I wouldn’t call a failure to recover control after your 16 year old son accidentally causes the autopilot to part-disconnect and then an almost 90 degree bank angle “bad autopilot use”.
The N186CB accident was a loss of control, probably in or while avoiding IMC. The aircraft probably was out of trim, which may or may not have been caused by the pilot overriding the autopilot.
This is different from, say, a pilot flying a stalling exercise with the autopilot engaged (good for building character and upper-body strength), or having the autopilot fly into a stall in VS mode (the dog was unharmed, apparently), where autopilot handling is the primary cause of the incident.
ValerioM, how do you get VNAV output onto your flight director? Which kind of AP do you have?
I wonder about the PA46 and it’s stall characteristics. I recall an accident not long ago near Geneva where one of those simply fell out of the sky in a spin as well as another one near Samedan which also came down in a spin. That wreckage (near Samedan) looked VERY similar to the one in the accident report. In a situation where you are faced with an unexpected severe pitch up, this might be important.
Certainly, the PA46 does not appear to be an airplane which can be flown by an average PPL. This guy seemed to have quite some experience on it, but probably not enough to react to something like this.
I appreciate the quality of the investigation report. There’s a lot of detail in it.
Mooney_Driver wrote:
Certainly, the PA46 does not appear to be an airplane which can be flown by an average PPL. This guy seemed to have quite some experience on it, but probably not enough to react to something like this.
I disagree. Its stall characteristics are normal and benign. Its main challenge in low level stuff is controlling speed and dealing with systems in which it would be no different than say a Cirrus or Bonanza. What can be different is because they are very capable aircraft some people may be launching in them in cirucmstances when they wouldn’t launch in a C182, and as a result they are getting themselves into trouble.
The more powerful and technically advanced an aircraft is, the easier it is for a pilot to get behind it. But I can assure you there is nothing intrinsic in the PA46 that makes it hard to fly, other than the bit between the seat and the yoke.
JasonC wrote:
But I can assure you there is nothing intrinsic in the PA46 that makes it hard to fly, other than the bit between the seat and the yoke.
I don’t know. I have not flown it myself, but there must be a reason why (almost) everywhere outside the U.S. a class rating was required for the Pa46. With EASA it is gone.
And regarding the possible out of trim condition: This is a piston single with a mass of less than two tons. Even if completely out of trim and with the addional force of a connected autoilot it can be handled without problems. The control forces will be unusually high but not beyond the capability of an average pilot. A B737 (which was quoted above as an example) configured for landing and trimmed for 130kt or so is totally different. Adding (too much) power with those underslung engines whilst retracting flaps and gear requires very strong control forces and quick reaction in comparison.
what_next wrote:
And regarding the possible out of trim condition: This is a piston single with a mass of less than two tons. Even if completely out of trim and with the addional force of a connected autoilot it can be handled without problems.
If there is enough time and space to do it I agree. I do remember one such incident myself when I in my very early days almost stalled a C150 with full 40° flaps when I put on go around power. The pitch up is massive. I expected it and that is why I was able to control it even as a student, even tough it scared the smelly stuff out of me. If he really flew just below the ceiling and got a massive pitch up moment when the AP disconnected, then the airplane reared up and he went IMC in maybe 2-3 seconds. We’ll never know how much it went ANU, it could be well beyond the scope of that little horizon. And then the reflex would be to trim down down, until it’s out of trim on the other end and then again and again. Two phugoids were enough and we know the end result, he stalled and came down in a spin.
Swiss Cheese. Low altitude, high speed, unexpected pitch input. That is how I read this report.
The 737 has a different problem but the outcome can be the same. Only it will do it in one single phugoid and can be lost if the crew looses the plot on trim early on. The difference is: none of them stalled fatally but were trimmed into an attitude which did not allow recovery. Both hit the ground with massive speed and negative pitch. In both cases, it was the unexpected reaction of the airplane and automatics which caught the crew. That is the parallel I am identifying.
Jason, thanks for your assessment. That is why I asked. I just notice that quite a few wrecks of the PA46 appear to look roughly the same after flat spin accidents which leads me to ask why they got into a flat spin in the first place.
I don’t know. I have not flown it myself, but there must be a reason why (almost) everywhere outside the U.S. a class rating was required for the Pa46. With EASA it is gone.
When you say nearly everywhere, you mean in Europe?
I agree it has a high accident rate. And a class rating may well be a good idea to help on systems and speed. Personally I think it almost needs a type rating to protect pilots from themselves. But I have 800 hours in it and the problem is the pilots. There are no strange handling issues or vices it is just a fast, pressurised FIKI single.
The report suggests that the pilot was able to overpower the AP because the clutches were set below spec. That bit I get.
The bit I don’t get is the suggestion that the AP was able to trim the aircraft a long way aft without him noticing.
The two ideas can’t co-exist.
If he was able to relatively easily overpower the AP then he would have also felt the worsening aft trim condition.
The idea that the AP goes off on a tangent and trims the plane a long way aft, while this not being obvious from the flight (because the AP is compensating by applying more and more down elevator), works only with clutches which are pretty stiff. Then the AP eventually disconnects (after the certification-mandated 16 seconds or whatever) and chucks the plane back at the pilot, way out of trim.
FWIW, I did try trimming my TB20 backwards while flying at 140kt, and the required yoke forward pressure became very uncomfortable way before I got anywhere near fully backwards. But then the TB20 has tons of elevator authority, evidenced by the virtual impossibility of loading it outside the envelope without exceeding MTOW.
The PA46 Type Rating is an old piece of history. I recall something years ago suggesting that a significant % of pilots got a frozen pitot (presumably because they forgot to turn on the heater), so they saw IAS dropping off, so they pitched down trying to maintain cruise speed (omitting the obvious thing which is to check pitch+power), went past Vne and broke it up aerodynamically.
Peter wrote:
FWIW, I did try trimming my TB20 backwards while flying at 140kt, and the required yoke forward pressure became very uncomfortable way before I got anywhere near fully backwards.
Exactly. And now, you would let go of the flight controls, what would happen? I think that is exactly where this pilot found himself.
If you press the yoke against the AP, it will try to trim against you. Out of that condition, if the AP releases, the airplane will be massively out of trim. Happens not only in the PA46, I remember a Chinese A310 which crashed because of exactly this mechanism, fighting the autopilot without realizing it.
