ROM, including many of the same questions, scenarios, and videos. There are a handful of useful weather tips (i.e. choose an alternate along your route so that you can divert early; wind changes mean weather changes up ahead), but unlike risk management, this is common stuff available to pilots from many better sources: I think I remember that Richard Collins of Flying has a CD-ROM or DVD about weather. The only reason for buying this CD-ROM is that you’re a U.S. aircraft owner who insures with AVEMCO, because they’ll give you a 5% discount for completing the course. Those people should think of the second CD-ROM as a discount coupon; the rest of us shouldn’t bother.

Final Words

In the future, I expect much of the information in the first CD-ROM to become a standard part of every pilot’s training, so that analyzing risk systematically and properly is as important as calculating crosswind components or reading weather maps. That will be a good thing — perhaps the Kings’ biggest contribution to the aviation world — and it will more than make up for one bad CD-ROM. So I guess I don’t really begrudge them that extra USD 49.00.

Update: Linda Pendleton on AvWeb does not believe that King’s risk management courses are of much use, though she does not name them explicitly. She prefers what she calls “scenario-based training,” and also includes this little gem:

We take students to the practice area and drill them at length until they are able to do perfect turns around a point, s-turns along a road and lazy-eights. When was the last time a pilot was killed because the lazy eight was less than perfect?

I enjoy the numbers in flying. That’s not to say that I’m one of those people who try to calculate everything to five decimal places like the FAA and Transport Canada (unrealistically) require on their tests; rather, I like the kinds of numbers that you can actually play with in your head while you’re flying the plane: they keep you awake and improve your situational awareness, so they’re a win-win. I’ve been collecting these rules of thumb for a while, from many different sources, and one of my favourites is the 1:60 rule: one degree equals approximately one unit (foot, mile, whatever) sideways for every 60 units forward.

Distance to a navaid

On Canadian written flight exams, and I assume on those of other countries as well, the 1:60 rule usually appears in a cryptic and almost totally useless question about calculating the time to a VOR or an NDB. The 1:60 rule says that 10 degrees should account for a unit sideways for every six units forward (60/10), so however long it takes you to change your radial or inbound track by ten degrees, it will take you six times as long to get to the navaid. For example, imagine that you are tracking inbound on the 260 radial of a VOR (i.e. your track is about 80 degrees), you turn right to 170, and it takes five minutes before you intercept the 250 radial. That means that your approximate time to get to the VOR is 6 * 5, or 30 minutes in the unlikely event that there is little or no wind to mess up your calculation (but of course you just wasted 5 minutes finding that out, and if you are IFR, you have ATC screaming at you over the radio and rerouting traffic all over the sector to stay out of your way). Let’s be realistic: if you’re VFR, just look out the window; if you’re IFR, check the DME or GPS, or even just your time since the last checkpoint, or call ATC and ask where you are. The only time that this stunt might make sense would be if you were completely lost with no GPS, DME, or ATC radar coverage.

Calculating the crosswind

Fortunately, there are more useful things you can do with the 1:60 rule, including calculating the crosswind component: this trick works especially well if you have your track and groundspeed from either a VOR/DME or a GPS. First, divide your groundspeed by 60 (approximately) — that gives you the amount of crosswind represented by each degree of crosswind correction; next multiply that number by the difference between your track (GPS or VOR) and your actual compass heading, and you have the crosswind component in knots or miles per hour, as applicable. For example, if your groundspeed is 110 knots, then each degree accounts for 110/60 or just under 2 knots of crosswind. If you are tracking the 133 radial outbound and your heading is 141, then your crosswind correction is 8 degrees right and the crosswind at your altitude is a bit under 8 * 2 knots: let’s call it 15 knots.

If you’re really bored and want to keep your brain awake during a long flight, you can go on and estimate what direction the wind is coming from. To do that, start by figuring out your headwind or tailwind component by subtracting your groundspeed from your true airspeed or vice versa: for example, if your true airspeed is 125 knots and your groundspeed is 110 knots, then you have a 15 knot headwind component. If the headwind and crosswind (from the right) are both 15 knots, then the wind is blowing at about 45 degrees to your right — just trace your finger around 45 degrees on the heading indicator or VOR, and you’ll see where the wind is coming from (in this case, you can round it off to 180 degrees, or due south, so there’s a good chance that there’s a low pressure system directly to the east of you: the 1:60 rule is even useful for weather observation and forecasting, just like the ).

