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OmniAtlas

Air France Flight 447: 'Damn it, we’re going to crash’

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I was watching a documentary on NetFlix on AF447 which was made prior to finding the Black Boxes, and one of the things they suspected was that the pilots may not have realized the throttle positions of the engines, because unlike Boeings Airbus Throttles don't move with the A/T. So they may have not been aware of the power setting causing the plane to lose or gain speed to a stall. They claim that the safe window between a safe airspeed and a stall at FL360 is 10kts in either direction. (That's something that definitely is not modeled in FS or X-Plane!) I know higher up near it's service ceiling the window is closer, but at FL360 I would think there is a little more gap.


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Tom

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Although AF447 was not technically in a deep stall in the classically understood sense of 'its elevators being blanked off from airflow by the disturbed air coming off the wings', it was undoubtedly in a deep stall in terms of the angle of attack combined with its forward speed, i.e. 35 degrees AoA @ 107 knots.

 

At least one good result of this silly dispute between two talented posters (one of them a non-native english speaker, which might help understand his poor choice of words) is that everyone following this thread looked up the true meaning of "deep stall".

 

Al, whether the plane was - or wasn't - in a "pretty deep" stall is a moot point. The hard - and heartbreaking - fact (among many other heartbreaking facts that took place that night) seems to be that the plane was recoverable and that none of the crew mentioned the word "stall" (or applied corrective action against it long enough) until it was too late.

 

I was watching a documentary on NetFlix on AF447 which was made prior to finding the Black Boxes, and one of the things they suspected was that the pilots may not have realized the throttle positions of the engines, because unlike Boeings Airbus Throttles don't move with the A/T.

 

Tom. While the plane can switch automatically to TOGA mode with the throttle in the normal CL flight detent under certain conditions (cf ALPHA FLOOR/TOGA LK, etc.), the throttle can also be moved manually to the TOGA detent and this is apparently what happened if you read the BEA report.

 

Bruno

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The term "Deep stall" has to be applied here because of the combination of high angle of attack, high incidence, and low airspeed plus the enormous rate of descent. When you think the rate of descent works out to be around 124mph(statute miles that is!!) or 107knts it would take a long time and a lot of air for the aircraft to be recovered fully. Had they discovered half way down "Oops we've stalled the a/c" they may still have hit the ocean because they were falling out of the sky so fast. I feel very sorry for the passengers who must have all been terrified out of their wits.

vololiberista


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Homework? There is no direct connection between stick position and stall warning sounding.

 

No but there was a connection between the AoA and the flight computer concluding whether the IAS values were valid or not, which in turn controlled when the stall warning sounded. So as far as I'm aware and in very simple terms what the PF was experiencing was pull back = no stall warning (IAS not valid because of AoA), nose down = stall warning (IAS valid due to lower AoA). I can only imagine how confusing this would be given everything else occurring and potentially being totally spatially disoriented in the middle of the pitch black Atlantic at night when you're not certain your PFD is displaying correct attitude information.

 

PS, the only type rating I hold is for an MX5 ;)

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No but there was a connection between the AoA and the flight computer concluding whether the IAS values were valid or not, which in turn controlled when the stall warning sounded. So as far as I'm aware and in very simple terms what the PF was experiencing was pull back = no stall warning (IAS not valid because of AoA), nose down = stall warning (IAS valid due to lower AoA). I can only imagine how confusing this would be given everything else occurring and potentially being totally spatially disoriented in the middle of the pitch black Atlantic at night when you're not certain your PFD is displaying correct attitude information.

 

PS, the only type rating I hold is for an MX5 ;)

 

As I said

 

....while the stall warning was sounding continuously between about 02:10;40 and 02:11;45 the First Officer took the aircraft from an AoA of 6 deg 30 deg to about 25 deg, and the flight path angle of of about 0 deg to about 25 deg nose-down by applying generally nose-up stick movements over that time period.


Gerry Howard

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Yeah but blindly saying:

 

Buried in the depths of the article are the words "...pull back on the control stick. He left it there despite the stall warning that blared out some 75 times." It's hard;y surprising that the aircraft eventually crashed with handling like like that.

 

Kind of implies a lack of understanding.

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Yeah but blindly saying:

 

 

 

Kind of implies a lack of understanding.

 

On who's part? The FDR traces confirm that's what the FO did.


Gerry Howard

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The author of that original quote you took and you as well to a certain extent; I haven't questioned what he did, have I? He was just reacting to a range of stimulus, one of which was implying nose down = stall warning, nose up = no stall warning.

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