Service Bulletin No. 505 B

Inspection of Crankshaft I.D. for Corrosion


Supersedes Service Bulletin No. 505A

December 1, 1997


The following Textron Lycoming four cylinder engines which utilize fixed pitch propellers except those installed in rotary wing aircraft or new engines shipped after February 15,1997:

All 320 series engines; and

All 180 horsepower, 360 series engines except the O-360-A4A, -A4D, A4G, - A4J, -A4K, -A4M, -A4N, -A4P -C4F, -C4P, IO-360-L2A and AEIO-360-B4A engine models.


Uncoated Crankshafts (no "PID" stamped on flange OD, see Figure 1)

A. Initial Inspections:

For new, rebuilt and overhauled engines shipped from Textron Lycoming prior to and including 1984, the initial inspection must be conducted within the next 200 hours of operation or 1 year from date of this Service Bulletin, whichever occurs first.

For new, rebuilt and overhauled engines shipped from Textron Lycoming after 1984, the initial inspection must be conducted at the next overhaul or engine disassembly or within 10 years of the original ship date, whichever comes first.

B. Subsequent Inspections:

1. Serviceable Crankshaft having no corrosion pits. The inspection must be repeated at each engine disassembly until overhaul and the time interval between each inspection must not exceed 5 years.

2. Pitted Crankshafts. Fluorescent Penetrant Inspections are required every 100 hours of operation or each year whichever occurs first until the crankshaft is replaced at overhaul or earlier at the owner's discretion, not to exceed 12 years. 

As more experience has been gained with aging engines, it is obvious that calendar time and frequency of use are important factors of service life. With age, the effects of corrosion can result in structural problems for engine components. Reports of crankshaft breakage originating from corrosion pits on the inside wall immediately aft of the pilot diameter have been received for fixed pitch propeller aircraft. To preclude the occurrence, this area must be inspected in the manner specified in Section I.

Get It Exchanged

Use our Engine Exchange Program to order a new, rebuilt, or overhauled engine to experience more airtime and less downtime.