About the altimeter setting

[Genghis the Engineer]

Frankly, anybody who can't handle changing from QNH to QFE and back again during a MATZ transit, or just the once when arriving at an airfield, probably lacks the mental capacity to be safe in charge of an aeroplane. Ditto in a QNH only environment mentally subtracting airfield elevation from the altimeter reading.

Frankly, I don't get the fuss. Using QFE is easy. Not using QFE is easy. Switching between systems is easy.

G

[phiggsbroadband]

Don't tell those Colonials about 'Regional Pressure Settings', lets leave that as a surprise 'Gotcha' for all them intrepid foreign airmen.

[Discorde]

it can get a bit more complex when flying through a MATZ and they give you QFE to fly on

Add field elevation to the height you're cleared at, round up or down to the nearest 100 ft, no need to reset your altimeter. Bonus: you'll eliminate the risk of forgetting to reset after MATZ transit.

[Maoraigh1]

I get Inverness QNH on taxi. I get Orkney and Portree QNH on leaving frequency. Lossie give me Lossie QFE though I'm not entering their MATZ. On return I get Inverness QFE. No problem in practice. I just set whatever the ATC I'm working tells me to.
But the OP had an exam question: What is the Altimeter Setting, and "Whatever ATC tell you to use" wasn't an option.

[2 sheds]

Orkney and Portree QNH

RPS - not QNH !

[chevvron]

Originally Posted by Maoraigh1

I get Inverness QNH on taxi. I get Orkney and Portree QNH on leaving frequency. Lossie give me Lossie QFE though I'm not entering their MATZ. On return I get Inverness QFE. No problem in practice. I just set whatever the ATC I'm working tells me to.
But the OP had an exam question: What is the Altimeter Setting, and "Whatever ATC tell you to use" wasn't an option.

Do Inverness actually offer you the QFE or do you ask for it?
CAA policy is that the 'normal' setting to be used is actual airfield QNH with QFE available 'on request'.

[phiggsbroadband]

Hi Chevron... To be pedantic... You are a bit ambiguous with ''actual airfield QNH''.


You could have an ''actual airfield QFE''. But an airfield does not have a QNH, unless the runway is a beach at the high water mark.

[Genghis the Engineer]

I had an airprox once after flying a microlight off a beach. I filed, as it scared me, and was definitely not my fault.

I put my altitude down as xxxft QNH. The Airprox board phoned me and asked what QNH setting I was using and where I obtained it from.

I explained that I'd set it to read zero on the beach, halfway between the high and low tide marks. The airprox board inspector had clearly never had that answer before, and it confused him!

G

[2 sheds]

chevvron wrote:

CAA policy is that the 'normal' setting to be used is actual airfield QNH with QFE available 'on request'.

Not quite correct - MATS Pt 1 specifies:

when requested by the pilot, or local procedures require, the appropriate QFE shall be given.

2 s

[Above The Clouds]

Slightly off topic

I had an airprox once after flying a microlight off a beach. I filed, as it scared me, and was definitely not my fault.

I put my altitude down as xxxft QNH. The Airprox board phoned me and asked what QNH setting I was using and where I obtained it from.

I explained that I'd set it to read zero on the beach, halfway between the high and low tide marks. The airprox board inspector had clearly never had that answer before, and it confused him!

G

Had a similar incident from an airprox filed against me many years ago, in essence the inspector Group Capt such and such was trying to plant the blame firmly on me for exceeding 250 kts IAS below 10000' outside controlled airspace.

He stated that from radar recordings clearly my TAS was approaching 300 kts which is a breech of ANO.......oh really I replied !!!! that airprox was filed under B.

[Genghis the Engineer]

I don't think that controllers know much about aircraft performance.

Apparently a couple of years I climbed into class A at 4500ft without permission, in a near MTOW AA5 doing 140TAS crosswind at a climb rate of just below 600fpm. Oh, really, I said !

G

[FullWings]

You could have an ''actual airfield QFE''. But an airfield does not have a QNH, unless the runway is a beach at the high water mark.

Well, in some ways it does. If the airfield elevation differs significantly from sea level, the “airfield QNH” could likewise be significantly different from the sea level pressure.

The QNH given to you by an airfield will result in a pressure altimeter reading the airfield elevation when you are on it. If you use a QNH derived elsewhere and the atmosphere is non-standard, which it is pretty much all of the time, there will be an error on your altimeter, maybe significant and possibly dangerous...

[JW411]

Which raises the subject of the seldom used QFF.

QNH will give airfield elevation using a standard atmosphere.
QFF will give airfield elevation using the existing atmosphere.

[2 sheds]

Which raises the subject of the seldom used QFF.

No, it doesn't! When have you ever heard QFF passed by ATC? That's for met charts.

QNH will give aerodrome elevation (at the highest point on the landing area - plus an allowance for instrument height if you want to be picky) in the existing conditions - that's the whole point.

2 s

[fireflybob]

QNH is atmospheric pressure at aerodrome level reduced to sea level assuming an ISA temp lapse rate (1.98 deg C per 1,000ft)

QFF is atmospheric pressure at aerodrome level reduced to sea level assuming isothermal conditions (i.e. constant temp). Isobars are lines joining places of equal QFF.

[Talkdownman]

Originally Posted by Genghis the Engineer

I don't think that controllers know much about aircraft performance.

Sir, with respect, I don't think that you know much about the knowledge of controllers

[Genghis the Engineer]

Originally Posted by Talkdownman

Sir, with respect, I don't think that you know much about the knowledge of controllers

Possibly - but I've certainly had several experiences where I had to explain in some detail the nature of an issue to controllers who did not get what to me was intuitive.

For example, that the generator failure I'd just suffered would not cause a subsequent engine failure (but that I might need a radio failure procedure to fall back on), or that nobody will do 140kts TAS crosswind whilst climbing at 600fpm at 5000ft in pretty much any standard single.

I have discussed this when being a volunteer pilot on a TRUCE course, and it re-inforced my opinions. Not that I would blame the controllers as much as I would their employers for not providing better training opportunities.

G

[JW411]

2 Sheds:

I absolutely agree that QFF is usually what is used for plotting on met charts however, on a few occasions during my flying career, I have been given the QFF "because QNH is not available". If I remember correctly, we are talking Middle East and Indian Subcontinent and certainly not "mainstream airfields". However, it was useful to know what QFF actually meant!