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Regulatory Brief -- Lycoming highlights "potential metallurgical condition" on -360 series crankshaftsRegulatory Brief -- Lycoming highlights "potential metallurgical condition" on -360 series crankshafts

Regulatory Brief

Lycoming highlights "potential metallurgical condition" on -360 series crankshafts

The issue:

Textron Lycoming Service Bulletin No. 549 "mandates" nondestructive testing of crankshafts installed in -360 series airplanes or shipped as spare parts. The SB states that a "potential metallurgical condition" may exist on 4-cylinder crankshafts shipped from the factory between May 1, 1997 and April 30, 2000.

The importance to our members:

Lycoming SB No. 549 lists 1160 affected crankshafts. Per the SB, warranty coverage for the SB's required inspection will be extended only through October 31, 2001. Inspections must be conducted by one of a number of Lycoming certified facilities listed in the SB.

Significant provisions:

  • Lycoming SB No. 549 affects only 4-cylinder crankshafts in -360 series engines.
  • If any -360 series engine has had the crankshaft replaced after May 1, 1997, with a crankshaft shipped from the factory as spares between May 1, 1997 and April 30, 2000 then the crankshaft inspection is required.
  • Affected engines/crankshafts and Lycoming approved testing facilities are listed in the SB (attached below).
  • Testing must be completed at one of the listed Lycoming approved testing facilities, and must be completed within the next 100 hours time in service or 180 days from the date of the Service Bulletin.
  • Lycoming will terminate warranty coverage for costs associated with compliance with the inspections required by SB No. 549 on October 31, 2001.
  • According to Lycoming officials, the "metallurgical condition" affecting -360 series crankshafts is not in any way related to the metallurgical problems that affected Teledyne Continental (TCM) crankshafts in 2000. Lycoming reportedly does not utilize the same vendor as TCM for the steel used to manufacture their crankshafts.
  • Lycoming reports that the metallurgical condition resulted when a very small number of crankshafts missed a critical heat-treating process at their vendor's foundry. Reportedly, the condition affects only an extremely small portion of -360 crankshafts, although the deficient parts are likely scattered throughout a large number of crankshafts in the field.
  • Textron Lycoming has trained a large number of facilities worldwide (listed in the SB) to conduct nondestructive testing of the crankshafts. At facilities where large numbers of affected airplanes are expected, Lycoming has installed eddy current testing equipment. Testing facilities with lower expected volume have been trained to conduct a simple micro etching process to determine the material composition of the crankshaft. Both methods can be conducted while the engine remains on the aircraft, and both methods are reported to be equally accurate.
  • According to factory representatives, Lycoming will extend warranty credit to cover the cost of any repairs/replacements necessary should a crankshaft fail the metallurgical inspection.

AOPA position:

AOPA recognizes that metallurgical deficiencies in crankshaft material can ultimately lead to catastrophic consequences. AOPA is concerned, however, over the availability of replacement parts, the adverse impact of aircraft downtime that will inevitably result from a parts shortage, and the ability for certified testing facilities to complete the inspections prior to Lycoming's October 31 warranty coverage deadline. AOPA has been in contact with Lycoming officials regarding these issues and will continue to press for reasonable resolution.


On March 23, 2001, Textron Lycoming published Service Bulletin No. 549.

Related documents:

Textron Lycoming Service Bulletin No. 549, March 23, 2001 (requires Adobe Reader)