INS Alignment at Sea

How is the INS aligned at sea on a carrier that is moving at 30kts?
Actually it was quite a challenge.

I was AEAN Flight Deck Troubleshooter assigned to VAW-116, launching the
E-2C Hawkeye off the pointy end of the USS Constellation during the WestPac
of 80-81 when we had to do a "handset align" of INS. We all stood around in
a semi-circle (to keep dumb****s from walking thru the turning props) and
when given the signal, I'd go into the island, call SINS and get our PP
(present position). Then I'd go up into the cockpit where they already had a
"rough align" and tell INS where we were. Of course we were just doing
doughnuts out in the middle of the IO. This was called a "handset align" and
was very common when SINS would not transmit via the cable and when an RF
Align was not possible (like during EMCON).

I've been in the cockpit of the Hawkeye (parked abreast the island) and seen
the ground speed display 42 knots- we were HAULING! When they lit up all the
boilers all four screws would really kick up a rooster tail.

I had a ball on the two WestPac's I did aboard the Connie- that was a great
ship with an even better crew :-)


--
Larry
AECS (AW/SW/MTS)
Disabled Combat Veteran
USN Retired

20 years of Navy in my rear view mirror
and getting further away every day ;-)

"Gary Watson" cf104@ihate spam.shaw.ca wrote in message
news:yyWob.251407$pl3.192778@pd7tw3no...
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

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

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.

In the days of the A-6A and its AN/ASN-31 inertial, shipboard alignments
were sometimes colorful and problematic affairs. There were none of the
goodies like RF links or GPS for us to play with.

Mini-sea story #1: On CORAL MARU's 1973 cruise, we (VA-95) found that (1)
most of the SINS cables were beat to hell and wouldn't work because (2) our
predecessor A-6 squadron in CVW-15 - VMA(AW)-224 - didn't know what
alignments were. It took us most of the cruise to weed out and survey the
hopelessly irrepairable cables and gradually accumulate a set of reliable
and maintainable ones.

Mini-sea story #2: On 95's 1975 cruise (still with CVW-15 / CORAL MARU), an
A-6 launched off Taiwan for a penetration flight to exercise ROC air
defenses. The crew obtained an normal SINS alignment, launched (this time
without the all-too-common inertial dump on the cat stroke) and commenced
the penetration. The crew became quite concerned however when the CIP did
not appear at all at the time and configuration briefed. Quickly - and
correctly - determining that they were actually headed for the friendly
shores of the Peoples Republic, they 180ed and bustered back to Mother.
Cause of problem? SINS posit was 40 nm (yes, 40 nm!) in error.

(There is a lot more to this second story than just the above.)

Prurient trivia item #436: The control panel for the AN/ASN-31 is described
in the NATOPS manual as the "Erection Controller Panel".

Owl sends.
--
Mike Kanze

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

650-726-7890

"When I read about the evils of drinking, I gave up reading."

- Henny Youngman


"Doug "Woody" and Erin Beal" wrote in message
...
On 11/1/03 4:35 PM, in article yyWob.251407$pl3.192778@pd7tw3no, "Gary
Watson" cf104@ihate spam.shaw.ca wrote:
[rest snipped]

My 2 cents,,,basically the same as Larry's,,,on the Big 'E' IO in '84
and the Connie IO in '85 we had SINS cable inputs sometimes available
for our US-3's, (Miss Piggy), . Otherwise we would Link with our
ASW-25 (UHF) to get CAINS updated Lat/Longs for the LTN-72's.... our
CODS only had gyros and AHRS (Attitude Heading Reference System),
although we could hook up a RO-RO LTN-72, and an internal 500 gallon
fuel tank for long haul repo flights. (Had a very uneasy feeling
sitting in the cargo compartment with a frickin leaking JP-5 fuel
cell, on numerous flights from PI to Singapore to Diego Garcia, etc.)
I still believe the most cost effective system is a dual AHRS combined
with GPS for the best representation of SA and Navigating. This type
of setup would cost less than a quarter of the over redundant and way
too expensive Ring Laser Gyro INS (over 150,000 per unit) and GPS
sysytems that are predominant in the newer Hornets, Orions and
Prowlers.

