Bf-109 vs. Spitfire....

[claidemore]

Claidemore,

The climb rate figures at SL is with radiator flaps open, which has a very negative effect on climb performance.

At 1.98ata and with closed radiators the max climb rate of the K-4 is above 28 m/s, or 5,500 + ft/min.

So it's quite true that the Bf-109 K-4 was the best piston engined climber of WW2.

I don't read German, and my translations are crude, so I didn't see anywhere where it indicated open radiator,but it makes sense that they would be open, why burn out a a test engine?
The Spit XIV tests also used open radiators, so the comparison would be the same. The 8.35 time to 30k on a Spit XIV was at 18lbs boost btw, at 21 or 25 lbs, it would be even less.

Spitfire Mk XXI was climbing to 30k in 7.85 minutes with Griffon 61 @ 18lb boost (1943 test). Spit 21s were delivered to squadron in Jan 45, and first operational use April 10, 45, but saw no combat.

I don't see any K4 graphs indicating 28m/s? is that a calculated rate? Or where did you get that figure from?

Comparing apples to apples, if you close the radiators on a Spit XIV as well, wouldn't it still have the same advantage as it had when both planes had radiators open?

Spit IX 25lb boost with rad open did 5080 fps at sea level, Spit VIII did 5580 @ sea level.

I know it has been generally accepted that the K4 achieved the max climb rate for a prop plane in WWII. I always thought it seemed odd that a higher wing loaded, lower hp/lb plane could have higher climb rate, and always attributed it to some unknown (to me) engineering or design feat in the closing months of the war. After this bit of research I believe the numbers show that the K4 was actually a very close second to the latest Spitfire Mks, definately when comparing operational planes, but also for the non-operational and test planes.

I know this might end up a double post, but seemed the eaiest way to reply to two people.

 

[Kurfürst]

Thanks, you are right, the heading on the graph indicates MW , but the 1.45 rated lines do not show it's use.
So, am I correct now in understanding that MW was only used on 1.75 ata or higher engines?

Yup, MW-50 injection only occured at the maximum ouput regime on all MW-50 Bf 109s that saw operational service.

 

[Soren]

Claidemore,

First of all 10km is 32,800 ft, and the Spitfire Mk.XIV could barely make that in 10min.

The light Spitfire VIII test-bed JF.319 made it to 32,000 ft in 9.25min, missing another 800 ft to reach 10km.

At 1.98ata with open radiators the K-4's time to climb to 10km is around 9.2 min, calculated. With rads closed it's below 9min, probably around 8.5min.

Finally, at 3,364 kg and with 1,975 HP I believe the Bf-109 K-4 is the piston engined fighter of WW2 with the highest power to weight ratio.

 

[claidemore]

Claidemore,

First of all 10km is 32,800 ft, and the Spitfire Mk.XIV could barely make that in 10min.

The light Spitfire VIII test-bed JF.319 made it to 32,000 ft in 9.25min, missing another 800 ft to reach 10km.

At 1.98ata with open radiators the K-4's time to climb to 10km is around 9.2 min, calculated. With rads closed it's below 9min, probably around 8.5min.

Finally, at 3,364 kg and with 1,975 HP I believe the Bf-109 K-4 is the piston engined fighter of WW2 with the highest power to weight ratio.

According to this chart:
http://www.spitfireperformance.com/jf319climb.gif
Spit XIV, 18lbs boost reached 32800 ft in 9.6 minutes. Tested, not calculated
21 lbs boost is going to be less.

Since the times claimed for the K4 are calculated, I thought I would try to duplicate those calculations.

When I calculated climb times using climb rate graphs for 1.98ata K4(with MW50) and did the same calculations for the 18lb boost XIV.... I got 9.2 min for XIV (which agrees pretty close with the graph and chart mentioned above) but I got 10.3 minutes for K4.

Obviously my calculations didn't come up with the same number for the 109 as yours. Maybe I'm not using the right method to calculate it, but since I used the same calculations for both graphs, the results are indicative of the difference between the planes performance.

If your calculations of climb time using climb rate graphs shows 9.2 min for the K4, what would the same calculations show for the Spit XIV using it's climb rate graphs?


Agree with the hp per weight; on the 109K4 I get 3.78 lbs / hp and 4.14 for Spit XIV. Of course wing loading is 43lbs/sq ft for K4 and the Spit XIV is 35lbs/sq ft.

 

[Soren]

How did you calculate your time to climb figures Claidemore ? Did you include engine performance figures ? did you take into account that the Bf-109 K-4 at 1,325 Hp reaches 10km in 13min ?

