Land and Hold Short

I was discussing this approach with some U.S. pilots before I revised the numbers up — at the time, I remembered not seeing the runway until below 100 feet, though now I’m fairly certain I saw it at 130 feet.

I was taken aback when one of the U.S. pilots asked me if this was a confession. It turns out that the U.S. regulations for descending below DH or MDA are different from the Canadian regulations — in Canada, once we’ve seen the required visual reference (such as approach lights, or the PAPI), we’re OK to land — legally, if not safely — even if we don’t actually see the runway until the wheels touch it. See RAC 9.19.3 Landing Minima in the Canadian AIM for details.

The American regulations in FAR 91.175 have similar required visual references, but there is an important addition of a step-down altitude when you spot the approach lights first:

(3) Except for a Category II or Category III approach where any necessary visual reference requirements are specified by the Administrator, at least one of the following visual references for the intended runway is distinctly visible and identifiable to the pilot:
(i) The approach light system, except that the pilot may not descend below 100 feet above the touchdown zone elevation using the approach lights as a reference unless the red terminating bars or the red side row bars are also distinctly visible and identifiable.
[...]

That extra 100 foot restriction isn’t in the Canadian regulations. In fact, AN (SSALR) approach lighting doesn’t even have red side row bars, and the terminating bar is green.

Most commercial pilots, from the 747 captain to the freight dog and flight instructor, have something that most private pilots lack: ground support (did you think I was going to write something like “gumption”?). Today, the professionalism of a charity and the generosity of an airline gave me a taste of that.

The quality of the ground support can vary, from an airline’s huge dispatch operation and legions of ground crews to the aspiring instructor stuck behind the dispatch desk or working line at a flight school, but in all cases, there’s someone to call who can help out and provide support — to help with scheduling, find another plane if you’re stuck, maybe check the weather while you’re fueling, help push a plane, etc. We private pilots don’t usually have that — if you’re stuck in Kalamazoo with a bad piston (or a head cold), you’re stuck, period. If you’re lucky, the FBO will call you a cab to take you to a motel until you can sort things out and cash in enough of your retirement savings to get home.

Today, I had a chance to see what it was like having high-quality ground support during a volunteer Hope Air flight. I’ve already written about one part of my flight out to North Bay to pick up the patient and escort. By the time I got them back here to Ottawa for their early-afternoon appointment, I had already spent 4:30 in the air battling IMC, turbulence, heavy rain, and an 80-knot low-level jet from the south/southwest, all hand-flown (I don’t have an autopilot). When I started slurring words talking to the London FIC during the layover here in Ottawa, I realized that I was unsafe and grounded myself from the return trip (the rain and lowering freezing level at North Bay was also setting off alarms) — but now what? I had on my hands a father, son, and case worker who were planning to be home in North Bay for dinner. I thought about putting them on the bus (a long ride home), but then I decided to call Hope Air on the off chance that they could help.

Within 20 minutes, the problem was solved. Hope Air called Bearskin Airlines and managed to get three seats donated on the 4:30 pm flight back to North Bay (all the major airlines donate seats to Hope Air, but Bearskin was the most direct). Wow! It was an amazing feeling having ground support to watch my back and a generous airline to help out. Commercial pilots shouldn’t complain too much or take their ground support for granted.

[Update: after a night's rest, I've gone back to the approach plate to get the threshold elevation, and have tried to remember the exact reports I gave North Bay radio; as a result, I've revised all altitudes up a little.]

On her blog, Aviatrix has been running an interesting series on Canadian runway and approach lighting systems (here’s the first article). Approach lights figured big in my own flying today — after a long and difficult IMC flight, I had planned to take the LOC (BC)/DME 26 approach into North Bay Airport, since the ATIS was reporting a ceiling of about 1,000 feet. Toronto Centre talked to North Bay Radio and decided to vector me the long way around for the ILS 08 instead, because of fog near the end of 26. Then a PIREP (pilot report) came in reporting a 100 foot ceiling.

It took a long time to circle around over Lake Nippising and join the ILS — I had glimpses of the city of North Bay below me, but no airport ahead. At 400 500 ft AGL and almost at the field, I still saw nothing. At 250 or 350 feet AGL (I no longer remember) 430 feet AGL, I saw the approach lights cutting clearly through the fog, but no ground or runway. I knew that in theory it was legal to land seeing only a few approach lights, but it sounded terrifying, and I never imagined I’d try; however, it was actually a fairly simple thing to do, no harder than setting up for a runway, and certainly not stressful, at least not in a slow plane like a Warrior. I lined up with the lights (I’ll admit that they didn’t appear straight ahead of me, since I was drifting and bouncing a lot in the turbulence) and planned to touch down just a bit past them. Somewhere around 50-100 feet 130 feet AGL, just before I crossed the threshold, the runway suddenly popped in below me, and I made a normal (if slightly long) landing.

