F-16 Pilot- Chris Lehto analyses Gimbal footage

FatPhil

Active Member
Hello i'm a brand new member and really new to this whole thing so maybe this is a dumb point but here goes.

Mick, I think you missed one of the key points of Chris' video in your rebuttal. His point of reference for the location of the object is not the intersection between the camera views, but instead a trajectory of the object being recorded that places it at a location on each line at each time point. This has a few key assumptions, mainly that the object is going at a constant velocity without turning. That's why his representations for location of the object are places where the distance between each line of bearing is equal, not the intersections. Focusing on the intersection between point 1 and 2 in your simulation makes no sense to me. How could an object be at the intersection of line of bearings 1 and 2 but then Jump to the line of bearing of point 3? it makes no sense. Each line of bearing represents some location where the object must be at that point in time. Assuming it's moving (a decent assumption given its elevation) It takes 10 seconds to get from a point on line 1 to line 2 to line 3.

The error in estimating the position using the intersection of the bearings from times t and t+delta are small compared to the other errors that exist in the model, and don't change the results significantly. The intersection is best viewed as an estimate of the position of the object at time t+delta/2 - one line will be off by some amount, the other line will be off by some other amount the other way. Better schemes can be introduced when/if there's sufficiently reduced uncertainty in the inputs to warrant it, and right now there isn't. Pinning down the rate of turn is way more important, as it has far more significant numerical repercussions.

Staff member

OneEleven

New Member
Lehto's response

He seems to resolve on a rate of turn higher than mine, but lower than 3.0

I don't have time to get into it this week. Maybe next week.
Chris seems to ramble a lot on irrelevant things and leaves thoughts unfinished. I wish he was a bit more focused. But maybe I'm just too stupid to get it.

It wasn't clear to me how the weight of the plane enters in reading that chart.

I also did not understand where he's coming up with those lines of intersection at the end. You could in principle put any line anywhere by assuming different speeds, no? Is he really just eyeballing based on the "constant size"? Isn't this going to be irrelevant if the object was a glare (flare?) from a far away object? Couldn't this assumption of his be biasing him towards assuming certain properties of the turning he admitted were guesswork at the beginning?

I also don't really understand the relevance of the standard rates of turn for airports for fighter jets doing exercise in the middle of the ocean. Surely none of those concerns matter under such circumstances?

This linear motion assumption could be a good way to analyze these videos (Gimbal and Go Fast): take agreed-upon trajectory of the plane and lines of sight, assume a constant speed object and find which linear motions are the most compatible with the data (instead of eyeballing). I could write such a software if there's any interest (taking positions and angles as input, not calculating the actual trajectory of the plane as I don't have the time to learn about this turn radius stuff). It would be a definitive statistical approach provided the position of the plane and the lines of sight are in agreement (which is where we're trying to reach).

It's also very sad to see highly trained pilots confidently using the Bernoulli principle as an explanation for lift. I wonder how many generations we need until that incorrect explanation finally dies. But that doesn't invalidate his points, it's just highlighting how pilots can be outdated in their physics too, so they are not authorities in the subject of physics of how planes actually fly. There's a significant amount of intuition-based skill, and intuition isn't objective or authoritative.

BrianHoltz

New Member
So he spends his first ten minutes justifying his original assumption of 3 deg/sec, and how it's so important for safety around airports etc. But then a few minutes later he's revised his estimate to 2.27 deg/sec. (That's an extra 38sec to complete a safety-critical "standard turn".) The "standard rate of turn" assumption has thus been completely discarded -- as well it should, for a plane flying way out over the ocean in military-exclusive airspace and very little other traffic.

His new rate of turn (which doubles his estimated range from ~4nm to ~8nm) is driven by a true airpseed of 400kt vs Mick's 350kt. His mistake is easy to spot, at 18m20s. He's kept the calculator's default air temp at 20C (68F), while standard atmospheric models give air temp at 25kft to be -34C (-30F). This leads him to inflate the true airspeed and throw off his calculations.

DavidB66

Active Member
....

It's also very sad to see highly trained pilots confidently using the Bernoulli principle as an explanation for lift. I wonder how many generations we need until that incorrect explanation finally dies. But that doesn't invalidate his points, it's just highlighting how pilots can be outdated in their physics too, so they are not authorities in the subject of physics of how planes actually fly. There's a significant amount of intuition-based skill, and intuition isn't objective or authoritative.
If you haven't already seen it, you might like this video about the reasons for 'lift' by a professor of physics at Nottingham University. I haven't watched it again, but I remember finding it interesting. I see that I commented on it 3 years ago when I first saw it!

markus

New Member
Quick free-body diagram illustrating Lehto's main mistake.

