Arctic Airmass Issues
- Ryan Retelle
The freezing temperatures that are sweeping across the Northern parts of the country have captured the attention of the nightly news. The sub-zero temperatures are causing many to rethink how and what can be accomplished outdoors. Some may be fortunate to travel South to warmer locations while others are dealing with the effects of dead car batteries and frozen door locks.
For those flight crews who are operating in these artic temperatures, the theory of cold temperature altimetry errors has become a reality. Have you been assigned a trip to a location that is listed within the Notice to Airmen Publication (NTAP) Cold Temperature Restricted Airport chart? Do you remember from your recurrent training how and where to apply the correction?
During your preflight preparation, take the time to review the briefing strip of your destination and alternate instrument approach charts. There may be two different notes at each airport. One note requires compensation when the airport temperature is at or below the listed value. The second note addresses conflicts with terrain for non-precision approaches; "For uncompensated Baro-VAV systems, LNAV/VNAV not authorized below -15°C".
Your preflight prep has identified that your destination airport has a required cold temperature correction value of -10°C and the current METAR is showing a temperature of M12. Does your FMS system have a Temp Comp feature? When should it be activated? May Temp Comp be activated while still navigating on the STAR? What if you have to manually calculate the altitude correction?
Pro tip: It is best to figure out these details with a warm cup of coffee in hand prior to departing. For an overview, review FAA Information for Operators [InFO] 07014.
These cold weather operations topics are addressed in Advanced Aircrew Academy's Winter Operations eLearning module.