Aviatrix: they were AN — I don’t think you’ve covered that yet. It’s amazing how they can punch through the fog and let you make a legal (and fairly safe) landing when the ceiling is under just over 100 feet.

When you’re looking at the weather around a specific Canadian or U.S. airport, the METAR (current observations) includes surface temperature and dewpoint, while the TAF (forecast) does not. Why?

It’s true that pilots have to worry about more than just the surface temperature. We move in three dimensions, and need to know the forecast temperature thousands (or tens of thousands) of feet above the airport as well as on the ground — we get that from the FD (digital winds/temperatures aloft) forecast, as well as the freezing level in the FA/GFA (wide-area forecast). Any risk of temperature-dewpoint convergence (i.e. mist or fog) is already taken into account in the TAF.

Still, surface temperature has value. For example, it can tell me whether I’m likely to find frost on my wings when I arrive at the airport, and it can tell me whether the forecast includes an inversion (which might not show up in the FD if it’s low level). It also gives us a good indication of where forecasters expect local variations from the area forecast. The main proof that surface temperature forecasts are important is the fact that FSS briefers routinely look up the surface temperature from the general public forecast and read it to me (it has limited value, though, since it’s only the high and low, without time information).

It turns out that the international TAF format does include an optional surface temperature group that looks like this:

T17/20Z - forecast temperature of 17° C at 2000 UTC
T08/21Z - forecast temperature of 8° C at 2100 UTC
T00/18Z - forecast temperature of 0° C at 1800 UTC
TM10/07Z - forecast temperature of minus 10° C at 0700 UTC

(I took these examples from a U.S. web page, INTERNATIONAL TERMINOLOGY AND FORECAST GROUPS NOT USED IN NWS TERMINAL FORECASTS.)

Why not include temperature? Does anyone know the history of this one?

I flew home from Atlanta by airline this morning. I had been forced to cancel my plan to fly myself down early Monday because of severe mechanical turbulence around Ottawa up to 6,000 feet (confirmed by a PIREP from a Navajo).

Atlanta/Hartsfield, the world’s busiest airport (by passenger traffic), has five concourses designated A, B, C, D, and E, and a mini subway train connecting them. A recorded voice announces each stop:

The next stop will be concourse A, as in alfa.

The next stop will be concourse B, as in bravo.

The next stop will be concourse C, as in charlie.

The next stop will be concourse D, as in david.

The next stop will be concourse E, as in echo.

OK, back up a bit … why does every stop use standard radio phonetics except for D? I’d like to think that it was in honour of my birthday today, but it took me only a moment to think of a better explanation. Atlanta is the major hub for Delta Air Lines, so using the standard radio phonetic delta for the letter D would look like special treatment (though most pilots probably wouldn’t notice). It’s kind-of funny, but I do understand the problem, and appreciate the choice of an alternative — I hope that the Dans, Dorises, Denises, and Dougs of the world don’t mind.

During the flight, I started trying to think of other airlines whose names include radio phonetics. Canada once had Air Canada Tango and Québecair. Is there a Foxtrot Airlines, or Air Zulu? I imagine that no one would call an airline Charlie, since it’s U.S. military slang for the enemy (especially an enemy aircraft, at least in cheesy war movies), and could cause unfortunate misunderstandings.

I just read this TAF for Watertown International Airport (KART):

KART 	121738Z 121818 19008KT P6SM SKC
FM0600 17006KT P6SM SCT250 WS015/23035KT
FM1400 19012KT P6SM BKN250 WS015/23045KT

The tricky parts are the phrases “WS015/23035KT” and “WS015/23045KT” — those might be common out in the prairies, but I don’t see that kind of thing often in TAFs around the Great Lakes. The “WS” stands for “wind shear”. The following number is the altitude of the shear layer above ground level (1,500 feet in both cases), followed by the wind direction and speed at that altitude.

So starting at 06:00z tomorrow morning (that’s 01:00 EST), the wind will be from 170 degrees true at 6 knots on the ground, but from 230 degrees true at 35 knots just 1,500 feet up; from 14:00z (09:00 EST), the wind will be from 190 at 12 knots on the ground, but from 230 at 45 knots 1,500 feet up.

What does that mean, practically speaking? As you approach to land on runway 25 at 10:00 am local time tomorrow morning, you’ll be facing a headwind of 43 knots until 1,500 feet AGL, at which point the headwind will drop abruptly to about 8 knots — that means that your airspeed will suddenly drop by 35 knots as you descend through the shear layer, until your plane has time to reestablish its trimmed airspeed. If you’re approaching at 80 knots calibrated airspeed, you’ll suddenly find yourself at 45 knots with your nose swinging hard towards the ground trying to make up the missing speed (you’ll probably also be in moderate-to-severe turbulence). In a light aircraft, you may have room to recover at 1,500 feet; in something heavier, like a commuter turboprop, I’m not so sure.

