HUD acceleration vector after last patch

[bkthunder]

After the last patch 1.5.4, the acceleration vector is no longer accurate.

In a climb, my airspeed was going down, but the AV was above the FPM.

Mach number was also not increasing during the climb.

[SCU]

The acceleration vector behaviour was changed in the last update to better suite its real version. Maybe something was broken while doing that. I haven't experienced what you described after the last patch personally, better wait for a dev response.

[bkthunder]

Hey bkthunder do you have a track? I did a couple climbs and couldn't get to do what you are seeing, might be a specific conditions I'm not meeting to make it happen.

 

I don't have actually, it was MP on the 104th and I'm away from my pc until the weekend.

I'll try to replicate the situation and send you a track if I can this weekend.

[Rlaxoxo]

I have the same problem the Acceleration chevrons are above the FPM while in a 10 degree climb but I'm losing speed

[Azrayen]

Well, Rlaxoxo, then perhaps you can procure a track to CptSmiley?

[Rlaxoxo]

I'll try when I get home

[jojo]

I have the same problem the Acceleration chevrons are above the FPM while in a 10 degree climb but I'm losing speed

 

How is Mach number ?

[Rlaxoxo]

Here's the track for CptSmiley Showcasing the issue

FPM - Test.trk

[jojo]

Here's the track for CptSmiley Showcasing the issue

 

Yes, but Mach speed is constant or slightly increasing...

[Rlaxoxo]

Yes, but Mach speed is constant or slightly increasing...

 

It's increasing no matter if the Chevrons are slightly above the FPM or below it

 

Test 2 Track with clean Load same problem

FPM - Test 2.trk

[jojo]

The chevrons aren't about speed, but total energy, meaning acceleration.

 

Doing test in climb is complicated, because of decreasing air density. With the same ground speed, your IAS will reduce while you climb and your Mach number will increase.

 

So far, excepted travel amplitude, I don't see any change in chevrons behavior.

[Rlaxoxo]

The chevrons aren't about speed, but total energy, meaning acceleration.

 

Doing test in climb is complicated, because of decreasing air density. With the same ground speed, your IAS will reduce while you climb and your Mach number will increase.

 

So far, excepted travel amplitude, I don't see any change in chevrons behavior.

 

Well when you're in a climb you're losing speed hence not accelerating meaning not counting the Potential energy

[jojo]

It depends the climb angle and throttle position...

As long as > < are above -O- you're not loosing energy, you have excess.

 

You're in full afterburner in your test, all along !

 

No bug here

p66

[url]http://www.developpement-durable.gouv.fr/IMG/pdf/hudF.pdf[/url]

 

Easier to use than to understand :smilewink:

Edited August 23, 2016 by jojo

[bkthunder]

JoJo, I don't peak french so that document isn't very understandable for me.

Are you basically saying that the AV is not about airspeed, but takes into account mach number or ground speed as well?

 

As a side note, during my climb, I wasn't using A/B, and I was definitely loosing airspeed, but the AV markers were way above the FPM.

[jojo]

You have math formula P66.

The energy chevron are about longitudinal acceleration.

It's more reliable than speed because at constant ground speed speed IAS will decrease with altitude while Mach speed will increase because of air density change.

 

And what does "climb" means ?

10 degrees, 20, 30...70 ?

[Luzifer]

The chevrons aren't about speed, but total energy, meaning acceleration.

 

That's not quite accurate, total energy means, well, total energy. The sum of kinetic (speed) and potential (altitude) energy. If you're flying level, then pull into a climb, then level out again without changing the throttle, you should have decelerated from the climb. Yet the total energy is still the same, you just converted speed to altitude.

 

If you climb at a constant forward and vertical speed, total energy is increasing even though there is no acceleration at all.

 

So when the chevrons now display total energy, OP's observation that the chevrons are above even though the speed drops just means that the gain in potential energy is larger than the kinetic energy loss.

[jojo]

That's not quite accurate, total energy means, well, total energy. The sum of kinetic (speed) and potential (altitude) energy. If you're flying level, then pull into a climb, then level out again without changing the throttle, you should have decelerated from the climb. Yet the total energy is still the same, you just converted speed to altitude.

