1999 Cessna 172M Accident at Berwyn Mountain, Mid Wales (G-BXLJ)

Accident Overview and Flight Details On 12 February 1999, a 1976 Cessna 172M, registration G-BXLJ, was destroyed in a private flight accident at Berwyn Mountain, Mid Wales. The aircraft was powered by a single Lycoming O-320-E2D piston engine. Three people were on board: two crew members and one passenger. All three occupants sustained fatal injuries when the aircraft initially struck the mountainside. ## Occupants and Qualifications The aircraft commander held a Commercial Pilot's Licence with an Assistant Flying Instructor's (AFI) rating. He was 41 years old and had 1,002 total flying hours, including 180 hours in the preceding 90 days and 62 hours in the last 28 days. The pilot who hired the aircraft held a Private Pilot's Licence issued on 7 October 1994 and a current Instrument Meteorological Conditions rating. His logbook showed 172 total hours, with 6 hours on type. Because the hiring pilot had not flown since 28 November 1998, the AFI accompanied him to satisfy the operator's four-week currency requirement. The AFI signed the technical log as aircraft commander, though the hiring pilot likely handled the controls for most of the flight. A student pilot in the rear seat was assumed to have played no active role. ## Flight History and Radar Data The three occupants boarded at Welshpool Airfield at about 1510 hrs UTC. Takeoff occurred shortly after 1515 hrs. Clee Hill Radar recorded secondary returns starting at 1525 hrs, with the first return 3 nautical miles west of the airfield at 1,558 feet. The aircraft tracked about 343°(M) at a groundspeed of about 90 knots and climbed to about 2,000 feet. It continued northwest, passing half a nautical mile west of Llanfyllin at 1531 hrs. Radar contact was lost shortly after 1534 hrs when the aircraft descended to about 1,558 feet above mean sea level while entering the valley between Llanrhaeadr-ym-Mochant and Tan-y-pistyll. Eyewitnesses observed the aircraft flying up the valley to the left of the road, below the valley side, and appearing to fly normally. The weather was good with only a light wind, and the tops of adjacent hills were not in cloud. Radar contact was regained at 1536 hrs at 2,158 feet, about 1 nautical mile north of the valley's end. The aircraft tracked north and began climbing. Near Llyn Lluncaws, at 2,358 feet, the rate of climb increased to about 725 feet per minute while groundspeed decreased from about 85 knots to about 45 knots. The last radar contact was at 1536:58 hrs at 2,558 feet, about one-third of a nautical mile north of the wreckage site, where the ground elevation was 800 metres (2,625 feet). ## Search and Recovery When the aircraft had not returned by 1630 hrs, airfield staff reported their concern to the Welshpool Airport operating company director at about 1655 hrs. After unsuccessful radio calls, the director informed the Distress and Diversion cell at the London Area and Terminal Control Centre at 1728 hrs. Overdue action was initiated, and the Rescue Co-ordination Centre was informed. A radar replay identified a track that disappeared at about 1537 hrs, and the last contact position was passed to the RCC. The Mountain Rescue Team at RAF Valley was mobilized, but weather precluded a helicopter search. A refined position from radar data defined the search area. At 2133 hrs, the MRT met local police and began the search in fog with visibility estimated at 200 metres. The wreckage was located at 0126 hrs, about half a nautical mile from the last radar contact. The aircraft had flown into steeply rising ground and tumbled back about 50 metres down the slope. ## Engineering Investigation The aircraft was found on the east-facing slope of Moel Sych at about 2,300 feet above mean sea level. An area of rock surface about 200 feet higher on the escarpment showed white and blue paint smears, with oil-coated rocks and grass immediately below. The detached noseleg had lodged at the foot of the escarpment. Almost all of the aircraft's structure lay at one location, held together largely by flying control cables. The cockpit and nose had disintegrated, and the two wings had separated. The engine and instrument panel lay close to the main wreckage. The broken airframe showed extensive impact damage from tumbling down the hillside. About half of one propeller blade was missing, having broken off in forward bending with leading-edge-upwards twisting. The other blade was bent rearwards through more than 180 degrees from multiple rotational impacts. The propeller condition indicated considerable power was being transmitted at impact. The pilot's throttle control was found near the closed position, though it was not possible to determine whether it had been moved during impact or selected closed beforehand. Other panel controls were in rational positions: the magneto switch was at BOTH, the mixture control at RICH, the primer was locked, and carburettor heat was at COLD. A small amount of clean Avgas 100LL was recovered from the left tank. Examination showed the aircraft had been complete at impact, with no pre-existing failure in the structure or flying controls. A massive impact on the underside of the nose removed the noseleg, crushed the carburettor and silencer, and crushed the lower half of the firewall and fuselage belly structure just aft of the firewall in an upwards and rearwards direction. The blue-painted engine sump was scored and damaged, and white paint from the fuselage probably identified this damage with the impact point on the rock face. Damage to the leading edge and underside of the right wing tip, just inboard of the plastic tip fairing, was likely incurred in flight. The wing skin was crushed rearwards, directly cordwise. Although this damage was at the right wing tip, other evidence showed the aircraft was approaching the escarpment from the left. This conflict could be reconciled if the aircraft was steeply banked to the right at impact. The fore-and-aft direction of the initial impact damage indicated the aircraft was in balanced forward flight at impact, albeit probably banked, suggesting no loss of control before impact. The engine was stripped, and nothing was found that was likely to have caused a substantial loss of power, consistent with the propeller condition indicating high rotational energy at impact. The lower compression ring on one cylinder was broken but remained in its groove without causing secondary damage. The left magneto had broken off but performed normally on test. The right magneto showed internal wear and retarded internal timing, but its timing on the engine was within limits. It produced some misfiring at low speeds but ran normally above 1800 RPM.