Met question

So I think exmpa is saying c as well!

But it could well be d!

Bit difficult to answer without sight of any reference material included in the paper/script. Cannot really believe that even the JAA could want you to calculate an altimeter correction like that from memory and first principles.

exmpa

So I think exmpa is saying c as well!

A quick look at my last winter brief reveals the following:

There are two aspects of our operation that will need to be corrected for if temperatures fall below 0degC:

MDA/DA and approch height crossing altitudes
Acceleration altitudes

Note:

You will have to correct all MDAs for CAT1 and non precision approaches. DH for CAT2/3 do not need correcting.

But that doesn’t really help with your question, particularly as FLs are referred to, not altitudes, implying an en-route scenario. The only alt/temp correction reference I can find which might be applicable is to the Minimum Off Route Altitude (MORA), i.e. the figure shown in each grid square of the Radio Nav chart. There are tables for both wind and temps corrections:

When operating within 20 nm of terrain whose maximum elevation exceeds 2000 feet
a.m.s.l., commanders are to increase the standard MORA by the amounts given in
the following table, according to the wind speed over the route:

WindSpeed In Knots 0-30 31-50 51-70 More Than 70
Terrain Elevation
2000 – 8000 feet + 500 ft + 1000 ft + 1500 ft + 2000 ft
More than 8000ft + 1000 ft + 1500 ft + 2000 ft + 2500 ft

Temperature Correction
When the surface ambient temperature en route is well below the ISA value, MORAs
must additionally be corrected as follows:

Surface Temperature Correction to MORA
ISA -16oC to ISA -30oC MORA plus 10%
ISA -31oC to ISA -50oC MORA plus 20%
ISA -51oC or below MORA plus 25%

Hope that this helps and doesn’t just serve to confuse.

exmpa

Below FL295 (or above and in RVSM) I would say c as 2 degrees per thousand feet is almost exactly International Standard Atmosphere. At the surface you would be looking at doing an altimeter correction to a DA due to the low temperatures, I wonder if they are implying something similar occurs in the separation scenario?