Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Strange Control Surface On The Wing Of The 767  
User currently offlinePyrex From Portugal, joined Aug 2005, 4063 posts, RR: 30
Posted (6 years 8 months 3 weeks 5 days 19 hours ago) and read 7371 times:

Hi guys,

I just did a flight for the first time in a 767, a Delta -300(ER?) from ATL to GIG and, while landing, noticed on the wing what seemed to me a strange control surface. It was large, between the inboard and outboard flap on the trailing edge of the wing, took about 25% of the chord and had an awkward shape. At first I thought it was another spoiler but it didn't move in tandem with the spoilers. It did, however, move when the aircraft was turning.
I think it might be some kind of roll damper but I had never seen anything quite like that. If it is, in fact, a roll damper, it mustn't be very efficient to have such a large moving surface just for that. Can anybody help me identify this control surface?
Thanks,

Miguel


Read this very carefully, I shall write this only once!
32 replies: All unread, showing first 25:
 
User currently offlineFutureUALpilot From United States of America, joined May 2000, 2608 posts, RR: 8
Reply 1, posted (6 years 8 months 3 weeks 5 days 18 hours ago) and read 7366 times:

High speed aileron IIRC.


Life is better when you surf.
User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 2, posted (6 years 8 months 3 weeks 5 days 18 hours ago) and read 7366 times:

Off the cuff, it sounds like an inboard aileron. Can you find a picture? That would settle it.


Proud OOTSK member
User currently offline2H4 From United States of America, joined Oct 2004, 8956 posts, RR: 60
Reply 3, posted (6 years 8 months 3 weeks 5 days 18 hours ago) and read 7371 times:
AIRLINERS.NET CREW
DATABASE EDITOR



Quoting Pyrex (Thread starter):
It was large, between the inboard and outboard flap on the trailing edge of the wing, took about 25% of the chord and had an awkward shape.

Sounds like the inboard aileron:


View Large View Medium
Click here for bigger photo!

Photo © Stuart Lawson [Airplane-Pictures]
View Large View Medium
Click here for bigger photo!

Photo © Jerome Mervelet



2H4



Intentionally Left Blank
User currently offlinePyrex From Portugal, joined Aug 2005, 4063 posts, RR: 30
Reply 4, posted (6 years 8 months 3 weeks 5 days 18 hours ago) and read 7355 times:



Quoting 2H4 (Reply 3):
Sounds like the inboard aileron:

That is exactly it. Is it normal for widebodies to have these or is it just the 767 aileron's that have little roll authority?



Read this very carefully, I shall write this only once!
User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 5, posted (6 years 8 months 3 weeks 5 days 18 hours ago) and read 7353 times:

It is a fairly normal design feature. On may types of aircraft, the outboard aileron will lock out to limit the twisting stress on the wing at high speeds.


Proud OOTSK member
User currently offlineUAL747 From , joined Dec 1969, posts, RR:
Reply 6, posted (6 years 8 months 3 weeks 5 days 17 hours ago) and read 7296 times:



Quoting Pyrex (Reply 4):
That is exactly it. Is it normal for widebodies to have these or is it just the 767 aileron's that have little roll authority?

This is the high speed aileron, or inboard aileron. It's common on Boeing widebody aircraft, although the 787 will feature only outboard ailerons. Modern Airbus widebodies do NOT have inboard ailerons.

The outboard ailerons lock after the flaps are fully retracted or at a certain speed and only the inboard ailerons are used in cruise. The theory is that at slower speeds, the outboard ailerons kick in because they will have the most effectiveness because they are farthest away from the center of gravity. They lock out at high speeds because the inboard ailerons are sufficient and give less loading on the wing when in action.

UAL


User currently offlineCptSpeaking From United States of America, joined Apr 2006, 639 posts, RR: 1
Reply 7, posted (6 years 8 months 3 weeks 5 days 16 hours ago) and read 7251 times:

Ok, I understand the theory behind limiting the twist of the wing at high speeds, but the effectiveness theory doesn't sound right to me...

Airplanes that have the most "effectiveness" rolling would have to be the T-38, the Pitts S-2, etc...but the common denominator here is SHORT wings and less distance from the flight controls to the CG. Seems to me that a control deflection 20 feet out on the wing gives you twice the roll rate of the same deflection at 40 feet out on the wing. If you watch videos of these high speed ailerons, you'll see that they're really moving around and working a lot at LOW speeds. Am I just way off on this?



...and don't call me Shirley!!
User currently offlineLowrider From United States of America, joined Jun 2004, 3220 posts, RR: 10
Reply 8, posted (6 years 8 months 3 weeks 5 days 15 hours ago) and read 7198 times:

Quoting CptSpeaking (Reply 7):

The aircraft you mentioned also have ailerons that are relatively large compared to the wing they are on. The short span combined with the large ailerons help generate the dramatic roll rate.

