Ground Spoilers in B737NG
Join Date: Mar 2001
Location: I wouldn't know.
Posts: 4,497
Likes: 0
Received 0 Likes
on
0 Posts
There is a hint in the name i guess. after all, they are ground spoilers, not flight spoilers... 
Usually those are design decisions between the need to dump lift on landing to achieve the required deceleration and the need for usage in flight where probably less of a spoiler control input is needed to achieve the design goals of roll augmentation and deceleration/drag increase if used as a speed brake. Of course those design decisions have other implications as the wing structure has to be designed to withstand the added stress of spoiler deployment in flight.
By the way, not a unique design of the 737, other aircraft have similar designs, for example on the A320 the spoiler 1 pair is used as ground spoiler only, as usual though, it is a bit more complicated there, as the spoiler pair 5 cannot be used as speed brake in flight, but roll control only, however it does act as a ground spoilers, as do the ailerons (aileron anti-droop).
Usually those are design decisions between the need to dump lift on landing to achieve the required deceleration and the need for usage in flight where probably less of a spoiler control input is needed to achieve the design goals of roll augmentation and deceleration/drag increase if used as a speed brake. Of course those design decisions have other implications as the wing structure has to be designed to withstand the added stress of spoiler deployment in flight. By the way, not a unique design of the 737, other aircraft have similar designs, for example on the A320 the spoiler 1 pair is used as ground spoiler only, as usual though, it is a bit more complicated there, as the spoiler pair 5 cannot be used as speed brake in flight, but roll control only, however it does act as a ground spoilers, as do the ailerons (aileron anti-droop).
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,179
Likes: 0
Received 0 Likes
on
0 Posts
And something implied in Denti's answer, but to state it explicitly - because the ground spoiler function wants as much lift dumped and drag created as possible, ground spoilers are (always - I bet someone will prove me wrong though) designed to either be stowed or fully deployed. there's no point in having "half ground spoilers".
Flight spoilers are intended to be a variable control, where you can command any of a range - perhaps a continuous range - of positions to get the amount of drag you want.
Its a lot simpler to design a ground spoiler control, as a result, than a flight spoiler. And thus cheaper. So you don't make them the fancier "flight spoiler" type (or even fancier spoileron type) unless it's required.
Flight spoilers are intended to be a variable control, where you can command any of a range - perhaps a continuous range - of positions to get the amount of drag you want.
Its a lot simpler to design a ground spoiler control, as a result, than a flight spoiler. And thus cheaper. So you don't make them the fancier "flight spoiler" type (or even fancier spoileron type) unless it's required.
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,179
Likes: 0
Received 0 Likes
on
0 Posts
Another design consideration which isn't as relevant to the 737 configuration, but I'll mention it anyway... on rear engined types, you don't want to have inflight spoiler type devices in front of the engines, for inlet distortion considerations. That leaves a big area of the inboard wing, that you'd like to be able to spoil for the landing/RTO cases, but want to avoid inflight. That naturally leads to installing ground-only spoilers in that location.
Even for an underwing type, spoiling the inboard wing in flight has more effect on the downwash at the tailplane than spoiling the flow further outboard, but that's not as big a factor as the engines. It's still a reason to prefer to not spoil the inboard flow, though. (There is a countering consideration, on swept wings, that you don't want to go too far outboard with flight spoilers for risk of having unacceptable pitching behaviour. So the mid span is where you tend to end up, for this and other reasons)
Even for an underwing type, spoiling the inboard wing in flight has more effect on the downwash at the tailplane than spoiling the flow further outboard, but that's not as big a factor as the engines. It's still a reason to prefer to not spoil the inboard flow, though. (There is a countering consideration, on swept wings, that you don't want to go too far outboard with flight spoilers for risk of having unacceptable pitching behaviour. So the mid span is where you tend to end up, for this and other reasons)
Join Date: Mar 2001
Location: I wouldn't know.
Posts: 4,497
Likes: 0
Received 0 Likes
on
0 Posts
That explains the Airbus setup i guess. Where the innermost spoiler is ground spoiler only, the outermost is only a roll and ground spoiler but not a speed brake spoiler. Similar to the 737 by the way, inner and outer spoilers are ground spoilers, the four middle ones are flight spoilers.
Rear mounted engines are not really used on airline jets anymore, but of course remain the standard configuration for most (all?) pure business jets.
Rear mounted engines are not really used on airline jets anymore, but of course remain the standard configuration for most (all?) pure business jets.
Join Date: May 2002
Location: still in bed
Posts: 190
Likes: 0
Received 0 Likes
on
0 Posts
B737 Max spoilers :
is somebody kind Enough to let me know if deployed spoilers after touchdowns do or do not retract automatically if power toga is applied ?
Thank you very much
is somebody kind Enough to let me know if deployed spoilers after touchdowns do or do not retract automatically if power toga is applied ?
Thank you very much
