109 e4 performance

[Crumpp]

It's not a promise it's a contract. I.e. if the aircraft doesn't meet the specifications laid out in the contract then the RLM does not accept the aircraft and it goes back to the factory.

I thought this would be a pretty straight forward idea?

Absolutely.

It is a legal binding document that the customer does not have to pay for the aircraft if it does not reach the stated performance. There is no guessing required. Once more as already stated, both Mtt and the Luftwaffe confirmed that performance before that aircraft left the factory.

Using a prototype, Bf-109EV15a from 1938 with a new type engine at the time, DB-601A. A new type engine that Daimler Benz is saying does not reach its rated power yet but will in the near future.

Bf-109EV15a is for a fact not representative of a front line fighter two years later.

It certainly is not proof of any form of "optimistic" manufacturer's performance.

The Aa should behave slightly different down low and the EN rating was different, too.

There is a lot of debate in some very knowledgeable circles about the engine used. It was either a DB-601A1 or a DB-601Aa as the DB-601A was never an 1100hp engine.

The 5 minute rating is either 1.3ata (DB-601A1) or 1.35ata (DB-601Aa).

Crumpp, give up, mate, obstinance trumps knowledge every time!

We will give him a chance. I make mistakes, especially when I rush or am not all that interested. I also think robo is trying to learn.

This particular debate over Bf-109E WNr 1304 has been ongoing for years among a much more knowledgeable crowd, no offense meant to the IL2 Sturmovik players.

Even lining up the original Baumeister Datum for WNr 1304 has not solved the issue. It was built at a time when both engines were being delivered to Mtt. Without the engine Werknummer, we may never know.

Crumpp your calculation of 492 km/h is spot on, nice one!

It is not accurate without the pressure data.

Although the top speed figures are within limits, what do you think about the radiator drag and overall climb performance (see my previous post?) Hard to explain...

I don't see anything wrong with the radiator drag. It seems typical for a liquid cooled engine installation.

The climb performance is also typical for a colder than standard day. They did get better climb results than Mtt but their climb power settings appear off. Their rpm is high, which makes a difference and so is their manifold pressure.

All of that is secondary to the fact they performed the climbs on a colder than standard day.

[Robo.]

Originally Posted by Crumpp

Absolutely.

It is a legal binding document that the customer does not have to pay for the aircraft if it does not reach the stated performance. There is no guessing required. Once more as already stated, both Mtt and the Luftwaffe confirmed that performance before that aircraft left the factory.

Of course. No one ever stated in this thread that any Emil accepted by the LW has failed to meet the specifations agreed in the contract. What I dared to say was that the tolerance was rather generous at 50km/h, and we can not assume automatically that the actual performance of Aa Emils was always 500km/h. I suggested certain variability to be modelled (for all aircraft obviously). Please read properly.

Originally Posted by Crumpp

Bf-109EV15a is for a fact not representative of a front line fighter two years later.

Just what I said, engine not quite ready + small important flaws in finish and lack of manifold exhaust covers. The test is interesting in certain aspect but no one ever suggested modelling the ingame A-1 Emils according to the charts.

Originally Posted by Crumpp

There is a lot of debate in some very knowledgeable circles about the engine used. It was either a DB-601A1 or a DB-601Aa as the DB-601A was never an 1100hp engine.

The 5 minute rating is either 1.3ata (DB-601A1) or 1.35ata (DB-601Aa).

I know this and it has nothing to do with what I wrote. I was simply asking how do you think the Emils with both A-1 and Aa should be modelled in game including the limits of the ratings. (Especially regarding the top speed at the sea level to start with). My reply was to Kwiatek simply to point out at different character of A-1 and Aa engine, because he did not make any difference between these 2 in his original post.

Originally Posted by Crumpp

We will give him a chance. I make mistakes, especially when I rush or am not all that interested. I also think robo is trying to learn.

Yes you did quite a lot of mistakes, mainly due to the fact you don't read properly what the others have to say and you somehow assumed that everyone except you doesn't know anything. You're learning, too dude, that's OK.

Originally Posted by Crumpp

It is not accurate without the pressure data.