As to your question on the deflection of the ailerons, all other things (air pressure, altitude, etc) being equal, a control surface will have to deflect further at a lower airspeed to generate the same result as a smaller deflection at a higher airspeed. This is why the outboard ailerons can be locked out at high speed with no penalty. If they fail to unlock during approach, then you do suffer penalties. The simplest way to visualize it is to imagine a boat and note the effectiveness of the rudder at 5,10, and 20 knots.

Hope this thumbnail sketch helps.

[Edited 2008-03-30 15:40:46]


Proud OOTSK member
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2577 posts, RR: 25
Reply 9, posted (6 years 8 months 3 weeks 5 days 14 hours ago) and read 7167 times:



Quoting CptSpeaking (Reply 7):
Airplanes that have the most "effectiveness" rolling would have to be the T-38, the Pitts S-2, etc...but the common denominator here is SHORT wings and less distance from the flight controls to the CG. Seems to me that a control deflection 20 feet out on the wing gives you twice the roll rate of the same deflection at 40 feet out on the wing. If you watch videos of these high speed ailerons, you'll see that they're really moving around and working a lot at LOW speeds. Am I just way off on this?

They've been called high speed ailerons here. All speed aileron is more accurate. The inboard/all speed ailerons work at low speeds and high speeds. Outboard/low speed ailerons work at low speeds, not at high speeds. These are generalisations, there are a lot of detail differences between aircraft types.

As for roll rates, an aircraft with a short stubby wing can generate a high roll rate because the roll damping from the wing is small (centre of pressure of the wing close to the CG) compared to one with high aspect ratio wings. They also have lower inertia about the roll axis, too. Ailerons are less effective closer to the CG (their leverage is less in layman's terms). Larger aileron area can make up for less leverage. Hence high rate of roll in the T-38, Pitts S-2, etc.

Quoting UAL747 (Reply 6):
Modern Airbus widebodies do NOT have inboard ailerons.

The A330 and A340 do have inboard and outboard ailerons but they are side by side, outboard of the flaps. In manual flight outboard ailerons only deflect at low speeds (< 190 kts) with flaps extended. In automatic flight and with certain failures they operate with the inboards up to 300 knots.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineUAL747 From , joined Dec 1969, posts, RR:
Reply 10, posted (6 years 8 months 3 weeks 5 days 13 hours ago) and read 7154 times:



Quoting Jetlagged (Reply 9):
The A330 and A340 do have inboard and outboard ailerons but they are side by side, outboard of the flaps. In manual flight outboard ailerons only deflect at low speeds (< 190 kts) with flaps extended. In automatic flight and with certain failures they operate with the inboards up to 300 knots.

Ah, well, I learn something new everyday. However, I still consider those to be a "set" of outboard ailerons when compared to the distance of the inboard ailerons from the Boeing aircraft, but to each his own. I wonder then what they call all 3 of them on the A380? Outboard, Middle, Inboard Ailerons? BTW, speaking of the A380's ailerons, does anyone else think that their movements are really strange? It seems there is no method to the madness as they are ALL always moving, some down while others up.....strange...though I know that there is a reason for it, just can't explain it.

UAL


User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 11, posted (6 years 8 months 3 weeks 5 days 12 hours ago) and read 7136 times:



Quoting UAL747 (Reply 10):
...though I know that there is a reason for it, just can't explain it.

I seem to remember that the A380 was fitted with an active gust load alleviation system for the wing. Perhaps the aileron movements are due to this function  Confused .

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineFlyASAGuy2005 From United States of America, joined Sep 2007, 7004 posts, RR: 7
Reply 12, posted (6 years 8 months 3 weeks 5 days 12 hours ago) and read 7134 times:

Ahhhh. I always wondered what those things exactly were also.


What gets measured gets done.
User currently offlineViscount724 From Switzerland, joined Oct 2006, 26005 posts, RR: 22
Reply 13, posted (6 years 8 months 3 weeks 5 days 11 hours ago) and read 7110 times:

The 707 and 727 also have outboard and inboard ailerons.


View Large View Medium
Click here for bigger photo!

Photo © Peter Kesternich
View Large View Medium
Click here for bigger photo!

Photo © Bruce Leibowitz



User currently offlineCptSpeaking From United States of America, joined Apr 2006, 639 posts, RR: 1
Reply 14, posted (6 years 8 months 3 weeks 5 days 10 hours ago) and read 7084 times:



Quoting Jetlagged (Reply 9):

I'm pickin up what you're puttin down about the center of pressure, dampening, etc., but I'm still struggling with how ailerons closer to the CG are less effective...

