Ships Inertial Navigation System (SINS)

[Navy Chief]

Seems like I remember it was the ATs or AQs perhaps that used to deal with this system on the aircraft.

Anyone know? I recall them taking a cable from the catwalks (I think), and hooking it up to the aircraft.

Navy Chief

[Willy]

PRB might know. He's an AT.

[PRB]

Yep. The ship has an Inertial Navigation System (INS) just like the plane does. To align the plane’s INS, as was discussed in another thread a bit ago, the plane has to be stable, and you have to know your current position. This is a problem on a pitching, rolling, and moving carrier. So to align the airplane’s INS, you must provide the airplane with constant position data from the ship’s INS (SINS) during the entire alignment. Most of the time SINS data is broadcast over the airwaves, and can be simply received by the plane. But, when the ship needs to go “silent”, the only way to get SINS data is from the cable, which is indeed screwed onto a connector in the catwalk. In the A-7 the cable was connected to a connector in one of the main wheel wells. The INS system, and the SINS cable, was the AQ’s job.

[Navy Chief]

Yep. The ship has an Inertial Navigation System (INS) just like the plane does. To align the plane’s INS, as was discussed in another thread a bit ago, the plane has to be stable, and you have to know your current position. This is a problem on a pitching, rolling, and moving carrier. So to align the airplane’s INS, you must provide the airplane with constant position data from the ship’s INS (SINS) during the entire alignment. Most of the time SINS data is broadcast over the airwaves, and can be simply received by the plane. But, when the ship needs to go “silent”, the only way to get SINS data is from the cable, which is indeed screwed onto a connector in the catwalk. In the A-7 the cable was connected to a connector in one of the main wheel wells. The INS system, and the SINS cable, was the AQ’s job.


Thanks PRB,

I knew I'd get an answer quick! Seems like the SINS cable was fairly hefty, if I recall correctly.

NC

[PRB]

Yes, we hated those things! If the cable wouldn't reach the plane, we had to connect two of them together, which was twice the fun!

[PRB]

A cool SINS story. I was on Enterprise (CVN-65), the top speed of which was, and remains, classified. Well, when aligning the INS aboard the ship, you could use the computer to monitor SINS data, which included speed… On several occasions, when it seemed we were going really fast, and it was convenient, I would tune in the SINS data. Because most of the time, the ship was always broadcasting SINS data… Well, on those occasions that I tried to use it to see how fast we were going, because it seemed we were hauling a**, they always quit broadcasting SINS data! :cool:

[strikehawk]

A cool SINS story. I was on Enterprise (CVN-65), the top speed of which was, and remains, classified. Well, when aligning the INS aboard the ship, you could use the computer to monitor SINS data, which included speed… On several occasions, when it seemed we were going really fast, and it was convenient, I would tune in the SINS data. Because most of the time, the ship was always broadcasting SINS data… Well, on those occasions that I tried to use it to see how fast we were going, because it seemed we were hauling a**, they always quit broadcasting SINS data! :cool:

I was a Grape on the Saratoga in 79-81 and to use the SINS you also had to use deck edge power. Since most birds at the time with the exception of the S-3 needed D/E power to take fuel we had priority on any and all power cables during flight quarters. You want to see an AT or AQ come unglued? Tell him that he has 30 seconds to shut down and give up his power cable, when he gives you the finger have the Plane Captain dis-connect it. Those guys would leap out of the 'pit of an A-6 to get at you. Sometimes they'ed have a go at you, but most Grapes were borderline crazy so the fights were few.

And yes I know what happens when you pull power before you shut the system down. I got tossed from AV "A" school a few weeks before graduation. You didn't think I'd go to school to be an AB did you?:eek:

[Bone]

Really interesting stuff, guys. I wonder why the cable needed to be so hefty? Since the SINS position data could also be broadcast, what could be so complex about it that a smaller cable couldn't do the trick? Maybe it just needed to be built like a tank for protection, after reading about those crazy Grapes.

[PRB]

That’s funny, strikehawk. I remember moments like that!
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Bone, the cable was about an inch in diameter, coax. Not sure why it was made that big. Probably, as you said, for durability. It wasn’t heavy if you just had ten feet of it to deal with, but that darn cable must have been over a hundred feet long. All coiled up, it was pretty heavy. Not so bad though. Heck we had to complain about something!
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One thing about broadcast vs. cable SINS, the cable data was much more reliable. The broadcast signal was always getting interrupted, and dropping off for a second here, and a second there, resulting in a potentially long alignment time. That was never an issue if you had the cable plugged in, since it was shielded.