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757 / 767 Speedbrake Safety?  
User currently offlineJoffie From Australia, joined Mar 2006, 806 posts, RR: 2
Posted (8 years 3 months 2 weeks 6 days 15 hours ago) and read 4033 times:

After watching the documentary on the American Airlines 757 which crashed into the mountains in Cali after the crew became confused, it was noted that one of the main causes of the crash was the First officer raising the speedbrakes, but forgetting to stow, or put them down.

My understanding is, airbus planes if the thrust is put to maximum, the speedbrake will automatically lower to prevent drag. On the 757 / 767 and possibly other boeing planes how come this does not happen? Wouldn't it be alot safer if the speedbrakes would lower if max thrust was applied?

I know there are hundreds of safe flights each day, and this is an extremly rare occurance.

thanks

11 replies: All unread, jump to last
 
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 1, posted (8 years 3 months 2 weeks 6 days 15 hours ago) and read 4023 times:
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Quoting Joffie (Thread starter):
Wouldn't it be alot safer if the speedbrakes would lower if max thrust was applied?

Haven't 757s and subsequent Boeings been modified to do just that?




2H4





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User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 2, posted (8 years 3 months 2 weeks 6 days 12 hours ago) and read 3976 times:

Haven't 757s and subsequent Boeings been modified to do just that?

Only if the aircraft is on the ground. Forty percent of travel from the idle stops will cause the ground spoilers to reteract. It's part of the function of GA.

All AAL B757s came from the factory that way.



"Eagles soar. But weasels never get sucked into jet intakes.."
User currently offlineOnetogo From United States of America, joined Feb 2006, 314 posts, RR: 0
Reply 3, posted (8 years 3 months 2 weeks 6 days 11 hours ago) and read 3962 times:

Quoting Joffie (Thread starter):
it was noted that one of the main causes of the crash was the First officer raising the speedbrakes, but forgetting to stow, or put them down.

This is a rather bold statement, especially considering the NTSB concluded that the plane would have impacted terrain regardless of whether the speedbrakes were extended or stowed. Recommend you read the full narrative report sir.


User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 4, posted (8 years 3 months 2 weeks 6 days 6 hours ago) and read 3911 times:

LINK
regds
MEL



Think of the brighter side!
User currently offlineSchooner From United Kingdom, joined Oct 2001, 139 posts, RR: 0
Reply 5, posted (8 years 3 months 2 weeks 6 days 5 hours ago) and read 3893 times:

SOP in my airline is to keep a hand on the speedbrakes whenever they are deployed in flight, the thinking being you are less likely to inadvertantly leave them up if your hand is resting on them!

Cheers.



Untouched and Alive
User currently offlineYYZYYT From Canada, joined Apr 2005, 947 posts, RR: 0
Reply 6, posted (8 years 3 months 2 weeks 5 days 23 hours ago) and read 3824 times:

Quoting Onetogo (Reply 3):
This is a rather bold statement, especially considering the NTSB concluded that the plane would have impacted terrain regardless of whether the speedbrakes were extended or stowed. Recommend you read the full narrative report sir.

hmm. I thought I remembered otherwise, so I re-read a portion of the NTSB report:

see bottom of p 50:

"Results of an initial study of the performance of AA965 following the GPWS warning indicates that if the flightcrew had retracted the speedbrakes second after initiating the escape maneuver, the airplane could have been climbing through a position that was 150 feet above the initial impact point. Therefore, because the airplane would have continued to climb and had the potential to increase its rate of climb, it may well have cleared the trees at the top of the ridge. The study also showed that if the speedbrakes had been retracted upon initiation of the escape maneuver and if the pitch attitude had been varied to perfectly maintain the stickshaker activation angle [35] the airplane could have been climbing through a position that was 300 feet above the initial impact point."

Though, Onetogo is not entirely wrong - the failure to retract the speedbrake was not listed as a cause at all, but rahter only as one of the contributing factors: see section 3.3, this is shown as a contributing factor:

"2. The flightcrew's execution of the GPWS escape maneuver while the speedbrakes remained deployed."

Interesting analysis of the issue, needless to say. Here is a link to the report:


http://www.rvs.uni-bielefeld.de/publ...s/DOCS/ComAndRep/Cali/calirep.html

[Edited 2006-04-13 18:29:01]

User currently offlineYYZYYT From Canada, joined Apr 2005, 947 posts, RR: 0
Reply 7, posted (8 years 3 months 2 weeks 5 days 23 hours ago) and read 3824 times:

Quoting Schooner (Reply 5):
SOP in my airline is to keep a hand on the speedbrakes whenever they are deployed in flight, the thinking being you are less likely to inadvertantly leave them up if your hand is resting on them!

report notes as well that Boeing recommends exactly this, but that AA did not include this in its own pilot manuals...


User currently offlineDH106 From United Kingdom, joined Jun 2005, 626 posts, RR: 1
Reply 8, posted (8 years 3 months 2 weeks 5 days 23 hours ago) and read 3812 times:

Quoting YYZYYT (Reply 6):
Though, Onetogo is not entirely wrong

Think I disagree - Onetogo seems to say the report implies impact was inevitable regardless of speedbrake position. The report says "it may well have cleared the trees at the top of the ridge" - although the report doesn't commit itself positivley, and the gist is that timely speedbrake retraction and rapid optimum escape maneuver was required, the report certainly doesn't imply impact was ineviable.



...I watched c-beams glitter in the dark near the Tanhauser Gate....
User currently offlineYYZYYT From Canada, joined Apr 2005, 947 posts, RR: 0
Reply 9, posted (8 years 3 months 2 weeks 5 days 22 hours ago) and read 3808 times:

Quoting DH106 (Reply 8):
Think I disagree

I know that - I was referring to Onetogo's challenge to this characterization...

Quoting Joffie (Thread starter):
one of the main causes of the crash was the First officer raising the speedbrakes, but forgetting to stow, or put them down

My point was simply that the truth (as usual) lies somewhere between the two...

And btw, I'm not taking a run at Joffie either... no matter how good these shows are they have to edit the content of hte NTSB report to make it interesting for the average viewer, and to fit the episode into 50 minutes...


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17001 posts, RR: 67
Reply 10, posted (8 years 3 months 2 weeks 5 days 18 hours ago) and read 3777 times:

Quoting Joffie (Thread starter):
My understanding is, airbus planes if the thrust is put to maximum, the speedbrake will automatically lower to prevent drag. On the 757 / 767 and possibly other boeing planes how come this does not happen? Wouldn't it be alot safer if the speedbrakes would lower if max thrust was applied?

For every person who sees this as an extra safety feature, you will find another person who thinks it is removing "authority" from the pilot.

In the end, if you don't follow procedure, you're doing something wrong and potentially dangerous, regardless of whether there is an extra safety net.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineJoffie From Australia, joined Mar 2006, 806 posts, RR: 2
Reply 11, posted (8 years 3 months 4 days 8 hours ago) and read 3449 times:

Some very information there.

I will sure check the official accident report shortly.

I have also read it is policy to keep your hand on the speedbrake lever when you are using them to slow down in some airlines.

If this is an AA policy, the policy was not followed.


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