Also wing-loading doesn't matter, lift loading does, and with slats in the K-4 still has a higher CL, 1.48 vs the Spitfire's 1.36.

 

[Hop]

Standard German testing procedure for the 109 was to open the radiators about half way. What evidence do you have that the figures for the K4 are for fully open radiators?

Against that, standard RAF practice was to override the automatic control and open the radiators fully.

According to this chart:
http://www.spitfireperformance.com/jf319climb.gif
Spit XIV, 18lbs boost reached 32800 ft in 9.6 minutes. Tested, not calculated
21 lbs boost is going to be less.

JF319 was one of the prototype Spitfire XIVs. It had lower supercharger gearing for MS supercharger setting. That means it delivered more power at very low altitude, but less at medium altitude.

As you can see, JF319 maintains maximum climb rate only up to 2,000 ft, above that the climb drops away rapidly.

Production Spitfire XIVs had higher gearing in MS supercharger, meaning they produced less power, but to a higher altitude. See http://www.spitfireperformance.com/spit14climbchart.jpg

If you look at the differences, the production gearing gives a lower climb rate below 3,000 ft, but higher climb rates up to about 14,000 ft. The net result is the production plane climbs to altitude faster.

Looking at the production Spitfire XIV, the first 9,000 ft are covered at an average of 4750 ft/min. That means 1.89 minutes to 9,000 ft.

The next 5,000 ft are covered at an average of 4,050 ft/min, which means 1.23 mins.

The next 8,000 ft average 3,675 ft/min, for 2.18 mins.

The last 10,800 ft average just over 2,800 ft/min, but I'll round it down. That's 3.86 mins.

Total time to 32,800 ft is 9.16 minutes. That's for the Spitfire running at 18 lbs boost.


For the 109K4, at 1.98 ata, the first 800m is covered at an average of 24.7 m/s. That's 32.4 secs.

The 4,600m average 22.5 m/s. 204.4 secs

The next 600m are at 19.3 m/s. 31.1 secs.

The last 4,000m average 12.5 m/s. 320 secs.

Total to 10,000m is 587.9 secs, which is 9.8 minutes.

Now those two comparisons are not quite fair. The 109 is running at 1.98ata, which may have been used in service in the last few months of the war. The Spitfire is running 18 lbs boost, not the 21 lbs that was used late war.

The 109 almost certainly has half open radiators. The Spitfire fully open.

Even the Spitfire LF VIII, running at 18 lbs boost, a mid 1943 aircraft, has a similar time to 10,000m as the 109K4 running at 1.98 ata, and the Spitfire VIII doesn't climb quite as well as the Spitfire IX.

I don't see any K4 graphs indicating 28m/s? is that a calculated rate? Or where did you get that figure from?

He made it up.

I know it has been generally accepted that the K4 achieved the max climb rate for a prop plane in WWII.

William Green started that. He misread a climb graph that shows the K4 at climb and combat power (about 1.45 ata iirc). Instead of the 1 square = 2 mins that the graph actually shows, Green seems to have assumed 1 square = 1 min, which doubled the actual climb rate (and halved the time to climb).

Soren seems to have made the same mistake earlier in this thread.

 

[Soren]

I haven't made anything up Hop (Unlike you), I calculated the time to climb figure.

The German figures are with radiators open (never said fully, again something you made up), that's fact, std. procedure.

The Bf-109 K-4 takes 13min to 32,800 ft with just 1,325 HP and the std. prop (0.8 min faster than with the Dünnblatt prop), that's pretty darn fast for such a low powerrating. At 1.98ata power is increased to 1,975 HP, giving quite an increase in climb rate.

With the experimental Dünnblatt prop max climb rate is 25 m/s, with the thicker std. prop alone this figure will increase quite significantly and with closed rads it will increase even further.

So from this I calculated a time to climb 32,800 ft in less than 9min at 1.98ata, which is being very conservative.

Even at 25 lbs/sq.in. boost the Spitfire Mk.IX needs well over 9min's to reach 32,800 ft, over 10 min to be correct.

Ofcourse you being the hardcore Spitfire fan that you are you will always try to downplay the performance of the 109, despite the fact that the 109 throughout its different versions in actuality outclimbed the contemporary Spitfire quite easily. The Bf-109 also benefitted from better performance for the given HP compared to the Spitfire, again something you'll try to dispute.

But heck I'm looking forward to you disputing this Hop, it's always very entertaining.

