Airworthiness Directive · Amendment 39-13839 · Eurocopter Deutschland GmbH Model EC135 P1, P2, T1, and T2 Helicopters
Eurocopter Deutschland GmbH Model EC135 P1, P2, T1, and T2 Helicopters
Model EC135 P1, P2, T1, and T2 helicopters, with main rotor drive aluminum torque strut assembly (strut), part number (P/N) L633M1001 103 or L633M1001 105, installed, certificated in any category.
This amendment supersedes an existing airworthiness directive (AD) for Eurocopter Deutschland GmbH (Eurocopter) Model EC135 P1, P2, T1, and T2 helicopters. That AD currently requires adding the AD or a statement to the Rotorcraft Flight Manual (RFM) informing the pilot to reduce power and land as soon as practicable if a thump-like sound followed by an unusual vibration occurs during flight. That AD also requires visually inspecting the main rotor drive torque strut assembly (strut) for a crack or a break, recording the inspections in the historical or equivalent record, re-marking and relocating the strut, as appropriate, and replacing any unairworthy strut with an airworthy strut. Also, that AD establishes life limits for certain struts and revises the life limit for other struts. This amendment requires the same actions as the existing AD except that it changes the visual inspection from a one-time inspection to daily inspections; reduces the life limit for aluminum struts; and eliminates the once-only transfer and remarking of certain struts. This amendment is prompted by an incident in which a pilot felt an in-flight increase in vibration and subsequent discovery of a failed strut. The actions specified by this AD are intended to prevent failure of a strut and subsequent loss of control of the helicopter.
To prevent failure of the strut and subsequent loss of control of the helicopter, do the following:
(a) Before further flight, insert a copy of this AD or insert a statement into the Emergency Procedures Section of the Rotorcraft Flight Manual (RFM) to inform the pilot to reduce power and land as soon as practicable if a thump-like sound followed by an unusual vibration occurs during flight.
(b) Before the first flight of each day, using a light and mirror, inspect each aluminum strut for a crack or a break by following the Accomplishment Instructions, paragraph 3.B. of Eurocopter Alert Service Bulletin EC135-63A-002, Revision 4, dated July 7, 2003 (ASB). Replace any cracked or broken strut with a new titanium strut, P/N L633M1001 104, before further flight.
(c) Within the next 100 hours time-in-service (TIS), for each aluminum strut with 400 or more hours TIS, replace each aluminum strut with a titanium strut, P/N L633M1001 104.
(d) This AD revises the Airworthiness Limitations section of the maintenance manual by reducing the retirement life of each aluminum strut, P/N L633M1001 103 and L633M1001 105, to 500 total hours TIS or retiring them no later than December 31, 2004, whichever comes first.
(e) The aluminum struts must be replaced with titanium struts in pairs and at the same time. Installing one aluminum strut and one titanium strut is not authorized. After installing titanium struts, recalculate the weight and balance using 0.356kg as the weight and 1498.76kgmm as the moment for both titanium struts.
Note 1: The once-only transferring and remarking of certain aluminum struts provided in the superseded AD are no longer authorized.
(f) Replacing aluminum struts, P/N L633M1001 103 and L633M1001 105, with titanium struts, P/N L633M1001 104, constitutes terminating action for the requirements of this AD. Titanium struts have no life limit.
(g) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Contact the Safety Management Group for information about previously approved alternative methods of compliance.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