The lateral acceleration (and thus the turn rate) is independent of weight because the vertical component of the lift vector cancels the weight during level flight.

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• lift.png
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Z.W. Wolf

Senior Member.
A very powerful telephoto lens can have a "hyperfocal distance" that is measured in miles. I made a post years ago in another thread:

In his first video, it seems to me that he is not discriminating between focus, motion blur and resolution as much as he should. In the case of the plane flying over land, which he compares to the plane over the ocean, he is not taking context into consideration. Waves on the ocean are simple and consistent. Features in landscapes are not.

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the_korben

New Member
Quick free-body diagram illustrating Lehto's main mistake.

The lateral acceleration (and thus the turn rate) is independent of weight because the vertical component of the lift vector cancels the weight during level flight.
If I am not completely wrong and based on 20 years of sim flying, I think what Lehto is talking about is that you don't just turn an airplane by banking. You also need to apply some pressure on the stick, thereby increasing the g load, to make a turn and remain level, otherwise you will slip. This in turn requires you to add some rudder to counteract your slip. You can turn harder at the same bank angle by applying even more force on the stick, but your turn will be even more uncoordinated, your altitude would increase AND you would need to counteract that with your rudder AND you would increase the load on the plane.

Looking at the chart, the lines for 30 deg bank angle show you the corresponding g load when doing a coordinated turn, i.e., when the rudder applied exactly counterbalances the additionally required angle of attack at 30 degrees bank to facilitate a standard rate turn. It doesn't mean that every turn at 30 deg bank will automaticall be a standard rate or coordinated turn at the given TAS. You can just bank and make your HUD indicate a 30 degree angle but by applying enough rudder and force on the stick, not even turn at all.

I think Lehto's argument here is that the higher g forces indicate that the plane is turning on a narrower radius than what you would get for a coordinated turn at 30 degrees bank angle. That's valid and needs to be taken into account and it cannot be determined from just looking at the angle of the flight path indicator. You need to take the g forces into account as well to actually determine the (varying) turn radius.

Mick West

Staff member

"A heavier aircraft will go around the larger circle faster but have the same rate." sounds like nonsense. We know the speed of the plane, it does not change significantly from 241 knots CAS (240-242). If you have a constant rate of turn and constant speed, then the radius is going to be constant, regardless of mass.

I think Lehto's argument here is that the higher g forces indicate that the plane is turning on a narrower radius than what you would get for a coordinated turn at 30 degrees bank angle. That's valid and needs to be taken into account and it cannot be determined from just looking at the angle of the flight path indicator. You need to take the g forces into account as well to actually determine the (varying) turn radius.

But is there evidence that it's not in a coordinated turn? It seems to be in speed and altitude-hold autopilot, as it maintains a constant speed and altitude. Chris tried to do this in the simulator, but could not get it to work.

Member
I feel like he isn't doing a great job articulating his arguments in these videos. This one was all over the place with tangents and disconnected points of contention. The dozens of jump cuts make it even harder to follow. I'd like to see him slow down and take some time to really articulate his points and I'd be fine with him sharing his ideas about what we might be looking at, even if it amounts to "alien spaceship."

At the end of the day I'm not sure it even matters. What difference does it make if the object is 6nm away or 50? Neither option makes the identity of the object more prosaic or more mysterious. It's still a blob that isn't doing anything otherworldly.

gtoffo

Active Member
Finally someone decided to try and simulate this on DCS! Love it. We need someone to download it here too. I don't own a PC unfortunately.

I'm not sure how much the loadout would affect the test. But I doubt they were flying with a full load out (all missiles tanks etc.). I would set up the aircraft with a more average loadout.

In any case he can't be off by much at this point.

If we are assuming a static object we have 3 pretty close points that could realistically indicate a static position for the 3 observations. I think that is the minimum distance.

If the object is moving then Chris shows the maximum realistic distance possible.