I'll go read up a bit in my Aerodynamics books and see if I can find an answer I can visualize...



...and don't call me Shirley!!
User currently offlineLemmy From United States of America, joined Dec 2004, 260 posts, RR: 0
Reply 15, posted (6 years 8 months 3 weeks 5 days 10 hours ago) and read 7074 times:

I've heard stories about 747 test flights with the outboard aileron lockout deactivated. At high speeds, the pilot was able to quickly turn the wheel to full deflection and the plane stayed put. This is because the wing twisted in the opposite direction enough to counteract the aileron.

Quoting CptSpeaking (Reply 14):
I'm pickin up what you're puttin down about the center of pressure, dampening, etc., but I'm still struggling with how ailerons closer to the CG are less effective...

I think they key has less to do with roll rate than with roll authority. Since they outboard ailerons are further from the CG, they've got far more leverage. This means they'll be more responsive at low speeds. Think of it this way: if you had to roll an airplane by grabbing the wing and pulling down, you'd have to apply much more force to get it started by holding the wing root. For the same amount of force, you'd get it started easier at the wing tip.



I am a patient boy ...
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2577 posts, RR: 25
Reply 16, posted (6 years 8 months 3 weeks 5 days 2 hours ago) and read 6999 times:



Quoting CptSpeaking (Reply 14):
I'm pickin up what you're puttin down about the center of pressure, dampening, etc., but I'm still struggling with how ailerons closer to the CG are less effective...

I'll go read up a bit in my Aerodynamics books and see if I can find an answer I can visualize...

It's not so much to do with aerodynamics, its forces and moments. The same size aileron twice as far away from the CG will produce twice as much rolling moment.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineCoolGuy From United States of America, joined Jan 2005, 414 posts, RR: 0
Reply 17, posted (6 years 8 months 3 weeks 4 days 23 hours ago) and read 6940 times:

Also on the 777 the inboard moves down when the flaps extend.

User currently offlineTroubleshooter From Germany, joined Feb 2005, 423 posts, RR: 4
Reply 18, posted (6 years 8 months 3 weeks 4 days 21 hours ago) and read 6897 times:

Nobody mentioned the A310 which has no outboard ailerons installed.

View Large View Medium
Click here for bigger photo!

Photo © Nick de Jonge - Jet-A1 Images




This job sucks!!! I love this job!!!
User currently offlineLongbowPilot From United States of America, joined Jan 2005, 577 posts, RR: 3
Reply 19, posted (6 years 8 months 3 weeks 4 days 12 hours ago) and read 6752 times:
Support Airliners.net - become a First Class Member!

I know something too. Spoilers help too Big grin

-Attack


User currently offlineHappy-flier From Canada, joined Dec 1999, 299 posts, RR: 0
Reply 20, posted (6 years 8 months 3 weeks 4 days 11 hours ago) and read 6737 times:

Yup! A310 has no outboards.

Perhaps less known, but also true, is the fact that the Convair jets - the 880 and 990 - had no outboard ailerons, only inboards. Making it even more idiosyncratic, the CV990 had no inboard spoilers, just immediately inboard of the outer engines. This particularly good perspective of the NASA CV990 shows this peculiarity quite well.



May the wind be always at your back . . . except during takeoff & landing.
User currently offlineMir From United States of America, joined Jan 2004, 21864 posts, RR: 55
Reply 21, posted (6 years 8 months 3 weeks 4 days 10 hours ago) and read 6708 times:



Quoting CptSpeaking (Reply 7):
Seems to me that a control deflection 20 feet out on the wing gives you twice the roll rate of the same deflection at 40 feet out on the wing.

Actually, a control deflection 20 feet out on the wing would give you half the roll rate of the same deflection 40 feet out on the wing. This is just simple physics: force X arm = moment. If you're trying to turn a bolt with a wrench, you're going to have a much easier time if you hold the part of the wrench furthest from the bolt, because the additional arm will make your efforts much more effective.

Comparing the effectiveness of a 767's ailerons to those of a T-38 is comparing apples to oranges. Or, more accurately, apples to coffee tables - they're nothing alike.  Smile

Quoting CptSpeaking (Reply 7):
If you watch videos of these high speed ailerons, you'll see that they're really moving around and working a lot at LOW speeds. Am I just way off on this?

Since they are less effective than the outboard ailerons, they do have to move around more to achieve a similar result.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlinePanman From Trinidad and Tobago, joined Aug 1999, 790 posts, RR: 0
Reply 22, posted (6 years 8 months 3 weeks 4 days 10 hours ago) and read 6704 times:



Quoting Troubleshooter (Reply 18):
Nobody mentioned the A310 which has no outboard ailerons installed.

