True Airspeed indicator bug

[hitech]

Not sure why you think the Away from wind looks strange. Your numbers are exatly what the TAS is by deffinition.

The deal is your thinking of TAS as a computed TAS as a pilot would, not by the definition of TAS as if it was computed perfectly.


HiTech

[Orig]

More notes:

When I took off in the zeek with zero wind and then added in 127 knots of headwind, the groundspeed remained constant but the airspeed increased by 127.  This appears to indicate that the flight model is referenced relative to the ground and not the air mass, but I can't possibly know for sure unless HiTech spills some secrets.  

I rather thought that the flight model would be referenced to the air mass and the relative motion over the ground would be based on the final results of the aero calculations, but it seems like the plane is referenced against the ground and it is the aero calculations that must be adjusted to take wind and motion through the air into account.  Wouldn't the aero calculations be easier if all motion was referenced to the air mass and not the ground?

The weird behavior of the IAS/TAS needles and the other behavior seems to point to the motion being referenced to the ground and the aero calculations must be adjusted to take wind into account, which must be a very complex task.  If the plane simply flew through an air mass and then only the motion across the ground was adjusted based on how that air mass was moving across the ground, it could simplify some things.  It would also allow environmental effects such as thermals and other vertical wind motion.  There would have to be a constant translation in positional reference coordinates since a motion of x feet through the air in any direction would not translate to a motion of x feet through the ground-referenced coordinate system, but that translation would be applied once instead of having to apply a wind vector to all of the calculated aero forces.

Or maybe it's already being done this way, and something else is causing the behavior I noted above. and HiTech is laughing at me for making a fool of myself.

Pointing and laughing at me is ok, I'm somewhat used to it

[hitech]

Orig. Tel me the diffrenect in TAS between these 2 situations.

The plane is in a 50 mph tail slide with no wind.

The plane is sitting still on the ground with a 50 mph tail wind.


HiTech

[Orig]

HiTech,

I think I see what you are talking about, finally.  My confusion was probably due to the fact that on the ground, there is no way to easily see crab angle so if there is a takeoff with a crosswind and the nose is kept pointed down the runway, the IAS will be lower than the displayed TAS until the plane lifts off and crabs into the wind, so unlike coordinated flight in the air, the plane is not moving straight into the relative wind.

So now that I see where the TAS is coming from, we're back to me wondering how a WWII pilot would get such info  Reverse calculating it back from the IAS might be more consistent and avoid idiots like me from pestering you with stupid questions.

Thanks for being so patient with me.  I hope I have not wasted too much of your time or needlessly annoyed you.

[Waffle]

So basically the TAS seems to be an Anemometer, measuring wind speed, whatever direction?

[Orig]

In the general sense, there is no difference.  The only question is if a pilot would have any indication of the backwards motion through the air other than possibly his exhaust streaming forwards instead of backwards.

There is of course an aerodynamic difference between wind flowing forward or backwards across a wing and control surfaces, and having the same TAS displayed for both head and tail relative winds confused me.  I'm used to thinking of motion relative to the air mass, with travel across the ground being a goal to be reached, so you're right, TAS to me is generally referenced from the nose because that's where the relative wind happens to be coming from in flight.  Any wind from the tail deserves a negative sign

I am hoping someone else can test what I noticed with the wind noise.  I turned my speakers way up and shut the engine off to make sure I was only hearing wind noise, and there was a definate difference between the wind noise heading upwind and downwind even though the indicated airspeed was the same at around 200-250.

[Waffle]

now sounds, that I can do...lol

Will go have a listen and see what i can discern

[hitech]

Orig.

IAS Indicated air speed , i.e. reading on pito tube.
CAS What the IAS should be reading with out errors in the pito tube system.
TAS What the planes real speed is relative to the air stream. Or CAS compensated for density.

      Now you normaly only think about those IAS errors at slow speed, and do to a small change in AOA at the pito tube, or by a small slip angle. You then look them up in a table and aply the correction. And then caclulate true air speed from that.

