Modelling engine wear and WEP limitations

[VO101_Tom]

Originally Posted by Seadog

If you read Dowding's memo carefully:
http://www.spitfireperformance.com/dowding.pdf
he discusses a number of scenarios that result in engine oil starvation and/or overheating. The engines were failing, not just from overuse of 12lb/3000rpm but from overheating and lack of oil pressure. Steep climbs damage the engine from overheating, not overboosting. Inverted flying damages the engine from lack of lubrication not overboosting. Dowding memo is pretty clear: keep your gauges in the black! Yes, Dowding states not to use 12lb boost for more than 5 minutes, but the real culprit is overheating and lack of oil pressure. No sane pilot, in a combat situation, say with a 109 on his tail is going to worry about using 12lb/3000rpm for more than 5 minutes, and Dowding's memo is nothing more than a reminder to not use overboost except when really needed.

I read it, thanks. Sry, this did not convinced me
They would write it if the injury of the bearing would depend on the temperature only. "Be watching the thermometer, and untill not in red, u can make what you want". Unnecessarily would limit their pilots (5 min limit) without reason?

"but the real culprit is overheating and lack of oil pressure." - and the strain of the drive. I believe it you recognise it you too, it takes advantage of everything if you squeeze more strength from the drive. Winch, crank, bearing, axis, gaskets, cooling, lubrication. They call it emergency power (notleistung in 109) because of this.

"No sane pilot, in a combat situation, say with a 109 on his tail is going to worry about using 12lb/3000rpm for more than 5 minutes" - totally agree I would not care about it. But the engine from this probably gets ruined yet. U reach home, or dont, it depends of luck. If u lucky enough, u can show the oil filter to maintenance team, if not... with an airplane less.

The same one is true for the Bf 109 anyway. Invert flying prohibited its oil system, and the increase manifold pressure until time only it may be used (start und notleistung). It is not linked to the temperature there actually, but this unambiguous. Temperature OR the time a limit defines it, till when it may have been used.

What is interesting yet, and I did not know about the fact that the system of the hydraulic propeller is bound to the engine, not separate system: "loss of engine oil pressure (inverted flight, slow rolls) has an effect on the Rotol aircrew in that baldes return to a fine pitch position". This means that he should lose very much from the performance at this time right?

[Crumpp]

At least you've given up on this fantasy notion of a strip inspection after every use.

A complete fiction that only exists in your mind. Feel free to quote me on the requirement for an overhaul.

You don't read what anyone else writes.

Crumpp says:
Change the oil, oil analysis, filter changes, compression check, and over all inspection for cracks/leaks/function would be in order to ensure engine health.

That is about 3 hours worth of work on a Merlin engine. If they check crank bearing tolerances then you can add about an hour to it. If they find something then of course, it will get fixed or replaced.

Once that is done, the mechanic would enter into the logbook the work performed and return the aircraft to service. A few hours in the shop is certainly worth the pilots peace of mind.

http://forum.1cpublishing.eu/showpos...0&postcount=27

[Seadog]

Originally Posted by Crumpp

Quote:
Crumpp says:
Change the oil, oil analysis, filter changes, compression check, and over all inspection for cracks/leaks/function would be in order to ensure engine health.

That is about 3 hours worth of work on a Merlin engine. If they check crank bearing tolerances then you can add about an hour to it. If they find something then of course, it will get fixed or replaced.

Once that is done, the mechanic would enter into the logbook the work performed and return the aircraft to service. A few hours in the shop is certainly worth the pilots peace of mind. [/url]

Crumpp says it. The Merlin engine service manual doesn't. The service manual says check the oil filter after emergency boost, so does Dowding. The rest of what Crump writes is his own fantasy based upon the idea that RAFFC operated on the same lines as civil aviation. The reality is that most combat aircraft were destroyed before their hundred hour checks, and 25-40% of RAFFC pilots died before they achieved 100 hours of combat flying. The Merlin engine could be flown continuously at 12lb boost with a low probability of failure and this engine was cycled 100 times from 4.5 to 12lb/3000rpm and the bearings held up just fine:
http://www.wwiiaircraftperformance.o...bs-14nov39.jpg
without the need for repeated engine checks, since by definition the engine was being cycled multiple times per sortie.

