European and U.S. regulators have expanded a software-upgrade mandate to CFM International Leap-1B engines that ensures Boeing 737 Max-powered aircraft will not experience engine-fan-speed issues caused by extremely cold weather.
The European Aviation Safety Agency and U.S. FAA mandates, issued Nov. 27 and Dec. 11, respectively, mirror earlier requirements that covered Leap-1A engines that power A320neos. The latest directives require 737 Max-family operators to upgrade full authority digital engine control (FADEC) and prognostic health monitoring (PHM) software within 60 days of their respective effective dates. The Boeing fleet upgrades were recommended in a CFM service bulletin issued Oct. 24.
The issue stems from engines cold-soaking after sitting idle for at least six hours in temperatures well below freezing. Frontier Airlines reported six incidents when Airbus A320neo-family aircraft departing on their first flights of the day 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 quickly developed the software modifications for the Airbus fleet. The issue has not turned up on any 737 Maxs.
“While we have not received any reports of aborted takeoffs with the CFM Leap-1B model engine, the unsafe condition is likely to exist because of similarities in design and instances of ice and moisture found in the pressure sense subsystem lines,” FAA said.