"Phase advance"
'Morning Davita,
My memory is shaky but I think the standard practice was to switch on the ignition in severe turbulance at altitude. Didn't the F/E have those switches under a plastic lid in front of his thrust levers?
You're right, but IIRC that's a fairly common precaution on all jets. The stall prot on the VC10 (and probably the One-Eleven) came in the sequence of the three stages I mentioned, at ascending values of AoA. It's the "phase-advance" feature that we're particularly interested to understand on the current Airbuses. Just to remind you and maybe others: if the system detects a rapid rise in AoA, it can anticipate an imminent exceedance and trigger the relevant protection before the nominated AoA is reached.
This appears to have happened on an A340 on a NAT Track in 2001. First an overspeed tripped the autopilot. About 10 seconds later, a stall protection mode was activated, due to a severe but brief upgust which triggered it by "phase advance". In the absence of any stick movement by the crew, the system sought to maintain a safe level of AoA: the minimum AoA in the stall protection range. That resulted in a pitch-up, and the a/c entered a zoom-climb. Safe aerodynamically, if untidy, but there was another a/c above...
The only thing that event has in common with the VC10 is the phase-advanced triggering of stall protection. I've had stick-shaker several times on the One-Eleven at normal speeds in turbulence, and I think on the VC10 as well.
On the 'Ten, you'll remember, the most (only?) critical flight phase was the clean-up after take-off. IIRC, the acceleration had to be very steady to achieve a target of V2+60 by the time the slow retractions of flaps and slats were completed. When heavy, V2+60 was only a few knots below the flap limiting speed. Out of Entebbe and Nairobi for London, it was a common thing for the F/E to see and call the pre-stall ignition lights flickering on his panel (didn't have any female F/Es...). If you saw you were likely to exceed the flap-limiting speed, pulling-back on the yoke could (IIRC) in itself invoke the phase-advance stall detection.
That's what I'm asking you more-recent VC10 flyers to tell me about.
Last edited by Chris Scott; 13th Nov 2013 at 10:31.