Sitrec Wind

[Mick West]

I've started to add wind to Sitrec

Currently, it's just the relative wind speed of the clouds.

This can be confusing.

I'm assuming the jet starts out going North (0°). The wind is reported as "120 knots from the West" - and I'm assuming that's the local wind velocity - i.e. in the air mass that the jet is flying in. Now all the calculations are done relative to airspeed, and previously assumed everywhere the wind was the same. So it makes no difference to the relative position of things what the wind actually is. So it's set to zero.

The jet is at 25,000 feet, but the clouds are at 9,500 feet. So it's safe to assume they are moving a lot slower. So, relative to the jet their motion is largely in the opposite direction to the local 120 knot wind vector from the west (270°). So here I have it at 80 knots from the east (90°), which is equivalent to 40 knots from the west.

I will probably change this to have one vector for local wind and another vector for cloud wind, but this is a useful start.

It does not really make much of a visible difference, but I've not studied it much.

The "fleet" is "all going against the wind", which is another complication.

This might be a factor in both GoFast and FLIR1. Possibly even Aguadilla, where the wind speed is a very interesting factor (but probably won't affect the plane much)

 

[Mick West]

I've added local wind (blue arrow) and cloud wind (white arrow) as separate vectors in all three ATFLIR videos (clouds only in Gimbal)

https://www.metabunk.org/sitrec/?sitch=gimbal

The length of the arrow indicates the total contribution of the wind over the entire track

This is VERY MUCH a work in progress, but quite interesting
Object speed now shows ground speed (green, like grass) and air speed (blue, like sky)

 

[Ravi]

Mick, perhaps you can dive into wind speeds a bit more using altitude resolved data from the Aeolus satellite.. I believe it is free.

https://aeolus.services/

 

[TheCholla]

Great additions, lots of things to analyze when playing with the wind.

Based on the audio ("going against the wind"), and the fact they are sure they were tracking an object within 10Nm, (based on what R. Graves and the WSO, indirectly, has said), this constrains the local wind direction. We expect it to be more or less facing the F-18 towards the beginning, something like [320;50] local wind direction in Sitrec, roughly.
Agree?

EDIT: seeing now it's set up with 340 local wind direction by default, seems right. The close flight path has to go more or less against the westerly wind, based on what the aviators say, and what the WSO testified to senate staff members.

 

[Mick West]

For the cloud velocity, the cloud tops are around 9500 ft, which is around 715mb pressure. Using earth.nullschool.net
https://earth.nullschool.net/#2015/...ographic=-77.49,34.40,1077/loc=-78.508,29.105

Only 17 knot, from 250

Higher altitude 120 knots at 270 seems reasonable

https://earth.nullschool.net/#2015/...ographic=-77.49,34.40,1077/loc=-78.508,29.105

I think I'll have to add an "initial heading" setting for the jet, but right now, if the jet is facing east, and the radar targets are coming from the east, and they are going against the wind, then the wind is a tailwind for the jet. I don't think we can say that with any confidence, as initially, the jet and the radar target (assuming that's the actual object ) have parallel paths.

And the "all going against the wind" comment is ten seconds into the video.

Man, this is too confusing to convert mentally. I'll add the "initial direction" so other directions can be absolute

 

[Mick West]

. I'll add the "initial direction" so other directions can be absolute

Done. The green arrow is the initial heading of the jet (currently 315 default to make the fleet fly west using "straight line" traversal)

Wind is 120@270.

However this put the fleet to the west of the jet, which seems a bit odd.

 

[Mick West]

The addition of wind raises another issue. Is "Az" relative to the ground track (cyan curve) or to the roll axis of the jet?

I'm assuming relative to the roll axis, as that makes the most sense both from a technical and from a human factors perspective. However, some documentation says otherwise:

That would be another kettle of fish!

 

[TheCholla]

What would make sense, and this is what the documentation says:
- Az : relative to ground track
- Situational Awareness cue dot : relative to plane boresight

 

[TheCholla]

Safe to say including wind makes a lot of difference. Quick illustration:

The "ideal" flying-away jet scenario.
No wind, 31Nm, for constant speed. Not very straight, but tail angle more or less consistent with a jet flying away.

Now with 346-heading 120 Knots wind. Picked objectively based on the audio and the objects going "against the wind" (bogus radar returns or not). This means wind needs to be about parallel to the LoS around 10s, and going opposite direction to the LoS.

Tail angle increases substantially, and this is not consistent with a jet flying away anymore (it's not looking tailpipe at the jet engines, required for the glare theory).

Will have to look further, but it seems having a 120Knot local wind, regardless of the direction, makes it very difficult to find the 30-40Nm distant jet flying away (tailpipe).

