TBO and be­yond

Pilot - - AIRMAIL - Ed Len­nox, Worces­ter­shire

I’m in the very for­tu­nate po­si­tion to be in charge of man­ag­ing/main­tain­ing a PA-28 that be­longs to an even more for­tu­nate friend of my son. Eigh­teen months ago we had the dreaded news from the en­gi­neer (iron­i­cally at a time when we felt ’XD was run­ning so very well) that there were metal shav­ings in the oil. One new en­gine later, I am pon­der­ing just how long it’s pos­si­ble to run an en­gine be­yond TBO on con­di­tion. Can I en­cour­age read­ers to tell me their ex­pe­ri­ences? What are their se­crets? I of­ten run my cars well be­yond 200,000 miles; at an av­er­age of 40mph, that’s 5,000 hours of oper­a­tion — but in cars it’s rarely the en­gine that’s the rea­son to scrap it. Can you imag­ine chang­ing the oil after ev­ery 50 hours (2,000 miles)? Com­pared to a car we run our en­gines at very low revs and change the oil with amaz­ing reg­u­lar­ity. Maybe us­ing an air­craft for less than 200 hours a year is a prob­lem, but that’s in line with the time an av­er­age car do­ing av­er­age mileage a UK car does an­nu­ally, ap­par­ently. I am thinking that the key rules for longevity and get­ting to TBO and be­yond may be: 1. Al­ways warm the oil to near op­er­at­ing tem­per­a­ture be­fore you en­ter the run­way (we have a rule: run for at least 0.1 on the Hobbs be­fore mov­ing, the min­i­mal cost of the fuel be­ing ab­sorbed into the over­heads) 2. Fly the plane at least ev­ery two weeks for at least half an hour if you can 3. Al­low tem­per­a­tures to sta­bilise be­fore shut down. Is there any more that we can do? Ideas wel­come! I’m de­ter­mined to find out the high­est num­ber of hours flown on a pis­ton en­gine be­fore over­haul and then see if we can ex­tract a sim­i­lar num­ber of hours from ours!

This let­ter was prompted by a re­cent visit to (won­der­ful) Den­ham where I watched a gen­tle­man climb into a rather lovely Bo­nanza which was ap­par­ently on its first flight of the day and he was thun­der­ing down the run­way in less than four min­utes from en­gine start. I won­dered how long that en­gine will last...

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