Summary
The FAA proposes to adopt a new airworthiness directive (AD) for General Electric Company (GE) CF34-1A, -3A, -3A1, -3A2, -3B, and - 3B1 turbofan engines with high-pressure (HP) rotor 4-step air balance piston stationary seals (4-step seals), part numbers 4923T54G01, 6019T90G03, 6037T99G01, 6037T99G02, and 6037T99G03, installed. This proposed AD would require removing the 4-step seals and incorporating an 8-step seal at the next piece-part exposure. This proposed AD results from the investigation of an airplane accident. Both engines experienced high- altitude flameouts. Rotation of the HP rotors was not maintained during descent and the engines could not be restarted. We are proposing this AD to prevent the inability to restart both engines after flameout due to excessive friction of the 4-step seal, which could result in subsequent forced landing of the airplane.