FW 190

[Crump]

But why are they so slow when they test it here:

 

Do not forget that you have to look at the configuration.  As you change configuration of the aircraft, you change the lift and drag relationship which changes the power available.  In the same configuration and aircraft, the same amount of power equals the same speed.

 

 

For example, the 510 is with the ETC 501 rack and the 517kph is clean configuration with inner gear doors and without the ETC 501 rack.

 

Edited June 2, 2016 by Crump

[Crump]

Maybe this will help too.

 

[Crump]

BTW, Brake Mean Effective Pressure is the value used to calculate the Brake Horsepower of an engine.  It is not compression ratio but it is function of it.

 

The BMW801A/C has a lower compression ratio.  That is also why it could use 87 Octane B4 AVGAS.

 

The BMW801D2 compression ratio would cause detonation with 87 Octane and as such, required 100 Octane C3 fuel.

 

[Brano]

Thank You Brano!

You are welcome 

[JtD]

Not having sekrit documents from ЦАГИ at hand, I will have to resort to what we have here or there.

 

Crump has detailed that a FW-190 does fairly exactly 510 km/h at sea level, given ANY powerplant of same dimension and weight producing 1370 hp at sea level. Right? (Nothing is trivial here.)

Not quite right. Fw190 varied widely in their aerodynamic properties. For instance, the Fw190A-4 is stated to have gills and the Fw190A-5 is stated to have adjustable cooling outlets. Closing these outlets will alone make a difference of ~20km/h in level top speed.

But it should be kept in mind that A-3's and A-4's were re-equipped with adjustable cooling outlets in the field, and that there's no guarantee that in every test performed they were properly adjusted and closed in level flight.

 

At any rate, adjustable cooling outlets would also explain your below question.

 

It is impressive that the A-5 is a lot faster according in the chart you posted. How come? I mean, given the airframes are fairly similar, I would deduce from that chart that höchstzlässige Dauerleistung @ 2300 rpm and 1.2 ata would suddenly be significantly higher in an aircraft that differs only in mild variations of the airframe? The chart you posted doesn't have the speed compressibiity adjusted. How would it look if it was? Can it explain the difference?

Additionally, racks for bombs or tanks, armament, radio, intakes, landing gear covers and all that may vary, too. So can the condition of the aircraft, in particular if examples captured in the field.

And, of course, you can expect simplifications and outright errors in documents of the nature of the NIIVVS report (which Brano has correctly pointed out in the mean time). It's just one piece of intelligence information, and intentionally summarized and simplified on top of that.

 

It is interesting that the Soviet in this NIIVVS document state that one of the major differences between the A-4 and A-5 is that in the A-5, the wing MG-FF are missing in the design and an installation of them is not planned for. Feel free to ask Crump what he thinks about that.

[JtD]

WRT engine power:

 

Kampfleistung: The BMW801A/C produces 1460hp@2400rpm/1.27ata. The BMW801D produces an extra 60hp, ie. 1520hp@2400/1.32.

Dauerleistung: The BMW801A/C produces 1280hp@2300rpm/1.15ata. The BMW801D produces an extra 90hp, ie. 1370hp@2300/1.20.

Figures are stationary FTH figures for both of them as taken from the manual. Apples to apples comparison. Agrees with the data Crump's posted a few posts up.

As stated already, it's just not true that the BMW801D produced the same power at Dauerleistung as the BMW801A/C at Kampfleistung.

Furthermore it should be mentioned that initially, the BMW801D was limited to

2350rpm/1.28ata Kampfleistung and 2250rpm/1.14 Dauerleistung, resulting in no extra power when compared to the A/C.

 

The Soviet standard procedure was to test aircraft at nominal power, which is the Kampfleistung in German aircraft.

Edited June 2, 2016 by JtD

[Crump]

At 510kph RAM power...

 

The BMW801C produces ~1390 PS to 1380 PS and that difference is too small to measure from the 1370 PS the BMW801D2 produces at 1.2ata on the airspeed end because velocity is cubed in relation to power....

