Originally Posted by Dozy
That's only partially true - you're looking at it from the assumption that Alpha Max has already been achieved
Because that's part of the alpha max demo and that's
where our discussion with OG initially started.
in which case the system will maintain it as speed continues to wash off, though eventually if airspeed is not sufficient to fly
Obviously you still didn't get what alpha max is ...
- you simply cannot "wash off speed" and "maintain alpha max" at the same time
- Airspeed is always sufficient to fly at alpha max
ground contact is a certainty (however as the Habsheim and Hudson incidents showed, the aircraft will "fly" right up until impact).
As a start, neither Habsheim or Hudson were at alpha max.
This is why, as OG correctly pointed out, Alpha Floor is an integral part of the combined systems protections - and why disabling it effectively transfers the responsibility for maintaining airspeed and thrust solely to the flight crew.
Alpha floor is an auto thrust function only and has nothing to do with maintaining speed for a flight crew.
The part you've now skipped over twice is how the EFCS works to *achieve* Alpha Max if it's not there already, and the rate at which it does so seems to be contingent on the mode (pitch normal vs. high AoA protection) and how the latter mode brings the phugoid damping aspect into the equation.
I have not skipped anything, but the BEA obviously has.
The US and Spanish teams have underlined the lack of pitch authority given to the pilots - They made some research and proposed possible explanations.
The BEA did ... nothing : "normal functioning of the aircraft"
It seems to be generally accepted that the TOGA thrust was applied too late
That part is a ALL chapter on its own as Asseline pretends TOGA was applied 4 seconds earlier than the BEA has concluded ... But we can keep that chapter for later as we have already enough to discuss on alpha max for now.
Originally Posted by Chris Scott
The essence of the accusation repeatedly made by CONF_iture is that the a/c failed to achieve alpha-max after the PF called for it.
Actually it is more specific : the elevator movements show that the FCS had no intention to deliver anything closer than 2.5 deg short of alpha max.
And the BEA has not provided any reason for such restriction.
But I mainly agree with the way you write the conclusion :
"That means that its IAS remained ABOVE Valpha-max until the treetops slowed it down. He argues, understandably, that the slight, residual surplus of speed above Valpha-max could have been traded more immediately for height."
Contributors who are expert in aerodynamic performance have explained that the refusal of the EFCS to respond immediately to the stick command was due to the lack of thrust, and the decaying IAS.
Then our "experts in aerodynamic performance" are in total contradiction with the BEA who conducted the simulated flight at the hands of Bechet.
The latter may have been exacerbated by a slight loss of headwind component at about t -2: that crucial moment when the N1s were still low, although spooling-up.
We need something more substantial than an hypothetical 2 kt wind shear to justify a drastic difference in the FCS response between the simulated flight and the Habsheim one.