 

[Mick West]

What would make sense, and this is what the documentation says:
- Az : relative to ground track
- Situational Awareness cue dot : relative to plane boresight

We already discovered an essentially perfect relationship between Az and Cue dot angle, where the Az is in the horizontal plane, and Cue dot is in the plane of the wings. However that's in the case where ground track and boresight are the same.

There was a discussion of the meaning of Az earlier:

So we've been working off some Navy documents that detail how ATFLIR is operated. In particular, A1-F18AC-746-100 states

Azimuth readout is the ATFLIR pointing angle left or right of aircraft ground track.

Now, to me, this never made any sense, at least for the Air-to-Air mode we're concerned with. It's adding a bunch of workload for the pilot who'll have to work out wind directions and speeds at whatever their altitude is in order to figure out where to go in order to find a target... that's probably subjected to the same wind he is anyway, so simply pointing the airplane towards him would be a much more expedient way to do it. So my assumption was that the manual was using imprecise language, and that the ATFLIR azimuths were referenced with respect to the horizontal projection of the aircraft velocity vector. This certainly makes more sense than it being the ground track, but if you think about it, ATFLIR is not just a thermal telescope, it's a component of a weapon system. The function of a weapon is to shoot things, in this case, missiles. If you want to shoot something like an AIM-9X at a target, you want to know how far off the aircraft boresight the target is to know if the missile can hit them or not. Furthermore, in an aircraft with integrated sensor systems, it'd be silly to have the FLIR pod and the radar work off different reference angles, and the radar azimuths are no doubt zeroed with respect to the boresight. So maybe the manual was right, but incomplete: perhaps the azimuths are referenced to the ground track when in air-to-ground mode, but to the boresight in air-to-air mode.

And DCS seems to have Az relative to boresight.

I'll look into adding a "Az relative to ground track", but it's a bit fiddly as right now to match the cloud motion (an absolute necessity for the end result of the sim) the turn rate is derived from the Az and cloud speed, meaning ground track is dependent on the Az - so a circular dependency. It's complicated.

 

[Mick West]

Will have to look further, but it seems having a 120Knot local wind, regardless of the direction, makes it very difficult to find the 30-40Nm distant jet flying away (tailpipe).

The "work in progress, results may vary" disclaimer very much applies here. However, it does make it easier to find one that's closer (20-30NM)! Although the perfectly straight line seems less plausible, a very slight curve or S-turn is all that's needed to have a very small tail angle.

 

[TheCholla]

The "work in progress, results may vary" disclaimer very much applies here. However, it does make it easier to find one that's closer (20-30NM)! Although the perfectly straight line seems less plausible, a very slight curve or S-turn is all that's needed to have a very small tail angle.

Will be interested to see which 20-30Nm path you are talking about.

This is interesting in regards to the discussion on probability of close versus distant flight paths, if the distant flight path is not extraordinary coincidental anymore (which never really was in my analyses).

An additional puzzle is that the reconstructed trajectories are relative to the F-18 ground track now, so we need to imagine them in their frame of reference, i.e. relative to their own local wind. Reducing wind speed to the expected wind shear between the two altitudes shows the "real" flight path of the object in its frame of reference, but this is approximate of course. This is my interpretation at least, let me know if I'm wrong.

 

[DavidB66]

they are sure they were tracking an object within 10Nm, (based on what R. Graves and the WSO, indirectly, has said)

The redacted transcript of the WSO's evidence to Congress staffers doesn't seem to give a distance, though there is a redacted passage (following the word 'approximately') which could well contain a relevant figure. Ryan Graves has probably mentioned the 10NM figure somewhere in his various public comments on the subject, though on a quick search I couldn't find it. However, the Gimbal video itself shows no range data, and Graves's estimate may depend on the assumption that the object tracked by the ATFLIR was one of the objects shown on the SA screen (the 'fleet'). As in the case of FLIR1 and the Tic-tac, the assumption seems weakly based, as the object shown in the video doesn't do anything like the claimed behavior of the 'fleet', just as the FLIR1 object doesn't do anything like the Tic-tac. The redactions in the transcript seem designed to conceal any information about how the objects were located and tracked (by radar or otherwise), but the redactor has (deliberately or not) let slip the statement that 'The staffers also asked [redacted] if he knew if the [redacted] observed the unidentified craft via radar as he did' (italics added). I'm guessing that the first 'redacted' refers to Graves, while the second is 'Weapons Systems Officer'.

 

[jarlrmai]

My understanding is that Graves was neither the pilot nor the WSO in GIMBAL. He was not in that aircraft. He claims to have spoken to the actual crew and to have seen a longer ATLFLIR video and a recording of the SA screen.

 

[DavidB66]

My understanding is that Graves was neither the pilot nor the WSO in GIMBAL. He was not in that aircraft. He claims to have spoken to the actual crew and to have seen a longer ATLFLIR video and a recording of the SA screen.

