Which is better: P-47 or Fw-190?

[DerAdlerIstGelandet]

Yeap that is another way of putting it.

[Soren]

I can see we missunderstood each other, "Again".

I'm not sure what your point is with respect to your saying, "Now what part of this did you miss?"

As a reminder, you said, "But how does this explain a 3,000lbs drop in the "normal" loaded weight figure?"

Which was pointed at the official books about the P-47, not the manual. What I couldnt understand was how so many serious researchers got it so horribly wrong, and I still don't understand how.

I pointed out that the reduction in weight was really about 2,500lbs (2,554lbs to be exact) to which you replied that even that reduction was, "... equally unrealistic... "

It is unrealistic, as engineers would never reduce or add to the normal loaded weight figures in flight manuals. (Performance figures is another matter)

I then responded that, "I have provided you with the pilot's manual itself Soren. It is what it is and that is a primary source of reliable data. That being the case, we can now assume that the 2,554lb (aka 2,500lb) drop in weight is not "unrealistic" but fact."

Presumably yes, but I'm just abit puzzled by the fact that so many researchers got it so horribly wrong, thats all.

Thus, I was under the impression that you found the 2,554lb (which you had represented to be 3,000lb) reduction of weight "unrealistic" per your own statement.

I do find it unrealistic, as that manual 'should' be correct. The engineers would never play with the weight figures, however with authors your just never 100% sure. But that 'so many' serious researchers should be wrong about the weight figures, seems quite strange to me, and makes the manual seem a little fishy, as the researchers presumably relied on manuals to get their figures themselves.

If that is not the case and you no longer or otherwise do not find the reduction in weight "unrealistic," in light of the data presented directly from the pilot's manual, then I apologize and am pleased that we are now in agreement.

Apology accepted. Now I will apologize for not making myself perfectly clear on what really meant.

Now, when I quoted you as saying, ""Engineers might add limiting factors for whatever weight-configuration, but they wouldnt alter the "Normal loaded" weight figure, as thats impossible.", I was responding to Flyboy. So to quote you again, "What part of this did you miss?"

Probably all of it, I was in quite a hurry when I read it.

I think my point about degradation of climb rate from 0ft to 5,000ft still stands. As I clearly pointed out, "I gave the data for the Spitfire Mk. IX only to drive home my point." Thus it was just an illustrative example.

Ok, I'll explain why not below.

Your quoted specifications appear on the website as:

Max rate of climb at full throttle in M.S. supercharger gear 4,470 ft/min. (at 11,200ft.)

Max rate of climb at full throttle in F.S. supercharger gear 3,400 ft/min. (at 22,700ft.)

I do not understand your reference to "=Initial climb rate." I'm not sure how this relates to my point concerning the degradation of climb rate from 0ft to 5,000ft which again was:

Spitfire Mk. IX @ 25lbs of boost

Climb rate at 0ft - 5,740ft.

Climb rate at 5,000ft - 5,080ft.

At any rate, if my point, as opposed to my example, is flawed, please explain. Otherwise, it is the point as opposed to the example that would apply to the "M" model's actual initial vs. "initial at 5,000ft" climb rate.

Look at my presented figures and then look at yours, then you will see that mine are presented as Max climb rate's at certain altitudes, yours are not. And as we both know an a/c has different speeds and climb rates at different altitudes.

Now the word "Initial" virtually means "beginning" or "Start of", and at 5,000ft the -47M will have a climb rate of 3,500ft/min in the beginning or at "the start of" the climb = the max climb rate at that altitude.

Also you will note the alt difference between my figures is 10,500ft(11,200-22,700ft) but only 970ft/min in climb rate, while the difference between your figures is much higher considering its a lower alt difference "5,000ft".

Take for example this quote from the same site:

Rate of climb at Sea level:
Spitfire IX BS. 543 Merlin 66= 4620 ft/min.
Spitfire IX BS. 551 Merlin 70= 4390 ft/min.

Spit IX Merlin 66: Rate of climb at full throttle height in M.S. supercharger gear= 4700 ft/min at 7000 ft.
Spit IX Merlin 70: Rate of climb at full throttle height in M.S. supercharger gear= 4530 ft/min. at 11,900 ft.
Spit IX Merlin 66: Rate of climb at full throttle height in F.S. supercharger gear= 3860 ft/min. at 18,000 ft.
Spit IX Merlin 70: Rate of climb at full throttle height in F.S. supercharger gear= 3480 ft/min. at 24,700 ft.

