Accident Overview
On September 4, 1998, at approximately 11:30 local time, a Kaman K-1200 helicopter crashed near Hindelang, Germany. The helicopter was destroyed, and the pilot was fatally injured. No third-party damage occurred.
Flight Details
The helicopter was performing external load flights, transporting logs from a remote forest area on the Sonnenkopf at about 5,000 feet elevation to a loading site in the Retterschwangtal. The pilot had flown several successful sorties earlier that morning. During a hover pick-up, as ground workers attached a load of two logs, the pilot began to lift vertically. Suddenly, the engine sound changed, the load line went slack, and the pilot activated the warning siren. The helicopter then entered a steep descent and impacted the ground in a near-inverted attitude approximately 150 meters below the pick-up point, still attached to the external load.
Aircraft and Engine
The helicopter was a Kaman K-1200 (model K-1200). The accident was attributed to a sudden engine failure caused by the failure of both drive shafts of the redundant, dual-stage engine-driven fuel pump. Metallurgical examination revealed that the splined connections of both shafts had failed due to wear. This resulted in a complete loss of engine power during a stationary hover over terrain unsuitable for a successful autorotation landing.
Cause and Contributing Factors
The official investigation concluded that the accident was unavoidable after the engine failure occurred. Contributing factors included:
- The absence of a pressure monitoring system for the two pump segments, which would have allowed the pilot to detect a failure of one segment before it led to an engine malfunction. Such a system was installed in other helicopter models with the same engine but was not present in the Kaman K-1200.
- The pilot did not jettison the external load. It could not be determined whether this was unintentional or a deliberate attempt to avoid endangering ground personnel. While the accident was unavoidable after the power loss, the attached load significantly increased the severity of the impact.
The probable cause, as stated by the investigation, was a sudden engine failure after both drive shafts of the redundant dual-stage engine-driven fuel pump failed due to wear on two splined connections, making the accident unavoidable due to the helicopter's position in a stationary hover over terrain unsuitable for autorotation.