Inaccurate performance data for BOB fighters in COD comparing to RL data

[Osprey]

If you have not voted chaps, then you need to.

http://www.il2bugtracker.com/issues/174

I would appreciate one of the well written and thorough performance explanations on the bug report please to cover each type we have in the sim. Luthier will need it.

Sod Crump, we have the issue raised to the mods, issue the coups-de-grace via the Bugtracker

[Robo.]

Originally Posted by 41Sqn_Banks

Rolls Royce gives 990 b.h.p as "international power rating" (+ 6 1/4 Boost with 2,600 RPM at 12,250 feet), see http://forum.1cpublishing.eu/attachm...8&d=1334724563.

Don't we have to convert the boost values to ata before we compare them make a statement about the factor between them? Otherwise the atmospheric pressure offset is not eliminated.

My point is that early Merlin were not designed to operate at 4.5lbs. boost max. I am aware of the conversion issues and I only tried to point out that Crumpps assumtion was wrong.

[41Sqn_Banks]

Originally Posted by Robo.

My point is that early Merlin were not designed to operate at 4.5lbs. boost max. I am aware of the conversion issues and I only tried to point out that Crumpps assumtion was wrong.

According to this article the Merlin was designed as "1,100 hp-class" engine to fill the gap between the 700 hp Peregrine and the 1,500 hp Vulture.

However I don't think Crumpp claims that the Merlin was limited to +4 1/2 boost at any time, if he does he will certainly provide a document to support this claim. I think he consider the "maximum continuous rating" of every engine as the design goal and uses this value to compare different engines. He's free to do so. Others consider the maximum power, and some may use the takeoff power. It doesn't matter, the engine remains the same.

[NZtyphoon]

Originally Posted by 41Sqn_Banks

According to this article the Merlin was designed as "1,100 hp-class" engine to fill the gap between the 700 hp Peregrine and the 1,500 hp Vulture.

However I don't think Crumpp claims that the Merlin was limited to +4 1/2 boost at any time, if he does he will certainly provide a document to support this claim. I think he consider the "maximum continuous rating" of every engine as the design goal and uses this value to compare different engines. He's free to do so. Others consider the maximum power, and some may use the takeoff power. It doesn't matter, the engine remains the same.

The first document, dated November 1939, confirms that after modifications the Merlin II and III were cleared for using 100 Octane and +12 boost, and confirms the potential limits of the engine as +17 lbs. It also shows that modifications to the boost control cut out were already in hand:

Paragraph 9: "The modification to the boost control cut out to limit the maximum boost to 12 lbs sq. in. are simple and in hand (otherwise full throttle would give about 17 lbs sq. in.)

It also confirms that stocks of 100 Octane were considered high enough to allow Merlins to use it, contrary to Crumpp's opinion, based as it is on a pre-war document.

Paragraph 11: The decision on this question (conversion of Merlins for +12 lbs boost) must be dependent to a large extent on sufficient stocks of 100 Octane fuel; but as it is understood there are adequate reserves of this fuel for the purpose it is accordingly recommended that approval...be given forthwith.

So far Crumpp has not shown us the relevant pages to confirm his "pilot's notes" are from June 1940, nor has he shown the relevant details of how A.P.1590B/J.2-W was already incorporated into them, as he claimed here:

Originally Posted by Crumpp

I have read those Banks. You misunderstand what I wrote. A.P. 1590B/J.2-W is incorporated into the June 1940 Pilots Operating Notes.

If the aircraft in service were most commonly using 100 Octane, those limits would be the ones listed under the limiting Operating Conditions of the Pilots Operating Notes.

That is how it works.

The 87 Octane limiting operating conditions are published as the predominate operating limits of the aircraft in June 1940. References to 100 Octane are minor footnotes denoting specialized circumstances that are not the common configuration.

I am seriously thinking he has evaded the question. Tsssk tsssk.

[Crumpp]

the "maximum continuous rating" of every engine as the design goal

It is the design goal. Maximum continuous is the power the engine is designed to develop and maintain.

It represents 100% of the power capability of an aircraft engine. Anything over that is an overload condition and will shorten the life of the engine.

Typically you see overload capability in take off ratings, sometimes climb ratings, and in emergency ratings.

It is the power the engine can produce at 100% capability that is the primary focus.

[28_Condor]

Originally Posted by JG5_Thijs

Gavin Bailey, ‘Narrow margin of criticality: The question of the supply of 100-octane fuel in the Battle of Britain’ English Historical Review volume 123 number 501 (200 p 394-411. (This article was quoted earlier by 28_Condor on page 98 of this thread, he, however, did not quote the article fully since there are some interesting points that Bailey brings up regarding the impact of 100 fuel use.)

