My students didn't believe me... by raistlin

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... when I gave them this simple explanation as to how inertial navigation works.

Note, Podge and John et al, will already know this in one form or another.

This text was originally transcribed from a US Navy training film.

Aircraft Inertial Guidance Systems

The aircraft knows where it is at all times. It knows this because it
knows where it isn't, or wasn't. By subtracting where it is from where it isn't, or wasn't,
or where it isn't from where it is (whichever is the greater), it
obtains a difference, or deviation.

The Inertial Guidance System uses deviations to generate error signal
commands which instruct the aircraft to move from a position where it
is to a position where it isn't, or wasn't arriving at a position where it
wasn't, or now is, or isn't. Consequently, the position where it is, is now the
position where it wasn't; thus, it follows logically that the position
where it was is the position where it isn't, or possibly wasn't.

In the event that the position where the aircraft now is, is not the
position where it wasn't, the Inertial Guidance System has acquired a
variation. Variations are caused by external factors, the discussions
of which are beyond the scope of this report.

A variation is the difference between where the aircraft is and where
the aircraft wasn't, or was it isn't. If the variation is considered to be a factor of
significant magnitude, a correction may be applied by the use of the
autopilot system. However, use of this correction requires that the
aircraft now knows where it was because the variation has modified
some of the information which the aircraft has, so it is sure where it
isn't, or wasn't.

Nevertheless, the aircraft is sure where it isn't (within reason) and
it knows where it was. It now subtracts where it should be from where
it isn't, where it ought to be from where it wasn't (or vice versa)
and integrates the difference with the product of where it shouldn't
be and where it was; thus obtaining the difference between its
deviation and its variation, which is variable constant called

Then I started the real lecture... and they thought the above was perfectly simple in comparison ;)

Cogito ergo sum... maybe?

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Posted 01 Mar 2011, 19:52 #1 

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(Site Admin)
Python sketch ?

Posted 01 Mar 2011, 20:22 #2 

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ooo me brain 'urts :?

Posted 01 Mar 2011, 20:29 #3 

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Mick wrote:Python sketch ?

No, apparently it really was a transcript from a US Navy training film, although modified and added to now I daresay.

Gives the students a laugh anyway :lol:

Cogito ergo sum... maybe?

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Posted 01 Mar 2011, 20:37 #4 

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ah I see.
So now we know why US pilots can't identify us and them...
The aircraft thinks it's where it isn't. Or isn't where it was...

Lordy me, back in my days in the RAAF we only had simple rules to remember.

1) You can never have too much altitude. ( Unless you are on fire )

2) Every landing is only a controlled crash.

3) A succesful landing is one where the outgoing crew can use the same aircraft.

4) As Captain you get to choose who does what. If it is a very sunny ay I will do the outside pre flight checks while you sweat it out in the cockpit. Or vise versa, if it is pissistantly raining, you do the outside checks while I am in the cockpit.

5) Try not to land with the parking brake on. Easy to tell if you have. There is a horrible noise closely followed by a series of loud bangs as the tyres go.

6) Unless you are stationary, ground is is good.

7) If you get warning sirens and lights going off while in the air, turn them off. They are very distracting when you are panicking anyway.

and finally......and I have very nearly done this....
Never, but never open the rear loading ramp without telling somebody in the load bay !

my chariot from back in the day.....
DH Caribou. The only fixed wing aircraft to ever suffer a bird strike from the rear .

Posted 04 Mar 2011, 12:34 #5