European safety regulators have banned aerobatic activity with XtremeAir XA42 single-engined sports aircraft over concerns that the engine could break away from the airframe.

The prohibition, which also applies to the XA41 model, follows discovery that both diagonal struts of the engine mount on one aircraft had separated.

Diagonal struts on the type had already been subject to an urgent check regime in March last year after cracks had been detected during scheduled maintenance.

The European Union Aviation Safety Agency says the XA42 aircraft flight manual must be amended to read “Aerobatic manoeuvres prohibited”, and a corresponding placard must be fitted in full view of the pilot.

EASA has also tightened the inspection regime, requiring a check on the engine-mount struts before each flight, rather than after every 10 acrobatic flights.

The cracks and possible separation of the struts could lead to “in-flight detachment of the engine”, warns the regulator.

German-based XtremeAir has issued a service bulletin containing inspection instructions and operational limitations. The two-seat XA42 and single-seat XA41 are powered by a Lycoming AEIO-580 piston engine.