About B737 spoilers (speed brakes).?

Question

I noticed that 737 spoilers seem to be divided into groups of three on each wing:

The Outboard group, Midboard group, and Inboard group.

I also noticed that during "slow-downs" (after de-rotation/on landing), the spoilers -when deployed- don't all stand up at the same angle; the Outboard and Inboard groups do stand at the same higher, steeper angles than the Midboard group.

This seems to be a "constant" thing as I can remeber from childhood (I logged a lopt of kiddie frequent flyer miles) up to present -where I still see the same thing in photos like the one I've attached. My question is "Why this peculiar difference in deployment angles? Does it have anything to do with the Outboard/Inboard being dedicated to full deceleration-on-the-ground while the Midboarders are dedicated to the fullest/wing-friendly deceleration-in-the-air?

Answer 1

That group of foils performs 3 different functions. They are part of the flapp-eron combo, flight spoilers, and ground spoilers. This functionality change happens automatically. There are 5 panels on each wing making all of this happen.

-The middle 2 panels are the "flight spoilers" during normal flight.

-When the flaps are extended all the panels work to kill some the ballooning lift that happens when the flaps are extended and you want that wing to go down. The aileron alone is not as effective way out on the outboard edge when you have all of that "laundry" hanging out in the mid section so this helps lower the wing more effectual and avoids some twisting loads. The inboard panels raise up at a sharper angle in this mode as this part of the wing has more chord and requires more lift-killing.

-Then as speed brakes they will all raise up fully automatically when the speed brakes are armed and the ground is detected. They don't all extend to the same degree so the air has somewhere to go other than straight to the outboard end of the wing.

http://www.airliners.net/open.file/1044992/L/

Answer 2

They have different purposes... the middle ones are flight spoilers that can be used to shed some airspeed mid-flight... the inboard ones are the real spoilers and they are the biggest... and the outside ones double as an aileron in flight... it does not have the full range of motion... it can only deflect up and thus, is only effective when the pilot wants that wing to go down... The ailerons are largely useless on the ground so they can use these ailerons/ spoilers on the ground with no loss of control...

Answer 3

the spoiler nearest to the fusalage will b having more air flow compared to others!
so all stand up at their respective angles and the speed ,length of runway ,weight of plane...

Answer 4

its to do with stall speed...