FIGHTER COMBAT COMPARISON No.2: Bf109E-3 vs Spitfire MkI

[krieghund]

I have been searching high and low for the companion volume to my FIGHTER COMBAT COMPARISON No.1: P-40C versus A6M2 Zero.

I found this excerpt online at IL-2 and tried to contact the poster with no results so here it is for your information.

FIGHTER COMBAT COMPARISON No.2: Messerschmitt Bf109E-3 versus Supermarine Spitfire Mk.IA, Tacitus Publications, M Rubenstein, 1973. The data were generated by a USAF a/c performance computer modeling program developed by John Boyd during his tenure at the USAF Fighter School, Nellis AFB, Las Vegas NV. This is the same program which demonstrated the combat superiority of Russian fighter aircraft over their US counterparts and was also employed in the conception and design of the F16.

Aircraft Design Comparison

..................Bf109E-3............Spitfire Mk.IA

Engine............DB601Aa.............R/R Merlin III
Output (t/o).... [email protected]@3000rpm
[email protected]@3000rpm
..................@14765ft (no ram)...@16250ft (no ram)
Red Gear Ratio....0.53:1..............0.477:1
Ram Recovery......37.5%...............50%
Propeller.........3-blade VDM.........3-blade Rotol
..................constant speed......constant speed
Empty Weight......4189 lbs............4810 lbs
Normal Loaded.....5875 lbs............6200 lbs
Combat Weight.....5479 lbs............5811 lbs
Length............28ft 4.25 in........29ft 11in
Span..............32ft 4.50in.........36ft 10in
Height............8ft 2.33in..........12ft 7.75in
Wing Area.........176.53 sq ft........242 sq ft
Aspect Ratio......5.94................5.61
Wing Loading......31.0 lb/sqft........24.0 lb/sqft
Power Loading.....4.66 lb/hp..........5.64lb/hp
Prof Drag Area....4.975 sq ft.........5.182 sq ft
Max [email protected]@18500ft
Max Climb Rate....3730 ft/min.........3240 ft/min
Range.............410 miles...........575 miles
Service Ceiling...35600 ft............37000 ft


On Wing Loading and Turning Performance -

"On paper, the wing loading of the Spitfire was far less than the Emil. Except that the Emil had slats. Although the slats reduced the advantage of the Spitfire in turning ability, it didn't eliminate it completely. The difference in wing loading was just too great. But the slats endowed the Messerschmitt with another important characteristic. They gave the pilot ample stall warning. Spitfire pilots weren't so lucky. If, in combat with the enemy, a Spitfire pilot pulled too tight a maneuver and stalled, he lost all control and became easy pickings for a fighter on his tail. As a result, many top German pilots believed that the Emil could turn inside the Spitfire. This is because they had fought RAF pilots who were afraid to extract the last ounce of turn capability from their mounts. With the slats preventing vicious stall and the wing giving the Luftwaffe pilots ample warning of impending stall, the German pilots could rack the Emil through the tightest possible maneuver."


Powerplants -

The earliest Spitfires, circa Battle of France, with the Watts wooden 2-bladed fixed-pitch propeller, and even the deHavilland 3-bladed two-position propeller, were inferior to the 109E-3 in both climb and ceiling performance. It was not until the Rotol variable-pitch constant speed propeller was fitted that Spitfire was substantially improved.

TheDB601Aa offered a significant improvement in critical altitude, from the 12140 ft of the old DB601A to 14765 ft.

"A cardinal fault of the Bf109E - one which was corrected in the F and G models - was the design of the supercharger air intake. The unit on the Emil was close to the fuselage and ingested the "dirty" boundary layer air which scrubbed along the cowling surface. As a result, the supercharger ram recovery was 37.5% compared with the Spitfire's 50%. The lower ram recovery meant that the critical altitude was reached at a lower altitude. Had the later design been used on the Bf109E, as much as 1000 ft may have been gained in ceiling and in best combat altitude. This would have nullified much of the Spitfire's performance advantage at height."

"Another important difference between the Bf109E and the Spitfire Mk.IA lay in the supercharger design. The early Merlin engines were equipped with gear-driven single-speed, single-stage units. The supercharger had to be throttles back at low altitude to avoid over-boosting the engine. As altitude increased, more and more of the supercharger capability was used and engine horsepower continued to increase until critical altitude was reached, after which power fell off rapidly.

