Meatball Export

Even thought I'm a bit off, this is still way more than you would want to know about carrier landing geometry and the IFLOLS. If you spot an error and can back it up, let me know.

EDIT TO ADD: Found a big glaring error in the model of the carrier I used in the video. The scaling is off compared to Nimitz dimensions. I did the model import in meters but I think it might be in yards. (Reason 256 why the metric system is better and we should ban any other system) I've got to redo the whole shebang!

A few things. Your measurement of the Hook to ramp clearance as a sanity check is off. You’re measuring from the bottom of the round down. The measurement should be taken further forward of the rundown, where the deck levels. In doing so, you will have less hook to ramp clearance. Also I think your a bit confused on hook touch down point. I think your measuring the hypotenuse as the hook touch down point. The Hook Touchdown Point (HTDP) is measured from the ramp forward,it’s the adjacent angle in the glideslope right triangle

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However there is another flaw beyond these points where some error is coming from. You’re not compensating the light assembly for hook to eye distance. The entire IFLOLS assembly rotates in order to raise the beam of light above the deck.

The net effect moves the optical glide slope forward. When you project the glide slope straight out of the lens 3.5 degrees without raising to compensate you will always end up with to little hook to ramp and early engagements. It would be like a PAPI light placed 16 feet below the runway.

The way you built your glide slope with cross checking light heights is also off. Since your hook to ramp is off your light heights / glideslope ends up shallower because your hook touch down point is to far aft. Which is why it ends up with the hook on the 2 wire.

Hook to ramp clearance is calculated as the Tan of the IFLOLS angle = hook to ramp / hook touchdown point. This is done to provide a safety margin which can quickly be adjusted and calculated as conditions change.

As first sanity I would check the dimensions of the carrier layout. The model of the carrier could be off in a few ways that would effect your modeling. The wire distance from the ramp could be wrong. The height of the IFLOLS could be lower than expected.

The LSO NATOPS provides and interesting way to try and validate the dimensions too. According to page 4-9. “A H/E of approximately 16.5 feet with a 3.5 BA and 230 HTDP, results in a source light plane level in roll (zero roll angle)”

I really liked the video and hope you keep it, the community needs more of this stuff.

Thanks for the detailed reply. Before I go too much further, I think we may be saying the same things; technical topics always work better in direct human-to-human form. I've already noticed that my hook deck clearance should be taken from the flat of the deck and not the rounded portion. That helps push things forward a bit. (a bit too far on my first quick attempt actually: I don't quite trust the tessellations for the round down though).

One thing that stands out to me is that you seem to be implying that the glideslope relative to the touchdown center line is not actually 3.5 degrees; it effectively becomes something else. Is that basically what you're saying there?

Thanks for the detailed reply. Before I go too much further, I think we may be saying the same things; technical topics always work better in direct human-to-human form. I've already noticed that my hook deck clearance should be taken from the flat of the deck and not the rounded portion. That helps push things forward a bit. (a bit too far on my first quick attempt actually: I don't quite trust the tessellations for the round down though).

 

One thing that stands out to me is that you seem to be implying that the glideslope relative to the touchdown center line is not actually 3.5 degrees; it effectively becomes something else. Is that basically what you're saying there?

No. The Optical glideslope and hook glideslope have the same angle. The Optical glideslope is just above hook glideslope. This is done by rotating the FLOLS. The optical glide path and hook glide path form parallel lines. Hook to eye distance is a perpendicular line between the hook and optical glidpath.

I think your main problem is your hook touchdown point is wrong. You are defining the hook touchdown point as a spot along the optical glide path. This is messing with all of your geometry. The hook touchdown point is simply measured from the ramp forward. In the case of Nimitz class, the hook touchdown point is 230 feet forward of the ramp.

No. The Optical glideslope and hook glideslope have the same angle. The Optical glideslope is just above hook glideslope. This is done by rotating the FLOLS. The optical glide path and hook glide path form parallel lines. Hook to eye distance is a perpendicular line between the hook and optical glidepath.

 

 

I think your main problem is your hook touchdown point is wrong. You are defining the hook touchdown point as a spot along the optical glide path. This is messing with all of your geometry. The hook touchdown point is simply measured from the ramp forward. In the case of Nimitz class, the hook touchdown point is 230 feet forward of the ramp.

Your point is well taken, though I don't quite see how rotating the FLOLS is relevant to the issue. Clearly I need to shift my origin of my optical glideslope forward such that it yields a proper hook strike. I was hoping the derive where the hook strike is based on optics positioning though. I've modeled the optical glideslope and let the aircraft fly down that. The hook by definition is scribing a parallel line and I was observing where it hit the deck. What I can't seem to justify is why the origin needs to be shifted like that unless we're just going to chalk it up to "fancy optics in the IFLOLS". I suppose that is my real question. I agree that the 230 feet is inaccurate as I've modeled it, but it is mathematically not a significant source of error - the hypotenuse corresponding to a 3.5 degree angle and a 230 adjacent is pretty darn close to 230 feet. Still, I'll correct it.

I'm going to rebuild a sketch and allow the tail to strike in the direct midpoint between wire 2 and 3. Then I'll do a sanity check with the plane on that glideslope at the ramp and make sure my 14.1 ft of hoook-deck clearance exists.

Is there anyway to export the meatball data for use in another window? I'm flying VR and the screen door effect makes seeing it pretty difficult. I'm thinking that once I have a feed of the meatball data, I can maybe hook some sort of java window display around it and then get that back to the cockpit via ORVDrop.

Yes, I think it would be a nice option to have it in a separate window if required. I endorse this because of fine vision issues. IMHO, I think it would help many "older" sim pilots. The boat is much harder to see the meatball than when acquiring lights when landing on an airfield.

Thanks.

Found a big glaring error in the model of the carrier I used in the video. The scaling is off compared to Nimitz dimensions. I did the model import in meters but I think it might be in yards. (Reason 256 why the metric system is better and we should ban any other system) I've got to redo the whole shebang!