Airworthiness Directive · Amendment 39-19410 · Tail rotor driveshaft
Airbus Helicopters
This AD applies to Airbus Helicopters Model AS355E, AS355F, AS355F1, AS355F2, and AS355N helicopters, certificated in any category.
We are adopting a new airworthiness directive (AD) for Airbus Helicopters Model AS355E, AS355F, AS355F1, AS355F2, and AS355N helicopters. This AD requires measuring a vibration level in the tail rotor (T/R) drive. This AD was prompted by reports of bearing degradation. The actions of this AD are intended to prevent an unsafe condition on these helicopters.
You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.
(1) Within 165 hours time-in-service (TIS):
(i) Measure the tail rotor (T/R) drive vibration level without balancing the T/R drive, and record the amplitude value.
(ii) Clean the oil cooler fan.
(iii) Measure the T/R drive vibration level without balancing the T/R drive, and record the amplitude value.
(iv) Calculate the difference between the two amplitude values. If the difference is greater than 0.75 inch per second (ips), before further flight, replace each oil cooler fan assembly bearing.
(2) After the effective date of this AD, do not install an oil cooler fan assembly bearing with more than 0 hours TIS unless the requirements of this AD have been accomplished.
