Incident Overview
During a cruise descent from flight level 330 in clear air with a ram air temperature of -22 degrees Celsius, a double engine flameout occurred. Prior to the descent, engine power had been adjusted to 86 percent with engine anti-ice activated. When the throttles were advanced at flight level 220, there was no response from either engine.
Subsequent Test Flights
Successful engine relights were accomplished on later test flights using the same aircraft, registration N18FE. However, N18FE experienced repeated engine rollbacks at and above flight level 290 when the throttles were retarded to the flight idle stop. These engine rollbacks did not occur when flight manual idle restrictions—which are intended for speeds below 200 knots—were observed at speeds above 200 knots.
Operational Context
The aircraft was operating in clear air conditions, and the double engine flameout occurred without any prior indication of malfunction. The successful relights during test flights indicate that the engines could be restarted, but the rollback issue was consistently reproduced at high altitudes with the throttles at the flight idle stop.
Investigation Findings
The investigation noted that the engine rollbacks were absent when the idle restrictions specified for lower speeds were applied at higher speeds. The relationship between power settings, altitude, and airspeed was a focus of the examination. No further causal factors have been explicitly stated in the provided source.