Those are still pretty close ranges. Even if we double them up we are at a very close intercept range for an F-18. It should be clearly visible on ATFLIR/Radar etc.

the_korben

New Member
But is there evidence that it's not in a coordinated turn? It seems to be in speed and altitude-hold autopilot, as it maintains a constant speed and altitude. Chris tried to do this in the simulator, but could not get it to work.
I did a bit of research on the autopilot modes and it seems there's attitude hold, two altitude hold modes, a course selection mode and a coupled mode that allows you to navigate to waypoints etc. There's also an auto-throttle button that holds your TAS. I would say the varying bank angle indicates that attitude mode is not engaged and all other navigational modes would (probably) use a fixed bank angle for coordinated turns.

In this sense, there is no indication or auto-pilot limitation that requires a coordinated turn. Indicated airspeed seems to increase by almost 2 percent rather than oscillate, but I'm not sure how precise the auto-throttle would be for that to be any indicator of auto-throttle on vs. auto-throttle off.

If I was in that plane (rather than in front of my cheapo flight sticks in front of the computer screen ) I would probably also just engage altitude hold and auto-throttle while handling my turn as I see fit to follow the target.

Z.W. Wolf

Senior Member.
Okay, his argument in the first video about "the way optics work" is really very misleading. He's comparing two different lenses at two very different distances and implying that the two situations are completely isomorphic.

This isn't the case at all. For his argument about focus to mean anything, he's got to tell us what the hyperfocal distance was for the camera in question; not show us the hyperfocal distance for his little camera inside the room. Anything else is empty speculation based on an argument from analogy which isn't valid.

He's bragging a lot about his expertise, but I'm not at all impressed by this argument about optics. This just seems very naïve... or deliberately misleading.

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the_korben

New Member
Important addition for my post above: I just found out thanks to Chuck's Guide that any altitude hold mode in the plane will actually require you to either fly straight and level or have heading- or attitude-hold mode engaged prior to this enabling altitude-hold mode as well.

So they were at most using auto-throttle or they could have also used the HSEL heading select mode, set a course and used the little bit of freedom it gives you to modify the roll angle a bit. But since the roll angle varyies form 25 to 35 degrees, I'm betting they flew manually (perhaps with auto-throttle).

dimebag2

New Member
Looking at this with the Geogebra schematic, the distance strongly depends on the points that are used to construct the intersection. A strong asumption is that the bank angle is constant, at 30°, but it is clearly changing from points 1 to 4. Here are screenshots of the Gimbal video, with a focus on the bank angle, at the 4 points taken every 10sec, with a protactor overlaid (cool online too I found) to measure the bank angle.

Point 1 (53° camera angle) :

The bank angle is about 26° -> 1.3-1.4 Rate of Turn based on the Bank Angle vs RoT graph you use

Point 2 (38° camera angle) :

The angle is about 31° -> ~1.6-1.7 Rate of Turn

Point 3 (21° camera angle) :

The angle is about 36° -> ~2.3-2.4 Rate of Turn

Point 4 (1° camera angle) :
this point is kinda dismissed but it's an interesting one, the plane is now basically pointing towards the target

The bank angle is still 36°, so here we have a constant RoT for 10 sec (2.3°/sec).

I've added point #4 in Mick's Geogebra (see below), with this RoT of 2.3°/sec, the intersection between Pt3 and Pt4 gives a distance of about 5.4 Nm. Using Intersection23 with a RoT of 2°/sec (average between Pt2 and 3) gives a distance of~10Nm. For sure, the results depends a lot on which points/intersection is analyzed. I would argue Pt3 and Pt4 may provide a better estimate because the bank angle, hence rate of turn, is constant between them (since the fighter speed stays the same). I'm not very good at geometry so I do not pretend being right here, and I appreciate any insights on this.

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Daniel F

Member
Okay, his argument in the first video about "the way optics work" is really very misleading. He's comparing two different lenses at two very different distances and implying that the two situations are completely isomorphic.

This isn't the case at all. For his argument about focus to mean anything, he's got to tell us what the hyperfocal distance was for the camera in question; not show us the hyperfocal distance for his little camera inside the room. Anything else is empty speculation based on an argument from analogy which isn't valid.

