What happened
On June 19, 2011, a Piper Aircraft PA18-90, registered LN-LJJ, was conducting a flight from Bagnères de Luchon to the Pène de Soulit altisurface. The pilot attempted an initial landing at a final approach speed of 52 knots but determined the touchdown point was too far down the runway, necessitating heavy braking on the upper platform.
Seeking a better landing, the pilot performed a second circuit, intentionally reducing the final approach speed by seven knots. During the flare, the aircraft experienced a descent and subsequently stalled, striking the unpaved runway approximately two meters past the threshold. The pilot noted a tailwind component of between five and eight knots during the approach. The impact caused damage to the propeller and destroyed the main landing gear.
The investigation
The investigation examined the specific characteristics of the Pène de Soulit altisurface, which features a short, unpaved runway with a significant slope. The investigators noted that the runway gradient is steep at the approach threshold and decreases toward the upper platform.
Expert testimony from an instructor pilot familiar with the site highlighted that afternoon meteorological conditions at this location can create challenging aerodynamic environments. The investigation also looked at the aerodynamic implications of landing on steep slopes, noting that the required pitch angle during the flare is much greater than on level terrain. This increased load factor effectively raises the stall speed.
Findings
- The pilot attempted a low-speed approach without accounting for the specific aerodynamic effects caused by afternoon weather patterns at this high-altitude site.
- The reduction in approach speed for the second attempt left an insufficient margin above the stall speed.
- While a higher approach speed might have been necessary to counteract a 10-knot gust, such a speed increase would have made landing on the short runway impossible.
- The aircraft stalled due to an approach at too low an energy state, failing to compensate for the local atmospheric conditions and the increased stall speed caused by the steep landing slope.