What happened
On June 17, 2005, a private VFR flight was being conducted from Krems-Gneixendorf (LOAG) to Wiener Neustadt Ost (LOAN). The pilot had originally intended to fly a different aircraft, a Cessna 182, but switched to the Cessna 172N after discovering a brake issue with the primary aircraft.
After completing standard pre-flight inspections and taxiing to runway 29, the pilot commenced the takeoff roll with 10 degrees of flaps. The aircraft accelerated normally and rotated near the center of the runway. During the climb, once the pilot began retracting the flaps, the engine began to sputter and run roughly. Despite immediate attempts to troubleshoot the engine by checking the power lever, mixture, fuel selector, and oil pressure, the engine suffered a complete loss of power.
After issuing a PAN PAN urgency message and making two unsuccessful attempts to restart the engine, the pilot was forced to perform an emergency landing due to the low altitude. The aircraft struck a field at the boundary of a corn and grain field. The impact caused the aircraft to capsize, coming to rest on its back with the wings and fuselage touching the ground. Both the pilot and the passenger sustained minor/no injuries and were able to exit the aircraft independently.
The investigation
Following the incident, the engine was removed from the aircraft and placed on a test stand for examination. Investigators attempted to start the engine on the stand, which initially failed. Upon inspecting the Bendix Dual Magnet ignition system, investigators opened the magneto housing to check the timing and ignition settings.
Findings
- The investigation established that the fastening screw for the distributor cam on the camshaft had loosened.
- This distributor cam is secured to the camshaft via a tapered connection using a screw, a retaining ring, and a washer to maintain a press fit.
- Due to inadequate thread-locking security, the screw had backed out, causing a loss of pressure on the tapered connection.
- As a result, the distributor cam was no longer rotating in unison with the camshaft, preventing the ignition contacts from opening properly and depriving the cylinders of necessary sparks.