AFa340-300E From France, joined May 1999, 2084 posts, RR: 25 Posted (14 years 11 months 1 week 4 days 20 hours ago) and read 4410 times:
I have noticed many aircraft have the rear part of their main landing boggies going down for the landing, so that only two wheels touch down, and then the rest of the boggy (two or four other wheels according to the aircraft type).
But for the 767, this seems to be the opposite (front part first, then the rest). Any reason behind this please?
Davinair From , joined Dec 1969, posts, RR:
Reply 3, posted (14 years 11 months 1 week 4 days 1 hour ago) and read 4274 times:
As requested by AFa340-300E i performed a search into the 767 landing gear issue. i have to admit what i read was interesting. but the answer is easer than all the answers given. the 757 and 767 were designed to meet two different modes of flight. 757 = "short range" 767 = "long range". when designing for these differnet modes of flight different things are important. range, fuel consumption, cargo capacity, etc. due to placement of the wing, needed cargo space, the desire to have the smallest wheel well as possible and the dedsire to keep the aircraft from tilting when its on the ground, boeing designed the landing gear to move forward on retraction on the 767. where on the 757 it moves aft. so think about it, if the gear needs to move forward the forward tires need to be down so when it is retracted the "boggies" will be inline with the fuselage. the same is true if the landing gear retracts aft (757). as a point of interest the 707 gear moves straight in to the wheel wells so it has no tilt.
Mech@lax From , joined Dec 1969, posts, RR:
Reply 6, posted (14 years 11 months 1 week 3 days 15 hours ago) and read 4234 times:
The 757, on landing and after the wheels leave the runway on takeoff, the aft MLG wheels have an aft tilt to them because there is no pressure on the tilt actuator. I forget the proper name of the actuator.
On gear retraction there is pressure to this actuator which straightens the wheels to a no tilt angle and this is how the wheels go in the hole (with no tilt).
On the 767 the wheels go in the hole just as you see in the pictures, with that FWD tilt.
Airgypsy From United States of America, joined Nov 1999, 130 posts, RR: 2
Reply 8, posted (14 years 11 months 1 week 2 days 22 hours ago) and read 4218 times:
Fit to the wheel well gets the cookie. The bonus is that when the gear front truck touches down, the torque from spin up cushions the touchdown of the rear truck. The "normal" types have to contend with slamming because the rear truck torque amplifies front truck touchdown. Watch a film of a 747 and cringe at the sight of it.