Timothy wrote:
The Dunkeswell tragedy (family of four killed) appears at first glance to be loss of control in IMC (stall, incipient spin, out of the clouds into the ground) but seems to have been caused by the pilot being unable to cope with the complexity of the PA46’s autopilot, which may have put him in IMC in the first place.
My take was that the accident was caused by the fact that he’d flown an approach with the autopilot still active, meaning he was pushing the nose down to descend whilst the a/p was still active and trying to hold altitude hence it was actively trimming the plane nose up. Once he did disconnect the autopilot properly, he was handed over an aircraft which was suddenly trimmed full nose up; once he released pressure from the yoke, the aircraft climbed sharply and that put him into IMC, leading to spatial disorientation……
Strangely enough that is the same thesis about some other crashes, including 737s or similar – that the a/p hands you a plane which has been trimmed to such an extent, pilots have become spatially disoriented as the plane suddenly heads in a direction they weren’t expecting it, nor did they understand why……
@Steve6443, opinions vary as to the exact sequence, but my point is that he was flying an aircraft with systems more sophisticated than he could cope with, and the result was tragic.
Timothy wrote:
Similarly, all those stories of autopilots masking engine power loss, through being in VS rather than IAS mode, resulting in spins in IMC, typically in Bonanza.
Full agreement here. In fact, GA Autopilots are often more complex to handle and have much more inherent dangers to those who do not go through the trouble of understanding them fully, than current airliner AP’s. Which sometimes leads to the grotesque situation that an airline pilot used to his Airbus or Boeing DFGS will fail miserably running a simple S-TEC 55×.
Operations which are dead simple in an Airbus can involve up to 7 steps with a 55x, such as altitude change or getting it to follow a nav signal properly.
Most GA AP’s need quite a bit of training to use them properly. Most airliner AP’s are quite straightforward but of course also can catch you out, as the example of the A320 at Strassbourg showed, where instead of a flight path angle a VS was selected which flew the plane into the ground. But generally of course, airline pilots also fly much more and know their AP’s inside out, whereas most GA pilots need to rethink how to use it every time they fly.
Timothy wrote:
The other thing is that lots of power, whether in aircraft or cars, creates its own controllability problems (torque in the TBM and EFATO in the King Air.)
I used to fly twins and love them. But I would not in my current flying want to own one for the very fact that i would not have the necessary currency to deal with an EFATO or even one in cruise or worse descent or go around (which causes a lot of grief when people open up both throttles but only one responds). That requires constant training and vigilance.
And talking of torque, try a Lancair 4P… that particular airplane scared the living daylights out of me the only time I tried it. Take off involves very slow opening of the throttle as the airplane will not track straight on a runway with the engine at full power…. I shudder to think how that beast behaves in a go around from low speed.
Yes, complexity is a huge factor. If you consider that the original Malibu 310P proved too much for most pilots who flew it only when it came to engine management, it doesn’t bother thinking about pressurisation and other stuff which comes with it.
Steve6443 wrote:
Strangely enough that is the same thesis about some other crashes, including 737s or similar – that the a/p hands you a plane which has been trimmed to such an extent, pilots have become spatially disoriented as the plane suddenly heads in a direction they weren’t expecting it, nor did they understand why……
There was one such accident in Russia where a crew totally lost the plot in a 737-500 during a go around. The 737 has quite a pitch up movement due to the position of the engines. They opened the throttles manually without pressing the TOGA button, leaving the Flight Director in APP mode but thought they were flying a coupled go around. Eventually they found that they were not and followed the flight director (which still tried chasing the GS) straight into the ground.
Under normal circumstances, most AP’s will involve autotrim and actually never should hand over the plane out of trim. This can of course change if the mode you think it is in is different from the one it is actually in and, particularly, if you try to overpower the AP.
One bit I’ve really learnt while dealing with autoflight is that if the question “what is it doing now” rises it’s ugly head, I’ve already lost the plot to an extent where a situation can escalate very fast indeed. The standard procedure for this (disconnect the AP and get the airplane levelled out with wings level) will not always lead to something nice either as the AP may very well be doing something quite reasonable while the pilot is way behind the airplane and has no idea what really should be done next.
