Spit 5

[Crumpp]

The Fw190A-8 could only manage 375mph at 26800' and 365mph at 27700'. The Spitfire VIII JF275 with a Merlin 61 was 22mph and 37mph faster and that is with a tropical filter fitted.

That is true.  No one is claiming the 190A was a great High Altitude performer.  Nor are they claiming it could doing anything more than what is documented.  Only in 1942 did the 190 have a commanding advantage over the Spit Mk V.  The Mk IX series and the 190A stayed as equals.

http://www.terra.es/personal2/matias.s/fw190.htm

190's fought spits in the vertical because they couldn't turn with them.  Spits fought 190's in the Horizontal because they could not hang with them in the vertical.  The first model of Spitfire that could was the Spitfire Mk XIV.  It increased the spit airframe both in power AND weight.

Taken plane for plane the Spitfire IS a more aerodynamic design.  This is evident from the following:

http://www.anycities.com/user/j22/j22/aero.htm

But when you factor in the physical size difference, the 190 comes out ahead simply because it has less surface area total.  Even it's radial engine drag approximates the surface area of the Spits radiator openings.  I instead of two square openings under the wing, you have one circle opening in the front.

The difference IS only POINT TWO (.2).  However drag quadruples with velocity.  Example, 1 mile and hour = .8 difference, 2 miles and hour = 1.6 difference, 3 miles per hour = 3.2 difference.  You can see how quickly that small difference builds up.

Induced drag, no matter how small, adds to the Spits overall drag.

Now some people will claim they can pick up a calculator and figure out the lift Co-efficient for these Airfoils.  I myself have to rely on Foilsim or other programs that do a pretty poor job of simulating the atmosphere.  Best we got without access to a wind tunnel.

http://www.grc.nasa.gov/WWW/K-12/airplane/liftco.html

In regards to the Spitfire Speed.  We have a test done at a Merlin 66 (+25).  The speed increase in it IS an AVERAGE of 30 mph.  It makes some gains.  

http://www.fourthfightergroup.com/eagles/merlin66_18_25.jpg

However at it's full throttle height, It overall speed gain is not very spectacular over the Merlin 61.

Merlin 61 top speed at Full throttle height:

------------------------------------------------------------------------------------

Maximum true air speed in F.S. supercharger 403 m.p.h. at
27,400 ft.

http://www.fourthfightergroup.com/eagles/bf274.html

------------------------------------------------------------------------------------

Merlin 66 (+25)

------------------------------------------------------------------------------------

Maximum true air speed in F.S. gear = 389 mph at 13,800 feet

http://www.fourthfightergroup.com/eagles/jl165.html

------------------------------------------------------------------------------------


Adding a new fuel pump increased it's Full Throttle height speed.

However it is very misleading to quote "30 mph gain".  Since no data exists on this website on Merlin (+18) performance without the new pump NOR is there any data for a Merlin (+25) with the new pump the reader is left to speculate.

Judging from comparing speeds approximating (+18) on Table IV and altitudes:

http://www.fourthfightergroup.com/eagles/jl165.html

And comparing them with Table I here:

http://www.fourthfightergroup.com/eagles/ma648.html

I don't think the Spitfire gained all that much speed from this fuel pump.  Around 15 mph at some speeds, ranging down to none at others.  Again, it is only speculation since no hard data exists.  You certainly cannot claim a 30 mph increase over all, at least not at low altitudes.  Remember the Merlin 61 has faster top speed than the Merlin 66 (+25).

The Merlin powered spits just didn't have enough inertia or Horsepower gain to overcome the drag of that same high lift wing which gave them such excellent low speed performance.

Looking at the Speeds I have to conclude the Merlin 66 (+25) is the correct Spit IX to fight the FW-190A8.  The contest would be close.

Crumpp

[Nashwan]

In regards to the Spitfire Speed. We have a test done at a Merlin 66 (+25). The speed increase in it IS an AVERAGE of 30 mph. It makes some gains.

http://www.fourthfightergroup.com/e...lin66_18_25.jpg

However at it's full throttle height, It overall speed gain is not very spectacular over the Merlin 61.

There is no difference at full throttle height because there is no extra power at full throttle height.

In fact, at the FTH for the Merlin 61, the Merlin 66 puts out less power, if anything.

At the altitudes where you have a large power increase, you have a large speed increase.

At the altitudes where there is no power increase, there is no speed increase.

However it is very misleading to quote "30 mph gain". Since no data exists on this website on Merlin (+18) performance without the new pump NOR is there any data for a Merlin (+25) with the new pump the reader is left to speculate.

Forget the SU fuel pump. There's only one aircraft on that page with the pump, and it's performance is only slightly different to a normal Spit.

