levg79
Posts: 918
Joined: Sat Sep 27, 2003 10:59 am

Controls For Taxi

Sat Sep 27, 2003 11:53 am

Hey guys,

Please don't make fun of a new airplane fan, but I was just wondering if anyone could tell me how the pilot controls the airplane while he taxies to the runway or back to terminal.

Does the pilot use rudder pedals or yoke to turn the wheel? Or is there another way of controlling the direction while on the ground? Any help would be appreciated.

A mile of runway takes you to the world. A mile of highway takes you a mile.
 
flyboyaz
Posts: 2077
Joined: Sat Sep 13, 2003 11:32 am

RE: Controls For Taxi

Sat Sep 27, 2003 11:57 am

It's a good question! They use the rudder mostly and on large planes, like commercial airliners, they also stear the nose wheel. Most smaller planes simply use the rudder pedals.
Catch a ride on a smile!
 
levg79
Posts: 918
Joined: Sat Sep 27, 2003 10:59 am

RE: Controls For Taxi

Sat Sep 27, 2003 12:12 pm

Then the next question would arise....what do they use to steer the nose wheel? Is there something similar to a steering wheel hidden in a cockpit?

P.S. Please don't make fun of my stupid questions.
A mile of runway takes you to the world. A mile of highway takes you a mile.
 
goboeing
Posts: 2428
Joined: Mon Jun 05, 2000 5:31 am

RE: Controls For Taxi

Sat Sep 27, 2003 12:16 pm

There is a steering "tiller" in the large jets. It's a wheel on the captains side if you see any cockpit pictures. It steers the nosewheel to the full turning capability. The rudder pedals only steer up to about 10 degrees I've been told.

Nick
 
Guest

RE: Controls For Taxi

Sat Sep 27, 2003 3:08 pm

In the 747, both captain and co pilot have a "steering wheel" (tiller)... there were other airplanes with the option of installing a tiller on the co-pilot side. I have seen a few 707s so equipped...
xxx
A reduced amount of steering (5 degrees, L and R) can be obtained in most airplanes (for takeoff and landing) through steering with rudder pedals, but tight turns for taxi require use of the steering tiller...
xxx
(s) Skipper
 
zak
Posts: 1926
Joined: Mon Sep 22, 2003 12:17 pm

RE: Controls For Taxi

Sat Sep 27, 2003 4:35 pm

On this picture, the airbus tiller is visible left of the sidestick.

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Click here for bigger photo!

Photo © Florian Kondziela

10=2
 
Spitfire
Posts: 697
Joined: Sat Feb 17, 2001 2:16 am

RE: Controls For Taxi

Sat Sep 27, 2003 7:52 pm

For your info, the round "knob" on top of the tiller is there to diconnect the rudder pedals input to the nose wheel while performing the "rudder check" (...feet full left then full right) during the flight controls check on the ground (during taxi).

Rgds
Spitfire

[Edited 2003-09-27 12:53:53]
Sabena ... Never to be forgotten (12 years already , what a shame !! )
 
suspen
Posts: 151
Joined: Tue Aug 05, 2003 11:01 pm

RE: Controls For Taxi

Sat Sep 27, 2003 8:15 pm

Levg79, they aren't stupid questions. Welcome to the forum.  Big thumbs up

Now I'm curious too. I thought some jets also used differential thrust for taxiway turning, but no one has mentioned it yet. Is that only used for "emergencies", or not at all?
Tower: "Cessna xxxx, state your intentions", Cessna: "To become airline pilot"
 
CX Flyboy
Posts: 6007
Joined: Sun Dec 26, 1999 6:10 pm

RE: Controls For Taxi

Sat Sep 27, 2003 8:52 pm

Levg79,

Remember that when most people reply, they are referring to specific aircraft. Don't get the idea it is the same for all aircraft.
On the 777, we have a tiller both for the Captain and FO. We usually use the tiller to steer the aircraft, however above 20kts taxying on long straight taxiways, we use the rudder. As others have mentionned, the rudder can only move the nosegear a limited number of degrees, whereas the tiller is quite sensitive and can turn the nosewheel a good 60 degrees or more. (68 seems to ring a bell but I'm probably wrong). On long straights, using the rudder means more gradual corrections to following the centreline instead of jerky movements with the tiller.
When doing the control check, the tiller is still connected to the nosegear so the rudder pedals will fight the tiller. To counteract this, we simply hold the tiller tightly when checking the rudder during taxi. If the tiller does not swing left and right with the rudder, the aircraft will not swing from side to side either.
 
tarzanboy
Posts: 124
Joined: Fri Sep 12, 2003 8:18 am

RE: Controls For Taxi

Sun Sep 28, 2003 11:31 am

skipper....

on other large crafts,,,,as well as the 747....how does the pilot avoid running off the taxiway wen he is making turns, like 90 degree turns?

how is he trained, or wat procedure is taught to avoid this mishap..and stay on the pavement...?
 
747Teach
Posts: 176
Joined: Wed Nov 29, 2000 3:05 am

RE: Controls For Taxi

Sun Sep 28, 2003 12:05 pm

Levg79: As others have said, most large aircraft have some sort of tiller or wheel to steer the nose strut while taxiing. A little differential thrust from the engines may help you, especially on tight turns. Seems to work a bit better on planes with wing-mounted engines. In this photo of a DC-9 cockpit, you can see the steering wheel on the left side.
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Click here for bigger photo!

