What happened
On 28 March 2008, a DC-8-63F cargo aircraft, registration N865F, departed Shannon Airport (EINN) bound for Qatar. During the initial climb phase, the aircraft encountered a series of compressor stalls in the number one engine. The flight crew responded by shutting down the affected engine. However, shortly after this shutdown, a second compressor stall occurred on the number two engine.
Facing an emergency, the crew declared an emergency and requested an immediate return to Shannon. To maintain necessary airspeed during the developing situation, the aircraft entered a descent, dropping from 2,400 feet to 1,100 feet. During this period, residents in the nearby village of Aske/keaton reported hearing loud bangs and seeing flames. After the crew activated the engine anti-ice system, the engines stabilized, and the number one engine was successfully restarted. The aircraft eventually landed safely on runway 24 after a 14-minute flight.
The investigation
The AAIU examined the aircraft's performance, the weather conditions, and the engine mechanics. At the time of the incident, the aircraft was operating at a heavy weight. While the ambient temperature was 6°C, the area was experiencing strong convection and heavy showers, which can create conditions for engine icing even when external airframe ice is not visible.
Investigators reviewed ATC radar data, which showed the aircraft's rapid descent and the activation of the Minimum Safe Altitude Warning (MSAW) system. The investigation also focused on the technical characteristics of the Pratt & Whitney JT3D engines, specifically how ice accumulation on the inlet probes or vanes can distort airflow and trigger compressor stalls.