Originally Posted by Chris Scott
At level-off (TGEN 321, or t -13 sec), the rad alt showed a height of 40 ft. At the same time, the pressure altitude was +869 ft, from which I calculate the pilots' altimeters (set to the QFE of 984 hPa) would have been indicating about 60 ft.
It's kind of annoying that the report leaves those calculations as an exercise to the reader (I used this
Pressure Altitude Calculator), but yes, it shows that the QFE value received from Habsheim must have been correct.
Capt Asseline may have planned to fly below 100ft all along. This was certainly not incompetence, because his height-keeping after level-off at t -13 (see my post to roulishollandais above) was remarkably accurate – whether you study the baro readings, or the heights recorded from the rad-alt. Although he did lose height, it amounted to no more than 10 ft on his baro-altimeter, and the same on the rad-alt. He has stated that he was using only his baro altimeter throughout, and claims that it must have been giving false readings, but – other than his own testimony – I’m not aware of any evidence to support that.
But Asseline seems honestly upset about the investigators not believing him ("Do they think that both of us are too stupid to read an altimeter?").
To reconcile the DFDR values with an indication of 100 ft on the captain's PFD, one could assume that the crew had erroneously entered a QFE value of 985.5. Now that seems totally unlikely. On the CVR, they repeat the correct value three times (and "cinq" and "quatre" don't even sound similar).
Asseline has another explanation, that the reference value for his altimeter must have shifted somehow, and he has indeed a hair-raising story to tell, where this happened to him on a flight from Paris to Geneva, and he ended up 1000 ft too low, almost (as in "too low, terrain") striking some mountains.
While I have some sympathy for this particular theory of his, it still leads back to the basic problem: the flight crew being unfamiliar with the airfield. Had they been aware that Habsheim control tower is not a good 100-ft-reference, and had they known about these trees that are just about as tall as the tower, it wouldn't have mattered if their altimeter reading was off by a lousy 40 ft.