Spoilers

[Rally]

Novice question here.

Why on landing do some spoilers come up initially but one delays on the 777? And I think the one that delays does'nt come up as much as the others? Also....I was on a flight on UAL one time into Germany from Washington, and when we landing the spoilers stayed up until the pilots shut of the engines at the gate? Why would this happen, was this a oversight?

Thanks

 

[grog_sit_reserv]

Forgot to disarm them after clearing the runway maybe?...

 

[Old School 737]

Ground spoilers and flight spoilers I assume. They come up at slightly different times and different deflections. 737 is the same. I don't fly the 777 but I bet it operates almost the same way.

 

[Rally]

Is there two switches or variable switches. Touchdown, flight spoilers then a little more weight and then ground spoilers?

 

[atrdriver]

Don't know about boeing products, but on the CRJ the spoilerons don't come out until both mains show WOW, so they can still be used for roll control in a crosswind landing. All the others come out with just 1 WOW signal. I wouldn't be surprised if they copied that idea from Boeing.

 

[Capt. Caucasian]

On the planes that I have flown the spoilers and the speed brakes are two different things. However, they do look similar.

Generally, the spoilers are the inner most set of flaps that extend from the top of the wing. They are used only on the ground to disturb the lift of the wing to aid the aircraft in "sticking" to the ground. Also, the speed brakes are slaved to the spoilers.

Some planes you have to arm the spoilers before landing (placing the speed brake lever in "arm") and others it is automatic. Wow (weight-on-wheels) and wheel-speed determine if the spoilers will be deployed on the ground. Some planes require the pilot to manually stow the spoilers and some automatically stow below a certain speed.

Speed-brakes are the flaps outside the spoilers. They do not extend as far as the spoilers and are actuated via the lever mentioned before.

Clear as mud?

 

[Rally]

Best answer yet....What is a WOW signal though. Weight on Wheels? Is there more than one?

 

[AKAAB]

The ground spoilers on some planes are actually pretty smart. The A320 will extend partial ground spoilers with weight on only one set of wheels and throttles at idle - then fully deploy when WOW is sensed on both gears. It keeps you from slamming the plane down when you roll one wheel on in a crosswind.

Let's wait and see if a 777 pilot will add to this discussion...

 

[Rally]

http://www.flightlevel350.com/Aircraft_Boeing_777-300-Airline_Air_France_Aviation_Video-5406.html

At :33 the spoilers deploy and then about 2 second later the rest deploy---the vid my help a little.

Thanks for all the responses.

 

[grog_sit_reserv]

WOW = Weight on Wheels

 

[Jim Smyth]

Usually Boeings are Boeings but I dont have any 777 experiance. The 737 has ground spoilers and also flight spoilers. There is a handle on the Captains side of the throttle quadrant that you can either pull it back to put the flight spoilers out in flight (like if you get a late crossing clearance or just miscalculate and are high on profile) or you can arm them for landing. If/when you arm them for landing on the 737 we get a 2 stage deployment. When the wheels make contact with the ground and start spinning, this allows the flight spoilers to deploy. Mind you that you are still about 8-10 inches above the ground at this point and as the airplane settles to the runway and you get strut compression you then get the ground spoilers also. This helps smooth the landing out in theory and also gets the weight of the airplane on the wheels which allows your brakes to be more useful. Not all planes are the same though. Years ago I flew a DC-9 for a few years and when you landed you got all the spoilers, ground and flight, deploying at the same time usually ruining all your good landings!

 

[Junkflyer]

Can't speak for the 777, but the 747 uses gear tilt to sense being on the ground (actually untilt) and spoilers deploy after a .6 second delay. There are 6 spoiler panels for each wing; the outboard 5 assist in roll control, the 2 inboard are speedbrakes inflight, and all 6 for ground spoilers. They retract with forward throttle movement.

 

[PlaneDrvr]

"Boeing Logic"

Boeing first put "Auto-spoilers" on the B-727; with main wheel spin-up (sensed by the left main), all spoilers deployed (flight and ground spoilers). This alway made for a definite 'firm landing' with a left crosswind, as that main away touched down first (with normal good x-wind technique, of course). And, then Boeing refined (improved) the system with the 737 (as the above post states); on main wheel spin-up (left main), the flight spoilers (the outboard panels) deploy, with full deployment being less of an angle (less drag) than the ground spoilers (the inboard panels), allows the a/c to more gently settle onto the main wheels, and with strut compression, the remaining spoilers (Ground spoilers, which deploy at a higher angle, meaning more drag) deploy to keep the weight firmly on the wheels. As said in the previous post; was design to make for a smoother touchdown with a 'staged deployment' of the flight and grd. spoilers.

Not sure about the B-777, but my guess, knowing "Boeing Logic" is that it probably works the same way; as when Boeing finds something that works well, they stick with. Kinda like; "Don't fix something that (works good) isn't broke"

But, maybe someone with 777 experience will chime in and let us know if it works the same on that a/c.

Hope that helps explain things.

DA