A lot of people have asked about the ice detection/protection systems on the Q. This is a great ice handling plane. I've seen a little over an inch on the unprotected surfaces with no detriment to speed or controllability. Lightly loaded as it was, the Q has an incredible amount of extra power. Below 8,000feet we cruise at 245KIAS at only 44-47% torque. Where they were on the approach, they were between 150-180 kts at about 25-33% torque. They would have had flaps 5 and gear down as they approached the marker.
According to the NTSB, the ice system was selected on and picking up ice, so their ref speeds would have been quite high. As they approached the marker (KLUMP), they would have called for "Flaps 15, before landing checklist." Below 171kts, the non-flying pilot (Bekki) would have moved the flaps through 10 degrees to the 15 degree mark. The Q tends to balloon a lot when flaps are extended, as the flaps on this plane are very large. According to the NTSB, this is where things started to go wrong.
The CVR recorded 2 hours worth of data, to include the crew brief of the ILS approach, weather, and discussion of significant ice build up on windshield and wings. They discussed airframe deice and verified as on. The flight director shows severe pitch and roll after the flaps went to 15. The crew attempted to raise gear and flaps just before the end of the recording.
The Q has bleed air supplied pneumatic boots on the wing leading edges, engine inlets, verticle, and horizontal stabs. It also has electric boots on the props. The pneumatic boots operate in six cycles of six second inflations, followed by either 44 seconds or 144 seconds of dwell time between cycles (fast vs. slow mode). The boots have to be turned on manually, but then will continue to operate on their own until the pilot shuts them off. There is also an option for manually operating one of the six boot segments individually, though that is rarely used. The heat for all three pitot tubes is on at all times from the after-start to the after-landing checklists. The front windows are heated electrically, as is the CA's side window. We also have defrost blowers that feed off the cockpit heat system through piccalo tubes at the base of all the windows.
As far as detecting ice: we can see about 1/4 of the prop and outboard along the wing leading edge from there. There is a very bright inspection light mounted in the outboard side of the engine nacelle that shines along the wing leading edge. The tail is not visible from the flight deck. There is an "ice detection probe" mounted on the windshield wiper. The wipers are stowed in a horizontal position, so the probe (a 1 inch tall, solid plastic cylendar mounted to the top of the wipers) sticks up just below the pilots' field of view. There is a light mounted to the top of the glareshield that shines through the windscreen to illuminate the probe. Each pilot has a push button switch next to their knee to turn the light on. Ice usually accretes here before anywhere else.
There is also an electronic ice detection system. There is a 4-5 inch long, 1.5inch diameter metal probe sticking out of both sides of the fuselage just below the pitot tubes. They vibrate at approx 40,000hz any time AC power is applied to the aircraft. When ice accretes on these probes, their vibration is slowed, and small heaters in the probe are automatically turned on. Once the vibrators return to normal the heat is turned off. If the vibration slows again, the system displays a yellow [ICE DETECTED] message on the Engine Displace (center of our five screens). Memory items when this is displayed are to turn the airframe deice system on, windshields to warmup (then on), and Ref Speeds to Increase (raises the calculated stall speed for the horn/pusher/shaker by 20kts - there is no stall vane/stall probe on the Q, it's all done by the computer). The [ICE DETECTED] message remains displayed until the probes no longer detect ice or the weight on wheels switch is made. The computer handles the rest.
If this was, indeed a tail stall, it would have been very difficul to detect. The Q's elevator is purly hydraulic with an artificial feel system for the control column. Control forces are normally heavier than most airplanes if you're more than very slightly out of trim. They likely wouldn't have had much if any tactile warning of building ice or an impending stall with the nature of the hydraulics on the elevator. I think it would have probably presented like an uncomanded stick pusher activation.
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