On May 12, 2014, the FAA published a Notice of Proposed Rulemaking (NPRM) proposing an Airworthiness Directive (AD) affecting certain Honeywell International Inc. turboprop engines. This proposal would require replacement of affected propeller shaft couplings and insertion of a copy of Honeywell Operating Letter into the FAA-Approved Flight Manual. This proposed AD would affect TPE331-5, -5A, -5AB, -5B, -10, -10R, -10U, -10UF, -10UG,-10UGR, and -10UR model turboprop engines, with a propeller shaft coupling, part number (P/N) 3107065-1, 865888-3, 865888-6 or 865888-8, installed.

 

This AD was prompted by engine propeller shaft coupling failures leading to unexpected propeller pitch changes resulting in high aerodynamic and asymmetric drag on the airplanes upon failure. The condition could be critical to maintaining control on twin-engine airplanes. The FAA is proposing this AD to prevent loss of airplane control, leading to an accident. 

 

The proposed AD would require, removing the shaft coupling from service by the earliest of the following:

• Next piece-part exposure; or
• Next turbine (hot) section inspection (HSI); or
• Before accumulating an additional 3,600 cycles after the effective date of this AD. Exceptions are engines installed on Mitsubishi MU-2 series which must be replaced before accumulating 1,200 cycles; CASA C-212 series and Twin Commander 690 and 695 series which must be replaced before accumulating 2,400 cycles. Certain other listed aircraft and all others not listed, including ag aircraft, fall into the 3,600 cycle limit. 

Additionally, within 60 days, applicable aircraft must insert a copy of Honeywell Operating Limitation Letter OI331-26, dated March 2, 2010, into the FAA-Approved Flight Manual. 

 

We recommend that you read the NPRM and service information carefully and make any comments regarding overall regulatory, economic, environmental and energy aspects of this proposed AD. Comments are due by July 11, 2014. They should be sent by one of the methods explained to the address given in the NPRM and include “Docket No. FAA-2012-0913; Directorate Identifier 2012-NE-23-AD” at the beginning of the comments.