QFF calculation....

[lc_aerobatics]

Hi,:8
I'm still having some problems calculation QFF and it's relation to QNH for ATPL met questions. :ugh::ugh::ugh:

Does any one have a good methoth how to memorize and calculate all pressure and temerature variations for ATPL MET ???:rolleyes:

Thank you very much !!!
LC

[clanger32]

For Met, the only type questions with relation to QFF will be along the lines of QNH is 1020, you're 200 ft above MSL and it's an ISA +10 atmos. What is QFF? (or indeed they could reverse and give you QFF and ask QNH) where the answers will be something like:
A) More than 1020
B) Less than 1020
C) The same as QNH
D) Unable to tell

The way we were taught to remember it, is just to consider the height AMSL and the ISA Temp. If you assign a "sign" to the values (+ or - depending on whether it's over or under MSL or over or under ISA) then two positives or two negatives and QNH > QFF but if you have one + and one - (doesn't matter which way around), then QFF > QNH

So, in other words

If Height is ABOVE MSL(+) and Temp is > ISA (+) then QNH > QFF
If height is BELOW MSL(-) and Temp is < ISA (-) then QNH > QFF
If Height is ABOVE MSL(+) and Temp is < ISA (-) then QFF > QNH
If Height is BELOW MSL(-) and Temp is > ISA (+) then QFF > QNH

So using this, for my example above, the answer would be B, as both height AMSL and ISA temp are +ves, making QNH > QFF

Hope that helps.

[David Horn]

Similar to clanger32, I was taught to simply look at the signs for whether the elevation of the airfield is higher or lower than MSL, and what the ISA deviation is.

SAME SIGNS: QNH higher
DIFFERENT SIGNS: QNH lower

[lc_aerobatics]

thanks guys !!!!

Back to books and questions.....

What a great weekend:E