Anti-Splat Aero (ASA), maker of after-market parts for experimental aircraft, has issued a service bulletin on their Air-Oil Separator system that many have installed in their aircraft. A recent forced landing of an RV-8 that blew out the crankcase seal due to over pressurization prompted the bulletin, although ASA maintains that most installations are problem free. The ASA system incorporates a vacuum valve that is tapped into the exhaust system to pull a suction on the crankcase breather line. On some aircraft, their exhaust tap is becoming clogged by coking oil residue. If it becomes sufficiently clogged, high crankcase pressure can result, and this can cause oil leakage or seal failure. They are recommending that all installations be inspected for coking at every oil change, and are offering a backup relief valve that can be installed to prevent cranks pressurization should the tap become clogged between inspections. The full text of their service bulletin (posted on the ASA web site) is below. Continue reading "Anti-Splat Aero Issues Service bulletin on Air-Oil Separator"