Spit/109 sea level speed comparisons in 1.08 beta patch

[JtD]

Originally Posted by Glider

What is more likely to go wrong, A prototype on its sixth flight or a test pilot of many years experience. The problem was traced to issues with the avionics and delayed responses to control input, not pilot error.
These had been calculated and tested in simlators but it was only when they flew that the problem was idnetified.
So the calculations and theory was flawed resulting in a serious accident the pilot was lucky to get away with. People who rely on theory are banking the farm on a theory and thats why I posted the video.

OK, so they did employ maths and physics improperly. I'm fairly certain that they came up with proper calculations after the accident and managed to simulate the problem. Just like we can calculate turn performance nowadays, the calculation is sound and all you can do wrong is input data.

This what hve ruined Il2 with a Spit that never depleted his E

You're wrong, Spits always flew to the same physics that applied to all other planes. The reason it could sustain a 17s turn is because it's one of the aircraft's design features. Just like high speed was a design feature of the Fw 190, which had no problem whatsoever to outrun Spitfires. Take a ton off a 190, give 200 extra hp at altitude and add 20% drag, and you got yourself a Spitfire.

[MiG-3U]

Originally Posted by Kurfürst

Nope, this is just your opinion and has nothing to do with any test report's contents.

The facts:
1. Prototype aircraft V15a, tested well before production started
2. Tested speed 493kmh at altitude of 440m, gives 485kmh at 0m
3. The supercharger has two fixed speeds:
- boden- and hohenlader are claimed and the optimal change altitude is determined
- manifold pressure drops above the FTH of the bodenlader, until hohenlader is set on
- the speed test confirms that the supercharger has two fixed speeds
- according to Flugmotoren und Strahltriebwerke by Kyrill von Gersdorff, Kurt Grasmann, Helmut Schubert the first order of the DB601 was the pre-series of 150 motors, A-0 ie Baureihe A (carburator engine with fixed speed supercharger), so based on engine number of 140, the V15a had one of these instead a A-1. The hydralic clutch came later with the Baureihe B along with fuel injection.

Originally Posted by Kurfürst

Unfortunately it is test data and it is relevant. Unless you want to dream up specifications.

It's not a test, just a piece of paper, no test data nor kenblats of production planes support 500km/h at sealevel. Everything else is around 460-470km/h including swiss planes with the 601Aa.

Originally Posted by Kurfürst

Oh but an 500+ kph Spitfire I as fast as the 109F *IS* logical, riiiiight?

Calculating the speed of the the Spitfire I at +12lbs the same way as done in the V15A report:

Density at sealevel: 1.225 kg/cubic meter
Power at sealevel at +6.25lbs: 880hp
Power at sealevel at +12lbs: 1180hp
Speed at sealevel at +6.25lbs: 280mph

r = ((1180/880)*(1.225/1.225))^(1/3) = 1.103

V0 = 280mph * 1.103 = 309mph = 497kmh

However, that is a crude, unaccurate and partially wrong way to calculate it.

Originally Posted by Kurfürst

Thank you for admitting that your remark about supposed two speed superchargers was just speculation.

The only speculative but logically correct part in my post is the size of the oil cooler, and it was there only because you asked it. The rest are facts.

Originally Posted by JtD

Regarding level speed performance of the 109, a question raised by I think MiG-3U puzzled me, maybe you have a good explanation, I'm at a loss for now: How come the 109E is faster than the 109F at less power, if you accept the 498 km/h for the 109E at 990ish hp from the V15 test and the 495 km/h for the 109F at 1065ish hp from the 109F Kennblatt?

Thanks for correcting the power of the 601N.

We do have several datapoints for production 109E giving 460-470kmh at 1.3ata and 990hp.
Calculating again the speeds of the 109E same crude way using 470kmh as base line:
601Aa 1045hp = 479kmh
601N 1060hp = 481kmh

Then we have the 109F doing 495kmh ie about 15kmh faster than the 109E at same power, that difference is roughly same as found at FTH. These values match very well while 500kmh is clearly an outlier and not supported by any test or kenbalt of the production planes.