 

 

 

 

 

Looks like the BMW data says they do produce the same power under those conditions!

 

And that very much agrees with the VVS data which is very clear the power production is the same at their test point.

 

 

 

[JtD]

The NIIVVS is giving the same power figures for both the Fw190A-5 and the A-4 because according to them, it's the same engine in both machines. Obviously so, as it is not listed in the differences, which are

1) small changes to the engine installation (cooling, prop)

2) armament (no MGFF)

3) armour (see scheme)

 

BMW states that the Kampfleistung of the C is about 100hp more powerful than the Dauerleistung on the D, if you use comparable figures. You have posted the figures yourself (1460hp@700m/1370hp@1200m).

[Crump]

 

 

(1460hp@700m/1370hp@1200m)

 

None of those conditions are RAM power at 510 kph at sea level.......

[JtD]

True, under these conditions were at 1390 vs. 1260, as stated already. Still an about 100hp difference.

[Crump]

True, under these conditions were at 1390 vs. 1260, as stated already. Still an about 100hp difference.

 

Static power but our aircraft is not producing static power.  That is why 1.27ata @ 2400 U/min for the BMW801A (1390PS RAM power at 510kph) and Dauerleistung 1.2 ata @ 2300U/min in the BMW801D2 (1370PS) are the same.  This is also evidence by the fact both aircraft do have a Vmax of 510 Kph under those same conditions.

 

Crazy huh?

 

The VVS data point is good data giving us power, weight, and performance under known conditions to compare.

 

End of Story

You can simply read the documents posted already in the thread!

I do not see any reason to continue feeding another bonfire of the vanities.  The community has some good data to compare performance.

[JtD]

No, it's not static power. It's rammed power at sea level at 500 km/h. For both. If you want to use static power for both, go two posts up. Either set of figures gives a 100hp difference.

 

You keep comparing static FTH D power with rammed sea level C power. That comparison is invalid. As illustrated by the C chart you keep posting, the engine loses roughly 90hp in low blower over 1200m altitude and another 20hp due to ram.

[Crump]

You are simply arguing minutia.

 

Depending on the RAM power chart I examine for the BMW801D2 the largest difference I can find is 60PS.  The average difference is 20PS. 
 

The cubed root of 60 is 3.9 and 20 is 2.7.  Nothing worth writing home about in terms of aircraft performance......

It gives good agreement in terms of significant digits and therefore is the same power and within normal aircraft performance variation.

[JtD]

First chart I picked for the BMW801D shows a loss of 60hp over 1200m altitude between FTH and sea level. Next one - 60. Next one - 60. Next one - 70. Next one - 70. Average 64. Call it 60.

Average sea level ram loss the same way - 40.

Total - 100.

How you "average" up at 20 is beyond me. I'd need to see two dozen showing nil power loss (which is physically impossible) to end up at 20.

 

Call it minutia if you like, but the 801C@2400/1.27 produces ~100hp more than the 801D@2300/1.2 in low blower under comparable conditions.

[Crump]

 

 

over 1200m altitude

 

Sea level..... 

[JtD]

Yes, exactly. Are you even aware that the power figure you keep quoting for the BMW801D@2300@1.20 is for 1200m altitude?

[Crump]

 

 

Well basic physics tells us that the same amount of force on the same mass object will produce the same acceleration.  That acceleration will reach zero at the same point.  In other words, you exert the same amount of power on the same airplane under the same conditions.....you are going to get the same airspeed!!   Pretty simple stuff.  It is not an assumption but rather just a basic fact of physics.

 

 

[JtD]

Ah, now a chart that lists Dauerleistung as 1420 static at FTH instead of the 1370 static at FTH you were originally quoting? Not 100% comparable to the C figure any more, but it still only shows 1320 (-100) rammed at sea level.

[Crump]

 

 

he cubed root of 60 is 3.9 and 20 is 2.7.  Nothing worth writing home about in terms of aircraft performance......

