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what does old worn engine can cause Except power reduce

You will probably notice higher fuel consumption, higher oil consumption, coolant leaks, difficult starting and a rough idle. An old, worn engine is also more at risk of sudden failure by throwing a rod, cracking a piston or cylinder, losing the coolant or oil pumps, etc. Basically if parts are in the yellow and not replaced then your next flight will be gambling whether or not those parts will fail.

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It's just a question if sudden catastrophic failure is even modeled to Core Accusim as it is to some older Accusim. Granted, Core Accusim gives you better gradual wear but B-17 Accusim gave sudden cylinder deaths (be that good or bad feature). I've yet to have to witness any sudden engine damage not related to crashing, nose-over, or other external shock on either Core Accusim craft. In reality, something that appears "green" (in oil pressure, or compression test) can within a fraction of a second to go to "red minus minus". Something like a snapped rod for example, a manufacturing defect that certainly won't be noticed at all in any compression test, nor in oil pressure, nor in engine imbalance, nor in lost power (increased friction, increased heat), nor in metallic particles in the oil... not in anything (aside from possibly a complete engine tear-down)... until a catastrophic failure that can cause a rod to puncture the engine block and at worst kill the whole engine without a seconds notice.

Granted, catastrophic engine failures are damn rare. Aircraft engines are intended to be reliable even compared to car engines and most of us won't experience a sudden engine blow up in our car even during our lifetime.

Well in regards to the rods, failures are often caused by a lack of lubrication seizing the bearings, so perhaps if oil pressure bottoms out this will happen in the modular Accusim?

Usually a catastrophic failure is proceeded by some other damage that may or may not be apparent.

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I have yet to witness any engine damage, period. I've flown the P-40 for 20 hours now and there isn't even any sign of cylinder compression degradation. It's totally fine if that's normal with normal aircraft handling within normal engine parameters, because I have been very good to my P-40. But having witnessed the quite quick degradation of the Spitfire I'm beginning to wonder if it's supposed to be that way.

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Happy Landings
- Patrick

I've flown the P-40B for almost 46 hours and all flights were within the limits. So I've never exceeded max. engine temperatures or used high MP with low RPM. The compression results show 71 for the lowest cylinder. Had to clean all filters at 34 hours and replace worn brakes at 31 hours. At the moment only the generator is shown in yellow.

But I did stress a brand new P-40C with high oil and coolant temperatures, used around 45" of manifold pressure with low RPM and 91 octane grade fuel for some minutes. The was knocking badly.
After landing I had a look at the maintenance hangar. Cylinders were damaged badly. Smooth ground running at around 1000 RPM was impossible due to intense misfiring of different cylinders.

If you run the engine within it's limits, everything is fine.

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"Give me a ping, Vasili. One ping only, please."

The way these engines wear down is quite a harsh curve.

With the early Merlins, you get something along the lines of:
6psi = 100 hrs
12psi = 10 hrs
18psi = 2.5 hrs
25psi = 15 min

Scott.

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A2A Simulations Inc.

Wow, and these are times until overhaul?

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I believe its much worse, going from memory here as me and scott were talking when he first went through the Rolls Royce manuals, but I believe that is life time, so until the engine goes 'pop'

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Correct Lewis,

That is total expected life under "operational" conditions. Peacetime maintenance and operations showed that the figures quoted were a bit harsh but one must remember that a Spitfire had an estimated combat life of 20-30 hours..so an engine that might last 30 hours in total was good enough.

Under the very best peacetime conditions the early Merlins were reckoned to have a 120 hour life before massive overhaul, pretty much replacing everything. At the time the manuals were done, that was a guess..because no Spitfire (or Merlin) had got to that number of hours!! Scott's figures were "hard" numbers, generated from actual running and testing done by RAF.

As a comparison the engine in the S6b (from which the Merlin was developed) had a 5 hour TOTAL life!!



These were not multi-million dollar F16s or Tornados, designed for a 20 year operational career. They were "cheap and cheerful" military aircraft...and plenty more where that came from....


Darryl

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...Some say he never blinks, and that he roams around the woods at night foraging for Merlin parts...

Those Merlin durability numbers could have been tested in a testbench, running a Merlin outside an airframe, using cool water without risk of overheating, and possibly using water injection for higher PSIs, thus limiting sources of damage to mechanical stress, removing heat and detonation from equation. Spitfire mounted Merlins wouldn't be able to run at anything above +6 PSI without overheating, adding more tear to what is theoretical. There's no water-injection. And they're subject to pilot error (low-rpm torquing). Then there's oil contamination, cold starts, rapid heating and cooling during power changes, lack of air filter on non-desert-modded Spitfires. And if they were tested on a testbench, those numbers are probably hours until seizure (zero horse power).

