What happened
On 11 September 2017, a Piper PA-28RT-201 Cherokee Arrow IV, registration G-BHAY, was performing a private flight from London Southend Airport to Newcastle International Airport. While flying over the Wash, the pilot reported a significant engine roughness and subsequently declared a mayday. During the emergency, the pilot reported smoke in the cockpit, which was likely caused by engine fumes entering the cabin, and shortly thereafter, the engine failed completely.
As the aircraft descended, the pilot attempted to navigate toward the coast to find a suitable landing site. Witnesses observed the aircraft flying at a very low altitude, noting that the propeller was no longer rotating. The aircraft was seen to turn and stall just before striking a berm, known as the old sea wall, at a high rate of descent. The impact caused severe damage to the engine, fuselage, and landing gear. Both the pilot and the passenger sustained fatal injuries.
The investigation
The AAIB investigation focused on the mechanical state of the Lycoming engine and the circumstances leading to the loss of power. Investigators examined the engine components and found significant evidence of internal damage. Specifically, the No 1 and No 2 cylinders showed evidence of blow-by and piston ring wear, which led to the fouling of spark plugs. This degradation caused a loss of oil through the engine breather.
As the oil level depleted, the remaining lubricant overheated, leading to the failure of the big-end bearings. The investigation established that the No 4 connecting rod eventually detached from the crankshaft, causing a breach in the crankcase and the total cessation of engine operation. The investigation also reviewed the aircraft's maintenance history, noting a period of several months where the aircraft was parked outside at Newcastle International Airport without known engine inhibition measures.