He's bragging a lot about his expertise, but I'm not at all impressed by this argument about optics. This just seems very naïve... or deliberately misleading.
I hear you, but I don’t get the impression he’s deliberately misleading. A bit loose with terminology maybe? But who am I to judge ! Just check my posts!
I welcome his input. Faults and all. None of us are perfect. Don’t see any wilful deceit or deviousness. Quite the opposite. Whatever you think of his knowledge ( or lack of ) regarding optics. I think it’s all coming from the right place . Bit off the topic of thread, but I can sometimes get too engrossed down these rabbit holes and start pigeonholing people on ‘my side’ or ‘their side’. Forgetting that we are all essentially engrossed in the same fascinating debate. It’s good to have people with knowledge involved whether I believe they are right or wrong. As long as it’s not intentional BS.
Maybe I’m wrong, but I don’t get that impression here.

Z.W. Wolf

Senior Member.
If what he's saying is wrong, and he's using faulty logic, how is that helpful?

He's also insisting he's right because he's better at this stuff. How is that helpful?

Synov

New Member
Hey all, longtime lurker here. Unless I am missing something, Chris is completely wrong when he claims the weight of the plane is relevant to calculating the turn rate for a plane in a level turn.

L = lift
Lv = vertical component of lift
W = weight
ϕ = bank angle

n = L/W by definition

W = Lv for a plane in a level turn

Lv = L cos(ϕ)

Therefore n = 1/cos(ϕ)

Any plane in a level turn at bank angle ϕ will have the same load factor, regardless of speed and weight.

Daniel F

Member
Very interesting simulator he used as well. Does anyone here use that software ? Particularly interested that you could in theory plot the gimbal encounter and observe how the atflir pod follows. Whether it’s in constant motion or not. May not be definitive or 1:1 accurate but it seems pretty detailed.

MarcusH

New Member
If what he's saying is wrong, and he's using faulty logic, how is that helpful?

He's also insisting he's right because he's better at this stuff. How is that helpful?
He’s brought the debate to a new level and he’s also willing to admit mistakes. He should only be encouraged.

jarlrmai

Active Member
It's DCS it's 60 UK pounds for the f/18 pack. I'm fairly close to picking it up at this point I've read enough ATFLIR manuals I can probably use it from memory. However it's only recently the ATFLIR was added though and not all the features we see in the videos are in, in fact it's quite telling that the hardest parts for them to simulate are some of the things we see in the video. I doubt they will actually simulate stuff like IR glare and physical lens changes causing track loss. I think they just added auto track but it's just faked they didn't actually simulate the IR and contrast tracking etc

Daniel F

Member
If what he's saying is wrong, and he's using faulty logic, how is that helpful?

He's also insisting he's right because he's better at this stuff. How is that helpful?
You’re right, it’s not helpful. I just stop short of deliberate misleading. More naivety. I recognise the symptoms very well !
I understand your position though and my comments were not in any way aimed at you !
When I say, observe the atflir- I mean externally watch it’s motion. It’s always been my belief that it must have been constantly rotating from its 54 deg left of target start. I know Mick argues very persuasively that the mirrors do the work but I’m not sure.

Daniel F

Member
It's DCS it's 60 UK pounds for the f/18 pack. I'm fairly close to picking it up at this point I've read enough ATFLIR manuals I can probably use it from memory. However it's only recently the ATFLIR was added though and not all the features we see in the videos are in, in fact it's quite telling that the hardest parts for them to simulate are some of the things we see in the video. I doubt they will actually simulate stuff like IR glare and physical lens changes causing track loss. I think they just added auto track but it's just faked they didn't actually simulate the IR and contrast tracking etc
Interesting. The most fascinating bit of his video was watching the gimbal pods motion. Do you think that it would simulate its tracking capability by actually moving on its axis as in reality ? That would be intriguing.

Daniel F

Member
I agree, it probably wouldn’t do artefacts but it may replicate the gimbal pod movements accurately?

MarcusH

New Member
In a reply to a comment from “chipsteroni” Chris say’s he’d be happy to go on your program Mick.

OneEleven

New Member
If you haven't already seen it, you might like this video about the reasons for 'lift' by a professor of physics at Nottingham University. I haven't watched it again, but I remember finding it interesting. I see that I commented on it 3 years ago when I first saw it!

Very nice video! Looks like I was too harsh on Chris, and I was wrong about the lift thing too. I stand corrected.
We really could use more physicists in this discussion, but it's unfortunate there's so much taboo.

In a reply to a comment from “chipsteroni” Chris say’s he’d be happy to go on your program Mick.

So, time for Chris and Mick to have a chat and get to the bottom of this and end this back and forth?

