Bf-109 vs. Spitfire....

[pbfoot]

I have what i think is another point in favour of the 109 . I was cleaning the aircraft when I looked at cleaning the glass . Now anyone who has flown or worked ATC has seen the bug mark on the glass that always forces you to takes a second look to make sure its not another aircraft. Cleaning the glass in the Spit is much harder then the 109 and impossible particularly behind the seat. Clean glass could make all the difference in a dogfight IMHO

[Negative Creep]

On the subject of glass, the Spitfire had a clearer canopy (with the exception perhaps of the Galland hood 109s) with fewer obstructions. Of course the last ones had bubble canopies as well, so that must be a point in its favour.

[claidemore]

Quite a while ago, there was a fairly lenghty debate on this thread about the climb rate of the Bf109 K4. One argument was for climb to 10k in 6.7 minutes, the other argument was for climb to 10k in 13.4 minutes. The disagreement coming from how a particular historical document was read.

Today a chart with climb rate for the Me262 was posted on another thread, indicated a 'calculated' climb rate for a 5700 kg Me262 of 10 minutes to reach 10k alt. That lines up pretty well with the 8 minutes to 10k of the F-86 Sabre jet.

That would indicate that the 109 K4 could not have climbed to 10k in 6.7 minutes, the 13.4 minute figure has to be the correct one.

___________________________________________

By the by...after reading this thread, it seems quite apparent that one on one, the choice of plane, 109 or Spit, is largely a matter of personal preference, or considering one aspect of performance to be more important than others.

However, for a large organization, given the choice of plane, the logical choice would probably have to be the Spitfire. Lower accident rate, easier to fly, able to provide maximum performance from average pilots, different weapon loadouts with little or no effect on flight characteristics, and a continued development that never had to sacrifice in one area to gain in another.

This was the case with the Israeli Air Force, they could not keep their Czech 109 deriviant the Avia S-199s operational, even though in combat with Egyptian Spitfires they came out ahead.[admittedly the "mule" Avia was not as good as a DB engined 109]

[Soren]

The only figures available for the Bf-109 K-4 in time t0 climb are Steig u. Kampfleistung figures. At SonderNotleistung (1.98ata) the Bf-109 K-4 would likely reach 10km in 9min or less.

[drgondog]

Originally Posted by Soren

The only figures available for the Bf-109 K-4 in time t0 climb are Steig u. Kampfleistung figures. At SonderNotleistung (1.98ata) the Bf-109 K-4 would likely reach 10km in 9min or less.

That is impressive..

[claidemore]

I just had a look at the graphs on Kurfurst site. As easy to read as the nose on your face, though I did have to get some German words translated. Thats one of the perks of reseraching things you find on this forum, you get to learn a little about other languages!

Two scales on the bottom, upper one is m/s, lower one is minutes. They are clearly indicated, and I did get them confused for a few seconds. Lines rising from left to right are climb time, lines rising from right to left are climb rate.

Two graphs show K4 to 10k at 13.4 minutes,the other graph shows 13 minutes even. 13 minutes even would be with MW and 1.45 ata. That would be the K4s that saw the majority of combat. The Mk IX Spitfire with Merlin 61 climbed to 30,000 ft in 9.2 minutes at combat rating and with Merlin 66 it took 8.4 minutes and the prototype 1943 Spit XIV took 8.35 minutes to 30000ft

Anyhooo...The calculated figures for 109 K4 @ 1.98 ata show a climb rate at 10k of 7.5m/s, and K4 @ 1.45 ata with 6 m/s The Spitfire MkXIV with Griffon 65 and 18lb boost shows a cllimb rate at 10k of 9.6 m/s the Spit Mk IX with Merlin 66, 18lb boots, is at 10.7m/s.

At sea level, K4 @1.98 ata 22-22.5 m/s(or 24.5-25m/s on one graph), K4 @ 1.45 ata 16.5 m/s and Spit XIV 18lb boost at 23.8 m/s, Spit XIV 21lb boost 25.9m/s and Spit IX(Merlin 66) is 23.4 m/s.
At 4500 meters, the 1.98 K4 and Spit XIV have exactly the same climb rate.
At 6700 meters, the 1.98 K4 is climbing at 16.5m/s and the Spit XIV is ahead again at 18.3m/s

(all data comes from original source documents at Kurfursts and Mike Williams sites.)


