Airworthiness Directive · Amendment 39-17090 · Dc generating system
Agusta S.p.A. Helicopters
This AD applies to Agusta S.p.A. (Agusta) Model AB139 and AW139 helicopters, with a generator control unit (GCU), part-number (P/N) 1152550-3 installed; certificated in any category.
We are adopting a new airworthiness directive (AD) for Agusta S.p.A. (Agusta) Model AB139 and AW139 helicopters with a certain generator control unit (GCU), to require replacing each affected GCU with an airworthy GCU. This AD was prompted by laboratory tests which revealed a potential fault in the overvoltage protection on a certain part-numbered GCU. The actions are intended to prevent failure of the overvoltage protection of the GCU, degraded performance of the electrical power generation and distribution systems, a fire, and subsequent loss of control of the helicopter.
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) Remove the No. 1 and No. 2 GCU, P/N 1152550-3. Do not install GCU, P/N 1152550-3, on any helicopter.
(2) Modify the electrical connector A13P1 (GCU No. 1) and A14P1 (GCU No. 2) by installing the wiring to the power distribution panel (PDP) for your serial-numbered helicopter as depicted in Figure 1 of Agusta Bollettino Tecnico No. 139-133, Rev. A, dated March 17, 2009.
(3) Using either GCU P/N 1152550-4 or GCU P/N 1152550-5, install a No. 1 and No. 2 GCU that has the same part number. Having different part-numbered GCUs on the same helicopter is not approved.
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.
Aircraft