 

[Kurfürst]

Thing is though, all these figures vary greatly in practice - raditor position is considerable source of drag for example, was usually assumed to be ca. half-open up to rated altitude in German calculations, and gradually closing above that to fully closed at the ceiling, but it was noted that this is somewhat pessimistic as the automatically controlled radiator flaps would, in practice, close 1-1.5 km above rated altitude, with reduced drag and improved climb; another aspect was that while the radiator flaps could be overridden in the 109F-K, and closed at will, there was no such possibility on the later Spitfires, and therefore the flap position came down to the current engine and outside temperature conditions; I believe these figures for the Spitfires all assume an optimum change between MS and FS gears, ie. as opposed to real life where it was not so optimal, done by automatics with some 'lag' and there was no possibilty for manual operation - the result in practice was that the engine continued to run in MS gear and deliver less power for a while at an altitude band where it would have been more advantageous to run in FS gear; and all these hotly debated figures refer to maximum power, wheter you call it 'Combat Power', or 'Sondernotleistung'. Now, 'Combat Power' was cleared for 5 minutes of use at a time for either the Merlin or the Griffon engine, 'Sondernotleistung' on the other hand was cleared for 10 minutes for the DB 605D. That may be a problem in the former case, for climbs of ~10 minutes duration, when you are only cleared for 5 minutes.

And so on. The point is, these values were far from set in stone. They would vary considerably even amongst the exactly same types, due to differences in serial production quality between individual planes.

 

[Hop]

So you knew the radiators were half open, and yet you re-"calculated" 109 performance for fully closed radiators, to compare with the Spitfire with fully open radiators?

And you accuse me of trying to downplay the performance of the 109?

So from this I calculated a time to climb 32,800 ft in less than 9min at 1.98ata, which is being very conservative.

And you think a 109 can climb at 1.98 ata for close to 10 minutes with the radiators fully closed, without overheating the engine?

Ofcourse you being the hardcore Spitfire fan that you are you will always try to downplay the performance of the 109,

Wait a second. I compared a 109 running at 1.98 ata, which may have been used in the last couple of months of the war, against Spitfires running at 18 lbs. I didn't use the 21/25 lbs figures that were used before the 109 started running at 1.98 ata.

I also compared a Spitfire running with fully open radiators, against a 109 with half open radiators.

Yet I am trying to downplay the performance? Note how I didn't re-"calculate" Spitfire performance to closed radiators.

despite the fact that the 109 throughout its different versions in actuality outclimbed the contemporary Spitfire quite easily.

Well, not really. The Spitfire I/109E4 had similar climb rates. The Spitfire V/109F matchup probably goes to the 109 for most of the time. With the introduction of the Merlin 63/66/70 in the Spitfire, the Spitfire outclimbed the 109, and that remained the position for the rest of the war.

Just look how you have had to rearrange the figures to get the 109K4 climbing better than the Spitfire XIV. You compare a vanilla Spitfire XIV with fully open radiators against a 109 with fully closed radiators, running on a power setting it might have used in the last few months of the war.

The Bf-109 also benefitted from better performance for the given HP compared to the Spitfire, again something you'll try to dispute.

For most of the war, yes. No surprise there, it was a smaller plane, and had to make do with lower hp engines.

Even at 25 lbs/sq.in. boost the Spitfire Mk.IX needs well over 9min's to reach 32,800 ft, over 10 min to be correct.

With fully open radiators. Why the double standard? Why pick the figures for the Spitfire with fully open rads, and make up figures for the 109 with fully closed rads?

 

[Soren]

No Hop, I used figures with fully closed rads for the Spitfire and time to climb 32,800 ft still took over 10min, sorry to disappoint you.

 

[claidemore]

Hi Soren.

I used the graph with K4 climb rates and times, the one dated 19/1/45 with a stamped number 5026\ 28. It has five different climb rates, and two climb times, one for K4 and K6 respectively. I used the climb rate lines, doing a calculation for each rise of 500 meters using an average climb rate for the beginning and end of each 500 meter segment. LOL crude, slow, manual, amateur method I know!

I calculated the K4 @ 1.45 ata and got a figure of 13.5 minutes which agrees exactly with the climb time for that plane on that graph. So my calculations are very close. Did the same for the 1.98 ata line on that graph and got 10.3 minutes.

Using the same method for calculating the Spit XIV 18lb boost, I get a time to 32,800 ft of 9.8 minutes.

I think whatever formula somebody else uses to calculate climb time on the K4, it needs to be 'proofed' against the 1.45 K4 which has a plotted climb time. Then it needs to be done on the Spit XIV as well to proove it. Then we know that we have figures that can be compared.

