Cracked Spark Plugs Prompt Bulletin
Tornado Alley Turbo has issued a mandatory service bulletin (PDF) and asked the FAA to issue an airworthiness directive for the owners of up to 950 Cirrus SR22TN aircraft that may have Champion RHB32S fine wire spark plugs, TAT is sounding the alarm and can only include the aircraft with which it is directly involved in its MSB and the proposed AD. However, the list of affected aircraft could grow to include other aircraft with those plugs installed. TAT says it has been gathering evidence that indicates those plugs are experiencing an unusually high rate of cracked ceramic insulators. Cracked insulators can cause detonation problems that can result in severe engine damage. TAT says it's aware of at least two forced landings and one non-injury accident that may have been caused by the damaged spark plugs. TAT President George Braly said that while the initial MSB applies only to turbonormalized Cirruses, TAT systems have been installed in other aircraft types and he expects action on those, too.
"We have been collecting data and researching this situation very closely. The time has come to deal with this continuing operational safety matter in a definitive manner," Braly said. "Therefore, it is our recommendation that pilots and operators of aircraft with one of the TAT TN turbo normalizing systems installed should not wait for the subsequent airframe model specific service bulletins to be issued." The cracked plugs have also been found in normally aspirated engines, which means the issue may not be limited to turbo-equipped aircraft.