From the tests of the Spit VIII and IX, the speed increase is pretty clear.

The difference between the Merlin at 18 lbs and 25 lbs is up to 400 hp. At some altitudes you get the full 400 hp increase, ie at the FTH height when run at 25 lbs you get 400 hp more. That declines until at the FTH at 18 lbs, you get no extra HP, and thus no extra speed.

Look at the boost figures for JL 165 on the speed chart. At altitudes where 25 lbs can be maintained, it's about 30 mph faster than at 18 lbs. However, that 25 lbs boost can't be maintained at all altitudes, and as it declines to 1 8lbs, the speed increase declines as well.

I don't think the Spitfire gained all that much speed from this fuel pump. Around 15 mph at some speeds, ranging down to none at others.

The speed increase from the fuel pump would be less than that, I think, but no-one is claiming a 30 mph speed increase from a fuel pump. What people are claiming, and the trials show, is a 30 mph increase from increasing the boost from 18 lbs to 25 lbs.

[gripen]

Originally posted by Crumpp
NASA says the Cl is rather complicated and is usually solved for experimentally in a wind tunnel.

Here Crumpp can't understand that we just calculate what lift coefficient is needed to produce certain amount of lift at given conditions. The Formula in the NASA page  is fairly simple:

Cl=L/(r x (V^2/2) x A)

Where:

Cl=lift coefficient
L=lift
r=density
V=speed
A=wing area
 
As an example we can calculate what lift coefficient is needed for the Spitfire flying level 200km/h near sea level, all the needed parameters are easy to find:

L=33354 N
r=1,229kg/m3
V=55,56m/s
A=22,48m2

=> Cl=0,782

Originally posted by Crumpp
No the value for "e" is the efficiency factor and you do not mention what you are using.

My post 08-07-2004 09:59 PM:

"Induced drag coefficients can be easily calculated by using the formula from your link above, note that I use same efficiency factor 0,9 for both planes despite Spitfire apparently was better in that area"

My post 08-08-2004 09:38 PM:

"All the needed values are listed allready above including E (efficiency) factor. As noted above, I used same E factor 0,9 for both planes. But as NASA site notes, the Spitfire had near ideal shape of the wing, so here are the values at 3g load using E factor 0,95 for the Spitfire and 0,8 for the Fw 190"

In later post I used capital E just like Crumpp in his post 08-08-2004 12:45 PM

Originally posted by Crumpp
No I have not confused induced drag and total drag.  I simply state that the Spitfire had more BASIC drag and ANY induced drag just adds to it.

Here Crumpp tries change his argument, but the funny thing is that his post ends as following:

Originally posted by Crumpp
The reader has to dig a little harder to see that and realize the penalty the Spitfire pays for it's wonderful high lift wing characteristics.

Shortly Crumpp can't understand induced drag nor lift coefficient.

gripen

[MiloMorai]

Originally posted by Crumpp
That is true.  No one is claiming the 190A was a great High Altitude performer.  Nor are they claiming it could doing anything more than what is documented.  Only in 1942 did the 190 have a commanding advantage over the Spit Mk V.  The Mk IX series and the 190A stayed as equals.

Barbi was claiming otherwise. He then, when shown his error, changes his story.

the fact is there`s no single report with known conditions that would show higher performance than 389mph for the serial Mk IX, and 391mph for the Mk VIII. Any FW 190A is faster than that by a large margin

Spitfire VIII, JL163, with a tropical air filter did 367mph and 372mph(with blanking plate) at 8300' while an A-8 using 1.65ata could just do 360mph.  (Fw data from graph dated 25.10.44)

[VO101_Isegrim]

He needs a girlfriend.

[Nashwan]

However, a complete report is known for the Mk VIII JF. 934F. It shows 391 mph obtained at FTH.

Yes, but note it was tropicalised, as was Jl 165.

Note that the tropical equipment always reduced speed. These from the Australian archives:





Maximum speed due to tropicalisation drops from 405 to 386 mph. These are speeds are with the Merlin 61.

I believe later tropical intakes had less effect on speed.

Like it or not, the JL 165 test report is the ONLY performance data referring to a serial production Mk IX LF on the highly biased 4th FG site.

How is Jl 165 a serial production plane? It was built as a Spit V with Merlin 45, had a Merlin 66 fitted, which Spit the history notes was a special engine for development of SU injection pump. After that, it was presumably modified back to a standard engine, had a "new type" tropical intake fitted, and was used by RR for trials, before being passed to A&AEE who used it for trials. How is this "normal"?

