Probe traces ATR terrain alert to wrong airport’s weather data

Canadian investigators have traced an unexpected ground-proximity warning on a domestically-operated ATR 42-300 to an altimeter setting error triggered by an incorrect weather-data transmission.

The First Air aircraft (C-GSRR) had been operating a service from Iqaluit to Pangnirtung on 9 December, according to Transportation Safety Board of Canada.

While en route at 19,000ft, and some 40nm north of Iqaluit, the crew obtained the most recent weather observation data for the destination from Quebec flight information centre.

But the centre inadvertently transmitted the data for Purvirnituq, some 880km to the south of Pangnirtung. The two airports have similar ICAO codes, respectively CYPX and CYXP.

Owing to the error, the crew had the wrong altimeter setting and, as the ATR descended to the destination, the pilots received a ground-proximity warning, says the safety board.

“Weather conditions permitted visual flight at the time, and there was no real risk of collision with the ground,” it adds.

It states that the crew subsequently obtained the correct altimeter information from a Unicom service, while about 20nm from the airport and descending through 2,200ft, and landed without further incident.