On Sat, 1 Nov 2003 20:39:18 -0800, "Mike Kanze"
wrote:

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.

In the days of the A-6A and its AN/ASN-31 inertial, shipboard alignments
were sometimes colorful and problematic affairs. There were none of the
goodies like RF links or GPS for us to play with.

Mini-sea story #1: On CORAL MARU's 1973 cruise, we (VA-95) found that (1)
most of the SINS cables were beat to hell and wouldn't work because (2) our
predecessor A-6 squadron in CVW-15 - VMA(AW)-224 - didn't know what
alignments were. It took us most of the cruise to weed out and survey the
hopelessly irrepairable cables and gradually accumulate a set of reliable
and maintainable ones.

Mini-sea story #2: On 95's 1975 cruise (still with CVW-15 / CORAL MARU), an
A-6 launched off Taiwan for a penetration flight to exercise ROC air
defenses. The crew obtained an normal SINS alignment, launched (this time
without the all-too-common inertial dump on the cat stroke) and commenced
the penetration. The crew became quite concerned however when the CIP did
not appear at all at the time and configuration briefed. Quickly - and
correctly - determining that they were actually headed for the friendly
shores of the Peoples Republic, they 180ed and bustered back to Mother.
Cause of problem? SINS posit was 40 nm (yes, 40 nm!) in error.

(There is a lot more to this second story than just the above.)

Prurient trivia item #436: The control panel for the AN/ASN-31 is described
in the NATOPS manual as the "Erection Controller Panel".

Owl sends.

On 11/2/03 12:56 AM, in article ,
"user" wrote:

My 2 cents,,,basically the same as Larry's,,,on the Big 'E' IO in '84
and the Connie IO in '85 we had SINS cable inputs sometimes available
for our US-3's, (Miss Piggy), . Otherwise we would Link with our
ASW-25 (UHF) to get CAINS updated Lat/Longs for the LTN-72's.... our
CODS only had gyros and AHRS (Attitude Heading Reference System),
although we could hook up a RO-RO LTN-72, and an internal 500 gallon
fuel tank for long haul repo flights. (Had a very uneasy feeling
sitting in the cargo compartment with a frickin leaking JP-5 fuel
cell, on numerous flights from PI to Singapore to Diego Garcia, etc.)
I still believe the most cost effective system is a dual AHRS combined
with GPS for the best representation of SA and Navigating. This type
of setup would cost less than a quarter of the over redundant and way
too expensive Ring Laser Gyro INS (over 150,000 per unit) and GPS
sysytems that are predominant in the newer Hornets, Orions and
Prowlers.


Foodog,

Dual AHRS/GPS wouldn't meet some of the specs required--especially in the
z-axis velocities.

--Woody

Yeah good point for high performance aircraft, thanks for the
input....How about for Commercial Air, and military slowmovers?

On Sun, 02 Nov 2003 11:10:42 GMT, "Doug \"Woody\" and Erin Beal"
wrote:

On 11/2/03 12:56 AM, in article ,
"user" wrote:

My 2 cents,,,basically the same as Larry's,,,on the Big 'E' IO in '84
and the Connie IO in '85 we had SINS cable inputs sometimes available
for our US-3's, (Miss Piggy), . Otherwise we would Link with our
ASW-25 (UHF) to get CAINS updated Lat/Longs for the LTN-72's.... our
CODS only had gyros and AHRS (Attitude Heading Reference System),
although we could hook up a RO-RO LTN-72, and an internal 500 gallon
fuel tank for long haul repo flights. (Had a very uneasy feeling
sitting in the cargo compartment with a frickin leaking JP-5 fuel
cell, on numerous flights from PI to Singapore to Diego Garcia, etc.)
I still believe the most cost effective system is a dual AHRS combined
with GPS for the best representation of SA and Navigating. This type
of setup would cost less than a quarter of the over redundant and way
too expensive Ring Laser Gyro INS (over 150,000 per unit) and GPS
sysytems that are predominant in the newer Hornets, Orions and
Prowlers.


Foodog,

Dual AHRS/GPS wouldn't meet some of the specs required--especially in the
z-axis velocities.

