QNH VS QFE

[Remys 4]

in the landing phase we can choose between QNH and QFE

 

ok so QNH stands for barometric pressure as reported by a particular station (local altimeter setting)

and QFE Altimeter setting referenced to airport field elevation (where field elevation equals zero feet)

 

but when should i use QNH and when QFE and what does it depends on ?

normally which one is used and is it related to approach charts .... ?

 

thank you

 

[cva1077 68]

IIRC QFE is only used in Russia (possilby China?-can't remember) QNH is definatley more widely used. I would always use QNH unless given a specific QFE.

 

On the approach chart you will be given the approach minima for different categories of aircraft. These are in barometric altitude and radio altitude. The barometric ones are directly related to the current QNH. (unless in Russia/China? where it is related to QFE)

[Richard McDonald Woods 168]

QNH is the current barometric pressure and, if set in your aircraft, will ensure that the zero altitude on your instruments will coincide with the height of the runway. If the barometric pressure varies and you do not reset your instruments, you will be in danger of being above or below the field elevation. QNH is the setting used in commercial aviation.

 

QFE is field elevation and is the altitude above mean sea level of the runway. This value, therefore, does not vary with barometric pressure. QFE is normally only used by GA aircraft which mostly return to land at their departure airfield or fly VFR so that the height above the runway may be visually estimated.

 

HTH

[cva1077 68]

QNH is the current barometric pressure and, if set in your aircraft, will ensure that the zero altitude on your instruments will coincide with the height of the runway.

 

Richard, I think you may be a bit confused? When sitting at any airport with the QNH set, the altimeter read the aircrafts height above MSL. This is wht in places like Zurich, the approach minima are 1590 ft on the baro.

 

If you set the QFE, then the altimeter will read zero when on the ground.

[Flamin_Squirrel 71]

QNH is the current barometric pressure and, if set in your aircraft, will ensure that the zero altitude on your instruments will coincide with the height of the runway. If the barometric pressure varies and you do not reset your instruments, you will be in danger of being above or below the field elevation. QNH is the setting used in commercial aviation.

 

QFE is field elevation and is the altitude above mean sea level of the runway. This value, therefore, does not vary with barometric pressure. QFE is normally only used by GA aircraft which mostly return to land at their departure airfield or fly VFR so that the height above the runway may be visually estimated.

 

HTH

 

 

You might be thinking of QNE (1013hPa / 29.92inHg).

 

QNH and QFE both vary with barometric pressure, QNH gives altitude above msl, QFE gives hight above a certain point, such as runway threshold.

[hopskip 253]

QNH is the current barometric pressure and, if set in your aircraft, will ensure that the zero altitude on your instruments will coincide with the height of the runway. If the barometric pressure varies and you do not reset your instruments, you will be in danger of being above or below the field elevation. QNH is the setting used in commercial aviation.

 

QFE is field elevation and is the altitude above mean sea level of the runway. This value, therefore, does not vary with barometric pressure. QFE is normally only used by GA aircraft which mostly return to land at their departure airfield or fly VFR so that the height above the runway may be visually estimated.

 

HTH

 

These are both remenants of the "Q-Code"

 

QFE = "Qcode Field Elevation" (The Barometric pressure in mm that reads 0 at the runway elevation)

QNH = "Qcode Nautical Height"  (The Barometric pressure in mm that reads 0 at sea level) 

 

Standard QNH = QNE = The average (standard) barometric pressure at mean sea level in the International Standard Atmosphere. aka 1013.25

 

QNE is kinda backwards compared to the other 2.

QFE is an adjustment of the barometer to read 0 on the runway.

QNH is an adjustment of the barometer to read 0 at sea level, and

QNE is the altitude the barometer reports when the Kollsman window is set to 1013.25 Standard Average (which will change when the barometric pressure changes).

 

I guess technically, the 777 altimeter doesn't really have a Kollsman window, but same idea.

 

Back in the old old days, Morse Code was used for ATC (!) QFE1001 is easier to type than BAROMETRICALTIMETERSETTING1001 or even CODEFE1001. "Q" stood for "code". I'v heard it referenced as "Queens-Code" but back when it was invented, the reigning British monarch was a King, so probably not.

 

I guess Q sounded like Code and without the trailing U would be pretty obvious that one wasn't receiving a proper word in Morse.

 

 

Regardless if you get told to descend to 6000ft, QNH 1022, you just plug 1022 into the Kollsman window and head on down to 6000ft.

 

If you get told to descend to 600 metres on QFE 1031, you stick 2000ft into your MCP, Check the Metric window is near enough to 600m, dial up 1031 into the Kollsman window, and head on down.

[Capt Richardo 12]

Cva1077 is spot on, dont forget the TA & TL and the correct use of 1013 (FL)(2992). QFE is normally used on finals for 0 alt on landing ang for circuits

[Richard McDonald Woods 168]

Yes, apologies to all. This is what happens when rushing for a train. I should have given it more thought. :(