"Mxsmanic" wrote in message
...
Capt.Doug writes:

The gear pins mentioned by others here are usually removed by pilots or
mechanics well before pushback for flight. The pin that the pushback crew
holds up is the steering by-pass pin. Without the pin in place, the
towbar
is free to swing with the nose wheel steering and could cause serious
injury
to persons and equipment. The pin is held up for the pilots to see so
that
the pilots know they will have steering before they start taxiing.
Additionally, at my airline and at United, the nosewheel steering is
turned
off in the cockpit because the steering may swing momentarily during
electrical power transfer as the engine-driven generators come online.

Thanks for the detailed answer. I was also able to look up "bypass pin"
after
reading your reply and got some additional detail ("pin" alone was too
general).

What's the relationship between the tiller and the rudder when it comes to
steering? I understand that most large aircraft have a separate tiller
wheel
that can be used to turn the nose gear on the ground, but it also seems
that
the rudder turns the gear, too (?), at least during landing and take-off.
What determines the interaction of the two? There doesn't seem to be any
cockpit control that governs how they work in the aircraft I've studied.

--
Transpose mxsmanic and gmail to reach me by e-mail.

This can be gear pins on some aircraft, but will normally be all the pins
not just the nose.

Some aircraft have towbars (they are usually aircraft specific on large
aircraft) that will disengage the steering mechanism when properly engage.
An integral locking pin usually has to be pulled out of the way by hand tp
prevent inadvertant actuation of the disabling mechanism.

With some aircraft, the nose wheel steering wheel is used during normal taxi
operations and to maintian centre line during take off untill around 80kts
when the rudder is effective enough to do the job. The nose of the aircraft
is usually getting too light at this stage and becoming non effective.

Some aircraft landing gear are configured so as to have a rearward rake
about them. This means that to retract the gear it has to lift the aircraft
over centre to retract the gear. Some have a rigid link connected to the
strut scissor links and when the strut is compressed with weight on wheels,
the link is pushed upward and causes a hinged locking collar to pivot down
and prevent the retraction actuator from breaking the over centre down lock,
which may also have un undercarriage safety pin inserted through the area
that it breaks at. AP-3Cs have all three and if an under carriage line is
replaced or something else minor, like an uplock release cylinder, it can be
leak checked by selecting the under carriage up and down without fear of
retracting the gear. It sounds a bit louder than a household tap (fawcet)
being turned on then suddenly turned off.

The old Sabre fighter jets, like Kirk Olsens, had a button that would
retract the gear on the ground if the brakes failed. The seat, if I remember
rightly, wasn't much use on the ground.

Scet

Scet