DCS: Spitfire Mk LF IXc Discussion

[Crumpp]

5 minutes is simply a guarantee, beyond which the manufacturer is absolved of responsibility, it does not mean the engine will fail promptly at 5:01.

 

It is more likely to fail at 10 seconds.

 

Basically, some folks want to be able to ignore the airplanes limitations.

 

Ask ED if they will model it that way for you!

[bongodriver]

It is more likely to fail at 10 seconds.

 

Basically, some folks want to be able to ignore the airplanes limitations.

 

Ask ED if they will model it that way for you!

 

No, it could fail after 10, 15 minutes or 10 seconds, it will be completely random, 5 minutes is simply meant to be a safe guaranteed time limit.

 

Nobody wants to ignore limits.

[Crumpp]

Honestly,

 

 

Take your frustration out on Rolls Royce or the RAF...

 

They are the ones who set the limit. Complain to them if you do not like it. :thumbup:

[Friedrich-4B]

Attached is the entire Lovesey article on the development of the Rolls-Royce Merlin.

In addition, Crumpp didn't provide "illustration 27" (Fig. 27) which shows that by September 1943, 395 hours was used on developing the Merlin 66 itself into a more durable engine than the one that first appeared in mid-1942.

 

 

It is more likely to fail at 10 seconds.

 

Basically, some folks want to be able to ignore the airplanes limitations.

 

Ask ED if they will model it that way for you!

 

Hopefully, Crumpp doesn't expect ED to model their engines to automatically fail at 5 minutes & 10 seconds! It is highly unlikely that a properly maintained Merlin would choose to die if run at +18 or +25 pounds for a few seconds longer than 5 minutes; as all the testing highlighted by Crumpp shows, by November 1943 Merlins were being run in overboost for 100 hours with no signs of component failure.

 

The fact is that most combat situations lasted for seconds, and few pilots would have been forced to operate their engines at such high boost pressures for even one minute, unless in a dire emergency.

 

For some reason "secure an adequate margin" was not highlighted in (iii).:sly:

There are no reference sources given from where the documentation posted came from either.

 

(iii) is an extract from A.P 2095 Pilot's Notes General: Part II Engines and Propellers; Note A. Engine Limitations (see below)

 

 

Paragraphs i(b) and ii of 3. Duration and Flight Condition Limits of Use state

 

 

thus, in para ii, pilots were given a degree of flexibility during combat or in emergency situations. ED should model their Merlin 66 accordingly.

Edited November 8, 2015 by Friedrich-4/B
Note A.

[Crumpp]

 

thus, in para ii, pilots were given a degree of flexibility during combat or in emergency situations. ED should model their Merlin 66 accordingly.

 

Absolutely!!

 

Model it just as it was in reality! Who cares about time limits some Ol silly engineer set!

 

 

 

:megalol:

[Yo-Yo]

Ok, and this is the way how we have it in DCS now. The reliability of the simulated engine is designed to have good probability to return home after 5 minutes of WEP. Not to complete mission pressing ESC but to fly home for several hundreds of miles and land.

You can really disregard this 5 minutes if you do not overheat the engine (degraded lubrication due to low viscosity, improper parts clearance, etc, will make the failure closer to you).

Anyway, if this 5 minutes limit is diregarded a kind of Russian roulette begins.

[Crumpp]

Thanks Yo-Yo!

[Crumpp]

Thanks Yo Yo, that's exactly as it should be.

 

Nothing Special for any of the engines....

 

As it should be!

[Friedrich-4B]

 

 

 

This highlights how much more developed and tougher the Merlin 66 of 1943-45 was than the Merlin II/III of 1940 (noting that the 66 ran on a 30/70% mix of glycol and water rather than the 100% glycol of the II/III): it also effectively illustrates how the pressure of wartime experience and development can lead to a much better aero engine.

[Crumpp]

Yo-Yo says:

You can really disregard this 5 minutes if you do not overheat the engine (degraded lubrication due to low viscosity, improper parts clearance, etc, will make the failure closer to you).

'

 

I think this is a great way to get players to realistically think about engine management.

 

Does the model allow for overcooling?

 

Over-cooling is very hard on the engine and will cause premature failures as well. Oil should be hot enough to get rid of water/contaminants that collect in the crankcase during non-operational periods but cool enough not break down the lubricant properties.

[bongodriver]

Honestly,

 

 

Take your frustration out on Rolls Royce or the RAF...