Now the if we were to follow your example/point the Spit IX would suddenly be climbing faster than from sea level when it reaches 7000ft, which we both know isn't the case.

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

Well this is all I have time for right now, but I'll be back later.
And please excuse any mess in the writing, as I was in quite a hurry writing this.

[DAVIDICUS]

"Look at my presented figures and then look at yours, then you will see that mine are presented as Max climb rate's at certain altitudes, yours are not."

I do see this but am not sure what the consequence is. Under what circumstances would you present "climb rate" if not intending to, present "maximum climb rate?" Isn't that just understood? What value would it be to have a chart that lists the "climb rate" at say 5,000ft at a lower speed and angle of climb and a "climb rate" at say 10,000ft at a higher speed and angle of climb? Or for that matter, why would anyone be interested in a climb rate that reflects a slow leisurely climb? I believe this is why we can assume that the data I provided was in fact for maximum climb rate (or are you saying that a Mk. IX at 25lbs of boost could do better?)

In keeping with this, the data I provided was in fact for maximum climb rate even though it didn't expressly say "maximum.":

Spitfire Mk. IX @ 25lbs of boost

Climb rate at 0ft - 5,740ft.

Climb rate at 5,000ft - 5,080ft.

I agree with you that, "Now the word "Initial" virtually means "beginning" or "Start of", and at 5,000ft the -47M will have a climb rate of 3,500ft/min in the beginning or at "the start of" the climb = the max climb rate at that altitude."

That being the case, when you presented P-47M climb data as "initial climb at 5,000ft" you were indeed presenting the "maximum climb rate at that (5,000ft) altitude."

Therein lies my point. I am concerned that if we compare the initial climb rate of the "N" model at a far lower altitude than 5,000ft, say sea level, we would be comparing apples to oranges. If the P-47M can start a climb at 5,000ft at a rate of climb of 3,500fpm (again, I am just assuming this figure for purposes of this discussion), then the P-47N, to be fair, would need to be tested in its start of its climb at 5,000ft as well.

If we assume a 3,500fpm maximum initial climb rate at 5,000ft for the "M" model, it stands to reason that that same "M" model aircraft could deliver a higher maximum initial rate of climb at sea level and a lower maximum initial rate of climb at 10,000ft and still lower at 20,000ft. Had you presented a maximum initial climb rate at 10,000ft or 20,000ft, I would thus be making the same argument.

To further the point of this example, it should be quite obvious to see that the "M" would have a higher "initial climb rate" at 5,000ft than at 20,000ft and that it would not be helpful to use the 20,000ft figure simply in order to depress the estimates of the "M" model's initial climb rate so that the "N" model's initial climb rate would be similarly depressed in a debate where you have taken the position that the climb rates are lower. Likewise, the 5,000ft figure you are in fact using is lower than the figure would be at sea level.

Hence, when I speak of "maximum initial climb rate" I want to be comparing apples to apples by comparing "maximum initial climb rates" at the same altitude in which the maximum climb rate can be achieved.

If the "M" model can pull 3,500fpm at 5,000ft, it could pull better than that at sea level. If we compare the "M" model at 5,000ft and the "N" model at sea level, we could very well see the "N" model's climb rate exceed the "M" model's 5,000ft maximum climb rate.

[Soren]

I see what you mean DAVID, but not all a/c will have better climb rates down low though, but thats another matter.

However since the -47N and -47M used the same C engine, their engine performance curve at altitude should be the same. So 'if' the C engine has better performance down at sea-level than at 5,000ft, then I agree the climb rate should be slightly better at sea-level than at 5,000ft.

So what we need is a performance curve for the R-2800-57 "C" at different altitudes.

[FLYBOYJ]

R-2800 INFO!

Here are the FAA Type Certificate Data Sheets (TCDS) for the civilian versions of the P&W R-2800. I think you might be able to extract some information from these:

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/137c165bea6c0fae8525670d0060671b/$FILE/E-264.pdf

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/28543f501b3e3cee8525670d0060471a/$FILE/E-231.pdf

[DAVIDICUS]

I recall that the climb rates for the F6F and F4U are linear in inverse proportion to the increase in altitude and thus believe that the P-47 would follow in kind.

I guess we can argue about what "slightly better" means.

