Swiss Investigation of Reims Aviation F152 Accident at Buttwil (HB-CFF)

Incident Overview and Aircraft Details On 14 February 2013, a Reims Aviation F152, registration HB-CFF, was involved in an accident at Flugfeld Buttwil (LSZU) in Switzerland. The aircraft, a single-engine, two-seat, braced shoulder-wing metal construction with fixed landing gear and a steerable nose wheel, was manufactured by Reims-Aviation S.A. in 1981. It was powered by a Lycoming O-235-N2C engine producing 110 BHP (82 kW) and equipped with a two-blade fixed metal propeller. The aircraft's maximum takeoff mass was 758 kg, and its mass at the time of the accident was 672 kg, with both mass and center of gravity within the limits specified in the aircraft flight manual. The last 100-hour inspection was conducted on 11 December 2012 at 11,698 hours, and the last condition inspection by an organization commissioned by the Federal Office of Civil Aviation (BAZL) was performed on 28 March 2012 at 11,300 hours. No technical restrictions were recorded in the flight logbook or the owner's Journey Log / Tech Log. The approved fuel qualities were AVGAS 100LL, AVGAS 100, and MOGAS. After the accident, approximately 58 liters of fuel were measured in the wing tanks, corresponding to a fuel reserve of about 2 hours and 30 minutes. ## Pilot Background and Flight History The pilot was a student pilot, a Serbian national born in 1989, who did not hold a license or any significant ratings. He held a Joint Aviation Requirements (JAR) FCL3 Class 2 medical certificate, issued on 4 May 2011 and valid until 4 May 2016, with no restrictions. His total flight time was 48 hours and 53 minutes, all of which was on the accident aircraft type, with 11 hours and 24 minutes of that time logged in the preceding 90 days. The student began his practical training for the private pilot license at Buttwil airfield in early July 2011. On 31 January 2013, the flight school, Flugschule Eichenberger AG, confirmed in his logbook that he had completed his private pilot training and was ready for the practical skill test. The skill test had been postponed several times due to bad weather, with a new date set for 16 February 2013. Two days before the test, additional flight training was scheduled as preparation. ## Flight Sequence and Accident Description On the morning of 14 February 2013, the student arrived at Buttwil airfield at approximately 09:30 local time. He checked the latest weather reports and refueled the aircraft with 30 liters of MOGAS. The flight instructor and student did not meet that morning, and no further briefing of the flight program took place. The instructor issued a written flight order with the planned route listed as “Lokal” and then departed at 10:00 with another student for an Alpine orientation flight. The student had originally planned to conduct a solo navigation flight to Grenchen and back, but this was canceled by phone due to the weather. He then asked if he could perform solo landing training, which the instructor approved after checking the runway condition. The airfield was snow-covered, and the runway had been prepared to a width of 18.5 meters, corresponding to the distance between the runway markings, and was covered with compact and hard snow. The student had previously made several takeoffs and landings at Buttwil on snow-covered runways, including solo flights, and the instructor stated that he had discussed the specific runway conditions with the student during those flights. After completing his preparations, the student took his seat in the cockpit, started the aircraft according to the checklist, and taxied to the beginning of the runway. He reported that taxiing was “somewhat difficult but possible.” At 10:29, the Reims Aviation F152, HB-CFF, took off from runway 34 at Buttwil. The student trained for his upcoming test flight, practicing approaches with fully extended landing flaps as well as zero-flap approaches. He did not perform touch-and-go maneuvers but instead conducted either go-arounds or full-stop landings followed by taxiing back to the runway threshold. After the first takeoff, the aircraft flew a left traffic pattern, which was ended with a go-around. A right traffic pattern was then flown, also ended with a go-around. The third circuit was flown to the left, and the first full-stop landing was made at the end of this approach, followed by taxiing back. After the next takeoff, the student first flew a left circuit, ending it with a go-around. He then climbed via the right base leg to 4,700 feet AMSL and, from a position over the airfield, performed a no-engine-assist approach. This exercise was ended with a go-around and repeated once more. He then completed six additional traffic patterns, two to the right and four to the left. The twelfth approach was ended with the second full-stop landing, after which he taxied back to the runway threshold to take off again. After the subsequent takeoff, the aircraft followed the right traffic pattern and again approached runway 34. This thirteenth approach was made with engine power and retracted landing flaps. The student had planned to land, stop, and end his training. The aircraft touched down 170 meters beyond the displaced threshold of runway 34 on the centerline. After a short straight taxi in the runway direction, the HB-CFF gradually deviated from the runway centerline to the right. The student unsuccessfully attempted to counteract this movement using the rudder pedals and wheel brakes. Eventually, the right main landing gear entered deep snow at the runway edge. The aircraft was subsequently turned and strongly decelerated. Due to the braking effect in the deep snow, the aircraft tipped forward to the left, rolled over, and came to rest on its back to the right of runway 34. The student closed the fire shutoff valve and switched off the ignition. He stated that he also accidentally operated the flap switch, causing the landing flaps to extend. He then unbuckled his safety belt and exited the aircraft uninjured. The total time from the first takeoff to the accident was 1 hour and 17 minutes. ## Meteorological and Astronomical Conditions At the time of the accident, Switzerland was in a saddle position with high pressure in the northeast and southwest. A trough extended from Iceland to southern Italy, with an embedded warm front approaching the Alps from France. In the Mittelland, blocked cold air with an upper limit at 1,100 meters was present, and fog reduced long-range visibility. Above 1,200 meters, the relative humidity dropped to 10 percent, resulting in excellent visibility in the dry air. The near-surface wind field consisted of local and regional cold air outflow following the water network and topographic guidelines. Between 1,100 and 1,300 meters, a southwest low-level jet blew at 15 to 20 knots. At Zurich Airport, the meteorological visibility at midday in moist fog was 5,000 meters. Moist fog was also observed at Grenchen airfield, with visibility of 4,500 meters at the same time, and 3,700 meters at Emmen airfield. The Mittelland was snow-covered. At the MeteoSwiss measurement station in Zurich-Fluntern, located at 555 meters, a total snow depth of 16 centimeters was measured on the morning of 14 February 2013. The weather at the accident site included 4/8 cirrus clouds at approximately 8,300 meters, visibility of 4,000 meters in moist fog, wind from 160 degrees at 3 knots, a temperature of -6.0 degrees Celsius, a dew point of -8.0 degrees Celsius, and QNH values of 1021 hPa at Zurich (LSZH), 1022 hPa at Grenchen (LSZG), and 1022 hPa at Emmen (LSME). No hazards were reported. The sun was at an azimuth of 166 degrees and an elevation of 29 degrees, with daylight conditions. ## Damage and Casualties The accident resulted in no fatalities or injuries. The single occupant, the student pilot, was uninjured. There were no third-party casualties. The aircraft was severely damaged, and there was no third-party damage.