Prompted By Tail Rotor De-Icing Power Supply Box Stuck In 'Closed' Position
The FAA has issued an emergency AD (EAD) for Airbus Helicopters Model AS332C, AS332C1, AS332L, and AS332L1 helicopters.
The EAD was prompted by a report of a tail rotor (T/R) de-icing system power supply box stuck in a “closed” position providing an uncontrolled and un-annunciated power supply to the system. The T/R de-icing system is part of the entire rotor de-icing system. This EAD requires inspecting certain T/R blades, replacing the set of T/R blades if there is damage, deactivating the rotor de-icing system, revising the rotorcraft flight manual (RFM), and installing a placard. These EAD actions are intended to detect and prevent structural damage to the T/R blades caused by overheating, and subsequent loss of control of the helicopter.
The European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union, issued EASA EAD No. 2015-0153-E, dated July 24, 2015, to correct an unsafe condition for Airbus Helicopters Model AS 332 C, AS 332 C1, AS 332 L, and AS 332 L1 helicopters, equipped with T/R de-icing installation unit part number (P/N) 204ZP01Y01 and T/R blade P/N 332A12-0055-XX (where XX represents any dash number). EASA advises of a report of a T/R blade that was overheated and damaged after application of alternating current (AC) from a ground power unit (GPU) following a flight during which the de-icing system was used. Subsequent analysis determined failure of the power supply box stuck in the “closed” position caused the uncontrolled power supply to the rotor blade de-icing system and subsequent damage. EASA also states that its EAD is considered an interim action and further AD action may follow.
The FAA determined that these helicopters have been approved by the aviation authority of France and are approved for operation in the United States. Pursuant to our bilateral agreement with France, EASA, its technical representative, has notified us of the unsafe condition described in the EASA EAD. We are issuing this EAD because we evaluated all information provided by EASA and determined the unsafe condition exists and is likely to exist or develop on other helicopters of these same type designs.
Airbus Helicopters issued Alert Service Bulletin No. AS332-05.01.02, Revision 0, dated July 22, 2015 (ASB), which specifies, before each flight and before starting at least one engine, if the applicable helicopter has been supplied external 115V/400Hz AC GPU with the rotor stationary or if the de-icing system has been used or tested using an AC GPU with the rotor stationary or spinning, visually inspecting the T/R blades for burn marks, detached leading edge protection, or cracks at the skin/leading edge protection junction. If at least one T/R blade is damaged, the ASB specifies replacing all of the T/R blades.
This EAD requires, before further flight, inspecting each T/R blade for a burn mark, any disbonding of the leading edge protection, and a crack at the junction of the skin and the leading edge protection. If there is a burn mark, any disbonding of the leading edge protection, or a crack at the junction of the skin and the leading edge protection on a T/R blade, this EAD requires replacing all of the T/R blades with airworthy T/R blades. This EAD also requires deactivating the rotor de-icing system, revising the RFM to state that flight into known icing is prohibited, and installing a placard stating that the rotor de-icing system is deactivated.
The EASA EAD allows operation of the rotor de-icing system with a recurring inspection of the T/R blades. This EAD requires an initial inspection and prohibits operation of the rotor de-icing system by deactivating the rotor de-icing system, revising the RFM to state flight into known icing is prohibited, and installing a placard stating that the rotor de-icing system is deactivated.
The FAA says it considers this EAD to be an interim action. Once a modification to the rotor de-icing system design is evaluated, approved, and available, we might consider additional rulemaking.
(Image from file)
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