45 degrees is easy, because the cross wind and headwind are equal. It’s also easy to calculate when you have a pure headwind (the crosswind is 0 or very small) and a pure crosswind (the headwind is fairly small). At 30 degrees, the crosswind will be about 60% of the headwind; at 60 degrees, the headwind will be about 60% of the crosswind. So if the headwind were 6 and the crosswind were 11 from the right, you’d have the wind blowing from approximately 2 o’clock (there’s no need to be more accurate than that). Being able to perform this kind of calculation is especially useful during IFR training or an IFR flight test when you’re on your way to a VOR for a hold.

Climb and glide angle

Many light, fixed-gear planes like the Cherokee and Skyhawk glide at about 1:10 when fully loaded: they move forward ten units (feet, miles, etc.) for every unit they descend. Since 1:60 represents a single degree, 1:10 represents six degrees — that’s your glidepath. If you plane glided at 1:12, your glidepath would be about 5 degrees (60/12); if it glided at 1:6, your glidepath would be about 10 degrees (60/6). When you consider that a typical VASI/PAPI or glidescope is set up to bring you in on a slope of 3 degrees, you can see that you won’t have much chance of gliding to the runway if you lost the engine on final.

The 1:60 rule also gives you your climb angle, as long as you convert miles/hour to feet/minute first — one knot is just a bit over 100 fpm, so it’s an easy conversion. For example, if your plane climbs at 70 kt (~7,000 fpm), then your climb angle is 1 degree for every 117 fpm (7,000/60 — call it 120 fpm) that you can climb at that speed. If your climb rate is 640 fpm, then your angle of climb is a bit over 5 degrees (640/120). This calculation is easier to perform at home, with a calculator.

Navaid accuracy

The 1:60 rule is useful, if a little frightening, for figuring out navaid accuracy. In Canada, a VOR receiver has to be accurate within +/- 6 degrees, which, obviously, means 1:10. That means that if you are 50 nm from a VOR, you could be 5 nm (50/10) left or right of the airway with your receiver in tolerance; at 100 nm, you could be 10 nm left or right. Air traffic control is so used to GPS these days that they used to call me to check if I was two miles off an airway centreline halfway between two widely-spaced VORs — unfortunately, the equipment isn’t any more accurate than that. I’m just glad that I don’t have to rely on the VOR for flying through mountain passes.

Deliberate deviation

You can also use the 1:60 rule to change your heading deliberately to miss a target. For example, let’s say that you’re dead-reckoning from inland to a city on the coast. To make sure you don’t miss the city, you decide that you want to hit the coast 20 nm to the left of the city and then turn right and follow the coast in. How much should you change your heading if you’re 120 nm away? That’s 2 nm for every degree (120/60), or a course change 10 degrees to the left.

With cheap, portable GPS in almost every cockpit now, this stuff is not as important as it used to be, but it can still be a lot of fun, especially when you’re sitting in your chair on a bad day, wishing you could be up flying.

I woke up to the sad news that a Boeing 747 carrying cargo and seven crew members crashed and exploded during takeoff from Halifax this morning. The only positive note in all of this is that no one in the media is speculating about irresponsibly about terrorism, at least not yet — maybe we’re starting to emerge from the fear-and-paranoia culture that infected us after 11 September, 2001. On the other hand, the TWA 800 conspiracy kooks will no doubt be interested in another story of a 747 exploding. [Update 2004-10-15: the 747 had a double tail strike and tail separation on takeoff.]

I visited Halifax in my Warrior last summer. It is a big airport designed for overseas traffic, with an 8,800 ft runway (Cat II ILS) a 7,700 ft runway, and no high terrain or obstructions nearby.

The next day, there is confirmation that the 747 suffered a double tail strike, after which the tail split off.

My Warrior’s altimeter is probably the simplest instrument on the panel, really nothing more than a calibrated barometer. It doesn’t even tell me my real altitude — on a very warm or very cold day it can be off by a thousand feet or more. Still, when I sat down to think about it, I surprised myself by coming up with four uses for this piece of low-tech steam gadgetry beyond finding my current altitude, starting with weather forecasting (note: I make no guarantee that any of these is practical or reliable).

Weather Forecasting

Because the altimeter is a barometer, I can use it to forecast the weather in a clumsy way. With any barometer, when the mercury is falling, the weather is probably getting worse, since a low-pressure system is likely moving in; when the mercury is rising, the weather is probably getting better, since a high-pressure system is likely moving in.