Also on  p281 Spitfire: The History, Jl 163 372 mph @ 9550 ft, Jl707 370 mph @8100 ft, both in MS gear with tropical intakes.

[Crumpp]

Gripen says

r=1,229kg/m3

R = Density of the AIR.  You got some pretty dense Atmosphere there Gripen!  Twelve hundred and twenty nine Kilograms a cubic meter! Where we flying? Venus?  The Earths core?

Here is the Correct value for R:

http://www.grc.nasa.gov/WWW/K-12/airplane/atmos.html

Let me once again repeat what NASA says:

Here is a way to determine a value for the lift coefficient. In a controlled environment (wind tunnel) we can set the velocity, density, and area and measure the lift produced.  Through division, we arrive at a value for the lift coefficient. We can then predict the lift that will be produced under a different set of velocity, density (altitude), and area conditions using the lift equation.

http://www.grc.nasa.gov/WWW/K-12/airplane/liftco.html

Using a wind tunnel under controlled conditions they can measure "L" and solve the equation from there.

Keep trying.  I am sure there will be a big financial windfall from all the money the scientific community will save when you make wind tunnels obsolete.

You might want to stick to what you know.

Crumpp

Barbi was claiming otherwise. He then, when shown his error, changes his story.

At the same time, there are altitudes in which the 190 is faster than the Spit Mk IX.

Nashwan,

400 hp input for only 30 mph speed gain with NO wieght input is definately a lot of work for a small amount return.

Examining the data, It is just like the RAF says.  There is a huge speed variation amoung Spitfires OF the same type WITH the same engine.

Here we can see in Table IV the one tested until Janurary of 1944.  The Aircraft set up is a known factor in this test.

http://www.fourthfightergroup.com/eagles/jl165.html

And a completely different speeds at the SAME altitude using another Merlin 66 (+25).
Aircraft set up is an unknown factor in this one.

http://www.fourthfightergroup.com/eagles/merlin66_18_25.jpg

Seems that all the known setups have the worst performance.  No conspiracy suspected.  It would be nice if they did so we could get some answers.

Spitfire VIII, JL163, with a tropical air filter did 367mph and 372mph(with blanking plate) at 8300' while an A-8 using 1.65ata could just do 360mph. (Fw data from graph dated 25.10.44)

They are pretty close, Milo.  I get about 364.  Use a straight edge.   Anyway according to the tactical trials the Spit VIII is just a very crappy rolling Spit Mk IX.  Again though we see the trails with a different engine from the data tables.

http://www.fourthfightergroup.com/eagles/spit8tac.html

Crumpp

[VO101_Isegrim]

That`s quite a good point about tropicalized aircraft. I wonder how more common was that on Spits, iirc Guppy said something it was added in Normandy as the low mounted carb intake took all the dust. Same thing in Russia.

How is Jl 165 a serial production plane? It was built as a Spit V with Merlin 45, had a Merlin 66 fitted, which Spit the history notes was a special engine for development of SU injection pump.

I suppose by the same logic which considers Werk.Nr.14 026 a representative serial plane, and Werk.Nr.14 513 not.

After that, it was presumably modified back to a standard engine, had a "new type" tropical intake fitted, and was used by RR for trials, before being passed to A&AEE who used it for trials. How is this "normal"?

You say just because the engine is swapped a few times in the same airframe, then it`s no longer representative of serial plane?

In any case, a large number of Mk IXs were just converted Mk Vs, nothing uncommon in that with WW2 fighters.

In any case, JL 165 was a modified Mk V airframe; this was common. It was tropicalized, that was common, too. Plus the report says it`s "a standard Spitfire IX with Merlin 66 engine, adjusted for maximum boost of +25 lb/sq.inch". I am sure w/o tropical equipment it would fare better, but doesn`t make it any less representative for the Mk IX series.

[Crumpp]

Gripen says

r=1,229kg/m3

R = Density of the AIR.  You got some pretty dense Atmosphere there Gripen!  Twelve hundred and twenty nine Kilograms a cubic meter! Where we flying? Venus?  The Earths core?  The measurement is in slugs/cu. ft.  Not Meters cubed.  Your number makes no sense.  Unless of course you were calculating the density of the Airplane itself?

Here is the Correct value for R:


http://www.grc.nasa.gov/WWW/K-12/airplane/atmos.html

Let me once again repeat what NASA says:

Here is a way to determine a value for the lift coefficient. In a controlled environment (wind tunnel) we can set the velocity, density, and area and measure the lift produced.  Through division, we arrive at a value for the lift coefficient. We can then predict the lift that will be produced under a different set of velocity, density (altitude), and area conditions using the lift equation.

http://www.grc.nasa.gov/WWW/K-12/airplane/liftco.html

Using a wind tunnel under controlled conditions they can measure "L" and solve the equation from there.

