AD Number 2024-06-51 Prompted By At Least Four Reports Of Failures Of The Torque Reference Tube Magnetic Insert Braze Joint...

The FAA has sent an Emergency Airworthiness Directive (AD) 2024-06-51 to owners and operators of General Electric Company (GE) Model CT7-2E1, CT7-2F1, CT7-8A, CT7-8E, and CT7-8F5 engines, and various restricted category helicopters with GE Model T700-GE-700, -701A, -701C, -701D/CC, -701D, -401, -401C, CT7-2D, or CT7-2D1 engines installed.

Background: The FAA issued AD 2024-05-51, Amendment 39-22702 (89 FR 18771, March 15, 2024) (AD 2024-05-51), for GE Model CT7-2E1, CT7-2F1, CT7-8A, CT7-8E, and CT7-8F5 engines, and various restricted category helicopters with GE Model T700-GE-700, -701A, -701C, -701D/CC, -701D, -401, -401C, CT7-2D, or CT7-2D1 engines installed. This AD was issued as emergency AD 2024-05-51 on February 28, 2024, and distributed to all known U.S. owners and operators of these engines and helicopters. AD 2024-05-51 required a phase array ultrasonic inspection of the torque reference tube magnetic insert braze joint of the power turbine (PT) drive shaft assembly for inadequate braze coverage, and repair or replacement of the PT drive shaft assembly if necessary.

AD 2024-05-51 was prompted by at least four reports of failures of the torque reference tube magnetic insert braze joint of the PT drive shaft assembly within the last several months. This condition, if not addressed, could result in improper torque and engine speed indications, which, in combination with specific phases of flight, could create an unacceptably high flight crew workload in maintaining control of the aircraft, and result in consequent loss of control of the aircraft.

Actions Since Issuance of AD 2024-05-51: Since the issuance of AD 2024-05-51, the FAA determined that PT drive shaft assembly P/N 5125T92G01 was inadvertently omitted from the applicability. Therefore, the FAA is superseding AD 2024-05-51 to revise the applicability to include engines with PT drive shaft assembly P/N 5125T92G01 installed. The FAA also revised the applicability of this AD to consolidate paragraphs (c)(2)(iii) through (viii) into paragraph (c)(2)(iii) of this AD. 

The FAA is issuing this AD because the agency has determined the unsafe condition described previously is likely to exist or develop in other products of these same type designs. This AD requires a phase array ultrasonic inspection of the torque reference tube magnetic insert braze joint of the PT drive shaft assembly for inadequate braze coverage, and repair or replacement of the PT drive shaft assembly if necessary.

FMI: https://drs.faa.gov/browse/excelExternalWindow/DRSDOCID162625772920240322154720.0001