1977 AS 202/15 Bravo Accident on Cavagnöö Glacier (HB-HEW)

Accident Overview and Aircraft Details On 30 May 1977, an AS 202/15 Bravo with registration HB-HEW, operated by Fliegerschule Birrfeld AG, made an emergency landing and overturned on the Cavagnöö Glacier in the canton of Ticino, Switzerland. The aircraft was rented by a pilot born in 1956, who held a private pilot license and had 48:14 total flight hours, including 35:14 on the accident type. The flight was a VFR private trip from Birrfeld to Ascona with the pilot's parents as passengers. ## Flight Sequence and Contributing Factors The aircraft departed Birrfeld at 1035 local time, fully fueled, with a planned latest return time of 1700. The route took the aircraft over Grimsel and the Nufenen Pass into the Bedretto Valley, then toward the Toggia Valley. The pilot intended to continue via Fiorina and Bavona to the Maggia Valley and Ascona. Over the Toggia reservoir, the pilot made a 360-degree turn to gain altitude. At approximately 2,750 m, the pilot entered the Fiorina Valley and began a descent. Upon seeing the Bavona Valley, the pilot observed cumulus clouds in the upper part, with a base around 2,000 m, thickening in the lower part. Judging a southern continuation too risky, the pilot climbed and turned northwest toward the Cavagnöö Glacier. The altitude was insufficient to return directly to the Bedretto Valley, forcing a turn. The stall warning horn sounded, and the pilot stopped the turn and pushed forward slightly. The pilot considered a turn under these conditions too risky due to the terrain and the need for a steep turn. ## Emergency Landing and Rescue Seconds later, the aircraft was only a few meters above the rising, snow-covered glacier. The pilot pulled the elevator control fully and performed a “sack landing” with the landing gear retracted. The aircraft first touched down on the main gear, overturned, and came to rest upside down. The pilot activated the emergency locator transmitter (ELT) and attempted radio contact on various frequencies without success. He climbed to the nearby Giacomohütte, which was locked. Returning to the aircraft, he removed the radio antenna to improve transmission, then removed the ELT and deployed its antenna, verifying its operation with the radio. The three occupants spent the night in the aircraft. A search launched by the Swiss Air Office the next morning was successful, and the occupants were evacuated by a military helicopter at approximately 0815. ## Investigation Findings and Probable Cause The pilot held a valid license and was authorized for the flight. No health issues relevant to the accident were known. The aircraft was airworthy, with weight and center of gravity within limits. The last 100-hour inspection was on 25 May 1977, and the last 50-hour inspection on 3 May 1977. The investigation found that the pilot deliberately began a descent when entering the Fiorina Valley before confirming that a continuation into the Maggia Valley was possible. The pilot's actions contradicted established aviation rules, which require adequate altitude and speed reserves in mountainous terrain to allow a safe turn at any time. When the stall warning horn sounded, it was correct to abort the turn and push forward, but the rising terrain and insufficient altitude made continued flight impossible. The pilot's limited flight experience contributed to the accident. The pilot's post-accident actions were described as prudent and effective. The probable cause was identified as incorrect flight tactics in mountainous terrain, with the pilot's limited experience as a contributing factor. The investigation recommended making the reporting of takeoff and landing mandatory for flights over the Alps to enable timely search operations.