B757 spoiler/speedbrake logic

[XPMorten]

Hi,

For simulation purposes we need a bit of help on the
757 spoiler system. I have the AOM, but it's really not that
helpful explaining the logic.

What we need to know is stuff like;
- In a roll, do ALL the rollspoilers on the LOW wing deploy,
or does is the number of spoilers depend on Control Wheel input?
- Is it correct that CW input needs to be greater than 11 deg for
deployment of rollspoilers?
- You are in level flight WITH speedbrakes, then do a sharp turn,
what happens? Do the UP wing spoilers retract?
- what are the max deflections in degrees for speedbrakes and rollspoilers?

Other useful information would be appreciated as well, also
on similar types of acf.

Attach a drawing for easy reference.

http://www.xplanefreeware.net/morten/DIV/75spoilers.jpg

Cheers,

M

[Mad (Flt) Scientist]

What we need to know is stuff like;
- In a roll, do ALL the rollspoilers on the LOW wing deploy,
or does is the number of spoilers depend on Control Wheel input?
- Is it correct that CW input needs to be greater than 11 deg for
deployment of rollspoilers?
- You are in level flight WITH speedbrakes, then do a sharp turn,
what happens? Do the UP wing spoilers retract?
- what are the max deflections in degrees for speedbrakes and rollspoilers?
Other useful information would be appreciated as well, also
on similar types of acf.

Reference the last part (only) : for various Bombardier aircraft...

(1) On some of our types it's all spoilerons, on some there is a schedule where one spoiler is deployed first, then a second, and on some one pair is a reversionary mode following a failure which disables the primary spoilerons.

(2) to avoid spoiler deployment for small amounts of roll input, a control wheel deadband is common. Magnitude varies with aircraft.

(3) Roll control usually has priority over speedbrake mode for a multi-function spoiler, so, yes, the 'other' spoilers retract

(4) specifics not going to be much use for you on the wrong aircraft, but beware of hingewise vs streamwise conversions, which can be significant for swept hingelines.

[tristar 500]

What we need to know is stuff like;
- In a roll, do ALL the rollspoilers on the LOW wing deploy,
or does is the number of spoilers depend on Control Wheel input?
- Is it correct that CW input needs to be greater than 11 deg for
deployment of rollspoilers?
- You are in level flight WITH speedbrakes, then do a sharp turn,
what happens? Do the UP wing spoilers retract?
- what are the max deflections in degrees for speedbrakes and rollspoilers?

Mad (Flt) Scientist Speaking from memory on the B757 I think only the outboard spoilers deploy for roll control, yes it does depend on control input but I cannot remember the actual angles.
I have a feeling that the upgoing wing spoilers do retract but not fully.
Hope this helps I will have to get my manual out & gen up!!

[World of Tweed]

Quote Ref: From the 757. OM VOL 2 13.20.10 (the old version)

"The Control Wheels and the Speedbrake Lever send signals to the spoiler controller. The spoiler controller combines the signals from the Control Wheels and the Speedbrake Lever, determines the required spoiler panel deflection, and then signals the soiler panel actuators to operate."

This is the only FBW system on the 757 (i think). For specific deflection angles and combinations I would suggest you try and get a look a the Airplane Maintenance Manual (AMM) . Specifically looking at Flt Cntrl Checks as any testing regime for the spoilers will indicate what deflections are expected for control wheel input etc...

From experience in Malaga or any other suitably Mirrored terminal building I would say the Control wheel input is more like 25 degrees before the roll spoilers are deployed....but thats just a estimate.

[Piper19]

Right, from my 757 maintenance training document:
-control wheel steering moves ailerons, when 55° of CWS is reached, ailerons are at limit deflection of 20° up/dwn.
-max CWS movement is 85°
-aileron trim authority is 30° of control wheel deflection (6 units trim), which is 13° aileron deflection.
-autopilot authority is 22° of CWS, 53° with 2 autopilots
-all spoiler panels except 4 and 9 on your drawing can be operated with CWS alone
-spoiler pickup occurs at 10° CWS, with max deflection of 45° at 85° CWS.
-But, spoilers 6 and 7 are limited to 15° inflight, 30° on ground
-if CWS moved without speedbrake selected, spoiler panels go up on down going wing, other wing stays clean.
-if CWS is moved with speedbrake selected (panels already up), results in down going wing panels staying full up, and up going wing panels lowering. Same for partially selected speedbrake.
-speedbrake operation in flight: panels 1,2,3,10,11 and 12 deploy to 30° max. panels 5 and 8 deploy to 20°. panels 6 and 7 only to 15°. Panels 4 and 9 do not move in the air.
-speedbrake operation on ground: panels 4 and 9 go to 55°; 6 and 7 to 30°; remaining panels to 45°
-panels 2,3,10 and 11 have 1,25 second time delay on ground deployment to reduce pitch up effect.

Should give you enough info for creating the ultimate 757 sim.

[XPMorten]

EXCELLENT Piper19 :D Thanks to everyone else as well.
Looks like we have some serious coding to do here..

Cheers,

M