HarryMan's heads-up to the AAIB Bulletin
Link on the EJ 737 Norwich incident is well worth reading for it's relevance to this thread:
- Not clearly defined or understood Test Schedules
- 1 "small" (in normal operation terms) Maintenance error/misunderstanding - surely to be expected and partly why the test flight is being carried out in the first place
- Misunderstanding / mishandling / unexpected events leading to a loss of control (again, a Flight Test Profile will be intolerant of such factors)
- Loss of control, which invariably in a swept wing high performance aircraft will lead to a significant loss of height
- Recovery actions do (eventually) work
Of course, one had a happy outcome, one did not... and being very broad brush... why? 1 crew actually performed their check at the specified altitude (~FL150), allowing time and space to recover... 1 did not.
Even a straight wing Jet Provost demands a minimum entry altitude of 15,000' for a 2-3 turn Spin.
So for all the ***** about FBW, we see a very similar sequence of events leading to a similar loss of significant altitude, in an aircraft about as far removed from FBW as we see flying today.
Lemurian - your use of Rudder post is potentially very relevant to the A320 accident. Large amounts of rudder were used, and are hardly going to help with low speed / "stalled" (Hi Alpha) aerodynamics. 15:45:15 sees Full Left Rudder (& Pedal, opposed by the Yaw Damper) at an IAS of ~100K or less... AoB might be 45R, but as your post again indicates, ignore AoB or whatever, you must recover from the "stall" before trying to recover from the attitude problems.
Overview - re-reading the Test Schedules in the Interim Report, it is clear that the "full back stick Min Speed on Alpha Max" should have seen a stable speed of 107K +/-3K. How did this crew, prepared (?) to do this test, and understanding (?) the principles behind it, and hazards associated with it (?), slow the aircraft to 92.5K
without asking "what's going on here"
AoA probes - interesting that in Airbus' Test Schedule, before doing any of this low speed stuff, their profile demands a
clean low speed check of all 3 AoA values... which seems rather relevant in this case with 2 AoA values seemingly "frozen" - which would have been revealed.
For the non Jet pilots here, just realise what seems to have been done. The crew, @3000', with Gear and Full Flap down, deliberately slowed the aircraft to 15K below the (equivalent) Minimum / Stall speed, and then applied Full Rudder (NB swept wing aircraft do not necessarily "stall" in a conventional sense, they just lose lift, develop a high RoD then "depart" which is a polite way of describing a flick into a potentially unrecoverable spin). Would you do that in a C150?
NoD