I believe wing loading is directly related to lift? Slats would not be open during a climb, so I don't know how they would have any effect here.

 

[Hop]

No Hop, I used figures with fully closed rads for the Spitfire and time to climb 32,800 ft still took over 10min, sorry to disappoint you.

I'm sorry, could you point me to that data?

Rolls Royce tests on Jl165:
http://www.spitfireperformance.com/jl165rrclimb.jpg

0 - 5,000 ft at an average of 5,350 ft/min - 0.93 mins
5 - 11,000 ft, 5,080 ft/min - 1.18 mins
11 - 32,800 ft, 3,450 ft/min - 6.32 mins

Total - 8.43 mins

A&AEE test on Jl165:
Spitfire IX Trials at +25 boost

FS climb with radiator flaps closed - 8.29 mins (point 29, not 29 secs) to 30,000 ft.

How long from 30 - 32,800 ft?

First method is to extrapolate from the graph of Jl165. Climb rate peaked at 4,750 ft/min at 11,400ft. It declined up to 32,800 ft. That's 21,400 ft, the halfway point would be 10,700, add it to 11,400 and the halfway point for the last stage is 22,100 ft. Climb rate at 22,100 ft is 3,100 ft/min.

So the climb above 11,400 ft is 21,400ft at an average of 3,100 ft/min, 6.9 mins. It took 2.39 mins to reach 11,400 ft, so the total is 9.29 mins

The other way to calculate how long it took to climb from 30 to 32,800 ft is to compare with other similar Spitfires (VIIIs or IXs with Merlin 66).

BS 543 took about 1.5 mins, which would make the total 9.79 mins
JF934 took about 1.2 mins, which would make the total 9.49 mins.

The final way is simply to extend the line on the graph. That looks like 1,750 ft/min for the last 2,800 ft, which is 1.6 mins. Total time 9.89 mins

Try as I might, I can't find any figures that show more than 10 minutes to 32,800 ft. Even for the A&AEE test of Jl165, where it performed worse than it had some months earlier at RR. The figures range from a low of 8.43 minutes to a high of 9.89 minutes. How can that equal "over 10 minutes"?

I used the climb rate lines, doing a calculation for each rise of 500 meters using an average climb rate for the beginning and end of each 500 meter segment. LOL crude, slow, manual, amateur method I know!

There's no need to do small segments, just find the halfway point along each straight line.

For example, if the plane climbs at 20 m/s at 1,000, and 10 m/s at 5,000m, then the halfway point is 3,000m. Read off the climb rate at 3,000m, and apply that rate for the entire 4,000m.

It's more accurate, and with most aircraft much quicker, because you typically have 5 or less segments to do, for any altitude.

 

[claidemore]

There's no need to do small segments, just find the halfway point along each straight line.

For example, if the plane climbs at 20 m/s at 1,000, and 10 m/s at 5,000m, then the halfway point is 3,000m. Read off the climb rate at 3,000m, and apply that rate for the entire 4,000m.

It's more accurate, and with most aircraft much quicker, because you typically have 5 or less segments to do, for any altitude.

Rgr that. Wife hates it when I spend 1/2 hour plotting figues.

For me, this project and discussion has shown that the later marks of Spitfire had a better climb rate than the 109K4, not only against the planes that saw operational service, but also against the top available tested plane data.

109K4 is still the winner for hp/weight, AFAIK. Closest I found was a Yak 3 with VK107 engine at 3.79 lbs/hp compared to the 3/74 for the 109K4.

A little off topic, but the 107 engined Yak3 is always listed as being too late to see combat in WWII.

He was the commander of 897 IAP.
Karavay and some other pilots went to Zavod no.31 at Tbilisi for planes and they found some new models of Yak fighters.
They took possession of them and brought to the unit by evading the usual procedures.
Karavay used the plane in fights above Hungary. He shot down one Bf-109 on 23.03.1945 above Mór and one more above lake Balaton on 22.04.1945 while flying this machine. (Yak 3 VK107A)

 

[Glider]

What I find interesting is how well the Spit IX did. A 1942 design with power settings that were available (I think) from early 1944, holding its own against a new fighter (redesigned 109K) using power settings that were in use only in the last few months of the war.

Not bad

 

[claidemore]

Agreed.

I was just reading about the Israeli Spitfires the other day, four Spit IXs shot down three British Spit XVIII's and one Tempest V. Obviously the Spit IX had a lot going for it.

 

[Hop]

What I find interesting is how well the Spit IX did. A 1942 design with power settings that were available (I think) from early 1944,

18 lbs boost was introduced for the Spitfire IX with the Merlin 63 engine. I believe EN306 was the first, first flight 13 Jan 1943.