So, let’s say that I land at a small, unattended airport for a leisurely lunch with a friend. Before I tie down the plane, I set the altimeter so that it shows the field elevation of 550 feet. Three hours later, I come back and the altimeter reads 750 feet — that means that the pressure has fallen by 1/5 of an inch of mercury in three hours (one inch of mercury is 1,000 feet), and the weather is going down. Where I live, in central Canada, the prevailing winds are from the west, so that’s probably where the low-pressure system is moving in from. That means that I can look up at the sky at the current weather, and then make a reasonable guess that if I fly west, towards the low, the weather will get worse than what I see right now, and if I fly east, away from the low, the weather will get better; north and south, of course, are anybody’s guess. If I came back after three hours and the altimeter read 1,550 feet, then the pressure is falling fast (one inch of mercury in three hours), and the weather change will probably be more severe.

The same thing works in the air — if the altimeter settings from airports along my route are getting lower, there’s a good chance that I’m flying towards worsening weather; if they’re getting higher, there’s a good chance I’m flying towards improving weather. In the air, that works moving north and south as well.

Detecting Inversions

The thermometer tells me the outside air temperature at my current altitude, but not the temperature of the air below me. However, I can use the altimeter to at least get a clue about what’s going on underneath if I compare its reading with the elevation displayed on a GPS (preferably one with WAAS). The altimeter is calibrated to show my altitude +/- 50 feet only when it has the correct altimeter setting and the air temperature is exactly 15 degrees Celsius at sea level and the temperature follows a standard lapse rate of 1.98 degC for every 1,000 ft up to my altitude.

On a cold winter day, the altimeter should show me much higher than I really am: for example, the altimeter might read 10,000 feet while the GPS shows me at 9,100 feet. On a hot summer day, the opposite is true: the altimeter might read 10,000 feet while the GPS shows me at 10,500 feet. When I don’t see the error I expect, that tells me that something unusual is going on beneath the plane — for example, if I’m at 10,000 feet indicated with an outside air temperature of -30 degC and the GPS shows that I actually am near 10,000 feet, I can take a fairly reasonable guess that I’m in cold air overrunning an inversion, and that things will get much warmer if I descend a bit (which could be bad in the winter, since I might end up in the ideal icing zone of 0 degC to -10 degC). Likewise, if my actual altitude isn’t above my indicated altitude on a hotter than average day, it’s a sign that there might be cooler air below me.

This is something I’d like to work on a bit. I’m still not sure how practical it would be in the cockpit.

Finding Vertical Air Currents

Glider pilots know all about using thermals and other vertical air currents to gain altitude. Unfortunately, those of us who fly underpowered planes also end up having to learn about these currents, since sometimes they’re the only way we can climb past 9,000 or 10,000 feet on a hot summer day in a fully-loaded plane. The vertical speed indicator lags a fair bit, so it’s not all that useful for finding rising air — by the time it shows a climb, I might already be past the air current. The altimeter, on the other hand, reacts almost instantly, and used together with the airspeed indicator, it tells me when I’m in rising air during a climb:

• If the altimeter needle starts moving faster and the indicated airspeed stays the same or increases, I’m in a column of rising air; often, I’ll slow down the plane below Vy to spend more time in the column. If the indicated airspeed is decreasing, then turbulence has probably just pitched the nose up.
• If the altimeter needle starts moving slower (or even falling) and the indicated airspeed stays the same or decreases, I’m in a column of falling air; often, I’ll speed up the plane well above Vy to spend less time in the column, even if it means levelling out or descending a bit. If the indicated airspeed is increasing, the turbulence has probably just pitched the nose down.

These will sound funny to people who fly behind big, powerful engines, but they matter a lot to someone dragging four people behind a 160 hp O-320. In level cruise, finding the currents is a bit simpler: assuming a constant power setting, if I have to push the yoke forward to keep the altimeter needle still, I’m in rising air, and if I have to pull the yoke backward, I’m in falling air.

Maintaining Attitude in IMC

Finally, the altimeter can help me maintain my attitude in IMC, especially in stratus cloud (where vertical currents are rare). Along with a rising airspeed, a falling altimeter needle is one of the first signs that the wings are not level — if the attitude indicator shows that I’m level and the engine is still producing the same power but the altimeter shows me descending from cruise or descending faster than expected in a planned descent, it’s time to cross-check the turn coordinator, vacuum gauge and compass to see if the attitude indicator is malfunctioning. This is especially useful during instrument approaches, when the altimeter is near the centre of the scan: it’s one of the first places I should be able to detect the beginning of a spiral.

