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Spoilers/speed Brakes Question?

Posted: Mon May 31, 2004 2:38 pm
by soaringadi
I know this sounds dumb.... but since I have never noticed it, neither know about it I'm gonna ask this question.....

Do the pilots ever use the spoilers during the descent, or on final approach ???

hope u guys can help me....

thanx  Smile

RE: Spoilers/speed Brakes Question?

Posted: Mon May 31, 2004 3:51 pm
by modesto2
Spoilers are often used on the descent to reduce speed and/or increase vertical speed. I have never seen pilots use them on final approach. At this phase of flight, they shouldn't be necessay. The aircraft should be established on the approach and the gear and flaps should create enough drag. Significant speed reduction can be accomplished with thrust reduction.

RE: Spoilers/speed Brakes Question?

Posted: Mon May 31, 2004 4:40 pm
by dl757md
There are several threads already in tech ops about spoilers.
I agree with Modesto2 about spoiler usage by the pilots. You will see the spoilers work in concert with the ailerons during final approach on most commercial planes. This is automatic and is not initiated by the pilots as a spoiler command but rather as a roll command through the control column or sidestick.

RE: Spoilers/speed Brakes Question?

Posted: Mon May 31, 2004 6:56 pm
by QantasA332
Adequate speed reduction isn't the only consideration underlying why spoilers aren't usually used (for their both-up speedbrake function) on finals/short finals; stall speed also comes into play. Put simply, spoilers reduce the maximum coefficient of lift (Clmax) of the wing, directly increasing stall speed (Vs). It's usually desireable to have the lowest possible Vs when landing (flaps obviously help with this by increasing the wing's Clmax), meaning spoilers aren't deployed (i.e. they aren't both deployed for speedbrake 'mode', as I said before). In addition to increasing Vs, spoilers obviously slow the aircraft. This can lead to another possible problem as Vs goes up and the aircraft's speed goes down, with the chance of the two passing each other if you're not careful.

Having said all that, I suggest you check out the thread(s) DI757md mentioned, where you'll find that I just repeated everything I said before Embarrassment, and some other good info as well.

Cheers,
QantasA332

[Edited 2004-05-31 12:02:10]

RE: Spoilers/speed Brakes Question?

Posted: Mon May 31, 2004 11:20 pm
by CX Flyboy
There are no restrictions on using the spoilers in the 777 at any stage of the flight, and that includes flaps 30 and gear down. As mentionned, this would be a very unusual time to use it, but sometimes, spoilers are neccessary even on approach. ATC can sometimes ask for a higher speed to be maintained than we would normally choose, and in order to lower the next stage of flap, the spoilers might have to be used.

Some airports have high crossing heights on approach and also high ATC speed requirements. Different aircraft have different operating techniques and in the 747-400 we used to put gear and flaps out early and use the drag to slow us down, but in the 777 we use the spoilers to slow us down to a more appropriate speed before configuring.

RE: Spoilers/speed Brakes Question?

Posted: Tue Jun 08, 2004 4:50 pm
by barney captain
Easy Cx flyboy. That is the very technique we have used at SWA for over 30 years only to discover flap spindle failures on approach that, according to the Boeing test pilots that recreated them were, "unrecoverable". Fortunately, our outcome was better, but please, believe it or not, the Boeing guys never test the wing or it's components for a flap/speed brake configuration. They indicate that it's not a condition one would normally encounter. You and I know better....

RE: Spoilers/speed Brakes Question?

Posted: Wed Jun 09, 2004 5:12 am
by Aaron747
That's astonishing considering spoiler panels and flaps are both wing structures that are exposed to specific and pronounced stresses as aerodynamic components - I'd have just assumed that Boeing would have tested them in all configurations. Frankly, that's rather surprising.

RE: Spoilers/speed Brakes Question?

Posted: Wed Jun 09, 2004 7:15 am
by Rick767
"They indicate that it's not a condition one would normally encounter."

Not my experience of approaching 5 years on the Boeings... flaps and spoiler together is a common requirement (especially so on the 757) to get it to "go down and slow down". My previous airline for example preached speedbrake usage on the 757/767 (up to Flap 20 settings) as "whatever it takes" to get it back on the profile.

Have done it (or had to do it!) countless times...

RE: Spoilers/speed Brakes Question?

Posted: Wed Jun 09, 2004 5:36 pm
by nudelhirsch
I have seen that before, but it is getting noisy, and also pilots here said it creates vibrations, so some pilots generally try to avoid using them, only if they are descending to rapidly and gain too much speed they are used.

RE: Spoilers/speed Brakes Question?

Posted: Wed Jun 09, 2004 6:17 pm
by 411A
Repeated for those that did not notice my previous comments about older jet aircraft...'What's the big deal about jets?'

Newer types are a pleasure to fly, very responsive.
Older types however, are a different kettle of fish altogether (speaking B707-321, JT4 powered here...).
Take for example...descent.
At 110 miles, close the throttles.
Duh, that was not a good idea, the Flight Engineer is having a fit because he cannot maintain pressurisation...as he grabs the inboard throttles and pushes them smartly up, to ensure turbocompressor spool-up.
So, down we go...now at thirty miles and still at 15,000, hmmm, lets grab a handful of spoilers. Ohhh, that was not a good idea, now the aircraft is shaking so much that you cannot read the instruments.
A better idea would be to split the spoilers (inboards OFF), ahhh, that works better, except now both you and the co-pilot have to push smartly forward on the column, to keep the nose from pitching up (way UP)...opps, started the stab trim too late, now the jackscrew is stalled.
Now, slightly low on the glide, a fistfull of throttles (why does it take so LONG for spool-up, opps, forgot, non-fan engines).
Gusty winds on final, no problem, the yaw damper will take care of this...NOT.
It had to be switched OFF at 1000agl, leaving you to arm wrestle the pig to the ground.

The handling qualities of the early heavy jet transports was very poor...new guys, on modern types, have it EASY.

RE: Spoilers/speed Brakes Question?

Posted: Thu Jun 10, 2004 1:09 am
by MD11Engineer
The MD-11 has an interlock, which prevents the use of speedbrakes after flaps have been deployed. Theoreticaly it is possible to set the flaps AFTER the speedbrakes are up, but acc. to one of our pilots it is not advisable because the plane turns into something like a brick or a piano.

Jan

RE: Spoilers/speed Brakes Question?

Posted: Mon Jun 14, 2004 6:23 am
by barney captain
Rick;

""They indicate that it's not a condition one would normally encounter."

Not my experience of approaching 5 years on the Boeings... flaps and spoiler together is a common requirement (especially so on the 757) to get it to "go down and slow down". My previous airline for example preached speedbrake usage on the 757/767 (up to Flap 20 settings) as "whatever it takes" to get it back on the profile.

Have done it (or had to do it!) countless times... "


Exactly my friend.....that's why I included this after my statement....

"You and I know better...."  Smile




RE: Spoilers/speed Brakes Question?

Posted: Tue Jun 15, 2004 5:58 am
by tangoecho
On the descent in a RyanAir 737-200 full deployment of the spoiler/speedbrakes was used for a good 10 mins, which I thought was a bit strange.  Wow!

RE: Spoilers/speed Brakes Question?

Posted: Tue Jun 15, 2004 4:46 pm
by nudelhirsch
Probably depends on thick air traffic apts...

Not seen it in HAM, STR, ARN, CPH, BNA, and so, but F R A ....wow, on a LH 744...

Think, if steep descend and still slowing down is necessesary then better go for it...

RE: Spoilers/speed Brakes Question?

Posted: Tue Jun 22, 2004 11:21 pm
by Corsair2
Mechanical interlocks on the 717 prevent the speedbrake handles movement after Flaps 8.

On a ValuJet DC-9 flight back around 1996, the spoilers deployed prior to landing due to a series of malfunctions with the older protection system.