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I know that the F/A-18C is equiped with a rotary switch for inertial alignment. The switch has two positions, one for ground and the other for carrier operations. Leaving aside the GPS/GNSS, I wonder how is the alignment process in a moving vessel. I'm thinking in the old good days of Phantoms, A-4's and all other Navy aircrafts of the fifties and sixties where GPS was not yet implemented. How are vessel movement errors corrected?

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  • $\begingroup$ Beyond a certain point it's just plain hard. PBS did a documentary called "Carrier" where, among other things, they followed one exercise mission on the high seas and a half dozen planes ended up stuck in the sky for hours trying to land on the pitching deck. They kept sending up refuelling craft to keep the fighters airborne and the pilots made attempt after attempt, failing over and over until they finally all managed to land. $\endgroup$
    – J...
    Mar 15, 2022 at 15:20
  • $\begingroup$ @J... Were the refueling craft able to land easier than the other planes? Or were they sourced at long range bases rather than from the carrier? $\endgroup$ Mar 15, 2022 at 17:47
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    $\begingroup$ @MichaelRichardson Refueling craft have much greater endurance and range than fighters. They can land later or elsewhere. I don't recall all of the details of this particular incident- you can watch the show if you like. $\endgroup$
    – J...
    Mar 15, 2022 at 17:53
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    $\begingroup$ @MichaelRichardson More reading on it available here, under Night of the Pitching Decks. $\endgroup$
    – J...
    Mar 15, 2022 at 18:21

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The aircraft carrier has its own inertial navigation system, (SINS - Ship's Inertial Navigation System) and this information is transmitted to each individual aircraft INS by either cable or datalink.

From the EA-6B NATOPS flight manual of the Mid-1990s, pre-GPS era:

20.2.1.5 Carrier Alignment requires ship's movement information as well as present position. This information must be supplied by either SINS or manual entry. When a carrier alignment is called for, the system checks that the data link is on. If this is true it is assumed that an automatic alignment is intended. If the data link is off or in test a manual alignment is assumed. The CDI then provides cues for the type of intended alignment that is assumed.

From there it goes into more detailed procedures. There is no information about preferred use of UHF data link vs cable other than a mention that on the CDI (Control Display Indicator) there will be an indication of either "CV UHF" (data link) or "CBL" if alignment information is being received via cable.

Most times at man-up the plane captains will have the alignment started, or the front seat NFO would start the alignment during preflight. Use of either UHF Data link or cable depended mainly parking location and number of available cables at that location, and speed/reliability of the UHF signal. Generally the split was random, and 50/50.

CV Manual alignments were least common, least desired, and only performed when SINS information was not available. They required more work making manual inputs, (of which ship's heading would need to updated if the ship was turning into the wind for launch, which it always did!) took longer, and they were less accurate.

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  • $\begingroup$ Do you have a source for this? I'm wondering when it was implemented. $\endgroup$ Mar 13, 2022 at 17:48
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    $\begingroup$ I just added amplifying info from my flight manual of the 1990s. Are you asking when the INS was implemented, or when GPS was common enough to obsolete it? $\endgroup$ Mar 13, 2022 at 17:53
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    $\begingroup$ I was USAF not NAVY, but I remember being surprised when I first saw the cockpit of a Navy F-4, and there was no INS in it. On reflection, of course it made sense, but this was early 1970s through the late 1980s. So the boats probably did not have INS until sometime during that period. $\endgroup$ Mar 14, 2022 at 16:08
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    $\begingroup$ Aircraft carriers are ships, not boats. $\endgroup$
    – rclocher3
    Mar 14, 2022 at 19:41
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    $\begingroup$ @rclocher3, you are of course technically correct, but to Naval Aviators they are boats. Only the Surface Warfare Officers concern themselves with such distinctions. $\endgroup$ Mar 15, 2022 at 0:50

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