744 Whiskey Compass limitations

[NSEU]

Just wondering if anyone had come across some pitch limitations for the whiskey compass on a 744. I'm assuming the ball is sitting on a pivot... and at certain pitch angles the ball is going to hit the glass or rear of the container. (Note: I'm not talking about magnetic field lines being at an angle at the poles).

Perhaps someone has one in a workshop... or sitting on a desk as a paperweight? :}

Thanks.
Rgds.
NSEU

[Spanner Turner]

From my 744 training notes: (my highlighting)

Characteristics
The standby magnetic compass is a sensitive instrument composed of
a circular heading indicator card having two parallel and horizontal
magnets. The card is floating in a liquid filled case and is free to
rotate and tilt. The liquid medium serves to dampen rapid movements
and oscillations of the compass.
The magnets align the compass with the earth’s magnetic lines of
flux. This rotates the compass card that is calibrated to show the
airplane heading relative to the earth’s magnetic field. The magnetic
heading of the airplane is read from the card against a fixed lubber
line.



From my 767 training notes:

It is a sealed, liquid
filled unit, with a circular indicator card that has two parallel and
horizontal magnets attached and free to rotate and tilt as the airplane
banks. The liquid medium dampens rapid movements and
oscillations.

Sorry I can't find an exact answer and alas, I'm not lucky enough to have one as a paperweight. :(

However, I once did a "barrell / aileron" roll in a simulator but didn't notice what the standby compass was doing!
:E :E

[forget]

This any good? HERE. (http://www.baseops.net/t44/I3102.doc)

Pitch limits.

A limitation imposed by a compass' construction is that the balancing bowl's pin, which is connected to a pivot point, only allows for, in most compasses, a pitch or bank of 18 degrees before the compass will touch the side of the casing. When the compass touches the side of the casing the freedom of the plane to rotate around the compass is lost and the compass becomes unreliable.

[NSEU]

Thanks, guys.
If the compass is simply a ball floating a bowl without a pivot point, I'd imagine it would rub against the sides and occasionally stick... unless airframe vibration unsticks it (although there shouldn't be much vibration on the 744).

I might have to observe it during an aircraft tow and see what it looks like during sharp turns. If it's on a pivot, depending on how good the damping is, it should imitate a pendulum. If not, it probably behaves like a balloon in a moving vehicle :P

Thanks.
Rgds.
NSEU

[olepilot]

...is this of interest? today, year 2009!

[forget]

Here's a sectioned diagram.

compass | flight | compass details | 1951 | 1575 | Flight Archive (http://www.flightglobal.com/pdfarchive/view/1951/1951%20-%201575.html)

olepilot ...is this of interest? today, year 2009!

Go away, and find something that may interest you. :bored:

[NSEU]

...is this of interest? today, year 2009!

It is if you've lost all main bus power due to water leaking into the Main Equipment Centre, have no ISFD and you're flying over the Pacific, hours away from the nearest suitable landing field.

[Graybeard]

Compass Variation, Deviation, acceleration and turning errors are all part of primary pilot training. Well, at least they used to be.

GB