This is a real hot topic and there’s two schools of thought on it. You understand I’m biased in the matter for obvious reasons but here’s my best shot at giving you unadulterated info to make a decision.
Flying past TBO is considered safe by many. According to engine shops, some engines are more likely to last longer than others with some flying 4,000 hours without major repair. There’s a lot of discussion about whether TBO recommendations are necessary or arbitrary. Some pilots have received advice from mechanics to continue flying until they experience excessive oil consumption or metal fragments after an oil change. If you’re not checking for metal fragments, you better start – especially if you subscribe to this school of thought.
If you want to join the crowd flying past TBO, consider the following:
- You are intentionally going against your recommended maintenance schedule. If you have an incident or accident, any prosecuting attorney will capitalize on this as ‘negligence’. It’s potentially a huge liability. Here’s an example of the NTSB faulting an aircraft owner for not complying with his recommended overhaul schedule. If this pilot had hurt anything other than marsh land, he would have been toast in court. Which brings me to the next point.
- Will your insurance policy cover an operation that doesn’t follow recommended maintenance procedures? You may not want to ask your agent…
- Are you going to find a shop to sign off your annual inspection if your engine is past TBO? There’s a lot of shops that won’t for liability reasons.
- How would you feel if something happened? Was you decision based on money, or did you really feel it was safe?
I see a lot of people who subscribe to the Mike Busch point of view that engines should be overhauled on condition, not on time. There might be some validity to this, but we have to consider Mike’s bias in the matter the same way we considered mine. He owns Savvy Aircraft Maintenance which collects $500-1000/year from aircraft owners and then offsets that cost mainly by deferring maintenance. So if there was evidence out there which proved that it wasn’t safe to fly past TBO, he’d be the last to find it. I’ve seen other expert opinions that contradict his points of view, but Mike’s are by far more popular. After all, your wallet is motivated to believe him.
There’s no evidence to prove definitively that flying past TBO is safe or unsafe. But we know a couple of things for sure:
- The liability is a real risk
- Some insurance policies don’t cover operation past TBO
- Some mechanics won’t sign an annual past TBO
- Engines don’t last forever and the longer you fly, the less likely you’ll be able to reuse expensive parts like a crankcase. This could eat any savings
- Overhauling your engine adds value to the plane and can be financed in many cases
- Some engines are more likely than others to run longer past TBO
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