The DB601Aa engine, on the other hand, was equipped with a single-stage supercharger with a hydraulic or fluid clutch. While heavier and more complex than the gear-driven clutch, this unit had the capability of operating at an infinite number of speed ratios. This meant that the supercharger could be slowed down without choking it and far more power was delivered at lower altitudes. As the Bf109 flew higher, an aneroid control caused the supercharger to run faster to compensate for the decreased density of the air. The variable speed characteristics of this supercharger are obtained through slippage, so it was necessary for the Bf109 cooling system to contain more oil for cooling.

At low levels, the variable-speed supercharger of the DB601Aa allowed some 200 hp more to be delivered to the Bf109. To a great extent, this was the measure of the low altitude superiority of the Messerschmitt fighter."


Armaments -

The Bf109E-3 was equipped with three 20mm Oerlikon MG FF/M (two wing mounted with 60 rpg and one in the prop hub with 200 rpg) plus two 7.9mm Rheinmetall Borsig MG17 in the cowling with 500 rpg. The MG ff/M fired a 115 gram projectile at 350 rpm with a muzzle velocity of 1919 ft/sec. The MG17 fired an 11.6 gram projectile at 1100 rpm with a muzzle velocity of 2600 ft/sec. Total weight of fire for the 109E-3 was 322 lbs/min

The Spitfire Mk.IA was equipped with eight .303 in Browning Mk.II machine guns firing 11.2 gram ball and 11.1 gram AP projectiles at 1350 rpm with a muzzle velocity of 2600 ft/sec. total weight of fire for the Spitfire was 266.7 lbs/min.

"While the Spitfire armament was very adequate against the Heinkel and Dornier bombers ... , it proved to be disappointing ... against the Emils. The German fighter's guns outranged those of the Spitfire. Its cannon were more lethal ..."


Profile Drag -

"...the equivalent profile drag area of the Bf109E was slightly less than that of the Spitfire Mk.IA. This would lead one to believe that the streamlining of the Messerschmitt was better than that of the English fighter. This just wasn't so. The Spitfire was, physically, a larger airplane. It was slightly longer, had a greater wing area, and was deeper. That the drag coefficients were so close could only mean that it was the Spitfire that had the more refined contours.


Energy / Maneuverability -

Maximum Climb Rate...Bf109E-3.........Spitfire Mk.IA
Sea level............3730 ft/min......2900 ft/min
14765 ft.............3300 ft.min......3200 ft/min
16200 ft.............3050 ft/min......3250 ft/min
24000 ft.............1875 ft/min......2150 ft/min
30000 ft.............1000 ft/min......1250 ft/min

Maximum Speed........Bf109E-3.........Spitfire Mk.IA
Sea level............305 mph..........280 mph
5000 ft..............322 mph..........301 mph
10000 ft.............336 mph..........324 mph
15000 ft.............350 mph..........346 mph
16400 ft.............355 mph..........350 mph
18500 ft.............350 mph..........362 mph
20000 ft.............347 mph..........358 mph
25000 ft.............336 mph..........349 mph
30000 ft.............315 mph..........335 mph
35000 ft.............276 mph..........309 mph

Level flight Acceleration -
Sea level............Bf109 superior by +/- 1.5 mph/sec
15000 ft.............practically equal
25000 ft.............Spitfire superior by +/- 0.25 mph/sec

Maneuverability -
At any airspeed, the Spitfire was superior in maximum instantaneous maneuverability, the advantage ranging from about +0.50G at 140 mph up to a full 1.0G or slightly more at 260mph plus.

In terms of maneuverability in the sustained 1G condition, the advantage lay heavily with the Bf109E up to about 18000 ft. Above that altitude, the Spitfire held a modest advantage. In the sustained 2G maneuvering case, the Bf109E was superior up to about 12000 ft, with the Spitfire superior above that altitude. In the 3G condition, the Bf109E was superior up to about 8,000 ft by my best analysis of the graph.


Conclusions -

"...against the Spitfire, the Emil could slash and dive away. At the lower altitudes where the Bf109 was unable to dive, it was capable of outperforming the Spit Mk.IA

At altitudes of about 20,000 feet or more, the Spitfire could outperform the Emil in everything except the dive. Nor could the Spitfire be intercepted effectively at the higher altitudes, since it owned a speed advantage.