I agree, he was not in the same aircraft. In a recent interview (below) he says he was part of the same exercise, and specifically that he was 'airborne for that one' (i.e. the Gimbal case). I took this to mean that he was watching the same SA page in real time, but it's not entirely clear. Maybe he watched a recording later, or maybe both. He description does suggest that he had time to review and memorise the incident in detail. The transcript of the Congress investigation (by Senate staffers, I think) implies that they interviewed at least two people, one of whom was definitely the WSO who took the Gimbal video (therefore not Graves), and one someone else. I guessed it was Graves, as he has been publicly forthcoming about the case, but maybe it was the actual pilot (identity unknown) or someone else who saw the radar data. Dimebag2 follows this case much more closely than me, so he may know!

The video here is a relevant extract from a longer interview of Graves by Lex Fridman:


Source: https://www.youtube.com/watch?v=wCT3HdHokaw&t=11s

 

[TheCholla]

R. Graves was in the squadron who was training when Gimbal was filmed. It was dark and they were all coming back to the carrier. One F-18 from their team went to check weird radar returns, and got the Gimbal video. After they were back, the whole squadron gathered to watch the tapes (FLIR and SA/radar), so more than 2-3 people saw it. The admiral checked it out too. This is what Graves had said in his tweets, and the story he tells in interviews I joined.

R. Graves is good friend with the WSO, they talk regularly, and in March he asked him to confirm the range he had on his instruments. See tweet below.


Source: https://twitter.com/uncertainvector/status/1508144005871153155?s=20&t=6aSE36PFWD_JynzFYMzYLw


When watching the tapes, they noticed the object following the fleet stopped and reversed direction, as indicated by the target velocity vector flipping direction abruptly on the SA.

 

[jarlrmai]

Graves' SA would have shown a different perspective to the recording jets SA, has he ever spoken about that? SA is ownship centered.

 

[TheCholla]

He only mentions seeing the tapes from the aircraft that filmed Gimbal. They were busy on other things when it happened and weren't checking the objects on their own instruments.

 

[aware]

And DCS seems to have Az relative to boresight.

From chucks guide for the f18 in dcs https://www.mudspike.com/chucks-guides-dcs-f-a-18c-hornet/ . Also i have dcs and the f18 and from experience, it is the degrees L or R of the nose of the aircraft but it could be different irl.

 

[TheCholla]

Very interesting things when looking at the effect of wind. Here I am focusing on scenarios that take into account what the aviators report.

Here is a scenario with the close flight path at ~8Nm, and the 120-knot wind coming from top-right, i.e. facing the object's direction. In this scenario the object would take a vertical U-turn when the rotation happens (around frame 900), as seen by the blue curve going to zero speed. But with wind effect included, the object would stop a bit earlier than that on the SA, around frame 750, as seen in its ground track (green curve). Maybe it explains why there is a bit of confusion about when the stop happened on the SA, relative to the rotation on FLIR, and the fleet's turn. Altitude increase is less than before, ~200ft.

Another interesting scenario is the following. If we consider the WSO is talking about the fleet when saying "they are going against the wind" (which is very possible because he says "there is a whole fleet of them" just before), the wind would come from top of the screen, facing the fleet while it turns left on the SA, to the left of Gimbal's direction. In that case the F-18 is heading North at first, and facing West (headwind) after turning towards the object.

This scenario looks like this :

Here we still see a stop on the SA (ground track, green curve), around when the object rotates on the FLIR. But the object does not need to stop, it rapidly decelerates from ~500 Knots to under wind speed, making it appears like it stopped/reverses direction on the SA (blue curve). Interestingly, the object does not have to gain altitude, see altitude graph.

This scenario would reconcile both sides of the argument, with the rotation being a camera artifact, but the object having an anomalous flight path, basically stopping mid-air, as the aviators have reported it. It does not explain the change in size/shape though, as the F-18 don't really get closer to the object. The aviators report they got closer and stopped tracking the object because of fear of collision. A point for the first scenario.

If we can clarify when exactly the stop happened, and what the WSO is referring to when saying 'they're going against the wind', we can further refine between these scenarios.

I'll let others look into distant plane scenarios, I'm focusing onto these close flight paths to explain what the aviators report.

 

[Mick West]

From chucks guide for the f18 in dcs https://www.mudspike.com/chucks-guides-dcs-f-a-18c-hornet/ . Also i have dcs and the f18 and from experience, it is the degrees L or R of the nose of the aircraft but it could be different irl.

And, not the most authoritative source, but TTSA also have it relative to the jet's axis (not ground track)

I think that the perfect correlation of the cue dot angle (in the plane of the wings, relative to boresight) and the Az angle (in the horizontal plane) matching perfectly through the entire 60° of turn relative to 120 knots of wind indicates that it's not measured relative to the ground track. So on reflection, I don't see a need to do a ground-track relative version.