Humor
Aircraft
Inertial Guidance System Simplified
"We are not sure who the author of the following article
is, however we feel that the article is one of the best, clearly
defined descriptions of the magic that resides withing the
aircraft's black boxes."
The aircraft knows where it is at all times. It knows this
because it knows where it isn't. By subtracting where it is from
where it isn'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, arriving at a
position where it wasn't, or now is. 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.
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. 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.
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 intergrates 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 "error".
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Updated 22 May 1997