ground spoilers

[mainwheel]

Ground spoilers-B747,MD11,767,757's etc.Maybe even Airbus's.

Where is the sensor for deployment? Main gear shock strut, wheel transducers.

Any clues...................

[Intruder]

747-400: Tilt sensors on the main and body gear. I don't know how many of the 4 are required, though.

[None]

It's the same for the 757/767. The tilt happens at touchdown.

[Flight Detent]

Hi all,
In regard to your Q on deployment of ground spoilers on landing:

For the B737 NG,
Compession of any landing gear strut enables the flight spoilers to deploy.
Compression of the right main gear strut enables the ground spoilers to deploy.

Cheers

[HotDog]

On the 747, the ground safety master relay is energized when at least one left main gear truck (body or wing) plus one right main gear truck (body or wing) not tilt signal is sensed by either the landing gear primary or landing gear alternate logic module. This in turn operates other relays, one of which is the speed brake control system.

[Fresca]

Regarding the 737NG:

I know that the reversers unlock at right main strut compression, or at 5 ft radio altitude for the 737 Classic. Is it the same on the NG?

[Popolama]

fresca it s 10 ft RA ;)

[Flight Detent]

Hi all,

Right on, Popolama, 10 feet RA, or air/ground sensor in the ground mode, if the radar altimeter is u/s.

Cheers

[Red_Z3]

I thought in the (737NG) there was a sensor in the wheels, so as the moment the wheel started to spin spoiler deployed if in the armed position. I was riding jump seat on a 738 NG and on touch down on a contaminated runway the spoiler didn't deploy so the captain who was the pilot flying, manually deployed the spoilers.
after we vacated the runway and were taxing to the gate he asked both myself and the F/O if we noticed that we were aquaplanning and that's why the spoilers didn't deploy.
I could be wrong so if tha's the case please correct me.

Cheers Red :ok:


P.S. I'm not sure if the initial question was for automatic deployment of spoilers when armed ........ or just when can they be deploed.

please let me know if my post above is correct for auto deployment.

[B73567AMT]

Red...
U R correct. 737s use wheelspin up for Autospeedbrake activation.

[DDG]

Hope this clarifies things as some of the B737NG info and terminology is a bit mixed up!

Auto Speedbrake General;
The auto speedbrake module and the auto speedbrake relays control the automatic operation of the speedbrakes using data from the following sources:-speedbrake arming switch
-speedbrake RTO switch
-Autothrottle microswitch packs
-Antiskid/Autobrake control Unit(ACAU)
-Air/Ground relays(2)
-Antiskid sense relays(2)
-Flight Control Computers(2)
-Radio Altimeters <10 ft relays (2)
LANDING
During landing,the auto speedbrake operates when all these conditions occur;
1 altitude <10ft(signal from FCCs to 10ft R/A relays)

2 The main landing gear is on the ground OR main landing gear wheel speed signals(min 2 <60kts)

3 The speedbrake lever in the armed position

4 BOTH thrust levers at IDLE

During landing,the pilots arm the speedbrake lever.During the flare or at touchdown,the pilots move both thrust levers to idle.Just after touchdown, the auto speedbrake actuator fully extends the speedbrake lever.This commands all spoilers to move up.
The auto speedbrake actuator retracts if either thrust lever is more than the idle position once on the ground.

REFUSED TAKEOFFS (RTO)
During a RTO,when the pilot moves at least one of the thrust reverser levers,the speedbrake refused take off switch closes.This permits the auto speedbrake actuator to extend fully.This commands all spoilers to move up.
The auto speedbrake actuator retracts if either thrust lever is more than the idle position.

MANUAL SPEEDBRAKE CONTROL
When the speedbrake lever is moved up,the speedbrake lever cables move a quadrant in the spoiler ratio changer.The ratio changer moves the spoiler mixer,which supplies an input to the ground spoiler control valve.When the speedbrake lever moves past 31 degrees,the ground spoiler control valve sends hydraulic power to the ground spoiler interlock valve.
A push/pull cable connects the ground spoiler interlock valve to the right hand main landing gear torsion lind.When the airplane is on the ground,this cable opens the ground spoiler interlockvalve.This permits pressure to go to the ground spoiler actuators causing the groung spoilers to move up.

[B73567AMT]

I forgot that it can work off of air/gnd as well. Sorry.

[DDG]

No need to say sorry B73567AMT,i posted the info from the B737-600/700/800/900 AMM part 1 as there was some confusion due to people using differing terminology and phrases.Regards DDG.