WIP/Teaser: LSOBot …. BMS Carrier OP Landing Evaluation Tool
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What info are you looking for? I know a guy…
Well, it’s mostly that we’re in a “we don’t know what we don’t know” state. The goal for the tool is to provide feedback on traps so that pilots can improve. I think the visualization absolutely does that - even if you totally ignore the grading, you can be able to see where you were off glideslope, AoA, etc., since it’s just a presentation of the position and attitude of the aircraft. It’s the grading where things get more difficult, since it’s more subjective. For instance, if you enter mid very high but correct to being right on glideslope, should that be marked as “very high”? “High”? “A little high”? There can’t be one right answer, since we’re trying to boil down a whole bunch of numbers into what’s effectively one number, but it would be good to know that our general approach is sane.
And that said, we actually do have a few questions about the concrete parts, too. For instance, the source materials we’ve found suggest that ideal AoA might be 3.3 degrees, but we also understand this can be adjusted for different conditions. How should we handle that?
At a minimum, then, it would be great to have someone who knows how the pros do it take a look at it and say, “Basically sane”, “Close-ish”, or “Totally FUBAR”. One step better would be a description of how it deviates. A step better still would be an extended conversation about how to improve the tool in the context of the sim, since there may be good reasons to make it different from RL.
I’m also curious to know how (or if) you’ve implemented OK passes. It would be wicked if there was some way for LSOBot to determine if there were faults or damage and then hand out that coveted grade if you flew a nice pass.
We don’t have quite enough information to do this in all cases. For instance, aircraft damage is not necessarily present in the ACMI. Right now you can get an OK+ by flying a pass with no deviations whatsoever - not even a little high/low/fast/slow/left/right at any stage of the landing. I’m not sure I’ve ever seen even the AI do this, though. Kudos if you pull it off.
I think the right way to handle this in the future might be to simply include a checkboxes labeled “Difficult conditions” or “Damaged” or whatever that would let a human add in additional factors. Then the program could adjust grades based on that - bump it up by half a grade or whatever makes sense.
I’d also point out that to some degree chasing more and more “accurate” grading is a slippery slope. First, it’s subjective. Second, in the limit it involves creating the sort of machine learning system that would be fun to write, but is probably outside the scope of a hobby system, when I have other things I’d like to do for the community as well. But we’re definitely not done, so I welcome conversations about what would be helpful, efficient, and beneficial to add or change.
P.S. Adding CSV export right now.
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…… And that said, we actually do have a few questions about the concrete parts, too. For instance, the source materials we’ve found suggest that ideal AoA might be 3.3 degrees, but we also understand this can be adjusted for different conditions. How should we handle that? …
I think you mean a 3.3* glideslope here? That ‘estimate’ is based on what we observe in BMS to be ‘correct’ …. basically what AI flies, iirc. I do believe there is some external source material (NATOPs?) that indicates a ‘normal’ glide slope range and our ‘estimate’ fit within that range. More to the point … what is the ideal ‘BMS Glideslope’ and does it change with conditions, AC selection, etc.?
Another ‘good to know’ item would be different AoA ranges for different model AC. I’m pretty sure C/D may have a different optimum AoA range than the E/F, for example.
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I think you mean a 3.3* glideslope here?
Yes, sorry - you are correct. And +1 on the rest of your comments.
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Actually, the AOA has very little (if nothing) to do with setting the lens - it’s based on hook to eye distance for a particular jet, and what the LSO is really doing is flying the hook point into the wire, not the “jet” itself. So as long as you can get hold of proper lens settings for a platform (which I think also depend on landing gross weight - as AOA will also be) you can get closer to the desired “realisimo”.
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Actually, the AOA has very little (if nothing) to do with setting the lens - it’s based on hook to eye distance for a particular jet, and what the LSO is really doing is flying the hook point into the wire, not the “jet” itself. So as long as you can get hold of proper lens settings for a platform (which I think also depend on landing gross weight - as AOA will also be) you can get closer to the desired “realisimo”.
And in fact what LSOBot assesses is the hook position - you have to fly it through the correct profile to get a good grade. Obviously, the farther out you are, the less it matters.
But I think what Agave_Blue was referring to what that we observe AI F-18C and F-18D pilots flying quite different AoA on approach. The D model flies a fair amount faster.
