Quote from HN39, in reply to CONF_iture:
"I'm disappointed that you still don't seem to grasp a point I made more than once (see f.e. my post #520 on page 26)
When flying at alphamax, thrust controls altitude through speed:
Increase thrust - speed goes up - lift goes up - airplane goes up
Decrease thrust - speed goes down - lift goes down - airplane goes down"
You're not the only one to be disappointed! In fact, for the benefit of new readers, you had earlier made the point on
page 24. It was picked up by others including myself, although the vertical component of thrust at high pitch-attitudes may assist the pilot somewhat.
The co-pilot, without any previous experience of the task, had been briefed to take control of the throttle levers if and when Capt Asseline found the task too onerous. Commenting on the knife-edge accuracy of control required by the co-ordinated efforts of the two pilots to maintain (even) the briefed height of 100 ft at alpha-max, I then wrote:
"Clearly, low flight at alpha-max is hazardous, for at least one reason: wind-shear, which is inevitable over and near trees and buildings, unless the wind at all levels is flat-calm (a rare event). Any loss of headwind or increase of tailwind leads to a loss of IAS. Recovery of IAS requires an increase in GS, i.e., kinetic energy. With no surplus of potential energy to convert, that increase in kinetic can only be supplied by an increase in thrust."
So was there any windshear on the day? A few days ago,
I wrote:
Starting from level-off at TGEN 321 [t -13] and finishing with TGEN 334, the estimated W/Cs at one-second intervals are as follows:
-7, -4, -8, -9, -7, -7, -6, -4, -6, -5, -7, -7, -3, -3.
(TGEN 334 represents t -zero, the approximate second at which the a/c reached the treeline)
The Karsenty video shows a tall balloon on the west side of the airfield leaning slightly to the south, suggesting a light headwind for the accident a/c. The above wind-components are based on the usual comparison of the IAS-derived TAS, and the inertial ground-speeds (GSs). Any errors in the recorded GSs are likely to be consistent, but the IAS may have suffered increasing position-error in the last few seconds at higher AoAs.
The free-air W/C seems to be between -5 and -9. As the a/c CG was roughly the same height as the approaching treetops, it is likely that the loss of headwind component indicated in the above figures is genuine, and due to slight windshear in the lee of the trees.
Between TGENs 332 and 333 (t -2 and t -1), the recorded IAS drops by 4 kt (116 to 112), although there is no change in AoA, pitch, or GS. That would suggest a loss of wing-lift of the order of 7%, partly offset by the increasing vertical component of thrust as the N1 increased? (There may also be a slight reduction in HS downforce as the elevators unload slightly, one at a time.)