Originally Posted by RWA
http://www.youtube.com/watch?v=3OtcaFkpUpk
It shows that the pilot’s grip on the handles looks slightly odd – only the forefinger is actually hooked over the levers, the thumb and middle finger are gripping the sides of the levers.
The grip in this video looks like the pilot keeps ready for go-around, by keeping the thumb and middle finder behind the levers to be able to push them quickly and decisively all the way forward. Note that contrary to some general SOPs for landing, he does not select reverse at touchdown, but waits for the spoilers call instead.
Some pilots here have remarked that this is also their preferred way on short runways, because, although this carries a small LDR penalty, it keeps open the GA option in case something goes wrong.
I researched this a bit and found that there are in fact red buttons on the outside of each lever, which trigger ‘autothrust disconnect.’ That is presumably the reason for the odd grip, so that the pilot could disconnect the autothrust before flaring – even though he would have been planning to pull the levers back to ‘idle’ in any case.
You only need one button, most comfortably I guess pressed with the thumb. It is a bad idea to disconnect autothrust explicitly before pulling the levers to idle on landing, because thrust would then rise to meet the lever position. After pulling the levers to idle autothrust disconnects, but can be re-activated, but in either case, thrust would be limitied to the lever position, i. e. idle.
From information earlier in the thread, we all know that, with the A320 setup, autothrust disconnect does not automatically reduce engine thrust to ‘idle.’ If the throttles are above ‘idle’ the thrust merely ‘defaults’ to the last recorded thrust setting (which in this case was presumably the power required to maintain landing speed on final approach).
Careful here. There are four distinct ways autothrust can disconnect:
1/ by pulling the levers (both) to idle. This is the normal way during landing. Thrust is reduced to and stays at idle.
2/ by pressing the so-called "instinctive disconnect" pushbutton at the thrust lever side. Thrust rises to meet the lever position. Standard procedure when using this method is to first move the levers to match the actual thrust setting, but it is not technically necessasry.
3/ by pressing the A/THR pushbutton on the glareshield. Thrust is locked until the levers are moved, after which thrust meets lever position.
4/ by an internal failure condition. Thrust is locked until the levers are moved, after which thrust meets lever position.
(4/) was the most likely way in this accident.
So, as I see it, even if the wheels are down, the ONLY way to reduce thrust on a given engine to ‘idle,’ and keep it there, is to retard the lever all the way to the ‘idle’ stop?
Yes, the above notwithstanding.
Is it even barely possibly that the pilot at CGH didn’t know this, or didn’t recall the point under the pressures of landing on a short wet runway with only one operating reverser? And therefore, in his own mind, used the buttons to order ‘autothrust disconnect’
No. In that case, thrust would have risen to the lever position (maximum climb power, around EPR 1.28). And A/THR disconnection would have been recorded in the FDR graphs. Neither is there.
Bernd