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Boeing 777/737 Ground Spoiler Deployment Question

Aaron747 From Japan, joined Aug 2003, 7619 posts, RR: 28
Posted (6 years 8 months 3 weeks 14 hours ago) and read 15270 times:

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.

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.

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?

If you need someone to blame / throw a rock in the air / you'll hit someone guilty

13 replies: All unread, jump to last

Fr8Mech From United States of America, joined Sep 2005, 4238 posts, RR: 12
Reply 1, posted (6 years 8 months 3 weeks 11 hours ago) and read 15243 times:

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.

When seconds count...the police are minutes away!

Aaron747 From Japan, joined Aug 2003, 7619 posts, RR: 28
Reply 2, posted (6 years 8 months 3 weeks 10 hours ago) and read 15236 times:

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?

If you need someone to blame / throw a rock in the air / you'll hit someone guilty

HAWK21M From India, joined Jan 2001, 31201 posts, RR: 58
Reply 3, posted (6 years 8 months 3 weeks 8 hours ago) and read 15220 times:

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

Think of the brighter side!

Aaron747 From Japan, joined Aug 2003, 7619 posts, RR: 28
Reply 4, posted (6 years 8 months 3 weeks 8 hours ago) and read 15215 times:

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.

If you need someone to blame / throw a rock in the air / you'll hit someone guilty

ChrisMUC From Germany, joined Jul 2006, 66 posts, RR: 0
Reply 5, posted (6 years 8 months 3 weeks 7 hours ago) and read 15210 times:

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

Aaron747 From Japan, joined Aug 2003, 7619 posts, RR: 28
Reply 6, posted (6 years 8 months 3 weeks 7 hours ago) and read 15201 times:

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]

If you need someone to blame / throw a rock in the air / you'll hit someone guilty

HAWK21M From India, joined Jan 2001, 31201 posts, RR: 58
Reply 7, posted (6 years 8 months 2 weeks 6 days 3 hours ago) and read 15039 times:

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.
regds
MEL

Think of the brighter side!

Tristarsteve From Sweden, joined Nov 2005, 3687 posts, RR: 34
Reply 8, posted (6 years 8 months 2 weeks 5 days 21 hours ago) and read 15011 times:

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 From United Kingdom, joined Dec 2005, 1078 posts, RR: 14
Reply 9, posted (6 years 8 months 2 weeks 5 days 18 hours ago) and read 14989 times:

Quoting Tristarsteve (Reply 8):

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

Tom

"Per noctem volamus" - Royal Air Force Bomber Squadron IX

Aaron747 From Japan, joined Aug 2003, 7619 posts, RR: 28
Reply 10, posted (6 years 8 months 2 weeks 5 days 17 hours ago) and read 14978 times:

Fascinating Steve. Any other good nuggets on spoiler properties in those three pages?

If you need someone to blame / throw a rock in the air / you'll hit someone guilty

HAWK21M From India, joined Jan 2001, 31201 posts, RR: 58
Reply 11, posted (6 years 8 months 2 weeks 5 days 10 hours ago) and read 14950 times:

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

Think of the brighter side!

Tristarsteve From Sweden, joined Nov 2005, 3687 posts, RR: 34
Reply 12, posted (6 years 8 months 2 weeks 4 days 21 hours ago) and read 14899 times:

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.

Aaron747 From Japan, joined Aug 2003, 7619 posts, RR: 28
Reply 13, posted (6 years 8 months 2 weeks 4 days 10 hours ago) and read 14848 times:

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]

If you need someone to blame / throw a rock in the air / you'll hit someone guilty

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