Loss of height
Quote from vilas:
"In a non precision approach MDA all authorities insist on +50ft. because when you execute a GA you are expected to lose that much..."
You are not comparing apples with apples. Your instrument-approach analogy addresses a NPA of the modern variety, in which the descent fom the FAF (final approach fix), at the final approach speed, may be predicated on a steady approach angle in excess of 3 degrees to an MDA, at which point the G/A is initiated immediately (unless the descent can be continued visually). During the G/A, the a/c must not descend below the OCH (obstacle clearance height), so the chosen MDA may vary from type to type. The fly-past at Habsheim was not planned or briefed in that fashion.
Many years ago, the concept of MDA did not exist (as such). Even on precision approaaches like ILSs, the approach was flown to a CH ("critical height") or OCH, at which the a/c normally flew level until passing the threshold of the runway (usually assessed by stopwatch) unless the descent could be continued visually. Approaching the critical height, the pilot gently flared the a/c to fly level at it (but never below it - going below the CH/OCH on instruments was a fail-point on an Instrument-Rating test). In order to have a chance of "getting in" to the runway in marginal conditions of cloud ceiling and/or visibility, a large jet would have to fly the instrument descent from the FAF at a steeper angle than the average slope from FAF to threshold; in order to have manoeuvering space to level off, see the runway, and resume the descent. (In these days of reliable ground-speed information and - since 1983 on the A310 - the FPA "bird" - the concept of leveling off at the MDA/OCH/CH is no longer necessary on big jets.)
Quote:
"...and You are at Vapp at that point which is at least say 30 kts higher than alpha max. Then if you lost 100ft from alpha max is it surprising? this fly past was doomed even at 100ft because you will have no elevator left to effect flight path change. Some height loss had to be accepted."
No, that idea needs to be put to bed immediately. The PF would have planned to initiate a flare prior to reaching 100ft QFE or 100R. He was visual, and not constrained to descend steeply prior to levelling off. His descent below 100 ft was prolonged for nearly half a minute, and was therefore either deliberate, or due to sloppy flying.
If the PF was finding the prolonged application of back-stick physically difficult, he should have gone-around earlier. (Even if that was not the problem, he should have gone-around earlier...) The briefed fly-past at 100 ft, however that height was going to be assessed/defined, was a risky manoeuvre that led to an accident. As the whole game plan was voluntary, as well as plainly and irresponsibly risky, any excuses for its shoddy execution are incompatible with the essential concepts of command and responsibility. (End of sermon!)
Now, back to the minutiae of flight mechanics...
Last edited by Chris Scott; 18th Dec 2013 at 15:46.