British radar prevented the Luftwaffe from jumping the RAF fighter units. Spitfires were forced to descend from the upper altitudes which favored them in order to join battle with invading German aircraft at lower - and less favorable - altitudes.

 

[Shortround6]

Thank you.

The comparison is interesting but the engine mounted cannon for the 109 seems to have been a common misconception at the time this work was done. The speed figures for the Spitfire seem to be for 87 octane fuel while the climb figures seem to be high most official British climb figures are for a 30 minute power level but then some German figures are also done with a climb rating rather than full (combat/emergency) power levels.

thanks again.

 

[Glider]

I have to be concerned as they have got some of the very basic information wrong.
Obvious examples are the incorrect weapons, lack of 100 Octane Fuel and the misconception of a lack of stall warning in the design of the Spitfire.
Others include the assumption that RAF Pilots wouldn't get the most out of their machines, in reality they would fly to the stall warning and then ease a touch until the warning eased off and stay at the edge of the curve by feeling for the warning. They have ignored the German reports that their pilots were afraid of going past the deployment of the automatic slats and the abrupt nature of their deployment, something that was cured by a change in the design for the Me109F.

 

[krieghund]

I have to be concerned as they have got some of the very basic information wrong.
Obvious examples are the incorrect weapons, lack of 100 Octane Fuel and the misconception of a lack of stall warning in the design of the Spitfire.
Others include the assumption that RAF Pilots wouldn't get the most out of their machines, in reality they would fly to the stall warning and then ease a touch until the warning eased off and stay at the edge of the curve by feeling for the warning. They have ignored the German reports that their pilots were afraid of going past the deployment of the automatic slats and the abrupt nature of their deployment, something that was cured by a change in the design for the Me109F.

I agree but remember this was published in 1973. I think if redone today it would be more factually correct taking advantage of the explosion of information via the net. I have been looking for this document since I bought the other one in 1973 (P-40C vs A6M2) but still to no avail.

 

[Ivan1GFP]

Hi Krieghund,

Thanks for posting this analysis. Are we going to see a pdf soon?

I believe the fellow writing this was quite knowledgeable, but fell down a lot in basic information and analysis. The basic information has already been discussed regarding the motor cannon, but how does he come up with the idea that the 109 had longer ranging armament? The two cowl guns were pretty much equivalent to the Spitfire's Brownings, and the MG FF has a horrible trajectory.

- Ivan.

 

[krieghund]

Hi Krieghund,

Thanks for posting this analysis. Are we going to see a pdf soon?

I believe the fellow writing this was quite knowledgeable, but fell down a lot in basic information and analysis. The basic information has already been discussed regarding the motor cannon, but how does he come up with the idea that the 109 had longer ranging armament? The two cowl guns were pretty much equivalent to the Spitfire's Brownings, and the MG FF has a horrible trajectory.

- Ivan.

If I ever locate the volume I'm sure too

The Germans had the same difficultly the Japanese had with the Zero, it has to fight bombers as well as fighters and the MG151 series wasn't quite ready yet and 30cal pop guns in low quantity won't down bombers and both designs didn't cater for a large battery of weapons. They balanced the best they could, however, had I been flying the 'E' I would have mounted an MG17 to fire through the engine like the He100.

Better yet, I'll take the He100 and three MG17, it cruises at the Spit's max speed and has more than 10 minutes over London but then that's for another thread.........

 

[badger45]

Thank you.

The comparison is interesting but the engine mounted cannon for the 109 seems to have been a common misconception at the time this work was done. The speed figures for the Spitfire seem to be for 87 octane fuel while the climb figures seem to be high most official British climb figures are for a 30 minute power level but then some German figures are also done with a climb rating rather than full (combat/emergency) power levels.

thanks again.

From what can be seen in "P-40 vs A6M2" comparison, the climb data are computed from 1-g SEP (specific excess power) curves. So they are indeed for full power and could not be safely used for prolonged climb without overheating the engine.

Regards,
badger45

P.S. Thank you Krieghund for this and other analysis by this author! It's nice read.

 

[Shortround6]

I agree but remember this was published in 1973. I think if redone today it would be more factually correct taking advantage of the explosion of information via the net. I have been looking for this document since I bought the other one in 1973 (P-40C vs A6M2) but still to no avail.

The author may have been going with the best information available at the time, or at least what was common knowledge.

