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Posted

Hi all.

It seems to me that my IAS, and M/TAS instruments are lying to me. I was flying few times now to test it around 1 Mach and every airspeed indication seems to be off.

I was testing it at ISA conditions down low where 1 Mach should correspond to 1225km/h.

At IAS and TAS 1225km/h (few km/h deviation) machmetr was already showing 1,04M, but I was still not supersonic. Not to the point of IAS and TAS of about 1275km/h (few km/h deviation) at that point machmeter was at 1,05M and I was just barely supersonic.

It seems all airspeed instruments are showing more than they should.

Machmeter about +0,05M, IAS/TAS about +50km/h.

 

Any MiG-21 driver show the same, or is it just me? I cant recall exactly, but I think this was not happening before latest patch.

Posted
Hi all.

It seems to me that my IAS, and M/TAS instruments are lying to me. I was flying few times now to test it around 1 Mach and every airspeed indication seems to be off.

I was testing it at ISA conditions down low where 1 Mach should correspond to 1225km/h.

At IAS and TAS 1225km/h (few km/h deviation) machmetr was already showing 1,04M, but I was still not supersonic. Not to the point of IAS and TAS of about 1275km/h (few km/h deviation) at that point machmeter was at 1,05M and I was just barely supersonic.

It seems all airspeed instruments are showing more than they should.

Machmeter about +0,05M, IAS/TAS about +50km/h.

 

Any MiG-21 driver show the same, or is it just me? I cant recall exactly, but I think this was not happening before latest patch.

 

RL pitot-static systems are not 100% accurate, especially at transonic mach numbers due to weird airflow around the plane. You should re-test at lower speeds (400-600 km/h) and higher speeds (More than Mach 1.2).

Posted
Hi all.

It seems to me that my IAS, and M/TAS instruments are lying to me. I was flying few times now to test it around 1 Mach and every airspeed indication seems to be off.

I was testing it at ISA conditions down low where 1 Mach should correspond to 1225km/h.

At IAS and TAS 1225km/h (few km/h deviation) machmetr was already showing 1,04M, but I was still not supersonic. Not to the point of IAS and TAS of about 1275km/h (few km/h deviation) at that point machmeter was at 1,05M and I was just barely supersonic.

It seems all airspeed instruments are showing more than they should.

Machmeter about +0,05M, IAS/TAS about +50km/h.

 

Any MiG-21 driver show the same, or is it just me? I cant recall exactly, but I think this was not happening before latest patch.

 

When you post ISA down low, What atmospheric conditions in DCS and what altitude from sea level where you flying?

To whom it may concern,

I am an idiot, unfortunately for the world, I have a internet connection and a fondness for beer....apologies for that.

Thank you for you patience.

 

 

Many people don't want the truth, they want constant reassurance that whatever misconception/fallacies they believe in are true..

Posted (edited)

Alt. 15m ASL, temperature +15°C, pressure 760mmHg no wind, no clouds, no turbulence.

 

I know there is some air compresibility issue around 0.85 to 1M, but I also know that machmeters should not be affected much by it. I red that max. deviation should be around +-0.01M, unless there is blockage of course.

 

It was not behaving like that in previous versions as far as I can remember, that is why it seem off to me now.

 

Edit: I just installed FC3 and tested it with Su-27. Under same conditions machmeter was showing exactly Mach 1 and airspeed of 1225km/h (+ few km/h) as I was just supersonic. Maybe FC3 aircraft are too simplistic to work with instrument, pressure, tempreature errors. But it seems way off for MiG-21.

Edited by Golo
Posted

You could be onto a bug, The pitot tube is in front of the aircraft for a reason (so that it is not affected by airflow from the air frame). Mach 1 should be showing Mach 1 on the instrument (with small percentage of error of course, but not a lot) and if you see high error, I would say this is a bug.

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Posted

Yes, but the static port is not on the pitot tube.

And I'm sure it does effect the IAS, in fact it's the different between these two pressure (pitot,static) to determinate the IAS.

Saying that at transonic speed the static sport goes in trouble all the related instrument will be effected, IAS,Altimeter,VSI and who knows whatelse....

Posted (edited)

There's a RL MiG-21 chart to correct for the indicated pressure altimeter reading lower than the actual one at low altitudes and high indicated airspeeds (at M<1) but I haven't found a IAS -> CAS chart.

 

To maintain the required pressure altitude (Hg), it is necessary to allow for the total (i.e. position and shock-wave) error of the pitot-static tube (Delta Hposn, sh/w).

 

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MiG-21_IAS-AltitudeCorrection.thumb.JPG.a2b01483f19e7848071e14c0428ccab5.JPG

Edited by Ramsay

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