Pilot Loses Propeller MID-Air []

On 17 March 2017, Regional Express flight RXA768 was descending toward Sydney when the crew noticed abnormal indications from the right engine. The Saab 340B was still controllable, but the problem became progressively more serious as vibration increased. During the crew's engine-shutdown procedure, the entire right propeller separated from the aircraft. The crew declared PAN PAN, completed the shutdown and continued to Sydney on the remaining engine.

Accident Facts

The warning came before the propeller separation

The ATSB investigation found that the crew had several minutes of warning in the form of abnormal engine indications and increasing vibration. Flight-data and cockpit-voice recorder information confirmed that the crew identified the right-engine problem approximately ten minutes before the propeller shaft failed.

Rather than immediately abandoning the engine or making an unplanned maneuver, the crew worked through the relevant procedures. The ATSB specifically noted that the crew did not depart from the checklists, communicated effectively and considered their options, including the possibility of a go-around because of the weather.

A component failed inside the propeller gearbox

After the aircraft landed, investigators examined the remaining propeller-gearbox components. The propeller shaft had fractured between the main shaft and its flange. Laboratory examination found fatigue cracking that had initiated at a dowel-pin hole and propagated until the shaft could no longer transmit the required loads.

The investigation also found corrosion and fretting around the affected area. The crack had progressed far enough to produce a failure under torsional loading. This was not a case of a propeller simply detaching for an unexplained reason: the physical evidence identified a fatigue-fracture mechanism in the shaft.

The propeller itself was eventually located about 19 km, or 10 NM, southwest of Sydney Airport. Its recovery gave investigators the fractured hardware needed for a detailed examination.

The maintenance system became part of the investigation

The ATSB identified a safety issue beyond the failed component itself. The engine manufacturer's maintenance documentation did not contain a specific inspection procedure designed to detect fatigue cracking originating from the dowel-pin hole. The operator's inspection worksheet also did not provide the best opportunity to record inspection findings in the manner specified by the documented procedures.

Following the occurrence, the engine manufacturer issued service bulletins requiring inspection of the relevant propeller-gearbox shafts, and further safety actions were taken by the manufacturer and operator. The investigation also found that the crew's checklist management and crew resource management contributed to the positive outcome.

The documented finding

“The propeller shaft failed as a result of a fatigue crack that had initiated at the dowel pin hole.” — Australian Transport Safety Bureau

Conclusion

The most important feature of the event is the sequence from early warning to component separation. The crew had time to identify the abnormal engine condition, apply procedures and prepare for an abnormal outcome before the propeller actually departed the aircraft. Once the shaft failed, the crew isolated the affected engine and completed the flight to Sydney without further incident. The investigation then moved beyond the immediate hardware failure and examined whether inspection practices could have detected the developing fatigue crack earlier. That combination—crew response, physical evidence and maintenance-system review—explains why the event became a significant airworthiness investigation rather than simply a dramatic propeller-loss story.

Sources

• Video source (ATC/audio reconstruction)