It is good enough given the information available. My point was that the value seems to be reasonable for the sim imho.

Originally Posted by Crumpp

I don't see anything wrong with the radiator drag. It seems typical for a liquid cooled engine installation.

That's right, but it is clear the French had some cooling issues and at one attempt, there was (unspecified) engine malfunction. All I said is that this test is a bit dodgy, too, just like V15a. The 50km/h difference is some 5-10km/h too big when compared to other test. I believe this is due to different ata setting during the two flights being compared at 5000m.

Originally Posted by Crumpp

The climb performance is also typical for a colder than standard day. They did get better climb results than Mtt but their climb power settings appear off. Their rpm is high, which makes a difference and so is their manifold pressure.

They got worse climb results.

Originally Posted by Crumpp

All of that is secondary to the fact they performed the climbs on a colder than standard day.

And yet, they were overheating, perhaps those higher RPM and different components and coolant as mentioned in the notes. Who knows... But one is for certain - 1304 just as V15a test is interesting and informative, but not really usable.

So can you please say what do you think the top speed for both engines with all 3 rated MFP/RPM from the above chart would be? In your opinion?

[Crumpp]

we can not assume automatically that the actual performance of Aa Emils was always 500km/h.

Of course not, 500km/h is just the mean.

Just what I said, engine not quite ready

Right, we agree on it.

I was simply asking how do you think the Emils with both A-1 and Aa should be modelled in game including the limits of the ratings.

Ok, I might do that for you if I have the time.

The 50km/h difference is some 5-10km/h too big when compared to other test. I believe this is due to different ata setting during the two flights being compared at 5000m.

5-10Km/h is nothing. It could be bugs on the leading edge and windshield....

This is why I don't get too involved with these kind of discussion's. You claim I think I know everything. Well, I don't. I do know airplane performance and the science of flight.

It winds up being an argument over every little point.

They got worse climb results.

Ahh so they did. Interesting but I think if you check out their radiator settings and compare it to what the Germans used you might find your answer.

They flew a large part of that climb regiment with radiators fully open and an engine on the verge of overheating. I imagine the fuel metering system set up for synthetic fuels did not like the French fuel.

The climbing was done at the Center with the radiators open up to 4000 m. then progressively closed until 8300m. It is possible that the different components (1) used by the German tests could permit climbing with closed radiators.

Different components is the oil and coolant. Additionally the French though the speed range is the same as the climb range. It is not. The percentage error over mean for climb performance Mtt says is 8%.

Given that, even with radiators open, the climb performance is within 7 seconds of the German results at 1000M.

One thing about recording climb performance. It is one of the hardest areas of performance to nail down accurately because it depends on so much that changes.

The French instrument error is 3% too.

[Robo.]

Thanks for the reply Crumpp - as you see I am not in any kind of disagreement. The calculations are not really for me, rather for the sim. I find it interesting and if the 1c guys happen to read this or if it gets reported, we might as well end up having Emils closer to the real thing FM-wise. I know I am naive

5-10 km/h - i got your point point, but it is really about these small details and I pointed out that the 2 flights compared (rads open / closed) at 5000m were at different MFP and the difference was perhaps smaller than 50km/h.

Also agreed on the climb performance -most difficult to measure as enviroment is a massive factor. Funny thing is they got the top speed right and climb so much off when the a/c was the same. I also believe it might be fuel / coolant / oil / instruments. I also believed that particular 109 has been slightly damaged before - hence the 'components' thought, not just fluids. No further info on that provided...

As for the actual figures and calculations for top speed at sea level:

DB 601 A-1 / 9-9518A

1.40 ata 2400RPM 1100HP (1 minute)
1.30 ata 2400RPM 990HP (5 minutes) radiator 1/4 open 467km/h
1.?? ata 2200RPM 810HP (30 minutes)

DB 601 Aa / 9-9518E

1.45 ata 2500RPM 1175HP (1 minute)
1.35 ata 2400RPM 1045HP (5 minutes)
1.15 ata 2300RPM 950HP (30 minutes)

Anyone cares to fill in the blanks, ideally rad fully open / rad fully closed + E-3 E-4 aerodynamics + /B aerodynamics?