Boeing 737 flight spoilers

[stjohnsmythe]

On a recent pax flight on a 737 I noticed use of the flight spoilers when approaching to land.

Am I right in thinking that spoilers can be deployed at a higher airspeed than flaps?

Also, what benefit do the spoilers have vs flaps i.e. do they control descent rate or airspeed or both?

Thanks!

[BOAC]

No speed limit on 'spoilers'. Most opeartors ban use below 1000' however.

[Flexi]

Spoilers reduce the created lift of the airfoil significantly. You can therefore use them to reduce speed, achieve a higher rate of descent or even both!

The 737 has no speed limit for the use of flightspoilers. The faster you are the more effective they are!

When using the flaps, placard speeds exist for each flap setting stating the highest IAS for deploying. The also help reducing speed (but creating extra lift) but Mr. Boeing recommends not to use flaps as speedbrakes since the stress on the flaps is undesirable!

Hope that answers your question!

Cheers

[PPRuNeUser0190]

Most opeartors ban use below 1000' however.

FCOM limitation even (for NG I'm sure, no idea for classic) :)

[stjohnsmythe]

Thanks very much!

[singpilot]

Depends too if you were seeing them assymetrically deployed as roll augmentation when flaps down.

Was this an observation or a planned future comment to a fellow crewmember? Or both, haha?

[A37575]

When using the flaps, placard speeds exist for each flap setting stating the highest IAS for deploying. The also help reducing speed (but creating extra lift) but Mr. Boeing recommends not to use flaps as speedbrakes since the stress on the flaps is undesirable

I would hazard a guess and say most 737 operators pay lip service to the FCTM advice of "Normal descents are made in the clean configuration to pattern or instrument approach altitude...if greater descent rates are desired, extend the speed brakes."

While they may stay within flap airframe limit speeds (usually much higher than minimum manoeuvre speeds for the flap settings conccerned), there is evidence that pilots often cannot be bothered with excellence in flying, so they say it doesn't matter a stuff and go ahead and call for Flaps one through to Flaps Five while still descending and at speeds above the recommended.

[D O Guerrero]

That's a pretty damning statement! How would one achieve a CDA without selecting flap in the descent?

[BOAC]

DOG

1) You missed off "and at speeds above the recommended."
2) What difficulties do you have flying a 'clean' CDA?

[iflytb20]

The FCOM [NGs] say do not extend spoilers below 1000 AGL. The "SPEEDBRAKE EXTENDED" Amber light will illuminated below 800 AGL. Our company has an additional restriction which says do not use speedbrakes with Flaps more than 15.

D O G

As per our procedures, while doing a CDA or a decelerated approach, we use F5 till 2000 AGL and then select the gear. This gives a "near" idle thrust descent and normally spped stays within limits. If speed starts to increase, we simply select gear early.

hope it helps
cheers

[Rapid D]

Southwest has own limitation of no flaps at all with speedbrake usage. The party line is "Boeing engineers told us so" even though it's not in Boeing's manual. Any other self imposed restrictions out there besides the flaps 15 just mentioned?

[D O Guerrero]

BOAC - no difficulties thanks. I only select flap in accordance with my operators SOP.

[Port Strobe]

Our company has an additional restriction which says do not use speedbrakes with Flaps more than 15

Doesn't one get an amber light with speedbrakes extended with flaps greater than 10?

[Flexi]

With "our" 737 Classics, definitely no amber light with Speed Brake and Flaps >10° - no idea about the NGs!

Cheers :ok:

[alistomalibu]

Hi

"The 737 has no speed limit for the use of flightspoilers. The faster you are the more effective they are"

I found this reading an "Emergency descent" article for the 737NG
"Remember that use of speedbrakes at speeds in excess of 320 kts could result in a severe vibration which, in turn, could cause extreme damage to the horizontal stabilizer"

However 320 IAS is close to the VMO which is 340 IAS.

[Omykron]

The 737 has no speed limit for the use of flightspoilers. The faster you are the more effective they are!

I wouldn't say "more effective" when talking about 737 speed brake. I would say less ineffective.

I found this reading an "Emergency descent" article for the 737NG
"Remember that use of speedbrakes at speeds in excess of 320 kts could result in a severe vibration which, in turn, could cause extreme damage to the horizontal stabilizer"

However 320 IAS is close to the VMO which is 340 IAS.

the 738 has a speed brake load alleviator system, which on kicks in @ 300kias, reducing the speed brake lever and the flight spoiler deflection angle in 50%. (it can be override by the pilot).

[rubik101]

A3757 states: I would hazard a guess and say most 737 operators pay lip service to the FCTM advice of "Normal descents are made in the clean configuration to pattern or instrument approach altitude...if greater descent rates are desired, extend the speed brakes."

While they may stay within flap airframe limit speeds (usually much higher than minimum manoeuvre speeds for the flap settings conccerned), there is evidence that pilots often cannot be bothered with excellence in flying, so they say it doesn't matter a stuff and go ahead and call for Flaps one through to Flaps Five while still descending and at speeds above the recommended.

Would you care to elaborate? I know of no airline that does such as you suggest here is common practice. If you could quote your source for such a contentious and defamatory statement, I would be most grateful. If you are merely speculating, as seems the case, then please delete your rubbish post.

[B737-800W]

use of speedbrakes at speeds in excess of 320 kts could result in a severe vibration which, in turn, could cause extreme damage to the horizontal stabilizer


the above statement was in a an old FCOM version. In the new version there is no speed limit regarding the use of speedbrakes:ok:

[TheWanderer]

Controller: ABC1234 increase rate of decent
Pilot: unable
Controller: Don't you have speedbrakes?
Pilot: Yes, we do. But they are for my mistakes, not for yours...

[TheWanderer]

Try to avoid speedbrakes like the devil will avoid the holy water.

The 5 P rules: Proper Planning Prevents Poor Performance!

IMHO if speedbrakes are needed, then something has gone wrong in the previous part of the descent.
Speedbrakes produce drag and are uncomfortble to passengers. If you need speedbrakes, you burned to much fuel in cruise or level flight earlier -> start your descent earlier.

There are other options that are more comfortable to passengers than speedbrakes.

[BOAC]

IMHO if speedbrakes are needed, then something has gone wrong in the previous part of the descent. - well then, IYHO you have obviously never approached LGW 08R, or many other runways where unexpected short-cuts can leave you high - or are you one of those people who always decline the short-cut?

[iflytb20]

I found this reading an "Emergency descent" article for the 737NG
"Remember that use of speedbrakes at speeds in excess of 320 kts could result in a severe vibration which, in turn, could cause extreme damage to the horizontal stabilizer"The speed restriction was of 300kts on acfts without stiffened elevator tabs. The tabs have been stiffened since Sep 06 (SB-737-55A1080). Best way to tell - if the tabs have Six hinges, they have been stiffened. If they have four, they have not yet been stiffened

Doesn't one get an amber light with speedbrakes extended with flaps greater than 10? That is below 800 ft RA