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HUD symbology help

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toom317
Posts: 1936
Joined: Tue Nov 10, 2009 7:31 pm

HUD symbology help

Post by toom317 » Wed Sep 29, 2021 9:27 am

Cross over from a mess post as someone said you Sim guys might be better placed to help me with this.

Screen grab from a video of a Jaguar GR3/3A. I've worked out most of the info but need some help with 8 items of information displayed in the photo.

Image

1- The inverted chevron at the centre top of the pic. Is this indicating the magnetic heading in relation to the true heading, or something else altogether? In the video, it doesn't deviate much either side of the centre indicator.
2- The two sets of data displayed, I can't figure out.
3- In the video, the arrow points in different directions and the numbers change throughout the flight, and again I can't figure it out.
4- Not a clue. Possibly to do with speed, but it doesn't change as rapidly with the change in Knots as the GS figure below it does.
5- I think this is to do with speed, Ground Speed in MPH as opposed to Knots displayed above the Mach No. at the top left. It does change rapidly as the Knots change.
6- No Ground Power/ Kilo Volts?
7- The 282 degrees is in connection with the horseshoe icon at the top right of centre, and indicates heading and direction to the next way point. I can't figure out what the G0050 /G005G means though.

Also forgot to number this while editing the pic, between 1&2 on the left, is a > symbol attached to what looks like a Yellow "L" . This doesn't move all that much, unlike the one on the other side, which shows rate of climb.
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Captain Kirk
Posts: 1
Joined: Mon Oct 18, 2021 8:12 pm

Re: HUD symbology help

Post by Captain Kirk » Mon Oct 25, 2021 10:52 am

HUD

Hi there - I stumbled across your post, looking for an image of a Jag HUD to show someone - I can answer most of your questions… :)

1. This is the ‘Track Index’ and displays ’True Track’ over the ground, i.e. the True Heading adjusted for wind effect…
2. I’m a little rusty on this one - it had no direct use in flight but IIRC it displayed a measure of navigation accuracy and could be used post-flight for analysing kit errors, etc. I think the last 5 digits might be height above the terrain database model of sea level.
3. This is the ‘Wind Index’ and shows relative direction and strength - in this case a wind of 6 knots from 7 o’clock, which accounts for the drift (Track Index to the right of Heading) and the slightly higher Groundspeed than IAS.
4. Demanded Ground Speed - the speed need to fly to arrive at the selected Waypoint on time. The active waypoint bears 282 degrees at 13.4 nm (see item 7) and to arrive there at the time loaded against that waypoint (by the pilot - not displayed in the HUD) would require a straight line speed (i.e. not taking not account any turn that is required) of 204 knots. In this case the aircraft is heading south (i.e. not pointing at the waypoint) and so the DGS will steadily increase.
5. GroundSpeed - 271 knots, and because this is in excess of the DGS, the aircraft would arrive at the active waypoint 58 seconds Early if it were to fly a track of 282 deg and maintain 271 knots groundspeed. In reality, by the time this aircraft had turned 90 right it would be showing about 40 seconds early, noting too that it will have more tailwind on the new heading. Arriving over a target exactly on time without ‘chasing the speed’ required judgement as to when to initiate the final turn onto attack heading - aiming to maintain attack speed for weapon delivery.
6. No Ground Proximity Warning (likely disabled) - K and V are measures of kit performance with (IIRC) K indicating a good Terrain Referenced solution and V indicating a good GPS solution.
7. Waypoint bearing and range (below) and G0050 is the set height for the Enhanced Ground Proximity Warning to alert - a predictive warning, i.e. it alarms if the projected flight path impinges the set height.

The > on the left indicates Angle of Attack, each dot representing increments of 4 deg - the double dot at 12 indicates the optimum AoA to fly an approach. It will increase turning a turn and/or as the aircraft slows down in level flight.

Hope that helps! :)

CK

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