When is cold temperature correction in effect

[bluehawaii]

Ladies and Gents, does anybody know at what cold temperature or condition does a pilot have to make cold temperature altitude corrections to his altitudes during the approach phase of flight into an airport.

[DBate]

Shouldn't that be stated in your company SOPs? Ours say that a cold temperature correction is to be applied at temperatures below 0°C.

Regards,
DBate

[bluehawaii]

Thanks DBate, I thought there was a reference temperature at which altitude correction factors become applicable in cold weather operations.

[Old Smokey]

If you want to be pedantic, Temperature Correction should be applied at any time that the SAT is below ISA, but the first few degrees make little difference (at least at the fairly low typical Approach Altitudes).

Like DBate, our company's SOPs also specify correction when the SAT is below 0 degrees. The resultant small errors would be well taken care of by the built-in margins considered when procedures are designed.

That's all very well for Normal All Engine Operations, where the margins are generous. When the margins are small (e.g. 35 feet Net clearance of an obstacle following Engine failure), I calculate the True Geometric Minimum Acceleration Altitude (3rd segment), and correct it for the lowest permissible temperature in the AFM approved Environmental Operating Envelope for the aircraft. This covers the worst case, but latter day EFB computed data uses the actuel temperature of the day, leading to some degree of variation in MAA provided on a 'per flight' basis (there are also other factors unassociated with temperature).

Regards,

Old Smokey

[Eff Oh]

As I understand it, it is applied whenever the temperature is below ISA -15.

[bluehawaii]

Thanks Old Smokey and Eff Oh.

[Dan Winterland]

Depends which table you use. the ICAO recommended one which is published in Jeppessen manuals and which in my experience most operators use is referenced to airfield temperature.

[3bars]

According to the Aerad supplimental grey book, corrections must be applied when airfield temperature is 0 degrees or below:eek:

[GlueBall]

Also good to know: ICAO Doc 4444: Aircraft on vectors will have cleared altitude temperature corrected.

If ever you fly in Siberia: consider corrections when ISA is -15c to -30c add 10% to MOCA/MORA; and when ISA is -31c to -50c add 20%

[Denti]

Heard these days a nice call from the relevant ATCO: Descend xxxx feet temperature corrected. Usually they don't tell you that they do but they usually do, at least from what i hear from my friends on the other side of that screen.

[bfisk]

For all practical purposes it works well with no correction for above freezing 10% down to -10C (airfield temperature). Colder than that, add a wee bit more if you don't expect weather close to minima, if you do, work it out with the charts or (or 0,4% pr degree in addition to 10% for -10).

And you certainly don't have to fly to siberia to see temps around -30. Ever been to Norway? :)