Report on aviation accident at Ångardsvatnet in Oppdal municipality 26 February 2017 involving Dyn Aero MCR 4S, LN-DLH

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Description

On 26 February 2017 LN-DLH was on the way from Ålesund Airport (ENAL) to Røros Airport (ENRO) at a height of approx. 9000 ft. A few minutes after passing Molde, a bang was heard and vibration occurred in the engine. The commander decided to perform an emergency landing on the frozen lake Ångardsvatnet. Due to a a snow layer on the ice, the aircraft groundlooped and settled with the nose into the snow. There was extensive damage to the aircraft. Neither the pilot nor the two passengers were physically injured.

The examination of the engine revealed that one of the engine's pistons had failed. The piston slanted in the cylinder and hit the cylinder head with subsequent rupture of the connecting rod. The piston skirt had broken off on one side. Similar incipient fractures were found in the other three pistons. The engine did not have Rotax original pistons, and they did not have full circumference piston skirts as the original pistons had.

A metallurgical examination of the pistons showed that they had a coarse granular structure. Such a structure weakens the properties of the material, and the crack formation in the pistons was of an intergranular nature. Damages were found in the piston tops indicating that detonation had occurred. EDS analysis showed that there were ferrous fragments embedded in the piston crowns, and the damages were atypical as symptoms of detonation. The cause of these damages has not been found.

The investigation revealed a number of violations of Norwegian regulations regarding the production of the engine parts and the modification of the engine.

No safety recommendations is issued in connection with this investigation.

Location
Ångardsvatnet, Oppdal municipality, Trøndelag county, Norway
Occurrence date
26.02.2017
Aircraft
Other light aeroplane
Operator
Private
Registration
LN-DLH
Meteorological conditions
VMC
County
Trøndelag
Type of occurrence
Accident
Type of operation
Private (club)
Category of operation
Light, aeroplane (< 5 700kg)
Aircraft category
Landplane, Single-engine, Piston engine
FIR/AOR
ENBD (Bodø ATCC)
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