Having some ILS / RCBCO alignment problems; and a (possibly related) ILS problem.

[old_wombat]

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:

True=145.1
magvar=12.3 (???)
Magnetic=132.8

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.

[ronzie]

What carrier file?

[ronzie]

http://geokov.com/Education/magnetic...clination.aspx is for 2010 and allowing for a couple of degrees 12.3 looks correct.

Are you off of the eastern Australia coast? If so find an airport near there and afcad the file in FS to get the 2003 declination for an approximation of an ILS setup.

[old_wombat]

This is going to sound like "Who's on First?", but what "What carrier file?" The carrier is the "USS Nimitz - Tasman Sea" from the Carriers2006 package. The AFCAD file is the one that came with it. Is that the info you wanted?

Steve from Mudgee.

[old_wombat]

OK, done this. Also found some more info and it looks like 12.3 is about right for 2004.

Steve from Mudgee.

[ronzie]

I looked at from carr2006.zip the afcad for the Nimitz in the Tasmanian Sea. The LOC is lined up with the runway center line and the GS is set to 4.0.

What I see different is that the LOC appears to be lined up co-located with the GS. I also notice that the LOC back course is turned on. The GS antenna is located correctly offset to the side of the touchdown point. What is different is that the LOC antenna is placed at the same end of the runway. Usually it is placed at the distant end for better LOC navigation unless the author wanted extreme sensitivity at the touchdown point.

I looked up the Optical Landing System (OLS) for carriers:
http://en.wikipedia.org/wiki/Optical_landing_system

To adjust the GS to match the GS meatball in ADE I highlighted the GS antenna and can separately drag it around as desired if needed toward either runway end (aft or fore, correct?) to adjust the desired touchdown point to catch the arresting cables. You can also move the LOC fore and aft to adjust the beam width to within cable lateral tolerance ang with the LOC heading.



Now in ADE ILS properties the variance is shown as -12.3. Is that negative sign needed in the .ini as well?



As far as catching the GS are you intercepting the GS from below it and depending on your IAS maybe you need to start descent before capturing a steep angle depending on your aircraft type. To prevent fishtailing overshoot I always turn the aircraft heading inbound with the heading control as the LOC indicator starts moving toward center and enabling the hnav or app coupling.



Please note in the author's documentation he references some added flatten files in fixes to correct altitude problems from the oruiginal in this update.

Yes, I'm too chicken to have tried a carrier approach. I did watch the PBS carrier documentary and also plenty of military carrier ops on PBS.

BTW, have you found FS's ground effect in force on take-off as you roll off the end of the flight deck? You should get a slight dip and then stabilize level to start a climb. Right?

[old_wombat]

Ronzie, thanx for your comprehensive reply. I have done a fair bit of investigation into the problem myself and many issues are now resolved. To address the comments that you raised:

- 4.5 degrees is almost unflyable, 4.0 degrees does work much better. I have both the meatball and the ILS now set to this.

- I have within AFCAD moved all parts of the ILS to the same spot, the centre of the fore arrestor wire (Number 4). I quickly discovered that this works better than the aft arrestor wire (Number 1). Depending on the plane, following the ILS now plonks me down in the middle of the arrestor grid.

- Whether the 12.3 needs a minus or not turned out not to be the problem. And in any case the meatball's .ini file is only interested in the magnetic heading so a variance is not used there. The problem turned out to be a dumbass user (that would be me) error. The meatball gauge BMPs were not as sharp as I liked them. I cleaned them up in Paintbrush and introduced some, uhhhh, "pixel location errors". I have since corrected these and the ILS localiser now matches the meatball perfectly. So that issue is fully resolved.

- The flatten files are essential, as without them you end up with immobile mountains of water higher than the flight deck. A most improbable situation even in the most unaptly (inaptly?) named "Pacific" Ocean

- The ground effect happens on takeoff exactly as you describe it. Very scary the first time you come off the catapult Unless you do the totally unrealistic thing of setting the catapult speed way above takeoff speed and rotating the nose early then you will lift off the deck before the end of the catapult stroke. Even in a simulation that looks totally wrong - which it of course is.

- Finally, as to catching the GS the problems are that (a) as previously said, 4.5 degrees is too steep a slope; and (b) since I am desperately trying to be a Jake Grafton / Harman Rabb and am therefore only interested in doing a perfect landing trap, I was starting my flight way too close to the carrier and the autopilot simply could not catch up in time. If I start the flight say 12 miles out the autopilot can in most cases capture the ILS beam. There are two outstanding autopilot issues that I am going to put into a new post if I can't fix them myself.

- The AFCAD file has the TRCV meatball, which may or may not in real life be actually an IFLOLS like in your detailed image. I have not yet been successful within AFCAD in moving the working meatball into the (blank, and I think in error) meatball artwork in the BGL file. This is of course only a cosmetic issue.


- To summarise, as a result of the above, the main goal - having the ILS exactly match the meatball gauge - has now been achieved.

Steve from Mudgee

[ronzie]

Glad you have most of this resolved

You mentioned testing with the C172 but if you go to jet military aircraft be sure they have the tail hook feature and you have the command set up in FS9 to lower and retract it. If you are using WWII prop aircaft did they require tail hooks or did they just get caught in the landing gear.

A quick OT note on one of the PBS carrier episodes. They did a profile on one of the on-board flight controllers using radar. She had an instance where a practice flight was conducted in rough seas in poor visibility. A jet was on its third try low on fuel. I think she did a radar precision approach to get it in the ballpark and avoided a water landing. I believe the jet had defective ILS. She saved the plane and possibly the pilot but it took a toll on her nerves for awhile.

[old_wombat]

Uhh, I use the C172 ONLY to slowly taxi around an area with the rcbco precision position indicator on to determine position for things like the arrestor wire and the catapult area; and also when I am precision placing scenery. I don't actually try to land it nor catapult launch it. That would be too bizarre even for me, and my wife already sometimes call me Sheldon Nor am I interested in WWII warbirds so I can't even comment on that area.

I am extremely lazy, so equip all my jet fighters with the same panel. It is a self-customized version of the default Boeing 737 mini-panel, with an added window for the catapult/tailhook toggles plus the precision position display; and of course another window for the meatball landing HUD. I only want to do landings and takeoffs (ie am not interested in flying supersonic nor at 70,000 feet nor pulling 12g turns), so the intrinsic limitations of the airliner gauges do not concern me.

Turning to your OT comment, here in Oz we had a series on the teev, called "Carrier", which sounds like it may well have been your PBS show. I do believe it was on the Nimitz, not totally sure as I only saw a couple of episodes in full as they conflicted with my wife's "Escape to the Country" I do vividly recall your story of the woman flight controller bringing down a plane at night on a pitching deck. I don't recall the defective ILS, though (although that's not to say that that wasn't the case). My recollection is that the pilots were simply afraid (and I use that word very reluctantly, given what they do) to land low enough in case they got hit by the deck pitching up, that they had to time their landing so that they hit the wires at the moment that the carrer was at the top of a pitching movement. It did give an excellent and to me totally nerve-tingling display of just how small that target area is when trying to drop a high-speed F18 onto it.

I am amused by your "land of 10,000 puddles". You may or may not know that here in South-East Oz we have had the wettest two years in the entire 250 year history of white settlement in this country. All of our creeks and dams and rivers are full for the first time this century. Towns all over the state are reporting seeing waterbirds that over a decade ago were recorded as extinct. I myself have had one such looking for fish in my lilypond (which has no fish). Global warming does not get great credence here

Steve from Mudgee