On 11/1/03 4:35 PM, in article yyWob.251407$pl3.192778@pd7tw3no, "Gary
Watson" cf104@ihate spam.shaw.ca wrote:

I am conversant with commercial INS and old military INS (LN3) and know that
the best alignment occurs when the a/c is stationary. Now my question.
How is the INS aligned at sea on a carrier that is moving at 30kts? Does the
ground crew start an alignment below decks prior to bringing the a/c up for
a launch? Also does the Captain have to realign heading on the catapult to
ensure proper heading reference or is there a slaved compass system in naval
military fighters?

Gary Watson




Gary,

Navy aircraft have two alignment modes. One for shore-based alignments and
one for shipboard alignments. The shipboard alignments require Ship
Inertial Navigation System (SINS) data via either a cable or from an RF data
link. This gives a fairly high quality alignment--it even worked well on
the A-6's IMU/INS.

If for some reason (and it happens) you can't get SINS data, you can
manually enter the ship's present position, speed, heading, and your deck
spotting angle and set the INS up to perform an manual CV alignment.

In the EGI/GPS equipped F/A-18 if THAT doesn't work, you can get a GPS in
flight alignment (IFA) even on deck.

--Woody