737 ng speedbrake

[homerj]

Hi ,

the FCTM says that ' use of the speedbrake between the down detent and the flight detent can cause rapid roll rates and should normally be avoided'
so when using the speedbrake should it not be used at intermediate settings?

I used to use it just to before point where the light buffeting starts but a CP quoted this to me.
And is it possible to pull the lever past the flight detent in flight.
Sounds like a bit of a basic question from a Pro but ive seen all kinds of use of it.

Thanks

[Radar Love]

Hi,

Boeing say you shouldn't extend beyond the flight detent in flight. They don't say anything about stopping when you get to the buffet or not using intermediate 'brakes.

With no official company guidance except the Boeing manual, I take it to mean you can use how much you need, up to the flight detent.

If they say avoid going past the flight detent then perhaps it's possible, but I wouldn't try it!

[homerj]

yeh but as i said , the book says "use of the speedbrake between the down detent and the flight detent can cause rapid roll rates and should normally be avoided" , so the Skipper I was flying with took it to mean any setting in between should be avoided, which sounds in line with the book.

No training Cp has ever mentioned it to me , and ive seen experienced lads use it at various settings but does anyone know the correct procedure

[Radar Love]

Sorry, pretty tired and misread the question. You're quite right. Actually thinking back to my previous company they did train you to use the speedbrakes at the flight detent position or not at all.

[wileydog3]

Unless the NG speed brakes have changed, the Boeing recommendation is to use the boards up to the flight detent and use caution between down and that detent. The reason is with, for example, half boards, when turning you will wind up with one wing with LOTS of extension and one with the boards fully retracted thus creating a quick (for an airliner) roll rate. Not a big deal but something to be aware of.

[homerj]

That makes sense alright Wileydog, And is it possible to pull the lever past the flight detent in flight, i must try it in the sim but am not sure if its possible

[Flight Detent]

It IS possible...

and quite easy if you pull the lever quickly up from the detented down position...

Remember quite recently Boeing reset the FLIGHT DETENT position in the NGs to alleviate a wing loading potential problem with winglets fitted.
So the actual physical distance you need to pull to get to the limit (in flight) is less.

Cheers...FD...:)

[iflytb20]

Not ALL have a mechanical flight detent. In my company, 8 acft don't have mechanical stop, so it is possible to go beyond flight detent. This is mentioned in the FCOM Vol II as well. The remaining acft have a mechanical stop which prevents the speed brake lever being deployed beyond the flight detent.

Cheers

[despegue]

Show me an official Boeing document where Boeing advises against using the speedbrakes in an intermediate position... I have flown for a lot of companies, have thousands of hours on Classic and NG but NEVER, EVER have I seen, or flown with someone who doesn't use an intermediate position if needed.
What Boeing DOES recommend is something entirely different: It recommends to use caution, read: move SLOWLY, while moving the speedbrakes between idle- and flight-detent.

[Rapid D]

Sure about that despegue?

Here is a link to download your own copy of the Boeing FCTM.

4shared.com - document sharing - download 737 FCTM.pdf (http://www.4shared.com/file/53334690/b3ebce5e/737_FCTM.html)

Please read the "Speedbrakes" section beginning on page 4.20. Like has been stated, it says specifically, "Use of speedbrakes between the down detent and flight detent can result in rapid roll rates and normally should be avoided."

[Flaperon777]

Ok...homer
Here's what u should know.
YES the use of the boards between down n flt detents is NOT recommended as procedure per se.Most instructors(myself included) would not just discourage the use of intermediate positions,rather go a step further and ban it altogether.
Reasons are quite simple really.As someone mentioned earlier,yes...a) Assymmetrical deployment during turns with the boards in an intermediate position could dramatically increase the roll rates.Especially since the fact remains that speed brakes are most effective at higher speeds,therefore i am assuming that thats the flight regime in which you are using them.This higer airspeed would positively aggravate the roll rate. And then....b)The 737(classics and ng's unfortunately)have a peculiar design feature in rgds to their speed brakes.Which is NOT the case in almost every other aircraft that I have flown,744 & 777 included.When u deploy the boards in the air,the ONLY time the flight spoilers are in a locked position is when they are in flight detent AND in ground detent(i'll come to that later).Therefore in ANY other position they are suceptible to the now infamous flight contrlos 'flutter'.This combined with the eddies created over the boards in the high speed regime and further combined with the aerodynamic forces during a rate one turn at those speeds could really become quite a dangerous flight situation.Also,during manufacturer's testing in the early days,the drag values had only been calculated for the 2 'fixed' positions.Because in the other variable positions of the speedbrake handle,the exact angle of flt spoiler deployment was not known(or at least....it varied with different aircraft of same type).Thus the inability to calculate performance figures.Its either all or nothing with the ng speedbrakes.Not so however with more advanced airplanes with Fbw systems like the 777 for eg.Here you can and SHOULD use any and all intermediate positions depending on the drag required.AND they have done away with the 'flt' and 'ground' detents too! Of course that's just evoloution for you...http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif
The 'ground' detent CAN be used and WILL deploy the ground spoilers in the air too(if i remember correctly,a single failure could deploy the ground spoilers in the air if the handle IS in the ground detent).This higher drag value could be catastrophic.Especially in the high speed regime.
Buffeting of the wing during normal use of the speed brakes is a normal phenomenon.And should not limit the use of the boards.Provided of course u do not exceed the manufacturer's 'recommended' values.
Well...i tried to help.Hope i succeeded.
A very good question though.Controversial....at the least.