 

They are the ones who set the limit. Complain to them if you do not like it. :thumbup:

 

No frustration really, I'm perfectly at ease with the way the real world works, I know how and why these limits are set.

 

Ok, and this is the way how we have it in DCS now. The reliability of the simulated engine is designed to have good probability to return home after 5 minutes of WEP. Not to complete mission pressing ESC but to fly home for several hundreds of miles and land.

You can really disregard this 5 minutes if you do not overheat the engine (degraded lubrication due to low viscosity, improper parts clearance, etc, will make the failure closer to you).

Anyway, if this 5 minutes limit is diregarded a kind of Russian roulette begins.

 

Yep, just like I said, 5 minutes guaranteed and beyond that you take your chances.....just keep watching those temps.

Edited November 8, 2015 by bongodriver

[MiloMorai]

You can really disregard this 5 minutes if you do not overheat the engine (degraded lubrication due to low viscosity, improper parts clearance, etc, will make the failure closer to you).

Anyway, if this 5 minutes limit is diregarded a kind of Russian roulette begins.

 

The bold text can be ignored as the manufacture defects of the Fw190D-9 and Bf109K-4 are not modeled.

 

Crumpp says: Over-cooling is very hard on the engine and will cause premature failures as well. Oil should be hot enough to get rid of water/contaminants that collect in the crankcase during non-operational periods but cool enough not break down the lubricant properties.

Start up and warm up should get rid of any water/contaminants.

[Crumpp]

Start up and warm up should get rid of any water/contaminants.

 

No

 

Lie #6:

The cooler the engine's oil and cylinder head temperatures, the better.

 

It turns out that the "cooler is better" notion isn't quite right. While excessively high temperatures are bad for your engine, low temperatures are no great shakes, either.

 

On the other hand, oil temperatures lower than 170°F or so on the gauge present a different problem...namely, that the oil is probably not reaching the boiling point of water at the hottest point in its travel. Why is this important? Every time we shut down the engine, a slug of water condenses inside the cooling engine and runs down into the oil sump.

 

https://www.backcountrypilot.org/forum/oil-temp-too-cold-what-to-do-update-problem-solved-14137

[Crumpp]

This highlights how much more developed and tougher the Merlin 66 of 1943-45 was than the Merlin II/III of 1940 (noting that the 66 ran on a 30/70% mix of glycol and water rather than the 100% glycol of the II/III):

 

I am curious as to why you would think the higher cooling requirements of the Merlin 66 means it is more reliable?

[NineLine]

Guys, I am so sick of the same old crap. Discuss the ED module, or go to another forum and carry on your schoolyard cyber fights... nothing here is doing anything for an unreleased module...

[Friedrich-4B]

....You can really disregard this 5 minutes if you do not overheat the engine (degraded lubrication due to low viscosity, improper parts clearance, etc, will make the failure closer to you).

Anyway, if this 5 minutes limit is diregarded a kind of Russian roulette begins.

 

:thumbup: From Pilot's Notes General (2nd Edn, 1943)

 

[Yo-Yo]

'

 

I think this is a great way to get players to realistically think about engine management.

 

Does the model allow for overcooling?

 

Over-cooling is very hard on the engine and will cause premature failures as well. Oil should be hot enough to get rid of water/contaminants that collect in the crankcase during non-operational periods but cool enough not break down the lubricant properties.

 

Yes, both over- and under-cooling lead to improper lubrication in the model and it's very easy to kill the engine running it at full steam especially in cold weather, Especially overrevving it... cold oil makes prop regulator more sluggish, so it's very easy to overrev the engine.

[Kurfürst]

Yes, both over- and under-cooling lead to improper lubrication in the model and it's very easy to kill the engine running it at full steam especially in cold weather, Especially overrevving it... cold oil makes prop regulator more sluggish, so it's very easy to overrev the engine.

 

The amount of detail put into the engine model... simply staggering! :thumbup:

 

I suppose electric pitch regulators are free of this problem (maybe effected by battery voltage dropping in cold wheater)? But hey, electrics tended to be slower.

Edited November 9, 2015 by Kurfürst

[Talisman_VR]

5 minutes seems pretty clear. If you want to take your airplane beyond the limitations, feel free to do it.

 

Yes, the 5 minutes bit is clear, but putting this information in the context of real world practical use, it begs the question, is that only 5 minutes ever for the life of the engine, or 5 minutes in every 10 minutes, or 5 minutes per sortie, or 5 minutes between engine overhauls? What is your interpretation?

