MD-11

Silverhawk

Silverhawk

New Member
I guess I never really noticed but the MD-11 has a third main wheel between the mains. Is this because of the additional cargo capacity that it allows for after passenger luggage etc...??

From an engineering or structural standpoint, why haven't larger freight liners, or passenger aircraft used this more frequently as opposed to the traditional gear placement. Or is it just a trait unique to the MD line ??

Just curious !!

MD-11 Pic
 
Hey that's kinda neat. I never knew that gear was under there. I guess that is my "something new that I learned today." Thanks.
 
I'm just making a guess, but maybe the wheel is there because there is more weight in the back of the plane because of the 3rd engine
 
Cool !! .. I guess I just never really noticed before... makes sense though. I may have to sneak out to Pitt to check out the 911th... I know they have a lot of refueler's out there at the airbase...
 
this has been on that airframe since the DC-10-30. the DC-10-10 didn't have it, but the DC-10-30 and DC-10-40 had it. seems like it'd be for those aircraft that can carry more weight so the plane's "footprint" won't damage the pavement. i have NO way to confirm this, just seems like common sense (also explains why the tanker would have it - heavy).
 
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this has been on that airframe since the DC-10-30. the DC-10-10 didn't have it, but the DC-10-30 and DC-10-40 had it. seems like it'd be for those aircraft that can carry more weight so the plane's "footprint" won't damage the pavement. i have NO way to confirm this, just seems like common sense (also explains why the tanker would have it - heavy).

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I think I'm correct on this but I believe it is to relieve stress on the spar with the added weight during touchdown and ground operations.
 
that makes sense, too. well at least we can pretty safely determine that it has something to do with the higher-gross weight models. anyone else have any ideas? i love to learn.
 
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How come the 777 has three wheels on the mains and the 767 only has two?

Things that make you go hum?

[/ QUOTE ] Think of the 3rd engine on the tail
 
Er, dude, he said 777.. that's definitely a twin jet. The MD-11 is
so a few posts ago!
cool.gif


As far as why the 777 has three on the mains, my guess would
be that it's because of the extra weight on the gear. It's a significantly larger plane and it would make sense to have the weight dispersed over an extra wheel on each gear assembly.
 
Anybody ever find it intresting that all the weight on a 777 would rest on just a little piece of those 14 tires?
shocked.gif

I'm guessing about 6 in. of contact with the ground per tire! (Which would be 7ft total)

Amazing how they got that to work out!
 
[ QUOTE ]
How come the 777 has three wheels on the mains and the 767 only has two?

Things that make you go hum?

[/ QUOTE ]


The 777 is a whole lot heavier. More even weight distribution.
 
The DC-10-30, KC-10, and MD-11 all have the same landing gear configuration (SBTT) because of...you guessed it...increased weight bearing capacity of the airframe. The MALW (Maximum allowable landing weight) of the KC-10 is 436,000 lbs. in the normal gear configuration, which is lowered to only 400,000 lbs. with the center gear retracted. The aircraft will not be dispatched at any weight unless the center gear is operational.

One interesting fact is that the center gear is not "stressed", and therefore must be retracted under any situation which may call for an abnormal gear configuration landing (e.g. left main gear will not extend). It is said that it will go right though the cargo floor if it is used as a main point of contact with the runway.

• S - Single Wheel type landing gear (DC-3)
• D - Dual wheel type landing gear (DC-6)
• T - Twin wheel landing gear (DC-6 again)
• ST - Single-tandem type landing gear (C-130)
• SBTT - Single-Belly Twin Tandem landing gear (KC-10, DC-10)
• DT - Dual-tandem type landing gear (B707)
• TT - Twin-tandem type (includes quadricycle landing gear B-52) (C-135)
• TRT - Triple-tandem landing gear (C-17)
• DDT - Double dual-tandem landing gear (B747)
• TDT - Twin delta-tandem landing gear (C-5)
 
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