Thijs

The download link didnt work

You can make the file available here? Thank you!

[NZtyphoon]

Originally Posted by Crumpp

It is the design goal. Maximum continuous is the power the engine is designed to develop and maintain.

It represents 100% of the power capability of an aircraft engine. Anything over that is an overload condition and will shorten the life of the engine.

Typically you see overload capability in take off ratings, sometimes climb ratings, and in emergency ratings.

It is the power the engine can produce at 100% capability that is the primary focus.

Originally Posted by 41Sqn_Banks

However I don't think Crumpp claims that the Merlin was limited to +4 1/2 boost at any time, if he does he will certainly provide a document to support this claim. I think he consider the "maximum continuous rating" of every engine as the design goal and uses this value to compare different engines. He's free to do so. Others consider the maximum power, and some may use the takeoff power. It doesn't matter, the engine remains the same.

Not so long ago Crumpp claimed that the Merlin was only capable of generating 400hp...

Originally Posted by Crumpp

You are talking about running the engine at 3 times its original design maximum capacity. Really guy? You think just changing the fuel did that?

I asked:

Originally Posted by NZtyphoon

So you think the Merlin was designed to run at about 400 hp?

Originally Posted by Crumpp

If that is what the engine produces at maximum continuous...YES.
Get a Spitfire Mk I POH and read the maximum continuous rating. That is the maximum power the engine is designed to safely and reliability produce.
Mixture control Normal = +4 1/2 lbs at 2600rpm

So he is trying to claim the Merlin III's maximum designed continuous power rating was +4 1/2 lbs at 2600rpm, and about 400hp.

[41Sqn_Banks]

Originally Posted by NZtyphoon

So he is trying to claim the Merlin III's maximum designed continuous power rating was +4 1/2 lbs at 2600rpm, and about 400hp.

I don't know if power at maximum continuous rating was 400hp, I've never seen a value for it. Rolls Royce always give International Rating, Maximum Rating and Maximum Take-off Rating. Sometimes Minimum Take-off Rating (this is at maximum allowed take-off boost with minimum allowed RPM, which is only important for fixed propellers).

Maximum continuous rating (1,15ata 2000 PRM) of DB601A was 810hp (@0km) to 860hp (@5km). As the maximum output is almost the same we can assume that the Merlin has a comparable power at continuous rating.

Here is the (not so serious) protocol from the design meeting at Rolls-Royce when they thought about their new high performance fighter engine. Engineer A is a daredevil, he likes fast, loud and dangerous stuff. Engineer B is a square and a careful engineer, he likes reliably stuff.
Engineer A: "I think with that design we should get 1,100hp maximum output. That's a great improvement compared to the 700hp of the Peregrine. Image how fast our fighters will fly with that. What do you think?"
Engineer B: "Hmm ... yes this should give about 800hp at a reasonable engine life of 100 hours between overhaul. I'm cool with that."
Engineer A: "Yeah whatever ... So we define our design goal as 1,100hp maximum and 800hp continuous output. Deal?"
Engineer B: "Deal! Let's do it!"

Later at Air Ministry ...

Engineer B: "This is our new engine design. We estimated it will will produce 800hp ..."
Engineer A: *facepalm*
Air Ministry: "What? The Germans build engines with 1000hp maximum output! You are useless!"
Engineer A: "May I interrupt? The 800 hp is the continuous rating, the maximum output will be 1,100hp."
Air Ministry: "... OK now that sound good. We want 900 engines delivered in 3 month. ... Oh and next time just tell me the maximum output. At Air Ministry we like fast, loud and dangerous stuff."

While leaving Air Ministry ...

Engineer A: "I told ya!"
Engineer B: "..."

[winny]

There's a book called "Britains war Machine" that I found last night. It contains a section devoted to the supply, use and production of 100 octane fuel.

It explains the whole Trimpell (Trinidad - ICI - Shell) refinery set up and says that the "shortage of 100 octane is a myth"

It's available as an e-book.

[Glider]

Originally Posted by NZtyphoon

Not so long ago Crumpp claimed that the Merlin was only capable of generating 400hp...



I asked:


So he is trying to claim the Merlin III's maximum designed continuous power rating was +4 1/2 lbs at 2600rpm, and about 400hp.

Must be a hell of a design to get 340 ish mph on 400 HP. Imagine what it could do with a decent engine in it