View Full Version : 747 Undercarriage question.....
AlanM
18th Sep 2002, 21:13
Have a quick look at:
747 turning on to 27R (http://www.airliners.net/open.file/172630/L/)
...particularly the main fuselage landing gear.
Question: Do these bogies have a certain amount of "play" in them to allow them to trail and go left or right a few degrees?
As the aircraft has taxied on to the runway at a more perpendicular angle, it then swung around to the left, lining up.
Are those wheels in trail or is it an optical illusion?
Alan
BlueEagle
18th Sep 2002, 23:30
Taken from the Vol2 of the BoeingB747-400 manual:
"When the nose-wheel angle exceeds 20 degrees, the body gear turns opposite to the nose gear to reduce the radius of turn and reduce tyre scrubbing. When the nose gear angle is less than 20 degrees, the body gear remains centred. Body gear steering is activated when ground speed decreases through 15kts. As speed increases through 20kts, the body gear is centred and body gear steering is deactivated"
On the B747-400 body gear steering is automatic subject to the above conditions, on the earlier B747s it also required a switch on the flight deck to be selected in order for BGS to activate.
Hope that answers your question.
woftam
18th Sep 2002, 23:30
AlanM,
The body gear steering operates when the nose wheel steering angle exceeds 20 degrees.
Body gear steering is activated when the ground speed decreases through 15 knots and is deactivated when the ground speed increases through 20 knots.(-400)
The rear two wheels on this bogie are "steered" by two large hydraulic actuators powered by hydraulic system #1.
The system reduces tyre scrubbing and lets the A/C turn in a minimum radius.
Hope this helps.
Just noticed BlueEagle beat me to the punch.
We must have been typing at the same time.
Quick Draw McGraw!
AlanM
19th Sep 2002, 06:53
Lovely jubbly!
Thank you both for yr replies.
Alan
mustafagander
19th Sep 2002, 10:25
WOFTAM,
Are you sure that only the rear 2 wheels on the BLG turn, or is it the whole truck??
As I understand it, the whole truck turns opposite to the NLG.
Intruder
19th Sep 2002, 19:22
The entire body gear truck turns as a unit, and both trucks turn the same direction at the same time.
woftam
19th Sep 2002, 23:00
Yes,my mistake.
The whole truck turns.
:(
SuperRanger
20th Sep 2002, 02:58
as a matter of interest, the B777 also has main gear steering but in its case, only the 2 rear-wheel turns.
SR
Is that ALAN Marega from Airkenya? IF yes whats up give me calli will tell u all about the 747.
later big al