In fact, in a severe partial panel situation (losing all gyros), the altimeter could be essential for maintaining attitude, though that kind of situation is very rare and very difficult to manage if it does happen.

If you are reading this feed in an RSS feed reader/amalgamator, please change the syndication URL to http://www.megginson.com/blogs/lahso.xml. The previous URL, lahso.rss, is not getting the right MIME type from my provider, and I haven’t made much progress getting them to fix the problem. Just about everyone will serve out a *.xml file as application/xml, and that should keep all of the amalgamators happy. Apologies for the trouble. The old *.rss file will stay available for a short while to give people time to change over.

I’m filling out an application to volunteer myself and my plane for Hope Air, a Canadian organization that flies sick people and family members (similar to Angel Flight in the US and British Columbia). The application process is about as complicated as applying for university, but I’m trying to find the patience to work my way through and add up my flying hours in all the different ways they want. One of the more interesting questions asks me to list all of the airports I’ve visited as pilot in command during the past 12-36 months. I’ve been flying as PIC for a bit over two years, so I decided to list all of them, divided up by province or state.

Ontario:

CYOW (Ottawa), CYSH (Smith’s Falls), CNP3 (Arnprior), CYRP (Carp), CYGK (Kingston), CYCC (Cornwall), CNL3 (Brockville), CNS8 (Morrisburg), CYPQ (Peterborough), CNC3 (Brampton), CYKF (Kitchener/Waterloo), CYRO (Ottawa/Rockcliffe), CYTA (Pembroke), CYYB (North Bay), CNT7 (Picton), CYAM (Sault Ste. Marie), CYTZ (Toronto/City Centre), CPD8 (Hawkesbury/Windover Field), CRL2 (Westport), CNS4 (Alexandria), CNW3 (Bancroft)

Quebec:

CYND (Gatineau), CYUL (Montreal/Dorval), CYMW (Maniwaki), CYMX (Montreal/Mirabel), CYQB (Quebec City), CYHU (St-Hubert), CYFJ (Mont Tremblant), CSD4 (Mont Laurier), CSE4 (Lachute), CYSG (St-Georges).

New Brunswick:

CYQM (Moncton), CYFC (Fredericton)

Nova Scotia:

CYPD (Port Hawkesbury, Cape Breton), CYHZ (Halifax)

New York

KMSS (Massena), KFRG (Farmingdale/Republic), KPLB (Plattsburgh/Clinton Co.), KART (Watertown), KITH (Ithaca)

New Jersey

KCDW (Caldwell)

Massachusetts

KOWD (Boston/Norwood)

The northernmost airport is Quebec, southernmost is Philadelphia, the westernmost is Sault Ste. Marie, and the easternmost is Port Hawkesbury on Cape Breton. All of these but two — Halifax and Port Hawkesbury — are within my Warrior’s non-stop range with good fuel reserves. Even Halifax would be doable non-stop with a good tailwind, though the return flight against the prevailing westerly winds would probably need a stop.

The only direction I haven’t gone far is north, and I’m hoping to make it up to Moosonee on James Bay within the next year or so.

There has been a lot of noise about the fact that two Yalies are running against each other in the U.S. presidential election, but people have paid less attention to the fact that two pilots are running against each-other. Their backgrounds are very different: President Bush flew military aircraft for a few years in the early 1970’s (and again, infamously, when he arrived on the U.S.S. Lincoln and spoke under the “Mission Accomplished” sign in May, 2003, though he was not pilot in command on that flight); Senator Kerry has flow general-aviation aircraft continuously since the 1960’s and holds a commercial pilot’s license and multi-engine IFR rating, among many others. One of the most interesting contrasts, however, comes with the two candidates’ aviation medical examinations. [Update 2004-10-24: corrected information on US medical requirements]

All pilots have to take special medical examinations regularly to keep our licenses valid. I renewed my own medical for my Canadian private pilot’s license a couple of weeks ago, and I barely passed: despite the fact that I’m only 39, run 25-35 km every week, lift weights, maintain a healthy body weight, and eat a textbook good diet, and have excellent eyesight and ECG readings, my blood pressure has always been borderline (even when I was younger), and this time I just squeaked through. Some pilots won’t take a medical if they think they won’t pass, preferring to ground themselves temporarily and (hopefully) solve the problem, rather than failing a medical and possibly grounding themselves for life.