As I stated earlier, "If the 3,500fpm figure at 5,000ft is correct, then the initial climb rate would be more like 3,600-3,650fpm (maybe as high as 3,700fpm) ..."

When I said "initial climb rate" above, I was indeed talking about the increase in climb rate that would be realized at sea level which is why I pointed out that the 3,500fpm initial climb rate would be incorrect as it is at 5,000ft. (Admittedly I could have been clearer. )

When you first represented the FW-190-D-9's climb rate, you said," The Fw-190D-9's climb rate was 3,660ft/min." That's it. No altitude specified. Naturally, I assumed that that was the highest numerical climb rate figure attainable by the Focke Wulf and since we were comparing against the P-47N, wished to use the highest numerical climb rate figure achievable as well, which I just assumed to be sea level for both planes.

Since we were extrapolating from the "M" model data to better understand the "N" model data, the "at 5,000ft" issue was of concern for me.

At any rate, I am still hopeful that I can obtain that Republic Aviation documentation on the "M" and "N" performance.

[FLYBOYJ]

Originally Posted by DAVIDICUS

I recall that the climb rates for the F6F and F4U are linear in inverse proportion to the increase in altitude and thus believe that the P-47 would follow in kind.

That's true for any recip aircraft.

[DAVIDICUS]

Maybe you could help us (or at least me) with that task Flyboy.

What are the fifferences between the "C" series 57 engine and the version of the engines presented in that data?

What conclusions do you infer from the presented data?

[FLYBOYJ]

Originally Posted by DAVIDICUS

Maybe you could help us (or at least me) with that task Flyboy.

What are the fifferences between the "C" series 57 engine and the version of the engines presented in that data?

What conclusions do you infer from the presented data?

As you folks been discussing this, I've been trying to find that out. In those 2 links I gave you it gives a break down of the 2800 civilian versions, but the -97 is shown on the 2nd TCDS. Usually a letter after an engine model designator has to do with an accessory, like a generator or supercharger. The -57 seems to be exclusive to the P-47, the "C" might designate clockwise for either the engine or for an engine accessory.

I think when comparing the climb performance of different aircraft you have to factor in a given altitude, rpm, mp and fpm. As stated, climb performance is usually inversely linear (supercharging may change this a bit, but the bottom line eventually climb perfomance will go to hell at altitude, supercharger or not). Just to say that an aircraft will climb at 3700 fpm doesn't mean much unless you could determine at what altitude that's at. To make it more complicated, that climb performance will change as density altitude changes(altitude with temp factored in). Max climb performance should be shown starting at SL, 59F at 29.92hg - that's standard temp and pressure and usually performance charts are built around that base.

[Soren]

I have this for the P-47D-35 which clearly states the "Max" initial climb rate:

P-47D-35-RA
Max. initial climb: 3,120 ft./min.

And it seems perfectly reasonable that the -47M was about 400fpm faster than the D-35.

[FLYBOYJ]

I would assume that's at SL

[DAVIDICUS]

Thanks Flyboy.

Let me ask for your input as you have some insight here. If we were to assume that the "M" model could climb at a rate of 3,500fpm at 5,000ft, what do you think the climb rate would be at sea level?

I know that we are just estimating or even guesstimating.

[FLYBOYJ]

I would "guess" about 3800 fpm, 59F, 29.92" I know its supposed to reach 15,000 in 4.9 seconds, so that would average about right!

[Soren]

So we can all agree that the -47M wont reach 20,000ft in 4.75min now ?

[DAVIDICUS]

Interesting.

The 4.9 min figure you are using as a backdrop is, I assume, the data I presented from: http://www.geocities.com/pentagon/qu...485/P-47M.html

Climb, at max. gross weight (including three 75 gallon drop tanks): 4.9 minutes to 15,000 feet at 2,600 rpm (1700 hp). Reportedly, the "M" could reach 20,000 feet in 5.7 minutes at military power (2,100 hp @ 2,800 rpm). 20,000 feet in 4.75 minutes in WEP (2,800 hp @ 2,800 rpm). This is with full internal fuel and ammo. No external stores or drop tanks. In other words, normal load, clean configuration.

That data has been the subject of the great debate (of epic proportions really ) between Soren and myself on this thread.

While we are on the subject, what do you think of the 4.75min to 20,000ft at WEP figure?

Does it appear plausible or does it strike you, as Soren would say, as "an insane number"?