What happened
On September 23, 2015, a Piper PA-28-181, registration SE-LTH, was conducting a private VFR flight from Nyköping/Skavsta airport to Öresten airfield. Upon arrival, the pilot performed a low pass to assess the condition of the grass runway, which was wet with visible puddles.
During the approach to runway 24, the pilot maintained an airspeed of approximately 70 knots at the threshold, touching down roughly 40 to 50 meters into the runway with full flaps. Following touchdown, the pilot noted reduced braking effectiveness and a tendency for the aircraft to yaw. To avoid further instability, the pilot initially refrained from heavy braking. As the aircraft approached the end of the runway, the pilot attempted to brake repeatedly, but the aircraft overran the threshold, passed through an area of tall grass, and descended a short slope into a swampy area. The aircraft sustained substantial damage, though the pilot and passenger were unharmed.
The investigation
The Swedish Accident Investigation Authority (SHK) examined the aircraft' and runway conditions. Investigators found that no performance calculations had been conducted prior to the flight. Calculations based on the aircraft's manual, including safety margins for wet grass, indicated that the required landing distance exceeded the available runway length by approximately 35 meters.
To further understand the aircraft's behavior, SHK conducted flight tests using the same model on a similar wet grass surface. These tests revealed that an average rolling distance of 580 meters was achieved without braking and at idle power. The tests suggested that additional engine power would be required to achieve a stopping distance greater than 580 meters under such conditions.
Findings
The investigation concluded that the runway excursion was caused by a combination of several factors:
- The touchdown speed was likely too high.
- The engine may have been producing thrust during the landing roll.
- The pilot did not utilize the brakes to their full extent.
- The aircraft may have experienced aquaplaning during the early stages of the landing roll.