Nevada Altimeter Settings

[Frederf]

Even forces which use QFE normally have procedures in place when the equipment can't be set normally due to the airport elevation. Most revert to QNH operations. L-39/MiG-21 altimeter can calibrate off the bottom of the scale using the triangle indices.

 

Approaching an airfield with reported QFE unusable and QNH unknown is not a realistic situation for a pilot to find himself in. There is no way to get a very accurate QNH setting only knowing QFE and field elevation. Accuracy is less but perhaps acceptable if you assumed standard atmosphere (need a chart) and even less if you applied a standard pressure gradient rule of thumb.

 

QNH known (e.g. static weather DCS briefing) then simply input this value into the altimeter and fly the altitudes as appropriate. Yes, if the desired traffic pattern is 1,500' AAL and the airport elevation is 3,456' you would have to do the math as a pilot to prepare for a 4,956' TPA. This also applies to manual bombing profile heights. This type of head math is expected of pilots.

 

As for unit conversions that's desk work to anticipate conversions of expected values if your instruments differ from what the controller gives. You'd have charts at hand to convert quickly and accurately from mmHg to inHg or bar or whatever as well as meters/feet. Operating routinely where instruments mismatch units of controller is uncommon.

[Piroflip]

Got it!

 

Thanks Frederf. I'll work w/ QNH and go from there. Lord knows I need to practice my math...:smartass: