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BA 747 crew commended for escaping near-stall on take-off

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UALRATT

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Jun 29, 2006
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http://www.flightglobal.com/article...nded-for-escaping-near-stall-on-take-off.html

South Africa's Civil Aviation Authority has praised the airmanship of British Airways Boeing 747-400 pilots who battled to prevent a low-altitude stall after the leading-edge slats unexpectedly retracted during lift-off from Johannesburg.
At 167kt on the take-off roll, fractionally below rotation speed, all the leading-edge slats inboard of the engines on each side automatically retracted, after receiving a spurious indication of thrust-reverser activation.
As the aircraft tried to climb out from Tambo International Airport, known for its 'hot and high' environment, the jet lost a "significant amount of lift", says the CAA, and the stick-shaker immediately engaged, warning of an approaching stall.
Instead of following the typical climb profile, the first officer - whose aerobatic experience meant he was familiar with buffet - controlled the aircraft through the stall warning and buffeting by executing a shallower climb, while the commander supported the manoeuvre by calling out heights above ground.
The slats stayed retracted for a total of 23s. They started to redeploy 7s after the jet became airborne - as the undercarriage was retracting, at a height of 56ft - and were fully extended 9s later. The stick-shaker, which had activated intermittently over a 15s interval, stopped as the airspeed rose to 186kt.
In its inquiry report into the 11 May 2009 incident, the CAA says the crew had "no notion" that the slats had retracted before rotation. There is no separate indication in the cockpit for leading-edge slat position.
"The flying crew should be commended for the professional way that they controlled the aircraft during a critical stage during take-off," it adds. "During [the incident] the flight-deck crew had no indication or understanding of what had caused the lack in performance of the aircraft."
After stabilising the 747's climb, the crew declared to air traffic control that they were experiencing problems with two engines and would be returning to the airport. The aircraft, which had been bound for London Heathrow with 265 passengers and 18 crew members, landed safely.
Investigators have concluded that, during the take-off roll, the slats retracted - as designed - in response to signals indicating deployment of thrust reversers on the two inboard Rolls-Royce RB211 engines. The right-hand reverser signal was triggered at 125kt and the left-hand at 160kt.
But neither reverser had been activated, and British Airways engineers examined the aircraft (G-BYGA) to trace the source of the false signals. The inquiry concluded that, although the reversers were stowed, their translating cowls were nevertheless seated relatively far rearwards.
As the 747's engines wound up to high power, and the aircraft accelerated, sensors monitoring the cowl positions transmitted incorrect 'reverser' signals. The slats retracted because of a logic process designed to prevent them being struck by efflux air from activated reversers.
Boeing subsequently developed a safety bulletin for Rolls-Royce-powered 747-400s to disable this reverser-based automated stowing.
 
Bet that was fairly high on the pucker factor! Great job!
 
16 seconds in that condition would probably seem like an eternity not knowing if you're going to be able to hold onto it long enough for it to fix itself, or even if it IS going to fix itself...

Nicely done!
 
Wait..

So we're supposed to REDUCE the pitch and INCREASE the airspeed???

That can't be right. They told me to pitch for shaker last CQ.
 
I can see in this scenario US airlines have the captain do the flying. I wonder what would've happened had he barked out "My Aircraft!" at a such low alt and a/s. It's a good thing he did not try to emulate Sully and did let his FO do the flying.
 
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I can see in this scenario US airlines have the captain do the flying. I wonder what would've happened had he barked out "My Aircraft!" at a such low alt and a/s. It's a good thing he did not try to emulate Sully and did let his FO do the flying.
Says who?

I have flown for 4 Part 135 carriers and 3 Part 121 carriers. Not a single one has EVER had the CA take the airplane at a low altitude. Engine failure, engine fire, stall recovery, anything.

AFTER the aircraft is STABILIZED, some airlines have the F/O fly while the CA troubleshoots the problem, while some have the PF direct the memory items and checklists, so *that* is different from airline to airline, but I've never seen a carrier with a standardized practice of taking the airplane with a problem right at or after V1.

Not sure what you're talking about here...
 
I can see in this scenario US airlines have the captain do the flying. I wonder what would've happened had he barked out "My Aircraft!" at a such low alt and a/s. It's a good thing he did not try to emulate Sully and did let his FO do the flying.

What airline has a "captain immediatley takes the a/c" in their procedures??
 
I can't imagine any Captain saying "I got it" and trying to transfer control of the aircraft in this situation when the F/O was obviously doing a great job. On the other hand, Sully would have looked like a fool if he didn't take control of the airplane given their circumstances. Finger pointing at Sully sure sounds like petty jealousy to me.
 
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