Tilting Bogeys...
 

Ok then,

Is someone able to explain to me why the main gear bogeys on large airliners tilt backwards when off the ground? I guess the answer is a simple one, but I'd like to hear it never the less!

I'm not that sure whether the answer is such a simple one, as there are also birds out there with a forward tilting one. (767).

They tilt back to help absord the "impact" of the landing, the bogies are held in that position so that they absorb some of the force of the landing making it smoother.
However if they cant fit them into the wheel wells in that position then they will tilt them the other way, such as in the case of the 767, which is why it is a lot harder to grease a landing in a 767!

They just tilt to that position, forward or aft, to fit in the wheel weel. Simple as that


Sq

Captain Squelch,

That is the correct answer!


Regards
Exeng

I know Exeng!

Sq

You are not the weakest link Captain Squelch!!

From memories, Triple 7 have different tilt angles.

At takeoff gears tilted backwards, on landing gears tilted forwards.

------------------
Not much of an engineer

I suspect that the primary reason is to save space as tilted bogies take up less room.

However I believe that tilted bogies allow a gradual 'spin-up' of the wheels and this saves on tyre degradation and also stress forces on the undercarriage on touchdown.

Correct me if i'm wrong

Captain Squelch is spot on. Whatever fits in the wheel well. Nothing more nothing less.

On my aircraft, the bogies are tilted nose up for landing. The action of landing and tilting the bogie compresses a piston called the 'hop damper', which has the sole purpose of damping out the landing, thus saving G&Ts/Martinis. On gear retraction, another jack tilts the bogie nose down so it fits in the well.

This aircraft however, was built in the days when the British Aircraft industry built proper airliners, and money was no object!

Which aircraft am I talking about?

(BEagle is excluded from this question!)

Trident??

VC10 methinks!

Beautiful machine.....

For the A330/A340 the MLG holds a 14 deg nose up tilt. This allows most of the landing shock loads to be absorbed by the time the front truck wheels rotate to contact. During gear retraction a mechanical "shortening mechanism" operates to shorten the MLG shock strut and, at the same time, rotate the bogie to a perpendicular position so that it can fit into the hole.

N2

Reverser - well done!

N2 - sounds like a similar system. perhaps we are still building good airliners!

Dan,

Sounds good in theory but in practice this gear has been really problematic with the shortening mechanism one of the major sore points. Although they are working on it, I think it will remain the Achilles Heel of this gear system.

N2

i have noticed that the airbus a310 has the
gear tilted rear-wards on landing,
while the 767 has it tilted foward,
the a310 landing was much smoother.

ZK,

The A310 gear may appear tilted on approach but in reality the truck assy is maintained perpendicular to the shock strut by a self contained "Pitch Trim" actuator

N2