Leap Software Upgrade Mandate Addresses Cold-Soak Issue

Issue triggered by aircraft sitting overnight in extreme cold.

European and U.S. regulators are mandating software upgrades to CFM International Leap-1A engines that the manufacturer rolled out several months ago to address an issue linked to extreme cold-weather operations and experienced by one operator.

The European Aviation Safety Agency and U.S. FAA directives call for operators of CFM-powered Airbus A320neos to upgrade full authority digital engine control (FADEC) and prognostic health monitoring (PHM) software within 90 days. EASA's AD was issued Oct 8 following a normal public-comment period, while FAA will issue its directive Oct. 10, bypassing the customary draft notice-and-public-comment period.

The issue has been traced to engines cold-soaking by sitting idle for at least six hours in temperatures well below freezing. Frontier Airlines reported six incidents in which aircraft departing on their first flights of the day after sitting all night were forced to return to their gates when engines would not reach the required takeoff fan speed. In each case, water and ice was discovered in engine pressure-sensor lines, affecting the sensor's accuracy.

CFM publicly revealed the issue in January, and said it quickly developed a fix. In late July, it issued a service bulletin recommending all operators upgrade FADEC and PHM software to ensure the problem does not show up in their fleets. The FAA and EASA directives are based on the bulletin.

The six Frontier incidents are the only ones linked to the issue. Despite a lack of evidence of a fleet-wide problem, FAA fast-tracked its directive, skipping a public notice-and-comment period that likely would have added 6-12 months to the process. The move provides operators with a reasonable compliance window without pushing the deadline past the upcoming North American winter season. 

FAA says there are about 80 engines on U.S.-registered A320neos affected by its mandate.

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