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That does sound odd - especially given that the D should be lighter (thus slower), but that does not mean in any way that on-speed for the two jets is or even should be similar in a given situation. It has to do with geometry of the airplane and landing gross weight. One of the things we VR Viper-drivers are spoiled by is that the Viper doesn’t seem to have a landing weight limit - at least not that one I can find documented, anyway.
For CV ops bring back and GWT into the wire are critical - and limiting - factors. In any event, a proper CV approach is flown with the indexer centered, and that speed and AOA will vary substantially with GWT and CG. So it’s not really fair to compare even two jets of the same type, unless you know something about how they are configured and what they weigh. It sounds like you’re doing the right thing, just ignore the actual approach speed - only that the jet should be on-speed during approach. In which case you’d want to grade by monitoring the indexer…if that’s even possible.
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For CV ops bring back and GWT into the wire are critical - and limiting - factors. In any event, a proper CV approach is flown with the indexer centered, and that speed and AOA will vary substantially with GWT and CG. So it’s not really fair to compare even two jets of the same type, unless you know something about how they are configured and what they weigh. It sounds like you’re doing the right thing, just ignore the actual approach speed - only that the jet should be on-speed during approach. In which case you’d want to grade by monitoring the indexer…if that’s even possible.
We’re assuming the indexer in the Hornet shows AoA unadjusted for any other factor - like the one in the Viper does - and that’s exactly what we grade. Ideal AoA is 8.1* and there are thresholds around that defining minor, major, and unacceptable deviations.
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I’m already certain that the BMS Hornet model isn’t very accurate (in a lot of respects)…it should show on-speed for the gear down/full flaps configuration only, and unlike the Viper be off (dark/blank/not on) in all other situations. It should also show five vice three indications vs the Viper…which makes it a bit more “ticklish”. But attitude to get to on-speed AOA is still going to vary with GWT and CG, and that will put the hook point higher or lower in the groove as a result. I strongly suspect that all of the variables involved are not in play at this time in BMS history…after all, it’s a Viper sim.
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The question you mistook in post #16 was: What is the glideslope (via the iFLOS) normally set to and when/why would it vary?
We took AoA range and mid-point straight from NATOPs for late block C models. The BMS bracket (and lights) uses exactly that range …. 6.9 - 9.3 degrees of AoA; mid-point 8.1 (iirc). It’s easy enough to verify with video and/or ACMI. Our vSquad is aware of the C model max trap weight and dumps fuel accordingly … accounting for remaining stores if needed. What others choose to do … who can say?
We attempt to land just as you’ve described … on glideslope (center ball) and on speed AoA (ignoring indicated airspeed, which will change with fuel loss over just a few traps).
…. …it should show on-speed for the gear down/full flaps configuration only, and unlike the Viper be off (dark/blank/not on) in all other situations. It should also show five vice three indications vs the Viper…which makes it a bit more “ticklish”. …
These items are trivialities. Useful, perhaps, but not ‘game breakers’ in any sense.
The two ‘big’ issues with F/A-18C landings at present (imho) is the ship not being, and staying, turned into the wind whenever AC are in the recovery airspace and not being able to ‘read’ the ball from at least 3/4 nm. Those two things (again, imho) would do wonders for carrier ops landings in BMS.
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In RL they would reset the lens each pass, as GWT will change each pass as fuel burns, and aircraft attitude changes to capture and maintain on-speed. You’re hung up on AOA when the real issue is aircraft attitude on approach.
Ship not staying turned into the wind is a game breaker…
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In RL they would reset the lens each pass, as GWT will change each pass as fuel burns, and aircraft attitude changes to capture and maintain on-speed. You’re hung up on AOA when the real issue is aircraft attitude on approach. ….
That’s the first time I’ve ever heard or read that the projection angle of the iFLOS is changed on each pass. Do you have a source document I could review? For instance:
Under normal circumstances—average wind and seas—the ideal glide slope is centered at 3.5 degrees above the deck, which equates to 14.1 feet of clearance between aircraft hooks and the aft edge of the deck. But according to F/A-18 pilot Matthew Pothier, a former LSO school officer in charge, stormy seas can call for adjustments: “If the aircraft carrier is [pitching up and down] plus or minus 10 feet…that clearance factor starts to get a lot lower than 14.1 feet, because the lens itself—the meatball—is stabilized not to the aircraft’s movement but to the horizon, basically. So we’ll go ahead and adjust that glide slope up to four degrees. That’s usually the maximum we’ll land at, and that’s going to give us more hook-to-ramp clearance, basically—a couple more feet.”
