Air Orlando Aviation Maintenance LLC

23 February 2010 Comments Re: Proposed AD, Piper Aircraft, Inc, Docket No. FAA-2010-0122 1. Preamble page 4 of 5, 7th paragraph, states in part, “This proposed AD would require replacing any spot weld V-band exhaust coupling with a riveted V-band coupling.” In checking with Lycoming, I found that only the one coupling, P/N 40D23255-340M (40D21162-340M) has been re-designed with rivets. All the other P/N’s couplings remain spot welded. Reference, Bart Kinley, Field Service Engineer, Lycoming Engines, @ 570-327-7064. 2. I feel that the AD, as proposed, really does not go far enough to correctly address the problem. Most of the broken couplings appear to break at the band, not spot welds. This spot welded type of coupling has been in service in automotive diesel as well as aircraft for many years and if installed correctly appears to provide excellent service. Inspection of aircraft failures have shown that the failed coupling was accompanied by (either / or) mis-aligned exhaust components, seized slip joints and over torqued couplings. My policy is to remove the entire exhaust system to insure slip joint movement and therefore correct alignment (as the engine expands)at 200 to 300 hr intervals. Normal slip joint movement due to expansion usually shows to be 3/32 to 1/8 in. during normal operation and allows correct alignment to be maintained to reduce stress on the couplings. 3. Lycoming SI 1238B, covers the installation procedure for the couplings as well as torque procedures. SI 1448 cover the exhaust installation in detail with call outs for the correct parts and part placement. I feel that incorporation of these two SI’s as well as the requirement to free all slip joints would enable the system to be installed and aligned correctly and would assist in correcting the issue. Sincerely: Gerald N Stroum, 2674633 IA D.O.M. Air Orlando Aviation Maintenance, LLC 407.228.4436 // maintenanceaoa@bellsouth.net