Accident Overview
On 6 July 1990, at approximately 1047 local time, a Cessna F-152 (registration HB-CFV) and a Piper PA-32R-301 Saratoga (registration HB-PES) collided in midair near Birrfeld airfield. The Cessna had just completed a check flight and was on final approach to runway 26. The Piper was conducting full-load circuits (transition training) with a pilot, an instructor, and three passengers. The collision occurred when the Piper, flying faster and slightly higher, struck the Cessna from behind, with its propeller partially severing the Cessna's tail. The Cessna entered a spiral dive and crashed approximately 400 meters from the runway threshold. Both occupants of the Cessna—a student pilot and an examiner—were killed. The Piper sustained damage but all five occupants were uninjured; the pilot executed a go-around, flew a short circuit, and landed on runway 26. Minor ground damage occurred.
Flight History
The Cessna HB-CFV departed from Birrfeld for a private pilot examination. After the test, it returned and entered the right downwind leg for runway 26 via the entry point 'N'. Meanwhile, the Piper HB-PES had been performing circuits. On its final circuit, the Piper took off, entered the downwind, and then turned base and final. Both aircraft were on final approach to runway 26, with the Piper initially behind and above the Cessna. The Piper, faster, closed on the Cessna. A ground observer noted the closing speed but could not issue a warning due to an unset radio. The collision occurred before any evasive action could be taken.
Aircraft and Crews
The Cessna F-152 was occupied by a student pilot and an examiner from the Motorfluggruppe Zürich. The Piper PA-32R-301 Saratoga was flown by a pilot receiving type instruction from an instructor; three passengers were in the cabin. The instructor had limited experience on the Piper Saratoga (1 hour 49 minutes total). Both aircraft had restricted outward visibility, especially the Piper.
Communications and Circuit System
Radio communications were minimal. The Cessna reported over point 'N' inbound, but no further position reports were made. The Piper crew did not hear any later calls. The airfield had no positive control; only AFIS (Aerodrome Flight Information Service) was in place. The circuit pattern at Birrfeld was considered inadequate for separating slow and fast aircraft.
Cause and Contributing Factors
The collision was attributed to insufficient airspace surveillance, particularly by the crew of the Piper HB-PES. Contributing factors included lack of traffic information between the aircraft, an inappropriate and tight circuit system, restricted external visibility from both aircraft (especially the Piper), the instructor's limited experience on the Piper Saratoga, and the absence of position radio calls by pilots of both aircraft.
Recommendations
The investigation recommended reviewing the circuit system at Birrfeld to separate slower and faster aircraft, and enforcing AFIS regulations strictly, possibly considering positive ground control.