AFGMEL
Topic Author
Posts: 190
Joined: Wed Jul 18, 2007 8:39 am

DC-10, MD-11 Inboard Airlerons

Wed Dec 16, 2009 2:22 am

I was playing around with flightsim and I noticed that when you make a strong turn, the inboard aileron appears to deflect into the jet blast. Is this just my perception and/or the inaccurate sim or was it specifically designed that way to lift the wing more effectively?

Thanks.
B 727-44/200 732/3/4/8/9 767-3 742/3/4, 772/3, A319/20/21 332/333 342/3 , DC3/4/10, F28/50/100, ATR72
 
jarheadk5
Posts: 216
Joined: Thu Nov 03, 2005 2:45 pm

RE: DC-10, MD-11 Inboard Airlerons

Wed Dec 16, 2009 5:24 am

The inboard ailerons on the KC-10 (which is basically a DC-10-30CF) are "above" the wing engines, and do deflect downward into the fan exhaust stream. I don't know whether this is a design feature to improve inboard aileron control authority, or if that was the only space left on the trailing edge to put the inboard aileron after the flaps and outboard ailerons were placed.
Cleared to Contact
 
User avatar
SEPilot
Posts: 4963
Joined: Sat Dec 30, 2006 10:21 pm

RE: DC-10, MD-11 Inboard Airlerons

Wed Dec 16, 2009 1:42 pm

When the B-47 was being designed it was discovered in wind tunnel testing that at high speed the ailerons on the wingtips when deflected instead of adding or detracting from the lift would instead twist the wing and essentially cancel themselves out; this was due to the structural differences between a straight and a swept wing. The solution was to add inboard ailerons much closer to the wing root, which are perfectly adequate at high speeds but lack sufficient control authority at low speeds, and so the outboard ailerons are still required (stiffening the wing structure to make the outboard ailerons effective at high speed would have added too much weight). The outboard ones are locked when at high speed, and only the inboard ones are used; I do not recall if the inboard ones deflect when the outboard ones are used or not, but from what you are seeing it appears that they do. I believe that all swept wing aircraft have followed this same pattern; what you are seeing in the sim I believe is just the way that on the DC-10 the inboard ailerons work. I suspect it is accurate.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
prebennorholm
Posts: 6419
Joined: Tue Mar 21, 2000 6:25 am

RE: DC-10, MD-11 Inboard Airlerons

Wed Dec 16, 2009 11:37 pm

Inboard ailerons must at all times be out of the jet blast.

If they were exposed to jet blast, then you would get roll responce varying according to engine power - different roll responces during climb, cruise and descend - in the latter case with engines at flight idle and consequently no jet blast.

Therefore you will also notice that inboard ailerons are not designed to endure the forces which the jet blast would expose on them.

If they did reach the jet blast (and they were designed to stay alive that way) then I think that it could create some very interesting sounds. Some quite funny shockwaves from the local supersonic air flow.

Primary control surfaces are kept away from jet blast on all planes. The only exception I can dream up is thrust vectoring, a mostly experimental feature to enhance combat maneuvering on fighter planes. Then there are of course VTOL planes like the British Harrier where the jet blast is the only primary control during vertical take off and landing. Four main nozzles provide transit bewteen hovering and horizontal flight as well as enhanced maneuvering, while a number of small nozzles in the tail and wingtips provide attitude control while hovering.
Always keep your number of landings equal to your number of take-offs
 
jarheadk5
Posts: 216
Joined: Thu Nov 03, 2005 2:45 pm

RE: DC-10, MD-11 Inboard Airlerons

Sun Dec 20, 2009 7:10 am



Quoting SEPilot (Reply 2):
The outboard ones are locked when at high speed, and only the inboard ones are used; I do not recall if the inboard ones deflect when the outboard ones are used or not,

At low speeds in the KC-10, the inboards and outboards both deflect.

.

Quoting Prebennorholm (Reply 3):
Inboard ailerons must at all times be out of the jet blast.

I guess I'll say it again...

Quoting JarheadK5 (Reply 1):
The inboard ailerons on the KC-10 (which is basically a DC-10-30CF) are "above" the wing engines, and do deflect downward into the fan exhaust stream.

Cleared to Contact

Who is online

Users browsing this forum: yeelep and 33 guests