Photo © Michael Carter

The round knob in the middle of the steering wheel sets and releases the parking brake. And you might be interested in knowing that on the 747 aircraft, when you steer the nose strut to the left, for instance, the body gear will steer slightly in the opposite direction (to the right) to prevent wheel scrubbing. Regards,
 
covert
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Joined: Sun Oct 21, 2001 1:02 am

RE: Controls For Taxi

Tue Sep 30, 2003 5:36 am

For the inexperienced, can the taxi process be likened to learning how to drive?
none
 
Guest

RE: Controls For Taxi

Tue Sep 30, 2003 6:54 am

Surprisingly to many, flying the 747 is extremely easy (very stable aircraft) but learning to taxi a 747, is not "that easy"...
xxx
Most pilots I train in the 747 come from other airplanes that are much "smaller" in size... I sometimes compare, that taxiing a 747 is like driving a "semi-truck" 18 wheeler (we have 18 wheels as well) and you have to "think" where you main gear "is" when making tight turns on taxiways...
xxx
I even sometimes teach taxi to ground engineers (mechanics) - we have a few mechanics who are qualified to taxi the 747...
xxx
Taxi in turns is not that easy with 747... if you nearly "stop" the aircraft, you are losing "inertia" momentum... and get quasi "stuck", requiring a lot of power to move again. I personally recommend a little extra power on the outboard engine (of the turn direction) to help... Taxi speed limitations in a 747 are (policy) 20 knots and 10 knots (or slower) in turns... think about your passengers in the rear if you "swing the tail" rapidly... very uncomfortable.
xxx
By the way, "steering on the runway" (nosewheel effectiveness) is as effective as a piece of "wet Kleenex"... the steering WOULD NOT HELP, if an outboard engine should fail... It is all in the "rudder" and "L/R" differential power... forget the steering, except to align yourself on the runway.
xxx
PanAm, by the way, disconnected the link, between the 747 rudder pedals, and the nosewheel steering system, since the 707 they were accustomed to, did not have a steering feature on rudder pedals...
xxx
Happy contrails  Smile
(s) Skipper
 
Guest

RE: Controls For Taxi

Tue Sep 30, 2003 7:04 am

Just an observation...

On nearly every Jet I've flown the biggest challenge facing the new pilot was learning how to taxi smoothly, without spilling the coffee and drinks in the back. In flight they're easy (and smooth) on the ground, well that can be an whole nuther story. Whether the problems are caused by sheer mass (B747), steering sensitivity, or touchy (grabby) brakes the results are the same.

Jetguy
 
ConcordeBoy
Posts: 16852
Joined: Thu Feb 01, 2001 8:04 am

RE: Controls For Taxi

Wed Oct 01, 2003 5:07 am

think about your passengers in the rear if you "swing the tail" rapidly

Hmm.... "swing the tail" you say?  Big grin
Faire du ciel le plus bel endroit de la terre c'est impossible sans Concorde!
 
meister808
Posts: 924
Joined: Sat Jan 01, 2000 11:45 am

RE: Controls For Taxi

Wed Oct 01, 2003 5:37 am

Well... thats a great video clip.

-Meister
Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation
 
POSITIVE RATE
Posts: 2121
Joined: Sun Sep 16, 2001 11:31 am

RE: Controls For Taxi

Wed Oct 01, 2003 12:20 pm

Just a question in relation to the steering tiller. Is it directly connected to the nosewheel via hydraulics or is it electronically connected and simply sends a signal to move the nosewheel??
 
Guest

RE: Controls For Taxi

Wed Oct 01, 2003 12:48 pm

It depends upon the specific aircraft, I've flown aircraft with 3 different types - electric, hydraulic, and also direct (cable).
 
Spitfire
Posts: 697
Joined: Sat Feb 17, 2001 2:16 am

RE: Controls For Taxi

Wed Oct 01, 2003 7:37 pm

Positive rate,

It is electronically connected on Airbus A320, A330 and A 340. Then via a computer ( BSCU - for Brake and Steering Control Unit, there is two off them onboard), the nose wheel is hydraulicaly actuated ("Green" hydaulic circuit).

Rgds

Spitfire

[Edited 2003-10-01 12:50:19]
Sabena ... Never to be forgotten (12 years already , what a shame !! )
 
gordonsmall
Posts: 2106
Joined: Sun Jul 01, 2001 1:52 am

RE: Controls For Taxi

Thu Oct 02, 2003 1:30 am

Spitfire,

Is the steering control linear? Or does the nosegear deflection vs tiller deflection depend on speed or other factors?

Regards,
Gordon.
Statistically, people who have had the most birthdays tend to live the longest.
 
Spitfire
Posts: 697
Joined: Sat Feb 17, 2001 2:16 am

RE: Controls For Taxi

Thu Oct 02, 2003 9:27 am

Sorry Gordonsmall that I can't post here a diagram coming from the Airbus FCOM. I'll try to explain...

Nose wheel steering angle varies in fonction of the ground speed. Up to 10 kts, you have 78 degrees available. Then from 10 kts to 30 kts the angle decreases from 78 to about 40 degrees. And from there ( from 30 kts to 100 kts), down to zero. That's for the input of the "manual" steering.
Concerning the rudder input, you have 6 degrees from 0 to 40 kts and then, down to zero up to 100 kts ( the rudder takes over).

All this for Airbus A330 and A340.

Rgds.

Spitfire
Sabena ... Never to be forgotten (12 years already , what a shame !! )

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