The National Transportation Safety Board said Thursday that oil leaks from aftermarket oil filter adapters have led to at least 11 general aviation accidents since 2004.
The NTSB called on the Federal Aviation Administration to issue an airworthiness directive to address an unsafe condition associated with oil filter adapters installed through a supplemental type certificate on Continental engines. Oil leaks from these oil filter adapters can lead to a loss of engine power if not properly installed or maintained.
After uncovering the safety issue during its investigation of two crashes in 2019, the NTSB identified nine other accidents between 2004 and 2018 in which airplanes equipped with these adapters had a loss of engine power. These accidents resulted in three fatalities and five serious injuries.
The oil filter adapter, originally manufactured by F&M Enterprises from 1996 to 2015, and now manufactured by Stratus Tools Technologies, is an after-market product that can be installed on certain models of engines; it allows owners and operators to use a conventional spin-on oil filter in place of the brass screen on the original engines. Both F&M and Stratus oil filter adapters are affected by this safety issue.
Torn and unevenly compressed gaskets and loose adapters are among the safety issues the NTSB identified in the 11 accidents. In response to these problems and other reports of oil leaks, Stratus issued a service bulletin in October 2019 to instruct mechanics on how to install and maintain F&M and Stratus oil filter adapters and to advise owners on how often they need to be inspected.
Because compliance with service bulletins is not mandatory for Part 91 operators, the NTSB is asking the FAA to issue an Airworthiness Directive to require owners of airplanes equipped with an F&M or Stratus oil filter adapter to repetitively inspect, and if necessary, reinstall the adapter to bring it in compliance with the service bulletin.
The advisory to mechanics, airplane owners and operators is available at https://go.usa.gov/x7t3q.
The complete six-page safety recommendation report is available at https://go.usa.gov/x7tqm.