I do think it’s more than just rapid accretion – in the TBM you need to select the inertial separator in icing conditions, otherwise the turbine can ingest ice. There was engine damage noted in the report, and the switch was found in the “off” position. So on top of what could have been fast accretion on the tail and wings, if you’re loosing engine power, you’ll turn into a brick fast enough.
The Garmin GFC 700 has a FLC (Flight Level Change) mode. This mode maintains your IAS and gives you a climb rate to a selected altitude that depends on your power setting. Meant to prevent you from getting into a stall. Would such a mode (airplane would stop climbing while still at climb power) have given the pilot a better clue that something was wrong?
For the Cirrus with FIKI installed/approved this is what the FIKI/TKS supplement states about the use of the autopilot: “Autopilot operation is prohibited when operating in icing conditions which are outside of the CFR defined conditions as stated in the preceding Environmental Conditions paragraph.” CFR relates to the continues flow rate setting. If it cannot cope with the ice (you need to use the boost setting for extra delivery of TKS fluid), then you cannot use the AP. Otherwise you can.
Yes, A/P usage is prohibited in these conditions. And it’s recipe for desaster anyway to use it, because the autopilot will retrim the plane without your knowledge until it’s too late. And with icing no speed based envelope protection of the DFC90 or DF700 kind could help you. These autopilots have no angle of attack probe.
A/P usage is prohibited in these conditions. And it’s recipe for desaster anyway to use it, because the autopilot will retrim the plane without your knowledge until it’s too late.
I think this may be putting it too strongly. Even with the autopilot set you should be monitoring what is going on. There is a fallacy that pervades this argument that you are either flying the plane or flying with the autopilot. Even with the autopilot on you should be vigilant and concentrating on what is happening.
I don’t think i exaggerated. The reason why A/P usage is prohibited by most POHs is that the A/P can retrim the plane until it is too late. See the accidents of Colgan Air and American Eagle. Imagine the A/P disconnects all of a sudden and the plane is completely out of trim. The accidents prove that it cannot be recovered in most of these cases. I think there is good reason for prohibiting A/P usage in icing conditions.
However – I think psychology is a big factor here.
To be icing up you are obviously in IMC, and the moment you disconnect the autopilot your workload is going to go up by an order of magnitude (no I am not a pilot forum “sky-god” 
and neither are 99% of pilots) so it is going to take a lot of balls to disconnect the AP when one sees ice building up.
My view is that one’s brainpower (what’s left of it) is far better utilised on leaving the AP engaged and monitoring everything that’s going on – airspeed, attitude and the operation of the de-ice equipment being the main ones.
A certified AP, that drives the pitch axis, is supposed to annunciate TRIM IN MOTION if the trim has been running continuously for (from memory) 9 seconds. If it has been running continuously for (from memory) 15 seconds, it is supposed to disconnect, with some other annunciation. Obviously the latter is a really bad scenario because it will throw a badly out of trim aircraft back to the pilot, but the pilot has had plenty of warning before that.
And anyway the AP is not going to be trimming away if the aircraft is flying at a normal speed and attitude. So the imminent disconnection is only the last stage in a series of warnings, which will include a big drop in IAS, a big increase in pitch attitude, and the TRIM IN MOTION warning. With a bit of luck, the stall warner should also go off because it is supposed to be heated so should not freeze up in the ice.
The above is based on my KFC225 (which has taken me to the edge of stall many times, when probing the operating ceiling at ISA+15 ) but I don’t see the KFC325 doing anything significantly different.
Please read this:
http://www.ntsb.gov/doclib/speeches/weener/weener_020111.pdf
The use of autopilots in icing conditions is PROHIBITED (!) by POH in many airplanes for good reason, i think.
Yes – I understand and agree; what I was getting at is that it is going to take solid steel balls to disconnect the AP in IMC.
I am not sure i have them… (i mean I do, but not sure if they’re made of steel :-)) that’s why i like flying to Croatia and Greece
