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Aaron747
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Boeing 777/737 Ground Spoiler Deployment Question

Fri Sep 01, 2006 10:29 am

Howdy folks,

Don't usually ask too many questions around here but this is one of those obscure things that has been nagging at me for some time.

Over the years I've noticed that with regard to ground spoiler deployment on landing, certain Boeing aircraft have curious properties. On the 777, for example, (pardon my no doubt incorrect nomenclature) the #2 outboard spoiler panels have a more shallow angle than the other four.

http://www.pbase.com/cityflyer/image/40855033/large.jpg

And on the 737 classics, the first two panels have the same setting whereas the last two panels have full deflection. The 73G models have an even more unusual arrangement where the last outboard panel is standing all tall with other panels recessed.

http://www.pbase.com/cityflyer/image/45164764/large.jpg

http://www.pbase.com/cityflyer/image/62725426/original.jpg

Surely there is a rhyme and reason to this but for the life of me I can't guess what it might be. Can some of you more in the know folks please shed some light on this technical oddity?
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fr8mech
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Fri Sep 01, 2006 1:36 pm

Though I can't give you a definitive answer, I suspect it has to do with local airflow and the vibration properties in the local area.
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Aaron747
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Fri Sep 01, 2006 2:28 pm

I suspected it might have something to do with vibration but if that were the case, shouldn't all transport category aircraft employ a similar system?
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HAWK21M
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Fri Sep 01, 2006 4:28 pm

Firstly the Numbering should be from Left to Right so the Spoiler in question for the B777 should be #4.I suspect its the Ground spoiler.

On the B757 also certain Spoilers have a different angle of Deployment than others in Air & on Grd depending on the Aircraft.The Inboard Spoilers will deflect less in Air when used as Air brakes to avoid Turbulence affecting the Horizontal Stablizer behind.

regds
MEL
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Aaron747
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Fri Sep 01, 2006 4:54 pm

I knew the numbering was left to right, so I guess that's why I referred to it as the #2 outboard? The inboard spoiler is only a ground spoiler so maybe it's regarded differently.
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chrisMUC
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Fri Sep 01, 2006 5:31 pm

The two shallower ones on your pic from the 737 classics are Flight Spoilers, so most probably their movement is limited to that level to make it impossible to deploy them to far in flight (valve failure or any other problem).
I could imagine that's it the same with the 777.

Chris
 
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Aaron747
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RE: Boeing 777/737 Ground Spoiler Deployment Quest

Fri Sep 01, 2006 6:11 pm

Except that only the innermost of the outboard panels on the 777 isn't used in flight, as seen here.

http://www.pbase.com/cityflyer/image/45164814/large.jpg

This is really a stumper.

[Edited 2006-09-01 11:12:51]
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HAWK21M
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Sat Sep 02, 2006 10:08 pm

Quoting Aaron747 (Reply 6):
Except that only the innermost of the outboard panels on the 777 isn't used in flight

Looks like a Ground Spoiler Ops Only.
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MEL
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Tristarsteve
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Sun Sep 03, 2006 3:41 am

On the B777, spoilers 4 and 11 are the cable controlled spoilers. They stay faired until 54deg of spoiler lever travel then deploy.
Spoilers 5 and 10 do not deploy in flight. Ground ops only.

For roll control the inboards go to 20deg and the outboards to 45deg
For speedbrake the inboards go to 15deg and the outboards to 45deg.

Also on landing when ground spoilers deploy, there is a complicated logic that restricts full movement if the AOA is more than 2deg.

There is more to it than that, three whole pages in the manual! 27-61-00.
 
Tom12
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Sun Sep 03, 2006 6:57 am

Quoting Tristarsteve (Reply 8):

Interesting post, do you have a link where i could read into this further?

Tom
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Aaron747
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Sun Sep 03, 2006 8:25 am

Fascinating Steve. Any other good nuggets on spoiler properties in those three pages?
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HAWK21M
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Sun Sep 03, 2006 3:03 pm

Quoting Tristarsteve (Reply 8):
Also on landing when ground spoilers deploy, there is a complicated logic that restricts full movement if the AOA is more than 2deg.

I presume That would be Air-Grd sensed enabled too.
regds
MEL
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Tristarsteve
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Mon Sep 04, 2006 4:15 am

Quoting Tom12 (Reply 9):
Interesting post, do you have a link where i could read into this further

No sorry it is out of The B777 MM Pt 1. Cant reproduce it here.

And I forgot to add this is all in normal mode, There is also a secondary mode when some computors are downgraded, and a direct mode. The laws are different in each, there is less computor interference.

The reason that 5 and 10 do not deploy in flight is to do with turbulence over the stabilsor.
 
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Aaron747
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RE: Boeing 777/737 Ground Spoiler Deployment Question

Mon Sep 04, 2006 3:17 pm

So Steve, if I'm following, spoilers 4 and 11 (as pictured, #4) don't fully deploy in ground mode because they are operated by a different control system from the others?

It would appear that flight mode is slightly different as they seem to deploy evenly (provided that 4 and 11 have the necessary command from the cockpit spoiler lever).

[Edited 2006-09-04 08:19:51]
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