AD 2021-05-07 Requires Inspecting The Starter-Generator Electrical Ground Connection

The FAA is adopting a new airworthiness directive (AD) for Airbus Helicopters Deutschland GmbH (Airbus Helicopters) Model BO-105A, BO-105C, BO-105S, MBB-BK 117 A-1, MBB-BK 117 A-3, MBB-BK 117 A-4, MBB-BK 117 B-1, MBB-BK 117 B-2, and MBB-BK 117 C-1 helicopters.

This AD was prompted by a report of a loss of electrical ground between the starter-generator and the generator voltage regulator (regulator). This AD requires inspecting the starter-generator electrical ground connection, retrofitting the starter-generator wire harness, and depending on model, revising the existing Rotorcraft Flight Manual (RFM) for your helicopter. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective April 16, 2021.

Supplementary Information: The European Aviation Safety Agency (now European Union Aviation Safety Agency) (EASA), which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2015-0098, dated June 2, 2015 (EASA AD 2015-0098), and EASA AD 2015-0220, dated November 9, 2015 (EASA AD 2015-0220) (also referred to as the Mandatory Continuing Airworthiness Information, or the MCAI), to correct an unsafe condition for all Airbus Helicopters Model MBB-BK117 A-1, MBB-BK117 A-3, MBB-BK117 A-4, MBB-BK117 B-1, MBB-BK117 B-2, and MBB-BK117 C-1 helicopters; and Airbus Helicopters Model BO105 A, BO105 C, BO105 D and BO105 S helicopters with certain part-numbered voltage regulators.

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain Airbus Helicopters Model BO-105A, BO-105C, and BO-105S helicopters; and all Airbus Helicopters Model MBB-BK 117 A-1, MBB-BK 117 A-3, MBB-BK 117 A-4, MBB-BK 117 B-1, MBB-BK 117 B-2, and MBB-BK 117 C-1 helicopters. The NPRM published in the Federal Register on July 16, 2020 (85 FR 43153). The NPRM was prompted by a report of a loss of electrical ground between the starter-generator and the regulator. The NPRM proposed to require inspecting the starter-generator electrical ground connection, retrofitting the starter-generator wire harness, and depending on model, revising the existing RFM for your helicopter.

The FAA is issuing this AD to address the loss of electrical ground between the starter-generator and the regulator. This condition could result in an overvoltage of electrical power, damage to electronic equipment, and subsequent loss of control of the helicopter.

FMI: www.regulations.gov