Obviously the K4 was very competitive in the climb department, particularly as the engine was approved for higher boost ratings, but the often heard statement that it was the best climbing plane of WWII seems to be erroneous.

[drgondog]

Originally Posted by claidemore

I just had a look at the graphs on Kurfurst site. As easy to read as the nose on your face, though I did have to get some German words translated. Thats one of the perks of reseraching things you find on this forum, you get to learn a little about other languages!

Two scales on the bottom, upper one is m/s, lower one is minutes. They are clearly indicated, and I did get them confused for a few seconds. Lines rising from left to right are climb time, lines rising from right to left are climb rate.

Two graphs show K4 to 10k at 13.4 minutes,the other graph shows 13 minutes even. 13 minutes even would be with MW and 1.45 ata. That would be the K4s that saw the majority of combat. The Mk IX Spitfire with Merlin 61 climbed to 30,000 ft in 9.2 minutes at combat rating and with Merlin 66 it took 8.4 minutes and the prototype 1943 Spit XIV took 8.35 minutes to 30000ft

Anyhooo...The calculated figures for 109 K4 @ 1.98 ata show a climb rate at 10k of 7.5m/s, and K4 @ 1.45 ata with 6 m/s The Spitfire MkXIV with Griffon 65 and 18lb boost shows a cllimb rate at 10k of 9.6 m/s the Spit Mk IX with Merlin 66, 18lb boots, is at 10.7m/s.

At sea level, K4 @1.98 ata 22-22.5 m/s(or 24.5-25m/s on one graph), K4 @ 1.45 ata 16.5 m/s and Spit XIV 18lb boost at 23.8 m/s, Spit XIV 21lb boost 25.9m/s and Spit IX(Merlin 66) is 23.4 m/s.
At 4500 meters, the 1.98 K4 and Spit XIV have exactly the same climb rate.
At 6700 meters, the 1.98 K4 is climbing at 16.5m/s and the Spit XIV is ahead again at 18.3m/s

(all data comes from original source documents at Kurfursts and Mike Williams sites.)


Obviously the K4 was very competitive in the climb department, particularly as the engine was approved for higher boost ratings, but the often heard statement that it was the best climbing plane of WWII seems to be erroneous.

The F8F, F7F, and P-38L will always be 'competitive', even P-51H and Ta 152

[Soren]

Claidemore,

The 13.4 & 13 min time to climb figures were achieved at Steig u. Kampfleistung, and that is clearly noted as-well.

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.

At 1.98 ata 10km would be reached in approx. 9min or less.

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

[Kurfürst]

Originally Posted by claidemore

Two graphs show K4 to 10k at 13.4 minutes,the other graph shows 13 minutes even. 13 minutes even would be with MW and 1.45 ata. That would be the K4s that saw the majority of combat.

A small correction : 1,45 ata was a 30-minute rating for the DB 605D ie. G-10 and K-4, and no MW 50 was injected at this setting. This was of course not the maxmum output of the engine, rather an (rough) equivalent of what the USAAF called 15-min Military and the RAF as 'Normal' rating. The equivalent of thE USAAF`s WEP or the RAF`s 'combat' rating is the Sondernnotleistung rating at 1,75/1,80/1,98ata (depending on engine model, ie. DM or DB/DC).

At 1,98ata maximum WEP I calculate 8.36 mins required to 30 000 feet, I didn`t do it with 1,8ata rating, but its fairly easy to do by the climb graphs.

[claidemore]

Originally Posted by Kurfürst

A small correction : 1,45 ata was a 30-minute rating for the DB 605D ie. G-10 and K-4, and no MW 50 was injected at this setting. This was of course not the maxmum output of the engine, rather an (rough) equivalent of what the USAAF called 15-min Military and the RAF as 'Normal' rating. The equivalent of thE USAAF`s WEP or the RAF`s 'combat' rating is the Sondernnotleistung rating at 1,75/1,80/1,98ata (depending on engine model, ie. DM or DB/DC).

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?

[claidemore]

Originally Posted by Soren

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]

Originally Posted by claidemore

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]

Originally Posted by 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.

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.