Why nosewheel tiller?
Guest
Posts: n/a
I'm not a professional pilot so I could very well be wrong about this but...
Surely one important reason is that you need separate control of the rudder and nosewheel when landing in a crosswind. Specifically, when you need to use the rudder to kick the a/c straight after a crabbed approach but you still need the nosewheel pointing straight down the rwy when you touch down.
Guest
Posts: n/a
Yes, but that could be controlled automatically couldn't it? Once the aircraft touches the ground nosewheel steering is gradually fed in.
Do airliners actually use the nosewheel for centerline guidance at > 100 kt? I think they use the rudder once it becomes effective.
Martin
Do airliners actually use the nosewheel for centerline guidance at > 100 kt? I think they use the rudder once it becomes effective.
Martin
Guest
Posts: n/a
The steering tiller is capable of turning the nose wheel quite a lot, 70 degrees on the B744, for taxiing. If the pedals were to be able to do this, the pedal travel for the few degrees of deflection needed on takeoff and landing would be next to none, making it nearly impossible to guide the a/c down the runway with any kind of precision.
Anyone know any other reasons?
Cheers,
/ft
Anyone know any other reasons?
Cheers,
/ft
Guest
Posts: n/a
Consider the Fairchild Metroliner and Merlin series of aircraft (SA226/SA227).
These aircraft have hydraulically powered, electrically controlled nose wheel steering capable of operation between 63 degrees left and 63 degrees right. Pilot inputs to the nose wheel steering include an on-off switch, a park switch, and the rudder pedals.
When the on-off switch is on, the pilot and co-pilot rudder pedals control the nose wheel steering, but full rudder pedal deflection can only call for a maximum of 10 degrees nose wheel deflection. This arrangement works well for normal taxing and for take offs and landings.
When the on-off switch is on, and the pilot holds down a push-on, momentary action park mode switch for a period of 12 seconds the maximum nose-wheel deflection is progressivly increased from 10 degrees to 63 degrees. This mode allows very tight turns and acurate parking, but would be far too sensitive for take-offs and landings. When the park mode switch is released the maximum nose wheel deflection is progessively reduced from 63 degrees to 10 degrees over a 12 second period.
Interestingly, on the SA226TC Metro II (which is 60 ft 6 inches long, but has a wing span of only 40 ft 6 inches) with 63 degrees nose wheel steering it is quite possible during a very tight turn to miss an obstacle with the wing tip, but clobber it with the tail. Its happened before, and no doubt will happen again.
These aircraft have hydraulically powered, electrically controlled nose wheel steering capable of operation between 63 degrees left and 63 degrees right. Pilot inputs to the nose wheel steering include an on-off switch, a park switch, and the rudder pedals.
When the on-off switch is on, the pilot and co-pilot rudder pedals control the nose wheel steering, but full rudder pedal deflection can only call for a maximum of 10 degrees nose wheel deflection. This arrangement works well for normal taxing and for take offs and landings.
When the on-off switch is on, and the pilot holds down a push-on, momentary action park mode switch for a period of 12 seconds the maximum nose-wheel deflection is progressivly increased from 10 degrees to 63 degrees. This mode allows very tight turns and acurate parking, but would be far too sensitive for take-offs and landings. When the park mode switch is released the maximum nose wheel deflection is progessively reduced from 63 degrees to 10 degrees over a 12 second period.
Interestingly, on the SA226TC Metro II (which is 60 ft 6 inches long, but has a wing span of only 40 ft 6 inches) with 63 degrees nose wheel steering it is quite possible during a very tight turn to miss an obstacle with the wing tip, but clobber it with the tail. Its happened before, and no doubt will happen again.
Guest
Posts: n/a
PolarMoosE
On the 744 the steering tiller is mainly used for taxiing and the line up. The tiller is able to turn the nosewheel up to 70 degrees in either direction.
For the take off roll, we use the rudder pedals, which are able to turn the rudder up to 7 degrees in either direction.
Further more during sharp turns on the ground(nose wheel steering angle exeeds 20 degrees), the body gear steering is activated when ground speed decreases through 15 knots. When speed increases through 20 knots, the body gear steering is deactivated, and the body gear is centered as well.
RGRDS
MP
On the 744 the steering tiller is mainly used for taxiing and the line up. The tiller is able to turn the nosewheel up to 70 degrees in either direction.
For the take off roll, we use the rudder pedals, which are able to turn the rudder up to 7 degrees in either direction.
Further more during sharp turns on the ground(nose wheel steering angle exeeds 20 degrees), the body gear steering is activated when ground speed decreases through 15 knots. When speed increases through 20 knots, the body gear steering is deactivated, and the body gear is centered as well.
RGRDS
MP
Guest
Posts: n/a
"Yes, but that could be controlled automatically couldn't it? Once the aircraft touches the ground nosewheel steering is gradually fed in."
That's all I need... another bl**dy computer to fix
Anyone heard of the KISS principle?
747-400 Avionics-fixer,
Q.
