The European Union Aviation Safety Agency (EASA) has issued an Airworthiness Directive (AD) announcing mandatory work to be undertaken on all E4 and E4P Jet-A1-powered piston engines installed in Diamond Aircraft, including the popular twin-engine DA-42 NG trainer in use at a large number of flight schools across the world.
The AD refers to a Mandatory Service Bulletin (MSB) from Diamond that has been issued following a number of engine failures resulting from a failure of inner main bearing cap screws, which engine
manufacturer Austro Engine (a subsidiary of Diamond Aircraft) states were produced at the “lower end of the material strength tolerance for Class 8.8 screws”.
For recently overhauled engines, the MSB states that bearing cap screws can wait to be replaced until 300 flight hours have been accumulated or at the next scheduled maintenance action – whichever occurs first. For engines with higher flight hours since overhaul, however, the replacement must be undertaken straight away with aircraft effectively grounded until completed, aside from permitting a day VFR ferry flight (of no more than three hours duration) to get aircraft to their maintenance providers.
EASA’s AD states: “Occurrences of engines failures have been reported, where, during subsequent engine inspection, failure of one inner main bearing screw was identified. Subsequent investigation determined that certain screws, meeting the lower end of their design specification, could fail when installed on the inner main bearing position and the engine is operated in specific operating conditions.
“This condition, if not corrected, could lead to engine failure, reduced control of the aeroplane and, for single engine aeroplanes, in emergency landing, possibly resulting in damage to the aeroplane and injury to occupants. To address this potential unsafe condition, Austro Engine published the MSB, providing instructions to replace the affected part with screws of higher class, and EASA issued Emergency AD 2024-0037- E, requiring replacement of affected parts with serviceable parts and providing additional criteria for installation of the affected parts and engines.”
According to Diamond, some 3,000 E-series engines have been manufactured and installed in Diamond aircraft since production began back in 2009, with more than 2.5 million flight hours (FH) accumulated over the last 15 years.
Image accredited to Diamond Aircraft
