Originally Posted by Owain Glyndwr
So far as 'phugoid damping' is concerned, the discussion has centred on the response in the last three or four seconds. The phugoid period at 118 kts is around 27 seconds - there is no way that phugoid motion is going to affect the issue.
No way? While I agree that the phugoid damping would not be sufficient to explain the apparently 'attenuated' response to the sidestick command, I'm not convinced that it could not have contributed to it.
As described in the Bilbao report " the EFCS behaves as a damper of the oscillations, commanding appropriate variations of angle of attack in a way that, when the aircraft is slowing down, makes it pitch downward and vice versa". In the last 5 seconds of the Habsheim flight, the airplane was decelerating at about 2 kt/sec. In the A340 airprox incident there was about 1 degree of alpha-prot bias between accelerating and decelerating parts of the trajectory for 2 kt/sec difference between acceleration and deceleration.