When you take off from runway 25, exactly the opposite will happen. As you climb through the shear layer (and turbulence), your airspeed will suddenly increase by 35 knots, and the nose will shoot up to the sky to try to regain the plane’s trimmed airspeed. For a brief time, the climb rate will be spectacular, but you’ll have to make sure that you get the nose down before the extra speed decays on you and leaves you nose-high and slow.

The exact effect will depend on how thin the transition layer is and how fast the plane is descending or climbing. A slow descent or climb, or a thicker transition layer, will give more time for a gradual adjustment.

Anyone for some touch-and-goes at Watertown tomorrow?

Update: WordPress tells me that this is my 100th post. Whoopie!

Update 2: I went for another test flight on Friday, and the problem is fixed.

When you land after a flight, do you know — within a gallon/a few liters — how much fuel your plane should take? Some people always take off with full tanks and limit their legs to 2-3 hours, so they figure they never have to worry.

On Tuesday, I took my Warrior for its second post-maintenance test flight. I started with full tanks, flew for 2.75 hours at 75% power, then filled up again. The plane took 146 liters of fuel, over 50% more than expected, indicating that I landed with less than 45 minutes of fuel remaining. Upon closer investigation, there was some blue staining on the wing and a bit of streaking coming from under the left side of the cowling. My new fuel pump was leaking, throwing fuel overboard as I flew. I probably leaked fuel on my first flight as well, but since I didn’t start with full tanks, it was harder to be certain (I mentioned my concern to my AME then, but we saw no evidence of leaks inside the cowling).

I’m glad that I insisted on a second test flight before making the 800 nm trip to Atlanta, but I’m also glad that I routinely track my fuel consumption and know what to expect at the pump — it’s as important as being able to read the panel instruments during flight. Unlike a Cessna (with its “both” fuel setting), my Piper would have warned me of a problem when the first tank ran dry, giving me a few minutes to land with the remaining tank, but fortunately it didn’t come to that. A new fuel pump will arrive by courier tomorrow (Thursday) morning from the engine shop.

Anyone who’s planned a serious cross-country knows not to pay attention to any weather forecast until about 12 hours before the flight, not to take any forecast seriously until 2 hours before the flight, and not to rely on a forecast, ever. Nevertheless, we have to plan flights days or weeks in advance, and passengers want to know if we’ll be able to make a trip.

The regular, public forecasts have limited value for aviation. We need to know where the pressure systems and fronts will (supposedly) be, and what kind of moisture and winds we’ll be facing. The 48-hour U.S. prog charts (which also cover southern Canada) are a common stop, since they’re a lot easier for lay people to interpret than the Environment Canada GEM.

A 48-hour weather forecast is very likely to be completely wrong, but still, many pilots would like to torture themselves by looking even further ahead. For us, there is good (??) news: Unisys publishes U.S. (and southern Canadian) prog charts up to 5 days (yes, that’s 120 hours) ahead, not just for the surface but for higher altitudes like 700 mb (~10,000 feet) and 500 mb (~18,000 feet), with winds. So now you can agonize for five days about your flight — just don’t try to decide until two hours before, because the forecast will probably change.

The weather might be marginal somewhere along your route. You’re instrument rated, but you’re concerned that filing IFR will result in a much longer trip, or maybe you’re worried that you’ll hit ice at the required IFR altitudes. Assuming that you don’t cancel the trip (possibly the best choice), what do you do?

1. file IFR, because you can always cancel and finish VFR if the weather’s not IMC; or
2. file VFR, because you can always get a pop-up IFR clearance if the weather closes in.

I’ve seen both of these pieces of advice many times on aviation lists, and have sometimes heard them from other pilots, but I know from personal experience that they’re both wrong.

If you’re trapped under a lowering ceiling, you can’t always get a pop-up IFR clearance. First, you’re probably well below the minimum IFR altitude and have no way to climb VFR; even worse, you’re probably too low for ATC to see you on radar or even to hear your radio call. The only option is to cross your fingers and climb (illegally) through the cloud until you’re high enough to get into the system. That’s a scary option, especially near high terrain.

If you’re IFR, you might just as easily be trapped on top. Maybe there is a safe amount of VMC below you, but you have to have a way down to it before you cancel and continue VFR. Maybe you can shoot and approach and break off down low, depending on where you are, but it will frequently happen that once you start IFR, you find yourself effectively trapped in the system, maybe with ice-filled clouds below you.

So you can’t, always. As with much of flying, the pat answers aren’t that helpful, and pilots of small, piston planes are left with difficult choices that flight instructors (who rarely fly long cross-countries) and turbine pilots might not understand.

Today I took my Warrior for its first flight with the overhauled engine installed. I haven’t flown it since 13 July, and it was a nice feeling, despite high winds and a lot of low-level turbulence. I was supposed to test fly the plane last Monday, but there was still enough magnetism in the firewall (the one big part that didn’t get sent off for degaussing) to keep the magnetic compass from working.

You can read more about the lightning strike that grounded my plane in past postings.