Back in 1972, a younger and apparently healthier man, Lt. George W. Bush, skipped his own medical and grounded himself from flying in the Texas National Air Guard. The only two reasonable explanations are that Lt. Bush wanted an excuse to stop flying, or conversely, that he was afraid of failing the medical and losing his flying priviledges permanently. Now, 32 years later, President Bush’s opponents have had fun speculating that the young lieutenant might have been concealing drug use, but it’s also worth considering that he might have been concealing some more natural health problem, like heart murmers, high blood pressure, or blood sugar problems, that can and do affect otherwise young healthy men.

In contrast, Senator Kerry seems to go almost overboard on his medicals, as illustrated by his entry in the FAA airmen database (available at landings.com):

Name                : KERRY, JOHN FORBES
Airman's Address    : 19 LOUISBURG SQ
                       BOSTON, MA, 02108-1202
FAA Region          : New England
Date of Medical     : Dec, 2003
Class of Medical    : 2
Expiration          : Dec, 2004
Airman Certificates : Commercial Pilot
                         Airplane Single Engine Land
                         Airplane Single Engine Sea
                         Airplane Multiengine Land
                         Instrument Airplane
                         Glider Aero Tow (Private Pilot)

The two most interesting fields here are the date and class of the senator’s last medical. In December 2003, in the middle of a brutally-fought primary campaign (where he was not yet the front-runner) and constant travelling, Senator Kerry still took an afternoon off to visit a doctor and take his medical examination; not only that, but it was the class 2 medical for commercial (non-airline) pilots, which is tougher than the class 3 private-pilot medical I (21 years younger) barely passed. It would have been an easy matter to downgrade to a class 3 medical, which does not need to be renewed as often.

What does all this mean? It does tell us that, as a matter of public record, Senator Kerry is a very healthy man even under the stress of campaigning — that’s bad news, perhaps, for Senator Edwards and his personal supporters, and it may also explain why Senator Kerry seems so dull on TV (his abnormally healthy metabolism keeps him from getting pumped up?). It also shows that Senator Kerry is committed, almost to the point of fanaticism, to general aviation — I love to fly, but if I were in a national campaign and could take an afternoon off, I’d probably use it to rest, not to visit a doctor’s office to be poked, prodded, and wired up to an ECG machine. [Correction 2004-10-24: Rick Potts informed me that the U.S. does not require an EKG for a second- or third-class medical; he also mentioned that the second-class medical is not significantly more difficult than the third-class.]

And what about President Bush? He, too, seems to be a healthy man — I’m certain that he could run circles around me — but either he was never that committed to flying, or there is something that he is concealing in his medical history, such as recreational drug use (no big deal, especially if he gave it up decades ago) or some other, more persistent problem, like my own borderline high blood pressure. If it’s the latter, it is something that has been with him for over three decades, though obviously it does not prevent him from being active.

I plan to follow this up with a second pilot-vs-pilot posting on security, and then revert to aviation topics unrelated to American politics.

Welcome to Land and Hold Short, a weblog dedicated to light aircraft and general aviation. I’ll be writing both for other pilots and owners, and for aviation-curious members of the general public who’d like to escape their desks for a few minutes and come on up into the clouds.

About David Megginson

I am an instrument-rated private pilot with 350 hours in my logbook as of September 2004. That makes me a relative newbie, and certainly not someone in a position to start preaching to other pilots about how they should fly. I am also finishing my second year of aircraft ownership, flying a 1979 Piper Warrior II (a member of the Piper Cherokee PA-28 family). Fortunately, since I’m self-employed, I do get a chance to fly a lot, and I will include trip reports, airport reviews, and pictures among the postings.

Content before beauty

If this is not the ugliest weblog you’ve ever seen, then you have my pity: I cannot imagine what else you might have endured. My first goal is to get this weblog online and make it easy to update, using a homegrown hack of XSLT and make on a Linux box. I’m always going to concentrate on content before beauty, but I will try to find time to throw together a decent CSS stylesheet and make these pages a little easier to look at. Please bear with me.

Update (2004-10-18): I’ve started adding clumsy CSS styles.

About the title

The title of this weblog comes from the Land and Hold Short Operations (LAHSO) used at busy airports with intersecting runways: the control tower is allowed to use two runways at the same time as long as one of the pilots agrees to land and stop before reaching the intersection. Big jet airliners cannot usually accept these because they burn a lot of runway, so it’s the small planes — the subjects of this weblog — that usually land and hold short.

I plan to post new entries at least weekly, and more often when I have the chance.