If this is happening, it would be helpful if we could put together some questions to Chris.

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jimmyslippin

New Member
He’s brought the debate to a new level and he’s also willing to admit mistakes. He should only be encouraged.

I am getting the sense that he respects Mick a whole lot more now than he originally did.

dimebag2

New Member
Hey guys, I had this feeling that something is wrong with the object being distant, and making more detailed analyses of the geometry confirms that. This is a fun problem to work on ! I started from Mick's Geogebra, but instead of having a constant Rate of Turn, I make it change along the course of the flight (see my post above that shows how the bank angle, hence rate of turn, changes from Pt 1 to Pt4). So there are different circles for Pt 1, 2 3 and 4 (3 and 4 are on the same circle because the bank angle does not change between them). Rather than fixing the different angles between Pt1/2/3/4 and Gimbal, I try to find a trajectory for Gimbal that would match the trajectory of the plane (along Pt1/2/3/4), and the corresponding IR camera angles (53°, 38°. 21°, 1°). I use a True Air Speed of 360 Knts (like Mick).

By doing that, it is clear that the object cannot be very distant. Or it would move at supersonic speed, which is not at all in line with the plane/glare theory. The only way I find a trajectory that matches the plane position, and camera angle, is for fairly close distance of ~5Nm. Here is an example, this is a GIF that shows a potential trajectory with more or less constant distances between the fighter and Gimbal (4-5 Nm) :

Look at the angles 1, 2 , 3 and 4 between Pt1/2/3/4 and Gimbal, I make them match the camera values (53/38/21/1) from one point to the next. The distance given in red is the corresponding distance from the new plane position. It stays between 4 and 5 Nm. Playing with possible trajectories, that are not many that fit these camera angles, and especially with larger distances from the fighter.

The more Gimbal is moved away from the fighter, the more impossible the angles are to match, or the object would have to cover a super large distance, greater than the plane (i.e. move at supersonic speed). Here is an example with a distance of 50Nm, for PT1 and PT4 (the other points/angle don't even make sense).

You can see how large would the distance be compared to the distance covered by the fighter (that goes at 0.6 Mach). And this is for a distance of 50Nm only, it is even less sustainable for greater distances.

Sorry if this is obscure but I hope it will make sense to those who have played with this schematic, especially Mick. I may be wrong, but if I'm not it is clear that Gimbal cannot be very far from the fighter, it simply does not align with the camera measurements. I'm not trying to prove one side or the other, I just find it a fun puzzle to solve, and hopefully this brings something interesting on the table. If I'm wrong I'd be happy to hear where this can be fixed.

I'd like to share the GeoGebra project so you can all play with the Gimbal position, but GeoGebra does not send me the confirmation email for registration, so I'm stuck with showing GIFs for now. But I can share the GeoGebra file (gpp) if somebody is interested in this model, I was able to save it.

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Mick West

Staff member
Sorry if this is obscure but I hope it will make sense to those who have played with this schematic, especially Mick. I may be wrong, but if I'm not it is clear that Gimbal cannot be very far from the fighter, it simply does not align with the camera measurements. I'm not trying to prove one side or the other, I just find it a fun puzzle to solve, and hopefully this brings something interesting on the table. If I'm wrong I'd be happy to hear where this can be fixed.
I think really the next step would be to do a frame-by-frame analysis in code to get a continuously varying curve, rather than a series of arcs. A fun challenge I might get into next week - although I suspect others might beat me to it.

Ultimately it would be good to find a way of using a simulator. DCS has a Lua scripting engine which might work, but I can't quickly find if it exposes the plane's controls in a simple way.

OneEleven

New Member
I think really the next step would be to do a frame-by-frame analysis in code to get a continuously varying curve, rather than a series of arcs. A fun challenge I might get into next week - although I suspect others might beat me to it.

Ultimately it would be good to find a way of using a simulator. DCS has a Lua scripting engine which might work, but I can't quickly find if it exposes the plane's controls in a simple way.
Does anyone have a spreadsheet with all the data? I tried looking in past threads and couldn't find it.

markus

New Member
If I am not completely wrong and based on 20 years of sim flying, I think what Lehto is talking about is that you don't just turn an airplane by banking. You also need to apply some pressure on the stick, thereby increasing the g load, to make a turn and remain level, otherwise you will slip. This in turn requires you to add some rudder to counteract your slip. You can turn harder at the same bank angle by applying even more force on the stick, but your turn will be even more uncoordinated, your altitude would increase AND you would need to counteract that with your rudder AND you would increase the load on the plane.

