QFE on altimeter doesn't match

[RICARDO]

hello,

i notice that when you call the ATC on ILS landing, QFE units on altimeter doesn't match what ATC gives you on radio.

How could i convert that?

thanks

[grunf]

hello,

i notice that when you call the ATC on ILS landing, QFE units on altimeter doesn't match what ATC gives you on radio.

How could i convert that?

thanks

The altimeter pressure is shown in millibars, the QFE is given in inHg. To convert it to millibars, multiply the given number by 33.8639 :D.

[Dingo_Bob]

The Mirage uses millibars, you can get it by multiplying the QFE (inHG) by 33.8637526

 

Thanks Azrayen,

I stand corrected :D very rusty at the old theory I knew as I was typing it it didn't sound right

over 25 years since I actually used it in practice :D

 

this site is quite handy too

http://www.hochwarth.com/misc/AviationCalculator.html

 

 

:D Sniped

Edited March 7, 2016 by Dingo_Bob

[Azrayen]

The Mirage uses QNH (mmHG), you can get it by multiplying the QFE (inHG) by 33.8637526

Ouch, huge confusion here. The Mirage does not use mmHG but hPa, and you can set any altimeter to either QNH or QFE.

 

QFE and QNH are two different things.

- QFE is set so that when on the ground at the terrain/airbase, altimeter shows 0

- QNH is set so that when on the ground at the terrain/airbase, altimeter shows the altitude of terrain relative to MSL (mean sea level).

 

Both QFE and QNH can use different units:

- hPa (standart in France/Europe)

- inHg (standart in North America)

- mmHg (standart in Russia / CIS)

 

The "STD" (standard) pressure used for all aircraft above transition level (so that wherever you come from / go to you can have the same setting as the next aircraft flying past you, or as the ATC of the country you're overflying) is :

1013(.25) hPa

29.92 inHg

760 mmHg

[gospadin]

Note that QFE essentially cannot be used in Nevada (and it's very uncommon in the USA anyway) because most altimeters cannot be adjusted enough to read zero when on the ground. Need ATC 2.0 to fix this.

 

QNH plus available charts is what most pilots use here.

[RICARDO]

Merci Azrayen,

très clair tres précis as usual ;-)