[homerj]

Thanks Flaperon , that sounds like the most confident explanation ive had regarding their use.
Its amazing how there is so much misunderstood ( and I include myself here) about such a basic and frequently used piece of kit.

[homerj]

Flaperon , If you have a minute could you take a look at my other thread regarding the FMC. Thanks

[despegue]

Well, I will have to re-evaluate my usage and teaching of the speedbrakes...I will ask collegues for their view. I can however
This proves that you never stop learning when flying...

[gimpgimp]

There is also sometimes confusion with the pointer on the sb lever.You know that little arrow on a sticker. That should line up with the white flight detent mark when the detent is felt. NOT the small metal bit that looks like a pointer but is an engagement thingy for the down detent indent.

[yrvld]

flaperon 777, thank you. :ok:

[plain-plane]

Someone more computer savy than me might be able to find an old thread that has pictures or links to pictures of a 737 with speed brake out at various stages with aileron deflection,,, I am quite sure I have seen them on here..

Boeing has a maintenance procedure that is required after speedbrake extended beyond flt detent in flight… I have seen a tec log ref to it a few weeks back anyway…

[de facto]

would flight controls flutter occur during wings level flight?
I grasp the idea of increased roll rate during turns as passed 10 deg of ailerons the spoiler on the inboard would be increased,becoming higher than the one on the upwing therefore increasing the roll rate..
However in the speedbrake mid position wings level,would it also cause rapid roll rates???flutter??:8 , what could cause such a spoilers assymetry in mid range position?(as they only have 2 'gated' settings?

[ampclamp]

There is a mech cable attached to the rh mlg squat that places a target over a prox sensor to allow gnd spoilers to operate when weight on wheels.
cant remember the full interface and other interlocks if any.Been a while.

[belowMDA]

I can't speak for the NG but I have seen the speed brakes extended to the UP detent in flight. I saw the captain pull the lever and thought that it was a lot rougher than normal, I looked down and sure enough saw the lever at UP. When I made a comment he didn't seem particularly fussed about it.

[ampclamp]

you can (in all 737 variants I have worked on ) pull the spd brk lever fully aft past the flt splr mark.None I am familiar with have a physical detent.
But you will only get flt splrs regardless of handle position.
You need (as per previous post) w on w (rh gear) and wheel spin up (60 knots I think it is and or reverse selected in certain conditions) to get the actual splr panels past the flt position.

So , from memory, you'd need a few failures to get gnd splrs in the air (never seen it thankfully)
You can physically select gnd splrs but it wont go there in a normal serviceable aircraft in flt.

[Swedish Steve]

You need (as per previous post) w on w (rh gear) and wheel spin up (60 knots I think it is and or reverse selected in certain conditions) to get the actual splr panels past the flt position.

I think you are getting confused between ground spoilers, and auto ground spoilers.
The ground spoilers are actuated when the spoiler lever is pulled to the ground spoiler posn, and the right MLG oleo is compressed. This compression moves a teleflex cable that opens the ground spoiler valve and ports hyd fluid to the ground spoilers. The ground spoilers will only move if this valve is open, and are only UP or DOWN.
Flight spoilers are always active, and can and will go to full travel in flight. On the B737 the flights spoilers are controlled by big mechanical devices in the wheel bay, The spoiler mixer, and the ratio changer. The spoiler mixer is a wonder of 60's design and extremely complicated inside.
Auto ground spoilers operate with aircraft on ground (same valve open) and wheel spin up. They will also operate with thrust reverse selection.

So if the teleflex cable failed in the ground position, you could get ground spoilers in flight, but only if you pull the spoiler handle back passed the flight posn. You would have other failures as well as the ground prox sensors are bolted on top of the ground spoiler selector valve, and controlled by the same cable. You can see this in the right wheel bay.
I have seen this happen. Very embarrassing as it was my mistake!

[ampclamp]

g'ay steve, yes I had it surrounded but not quite there.wheel spin up for auto splrs.But still need the vlv in the gnd position to get gnd splrs regardless
thanks for that.
some above were saying they have used gnd splrs in flt and or do select beyond the flt part of the quadrant.One day you day get what you select!