Dash-8 incident out of Kingston

Posted on December 16, 2005 by David Megginson

This morning, I read a CBC story about a control problem on an Air Canada Jazz Dash-8 flying from Kingston to Toronto on 2 September 2004. From the story, it was pretty hard to figure out what had actually happened, especially given statements like these:

  • “It took the strength of two men to steady the control column of an Air Canada Jazz flight veering dangerously out of control” sounds like directional control problems — jammed aileron? asymmetric flaps?
  • “pilots struggling to gain control of the plane from the moment after takeoff” directional control?
  • “The control column, a stick used to manoeuvre and control altitude, was forcing the plane’s altitude higher as the craft continued to pick up speed” sounds like excessive up trim, but then why would the plane be picking up speed if the nose were up?
  • “loose nuts caused bolts in the plane’s elevator spring tab – a part of the aircraft that helps maintain control – to move out of place and throw the plane’s balance and control out of whack” OK, then it’s elevator trim

I didn’t feel much better informed after reading the article, so I hunted down the actual TSB report. It makes terrifying reading, not because of the trim-control problem (as troublesome as that was), but because of the risk of catastrophic structural failure.

As far as I can understand from a quick reading, the Dash-8 has elevators that can move separately on the left and right sides, and each has its own trim tab — the left and right trim tabs have to be balanced with weights so that one doesn’t pull more than the other. When the incident plane was in for painting a while before the accident, the tabs were rebalanced. The TSB’s best guess is that the AME left the bolts loose on one side in case the weight needed to be removed for more balancing, and forgot to tighten them afterwards.

Eventually, the weight fell off, leaving the tabs badly out of balance. As the Dash-8 accelerated for takeoff from Kingston, it sought to trim nose-high. The pilot flying (first officer) noticed that very little pressure was required to lift off, and soon both pilots were pushing forward hard to maintain airspeed, even with full nose-down trim. After running through some checklists, the captain disconnected the copilot-side trim (I think — this part is a bit hazy), and then was able to trim the plane for cruise using controls on his side. Althought they had declared an emergency 30 seconds after takeoff, they decided to continue to Toronto (about a half hour away) rather than landing at CFB Trenton between Kingston and Toronto.

I can understand their decision. After all, trim is mainly just a convenience for the pilots, to save us having to push or pull the yoke constantly during flight. On such a short flight, and with one of the independent trim systems (apparently) working, why not just continue the last distance into Toronto, rather than dumping up to 50 passengers on the tarmac of a military base in the middle of nowhere?

Unfortunately, things could have turned out very badly. Because of the weight imbalance, the two elevators were exerting different forces — one was trying to push the nose down, and one was trying to pull it up. According to the TSB report, this caused a twisting force on the vertical stabilizer close to its structural limit. That reminds me of the force that snapped the tail off American Airlines flight 587, though the cause was rudder oscillations, in that case. In hindsight, we know that that was the real danger of the flight and that the trim problem was only a sympton.

If the flight crew had known the real risks, I don’t doubt that they would have set down in Trenton without a second’s thought. In my own flying, I’ll try to keep in mind that any anomaly I can actually detect may just be the tip of a very large iceberg.

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Mind reading and ATC

Posted on December 15, 2005 by David Megginson

I’ll guess that 80% of my flying is done in continuous radio contact with ATC, either IFR, VFR in class B/C/D airspace, or VFR with flight following in class E/G airspace. This kind of flying has its own challenges, but one of the biggest ones is learning to read controllers’ minds (I’m sure that they’d tell you the same about dealing with pilots). If you can figure out what the controller is thinking — what her or his plan is to get you to the approach or the airport, why you’re being vectored, what traffic he or she is worried about, etc. — you can anticipate what’s going to happen next, and sometimes you can even help out a bit, especially if you can tell that the controller’s getting overwhelmed (again, just as controllers do with pilots).

Mind reading is also sometimes necessary, though, simply because of sloppy terminology. Here’s what happened to me yesterday — I was returning to Ottawa VFR, and a few miles from the airport, terminal control passed me to tower with a minimum altitude restriction of 2,000 feet still in force. Here, as far as I can remember, is what the tower controller said:

Tower: BJO, I’m going to have you follow the downwind for 25 first, then bring you around for the left downwind on 22 [my intended runway].