Looking at the chart, the lines for 30 deg bank angle show you the corresponding g load when doing a coordinated turn, i.e., when the rudder applied exactly counterbalances the additionally required angle of attack at 30 degrees bank to facilitate a standard rate turn. It doesn't mean that every turn at 30 deg bank will automaticall be a standard rate or coordinated turn at the given TAS. You can just bank and make your HUD indicate a 30 degree angle but by applying enough rudder and force on the stick, not even turn at all.

I think Lehto's argument here is that the higher g forces indicate that the plane is turning on a narrower radius than what you would get for a coordinated turn at 30 degrees bank angle. That's valid and needs to be taken into account and it cannot be determined from just looking at the angle of the flight path indicator. You need to take the g forces into account as well to actually determine the (varying) turn radius.
Indeed there's an assumption that the lift vector points upwards normal to the plane of the wings (or whatever corresponding symmetry plane when there's a dihedral, etc. -- you know what I mean). Note that even Lehto assumed that this is the case, and it's an assumption that always goes together with the phrase "standard rate turn". In uncoordinated flight the results can be different. However, uncoordinated flight is inefficient and there'd be no tactical reason to use it. I could see a fighter pilot using uncoordinated inputs in a dogfight to trade energy for turn radius/nose position, but what we're seeing looks like a fairly standard intercept with the F-18 getting in (again what looks like) an advantageous position. So there'd be no reason to perform a maneuver as crass as a slip/skid.

As an aside, these aircraft have pretty small adverse yaw tendencies, and require very little rudder input from the pilots for proper coordination. I first heard this from CW Lemoine (sorry, I don't remember the exact video), but it can be easily verified in simulators. Whether this is a result of aerodynamics or the flight control system automatically applying the proper inputs I don't know, but the end result is that the assumption of coordinated flight is a pretty good default assumption here. Again, Lehto himself assumed this (around 13:40 in the De^4-bunking video), so he couldn't possibly have meant that the pilots were trying to turn faster than ordinary coordinated flight allows.

Zerth

New Member
At the end of the day I'm not sure it even matters. What difference does it make if the object is 6nm away or 50? Neither option makes the identity of the object more prosaic or more mysterious. It's still a blob that isn't doing anything otherworldly.
Isn't the distance at least somewhat useful in analyzing the blob? If the main hypothesis is that it's a glare, and we know how glares look like at X distance when it's a Y aircraft. It's a bit of a brute force approach, but I think it can be useful.

What is even the maximum distance that you'll see a glare at? Or a rough estimate, if anyone knows.

Mick West

Staff member
What is even the maximum distance that you'll see a glare at? Or a rough estimate, if anyone knows.
There is no maximum, it just depends on how hot it is. The sun is at 93 million miles and glares just fine.

dimebag2

New Member
Of course the distance is key here. If it's close then it's clearly not a plane, or anything with a clear propulsion signature.

Here is my Geogebra model (adapted from Mick) that allows to play with the Gimbal position, and figure the different distance d1/d2/d3/d4 from Point 1/2/3/4 :
https://www.geogebra.org/classic/jjxxmdxs

You can move the Gimbal object, and follow the values of d1/d2/d3/d4 on the left of the screen. Units are in Nautical Miles (the selected airplane speed is 360 Knots, i.e. 360 Nm/h).

It's very easy to see that a long distance for Gimbal just does not match the plane trajectory and IR camera angles. Or Gimbal would have to cover a very large distance, hence moving at supersonic speed. This is quite simple geometry really, I let you guys figure it by yourself. At this point I really think this is a legit footage, and not any camera artifact.

Member
Isn't the distance at least somewhat useful in analyzing the blob? If the main hypothesis is that it's a glare, and we know how glares look like at X distance when it's a Y aircraft. It's a bit of a brute force approach, but I think it can be useful.

What is even the maximum distance that you'll see a glare at? Or a rough estimate, if anyone knows.

I think the distance only becomes important when paired with other points of data that can be used to establish a likely identity. Kind of like how the Chile 'UFO' encounter was solved. Unfortunately in this case we're unlikely to get additional data and none of the proposed hypotheses have really truly solved the case.

