SAIB CE-06-33

SPECIAL AIRWORTHINESS

INFORMATION BULLETIN

Aircraft Certification Service Washington, DC

U.S. Department of Transportation Federal Aviation Administration

CE-06-33 March 17, 2006 http://www.faa.gov/aircraft/safety/alerts/SAIB This is information only. Recommendations aren’t mandatory.

Introduction

This Special Airworthiness Information Bulletin (SAIB) alerts you, repair stations and mechanics holding Inspection Authorization (IA), of service difficulties and safety issues associated with certain Marvel Schebler /Precision Airmotive float type carburetors.

Background

We have received several reports of poor idle cut-off or of fuel leaking from the carburetor after shutdown. The conditions reported were the result of fuel leaking into the carburetor float, a damaged or worn float, or a damaged or worn float valve. Since this condition, if uncorrected, can lead to in-flight fire or loss of power due to an overly rich fuel mixture, we are issuing this SAIB to assure timely dissemination of this information to maintenance personnel. While such issues are not new or specific to any particular carburetor float design, it is possible that mechanics and operators with little or no exposure to carburetors could fail to recognize the potential cause and possible effects of such conditions.

Precision Airmotive LLC has issued Service Letter (SL) SIL MS-12, dated February 24, 2006, to provide information regarding these problems.

Recommendation

• OPERATOR ACTION: Operators of aircraft equipped with float type carburetors should be aware of the potential for these conditions to exist and should immediately remove an aircraft from service if fuel leakage or poor idle cut-off are evident. The operator should have qualified maintenance personnel inspect the aircraft prior to return to service.

• MAINTENANCE ACTION:

Mechanics addressing these issues should inspect the carburetor for signs of fuel leakage. This may be evidenced by fuel stains from the bowl vents in the throat of the carburetor and/or fuel in the air box. Remove carburetors with signs of fuel leakage and send them to a qualified repair station for inspection and repair.

• We also recommend that the carburetor be overhauled or replaced at each engine overhaul.

NOTE: Fuel leakage after shutdown is also known to occur on certain engines running on automobile gasoline. If inspection of the carburetor on these engines reveals no discrepancies, switching back to avgas may resolve the issue.

2 Refer to Precision Airmotive Service Information Letter SIL MS-12 dated February 24, 2006 for complete details regarding this problem.

For Further Information Contact

Richard Simonson, Seattle Aircraft Certification Office, 1601 Lind Ave SW, Renton WA 98055; telephone (425) 917-6507;

fax (425) 917-6590; e-mail:

richard.simonson@faa.gov

Precision Airmotive LLC, 14800 40th Avenue NE, Marysville WA 98271; download the SL at www.precisionairmotive.com