757's speed brakes

[wingtip777]

someone says on 757, if you need to use speed brakes then use all of them. don't let the stick stay at the middle position, is that correct ? if it is, then what are the reasons? thanks!

[subscale]

Flew it for a number of years a little while ago, and heard the same said. As far as I could see it was an old wives tale as I always used the amount of airbrake I needed to lose the energy I needed to lose smoothly.
Is that cos I was taught to use judgement and airmanship which don't fit well into todays environment of over prescriptive procedure?

[Eff Oh]

If it was ever designed to be "all or nothing" it would have an on/off switch not a sliding lever. I have heard this said too and I utterly disagree. As subscale said, you should use aimanship to dictate speedbrake useage.
Eff Oh

[Right Way Up]

I do not know if this is relevant to the 757 but on the 737 full speedbrake is recommended, as high roll rates can occur when applying roll with intermediate speedbrake setting. Having seen it demonstrated on the aircraft I can see why it is recommended!

[Herp]

Right Way Up..

Not relevant I'm afraid. The Boeing 757 Flight Crew Training Manual says 'Use of sppedbrakes does not appreciably affect airplane roll response' with no caveat for partial deployment.

I haven't heard of any 'all or nothing' recommendation and have experienced no ill effects from partial deployment, which is my preferred method of use as it is more comfortable for all on board (assuming I've thought far enough ahead!).

[Right Way Up]

In that case maybe it is a case of ex 737 drivers bringing their old ideas across. Certainly on the 747-400 partial speedbrake was a much more pleasant way of operating the aircraft, and led to continous bollokings on my conversion to the 737 when I used partial speedbrake.

[lizard drinking]

For the comfort of the pax, any speedbrake causes vibration and noise, so it makes sense to use it all for a short period than a little for a longer time. The vibration is much the same with partial or full speedbrake. It does not do much until it is all the way out, and even then it is not much good, it is only a spoiler after all, and since it blows down at high speed and at low speed it has only a small effect, I always use all or none.

[Chris Higgins]

None of the above ladies/gentlemen:


As a former Flight Crew Training Instructor for a major US Airline and a representative instructor at the Longacres Facility in Washington, the answer is: Cali, Colombia!

That's right, we were taught to instill a sense of respect for the speed brake, where pilots should be alerted to partial use of speed brake for reasons that it adversely affects climb performance in a CFIT escape situation.

The AA Cali Accident scene would not have been had the crew not had speed brake deployment throughout the CFIT escape procedure. In fact the simulation shows that they would have missed the hill top by several hundred feet.

As an added precaution PLEASE leave your hand on the speed brake following deployment and do not remove it until it is safely stowed!!

[Boeing Freak]

would it not be easy to generate an EICAS message when thrust is applied with the speedbrake deployed?

[Chris Higgins]

Yes it would Boeing Freak, just as it would be to initiate a stow feature as a catch with thrust lever advancement, but this is 1983 technology we are speaking of....and millions for an STC to change it, and an admission of guilt in the liability lawsuits still pending over AA Cali.