View Full Version : Airliner nose wheel steering
Superpilot
7th Mar 2006, 13:47
Sorry for asking this embarrassingly simple question but I can't find an answer elsewhere.
On modern airliners, If you touch down on the mains (as you should), and keep the nose wheel of the ground as long as possible, kicking in right rudder, will the nose wheel also turn to the right? or will it only turn to the right if it is in contact with the surface? Also what happens if you have full right rudder in place, and the nose will touches the ground. Will the nose wheel stay straight until you release and then re-apply rudder?
Thanks
"or will it only turn to the right if it is in contact with the surface?" - correct (for 737 anyway)
"Also what happens if you have full right rudder in place" - you generally have more problems than nosewheel steering:) I really do not know the answer to that - on the 737 the steering only 'engages' with 'weight on' and whether it zeroes on engagement I know not.
Edit for typo
Jet II
7th Mar 2006, 14:40
All large commercial airliners have 'centering cams' built into the nose leg to ensure that when the leg is extended (ie in the air) the wheels are in the straight ahead position irrespective of rudder inputs.
When you put weight on the wheels then the steering will respond to rudder pedal inputs but only to a small degree (usually + or - 7 degrees) full steering travel is only achievable using the tiller.
The question is, JetII, if I understand it, what happens then, when the weight comes on and the rudder is put to neutral? Does the nosewheel get a commensurate turn input equivalent to full rudder deflection?
Having never landed with 'full rudder' I do not know:).
Jet II
7th Mar 2006, 16:52
The question is, JetII, if I understand it, what happens then, when the weight comes on and the rudder is put to neutral? Does the nosewheel get a commensurate turn input equivalent to full rudder deflection?
If you land with full rudder deflection away from neutral (can I suggest you try this trick when I am not on-board ;) ) then as soon as you have compression on the nosegear the nosewheels will position to 7 degrees off-centre. I would then assume that you would quickly centre the rudder pedals to keep the thing on the runway.:ok:
Just a bit off topic......
I read somewhere that the B52 has the ability to set the main gear at an angle to allow for 'crab' landings. Is this true?
Nosewheels in most modern TurboJet Transports will "center when the shock strut is extended as after liftoff when appreciable weight is removed from the strut. If this were not to occur, chances are when the gear is retracted and not centered, structual damage of some accord would certanly happen as gear attempts to stow in the underside of the bonnett. When the strut is fully extended, the steering mechanism is disconected when the centering mechanism is activated. Obviously, different models operate somewhat differently, however, same concept.
Cardinal
8th Mar 2006, 23:36
In my distinctly unmodern and small airliner (1900) this becomes an issue. The solenoid that disconnects the nosewheel steering is controlled by a squat switch on the left MAIN gear leg, and the steering has 30-ish degrees of authority. Thus at the moment of touch down the steering engages, even though the nose isn't on the ground yet. During a strong crosswind with lots of rudder input during derotation you are rewarded with an annoying swerve as your cocked nosewheel grabs the pavement at 80 knots or so. For a truly smooth x-wind landing you have to center the pedals the moment before the nosewheel touches.
Other annoyances - the props go into low pitch the instant the right main squat switch is satisfied, thus slamming the left main onto the runway if it wasn't already there. Since there's no spool-up time involved, it's as though reverse thrust on a jet was instantly applied with but one one gear leg on the ground. One big thud. Rant over.
L Peacock
10th Mar 2006, 19:14
If you're interested and if I remember correctly from my days on Tornado...
Gear extended with weight off wheels = nose wheel powered to centre
Main weight on nose weight off = free to castor
Nose weight on = fade in (2 secs I think) to full NWS authority.