I just think we're seeing people talk in circles at this point. Lots of arguments about glare and distance but none of that really gets us much closer to identifying the object in the video. Basically "It's probably a plane but we don't have enough data to definitively prove it isn't an alien spaceship."

the_korben

New Member
Again, Lehto himself assumed this (around 13:40 in the De^4-bunking video), so he couldn't possibly have meant that the pilots were trying to turn faster than ordinary coordinated flight allows.
First off, thanks for your valuable input. Also, yes, I don't think Letho is arguing very consistently in these videos, so it's all a bit of a mess.

Concerning coordinated vs. uncoordinated turns, I did read a comment by an F/A-18 pilot on reddit at some point where he mentioned that some of his colleagues like to use lots of rudder and an uncoordinated turn when using the targeting pod. But I can't find it right now. In any case, this is probably something that the pilots themselves will have to answer.

The only thing I wanted to point out is that given the (limited) info in the video, it is not correct to assume that we have all the variables covered by just looking at/tracking the angle and the chart. I was totally shocked last night that I did not realize this before and only realized it thanks to Letho's video and your initial comment.

I also agree with the others that using DCS with a more stable, scripted approach would probably be the best thing to do. I do have DCS and the F/A-18 module, but I don't have it installed (it's huge ... like 200 GB if you have several of the modules) and I don't really have time for this stuff right now (kids, work). Another idea would be to track the cloud and cloud parallax by employing some kind of cloud-size model. That could also give us an additional scalable data point for the true angles.

Z.W. Wolf

Senior Member.

Chris Lehto (Edited for clarity and brevity). Talking about the GoFast Video.

He's saying there's no way a purely passive optical device, or a computer, can tell how far away something is by just by processing the photons it's passively receiving.

This is false. What about an optical rangefinder? How does that work?

C.W. Lemoine - an F-18 Pilot. Also talking about the GoFast video.

This implies that the system uses at least one type of optical range finder. But does it use a rangefinder that has two lenses and "does the math" by using parallax?

How did battleships during the Battle of Jutland, in 1916, compute the distance to targets 10 miles away, and more? Long before radar. They used optical rangefinders.

An Argo rangefinder unit (1912)

https://www.jutland1916.com/tactics-and-technologies-4/range-finding-and-course-plotting-2/

A selection of (passive) optical rangefinders from the 30s and 40s.

HMS Revenge

Bismarck

Artillery

FLAK

Article on coincidence rangefinders.
https://www.mathscinotes.com/2013/08/battleship-rangefinders-and-geometry/

How do humans determine (relatively nearby) distances? Depth perception. We have two eyes. Parallax. Pretty common knowledge.

Question: Does the system in question use an optical range finder that uses two lenses and parallax?

Or does it "do the math" only when it recognizes a known aircraft; using the known dimensions of the aircraft. This type of system doesn't use parallax and only needs one lens. (Cheap golf optical rangefinders use the known height of the pin and have just one lens.)

If this is the case, the computer must have thought it recognized the object; (using TV mode?)

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Domzh

Active Member
i cant see how it can accurately estimate range without a laser. it also only has one LOS.

it needs to know the size of the object.

maybe it just assumes an average size for A/A objects that you would usually dogfight with, plus/min 40 feet and guesstimates its range.

we now have multiple fighter pilots dismissing the range value. CWL clearly does not have an ET bias and he doesnt seem convinced by the range value either.

i am all for calling authority bias when it comes to misinterpretation and human error but in this case, thats not something linkable to human error. thats experience. if multiple construction workers tell me they cant actually use the screwdriver part of a swiss army knife for serious work, i believe them.

Z.W. Wolf

Senior Member.
WWII gunsights used in fighter aircraft and in bomber gun turrets used a ranging system that depended on the pilot or gunner recognizing the enemy aircraft and setting the gunsight for that type of aircraft.

This is too complicated to summarize in words. So I'll refer to this YT video.

(The gunsight used a mechanical analog computer.)

The computer in the system now in question (on the F-18) can recognize aircraft on its own. If this is the only type of passive optical system it uses... since the system provided a range - 4.4 miles - the computer must have thought it recognized the object.

OR does it also have a two lens system that uses parallax? The WWII era rangefinders in the photos in my last post are sizable, but with modern optics and a digital computer to do the processing, it could be much smaller. But does it exist? I don't know.

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