Here is a question perhaps more for our northern friends (Southern France is more unlikely being concerned when not flying every day as a pro):
As pilots, do you apply temperature corrections to DA/DH MDA/MDH altitudes in temperatures below 0°C? Is it needed for FAF crossing? What about MSAs?
The approach chart will usually contain a remark that below -15C the numbers given will not be valid. To my understand that’s when you need to correct.
I saw that on (Baro-VNAV) GNSS approaches. It is said that below -20°C (GNSS 14L/14R at LFBO) you are not authorized to use the approach. The more often is a 15°C limit as you pointed out. That seems very clear as with other type of approaches, there could be a correction factor.
Flyamax wrote:
Here is a question perhaps more for our northern friends (Southern France is more unlikely being concerned when not flying every day as a pro):Yes, absolutely.As pilots, do you apply temperature corrections to DA/DH MDA/MDH altitudes in temperatures below 0°C?
Is it needed for FAF crossing? What about MSAs?
Yes. To take an example… Suppose the temperature on the ground is -10°, the FAF altitude is 1500 ft and the temperature at 1500 ft is -5° (there is usually an inversion when ground temperatures are that low). On the average, that is ISA-21°. Then the altimeter will read about 125 ft low. That’s 1/4 of the minimum obstacle clearance at the FAF…
Not to mention that ILS check altitudes won’t match unless you correct for temperature.
Here is a comprehensive article on this.
Airborne_Again wrote:
Then the altimeter will read about 125 ft low.I mean high, of course….
There is a free App for iPhone and iPad which can easily calculate the altimeter corrections (and decode MOTNE codes which is more useful to me) called “ColdAirOps”. Luckily I rarely encounter temperatures where that really matters.
