What happened
On October 11, 1973, a Cessna U 206 A, registration HB-CBU, departed from Locarno Airport for a series of skydiving flights. The aircraft was carrying a pilot and five passengers, including a skydiving instructor and four students. Shortly after takeoff from runway 26, while the aircraft was performing a climbing turn over Lake Lungo, the engine power dropped and the engine failed. The pilot noted that the fuel pressure had fallen to zero.
In an attempt to manage the emergency, the pilot performed an emergency landing on the water. As the aircraft approached the surface, the pilot pulled back on the elevator to maintain a landing configuration. However, the aircraft struck the water nose-first with a right-wing dip. All occupants managed to exit the aircraft through the rear right door. While a nearby fisherman was able to rescue the pilot and four passengers, one passenger, who had initially clung to the sinking wreckage, was unable to swim to safety and subsequently drowned.
The investigation
Investigators examined the wreckage recovered from a depth of 80 meters. The investigation revealed that the engine had failed due to fuel exhaustion. While the right fuel tank was full, the left tank contained only a minimal reserve. The wreckage showed significant damage, including a broken engine mount, a fractured right wing, and a bent fuselage.
Technical analysis of the fuel system showed that the fuel selector valve was set to the left tank. The investigation also reviewed the pilot's pre-flight procedures and the aircraft's recent maintenance history, noting that a recent inspection had required both tanks to be filled, which had altered the routine fuel management practices of the operator.