PPRuNe Forums - View Single Post - Descend below grid MORA?

19th Jul 2007, 16:27

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flyerline

Join Date: Dec 2005

Location: Switzerland

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Descend below grid MORA?

Hi

I have a question about the definition of grid MORA and the operational consequences at high temperatures and high QNH.
Is grid MORA defined by true altitude giving a terrain clearance of 1'000 ft <5'000 ft and a clearance of 2'000 ft >5'000 ft?

If so, is the following example a legal flight?
We fly off route with QNE 1013.25 hPa and want to know the lowest possible flight level, which ensures enough terrain clearance.
Let's say grid MORA is 18'300ft, temperature is ISA +20°C and QNH is 1018 hPa.

We calculate:
grid MORA 18'300ft
QNH correction -5x27ft = -135ft
temp. correction -8% of 18'300ft = -1464ft
Result: 16701 ft, so we could descend to mnm IFR FL 170.

Is this correct?

Thanks & Regards
flyerline

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