 

[Crump]

 

 

You are simply arguing minutia.   Depending on the RAM power chart I examine for the BMW801D2 the largest difference I can find is 60PS.  The average difference is 20PS.

 

[ZachariasX]

The cubed root of 100 is 4.6. This is still not so much. So power output according to Crump make (at worst) less than 5 difference to JtD's view on things? Correct?

 

JtD, you mentioned that also would translate to 1 sec difference in turn time. Are the turn times as we have them in-game now farther off than this variation?

 

Z

[JtD]

Not correct. The cubed root of a fixed hp figure doesn't mean anything. Crump likes to do it, for whatever reason, but it is completely meaningless. A few estimates can be made as follows:

 

Speed: Cubed root of horsepower ratio old/new translates into estimate of speed ratio old/new. For instance, if at 1300hp your plane goes 510, and you have an extra 100hp, the new speed will be in the region of 510*(1400/1300)^(1/3) = 523

 

Climb: Convert horsepower to Watt by multiplying with 735, divide by mass (kg) and gravity (10m/s²) and you get an idea of the climb rate improvement in m/s. 100hp for a 4ton plane, it's 73500/10/4000 = 1.8m/s.

 

Turnrate: Similar to speed, a bit more as a trend, amount of trend depending on how good a turner your plane was before. For a Fw190@1300hp@low altitude, 100hp extra are ~0.8s.

 

Personally, I don't consider near 15 km/h level speed, 2m/s climb and 1s of sustained turn small margins, but that is my personal point of view. I'm very focussed on relative aircraft performance in combat. My game currently crashes upon start-up, so I can't check in game performance for now.

Edited June 3, 2016 by JtD

[ZachariasX]

 

 

Personally, I don't consider near 15 km/h level speed, 2m/s climb and 1s of sustained turn small margins, but that is my personal point of view. I'm very focussed on relative aircraft performance in combat. My game currently crashes upon start-up, so I can't check in game performance for now.

 

I was stating my surprise how seemingly small engine side effects supposedly were if i followed that reasoning as I understood it.

 

As we fly the aircraft in game here, the differences you mention surely make a difference, as there are so many people fling their aircraft at the edge of the envelope.

[Crump]

We are not dealing with an extra 100 hp.....

 

Why JTD keeps repeating that fiction is unknown.

 

The margins are 20 to 60hp....which is insignificant.

[Crump]

510*(1380/1320)^(1/3) = 517

 

Or a 1% speed difference that is not even noticeable buried in a 3% normal variation.

 

In terms of aircraft performance.....it is exactly the same and why the VVS simply state the power is the same.

[JtD]

I was stating my surprise how seemingly small engine side effects supposedly were if i followed that reasoning as I understood it.

 

As we fly the aircraft in game here, the differences you mention surely make a difference, as there are so many people fling their aircraft at the edge of the envelope.

The effect on speed is generally quite small, if you look at the percentages of 1..2..3%. But absolutely, 10 or 15 km/h are quite a bit.

In terms of climb rate, it's rather vice versa, figures like 1.5m/s don't really sound like much, but it's a 10% improvement, even down low.

These couple of % add up considerably in a combat situation...may make a difference of 50 or 100m of altitude gain in the initial zoom climb, which determines if you become hunter or prey.

 

We are not dealing with an extra 100 hp.....

It's pretty obvious that the chart you've posted doesn't show the 1370hp@1200m static seen in every side by side data of C&D engines. The chart shows 1420 instead, 50 more.

Everyone is free to draw his own conclusions about what would happen to the 1320@SL rammed figure of that chart if static power was matching the side by side figures, showing 50 less.

At any rate, if the difference is 60 or 110 doesn't really matter to me now. It's not "the same power".

[Crump]

[Edited]

[Bearcat]

Enough. Closed temporarily.

 

There are enough charts, diagrams and anecdotes in this one thread alone to last for some time.... or at the very least uintil it is reopened ... if it is reopened at all....