NTSB · Safety Recommendation
Safety Recommendation A-16-054
Recommendation
TO PRATT AND 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.
Safety Issue and Context
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. They are derived from investigations of accidents 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.
During the NTSB’s on-scene wreckage examination of a Beech 1900C airplane that collided with terrain following a loss of thrust in the left engine (a Pratt & Whitney Canada PT6A-65B) shortly after takeoff from Miami Executive Airport, Miami, Florida, the left engine's propeller beta arm was found incorrectly positioned over its guide pin rather than under it. (Figure 1 shows exemplar engines with correctly and incorrectly positioned beta arms.) If the beta arm is not secure under the guide pin, the unsecured linkage could release oil pressure in the beta valve and cause uncommanded travel of the propeller to the feather position.
Although metallurgical analysis during the NTSB’s investigation determined that the incorrect beta arm position was a result of impact or postaccident forces and therefore not causal to the accident, the incorrect position of the component was identified as a finding in the investigation.
Response History
September 23, 2025 · NTSB Correspondence · Pratt & Whitney
On September 18, 2025, you informed us that Pratt and Whitney is continuing its work in response to Safety Recommendation A-16-54. We look forward to receiving your next update.
September 18, 2025 · Recipient Response · Pratt & Whitney
-From Toufik Djeridane, Service Investigation Manager, Pratt & Whitney Canada Corporation: Following our latest update communication letter dated October 1st, 2020, P&WC completed the certification of the design change to be implemented in production on the Cessna Caravan engine series (PT6A-114 /114A / 140). The production implementation is scheduled in Q1 2026 and will be accompanied by a retrofit Service Bulletin release for fielded engines.
In parallel, P&WC is expanding implementation of the design change intent to other PT6A models for which further installation validations are required prior to final configuration release.
P&WC will keep you informed on the progress made for the tasks listed above as soon as a significant milestone is achieved.
Should you require any additional information, please do not hesitate to contact me.
September 18, 2020 · NTSB Correspondence · Pratt & Whitney
We continue to believe that your ongoing work with the original equipment manufacturer to design a new guide pin assembly that fits all installations is responsive to this recommendation. Pending completion of this effort and implementation of the redesigned guide pin assembly on aircraft equipped with PT6A engine models, Safety Recommendation A-16-54 remains classified OPEN--ACCEPTABLE RESPONSE.
Please update us at ExecutiveSecretariat@ntsb.gov on your progress toward implementing this recommendation, and do not submit both an electronic and a hard copy of the same response.
May 6, 2020 · Recipient Response · Pratt & Whitney
-From Jean-Francois Houle, Service Investigation Manager, Pratt and Whitney, Canada: P&WC recently completed the field trial fit of the new guide pin bracket onto the first target aircraft with the PT6A-114, PT6A-114A or the PT6A-140 engine models. The trial fit demonstrated the design intent of the new guide pin bracket, that when the propeller reversing lever (beta arm) – is incorrectly placed above the guide pin bracket during engine rigging, it would not allow the beta block to engage with the beta ring.