This is pretty normal when arriving at the airport from the southeast — they want to keep me out of the departure path of 25 and have me cross the middle of the jet runways at circuit altitude. But what about my altitude restriction? When you’re cleared to any leg of a circuit (in Canada, anyway), you are automatically cleared to descend to circuit altitude, but was I cleared for a downwind leg? I didn’t hear any clearance in the controller’s communication — feel free to leave a comment if you disagree — but my amazing powers of telepathy told me that because the tower controller used the word “downwind”, he thought he had cleared me; unfortunately, if I had acted on his assumption and ended up with a loss of separation with an IFR aircraft, the tapes would have shown me in the wrong. I decided to help things along a bit a couple of miles from the airport:

Me: Tower, BJO has an altitude restriction of 2,000 feet. Is it OK to descend to circuit altitude now?

Tower: Sure BJO, descend to 1,500 feet. For future reference, a clearance to downwind lets you descend to circuit altitude.

Yep, I read that one correctly — he thought he’d cleared me to downwind. I thanked him (no point wasting radio time on a long discussion), and counted myself lucky that he wasn’t wearing a foil hat to shield his brain waves.

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Training and false alarms

Posted on December 7, 2005 by David Megginson

The story goes (true or not) that 911 gets more than its share of calls about airplanes in distress over the practice area west of Ottawa. I don’t blame the people calling in — stall practice is (hopefully) too high to see details, but someone might still note the change in engine noise; a forced-landing practice down to 500 feet AGL, on the other hand, looks and sounds an awful lot like the emergency it’s trying to simulate, right down to engine-surging noises (advancing the throttle briefly every 500 feet) and the plane disappearing behind the trees for most viewers on the ground.

I think that might be what happened in New Brunswick yesterday. According to this CBC story, several people on the ground reported reported a low-flying aircraft with engine trouble, and, in this case, S&R took the reports seriously enough to dispatch a Hercules aircraft, a Comorant helicopter, and a Coast Guard cutter (!!) to investigate, possibly because local media had already picked up the story.

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LOP debate goes mainstream

Posted on December 6, 2005 by David Megginson

The lean-of-peak debate, which I’ve written about before, has just gone mainstream — check out this Forbes piece, part of a series of online articles about institutional stupidity. The focus is on Lycoming’s business practices (deny evidence that you cannot refute while insulting your customers in the process) rather than the technical fine points of LOP operation, but still, there it is, out of the pilot-geek closet.

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Cirrus owner's review (mixed)

Posted on December 3, 2005 by David Megginson

Back in July 2005 (updated in September), Philip Greenspun published a detailed owner’s review of his factory-new Cirrus SR20, the 200 hp (cheaper) sibling of the Cirrus SR22. Philip has flown his plane pretty seriously around a huge part of the continent (including the Canadian arctic), and has a long list of both the good and bad aspects of it. There are dozens of annoyances — large and small — that you’d never know about after reading a glossy magazine review written on the basis of a single test flight.

Philip also speculates about the actual safety value of the chute. In his opinion, most or all of the cases where people have pulled the chute and survived would have been survivable in a non-chute equipped Piper or Cessna, while in the cases where the chute really was necessary, it failed and resulted in a fatal accident. I don’t know how accurate this analysis is, but it’s an interesting perspective, especially coming from a Cirrus owner.

This page is highly-recommended reading, even if (like me) you cannot imagine ever being able to afford a factory-new plane. The 6-8 week, USD 10,000/year annuals — while still under warranty — are certainly an eye-opener. I wonder how much he’ll pay for maintenance when the plane is a little older and the warranty has expired. It sounds like a pretty nice plane, though, on balance, and I certainly wouldn’t turn one down.

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Canada/US descent below minima

Posted on November 30, 2005 by David Megginson

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.

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Ground support

Posted on November 29, 2005 by David Megginson

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.

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A low approach, and the lights

Posted on November 29, 2005 by David Megginson

[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.

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Surface temperature and the TAF

Posted on November 28, 2005 by David Megginson

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?

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Alfa, Bravo, Charlie, David …

Posted on November 18, 2005 by David Megginson

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.

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