Thanks Mike, a good descriptio0n. I worked on Cf104s back in the 60s with
the LN3. Often we had terminal errors of 20+ miles after a 11/2 hr flight -
if the platform remained erect.
I have worked witht eh latest Litton and Honeywell commercial RLG based
platforms and indeed they provide a very nce package in a Falcon 900Ex of
Global Express
Gary W
"Mike Kanze" wrote in message
news
Gary,

I was intersted to hear that the alignments would go "south" during the
catapult stage. Did air alignments work out ok as I realize you were
getting
lat/long info from another aircraft but can't imagine having the time to
carry out the process.

In the early 1970s A-6A, inflight alignments of the AN/ASN-31 inertial
navigation system were both common and more often than not "reasonably"
accurate - at least for providing a stable reference of aircraft heading,
attitude, and horizontal and vertical velocities. The A-6A/B/C NATOPS
referred to these as "rough alignments".

("Reasonably accurate" = accurate enough to complete the mission
successfully.)

An inflight alignment of the ASN-31 required true heading (which one got
from the magnetic wet compass and then adjusted for local magnetic
variation), aircraft velocity and the latitude of the inflight alignment
starting point. B/Ns made it a point to write down the ship's current
LAT/LONG during shipboard (SINS) alignments, since the cat shot was the
most
likely flight phase for an inertial dump and the inflight alignment could
be
started almost immediately after launch.

Entering the LONG in addition to the other three parameters above usually
produced a fix for the inertial accurate to +/- 3 to 5 miles, depending
upon
the distance traveled by the ship between SINS alignment and inertial
dump.
(There was also a fair amount of dead reckoning thrown in here as well,
using inputs like ship's estimated course and speed changes since SINS
alignment.)

In the A-6A, the real keeper of position was the AN/ASQ-61 ballistics /
nav
computer and not the ASN-31. It obtained its initial reference from the
ASN-31's aligned position, and took as inputs throughout the flight the
velocities generated by the ASN-31. The ASQ-61 also took inputs from the
aircraft's pitot-static system, radars, and the knobology activities of
the
crew.

During the mission the crew would update the ASQ-61's position with fixes
off the search radar, or visually if crossing a known position like the
CIP.
These updates minimized computed position errors.

At least that was how it was SUPPOSED to work. g

As Woody and others point out things are much different today, especially
the need for accurate posit inputs into the smart weapons we didn't have
back in the early 1970s.

--
Mike Kanze

436 Greenbrier Road
Half Moon Bay, California 94019-2259
USA

650-726-7890

"When was the last time in world history in which 'suicide' and
'martyrdom'
were the code of enlightened action admired by any society?"

- Roy Fassel (WALL STREET JOURNAL, 10/27/03)


"Gary Watson" cf104@ihate spam.shaw.ca wrote in message
news:CHbpb.260660$6C4.185337@pd7tw1no...
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