Just like the early A300s. I can confirm that the TNT A300 which we have in the hangar at the moment only has an inboard aileron.

PanmaN


User currently offlineCptSpeaking From United States of America, joined Apr 2006, 639 posts, RR: 1
Reply 23, posted (6 years 8 months 3 weeks 4 days ago) and read 6619 times:



Quoting Mir (Reply 21):

I think I'm starting to get it...my tiny little brain was thinking that if I push down on the wingtip 2 feet at a certain rate, the airplane will roll at x rate, and if I push down at half the distance for 2 feet at the same rate, I'll get twice the roll rate, and the wingtip will now be 4 feet down rather than 2 with the same force being applied, just in a different spot...what I wasn't considering was the difference in force required caused by the difference in arm/moment...got it now though, thanks  Smile



...and don't call me Shirley!!
User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 24, posted (6 years 8 months 3 weeks 3 days 20 hours ago) and read 6570 times:



Quoting Mir (Reply 21):
If you're trying to turn a bolt with a wrench, you're going to have a much easier time if you hold the part of the wrench furthest from the bolt, because the additional arm will make your efforts much more effective.

Lemmy's story suggests that you might also extend this analogy;

Imagine a seized bolt - one that resists turning. Gaining more leverage with an extension bar might get it undone, but it also might just shear the bolt - or bend the extension bar.



Todos mis dominós son totalmente pegajosos
25 Blackbird : To Pyrex, Regarding the wing of the Boeing 767, you probably saw the high-speed aileron. Traditionally, the best place to put the ailerons on a wing a
26 Tdscanuck : The amount of counter-torque caused by dragging the wings through the air as you roll. Thing of a rolling airplane as a paddle wheel with the wings a
27 Jetlagged : Damping is a force opposing motion, due to velocity. So roll damping is a rolling moment opposing the rolling motion due to roll rate. If you initiat
28 Blackbird : Tdscanuck and Jetlagged, Thank you for the explanations Blackbird
29 Mir : No exceptions. The further out the aileron is, the higher the roll rate will be (all other things equal). FxA=M doesn't lie. -Mir
30 Blackbird : Mir, What about roll damping?
31 Vikkyvik : Neither does F=MA I assume he meant all other things being equal.
32 Mir : Not part of the equation. I did say "all other things being equal". Granted, roll damping will make it harder for a long-winged aircraft to turn than
Top Of Page
Forum Index

Reply To This Topic Strange Control Surface On The Wing Of The 767
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Control Surfaces On The Wing posted Tue Sep 16 2003 18:35:39 by DIJKKIJK
Ailerons, Flaperons, Flaps - All On The Same Wing posted Sat Jul 7 2007 13:31:28 by TripleDelta
Tri-motor - What's That On The Wing? posted Thu Nov 9 2006 00:50:53 by TimePilot
A Yellow "hole" On The 737 Wing posted Tue May 18 2004 23:31:59 by Tg 747-300
What's This Object On The 747-SP's Wing? posted Mon Feb 9 2004 22:04:40 by Mr Spaceman
Doors On The 767 & 777 posted Fri Nov 28 2003 01:50:07 by Fanoftristars
What Is That On The Wing? posted Fri Nov 14 2003 00:44:54 by KYIPpilot
Ridges On The Wing posted Thu Jul 11 2002 15:12:07 by Ngr
'vortex' On Top Of The Wing? posted Sun Apr 28 2002 14:29:22 by Staffan
CFM & RR On The Same Wing! posted Sat May 12 2001 03:00:54 by Bio15
A Puff Of Smoke From The Wing Of A 727? posted Thu Nov 24 2011 01:13:13 by B737-112
Skin Buckling On The Wing Surface? posted Wed Apr 20 2005 02:59:51 by Bio15
Control Surfaces On The Wing posted Tue Sep 16 2003 18:35:39 by DIJKKIJK
3rd FMC On The 767, PFD posted Tue Jan 31 2012 06:43:22 by krisyyz
What Are These On The 747(classic) Wing Tips? posted Fri Dec 31 2010 14:36:39 by airbusb0y
Wing Strobes On The DC-9-30 posted Mon Jul 19 2010 07:13:42 by c5load
Engines Under The Wing And On The Tail At Once posted Wed Nov 18 2009 17:35:36 by YYZALA
What Is This On The Wing? ( OS A319) posted Wed Jul 22 2009 06:43:20 by OHLHD
Lot Of Time On The Wing posted Fri Dec 19 2008 15:10:33 by Venus6971

Sponsor Message:
Printer friendly format