….http://www.airspacemag.com/how-things-work/the-meatball-8421491/
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Jeeeez I feel a little sorry to see that tremendous amount of work
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Jeeeez I feel a little sorry to see that tremendous amount of work
Sorry - not sure I understand.
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That’s the first time I’ve ever heard or read that the projection angle of the iFLOS is changed on each pass. Do you have a source document I could review? For instance:
http://www.airspacemag.com/how-things-work/the-meatball-8421491/
…my source is some short time spent on an actual CV LSO plat, watching them do it. In RL it really is all about gross weight (which also determines how the wires are set) and aircraft attitude - the lens is set based on hook to eye distance, and that can change with aircraft attitude because of trim change due to fuel burn. So the actual geometry changes…each pass, each platform - they don’t land all F/A-18s in sequence, then all C-2s, then all…etc. - they all come aboard based on fuel remaining, which means the lens is constantly being reset. Every pass.
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…my source is some short time spent on an actual CV LSO plat, watching them do it. In RL it really is all about gross weight (which also determines how the wires are set) and aircraft attitude - the lens is set based on hook to eye distance, and that can change with aircraft attitude because of trim change due to fuel burn. So the actual geometry changes…each pass, each platform - they don’t land all F/A-18s in sequence, then all C-2s, then all…etc. - they all come aboard based on fuel remaining, which means the lens is constantly being reset. Every pass.
Ok, I’m willing to accept that and I understand the visual reference will need to change as the relative pilot viewing location changes (i.e. higher or lower for one AC vs another). I think this is what you’re referring to as ‘hook to eye distance’. But that conversation is a little bit of a tangent from the root of my question.
Every document, article or description I have ever read on carrier landing systems describes the FLOS/IFLOS meatball (or meatball v datum) as a glideslope reference …. that is a centered meatball represents a glideslope of x, where is ‘x’ is determined to be the optimal glideslope for current conditions.
Earlier you seemed to be saying that wasn’t necessarily correct and that the optimum glideslope changed with each pass. So, does the IFLOS encode glideslope visualization for the pilot and does the ideal glideslope change for each pass (during a single recovery event)?
For example:
…. The FLOLS, therefore, encodes deviations of the aircraft from glideslope as deviations of the meatball from the horizontal of the datum lines. The geometry of this relationship is diagrammed in Figure 2.
For purposes of the present discussion, the standard 3.5* glideslope is assumed;
The Retinal Image of the Fresnel Lens Optical Landing System
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Yes - and that glideslope is set based on the geometry of the particular aircraft to fly the hook point into the 3 wire. Every aircraft has a nominal hook to eye (design eye) distance - the literal measurement between the hook point and the pilot design eye point. The lens is set based on this distance - RL LSOs told me that - but the geometry can also vary dependent on aircraft trim (so four wires)…aft CG and the hook may hang lower than “nominal”…which means the pilot may need to trim nose down and fly faster to put the shoe in the proper groove - I’m speculating. CV glideslope is also 3 degrees nominal, I seem to recall…at least for the platforms I’m familiar with…but this may also vary dependent on how far aft of the CG the hook point is located. There’s a lot more that goes into it as far as setting the wire, bring-back, max trap, and max decent at trap for each type aircraft goes, but that’s the main of it.
Anyway, the cadence for getting to the groove is to call: call sign, fuel state, hook down, three green, and GWT/bringback…in some priority order which I forget. Then once the pilot has the ball in sight the call is callsign, “type-ball” so as to enable a final lens set check/verify, and fuel state…while the LSO watch are yelling “clear deck” or “foul deck” so the primary can wave or land the guy in the groove - during my trip there were generally a half dozen LSOs on the plat during ops…there is never just one guy there. I only spent a week watching, and it was a while ago…I mostly just tried to stay out of their way, but it was way cool not only to watch but just to have the privilege of being there to watch. Particularly at night. Those guys are SERIOUSLY trained up.
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I believe the glide slope is above 4 degrees, 4.1 if i’m not mistaken for the Hornet anyway. If anyone knows that would be great as the glide slope seems way to shallow in BMS.
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Jeeeez I feel a little sorry to see that tremendous amount of work
I think it will work well in concert.
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