Originally Posted by
roulishollandais
Being particularly concerned in flying systems as a former manager of mathematics and computational methods, the comment of the expert Max Venet indicates to me a lack of computational methods. From memory, he said the following sentence: "We do not really know why the aircraft did not set in flare passing below thirty FT RA, or how long he should stay less than thirty feet. "
We've covered a lot of this ground before, and I believe you had a look at my old Prof's overview from his 1993 visit, where he saw use of advanced software engineering and reliability techniques in person.
Would this be the same Max Venet who was President of the SNPL from 1979 to 1982? If so, in which area of expertise was he qualified to comment?
This sentence shows that Venet did not found in Airbus a person who could tell him that or a document with this information.
No it doesn't, it shows that he didn't have the information - whether this was because he didn't try hard enough to get it or because Airbus were wary of supplying (at the time) very commercially-sensitive data to a representative of a hostile organisation is unknown.
The absence of such documents can only be accompanied by operational documents being incomplete and unsafe to the user (airlines, pilots, mechanics).
M. Venet stating that he didn't have those documents is not the same thing as those documents not existing. Again, we're back to Prof. Mellor's visit where he saw contemporary best practice in action.
I say that as a computer specialist who had to put up this kind of working methods among researchers and engineers.
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I do not see the point either to keep secret the software description. The fight against the copy is much easier to exercise if everyone puts their workon the table in daylight in a reasonable time.
And I respond as a professional software engineer and aviation nerd who had the good fortune to be educated by someone who saw behind the curtain.
These days it's clear to those with an interest that some of the techniques pioneered with the Airbus FBW systems have percolated down into more mainstream software practice (test-driven development and regression testing in particular). The kind of source-code sharing you describe has also become well-known, spawning the Open Source movement. However in 1988 the legalities surrounding software copyright and ownership were still something of a grey area, and the people dictating commercial policy guarded all aspects ferociously.
Getting back to the point, we've already discussed that Capt. Bechet organised an accurate real-world replication (minus the trees that were hit) of the flight at Toulouse. Flare mode was not activated, but Alpha Prot was.
Based on my understanding of how the systems were designed, it's likely the reason Flare Mode was not activated was because the brief RA reductions were not consistent with the overall trend of the values. M. Venet appears to have been working on the assumption that a value of 30ft RA will immediately trigger Flare Mode under all circumstances. This in turn suggests an overly simplistic understanding of software in general and indicates that his expertise was not in software, real-time or otherwise.
If Flare Mode had been (completely - h/t HN39) activated by overflying the copse, the DFDR would have indicated the elevators down shortly after crossing the strip threshold. Instead, the EFCS complied with the sidestick commands until shortly before impact, where Alpha Prot mediated the pitch-up demand to avoid stall.
And as rudderrudderrat said all the way back in post #45, Flare Mode can be overridden at any point:
Originally Posted by
rudderrudderrat
The baulked landing procedure (Select TOGA power and rotate to 10 degs pitch) allows you to fly away from any attempted landing - even after touch down.