Tuesday, March 20, 2012

2012 Annual Inspection (ii)

This morning I stopped by the hangar to visit N631S, collect the various loose items for storage, and see how the inspection was progressing.
Before anything was taken apart, Mike the IA did a pre-maintenance run-up and found no discrepancies. The airplane is decowled, the old oil drained, and the main gear fairings are off. The upper spark plugs have been pulled; they look good. Work continues on opening the inspection covers and removing the interior.

The results of the engine's cylinder leakdown check (i.e., the "compression test") look quite nice. Mike checked the cylinders for leakage as instructed by TCM Service Bulletin SB03-3. Last year, one cylinder, #2, was not very tight. It tested at 48/80 psi on a day when the minimum acceptable value based on the standard orifice was 46/80. This year, on a day where the minimum acceptable value was 48 psi, it performed better. From the logs, here are the compression values at each annual inspection since 2007 (charted below):

Obviously, cylinders #2 and #4 were having a much better day this year than in 2011. N631S's engine is now at 1567.4 hours since its last major overhaul and oil consumption never exceeds 2 quarts during each 50 hour oil change interval. I anticipate that no surprises will arise from spectrographic analysis of the used oil, or from the visual inspection of the filter media or from the borescope inspection of the cylinder interiors. It looks to be a healthy engine and there appears to be every chance that it will happily run well beyond the nominal 2000 hour TBO period...at least I hope so!

As usual, I'll be stopping at the hangar tomorrow morning to see what items of interest Mike has found today.


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