[VO101_Tom]

Originally Posted by Seadog

Crumpp says it. The Merlin engine service manual doesn't. The service manual says check the oil filter after emergency boost, so does Dowding. The rest of what Crump writes is his own fantasy based upon the idea that RAFFC operated on the same lines as civil aviation. The reality is that most combat aircraft were destroyed before their hundred hour checks, and 25-40% of RAFFC pilots died before they achieved 100 hours of combat flying. The Merlin engine could be flown continuously at 12lb boost with a low probability of failure and this engine was cycled 100 times from 4.5 to 12lb/3000rpm and the bearings held up just fine:
http://www.wwiiaircraftperformance.o...bs-14nov39.jpg
without the need for repeated engine checks, since by definition the engine was being cycled multiple times per sortie.

I agree, huge difference is between 5 min and 8 hour, but the engine failure IS exists. If 20% of flight time using 12lbs boost, the engine gets damege certainly. After 50 hour test, this Hurri have cylinder head cooling leak. But you don't know, after how much time got damage. Maybe after 5 minutes, maybe one hour, maybe eight. Maybe its far from 5 min, but also far from "continously without damage". We do not say that the engine has to explode after 5:01 minute. But the problem exists, and it is not possible to leave it out of consideration.

I believe it if you say that a limitation was official onto the machine, but nobody took it seriously. Okay. But this does not mean that it did not have consequences. If you don't want to, you do not deal with it in the game. But let it have consequences. As it is for the other side.

[VO101_Tom]

Yeah I forgot this According to you, what was the purpose that the oil filter was taken out (without an oil change)? What did they make with it? It was thrown in into a big green box, on which was a huge "not interest " stencil?

[Seadog]

Originally Posted by VO101_Tom

I After 50 hour test, this Hurri have cylinder head cooling leak. But you don't know, after how much time got damage. .

The early Merlin engines were prone to cylinder head leaks, as per the memo, and this had little or nothing to do with 12lb boost. WW2 combat engines had a short service life, by civil aviation standards, and, as I have pointed out most aircraft and engines never survived past 100 hours.

Originally Posted by VO101_Tom

Yeah I forgot this According to you, what was the purpose that the oil filter was taken out (without an oil change)? What did they make with it? It was thrown in into a big green box, on which was a huge "not interest " stencil?

They would examine the filter for evidence of metal filings which typically indicated bearing damage. No metal = no need for further investigation. Obviuosly the engine flown for 49.5 hours with repeated cycling of 12 and 4.5lb boost never showed evidence of bearing damage, or they would have stopped the trial.

[TomcatViP]

Originally Posted by Seadog

The early Merlin engines were prone to cylinder head leaks, as per the memo, and this had little or nothing to do with 12lb boost. WW2 combat engines had a short service life, by civil aviation standards, and, as I have pointed out most aircraft and engines never survived past 100 hours.




They would examine the filter for evidence of metal filings which typically indicated bearing damage. No metal = no need for further investigation. Obviuosly the engine flown for 49.5 hours with repeated cycling of 12 and 4.5lb boost never showed evidence of bearing damage, or they would have stopped the trial.

Man engine and airplane are strategical assets in a war. Not so much men This why you've got disciplinary council and your superior makes good or bad report on your behavior. This was not paparazzi on look. Think that the logistical bckgrd to sustain a full air-force at war was simply enormous. You don't want to change an eng because some fighter jock only wanted to buzz Lili's home.

May I remind you the late war LW with thousands of a/c build each month but with only hundreds on the fronts?

Even in the late war Tempy the Emergency power had a restricting safety link.

The Spitfire during BoB was a wonderful aircraft, potent, powerful and survivable. That's it.

