Parts shortages and waiting times on engines and props threaten GA?

No delivery date on the cylinders was given.

My understanding from US shops is that years ago cylinders were expensive and welding was commonly done, but prices came down via competition so much less welding is done.

I don’t believe 2024 etc dates. Somebody somewhere is taking the p1ss, otherwise engine builders all over the US would be out of business.

Peter wrote:

otherwise engine builders all over the US would be out of business.

Yes I wonder about this too, and also how any shop could stay in business at all if no parts are available. Having said that, I was just discussing the situation with my shop, and they said they are really having a hard time keeping people flying as a result of the shortages. After initially being agnostic about the Challenger filter, last week they advised it would be a good idea as they were nearly out of filters and unsure when they would get more.

I suspect the answer is the obvious one: US shops are better connected. European shops tend to order from the big European parts distributors. Over here everything is a bit of a struggle; look at this for example.

I visited Barrett Precision some years ago, in Oklahoma. That entire road is nothing but aircraft parts firms. If you want a crank ground you take it 50 yards along the road. If you want crankcases machined, you take them 100 yards down the road. It’s a pretty complete ecosystem.

And shipping an engine to the US is not exactly hard. One writeup is here (disregard those taking the p1ss). It doesn’t help you with just a cylinder though.

How much ‘refurbishment’ can you typically do on a cylinder?

We are overhauling the Continental C-90 in the Vagabond and the engine manual tells us that only one re-bore is permitted, to +0.0015". This surprised me – I had been familiar with re-boring car engines to +0.0020", +0.0030", +0.0040", and finally +0.0060" which was usually the limit. Maybe the cylinder walls, being a standalone part rather than in a block, are very thin – but if I recall correctly the automotive limit was usually due to proximity to coolant passages, which of course the aircraft engine doesn’t have.

We are awaiting measurements but hope to get away with a hone. Then re-grind a couple of the exhaust valves and we should be good.

Aircraft cylinders can be bored once or alternately be built up and bored to standard size. This article lays out some the issues, and why people do different things.

An airport friend who has since moved away had a shelving unit full of C-85 cylInders in various states of decay. If he needed one he sorted through until finding the best of those left, and sent it off for overhaul. Sometimes it came back having failed crack detection and the process started again. He is an A&P working on his own planes and all this was done for small amounts of money. He flew a lot, but his overhauled cylinders didn’t necessarily last a long time after their let’s say fourth overhaul so this occurred regularly for decades Occasionally somebody would give him some run out cylinders and the shelving unit would fill up again.

Typical aircraft cylinders are steel with alu heads screwed on top . So the cylinders have to stand all combustion stresses, unlike car engines with cast iron blocks, well not Porsche 911 cylinders. You better not bore steel cylinders more than specified unless you risk breakage in flight. Welding cracked alu heads is not recommended as these are tired anyway. Alu has a memory , see lifetime limits of airliners and all. So welding tired alu heads is shortsighted B.S. Vic

The situation with structural stress and reboring of aircraft engine cylinders is more analogous to that of a car engine with wet cylinder liners than it is to a monoblock engine with cast in liners that can be rebored several times. With the wet liner engine (e.g. Jag V12, Alfas and Diesels) you replace the liner instead of reboring. It’s not a perfect analogy however as aircraft cylinders unlike both wet liner and air-cooled VW etc engines etc have no through studs to hold the cylinders onto the crankcase – the cylinder itself is in tension.

Re welding aluminum cylinder heads, the issue is achieving the same fatigue strength in the welded area that was in the original cast alloy, as cast the first time. This is the reason for weld procedures, FAA guidance etc. Welding is basically a relatively uncontrolled local casting process that in addition to removing the crack erases the previous fatigue history in the local area. Meanwhile crack propagation at smaller scale continues in other similarly stressed areas on the same part, although it’s often very slow and checking the part for cracks at overhaul is frequently adequate to assure a reasonable service life from that time on. The assessment is based on experience with a given engine, and there is a lot of useful experience with many aircraft engine cylinder head designs. As @Peter points out, this is part of the flexible aircraft engine ‘eco-system’ that gets things done and helps control overhaul cost and availability when it becomes necessary, as it now has.

A factory overhauled O-200 is now 46K.

If thats not a statement that GA is under threat then I don’t know what is.