[Osprey]

Would you mind, TomcatVIP, not slandering me by implying that I am some sort of Spitfire fanboy. I don't appreciate it because it's just not true. You constantly insult people with your replies, it's all in the tone you apply, and then you often go on to make ludicrous statements afterward (such as the one about no energy loss for the Spitfire in COD).

If you reply to me again in this manner then I'll report it. The mods here are hot on infractions.

[Robo.]

Originally Posted by MiG-3U

It's not a test, just a piece of paper, no test data nor kenblats of production planes support 500km/h at sealevel. Everything else is around 460-470km/h including swiss planes with the 601Aa.

I am completely with you here (although I am a huge Bf 109 fan), the Mtt 500kph +-5% guarantee debate has been here before and I was saying pretty much what you're saying now.

[Al Schlageter]

Can someone tell why these 2 German documents have the Vo as 476-476kph and 466-467kph.

[Robo.]

It says underneath, that although those speeds are re-calculated for normal temperature and correct manifold pressure, they are not corrected for the guaranteed engine perfoamance yet.

Seems to me that no matter how I look at that, the guaranteed performance by Mtt is rather theoretical.

Good point.

[Kurfürst]

Besides the fact that both of these papers show 109s with the 990 PS DB 601A and not 1045 PS 601Aa....

And, despite the weaker engine operating at an unknown power, the first test (476 kph) still just satisfies the guaranteed specs of Messerschmitt (500 kph +/- 5%, that is: anything between 475 and 525 kph is O.K.).

[NZtyphoon]

In other words the Germans took it for granted that there was a possible variation of 50 km/h in guaranteed speed at sea level, which is no form of guarantee at all when life or death in air-to-air combat could rest on very small margins of speed. It also means the top speed of a 109E at FTH could vary by an even wider speed range - anywhere between 532 km/h (330 mph) to 582 km/h (361 mph).

[Al Schlageter]

Thanks Robo. The speeds are not within the +/-5% tolerance being in the 7% range.

Another point to discuss.

Someone said the, iirc, that the trim tabs on the Bf109 were set for a speed of 400kph. This would be ~80% of top speed. This would be max continuous speed would it not?

How much time would be spent at max continuous speed? The a/c wouldn't be at this speed when escorting the bombers but at a lower speed for which the a/c would not be trimmed for. I would think that the a/c would be trimmed for a speed the a/c would spend more time at, possibly 300-350kph. At these speeds, it would be much easier on the pilot.

Kurfurst once posted some test data on the Bf109G that was a plot of the top speed of several a/c. There was more a/c below the guaranteed top speed than above the guaranteed top speed. Just something to think about.

[Kurfürst]

Originally Posted by MiG-3U

The facts:
1. Prototype aircraft V15a, tested well before production started

Fact: report says aircraft is identical to production E-1.

Originally Posted by MiG-3U

2. Tested speed 493kmh at altitude of 440m, gives 485kmh at 0m

Fact: MIG 3U misrepresentats the report, which states:

Erflogene Geschwindigkeit 493 km/h, auf Normaltag und Garantileistung umgerechnete Geschwindigkeit 498 km/h im 0 m.

They have flown 493kmh at altitude of 440m, which was not yet corrected for German Standard Day conditions or the Guaranteed output of the engine. Bench tests confirmed engine was developing 45 PS less than it should have.

3. The supercharger has two fixed speeds:
- boden- and hohenlader are claimed and the optimal change altitude is determined
- manifold pressure drops above the FTH of the bodenlader, until hohenlader is set on
- the speed test confirms that the supercharger has two fixed speeds

Nope.

Fact: Boden and Hohenlader are just generic names for MS and FS speeds, present on all DB 601/605/603.

The supercharger has two . US trials of captured Bf 109E, later Rechlin trials of Bf 109G-6, G-14 also run with fixed supercharger speeds, something which is easily done on the DB 60x series with hydraulic coupling by bypassing the barometric control.

