Owners of more than 300 Cessna 172R Skyhawks delivered since shipments restarted in January 1997 have been ordered to replace the exhaust silencers. The US Federal Aviation Administration issued an airworthiness directive (AD) on 13 January mandating replacement of the silencers, made by Aeroquip, because of leaking welds.
The FAA issued a similar AD on 30 December, requiring replacement of Aeroquip-manufactured silencers on 19 182SSkylanes. Both directives are intended to eliminate the risk that a leaking silencer could allow carbon monoxide into the cabin heater.
A cracked weld was noticed in 1997 during a 182 ferry flight, leading to discovery of exhaust-system problems on Skylanes on the production line. Pressure tests revealed a 70% failure rate, with leaks at or around welds. Tests on Skyhawk silencers also revealed an unacceptably high failure rate. Aeroquip is delivering new silencers.
Skylane owners were required to replace the silencers before resuming flights. Skyhawk owners can fly their aircraft, provided the heater is rendered inoperative, until a new silencer is available.
Source: Flight International
