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Accident Report Detail

​Safety Recommendation Report: Preventing Incorrect Installation of the Beta Arm in Pratt & Whitney Canada PT6A Engines

Executive Summary

​The National Transportation Safety Board (NTSB) is providing the following information to urge the Federal Aviation Administration (FAA) and Pratt & Whitney Canada to take action on the safety recommendations in this letter. These recommendations are intended to prevent the incorrect installation of the reversing lever (beta arm) and related components in PT6A engines, which can cause the propeller to transition uncommanded to feather in flight.1 They are derived from investigations in which the beta arm or related components were found incorrectly positioned. As a result of these investigations, the NTSB is issuing one safety recommendation each to the FAA and Pratt & Whitney Canada.

Probable Cause


To the Federal Aviation Administration:

Issue a special airworthiness information bulletin that directs maintenance personnel, during routine scheduled inspections of and after propeller installation on Pratt & Whitney model PT6A engines, to visually verify that the propeller reversing lever (beta arm) and guide pin are correctly installed and, if necessary, to fix any improper installations. (A-16-53)

To Pratt & Whitney Canada:

As soon as practicable, complete the development and implementation of a redesigned guide pin assembly for PT6A engines to prevent the possibility of the reversing lever (beta arm) and guide pin being incorrectly installed. (A-16-54)

Accident Location: Multiple , Multiple    
Accident Date:  
Accident ID: IAD01LA048; ANC13WA057

Date Adopted: 12/5/2016
NTSB Number: ASR1607
NTIS Number:  

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