Originally Posted by
BRDuBois
To counter the right wing down command, the rudder needs to move the nose left. In level flight this will roll the sim Electra over.
I've said that the problem was they were already in a bank when the problem was noticed. Below the speed at which a plane can do knife-edge flying, for any given speed there is some bank angle which is the maximum bank that the rudder can counter. The rudder needs to move the nose left, which in a bank has a vertical component. The sim tells me at about 160 knots the maximum right bank is near 60 degrees, meaning beyond that angle the rudder can't lift/left the nose. At that angle the plane can fly indefinitely. And when near that angle the rudder's authority is severely degraded.
I think they were calling for left rudder and the plane was balanced, if you will, near the peak of that curve. A little higher bank and the rudder would have lost all effect, they would have gone down much faster; a little lower and they would have recovered no problem. They were in the flatter part of the response curve, and it took some time for the nose to lift. Once it started to lift, like rolling down a slope, it gained speed. So I think they were rolling fairly quickly left when the right wing hit the embankment.
It wasn't an issue of bad design, in my [nonpilot] opinion, but bad luck that they didn't know of the problem until they were too far into the zone where the rudder authority is degraded. We've discussed this here previously, and I'm including it in my next release.
You will have noticed I make the case for the aircraft rolling left at embankment Impact?
“It wasn't an issue of bad design, in my [nonpilot] opinion, but bad luck that they didn't know of the problem until they were too far into the zone where the rudder authority is degraded. We've discussed this here previously, and I'm including it in my next release.”
I also feel comfortable to state they knew of the problem before they broke ground. The “turn” was way too early, the climb was almost flat, and they were committed to take off before a decision could be made to abort. The right turn was “noticed” by witnesses at eight thousand feet along, and 100 feet AGL.
The ailerons could have been jammed whilst taxiing to the runway, ailerons have no authority until 70 knots, so any notice of Roll would not have been sussed as aileron induced, likely Rudder was used to keep the centerline. Any roll prior to 200 AGL would have been countered by left input, the pilot would notice instantly no response in Roll, takeoff is accepted, and the rest is a litany of problem solving and trial. They tried to roll left before the aircraft broke ground, IMO. The steady state of Right Roll suggests that some left roll was available; with acceleration, the roll rate should have accelerated also with constant deflection, so aileron deflection was reducing as the flight progressed.
Any mention of aileron trim set at impact?