EASA SIB SAFO15007
Pratt & Whitney R-985 (Wasp Junior) Engines — Flyweight Hardware Failures
Summary
SAFO 15007 is a Safety Alert for Operators issued by the FAA regarding Pratt & Whitney R-985-AN-14B (Wasp Junior) engines. It addresses failures caused by fatigued flyweight screws and improperly modified or under-torqued expanders, which have led to in-flight engine failures and forced landings. The alert also applies to other Pratt & Whitney Wasp Jr (R-985 Series) and Wasp (R-1340 Series) engines used in various aircraft including Air Tractor AT-301 and 401, Ayres Thrush, Beechcraft D17 and 18 series, Boeing-Stearman 75, de Havilland DHC-2 and DHC-3, Gee Bee, Grumman G-21 and G-164, Howard DGA-6, -11, -15, North American T-6, and Weatherly 201 and 620.
What Changed
SAFO 15007 introduces awareness of flyweight screw and expander hardware failures due to fatigue, improper modification, and incorrect torqueing during installation. It highlights inspection findings of cracked screws and altered expanders, and clarifies that no FAA-approved procedures exist for removing thread steps or modifying expanders. The document provides specific criteria for replacing screws and expanders to prevent failures.
Why It Matters
This alert is critical for aviation professionals because failure of flyweight screws can cause in-flight engine failures, posing serious safety risks. Operators, mechanics, and repair facilities must ensure proper inspection and replacement of affected parts to maintain engine reliability and comply with FAA safety standards. Understanding these issues helps prevent forced landings and enhances overall flight safety for aircraft powered by these engines.
What To Do
Owners, operators, mechanics, and repair facilities should inspect flyweight screws and expanders during maintenance and overhaul for any signs of thread steps, surface damage, or unauthorized modifications. Replace any screws or expanders that do not meet the specified conditions. Additionally, inspect assemblies during maintenance actions that provide visual access and remove engines from service if abnormalities are found. Use only serviceable parts during overhaul and follow torque specifications precisely.