Question on 737 spoilers...

[Hard-Drive]

I was on a 737 the other day, and the inner port spoiler was lifting up about 6" on climb out. The flaps were still down, and it was almost as if the airflow was getting under it and lifting it up. I'm no expert, but I can't see any reason why you'd want spoilers deploying on takeoff...as someone with a bit of glider experience it just seems all wrong!

Is this normal?

[S3_Graham]

I'm not rated in the 737 but on our Lear 45 the spoilers assist the ailerons and are hence called spoilerons. Possibly the same?

[Eric Mc]

Very normal. I'm pretty sure they are deployed to assist roll control.

[ijneB]

When the control wheel is displaced more than 10 degrees, spoiler deflection is initiated to supplement roll control. The spoiler movement is also proportional to aileron input.

[Hard-Drive]

Thanks for clearing that up. Seems odd though...so you've got flaps extended giving more lift, and spoilers deploying reducing lift at the same time

I'm also pretty sure it was only the inboard spoiler...I would have thought if you wanted to induce roll, the further outboard the control surface movement was, the better?

[Eric Mc]

Hard-Drive said:

Thanks for clearing that up. Seems odd though...so you've got flaps extended giving more lift, and spoilers deploying reducing lift at the same time

I'm also pretty sure it was only the inboard spoiler...I would have thought if you wanted to induce roll, the further outboard the control surface movement was, the better?

The flaps allow the plane to fly slowly. The spoilers assist in giving the pilot better roll control at slow speeds.

[RWD cossie wil]

Hard-Drive said:

Thanks for clearing that up. Seems odd though...so you've got flaps extended giving more lift, and spoilers deploying reducing lift at the same time

I'm also pretty sure it was only the inboard spoiler...I would have thought if you wanted to induce roll, the further outboard the control surface movement was, the better?

Only the down going wing spoilers pop, and only the flight spoilers, the ground spoilers are interlocked so they only work with weight on wheels for lift dump. The more aileron you apply, the more spoiler you get after 10 degrees of control wheel movement. You will also find that roll control over rides speed brake function.

[RWD cossie wil]

Hard-Drive said:

Thanks for clearing that up. Seems odd though...so you've got flaps extended giving more lift, and spoilers deploying reducing lift at the same time

I'm also pretty sure it was only the inboard spoiler...I would have thought if you wanted to induce roll, the further outboard the control surface movement was, the better?

Only the down going wing spoilers pop, and only the flight spoilers, the ground spoilers are interlocked so they only work with weight on wheels for lift dump. The more aileron you apply, the more spoiler you get after 10 degrees of control wheel movement. You will also find that roll control over rides speed brake function.

[anonymous-user]

A quick visual reference for those of us who are non-experts in aerodynamics and flight controls ;-)

[LimaDelta]

Hard-Drive said:

Thanks for clearing that up. Seems odd though...so you've got flaps extended giving more lift, and spoilers deploying reducing lift at the same time

I'm also pretty sure it was only the inboard spoiler...I would have thought if you wanted to induce roll, the further outboard the control surface movement was, the better?

I thought it was to reduce adverse yaw, rather than induce roll? (i.e balance the drag caused by the down-going aileron on the opposite wing). Also, following that, wouldn't the inboard spoiler be less likely to cause a wing drop in a low and slow configuration?

[Kempus]

Yeah spoilers, differential ailerons and rudder cross mixing through the yaw damper are all used to prevent adverse yaw.

I fly the triple but this never fails to amaze me what flight control computers can do! Everything going in all directions!

http://youtu.be/MsV6c5GdxNQ

Edited by Kempus on Saturday 20th December 17:48

[Mojocvh]

Gust damping

[davepoth]

Mojocvh said:

Gust damping

Sounds vaguely rude.

[perdu]

davepoth said:

Mojocvh said:

Gust damping

Sounds vaguely rude.

Not to those of us to whom it can be a boon