My club has a Cessna 172R aircraft with a Lycoming IO-360-L2A engine. This is a 180 hp engine which is derated to 160 hp on the 172R by limiting rpm to 2400. The engine has an official TBO of 2000 hours. The Swedish national aviation authority allows 2400 hours before overhaul on commercial ops and 3000 hours on non-commercial ops for aircraft on approved maintenance programmes.
The engine was overhauled in 2015.
At 1500 hours after overhaul, cylinder #4 had to be replaced.
At 2245 hours after overhaul, cylinder #3 had to be replaced.
At 2575 hours after overhaul, cylinder #2 had to be replaced.
At 2650 hours after overhaul, cylinder #1 had to be replaced. The engine was overhauled again at this point.
We have never encountered anything like this before. We regularly run our engines to at least 2400 hours. Another engine of the same type on a Cessna 172S, not derated but giving the full 180 hp, ran to 3400 hours before overhaul. (That aircraft was on an owner-declared maintenance programme. The overhaul was not due to any indications of problems, but because we felt that 3400 was enough.)
So what’s likely to have happened? Did we get a set of bad cylinders in 2015 or is there some problem with the engine installation? The operational profile of the aircraft is no different from that of our other aircraft – a mix of flight training and private flights. The aircraft doesn’t have a CHT indicator.
Should we have gone for an overhaul already when the second cylinder broke at 2245 hours?
We’re the cylinders new or overhauled at the overhaul in 2015?
Would I be correct in that you run them on unleaded fuel?
Airborne_Again wrote:
had to be replaced
Due to what? All of them for the same reason?
Airborne_Again wrote:
The aircraft doesn’t have a CHT indicator.
Might be a good idea to install some data logging CHT and EGT indicators – they are really helpful when trying to monitor an engine’s health. They are pretty cheap now.
Do you know if your mechanic borescoped the cylinders? Many mechanics see 55/80 compression and replace the cylinder. Perhaps your mechanics are a bit more advanced and keeping up with the latest thinking on compression, borescope inspections, and valve lapping.
Bathman wrote:
We’re the cylinders new or overhauled at the overhaul in 2015?
Don’t know, and I’m not sure I can get that documentation now.
Would I be correct in that you run them on unleaded fuel?
Yes, and so do all of our other aircraft. Why would it matter?
Airborne_Again wrote:
This is a 180 hp engine which is derated to 160 hp on the 172R by limiting rpm to 2400
It’s still a high compression 360, just with limited rpm?
LeSving wrote:
It’s still a high compression 360, just with limited rpm?
Exactly: 29"MP will probably result in higher peak ICP (cylinder pressures) at 2400RPM than at 2700 RPM, although BMEP (mean pressure) is the same since 2700/2400*160/180=1. In other words, the engine is run more “oversquare” assuming all else is the same
Do you have another ‘R’ to prove the point? A sample of one cannot really be called of any statistical significance (although you could argue it is a sample of four)…but surely you must have asked around for other R’ models?
Avgas? Cold CHT? Sweden is cold temp territory.
Edit: Never mind. No Avgas.
We have just ordered a factory rebuild engine for our 172s
It had a landing incident with a lower firewall repair and a shockload needed. The insurance was happy to let us upgrade the shockload to a 0 timed engine,
The engine was at app. 2850h. and still going strong.
As I understand the IO360-L2A is considered a strong engine, https://www.avweb.com/ownership/bulletproof-engines-are-there-any/
Cylinder problems like that seems strange. If related to fuel or pilot operation your other aircrafts should have the same problems.
pmh wrote:
If related to fuel or pilot operation your other aircrafts should have the same problems.
Not necessarily if running a high compression 360 on UL91/96 at WOT at low RPM, IMO.
