What's the pin for?

"Mxsmanic" wrote in message
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.

Typically the rudder pedals provide about 8 degrees of nosewheel turning in
either direction. The tiller is used when when sharper turning is needed.

D.

Paul Tomblin wrote:
In a previous article, Mxsmanic said:

What does it mean when the crew of an aircraft look for "the pin" held by the
ground crew after pushback?


It disables the reset button.



that's flippin funny.
too bad someone actually responded seriously.

Tim writes:

too bad someone actually responded seriously.

Yes ... why interrupt sophomoric jokes with serious discussions of aviation?

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On Mar 13, 5:39 pm, Bob Moore wrote:
Mxsmanic wrote

What does it mean when the crew of an aircraft look for "the pin" held
by the ground crew after pushback?

They are looking for the Nose Gear Ground Locking Pin to insure
that it has been removed prior to flight. If not, the nose gear
will not retract.

Bob Moore
ATP B-707 B-727

In the Navy the pins also cause the gear to be rigid so it doesn't
sway when the ship does. I remember once an A-7 arrived without the
pin in its normal on-aircraft storage place, there was a mad search to
find it. The concern was it may have fallen out of the storage and
fallen onto someone on the ground. Turns out some line guy on the ship
had forgotten to put it in where it was suppose to go, it was later
found hidden in his locker.

-Robert

Most fighters and bombers also have arming safety pins too.



"PapaGeorge" wrote in message
nk.net...
| Most fighters have three pins...both mains and nose gear.
PapaGeorge
|
| "Bob Moore" wrote in message
| 6.128...
| Mxsmanic wrote
| What does it mean when the crew of an aircraft look for
"the pin" held
| by the ground crew after pushback?
|
| They are looking for the Nose Gear Ground Locking Pin to
insure
| that it has been removed prior to flight. If not, the
nose gear
| will not retract.
|
| Bob Moore
| ATP B-707 B-727
|
|

On Mar 13, 10:18 pm, Mxsmanic wrote:
I thought aircraft usually had interlocks that would prevent gear from
retracting as long as they had weight on them.

The "squat switch" interlocks people usually speak of are to prevent
the gear control from being used with weight on the wheels. Nothing
to do with actually mechanically holding the gear down.

Many gear are designed so, yes, they tend to stay in place by
themselves. But put a tug on the front wheels, and you could push
the gear out of place.

Some planes, for example the Airbus, also depend on powered hydraulics
as a separate aid to holding the gear in place. They suggest that
pins be put in place if a tug is used to move an unpowered plane (such
as for maintenance).

Kev

"Jim Macklin" wrote in message
...
Most fighters and bombers also have arming safety pins too.

That is correct. I was an Aviation Ordnance man.. Worked on A4b Skyhalks..
Guess that is showing my age.

You could play little tricks with the pins.. None of us ever wanted to be on
recovery for night ops.. If any ordnance came back, it could not be brought
back to the mags at night. We would have to post a watch on the trailer.

Pull the pin on the bomb rack when arming and gauranteed no bombs coming
back.

Probably the most inportant pin was in the pilots ejection seat. It was an
added safety feature. The landing gear alone should have disabled ejection.
but.... At NAS Jacksonville.. A guy playing around in the cockpit pulled the
ejection curtain with plane in the hangar, without the pin in. He made quite
a splash on a 50 foot high hangar ceiling. So saftey features always don't
work. All aviation rules are written in blood they say.. So if a pin should
be in. put it in.

Kev writes:

Some planes, for example the Airbus, also depend on powered hydraulics
as a separate aid to holding the gear in place.

Somehow that doesn't surprise me.

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"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.

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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

Scet wrote:

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


The DC-3 has no nose gear, but you pin the mains (not necessary to do
anything for the little guy in the back).