History of the Flight
The accident flight was the first flight after installation of new avionics and an autopilot. The purpose was to test the equipment and for the owner to familiarize with their use. On board were the owner, an electronics technician who had participated in the work, and a pilot-instructor who had previously performed a check flight on this type. The flight program included takeoff from Bâle-Mulhouse under VFR, an RNP approach to runway 15 (rejected), and an ILS approach to runway 33. The pilot took off at 15:17 from runway 15. After about 15 minutes, between waypoint ALTIK and the final for runway 15, the pilot observed an ammeter charge indication close to 70 A, much higher than the expected 10–30 A. He cut the alternator (Master ALT switch) and the ammeter dropped to zero; when he switched it back on, the ammeter again indicated around 70 A. The occupants presumed a discharged battery and continued. The pilot flew a missed approach at about 3,000 ft and began the ILS approach for runway 33. While climbing to 7,000 ft, the pilot and passengers perceived an electrical smell. Suspecting an incipient fire, the pilot decided on an emergency landing on runway 33, informing the controller. Shortly after, smoke from the luggage hold and flames spread into the cabin. The pilot started a quick descent and isolated the battery and alternator by setting Master BAT and Master ALT switches to OFF. He landed on runway 33. While the aeroplane was still rolling at an estimated 30–40 kt, the three occupants evacuated. The owner in the front right seat was the first to evacuate; he was fatally injured on hitting the runway. The rear passenger was severely burnt.
Aircraft Information
The aeroplane was a Piper PA-28RT-201T Arrow IV, manufactured in 1981, registration HB-PNP. It had 5,386 flight hours and 5,560 cycles. Its airworthiness review certificate issued on 3 October 2019 was valid. It was equipped with a hand-held halon fire extinguisher under the front right seat. Several Supplemental Type Certificates (STCs) were installed: a battery STC (Concorde RG-35AXC) in October 2017, a cable STC (Bogert Aviation) between battery and starter in November 2019, and a Garmin avionics STC (Garmin G5 EFIS and GFC500 autopilot) installed from 19 June to 16 July 2020. Avionics work was done by AVIONITEC; mechanical work by FLUGSCHULE BASEL. An electrical power consumption test on 16 July 2020 showed total consumption less than 60 A (85% of alternator capacity). The Garmin STC did not require a flight test before return to service. The Approval for Return to Service was issued by the electronics technician who was the rear passenger. The day before the accident, the battery was removed and fully charged, and ground tests were performed with the engine running on a GPU.
Technical Examinations
Visual examination of the wreckage determined that the source of the fire was in the compartment behind the luggage hold, which contains the ventilation system, hydraulic pump for landing gear, battery, and numerous general electrical system components. Damage to the ventilation system and hydraulic pump did not indicate prior damage. Work concentrated on the electrical power system. In coordination with the NTSB, Piper and equipment manufacturers were consulted.
Conclusions
No probable cause was stated in the available source.