Again I thank you for the work in typing it out for us to see.

 

[Glider]

I agree but remember this was published in 1973. I think if redone today it would be more factually correct taking advantage of the explosion of information via the net. I have been looking for this document since I bought the other one in 1973 (P-40C vs A6M2) but still to no avail.

Fair point and I also thank you for the effort that you obviously put into this.

Many Thanks

 

[timshatz]

All in all, not a bad job. Thanks for posting Krieg.

 

[GregP]

The performance comparison above uses a video game site as its reference?

Please! Neither aircraft could climb 3,000 feet per minute, much less exceed that. A realistic climb for both at best rate is 2800 - 2900 feet per minute (assuming a constant-speed prop) for the Spitfire and 2850 feet per minute or so for the Me 109E model. 355 mph is the highest max speed ever recorded for an Me 109E. More than twenty other tests resulted in about 342 - 345 mph top speed. The Spirfire Mk I was really about 355 mph in most tests.

The Spitfire I was about 6,050 pounds and the Me 109E was about 5,675 pounds at normal loaded weight. Higher weights were possible, but not on fighter missions.

If we want to get was was real, we must average 3 - 15 test reports, not pick the best one and say it was typical. And never from a video game website ...

 

[tomo pauk]

In the OP it is clearly stated that the comparison was written in 1973. The members of that gaming community were just providing it.

 

[Vincenzo]

GregP the tests are available on line?

in the kurfurst page there is "BAUBESCHREIBUNG für das FLUGZEUGMUSTER MESSERSCHMITT ME 109 mit DAIMLER-BENZ-MOTOR DB 601" (i know it's not a test) that repost a max speed of 570 km/h at 5000 meters

 

[krieghund]

The performance comparison above uses a video game site as its reference?
.

I had been searching for this document for a long time and someone on the IL2 board posted excerpts from it. Those guys are pretty serious about trying to be accurate to their gaming.

However, I have very good news....I have located an original copy and it is at home waiting for me..I don't trust APO mail so it will have to wait until I have incentive leave home to scan and post it. I was doing a 'deep data mine' when I came across it.

 

[Denniss]

Some more errors to point out:
The typical E-series Bf 109 had the DB 601A, not the DB 601Aa. The latter was mostly used on the fighter-bomber variants as they needed some additional power.
Early E-series had the DB 601 with critical alt of 4km, but most got an improved version with 4.5km alt AFAIR from the E-3 on.
I have never heard of the 1-min power rating as being cleared for use in the Bf 109, take-off power was 990 PS (601A, not 1100) or 1045 PS (601AA, not 1175)
E-3 did not use MG FF/M, these were introduced with the E-4 (although retrofitted to many older versions). Other gun data is wrong, too: 130g projectiles at 600 m/s and 530 rpm.

 

[Vincenzo]

kurfurst site on DB 601A Kurfürst - DB 601, 603, 605 datasheets - DB 601 A-1 1100 ps for 1' and 990 ps for 5'
on 601Aa Kurfürst - DB 601, 603, 605 datasheets - DB 601 Aa 1175 ps for 1' and 1045 ps for 5', 950 ps for 30'

 

[GregP]

C'mon, there wasn't a Bf 109E that ever climberd at 3700 feet per minute (FPM)! ... unless it wsa zoom climb. Not enough HP to weight. Climb rate was very much more like 2900 FPM. Wherever did you get a 3,700 fpm climb rate?

Steve Hinton, who has flown one or three, says 2,900 fpm for the Bf 109E model ... MAX. We (Planes of Fame) have a G-10 and KNOW how it climbs. While we don't fly it anymore, it IS flyable. Museum pilocy is not to fly any aircaft for which we don't have at least two engines. If they break, you still have to fly them home sometime!

 

[Tante Ju]

I have never heard of the 1-min power rating as being cleared for use in the Bf 109, take-off power was 990 PS (601A, not 1100) or 1045 PS (601AA, not 1175)

The Baubeschhreibbung paper list these rating for 109E. Why do you think it was ot possible use on Bf 109E?

 

[tomo pauk]

From Db-601A and 601B manual:

 

[Ivan1GFP]

Hi GregP,

While you do have examples of the actual planes, I suspect you don't fly them at the throttle settings that were used in combat. Another thing to consider is that you probably don't run them on C3 fuel either.

- Ivan.