BA777
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767 Main Bogies Tilt Forwards!?

Tue Apr 23, 2002 5:45 am

Guys,

Is there an explination as to why the 767s main bogies tilt forward, and the 777/747 and probably other boeing aircraft's main bogies tilt backwards?

Any reason?

BA777
 
D L X
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RE: 767 Main Bogies Tilt Forwards!?

Tue Apr 23, 2002 5:53 am

From what I understand, the forward tilt of the 767 (as opposed to the backwards tilt or level gear of all other multiple axle aircraft) is so that the gear would fit in their housings under the plane's body.

Just a different design, really, no big deal. Think about it this way: when you jump up in the air, do you land on your toes first, or your heels first? 767s land on their toes first.
 
roguetrader
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RE: 767 Main Bogies Tilt Forwards!?

Tue Apr 23, 2002 6:00 am

There was a short note about this in Airliners or somewhere several months ago. Like D L X says, it is purely a question of fitting in the gear in the best way with all the other structures in that part of the plane. Apparently, it offers no significant operational advantages or disadvantages, it is just the best way they could find to make the gear fit.

kind regards,

RogueTrader
 
AFa340-300E
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RE: 767 Main Bogies Tilt Forwards!?

Tue Apr 23, 2002 6:18 am

Hello,

Indeed the two main landing gears of the 767 tilt forward to fit in the fuselage between the aft cargo hold and air conditionning system.


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Alain Mengus
Air Transport Business
 
777236ER
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RE: 767 Main Bogies Tilt Forwards!?

Tue Apr 23, 2002 6:39 am

Nope.

The 777's MLG tilt BACKWARDS when down, but tilt 5 degrees forwards when they're in the bay to fit in.

The main reason for this is due to fuselage geometry. The 767 has a tendancy to pitch forwards after touch-down. The gear tilting forwards helps to keep the nose up longer as some energy is dissipated in straightening the gear and tilting them backwards as the a/c touches down.

On the 777, for example, the gear is tilted backwards. Not only does this help smooth the landing (767 landings are always pretty hard), but it also helps to straighten the 777 out as it lands, as the straightening gear helps LOWER the nose.

It's really just a matter of design choice, there's not a lot of difference.
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apuneger
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RE: 767 Main Bogies Tilt Forwards!?

Tue Apr 23, 2002 6:56 am

A couple of years ago, I read the very same question in an aviation-related mag (can't remember which one).

Anyway, one of the experts (well, the guy who answered the reader's question) said that it (also?) has something to do with the time in which the 767 was developed (at the time the 767 was being developed, two oil crises occured). Therefore, the wing or center of gravity or whatever, was put more in front or so, hence the forward tilting bogeys.

I don't know if this makes sense, but I just try to remember what I read back then...

Ivan
Ivan Coninx - Brussels Aviation Photography
 
zebfly2
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RE: 767 Main Bogies Tilt Forwards!?

Tue Apr 23, 2002 7:32 am

I can recall when I first started flying on 767's back in the late-80's, their landings did not seem to be smooth and I thought that the position of the landing gear had some thing to do with the rough landings. Now when I fly 767's the landings are much smoother. Can anyone recall the same experiences? Is it possible that over a period of time pilots became more familiar with the a/c which in turn led to smoother landings? I'm not trying to slight or question the skills of any pilots out there, but rather discussing facts that I am aware of when I first started flying on 767's. Any comments would be appreciated. Thanks.
Educate your children before others mis-educate them!!!
 
Rick767
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RE: 767 Main Bogies Tilt Forwards!?

Tue Apr 23, 2002 7:38 am

Zebfly2,

I'm sure your experiences were just coincidental. I am not aware of any changes in the landing gear design or any other aspect which has made the 767 smoother at landing.

I find it easier to make a smooth landing in the 767 than the 757 (especially the -200, love that bird!) but then some other pilots in my company find the opposite.

