Airworthiness Directive · Amendment 39-17820 · Turbomeca S.A. Turboshaft Engines
Turbomeca S.A. Turboshaft Engines
This AD applies to Turbomeca S.A. Arriel 2B1 turboshaft engines that do not have modification TU157 incorporated.
We are superseding airworthiness directive (AD) 2007-19-09R1 for all Turbomeca S.A. Arriel 2B1 turboshaft engines that do not have modification TU157 incorporated. AD 2007-19-09R1 required replacement of the hydromechanical metering unit (HMU) with a serviceable HMU. This AD requires HMU replacement; reduction of the compliance interval; and inclusion of the power turbine C2 cycle consumption rate when determining compliance times. This AD was prompted by reports of ruptures on HMU constant delta pressure valves that have less than 2,000 hours in service. We are issuing this AD to prevent failure of the HMU, which could lead to damage to the engine, and damage to the aircraft.
(1) HMU operating hours and power turbine C2 cycles are known:
(i) If on the effective date of this AD, the HMU C2 cycles are less than 900, then replace the HMU before the HMU accumulates 1,000 C2 cycles or 1,500 HMU operating hours, whichever occurs first;
(ii) If on the effective date of this AD, the HMU C2 cycles are 900 or more, then replace the HMU within 100 HMU C2 cycles after the effective date of this AD;
(iii) Thereafter, replace the HMU at every 1,000 HMU C2 cycles or 1,500 HMU operating hours, whichever comes first.
(2) HMU operating hours are known and C2 cycles are not known:
(i) If on the effective date of this AD, the HMU operating hours are less than 1,100, then replace the HMU before accumulating 1,200 HMU operating hours;
(ii) If on the effective date of this AD, the HMU operating hours are 1,100 or more, then replace the HMU within 100 HMU operating hours after the effective date of this AD;
(iii) Thereafter, replace the HMU at every 1,200 HMU operating hours.
For the purpose of this AD, HMU operating hours or C2 cycles are defined as operating hours or C2 cycles since new, since overhaul, or since incorporation of Turbomeca S.A. Service Bulletin (SB) No. 292 73 2105, Version B, dated December 16, 2010, or earlier version, or Turbomeca S.A. Mandatory SB (MSB) No. 292 73 2818, Version D, dated June 24, 2013, or earlier version.
Incorporation of Turbomeca S.A. SB No. 292 73 2157, Version C, dated July 17, 2013, or earlier version, is terminating action to the replacement and repetitive inspection requirements of this AD.
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.
