Microlight question - altitude 170 metres, QNH 1004 hPa, what is the QFE and how do you calculate it?

Question

My neighbour is studying for his exam and this is one of the questions on a past paper. Yes, I see my mistake, the height of the airfield is 170 metres

Answer 1

it sure is a guess barry. and a p**s poor one at that. did they finally rename this place yahoo guesses? the question is an excellent one and well constructed to someone with any knowledge at all of aviation. good job Z B. now the asker won't be even further confused by thinking altimeter settings have a d**n thing to do with brake horsepower. sheeesh.

Answer 2

QFE is the altimeter setting at which on the runway threshold, your altimeter will read 0. Without knowing the height of the aerodrome, you can not calculate the QFE.

Answer 3

The QFE is different from the presumed sea level pressure of 1004 hPa.

Expect a standard pressure difference of 100 hPa per 1000 meters.

(100 hPa: difference) = (1000m:170m).

(1 hPa/10 m)(170m) = difference.

17 hPa = difference.

The airport is above Mean Sea Level, so (at standard temperature for 170 m) the QFE will be 17 hPa less than 1004 hPa, or 987 hPa.

Answer 4

The engine manufacturers will tell you the rated BHP at sea level. They will also have data on power loss per metre of altitude. This answer is a guess as your question is a bit hard the way you have constructed it!