Could probably divide the number by something like 3 or 5 to get a usable engine life. Certainly wouldn't press +6 PSI any more than required. If take-offs are done with +2 and climb at reduced rpm +0 and cruising at somewhere between -4 and +0, then it will probably reach the mentioned 120 hours before it starts to "yellow" on a larger scale. I dunno how's it with A2A damage modeling since I haven't got anywhere as high on operational hours. I got at around 30 but Core Accusim update reset the plane condition to 0 hours (at that point I had overhauled yellow brakes and radiator, nothing else seemed affected).

When babied even Merlin lives long. Allison should live longer, probably, babied or not, I suppose.

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BTW, some Accusim development update or other teaser video mentioned that "some squadrons overboosted these Allisons to over 70" of MP", or something along the lines. Was this just mentioned about Allisons being tortured with such high boosts, or were the Allisons fitted in early P-40? At least none of the variants so far are overboosted and fitted with required water-injection for surviving such high boost, so are we talking about some field-modded variant of early P-40 not yet supplied by A2A? A late P-40? P-38? P-39?

EDIT: HTML to BB-code

I highly doubt the test cells would add water injection just for the purpose of testing since it would make the results irrelevant to the pilots and crew of operational airplanes, the very people such testing would be intended for.

Another thing to note is that RPM is a more important factor in an engine's lifespan than manifold pressure. If you aren't running into detonation or overheating then more revs will kill an engine quicker than sustained high boost. The extremely short lifespans of the aforementioned Merlins at 12 psi and beyond (outside the operational envelope of these engines) is because detonation is literally eating away the pistons and melting the exhaust valves at that point since there is inadequate charge cooling to keep combustion under control.

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The results are irrelevant either way as testbenched Merlin doesn't have same limitations on cooling capacity.

But the results for 18 psi and 25 psi might still be "dry" measurements with RICH RICH fuel mixture. I was just thinking whether it'd be even possible to run Merlin at 25 psi without water injection even for that 15 minutes. Plus, wasn't the stock supercharger on early Merlins only capable of 18 psi at sea level? (Intentionally limited to 12 psi with the drilled holes. And also with a second power limiter (BCO) at 6.5 or 9.0 psi.)

True Whiic.
This was very evident in the early p-40s, espically the ones in the lend/lease program.
American P-40s were a bit more beefed up and could take more punishment.
The flying tigers p-40s all had custom made engines, and had the same superchargers that were used on the spitfires.
There is a lot of speculation as to how chenalt, got his hands on these superchargers....
I have pictures of the engines of some of these planes, you can see where either rods broke thru the sides of the block or they were bullet holes.
The planes did make it back to their base. Aside from that i have no idea if the engines were running upon touchdown....
I once heard of a P-38j that was in Alaska. Years ago, that had been flown from Anchorage, to Seattle with one engine seized, and the other threw a rod....What i heard was the thrown rod engine stayed running untill the pilot powered down to land before it finally gave out....
More research is needed to see if this really happened or not....I will see what i can dig up on this.

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This was covered previously with the Spitfire I release, but it still applies here. One has to remember that the Merlin and Allison V-1710 were built under very different conditions. The Merlin was pressed into service "right now" because the RAF needed them for the Hurricane and Spitfire to fight the Germans. They continuously improved the Merlin engine as the war went along because they got time to test them both in cells and in the airplanes and found what needed to be "fixed" or improved. The Allison V-1710 was built without any such pressure. It was designed to last longer (although not necessarily a lot longer) because peacetime serviceability was a major issue for the USAAC. However, it had its problems as well and experience in service, especially once Lend-Lease started, and improvements/fixes were made as quickly as they could.

Also, it's important to note that even the last versions of the Merlin built for fighters had problems and still do. Rousch has been doing a lot of work recently fixing some of the lingering problems that the Merlins have been presenting to modern operators of the engines like the plating on the cams and the design of the fingers. They've also started manufacturing replacement heads for the engines based off of the "Transport Heads" that were used on aircraft like the DC-4M and Tudor which were beefier and longer lasting, but were heavier (a major concern for wartime fighters, but not really for modern warbirds).

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