Originally Posted by MiG-3U

- according to Flugmotoren und Strahltriebwerke by Kyrill von Gersdorff, Kurt Grasmann, Helmut Schubert the first order of the DB601 was the pre-series of 150 motors, A-0 ie Baureihe A (carburator engine with fixed speed supercharger), so based on engine number of 140, the V15a had one of these instead a A-1. The hydralic clutch came later with the Baureihe B along with fuel injection.

Nope.

DB 601A-0.

"Gemischung durch: 1 Bosch PZ 12 HM 100/11 Einspritzpumpe für 12 Zyl."

"Lader: einstufiges Schleudergeblaese mit barometrischer regelung"

Originally Posted by MiG-3U

It's not a test, just a piece of paper, no test data nor kenblats of production planes support 500km/h at sealevel.

Nope. French trials for example with Bf 109E-3 WNr. 1304. (DB 601A-1, so lower power at 1,3ata) show 495 kph at about 500 meter altitude.

http://kurfurst.org/Performance_test...09EWNR1304.jpg

Everything else is around 460-470km/h including swiss planes with the 601Aa.

All figures match the V15a performance using Höhenlader well, indicating the tests

"Everything else", well.

WNr. 1774. 498 kph, E-1, "DB 601A", 1,35 ata. 1060 PS.
WNr. 1791. 475 kph, E-1, DB 601A-1, 1,3ata 990 PS, ie. 70 PS less power. "figures are not corrected for guaranteed engine output"
WNr. 1792. 467 kph, E-1 DB 601A-1, 1,3ata 990 PS, ie. 70 PS less power. "figures are extrapolated graphically to 0m" and "figures are not corrected for guaranteed engine output"
WNr. 1304, ca. 485 kph, E-3, DB 601A-1, 960 Hgmm (ca. 1,3 ata). 990 PS, ie. 70 PS less power. With estimated position error curves: +/- 15 kph on speed.
WNr. 2404, 464 kph, E-3, DB 601Aa, probably 1,35ata. Conditions unknown. Curves clearly show single speed supercharged performance with no appearant hydraulic curveture. Figures closely match WNr. 1774. Höhenlader performance (extrapolating to about 460 kph at SL)


Calculating the speed of the the Spitfire I at +12lbs the same way as done in the V15A report:

Density at sealevel: 1.225 kg/cubic meter
Power at sealevel at +6.25lbs: 880hp
Power at sealevel at +12lbs: 1180hp
Speed at sealevel at +6.25lbs: 280mph

r = ((1180/880)*(1.225/1.225))^(1/3) = 1.103

V0 = 280mph * 1.103 = 309mph = 497kmh

However, that is a crude, unaccurate and partially wrong way to calculate it.

The only speculative but logically correct part in my post is the size of the oil cooler, and it was there only because you asked it. The rest are facts.

As shown above, they are not facts but misrepresentation of the facts.

Your theory is basically this. Messerschmitt built a prototype for the Bf 109E series, which achieved around 500 kph with the the engine cowling still unpainted, without fuel injection and without a multi speed supercharger, which (then appearantly the Americans got hold somehow of another Bf 109E and oddly tested it the same way as the Germans theirs... ) . They have noted in their report that due to time constraints, they could not yet fit the proper exhausts and air intake, so "further increases in performance are possible".

Then they supposedly went on improving it with a oil cooler of the size of an elephant, that chopped down 40 kph (!!! ) from top speed, but strangely enough only at low altitude , they added direct fuel injection which probably made the engine even weaker. Happy of good days work, and that they achieved no less than 40 kph speed loss, they decided to put that new version into production. The legal and financial department went nuts too, and decided to give legal guarantees for reaching a performance that according to you, was impossible to achieve. Save for a few odd examples that landed in French, Swiss hands which matched V15a figures finely.

Extremely likely, yes.

Any observations on the "prototype" Bf 109E overlayed with the Swiss trials of WNr 2404?