Hornet altimeter setting

Hello.

For as long as I've had the Hornet now (shortly since its launch) I've noticed an apparent bug that I don't believe I've seen anyone report yet:

The altimeter setting is incorrect for a given altitude.

And example: our server's mission has a QNH of 29.78. As we know, by setting QNH on an altimeter said altimeter should show the current altitude above sea level. My aircraft is parked on Krasnodar Center with the field elevation of 98ft. By setting 29.78 I get the altitude of 420ft. To get the correct altitude of roughly 100ft I need to drop the altimeter pressure setting down to around 29.43.

Is there an explanation for this behaviour or is it indeed a bug?

Regards,

MikeMikeJuliet

Hello.

 

For as long as I've had the Hornet now (shortly since its launch) I've noticed an apparent bug that I don't believe I've seen anyone report yet:

 

 

The altimeter setting is incorrect for a given altitude.

 

And example: our server's mission has a QNH of 29.78. As we know, by setting QNH on an altimeter said altimeter should show the current altitude above sea level. My aircraft is parked on Krasnodar Center with the field elevation of 98ft. By setting 29.78 I get the altitude of 420ft. To get the correct altitude of roughly 100ft I need to drop the altimeter pressure setting down to around 29.43.

 

 

Is there an explanation for this behaviour or is it indeed a bug?

 

 

 

Regards,

MikeMikeJuliet

I did a quick test on a runway at alt. of 43 feet ASL. At first, I didn't change any settings and the altitude displayed on the HUD was 50. After moving the setting up a notch then bringing it back to 29.92 the HUD was showing 40 (good enough for me) I guess I woke it up!

On the next test I changed the pressure in ME to 30.24 When I got in the cockpit The HUD showed -250 (that's about right) at 29.92 setting. I changed it to current 30.24 and the HUD alt. went up to 40. So... I guess it worked correct. I'll play with it more later.

I did a quick test on a runway at alt. of 43 feet ASL. At first, I didn't change any settings and the altitude displayed on the HUD was 50. After moving the setting up a notch then bringing it back to 29.92 the HUD was showing 40 (good enough for me) I guess I woke it up!

 

On the next test I changed the pressure in ME to 30.24 When I got in the cockpit The HUD showed -250 (that's about right) at 29.92 setting. I changed it to current 30.24 and the HUD alt. went up to 40. So... I guess it worked correct. I'll play with it more later.

Interesting. I do have a feeling I have not seen this constantly. I have to do additional testing on this as well.

Assuming it's static weather (if it's dynamic weather then briefing means exactly nothing) then "QNH" value is really QFF which is QNH for a sea level station.

The mapping of pressures to altitudes can have both a pressure shift (pressure anomaly) and a scaling compression (temperature anomaly). In non-standard temperatures it is impossible for altimeter to be calibrated to read correct at more than a single altitude. Away from this altitude the compression causes a proportional error (larger error the more unusual the temperature and more distance from the calibrated elevation).

So QNH is only valid for a certain elevation at a certain location. The setting which will makes the altimeter read Beslan's elevation at Beslan is not the same that makes altimeter read Batumi's elevation at Batumi.

What QNH does not guarantee is that the altimeter will read the true altitude anywhere except at the airfield elevation which that particular QNH is defined.