--Woody

The dual AHRS/GPs updated types of systems work well in the slow movinn'
easy turning world of commercial air transport. I know the LTN 72, Carousel
IV spinning iron systems from aircraft such as the G-II and L1011 etc and
the RLGs are much much more reliable but this is not in the military
environment.

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.

BTW my interest is because I teach Nav systems to tech school students and
we were discussing INS and the need for a stable airframe for alignment. I
can now go back Monday and answer the question about aligning whilst the
aircrafme is moving. Thanks guys

Gary Watson



"user" wrote in message
...
Yeah good point for high performance aircraft, thanks for the
input....How about for Commercial Air, and military slowmovers?

On Sun, 02 Nov 2003 11:10:42 GMT, "Doug \"Woody\" and Erin Beal"
wrote:

On 11/2/03 12:56 AM, in article
,
"user" wrote:

My 2 cents,,,basically the same as Larry's,,,on the Big 'E' IO in '84
and the Connie IO in '85 we had SINS cable inputs sometimes available
for our US-3's, (Miss Piggy), . Otherwise we would Link with our
ASW-25 (UHF) to get CAINS updated Lat/Longs for the LTN-72's.... our
CODS only had gyros and AHRS (Attitude Heading Reference System),
although we could hook up a RO-RO LTN-72, and an internal 500 gallon
fuel tank for long haul repo flights. (Had a very uneasy feeling
sitting in the cargo compartment with a frickin leaking JP-5 fuel
cell, on numerous flights from PI to Singapore to Diego Garcia, etc.)
I still believe the most cost effective system is a dual AHRS combined
with GPS for the best representation of SA and Navigating. This type
of setup would cost less than a quarter of the over redundant and way
too expensive Ring Laser Gyro INS (over 150,000 per unit) and GPS
sysytems that are predominant in the newer Hornets, Orions and
Prowlers.


Foodog,

Dual AHRS/GPS wouldn't meet some of the specs required--especially in the
z-axis velocities.

--Woody

Whoa! A CVN at 42 knots? How many water skiers could she tow? What a wake to jump!
walt BJ

On 11/2/03 12:05 PM, in article CHbpb.260660$6C4.185337@pd7tw1no, "Gary
Watson" cf104@ihate spam.shaw.ca wrote:

The dual AHRS/GPs updated types of systems work well in the slow movinn'
easy turning world of commercial air transport. I know the LTN 72, Carousel
IV spinning iron systems from aircraft such as the G-II and L1011 etc and
the RLGs are much much more reliable but this is not in the military
environment.

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.

BTW my interest is because I teach Nav systems to tech school students and
we were discussing INS and the need for a stable airframe for alignment. I
can now go back Monday and answer the question about aligning whilst the
aircrafme is moving. Thanks guys

Gary Watson



Gary and Foodog...

With regard to slow movers...
AHRS/GPS would be no problem for slow-movers in my opinion--whether UAV or
domestic air carriers. I wouldn't want to take one overseas--and couldn't
legally in the North Atlantic in RVSM airspace.

With regard to USN INS's...

Occasionally, the mechanical gyroed IMU/INS would dump on the cat when the
alignment was weak or due to some mechanical or electronic glitch. 1/2 of
the time you could IFA it and get it back. In my experience, the ASN-139
RLG INS doesn't care about the cat stroke.

The mechanical INS's would also build insidious, non-obvious
errors--occasionally until they'd dump entirely. Then you could IFA them if
you had the time/airspace.

The RLG fails fast and fails totally if it's broken. It's seldom that
you'll get it back once it fails--unless you caused the failure yourself
(due to incorrect initial coords during the alignment or bad SINS data).

Accurate data (3-axis) is important for many things, but most importantly
for transferring nav data to weapons--especially some of the newer more
complex stuff.

--Woody

"WaltBJ" wrote in message
om...
Whoa! A CVN at 42 knots? How many water skiers could she tow? What a wake
to jump!

When Sadat got assassinated, we were in port in Venice. At dusk we weighed
anchor and made mega-neutrons enroute to the coast of Egypt. The Boat was
going so fast that you couldn't even stand in the catwalks. I don't know
what speed we were doing, but it's was as fast as I've ever experienced
onboard any ship.

__!_!__
Gizmo