 

[Glider]

18 lbs boost was introduced for the Spitfire IX with the Merlin 63 engine. I believe EN306 was the first, first flight 13 Jan 1943.

Thanks for that. My comment was based on the 25lb boost but I wondered about the 18lb boost.

 

[Kurfürst]

And you think a 109 can climb at 1.98 ata for close to 10 minutes with the radiators fully closed, without overheating the engine?

I would not rule out the possibility, given the engines thermal output (simply to put, the DB 605D is not putting out much heat thanks to MW50s cooling qualities), and the generous coolant and oil radiator capacity of the aircraft.

Wait a second. I compared a 109 running at 1.98 ata, which may have been used in the last couple of months of the war, against Spitfires running at 18 lbs. I didn't use the 21/25 lbs figures that were used before the 109 started running at 1.98 ata.

Well the +25 lbs rating was limited to Service TRIALS before 1.98ata was introduced, the +21 rating was an act of desperation in the summer of 1944, and its use was limited to V-1 patrols; when these ended, they reverted to +18.

In fact, the service introduction of +25 lbs (which was later recalled a month or so later and they reverted to +18 because of accidents with the new rating and fuel), and possibly (and theres very little evidence to it, actually) +21 for the Griffon, too occured at the same time as the introduction of 1.98ata, in the early months of 1945.

These are all 1945 ratings for all practical purposes.

I also compared a Spitfire running with fully open radiators, against a 109 with half open radiators.

Now THAT is just muddying the water... the 'fully open' radiators on the Spitfire - as you are well aware - meant actually less exit area on the Spitfire than on the 109, not to mention all this 'fully open' and 'half open' stencils are applied by you only, the RAF and the LW never used such terms, what you re-named was actually the standard in the two airforces for climb rates.

Well, not really. The Spitfire I/109E4 had similar climb rates. The Spitfire V/109F matchup probably goes to the 109 for most of the time. With the introduction of the Merlin 63/66/70 in the Spitfire, the Spitfire outclimbed the 109, and that remained the position for the rest of the war.

That latter a very bold and doubtful statment IMHO.

Just look how you have had to rearrange the figures to get the 109K4 climbing better than the Spitfire XIV. You compare a vanilla Spitfire XIV with fully open radiators against a 109 with fully closed radiators, running on a power setting it might have used in the last few months of the war.

You are being unfair here. Simply there isnt any other figures for the Spitfire XIV, the calculated figures we have for the type only exist for +18 lbs, there is none for +21 which the XIV might have used in the last few months of the war in air-to-air combat, and all the details for these figures are missing, we dont know what kind of airframe conditions (polished, good, bad, standard or not) the figures relate to, nor if the figures are understood for open or closed radiators.

Oddly enough, you are complaining about that he is not making up figures for a higher boost, and not making up the conditions of the aircraft..

I'm sorry, could you point me to that data?

Rolls Royce tests on Jl165:
http://www.spitfireperformance.com/jl165rrclimb.jpg

0 - 5,000 ft at an average of 5,350 ft/min - 0.93 mins
5 - 11,000 ft, 5,080 ft/min - 1.18 mins
11 - 32,800 ft, 3,450 ft/min - 6.32 mins

Total - 8.43 mins

Well, looking at this climb chart is says the aircraft was tested at 7234 lbs. The normal takeoff weight of the Mk IX was apprx. 7450 lbs.

Is it a surprise that a lightly loaded aircraft missing 220 lbs weight climbs faster than if it would have been fully loaded..?

 

[Kurfürst]

What I find interesting is how well the Spit IX did. A 1942 design with power settings that were available (I think) from early 1944, holding its own against a new fighter (redesigned 109K) using power settings that were in use only in the last few months of the war.

Not bad

In the climb department, the IX was pretty good. Holding its own... well, ask Clostermann about it. The IX may have had a similiar climb rate as late war 109s (or the late war XIVs), but it was just hopelessly slower than either the XIV, Tempest or the Mustang or the 109K for that matter; the latter two could cruise faster at altitude than the IX would manage at full throttle.

It was a bit like the Zero in the Pacific by 1944; manouverable, but simply too slow.

 

[Glider]

As a matter of interest what was the cruising speed of the 109K and at what altitude are you talking about?
Just a thought but if the 109K could cruise faster than a Spitfire at max speed then why did they find it so difficult to intercept allied PR planes such as the SPit or the Mossie

Re the Zero I do find that amusing, didn't know they went over 400mph.