EASA SIB 2013-16: Pratt & Whitney Canada PT6A Engines — Reduction Gearbox Failures

What to do

Affected operators and maintenance facilities should adhere strictly to the Pratt & Whitney Canada overhaul manual for the reduction gearbox, ensuring replacement of the first stage reduction sun and planet gears as a matched zero-time set during overhaul. If previous repairs did not comply with these criteria, replacement should occur at the next overhaul or within 12,000 hours total time-since-new. No immediate mandatory actions are required, but following these recommendations is advised to prevent failures.

Summary

EASA Safety Information Bulletin 2013-16 is an informational bulletin addressing reduction gearbox failures in Pratt & Whitney Canada PT6A series turboprop engines. It highlights the potential for in-flight engine shutdowns due to premature failure of the reduction gearbox, affecting various aircraft types including the Cessna 208 Caravan, DeHavilland DHC-6 Twin Otter, Pilatus PC-7, and Beech King Air series among others. The bulletin aligns with FAA Special Airworthiness Information Bulletin NE-12-04 and aims to inform operators and maintenance organizations within EASA member states.

What changed

This bulletin introduces awareness of reduction gearbox failures linked to improper maintenance practices, specifically the replacement and installation of first stage reduction sun and planet gears. It does not mandate new regulatory actions but concurs with FAA recommendations to follow overhaul manual procedures and replace certain gearbox components under specified conditions. No Airworthiness Directive action is currently warranted under EU regulations.

Why it matters

The bulletin is important for aviation professionals as it addresses a safety concern that could lead to engine in-flight shutdowns, impacting flight safety and operational reliability. Operators and maintenance organizations must understand the maintenance practices that contribute to gearbox failures to prevent costly engine shutdowns and ensure compliance with manufacturer guidelines. Awareness helps in planning maintenance and overhaul activities to mitigate risks associated with gearbox component wear or incorrect installation.