Summary
We propose to adopt a new airworthiness directive (AD) for certain Eurocopter Model EC225 LP helicopters. This proposed AD would add a new operating limitation that would require increasing the minimum density altitude flight limitation for helicopters without certain Eurocopter modifications installed. This proposed AD is prompted by a report that flights below a certain density altitude create oscillations in the main rotor which can transfer dynamic loads to the structure, the main gearbox (MGB), and the main servo-control inputs, which could result in subsequent loss of control of the helicopter.