vertical speed indicator is inaccurate

[jp203000]

Especially when the pointer points to right below zero , the plane keeps moving up . This phenomenon can be seen during refueling .:huh: If you don't believe ,have a try .

Edited March 9, 2012 by jp203000

[EtherealN]

Do you have a track file to display this behaviour? ;)

 

As an aside, analog instruments lag, variometers in particular. They never give you a "perfect snapshot" if there is acceleration on any axis.

[jp203000]

Track.trk

Please have a look, when i was close to the tanker, the vertical speed pointer was below zero , but my A10 fly to the top of the tanker.

Edited March 9, 2012 by jp203000

[Inseckt]

Remember that the needle is not exactly "on" the background, it is in fact some millimeters "out" from the background, this may give inaccurate readings when looking at from an angle. It can even be seen in cars, when the driver and passenger would read the speedometer differently. This is also the case in DCS and I could imagine it could be substantial due to the (in some cases) high seating in the A-10. To get accurate reading, look at the VVI from directly in front of it (which may be hard to judge)...

[Wheel]

The VVI is acting correctly. When you pull up to climb, the VVI will show a descent due to gravity and show a climb when you push forward to descend. Once a climb or descent is established, the VVI will catch up and indicate your rate of vertical speed in accordance with power and pitch used. Think of it as if you have a glass of water setting on the dash of your car, accelerate and the water goes back, stop and the water goes forward.

 

Wheel

[Inseckt]

I think the above is dubious (no offense). Although I wouldn't be the right person to say anything for reference, I'm pretty sure the VVI don't have gravity (or acceleration) in it's input. I think it's simply connected to the pitot static system which are used to tell airspeed and barometric altitude. It then simply tells you the how fast said altitude is changing. If gravity or other forces is the reason for the behavior of inaccurate VVI, it would have to exert enough forces one the needle itself, to actually overcome the mechanical forces behind the gauge, which I believe on a small needle is, well, dubious (allthough EtherealN's statement suggests acceleration can affect the VVI, so I can't be 100% certain).... And to further shoot this statement down, the behavior explained above is the exact opposite of the behavior of the VVI in-sim. I you pull back hard, the the VVI will accelerate in a clockwise direction:)

 

Cheers

 

Edit: Not my intention to be hard on your first post. Welcome to the forums;)

Edited March 9, 2012 by Inseckt

[effte]

Most VSIs these days have an inertial compensation built in, essentially a spring suspended bobweight in a tube, adding a pressure difference as a climb/descent is initiated before the pressure sensing components are able to react. This adds in the right direction, i e up when pulling up (unless you are inverted, of course). This makes them IVSIs, Instant variometers.

 

No idea whats fitted to the Hawg - possibly it goes through the ADC. Check the dash one.

 

Cheers,

Fred

[Deadman]

the Warthog is fitted with an AAU-9A the specs are available on line.:thumbup:

[BlueRidgeDx]

Can't watch the track, but I'm thinking it's parallax. It's most evident on the engine gauges, but it's there on the VSI too.

[awdrgyjo]

Is this anomally exclusive to inflight refueling? if so, it could be due to presure waves produced by the tanker.

[Inseckt]

In RL: Perhaps but I doubt it to be enough to actually affect the VVI...

In sim: pressure waves, vortexes and other "wake" effects are not moddeled, so no..

[Inseckt]

LOL, I checked the track and the reason which has eluded us is perhaps the most obvious!

 

wait for it!... (drumwhirl)...

 

There is nothing wrong with the VVI. The tanker itself is descending! (I think the reason is it's starting altitude vs. it's next waypoint or It's starting speed is to low to sustain current altitude, (the tanker has a very high AoA...))

 

:megalol:

 

This is an example of where a prime assumption is erroneous and creates a wild goose-chase:)

 

Cheers!

Edited March 10, 2012 by Inseckt

[awdrgyjo]

In RL: Perhaps but I doubt it to be enough to actually affect the VVI...

In sim: pressure waves, vortexes and other "wake" effects are not moddeled, so no..

I think low pressure vortex is modelled, look at the leading edges when the wing is loaded, under high G for example.

[Inseckt]

I think low pressure vortex is modelled, look at the leading edges when the wing is loaded, under high G for example.

 

I'm afraid that is "simply" an animation and does not have any physical effects on other objects...

Edited March 10, 2012 by Inseckt

[mvsgas]

I think we should use the HUD more, and instruments as back up. the HUD provides more information, more accurately and faster.

[effte]

You're not supposed to use the HUD as your primary source. It's in the book.

[mvsgas]

What book? Primary source for what?

[BlueRidgeDx]

He's referring to the fact that the HUD is not approved for use as the primary source of aircraft attitude/altitude/airspeed data during flight in IMC.

 

There have been several cases where the HUD provided erroneous data causing Class A mishaps even though the electromechanical instruments were operating normally, simply because the pilot did not recognize the failure. See the F-15E crash off the coast of South Carolina, for one example.

 

Edit: Is it really possible to get the tanker to descend during AAR in DCS? If so, we can simulate the beloved A-10 "toboggan" maneuver.

Edited March 10, 2012 by BlueRidgeDx

[mvsgas]

Is the HUD going to break in DCS?

[mvsgas]

I found it, it is in AFI11-2A-OA-10V3

 

4.7. Use of the Heads-Up Display. The HUD may be used as an additional instrument reference in night/IMC conditions; however, do not use it as the sole instrument reference in these conditions. In addition, do not use the HUD to recover from an unusual attitude or when executing lost wingman procedures except when no other reference is available.

 

The way I understand this is, as long as your not flying at night or IMC, this really does not apply. Ether way, I still feel the HUD is a more accurate instrument than the rest.

One question, was this manual written before or after the A-10C enter service? It does not look like it has been updated, when did the A-10C start using the EGI? I did not see another 11- series manual for the A-10.

Edited March 10, 2012 by mvsgas

[effte]

Also says it's not a primary reference and not to be used for AS/alt during take off and landing either.

 

Edit: I e the A model -1.

Edited March 10, 2012 by effte

[BlueRidgeDx]

Yeah, the HUD fine for use in all conditions, just not as the primary source except during Day/VMC.

 

It applies to all airplanes*, not just the A-10. The problem is that the HUD is only a repeater, so a single point of failure can cause the entire HUD to freeze and display erroneous indications - which is exactly what happened to the F-15E I mentioned.

 

The A-10A had EGI for a while before the A-10C retrofit was complete and was known as the A-10A+ or "AIM". In any event, EGI doesn't make the HUD any more accurate, since it's simply a repeater and not an independant instrument.

 

*Edit: It looks like certain blocks of the F-16 with certain OFP loads can, in fact, use the HUD as a primary reference. It also looks like the F-22 HUD is certified too. The A-10, F-15C, F-15E, certain blocks of F-16C, and T-38 are not certified.

Edited March 10, 2012 by BlueRidgeDx

[cichlidfan]

Is the HUD going to break in DCS?

 

That, is the crux of the biscuit!:D

[effte]

You're free to play the game or use the simulator. Each to his or her own.

[mvsgas]

...It looks like certain blocks of the F-16 with certain OFP loads can, in fact, use the HUD as a primary reference...

I know bud, that is why is hard to relate to the way they do it on other aircraft for me I guess, I'm still a 16 guy.