The meatball gauge on the carrier uses information in a matching .ini file. In it I have a rectangular box marking out the corners of the grid of arrestor cables. I drove this boundary many times with the Cessna 172 and am satisfied that the coordinates of it are correct. There is also a runway heading and a runway altitude. I have put all that into the .ini file and when I do a meatball landing it seems to be OK. I say "seems" because even into a 36 knot headwind (reasonable for a nuke carrier), landing on such a small target happens very fast and I am only a very ordinary pilot
The carrier also came with an AFCAD.bgl file that I have opened up with AFCAD (Yes, Jim, it should be ADE, but let's not go there now). I have set the altitude and runway heading to match the meatball info. I have also moved the ILS, glide slope and localiser to the centre back of the arrestor grid. That is, the three pairs of coordinates for ILS info in the AFCAD data entry screen match exactly the midpoint of the BackLeftCorner and the BackRightCorner in the .ini file. And I have put in the same value for the glideslope in both sets of places.
With all of this matching, on an approach I would have expected the indicators in ILS landing system to match the meatball exactly. But it doesn't. The glideslope seems to be OK, but the localiser does not. Now I wonder whether there is a magvar issue here? In the AFCAD editor I have the following, the arithmetic is certainly correct but I wonder about the value itself:
My carrier is at S31.3 E153.4 . Is a magvar of 12.3 correct for this location? If it is, then obviously it's not the source of the lack of alignment, so what might it be?
The other issue is that planes I have flown for many years into all sorts of airports wont lock onto the ILS. I approach the carrier at a reasonable speed and manually fly the needles and the meatball until I am "almost perfect" on the ILS. A few miles out, well within the ILS range, I select Autopilot on and select Approach, as I have done at many other airports. Under AP control, the planes roll correctly first one way then the other to end lined up on the localiser. At this point I can't roll the elevators manually, which I believe is correct. However, the planes do an ever-increasingly steep dive and do not lock onto the glideslope, and I can pitch up and down manually.
There is definitely a glideslope section in the AFCAD file; well at least there is in the data entry screen, and I have put the data into it The only thing that I can see being significantly different is that being for a carrier rather than a land-based airport, the glideslope angle is set to 4.5 degrees, a value I got from a US Navy website about its aircraft carriers. I have tried the traditional 3.0 degrees and the problem still occurs.
Steve from Mudgee.