Modelling engine wear and WEP limitations

[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?

[Seadog]

http://i38.photobucket.com/albums/e1...00octane_2.jpg

OK so here we have the engine life of a Merlin III at 12lb boost and in 1938 it was 10 hours and later engines it was 20 hours at 12lb boost.

20 hrs = 30 sorties flown exclusively at 12lb/3000rpm, or 80 sorties at 15min/sortie, which is already exceeding average aircraft life during the BofB.

[Crumpp]

OK so here we have the engine life of a Merlin III at 12lb boost and in 1938 it was 10 hours and later engines it was 20 hours at 12lb boost.

Geez....

Nowhere except in your mind can you run a Merlin at 12lb for 10 hours.

That is the total time the engine ran during endurance trials of 5 minute intervals with a 20 minute rest period between each interval.

It could be used for 5 minutes at a time. That use had to be logged and the engine inspected for serviceability, and the reduction in life assessed before it could flown again.

[Seadog]

"I had to return from Nuremburg in a Wellington II on one engine and used maximum boost and revs on a Merlin X for five hours with no sign of distress..."

= +10lbs at 3000rpm.
The Merlin in Perspective,p25.

[TomcatViP]

Merlin X (two stage - two speed s/c) later eng model (with 1145 HP and 9lb )

[Kurfürst]

Originally Posted by TomcatViP

Merlin X (two stage - two speed s/c) later eng model (with 1145 HP and 9lb )

In 1938 it was probably an early internal RR - and not a service - designation (X = eXperimental?) for a Merlin with 100 octane IMHO.

[TomcatViP]

X stand for 10 - Beware that all those long night of typing might hve put some excessive strain on your brain eng

[Blackdog_kt]

Originally Posted by Seadog

OK. Now how to sim that?

A few people already gave pretty good ideas on that, but it's currently buried under the Merlin debates

As a short recap:

a) accelerated engine wear model if spawning with a brand new airframe on each sortie, selectable by the player from the difficulty options

b) realistic engine wear model if spawning with the same airframe (relevant aircraft parameters carry over from one sortie to the next in the context of a dynamic campaign), along with a penalty for deliberately "recycling" airframes with abused engines, both for single and multiplayer...once again, selectable from the difficulty options

c) the two above models are mutually exclusive...we shouldn't be able to enable both an accelerated engine wear model and a "carry over" model, clicking one on the difficulty options would deselect the other, but it would still be possible to disable both

This makes sure that if the player is so inclined, he can fly with the uncertainty and chance of mechanical failure that engine abuse would pose.

Simple, clean, optional

[TomcatViP]

Originally Posted by Blackdog_kt

A few people already gave pretty good ideas on that, but it's currently buried under the Merlin debates

As a short recap:

a) accelerated engine wear model if spawning with a brand new airframe on each sortie, selectable by the player from the difficulty options

An accelerated wear model wld be very difficult to achieve in term of stability. Mind that any programming glitch or non-anticipated player action would hve its repercussion magnified by the accelerated engine code.
I guess that 1C will need a lot of trying in here that way.

[Crumpp]

"I had to return from Nuremburg in a Wellington II on one engine and used maximum boost and revs on a Merlin X for five hours with no sign of distress..."

As a RL pilot, I see that as maximum continuous which is THE engines maximum boost and revs....

He does not say he used "Emergency Power"....