That's all I need... another bl**dy computer to fix
Anyone heard of the KISS principle?
747-400 Avionics-fixer,
Q.
Guest
Posts: n/a
"For the take off roll, we use the rudder pedals, which are able to turn the rudder up to 7 degrees in either direction."
Sorry to be exacting, but the 400 rudder fine steering system provides up to 7 degrees nosewheel steering with rudder pedal deflection - not 7 degrees of rudder.
Sorry to be exacting, but the 400 rudder fine steering system provides up to 7 degrees nosewheel steering with rudder pedal deflection - not 7 degrees of rudder.
Guest
Posts: n/a
The 747/744 has landing rollout control, an automatic function that alledgidly would guide the a/c down the centre line of the runway, it is obviously dependant on localiser accuracy, and a/c system fully operational. Once the a/c speed reduces below 80kts rudder pedal steering is available to deflect nosewheels as previously stated.
Guest
Posts: n/a
For what its worth on the A319/320/321 family the rudder pedals have 6 degrees of authority upto 40kts reducing to 0 degrees at 130kts, whereas the hand wheels have 75 degrees upto 20kts reducing to 0 degrees at 70kts. They are also capable of CAT 3B approaches with rollout guidance (ie automatic steering on the landing roll)
Guest
Posts: n/a
V2Climb, there is no reason why an aircraft can not take-off with yaw damper(s) engaged and still have pilot inputs to the hydraulic nose-wheel steering via the rudder pedals. This is in fact exactly how things are done on most FAR25 aircraft. Yaw damper rudder inputs are not an input to the rudder artificial feel units on any aircraft I know about.
The 146 does not have rudder pedal control inputs to the nose wheel steering for the same reason that it has so many other unique features...because it is english.
The 146 does not have rudder pedal control inputs to the nose wheel steering for the same reason that it has so many other unique features...because it is english.
Guest
Posts: n/a
BIK_116.80
Good post, but you finish with …because it is english…
BAe’s other four engined jet with unique features does have rudder pedal control input to the nosewheel steering, allowing ±10° nosewheel travel, compared to ±60° nosewheel travel available from the handwheel.
Electrically controlled, hydraulically operated, autostabilization system engaged from start of taxy out……works like a dream.
[This message has been edited by Bellerophon (edited 06 February 2001).]
Good post, but you finish with …because it is english…
BAe’s other four engined jet with unique features does have rudder pedal control input to the nosewheel steering, allowing ±10° nosewheel travel, compared to ±60° nosewheel travel available from the handwheel.
Electrically controlled, hydraulically operated, autostabilization system engaged from start of taxy out……works like a dream.
[This message has been edited by Bellerophon (edited 06 February 2001).]
Guest
Posts: n/a
Mustafagander--
Actually, it is the "parallel" yaw dampers that should be switched OFF for takeoff and landings, series remain ON at all times (at least on the B707). Hibred types, like the L1011, series for all flight ops except at A/L track where it switches to parallel for runway alignment. Recently delivered a TriStar on its last flight before being parted-out. Even though it had not had a gold-wire check in years, the Approach/Land
function worked perfectly with centerline displacement of no more than about six feet.
Actually, it is the "parallel" yaw dampers that should be switched OFF for takeoff and landings, series remain ON at all times (at least on the B707). Hibred types, like the L1011, series for all flight ops except at A/L track where it switches to parallel for runway alignment. Recently delivered a TriStar on its last flight before being parted-out. Even though it had not had a gold-wire check in years, the Approach/Land
function worked perfectly with centerline displacement of no more than about six feet.
Guest
Posts: n/a
411A, yes afraid you are right, mate. The intricacies of early pure-jet 707s are a little before my time. Are you suggesting that some early 707s had yaw dampers in parallel with the rudder pedals such that the rudder pedals moved with the yaw damper?
And, mustafagander, can you enlighten us as to why it is that the Saab 340 yaw damper must be off for take-off? Is it because the yaw damper provides inputs to a rudder artificial feel unit or for some other reason?
And, mustafagander, can you enlighten us as to why it is that the Saab 340 yaw damper must be off for take-off? Is it because the yaw damper provides inputs to a rudder artificial feel unit or for some other reason?
Guest
Posts: n/a
BIK_116.80
Yes indeed, on the early B707 aircraft with a parallel yaw damper, the rudder pedals moved with the inputs from the yaw damper unit. It was normally switched OFF at 1000 feet AGL before landing and ON after flap retraction on takeoff. If it was a gusty day, these early aircraft were a real handful due to their dutch-roll tendencies. They were rather ah....unstable, to say the least.
Yes indeed, on the early B707 aircraft with a parallel yaw damper, the rudder pedals moved with the inputs from the yaw damper unit. It was normally switched OFF at 1000 feet AGL before landing and ON after flap retraction on takeoff. If it was a gusty day, these early aircraft were a real handful due to their dutch-roll tendencies. They were rather ah....unstable, to say the least.