Incident
On 11 April 1998, a Piper PA-23-250 (registration EI-BYK) was on a private ferry flight from Waterford, Ireland, to Exeter, England, where it was scheduled for an annual inspection. An Irish Ferry Permit had been issued for the flight. A Cessna 182 flew in formation with the aircraft and handled radio communications due to an intermittent problem with the Piper's press-to-transmit switch.
Approximately five minutes after passing Strumble VOR at Flight Level 60, the right engine began to run roughly. The pilot trimmed the aircraft for single-engine flight and performed engine failure checks, which included selecting the right electric fuel pump to ON, switching fuel tanks, selecting alternate air, and setting the fuel mixture to fully rich. However, the rough running increased until the engine was producing no useful power. The pilot attempted cross-feeding fuel, but with no improvement.
A few minutes later, the left engine began to misfire when the aircraft was about 6 nautical miles from Worms Head. The pilot turned towards land in a shallow descent and transmitted a Mayday call to London Information, which had difficulty receiving the transmission. After the pilot provided his position, he was instructed to switch to the emergency frequency of 121.5 MHz, and the accompanying Cessna 182 took over radio communications.
Assessing the coastal fields as too small and undulating for a forced landing, the pilot determined that the beach offered the best available landing area, as the tide was out. The aircraft subsequently landed successfully on firm sand at Rhossilli Beach and was attended by local police and the Coast Guard. A police officer later confirmed the fuel tank contents: the inner tanks were two-thirds full, and the outboard tanks were low.
Post-Landing Examination
The aircraft was pulled clear of the high water mark and examined the following day by maintenance engineers from Exeter Airport. Fuel drains and filters were checked, revealing a small amount of grey, powdery material in the filter from the right engine. However, fuel flow to the right engine was satisfactory, and the injector filter and injector lines were clear. No evidence of contamination was found in the left engine fuel system.
Engine runs were conducted: the left engine ran normally, but the right engine operated unevenly. Removal of the fuel injectors from the right engine revealed that three nozzles were completely blocked and one was partially blocked. These were cleaned as well as possible under the circumstances, and a further engine run was carried out. The No. 6 cylinder on the right engine still ran cold, so the associated injector was removed and cleaned again. The next engine run was satisfactory.
The pilot was asked to carry out a high-speed run on the hard sand with an engineer onboard, which was successful. The engineer then disembarked, and the pilot flew the aircraft the short distance to Swansea Airport, where the fuel filters were re-checked. The aircraft later flew to Exeter Airport without further incident.
The aircraft is currently undergoing an Annual 'Star' Inspection, during which the fuel injectors and manifold valve will be sent to an overhaul agent for strip examination. The fuel tanks are also scheduled for removal, inspection, and cleaning.
Probable Cause
Neither the source nor the investigation explicitly state a singular probable cause for the event. However, the engineering examination confirmed that the right engine problem was caused by sediment blocking several injector nozzles. The cause of the misfiring on the left engine was not identified. The pilot considered that in his efforts to resolve the problems, he may have attempted every combination of engine/fuel tank selection, potentially introducing air to the left engine from one of the low-fuel outboard tanks.