[Blackdog_kt]

Originally Posted by Seadog

Crumpp says it. The Merlin engine service manual doesn't. The service manual says check the oil filter after emergency boost, so does Dowding. The rest of what Crump writes is his own fantasy based upon the idea that RAFFC operated on the same lines as civil aviation. The reality is that most combat aircraft were destroyed before their hundred hour checks, and 25-40% of RAFFC pilots died before they achieved 100 hours of combat flying. The Merlin engine could be flown continuously at 12lb boost with a low probability of failure and this engine was cycled 100 times from 4.5 to 12lb/3000rpm and the bearings held up just fine:
http://www.wwiiaircraftperformance.o...bs-14nov39.jpg
without the need for repeated engine checks, since by definition the engine was being cycled multiple times per sortie.

Sorry, but the fact that you claim continuous running on what's called emergency power and then try to support it with the argument that most planes would be destroyed pretty fast anyway, makes it all sound like an effort to disguise the fact that if the aircraft survived long enough they would get a higher proportion of engine failures.

It would be more accurate to phrase this a bit differently: engine failures were rare not because WEP was free of charge, but because the aircraft rarely survived long enough for the engine abuse to take effect.

Like i said before, they wouldn't call it emergency power if it was fine to use it all day long and fuel burn was the only real drawback. They would just call it full power and insert a footnote "warning, it burns fuel really fast".

Emergency has a pretty strong connotation to it, it means "don't use unless you're about to die" in simple terms.

And finally, this is not a thread about what the Merlin could or couldn't do. This is a thread about modeling engine limitations on ANY kind of engine in the sim if it also had them in reality. If the Merlin did or didn't have such restrictions is a completely different matter and totally out of the scope of this thread. What are doing here is this:
"Supposing engine X has limitation Y, what's the best way to have this reflected in the sim?"

Why do you feel the need to constantly hijack this thread in the direction of the Merlin specifically is completely beyond me, especially when you can just as easily start your own thread and argue your point there without dragging this one completely off-topic.

We are not discussing the capabilities of a specific engine here, we are discussing a proposed idea for a game feature. If you want the Merlin to be exempt from it, feel free to start a separate thread about it or use one of the many already provided. We don't need every single thread around here to revolve around the Merlin and the use of 100 octane fuel, there's several of them already

Excuse me the bolded text, i mean no hostility and it's purely for emphasis. It's just getting mighty tiresome trying to discuss an interesting idea with some like-minded fellows in the pub and having someone from across the bar constantly jump in the middle of your group shouting "AHA" as he dumps a load of old musty dossiers and charts on the table before he starts on something that has almost nothing to do with the discussion at hand. Don't drive us out of the pub man, especially when there are people having the kind of discussion you prefer just two tables over

[Seadog]

Originally Posted by Blackdog_kt

And finally, this is not a thread about what the Merlin could or couldn't do. This is a thread about modeling engine limitations on ANY kind of engine in the sim if it also had them in reality. If the Merlin did or didn't have such restrictions is a completely different matter and totally out of the scope of this thread. What are doing here is this:
"Supposing engine X has limitation Y, what's the best way to have this reflected in the sim?"

Why do you feel the need...

[b2]We are not discussing the capabilities of a specific engine here, [/b]

Excuse me the bolded text,

b) establishing an engine's limitations is a prior requirement before you can sim it. There must be others who can comment on the DB engine's reliability and reliability with WEP. Until these limits are discussed, how can you create a sim based upon RL?

I am not hijacking the thread, when I discuss engine limitations, or the mathematics and probabilities of engine failure versus average service life: These are the essential factors that have to be modelled but if engine life with repeated overboost works out to be greater than the average life of an aircraft, then the use of overboost is probably extending the average life, rather than shortening it.

b2: Indeed not, but no one is presenting info on Luftwaffe engines. I wish they would.

I suspect that those familiar with the Me109 for example, are well aware that the use of a properly modelled WEP while flying over London, will probably mean a long swim somewhere in the English Channel, and thus fuel considerations are probably a primary factor in limiting the use of 1.3/1.4 ATA in the 109, while flying over Britain, and while this is less a worry for RAF pilots it is still very much a factor when fuel consumption rises to ~105gph for the Merlin III at 12lb/3000rpm.

Originally Posted by Blackdog_kt

It would be more accurate to phrase this a bit differently: engine failures were rare not because WEP was free of charge, but because the aircraft rarely survived long enough for the engine abuse to take effect.

OK. Now how to sim that?