From day one my landing experiences in the 767 have been the same, some days it's good, some days it's not. I haven't found myself getting better at it over the years... yet!  Smile
I used to love the smell of Jet-A in the morning...
 
D L X
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RE: 767 Main Bogies Tilt Forwards!?

Tue Apr 23, 2002 7:44 am

Oh, one more reason for the forward tilt: so it would be easier for spotters to tell it's a 767 while still distant.

(Okay, I'm only somewhat sure the Boeing engineers thought about that.  Big grin )
 
BlatantEcho
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?

Tue Apr 23, 2002 9:21 am

I have never heard a single one of the stories mentioned above. From what I have gathered here, and in aviation magazines (this is discussed monthly here, honestly) was rather simple.

Designing the gear, the wheels were either smaller and closer together, or the whole gear assembly was just smaller. The loading on the ground was a bit high, so they stretched out the gear a bit, maybe with bigger wheels, I don't remember. Anyway, it was very close to the end of the design phase, and with a bigger gear, they would have had to goof with the center wing box and all that jive to get it to fit. Someone figured out that a gear tilted forward would squeeze right in, so there you go.

As I said, I have garnered this information from the same question being asked 1000 times on this site, and every time the reply has been "Titled forward to fit in it's bay" nothing more or less.

I will be thrilled if there is more to it, but I'll want proof first.

regards,
BlatantEcho
They're not handing trophies out today
 
rmm
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RE: 767 Main Bogies Tilt Forwards!?

Tue Apr 23, 2002 10:44 am

The MLG tilts 17 degrees to fit into the wheel well. It was not an after thought. What boeing didn't compensate for was the arc of the retract actuator. Our instructor told us on the first gear swing in the factory, the actuator rod ends punched holes in the upper wing skin.
If you look closely on approach (and sitting in the right row) you'll see a small door raise and lower on top of the wing while the gear is extending.

Rmm
 
242
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RE: 767 Main Bogies Tilt Forwards!?

Wed Apr 24, 2002 6:58 am

Nope.

The 777's MLG tilt BACKWARDS when down, but tilt 5 degrees forwards when they're in the bay to fit in.

The main reason for this is due to fuselage geometry. The 767 has a tendancy to pitch forwards after touch-down. The gear tilting forwards helps to keep the nose up longer as some energy is dissipated in straightening the gear and tilting them backwards as the a/c touches down.

On the 777, for example, the gear is tilted backwards. Not only does this help smooth the landing (767 landings are always pretty hard), but it also helps to straighten the 777 out as it lands, as the straightening gear helps LOWER the nose.

It's really just a matter of design choice, there's not a lot of difference.




I think that's the best explanation. The fact of the matter is that the 757, 767 and the 777 all have tilt actuators on the main gear, and all of them must tilt the gear forward upon retraction to fit them in to their gear wells. There has to be another reason for leaving the 767 mains tilted down, considering the 757 and 777 tilt them backwards during deplyment.
 
FDXmech
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RE: 767 Main Bogies Tilt Forwards!?

Wed Apr 24, 2002 7:35 am

How about the A300/A310?

The A300's are level, the A310 tilts forward.
You're only as good as your last departure.
 
hkgspotter1
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RE: 767 Main Bogies Tilt Forwards!?

Wed Apr 24, 2002 9:25 am

The A340-600's main wing gear tilt back but the main center gear tilts forward !!
 
calpilot
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RE: I Like The Way 767's Land

Wed Apr 24, 2002 11:28 am

I agree with Rick, I can usually get better landings in the B767-200. The -400 is another story for me. However, my DL buddy likes the -400 better, so go figure?
 
Guest

RE: 767 Main Bogies Tilt Forwards!?

Wed Apr 24, 2002 3:50 pm

The one that looks strange is the A340-600. The center gear tilting one way and the outer gear tilting the opposite way.

http://www.airliners.net/open.file/201681/L