Velocity Vector (HUDD)

[Andúril(Flame of the West)]

Very Simple Question. On the Velocity Vector on the Hud, when especially landing, what does it mean when the Velocity Vector Flashes or is not constant? It acts as though it is sensing not enough velocity. When I increase power, it does return to a constant symbol. I ask this because I could not find anything about it, and sometimes it does not act as though it has anything to do with too low of velocity, in other words, the plane may stall. Can someone explain? 

[Rudel_chw]

58 minutes ago, Bizzy said:

Velocity Vector Flashes or is not constant

maybe you are confusing it with the waterline symbol? The ww flashes when pitch attitude on landing exceeds 13º, as a warning that at 15º you may strike the jet pipes on the runway.

[MagicSlave]

I think the velocity vector flashes when it is outside the HUD field of view. I.e. during landing, if the VV is just below the HUD FOV when slow and high AOA

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[Rainmaker]

1 hour ago, MagicSlave said:

I think the velocity vector flashes when it is outside the HUD field of view. I.e. during landing, if the VV is just below the HUD FOV when slow and high AOA

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This. 

[SharpeXB]

I get the impression that the VV is flashing when you are at the correct on-speed AoA of 20-22 for landing. I haven’t found this described in the manual. 

Edited January 12, 2024 by SharpeXB

[MagicSlave]

I get the impression that the VV is flashing when you are at the correct on-speed AoA of 20-22 for landing. I haven’t found this described in the manual. 

No, it flashes when true velocity vector would be out of HUD field of view.

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[SharpeXB]

3 hours ago, MagicSlave said:

No, it flashes when true velocity vector would be out of HUD field of view.

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That’s what I thought at first, but that’s not it. Tested it again and yeah it starts flashing at 21.3 AOA. It will flash even above the horizon line when it’s clearly in view. 

[Rainmaker]

1 hour ago, SharpeXB said:

That’s what I thought at first, but that’s not it. Tested it again and yeah it starts flashing at 21.3 AOA. It will flash even above the horizon line when it’s clearly in view. 

How exactly are you getting 21.3 AoA (HUD is CPU FWIW) and a VV still in the in plane view in the HUD?

And horizon line has nothing to do with it.

Edited January 12, 2024 by Rainmaker

[SharpeXB]

15 minutes ago, Rainmaker said:

How exactly are you getting 21.3 AoA (HUD is CPU FWIW) and a VV still in the in plane view in the HUD?

And horizon line has nothing to do with it.

 

Trimming for AoA like this. The two screenshots catch it flashing. The point about the horizon line is that if the VV is on that then it's obviously not out of view. If I lower the AoA it stops flashing.

[Rainmaker]

21 minutes ago, SharpeXB said:

Trimming for AoA like this. The two screenshots catch it flashing. The point about the horizon line is that if the VV is on that then it's obviously not out of view. If I lower the AoA it stops flashing.

Yes, and you are at the point of being HUD limited.  That's the way its designed.

[SharpeXB]

29 minutes ago, Rainmaker said:

Yes, and you are at the point of being HUD limited.  That's the way its designed.

I’m not HUD limited, the HUDs view extends down at least to the -5 pitch ladder. The VV is right in the center, well within the HUD. Try it for yourself. Keep it in the HUD the whole time and just gradually adjust your AoA. It will be solid until your AoA increases then it will start flashing at about 21.3. Decrease AoA and it will go solid again.

Edited January 12, 2024 by SharpeXB

[Ignition]

The VV flashes when it's on the limit of the HUD and beyond.

It shouldn't be used as a reference for AoA.

Edited January 13, 2024 by Ignition

[MagicSlave]

I’m not HUD limited, the HUDs view extends down at least to the -5 pitch ladder. The VV is right in the center, well within the HUD. Try it for yourself. Keep it in the HUD the whole time and just gradually adjust your AoA. It will be solid until your AoA increases then it will start flashing at about 21.3. Decrease AoA and it will go solid again.

