Lycoming and its service centres have begun installing replacement crankshafts in turbocharged piston engines affected by airworthiness directives that have grounded hundreds of aircraft.

Final certification for production of the new crankshafts was received earlier this month and the company hopes to have all 950 affected TIO-540-series engines repaired by early in the second quarter.

Production and testing processes have been improved to eliminate the weakened "honeycomb" grain structure blamed for a series of crankshaft failures (Flight International, 12-18 November 2002). Embrittlement is believed to have resulted from overheating during treatment after forging.

Lycoming's supplier has switched to press forging of all crankshafts, with automated induction heating and temperature monitoring at the furnace exit.

All replacement crankshafts undergo impact testing and scanning electron microscope analysis. Training, work instructions and quality audits have all been improved, says Lycoming.

More than 600 replacement crankshafts have already been produced on a "risk-release basis" that allowed production to begin ahead of certification. Lycoming and 15 authorised repair centres worldwide are planning to install the replacement crankshafts at a rate of 20-30 engines a day to get the grounded aircraft fleet back in the air by early in the second quarter.

Lycoming parent company Textron last year took a $37 million charge to cover production of replacement crankshafts, shipping, tearing down and rebuilding the engines, and paying for alternative transport for owners of grounded aircraft.

Source: Flight International