As I’ve mentioned before, the sweepstakes Debonair had a major overhaul completed in 2007, at Penn Yan Aero. Penn Yan does great work, but the then-owners didn’t fly the airplane much for the next five years. In that period of time they put approximately 28 hours per year on the airplane. Those hours most probably were local flights for currency purposes.
That’s not much time. For much of those five years it was tied down–outside–on a ramp at Hartford’s Brainard Airport. So the oil level sank to the sank to the sump in the crankcase, leaving the camshaft, pistons, valve assembly, wrist pins–the whole top end, in other words, left high, dry, and free of a proective oil coating. Well, maybe it wasn’t exactly dry up there. Condensation must have occurred as humidities and temperatures rose and fell, and the seasons came and went. Obviously, this promotes rust.
Since taking delivery of the airplane, I’ve logged about 36 hours in N75YR’s left seat, on trips to Minnesota (D’Shannon Aviation, for tip tanks, window, and gap seal installation); Kansas; New Mexico (Santa Fe Aero Services, for avionics install); Lakeland (for display at Sun N’ Fun); Newburgh, New York (KD Aviation’s paint shop); Oshkosh (for display at EAA AirVenture); and Batavia, Ohio (for Air Mod’s interior renovation).
In other words, the airplane went from torpor to serious flying. Right before Oshkosh, we had an oil change done, and an oil analysis performed by Blackstone labs at the same time. The numbers–especially for iron–were disturbingly high. Iron particles in the oil represent wear from the cylinders. Aluminum (top end components), chrome (camshaft lobes), copper (bearings and valve guides), and silicon (dirt) were also represented in elevated levels. The high lead readings are from the lead in avgas, and aren’t cause for concern. Blackstone called us to express their interest in the engine’s condition.
A meeting of the minds–Penn Yan and Blackstone–came out with a recommendation to keep flying the airplane, but to change the oil at more frequent intervals. Compressions have been good, by the way, and the engine runs smoothly, puts out rated power, and meets book performance.
This is what happens when a long-still engine comes to life. Deposits work free as moving surfaces are cleaned by fresh oil, and acids and water are eliminated by long periods of combustion.
After Oshkosh, Air Mod changed the oil. It had been seven hours since it was last changed. We were hoping to see lowered particulate levels–and we did! Here is theBlackstone report, showing the results of the two analyses:
So now the plan is to keep flying (look for more cross-country flying in the coming months) and keep quick-changing the oil. We’re also installing an Airwolf spin-on oil filter (the IO-470 has a screen, not a proper oil filter) so that we can better examine the filter for particles. The filter could also help capture any older particles that have been trapped over the years. In effect, we’re flushing the engine’s oil free of contaminants. We hope.
“If I sat on a couch for five years, then got up and went to New Mexico and back, I’d be shaking loose some deposits of my own,” said Bonanza/Debonair guru Adrian Eichorn. Well put. I’ll show the next oil analysis results when the time comes. If the numbers go down, great. If they don’t, we may have to consider another overhaul–an unplanned alternative we hope to avoid.