Where the HUD FOV limits are in relation to the glass will vary with your head position, as the projection is collimated to infinity and will remain static in relation to distant objects, rather than the combiner glass. I guess to get a definite answer, you would have to ask an SME about the meaning of VV flashing, as there is no explanation in the manual. However: 1) it is pretty important to indicate to the pilot that the VV displayed in the HUD is not accurately representing the true direction of travel anymore:; 2) the other US aircraft also indicate when the true VV is out of FOV, such as "X" superimposed across the VV in F-16C.

That is why my bet is that the flashing indicates that the VV is out of HUD FOV. I guess you could check if the flashing continues beyond the optimal landing AOA, for example... This is just my reasoning, I have no sources for this

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[Rainmaker]

24 minutes ago, SharpeXB said:

I’m not HUD limited, the HUDs view extends down at least to the -5 pitch ladder. The VV is right in the center, well within the HUD. Try it for yourself. Keep it in the HUD the whole time and just gradually adjust your AoA. It will be solid until your AoA increases then it will start flashing at about 21.3. Decrease AoA and it will go solid again.

 

You are HUD limited.  The VV indicator is not meant to go all the way to the edge. iIRC, it a few degrees from it.  I dunno what else to tell you.  It’s not related to AoA. 

[SharpeXB]

30 minutes ago, Rainmaker said:

You are HUD limited.  The VV indicator is not meant to go all the way to the edge. iIRC, it a few degrees from it.  I dunno what else to tell you.  It’s not related to AoA. 

I can make the VV go from solid to flashing and back to solid while it remains in the HUD the whole time. If the flashing isn’t meant to correspond to AoA it sure seems that way. You could sure be fooled thinking it’s some sort of AoA indexer for landing because it starts flashing at exactly that AoA. Not saying that’s correct but it’s what I see. Maybe it’s a bug. 

Edited January 13, 2024 by SharpeXB

[SharpeXB]

48 minutes ago, Ignition said:

It shouldn't be used as a reference for AoA.

Well it does actually relate to your AoA because the distance between the VV and the Waterline Symbol is exactly that. The farther apart those are, the greater your AoA and vice versa. 

Edited January 13, 2024 by SharpeXB

[Rainmaker]

6 minutes ago, SharpeXB said:

I can make the VV go from solid to flashing and back to solid while it remains in the HUD the whole time. If the flashing isn’t meant to correspond to AoA it sure seems that way. You could sure be fooled thinking it’s some sort of AoA indexer for landing because it starts flashing at exactly that AoA. Not saying that’s correct but it’s what I see. Maybe it’s a bug. 

 

Its going to. Its a fixed FOV with a fixed waterline. Its always going to do it at the same AoA. That doesnt mean its built to correspond that way. It also does the same with drift. Its meant to say the VV is at the edge of the limits it was designed to be accurate for. That’s all. 

Edited January 13, 2024 by Rainmaker

[Ignition]

Just now, SharpeXB said:

I can make the VV go from solid to flashing and back to solid while it remains in the HUD the whole time. If the flashing isn’t meant to correspond to AoA it sure seems that way. Not saying that’s correct but it’s what I see. Maybe it’s a bug. 

 

I believe it's just a coincidence. Imagine the consequence if the VV goes beyond the HUD and the pilot believes he's in the correct AoA just because it's still flashing with 30 units.

The flashing in fact it's a warning that the VV may not be trusted and not because it's the correct AoA.

[SharpeXB]

I’ll have to post a track or video to explain this. You can see the behavior clearly when doing the landing pattern. On downwind when you’re flying level and therefore the VV is fixed on the horizon line, start increasing AoA to the required 20-22 and you’ll see it start flashing without leaving the HUD. 

[SharpeXB]

Aha. I get what’s happening. The VV has a boundary or limit that’s separate from the other HUD elements. So it appears to be within the HUD when it’s actually outside it. It’s at the edge of its own limit and therefore flashing. When you’re trimmed for the approach and flying level that limit nearly coincides with the horizon line. 

Edited January 13, 2024 by SharpeXB