 

If you climb at a constant forward and vertical speed, total energy is increasing even though there is no acceleration at all.

 

So when the chevrons now display total energy, OP's observation that the chevrons are above even though the speed drops just means that the gain in potential energy is larger than the kinetic energy loss.

 

Ok guys, you want to know, read the math in pdf above. No need to read French to read math formulas...

 

Moreover, what you wrote is wrong. You won't convert all the speed lost into altitude gain because of the drag.

Edited August 25, 2016 by jojo

[Rlaxoxo]

Ok jojo chill man

[Frederf]

The chevrons aren't about speed, but total energy, meaning acceleration.

 

This makes no sense to me. Total energy is not determined by acceleration. Total energy is a function of height, speed, and mass. A constant-speed, constant-height airplane will be losing energy (Joules) as it burns fuel. The airplane is losing potential energy (height x mass) and kinetic energy (speed^2 x mass).

 

To not be sloppy by language we must be more careful about our use of terms. Replace total energy with total specific energy. OK, this is energy per unit mass (Joule per kg). A constant-height, constant-speed airplane is constant specific energy even as fuel is burned. Total energy is decreasing but so is mass and the ratio remains constant.

 

OK, total specific energy can be thought of as a sum of the contributions from potential (height) and kinetic (speed). Holding both constant produces a constant value of the sum but there are a variety of changing speeds and heights which result in decreasing, constant, or increasing TSE.

 

What is speed? Airspeed isn't it. Mach isn't it. True airspeed isn't it. Speed is presumably measured with reference to the Earth, aka ground speed. Speed is also directional, forward, right, or up (negatives being back, left and down). So we have to ask is this total speed or longitudinal acceleration.

 

So are the "energy carets" in the Mirage 2000:

1. Showing changes in total energy?

2. Showing changes in total specific energy?

3. Showing changes in total speed?

4. Showing changes in longitudinal groundspeed?

5. Showing changes in total/longitudinal true airspeed?

6. Showing changes in total/longitudinal indicated airspeed?

[jojo]

Stop this and go page 66

 

http://forums.eagle.ru/showpost.php?p=2883041&postcount=14

[jojo]

Light explanation in English by Airbus

 

[url]http://www.airbus.com/fileadmin/media_gallery/files/brochures_publications/FAST_magazine/fast46-7-headup-display.pdf[/url]

 

"Total Energy Chevrons"

[Luzifer]

Moreover, what you wrote is wrong. You won't convert all the speed lost into altitude gain because of the drag.

 

Well duh, there's always drag. There's drag in level and constant speed flight. There's also engine thrust counteracting the drag.

 

This is completely independent of the fact that altitude can be converted to speed and vice versa. That's the reason the total energy concept is so useful.

[Luzifer]

I can't quite read understand the French but the diagrams (including the Airbus one) make me think that the chevrons are centered on the horizon line, not the FPV, and furthermore the deviation is scaled so that they coincide with the FPV when speed is constant.

 

If that is the case, that would mean that deceleration in climb showing the chevrons above is indeed wrong. In this situation, if the total energy gain is still positive the chevrons should be above the horizon but below the FPV marker.

 

 

Edit: Oh wait, the relevant speed for kinetic energy would be TAS. Can't say if that makes enough of a difference to be noticeable.

Edited August 26, 2016 by Luzifer

[Sarge55]

Math isn't my strong suit so all I ask is once it's sorted out :book: you pass it onto us laymen in a simple format.

 

Like;

 

chevron above = going faster

chevron below = slowing down

 

:thumbup:

[Luzifer]

Basically the total energy is converted to a virtual altitude H and the chevrons show the "flight path" in reference to that virtual altitude. If only altitude changes and speed doesn't, the path angles of both H and real flight are the same and the chevrons appear next to the flight path marker.

 

If speed is increasing the chevrons are above the FPM. If total energy is increasing the chevrons are above the horizon line.

 

That's what the formulas in the French document say, I don't know if RAZBAM has now implemented it exactly like that.