But then again what if you are in a tail slide, the problem isn't with what TAS is, the problem is that your table dosn't apply corrections for those situations. If you were to make a weather vaining pito tube so it always points directly into the wind no mater what direction the plane was flying , i.e. sidways , back wards what ever.

Then IAS and CAS would always be equal.

So the thing that your strugling with is comming up with a CAS at very unusal attidues. No matter what attidude the plane is flying in TAS and CAS will always remain constant.

HiTech

[Orig]

You are correct sir.  Now that I understand exactly what we're talking about, I fully agree and thank you for taking some time educating me.  I understood the definitions, but I was having a hard time seeing how they were working in the game.

Some of my misunderstanding was probably caused by trying to experimentally figure out what is going on in the game by adjusting and testing things beyond the conditions you designed the game to properly model.  For example, flying a zeek around in 127 knots of wind is not likely the conditions where you have spent a lot of time to make the ground handling work right, so a 127 knot wind pushing a zeek backwards at 100 knots when the throttle is slightly above idle is not a useful place to go trying to understand how the game models things

The ground handling at various speeds in a crosswind that changes depending on if the throttle is fully back in idle is a totally different subject and probably not worth discussing since it only feels weird in extreme situations, if the throttle is not calibrated properly to go all the way back to full idle, or if the throttle is moved out of idle and back to idle a lot while taxiing or landing in a crosswind.

Waffle's original question still remains and I'll slightly rephrase it - Why is perfect TAS displayed in AH planes since this does not seem to be consistent with the detailed realism you and Pyro are careful to maintain in other areas of the simulation?  It is no more than an academic question to me since I'd rather a game be fun than 100% realistic, but Waffle is still scratching his head and looking at me funny so I figure I'd try to get the thread back to his question  

[Waffle]

Sounds: -

127 North wind offline

Flew into the wind up to 200+ IAS/TAS no wind sound.
up and over with the wind...200+ -  wind sound on.
Down and back into the wind 300+ IAS / TAS - no sound

In set up, turn your engine sound off as well as you external engine sound. Then you can listen only for wind.

Which brings me to a HIJACK:

Hitech, I noticed that you have volume control for both internal engines and exterior engine sounds. I was messing around editing some sounds , and was able to use stereo engine sounds in cockpit. only problem - the external engine sounds use a mono source, so no external engine sounds.

What's the possiblity of adding a seperate mono external engine sound?

[Orig]

Waffle,

So... it sounds like flying into a headwind reduces the volume of the wind noise?  Interesting.  Maybe someone should report that in the bug forum

Is it possible for someone to hijack their own thread?

[Waffle]

Actually orig, it plays a set volume, unless there is something coded in that changes the volume, like the doppler, and posistion of sounds from external sources.

Basically, it doesn't start the loop when into a headwind.

Maybe this sound is triggered by speed relative to the ground or is that velocity?


 

[Orig]

I know almost nothing about sounds in AH.  Some like hit damage I turn all the way up, some like voice comm I turn all the way down.  That's about as far as I go with sounds

[hitech]

Orig. The answere to that question is simple.

Before we had put that in the game, every clueless tom dick and harry would claim our planes didn't fly fast enough. They would read some book saying the p51 went 450 mph, then couldn't figure out why AH's would not go faster than 360 mph.

Of course they had no idea what tas vs ias was, hence we put the conversion in there for them. As to realism, no it is not real, I don't know of any plane that has a TAS needle.

As to how pyro and I view realism, you almost have it, but we never like to put nusiance realism in the game unless it serves some other purpose. I.E. Like adding auto pilots to the planes, most didn't have it, but hey I realy don't want to force people to stay at there screen when they need to take a pee.

So when it comes to performance and handling of flying aircraft we don't comprimise. When It comes to things like gauges and stuff we do.

HiTech

[Orig]

Thanks for the explanation!