Keep trying.  I am sure there will be a big financial windfall from all the money the scientific community will save when you make wind tunnels obsolete.

You might want to stick to what you know.

Crumpp

Barbi was claiming otherwise. He then, when shown his error, changes his story.

At the same time, there are altitudes in which the 190 is faster than the Spit Mk IX.

Nashwan,

400 hp input for only 30 mph speed gain with NO weight gain is definitely a lot of work for a small amount return.

Examining the data, It is just like the RAF says.  There is a huge speed variation among Spitfires OF the same type WITH the same engine.

Here we can see in Table IV the one tested until January of 1944.  The Aircraft set up is a known factor in this test.

http://www.fourthfightergroup.com/eagles/jl165.html

And a completely different speeds at the SAME altitude using another Merlin 66 (+25).
Aircraft set up is an unknown factor in this one.

http://www.fourthfightergroup.com/eagles/merlin66_18_25.jpg

Seems that all the known setups have the worst performance.  No conspiracy suspected.  It would be nice if they did include some set up data so we could get some answers.

Spitfire VIII, JL163, with a tropical air filter did 367mph and 372mph(with blanking plate) at 8300' while an A-8 using 1.65ata could just do 360mph. (Fw data from graph dated 25.10.44)

They are pretty close, Milo.  I get about 364.  Use a straight edge.   Anyway according to the tactical trials the Spit VIII is just a very crappy rolling Spit Mk IX.  Again though we see the trails with a different engine from the data tables.

http://www.fourthfightergroup.com/eagles/spit8tac.html

Crumpp

[bozon]

extra 400 hp which is lets say 25% increase for a ~1600hp engine will not give you 25% increase in thrust. Props are inefficient and their efficiency / inefficiency changes with airspeed / density.

Props are optimized for certain conditions. outside of those, most of the added power will just go to stirring up the air. If the air speed gets really high - as in dives, the props will start acting as a break even if it has 400hp more. You have to trade-off low speed preformance (acceleration, climb) with high speed (max speed cruise). I suppose this is the reason for the 5 blades used on the XIV, they needed a different preformance envelop.

zoom climb (as vertical dives) has nothing to do with induced drag. The lift generated is close to zero (zero G) and you have just inertia (mass), drag (viscos), and prop pull. when the initial speed is high, you'll find the most important term to be m/d (mass over drag co-eff), so being heavy actually helps.

Bozon

[Crumpp]

Thanks Bozon!

Crumpp

[Angus]

Ohhh, another Spitty vs whatever thread, yummy.
(Wish I wasn't in the middle of harvesting, otherwise I'd have the time to read up a tad better)

Anyway, I see some vital point missing, possibly due to lack of some people's knowledge of the true meaning of some parameters being used.

What is induced drag?
Answer, LIFT INDUCED DRAG. in other words, drag induced by the creation of lift. A function of lift. It is influenced a tad bit by wing shape. A square wing is the worst, while an elliptical one is the best. Tapered goes between. Aspect ratio will also influence this.
A nice elliptical wing beats all others in the lift vs drag by 5 - 10%

The "other" drag is mostly referred to as parasite drag. Drag which has no relation with the generation of lift.

Something from Crumpp that also made my eyes roll a bit. That's where he was wondering about how little speed the spittie gained by a big increase in Hp.
Well, for the record, the thumb rule is that to double the speed, one needs to quadruple the power. What does 15-20% power bring at the best?
All  depends. Some airscrew will bring better speed while other bring better climb. And climb efficiency also means acceleration.
Pretty much what bozon said actually.
Anyway, goodnight gentlemen!

[Nashwan]

Seems that all the known setups have the worst performance. No conspiracy suspected.

I don't know about all, just JL 165. The other Spit tests are fairly well documented, and accepted by most people (Isegrim excluded) as being accurate.

JL 165 simply ran much worse than other tested Spit IXs, and the fact that it had a long record as a trials aircraft probably had something to do with it.

[MiloMorai]

Note that there is a note saying: External surfaces filled and polished. Not your normal condition of a Fw assigned to a JG.

Your ruler is crooked. 8300'  = 2530m.  At 2600m on one graph it could not reach 360mph. On the other 2 graphs, with very straight edges (drafting type), 362.5mph.

Not bad compared to the used and abused JL163.

At the same time, there are altitudes in which the 190 is faster than the Spit Mk IX.

Never said it wasn't. Barbi in one of his usual generalized statements claimed that the Fw was faster than the Spit.

[mw]

Great stuff Nashwan, thanks for sharing