 

I suggest that the pilot notes and other associated guidance was written with the knowledge that the engines would actually perform for longer than the printed limitations and aimed to allow a degree of discretion on behalf of the pilot in an operational combat situation.

 

Happy landings,

 

Talisman

[Friedrich-4B]

Yes, both over- and under-cooling lead to improper lubrication in the model and it's very easy to kill the engine running it at full steam especially in cold weather, Especially overrevving it... cold oil makes prop regulator more sluggish, so it's very easy to overrev the engine.

 

What sorts of conditions and what sort of engine handling in DCS could promote over-cooling?

 

I suggest that the pilot notes and other associated guidance was written with the knowledge that the engines would actually perform for longer than the printed limitations and aimed to allow a degree of discretion on behalf of the pilot in an operational combat situation.

 

Happy landings,

 

Talisman

 

Dead right; as noted here the Pilot's Notes General make it clear that the pilot had some discretion during combat or emergencies.

 

NB: A.P. 2095 "Pilot's Notes General" were issued to RAF pilots along with the Pilot's Notes on specific aircraft types - attached are some pages from Part II: Engines and Propellers

 

[klem]

Ok, and this is the way how we have it in DCS now. The reliability of the simulated engine is designed to have good probability to return home after 5 minutes of WEP. Not to complete mission pressing ESC but to fly home for several hundreds of miles and land.

You can really disregard this 5 minutes if you do not overheat the engine (degraded lubrication due to low viscosity, improper parts clearance, etc, will make the failure closer to you).

Anyway, if this 5 minutes limit is diregarded a kind of Russian roulette begins.

 

Thanks Yo-Yo. The fixation on the 5 minute guideline has caused more irrelevant arguments than I can count.

 

If BCO is operated and historical records show that overheat comes into effect after a period of time and you model it then so be it and its up to us to manage it. If there is historical evidence of mechanical failure after a period pf time then that is indeed where Russian Roulette comes into it and if there is that evidence you could of course program in a random time for failure beyond 5 minutes. I think it was Al Deere that told of a sortie in his Autobiography where he is returning to England after a long drawn out combat over France where he had left BCO operated continuously way beyond the 5 minutes. I think it was about twenty minutes, I'll have to re-read the book. Anyway it eventually began to run roughly but after correcting things the engine cooled down and performed perfectly well for the rest of the flight. It may even have been an earlier mark of Spitfire but it was a testament to the general reliability of the Merlin.

 

What this argument sometimes comes down to is 'the LW' not wanting 'the RAF' to gain unfair advantage but accurate modelling will defeat those arguments.

 

Other than that I don't think there is any practical reason why it should not be operated beyond the five minutes, after all we don't have persistent damage modelling (damage or wear carried forward to the next sortie) and we can assume that having reported it to the ground crew it would have been checked and the engine replaced if necessary, or that we were assigned another aircraft.

[Friedrich-4B]

I am curious as to why you would think the higher cooling requirements of the Merlin 66 means it is more reliable?

 

No such comment was made or implied - it was merely an observation that the early Merlins relied on 100% glycol cf. the 30/70 glycol & water of later series Merlins.

Edited November 11, 2015 by Friedrich-4/B

[Kurfürst]

I observe that the tougher Merlin 66 series pistons failed in as little as 7 1/2 hour stress load acccording to the stress test results posted. Even the toughest ones did not last longer than 50 hours.

 

I wonder what the lifespan of the less tough Merlin II/III's pistons could have been then.

 

I also wonder what sort of requirement R-R had in mind before clearing a rating for use, as it cleared +18 lbs while the pistons kept failing under 10 hours of stress at the said load.

[Rapidfire]

I observe that the tougher Merlin 66 series pistons failed in as little as 7 1/2 hour stress load acccording to the stress test results posted. Even the toughest ones did not last longer than 50 hours.

 

I wonder what the lifespan of the less tough Merlin II/III's pistons could have been then.

 

I also wonder what sort of requirement R-R had in mind before clearing a rating for use, as it cleared +18 lbs while the pistons kept failing under 10 hours of stress at the said load.

 

I dont think anyone in this sim will be flying it straight for 10 1/2 hours :thumbup:

[Barfly]

I would not be concerned about running a few to 5 minutes at 18" boost in flight, knowing that the motor had been stressed at that power setting and survived for 7+ hours in destructive testing.

 

The entire point of that testing was to induce accelerated wear on the engine to find areas that could be improved, that would lead lower probability of failure at all settings and increase overall engine life. A method of improvement deemed more expeditious than just flight testing and reviewing engine issues during operational deployment.