What happened
On June 21, 2017, a Diamond DA 40 NG, registration LN-FTR, operated by Pilot Flight Academy, was conducting an IFR training flight from Torp Airport Sandefjord to Karlstad, Sweden. While cruising at 6,000 feet near Fredrikstad, the crew heard a loud bang from the engine. This was immediately followed by unstable RPM fluctuations and a progressive loss of engine power.
As the engine eventually ceased operation entirely, the crew attempted to reach Moss Airport Rygge. However, realizing the aircraft could not reach the airfield, the instructor executed a forced landing in a field near Rå andde Church. There were no injuries to the two crew members, and the aircraft sustained no damage during the landing.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the engine and the circumstances surrounding the flight. The investigation noted that the aircraft had recently undergone maintenance, having left a repair shop only the previous day following a cylinder head replacement. Since that maintenance, the aircraft had completed 5.5 flight hours without any reported issues.
Investigators analyzed the internal state of the engine, which showed extensive damage. The investigation focused on two primary theories regarding the origin of the failure: whether the timing chain had been incorrectly installed during the recent maintenance, or if the failure began with localized damage in cylinder 1, such as a faulty injection nozzle or valve failure, which then cascaded through the remaining cylinders.
Findings
Technical analysis confirmed that the engine suffered significant internal damage, specifically starting in cylinder 1. The destruction of components in the first cylinder likely spread to the other cylinders, leading to a total loss of compression and eventual engine seizure.
While the investigation could not definitively prove whether the cause was incorrect timing chain installation or a localized component failure, the pattern of damage was consistent with faulty timing. The crew was unable to prevent the failure or restart the engine once it stopped, though the NSIA noted the emergency was handled effectively by the flight crew.