AD 2021-06-05 Requires Replacing Each Affected Engine Mount Bushing With An Improved Engine Mount Bushing

The FAA is superseding Airworthiness Directive (AD) 2017-07-08 for Airbus Helicopters Deutschland GmbH (Airbus Helicopters) Model MBB-BK 117 D-2 helicopters.

AD 2017-07-08 required repetitively inspecting each engine mount elastomeric bushing (elastomeric bushing). Since the FAA issued AD 2017-07-08, Airbus Helicopters has designed an  improved engine mount metal bushing (metal bushing). This new AD retains the inspection requirements of AD 2017-07-08 and requires replacing each affected engine mount bushing with an improved engine mount bushing, while also requiring repetitive inspections of the improved engine mount bushing. This AD also prohibits installing an elastomeric bushing on any helicopter. The actions of this AD are intended to address an unsafe condition on these products. This AD is effective May 7, 2021.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to remove AD 2017-07-08, Amendment 39-18846 (82 FR 16895, April 7, 2017) (AD 2017-07-08), and add a new AD. AD 2017-07-08 applied to Airbus Helicopters Model MBB-BK 117 D-2 helicopters and required repetitive visual inspections of each elastomeric bushing of the inner and outer forward trusses of both engines, and depending on the outcome of the inspections, repairing or replacing the elastomeric bushings. AD 2017-07-08 was prompted by EASA AD 2015-0198, dated September 30, 2015 (EASA AD 2015-0198), issued by EASA, which is the Technical Agent for the Member States of the European Union. EASA advised that during a pre-flight check of a Model MBB-BK 117 D-2 helicopter, an elastomeric bushing was found delaminated. More cases of delaminated elastomeric bushings were reported following additional investigations. According to EASA, this condition could lead to cracks and eventually failure of the engine mount front support pins, possibly resulting in loss of helicopter control.

The NPRM published in the Federal Register on August 27, 2020 (85 FR 52931) and was prompted by EASA issuing a series of ADs to supersede EASA AD 2015-0198. EASA issued AD 2019-0030, dated February 13, 2019 (EASA AD 2019-0030), to supersede EASA AD 2015-0198. EASA AD 2019-0030 advises that Airbus Helicopters has designed an improved engine mount bushing P/N B712M10X1001, which when installed becomes a terminating action for the repetitive inspections of elastomeric bushing P/N 105-60386. Accordingly, EASA AD 2019-0030 requires installation of improved engine mount bushing P/N B712M10X1001 and also prohibits the installation of elastomeric bushing P/N 105-60386 on any Model MBB-BK 117 D-2 helicopter. Since EASA issued AD 2019-0030, occurrences were reported of finding damaged metal bushings. EASA issued AD 2019-0275, dated November 7, 2019 (EASA AD 2019-0275), which retains the requirements of EASA AD 2019-0030 and requires repetitive visual inspections of the metal bushings. EASA AD 2019-0275 also updates the terminology used in the definitions section from affected part to elastomeric bushing and from serviceable part to metal bushing. The NPRM proposed to retain the repetitive visual inspections of AD 2017-07-08 and proposed to require installing metal bushing part number (P/N) B712M10X1001, which would terminate the repetitive inspections of elastomeric bushing P/N 105-60386. The NPRM also proposed to require repetitive inspections of metal bushing P/N B712M10X1001 and prohibit the installation of elastomeric bushing P/N 105-60386 on any helicopter.

FMI: www.regulations.gov