SPECIAL AIRWORTHINESS INFORMATION BULLETIN
Aircraft Certification Service
Washington, DC
U.S. Department of Transportation
Federal Aviation Administration
NE-08-26 R3

March 31, 2011

This is information only. Recommendations aren’t mandatory.

Introduction

This Revised Special Airworthiness Information Bulletin (SAIB) alerts you, owners, operators, and certificated repair facilities of Lycoming four, six, and eight cylinder reciprocating engines with a Teledyne Continental Motors (TCM) (formerly Bendix) Series D2000 and D3000 Dual Magneto (2 magnetos with a single drive), of the possibility for the magneto to separate from the engine. Several conditions identified could result in separation of the magneto from the engine, which will result in the loss of power. These engines can be identified by the letter “D” in the 4th or 5th character in the engine model’s suffix. This revision updates the Lycoming Service Instruction (SI) No. from 1508B to SI 1508C. All other information remains the same.

Most of the problems have occurred in Lycoming IO-360-A1B6D and IO-360-A3B6D engines installed on Mooney M20J-201 and Cessna 177RG airplanes, although the potential for magneto separation exists on any engine with a TCM Dual Magneto installed. The airworthiness concern is not an unsafe condition that would warrant airworthiness directive (AD) action under Title 14 of the Code of Federal Regulations (14 CFR) part 39.

Background

For various reasons, several incidents of TCM Dual Magnetos separating from Lycoming engines during flight have occurred.

One failure occurred on the first flight after installation of a newly overhauled magneto. The failure occurred due to cracks in the magneto housing mounting flange area that were present as a result of the magneto’s prior operation. During the overhaul process, the overhaul manual only required visual inspection of the magneto.

Another failure mode has been due to the use of the wrong gasket between the magneto and the engine accessory housing. Lycoming SI No. 1508C clearly shows that an acceptable gasket is circular with no part of the gasket able to extend under the magneto clamp. It also shows an unacceptable gasket that can be installed over the studs in the rear accessory case and subsequently captured between the magneto clamp and the accessory housing.

When a gasket is located between the magneto clamp and accessory housing it will compress and in time result in a loose magneto. A loose magneto will result in the magneto clamp wearing into the magneto mounting flange. Ultimately, the flange thickness will be reduced and the flange will fail.

Improper maintenance usually occurs when magneto maintenance is performed in the field and the nuts holding the magneto clamps in position are removed or loosened. When these nuts are reinstalled, new lock washers must be used because lock washers lose their locking ability with repetitive usage. The ability to obtain the proper torque on the nuts securing the magneto clamps or even make them adequately tight depends on the accessibility of the nuts when the engine is installed in the airplane. Magnetos are more accessible on some airplanes than on others and obtaining thecorrect torque is easier. However, on some installations, the working room is limited and the magneto clamping nuts are inaccessible making proper torquing difficult. As stated above, most of the problems have occurred on Lycoming IO-360-A1B6D and IO-360-A3B6D engines installed in Mooney M20J-201 and Cessna 177RG airplanes because of the inaccessibility of the nuts securing the magneto clamps.

Recommendations
  1. Before installing a magneto, check the magneto housing mounting flange for wear and cracks. A worn or cracked flange might subsequently fail, resulting in the magneto separating from the engine. If the flange is worn or cracked, replace the magneto.
  1. Only install the correct gasket, part number (P/N) LW-12681, which is a circular gasket, between the magneto housing mounting flange and the engine accessory housing. Gasket, P/N LW-12681, does not extend over the magneto mounting studs and it must not be installed between the magneto clamps and the engine accessory housing. If a gasket is installed between the magneto clamps and the engine accessory housing, it is the wrong gasket and must be replaced.
  1. Only use the new style magneto clamps, P/N 66M19385.
  1. Each time a magneto clamp is removed, install a new lock washer, P/N STD-475, before re-installing the nut, P/N STD-1410.
  1. Torque the nuts that secure the magneto to the accessory housing using the torque specified in Lycoming SI No. 1508C.
  1. Repetitively inspect the magneto for looseness by attempting to move it by hand at each oil change or within every 50 operating hours time-in-service. If the magneto is loose, visually check the magneto mounting flange for wear and cracks. If no wear or cracks are present, re-torque nuts, P/N STD-1410, as specified in Lycoming SI No. 1508C. If the flange is worn or cracked, replace the magneto.
  1. Repetitively check the torque on the magneto clamp nuts, P/N STD-1410, with a torque wrench at each annual or 100-hour inspection. If the nuts are loose, visually check the magneto mounting flange for wear and cracks. If no wear or cracks are present, re-torque the nuts as specified in Lycoming SI No. 1508C. If the flange is worn or cracked, replace the magneto.
  1. Prior operation of the engine with loose magneto clamps might have caused cracks in the magneto housing mounting flange. We strongly recommend that you ensure that the facility overhauling your magneto has inspected, or will inspect, the magneto housing for cracks by using a form of non-destructive test (NDT). There are no NDT instructions in the current TCM Magneto Overhaul Manual. A documented procedure using a Level III fluorescent penetrant material, as specified in either current version of SAE International Standards Document SAE 2647 or ASTM International Standards Document ASTM 1417, is acceptable. A procedure recommended by TCM is also acceptable. A Qualified Inspector, as specified in FAA Advisory Circular 43-13 or MIL Standard 410, is to perform the fluorescent-penetrant inspection. A qualified FAA Airframe and Powerplant Mechanic may also perform the fluorescent-penetrant inspection.
  1. Refer to Lycoming SI No. 1508C for additional information.
For Further Information Contact

Norm Perenson, Aerospace Engineer, New York Aircraft Certification Office, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: (516) 228-7337; fax: (516) 794-5531; e-mail: norman.perenson@faa.gov.

For Related Service Information Contact

Lycoming Engines, 652 Oliver St, Williamsport, PA 17701; phone: (570) 323-6181; fax: (570) 327-7101; or go to their Web site at: http://www.lycoming.textron.com/support/publications/service-instructions/pdfs/SI1508C.pdf.