Accident Details
On 27 June 2012 at 1207 UTC, a Piper PA-34-200 Seneca, registration G-BBPX, was involved in an accident at St Mary's Airport, Isles of Scilly. The aircraft was manufactured in 1972 and powered by two Lycoming IO-360-C1E6 piston engines. The private flight carried one pilot and three passengers; none were injured. The aircraft sustained damage to the left main landing gear leg and fuselage skin.
Flight History
The pilot departed Newquay Airport at 1130 UTC with the intention of flying to St Mary's. Before departure, he received a weather forecast indicating a surface wind of 150° at 12 kt, good visibility, nil weather, and few clouds at 300 ft. Upon arrival at St Mary's, the weather was observed as scattered cloud at 200 ft and broken cloud at 300 ft. The pilot elected to fly an NDB approach to Runway 27, with the intention of circling to land on Runway 14.
During the approach, the pilot lost visual contact with the Runway 14 threshold due to a fog bank to the north of the airfield. He initiated a go-around and noted that the south side of the airport was clear of fog and that Runway 27 was clearly visible. The pilot reported no penetration of fog or cloud during the go-around and subsequent approach.
The pilot then requested wind information for Runway 32 but rejected the tailwind component of 15 to 17 kt. He instead opted to land on Runway 27, which had a tailwind component of 8 to 10 kt. The aircraft touched down on the Runway 27 threshold at 75 kt. After touchdown, the pilot applied brakes and deceleration occurred initially. However, as the aircraft transitioned from the asphalt to the grass portion of the runway, braking effectiveness ceased almost entirely. The pilot shut down the engines and switched off the fuel. The left main landing gear struck a runway end light, causing the gear leg to collapse. The aircraft overran the runway and slid down a grass slope before coming to rest upright. The pilot informed air traffic control that all occupants were uninjured and evacuated via the cabin door.
The pilot noted that the wet grass offered minimal braking, and considered this, along with the tailwind component and the downward slope on the latter part of the runway, as direct causal factors. He also acknowledged that pressure to complete the flight, already delayed by weather, and his familiarity with the airport and aircraft may have led to insufficient consideration of performance factors.
Weather and Airport Information
At the time of the accident, a weather observation gave a surface wind from 140° at 16 kt, visibility over 10 km, scattered cloud at 200 ft, and broken cloud at 300 ft. Temperature and dew point were both 15°C. A meteorological forecast issued earlier for the period 1200 to 1900 UTC predicted surface wind from 130° at 15 kt and visibility of 300 m in fog, temporarily improving. A fog warning had been issued for the daytime period.
St Mary's Airport has two runways. Runway 14/32 is 600 m long and all asphalt. Runway 09/27 is 523 m long, partly asphalt and partly grass. Runway 27 is asphalt for the first 287 m (to the crossing with Runway 14/32), then grass. The first 100 m of Runway 27 has an uphill gradient of 4.3%, while the last 100 m slopes downward at 5%. The UK Aeronautical Information Publication warns of the hump-backed nature of the aerodrome and the different braking characteristics between asphalt and grass sections.
Air Traffic Control and Radiotelephony
Air traffic control placed the Rescue and Fire Fighting Service on standby before the aircraft's arrival due to changeable weather. After the pilot discontinued the approach for Runway 14, he requested wind information for Runway 27. The controller reported the wind as 140° at 16 kt, giving an 8 to 10 kt tailwind. The aircraft was observed landing at an estimated 80 to 100 m beyond the threshold. Heavy braking was seen initially but ceased when the aircraft moved onto the grass. RFFS was dispatched at the first sign of the aircraft failing to stop and arrived within seconds. The controller activated the airport's full emergency orders.