Reporting Of Air Pressure Change
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Reporting Of Air Pressure Change
If the ATIS reports both QNH and QFE, why do broadcasts of air pressure change by Approach and Tower only report the new QNH pressure?
I presume the QFE on the airfield has also changed, although maybe I'm wrong. Someone let me know.
I presume the QFE on the airfield has also changed, although maybe I'm wrong. Someone let me know.
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Dep Beck,
At Manch, we have QNH1009. QFE1000. For Rw24R we add 0.2mb, for 06L add 1.6mb and 06R 2.6 mb [ I think], and round DOWN.
So If the QFE is 1000.3, and we are landing 06R, then touchdown is 1000.3 plus 2.6 = 1002.9 which we round down
to 1002.
QNH is passed by Met in WHOLE numbers, QFE in increments
hope this helps
we aim to please, it keeps the cleaners happy
At Manch, we have QNH1009. QFE1000. For Rw24R we add 0.2mb, for 06L add 1.6mb and 06R 2.6 mb [ I think], and round DOWN.
So If the QFE is 1000.3, and we are landing 06R, then touchdown is 1000.3 plus 2.6 = 1002.9 which we round down to 1002.QNH is passed by Met in WHOLE numbers, QFE in increments
hope this helps
we aim to please, it keeps the cleaners happy
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Sorry, maybe I didn't make the question clear enough. What I meant to ask was why do I only ever here ATC advising crews of a new QNH reading, and never a new QFE reading. Crews use both measurements on their altimeters for different reasons, so why don't I ever hear a broadcast advising of a new QFE pressure?
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DB,
The QFE does not always change when the QNH does - all to do with rounding down to whole numbers. At Heathrow the elevation is 80ft AMSL, therefore the QFE is sometimes 2mb and sometimes 3mb lower than the QNH.
95% of commercial crews use the QNH nowadays, therefore airport elevation will show on the altimeter when the aircraft is at the airport. If a pilot requires the QFE then he will ask for it, but this is a very rare occurrence. Use of QFE is mainly confined to private aviation nowadays. The last bastion of the QFE was the military, but I believe that this has also changed. Perhaps Whipping Boy's SATCO can confirm.
The QFE does not always change when the QNH does - all to do with rounding down to whole numbers. At Heathrow the elevation is 80ft AMSL, therefore the QFE is sometimes 2mb and sometimes 3mb lower than the QNH.
95% of commercial crews use the QNH nowadays, therefore airport elevation will show on the altimeter when the aircraft is at the airport. If a pilot requires the QFE then he will ask for it, but this is a very rare occurrence. Use of QFE is mainly confined to private aviation nowadays. The last bastion of the QFE was the military, but I believe that this has also changed. Perhaps Whipping Boy's SATCO can confirm.
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Out of interest, where are the procedures for this written down?
At White Waltham (elev. 130'), we use the QNH from Heathrow (listen in to their ATIS from time to time to update it), and subtract 5mb from it to get a QFE. No issues with rounding - we couldn't round accurately anyway, since we only get the QNH to the nearest millibar. I'm wondering if there are any formal procedures anywhere, and if the procedures at a small GA field without ATC, such as White Waltham, would be less stringent than somewhere like Heathrow?
(And, as far as I recall, when there's a pressure change, the QNH and QFE are both broadcast... but, as ATCO Two says, most of the pilots at Waltham do use QFE when in the circuit, unlike LHR.)
FFF
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At White Waltham (elev. 130'), we use the QNH from Heathrow (listen in to their ATIS from time to time to update it), and subtract 5mb from it to get a QFE. No issues with rounding - we couldn't round accurately anyway, since we only get the QNH to the nearest millibar. I'm wondering if there are any formal procedures anywhere, and if the procedures at a small GA field without ATC, such as White Waltham, would be less stringent than somewhere like Heathrow?
(And, as far as I recall, when there's a pressure change, the QNH and QFE are both broadcast... but, as ATCO Two says, most of the pilots at Waltham do use QFE when in the circuit, unlike LHR.)
FFF
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ATCO 2
The Military use QNH IAW the procedural charts at civilian airports and have the choice of using QNH or QFE from the FAF. If the approach is to be flown entirely on QNH, ATC must be informed since it is assumed by ATC that QFE will be the landing datum. The aircraft will then be given the airfield landing threshold elevation.
At military airfields QFE is the landing datum for all RAF aircraft.
The inference that the military now use QNH is based on a trial some 10 years or so ago where the only pressure setting used was QNH. Unfortunately the fast pointy aircraft operators always liked to see 1000ft indicated in the circuit and 200ft at DH. They found the mental gymnastics a distraction for single seat and lobbied for the return to QFE, a mistake in my view.
The Military use QNH IAW the procedural charts at civilian airports and have the choice of using QNH or QFE from the FAF. If the approach is to be flown entirely on QNH, ATC must be informed since it is assumed by ATC that QFE will be the landing datum. The aircraft will then be given the airfield landing threshold elevation.
At military airfields QFE is the landing datum for all RAF aircraft.
The inference that the military now use QNH is based on a trial some 10 years or so ago where the only pressure setting used was QNH. Unfortunately the fast pointy aircraft operators always liked to see 1000ft indicated in the circuit and 200ft at DH. They found the mental gymnastics a distraction for single seat and lobbied for the return to QFE, a mistake in my view.
