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IFR Fix: The air down thereIFR Fix: The air down there

The instrument flight to Berlin, New Hampshire, for some late-winter fun in the White Mountains is on for March 4, and your flight planning is gathering steam.

The planning has a new wrinkle during the first winter of mandatory procedures in effect at cold temperature restricted airports (CTRA). Studying the airport’s instrument approach procedures, you note that Berlin Municipal is a CTRA; the required procedures take effect when the surface temperature is colder than minus-8 degrees Fahrenheit, or minus-22 degrees Celsius.

The latest edition of the Notices to Airmen Publication will tell you which approach segments require calculating and applying an altitude correction to fly above your indicated altitude for safe obstacle clearance. In Berlin, intermediate and final approach segments require this correction, according to the Feb. 4, 2016, edition of the publication.

What’s the likelihood of CTRA operations being in effect?

You’ll check the weather before and during flight, of course, with new emphasis on the surface temperature—a METAR element that previously served mainly to check the temperature-dew point spread, and in warm weather, to calculate density altitude.

Now, however, look over temperature statistics for CTRAs to get a general idea of the likelihood of needing to follow the mandatory procedure for arrival.

On the day of your planned arrival, Berlin, in northern New Hampshire, typically is chilly, with temperatures between 12 and 35 degrees Fahrenheit, according to one source of weather information.

On that date in 1938, the temperature reached minus-29 degrees Fahrenheit—the lowest March temperature ever recorded in Berlin. In 1964, it was 63 degrees Fahrenheit outside. They’re probably still talking about that day, but no one cares to recall Dec. 30, 1933, when the high fell to minus-41 degrees Fahrenheit.

What emerges from the review is that from November through March, temperatures colder than minus-8 degrees Fahrenheit have been recorded, meaning CTRA operations will likely be in effect.

Work out the applicable correction when within range of your destination, based on the latest reported surface temperature, and before your approach workload starts to build.

Such early preparation would be even more important for an approach to a CTRA of a different type: At Colorado’s Eagle County Regional Airport, for example, when temperatures reach minus-25 degrees Celsius or minus-13 degrees Fahrenheit, an altitude correction applies only on the missed approach—when fumbling for a cold temperature error table while flying a complex transition in mountainous terrain is the last thing you’d want to be doing.

Dan Namowitz

Dan Namowitz

Aviation Writer
Dan Namowitz is an aviation writer and flight instructor.
Topics: Instrument Rating, IFR, Weather

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