# DeWoitone D.520 vs. Spitfire Bf-109



## Jerry W. Loper (Mar 30, 2010)

If France hadn't got knocked out of the war so fast in 1940 and more DeWoitone D.520 fighters were produced, would this fighter have proved equal to the contemporary Supermarine Spitfire Mk. I and Messerschmitt Bf-109E?


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## Colin1 (Mar 30, 2010)

France's rapid demise was largely down to her economic situation prior to hostilities. At the outbreak, France barely had enough D520s to equip a single squadron.

Technically, the Dewoitine fighter had more potential for development than the Morane-Saulnier fighter though practically, I don't think France's defence industry had anything bigger or better up their sleeve powerplant-wise; nor did the incumbent 12Y have a lot of margin for development.

Faster than a Hurricane I, slower than either a Spitfire I or a Bf109E but with a useful armament and good manoeuvrability, it acquitted itself well in the short conflict that it was thrust into; in my own opinion, keeping up with British and German technological developments after the Battle of Britain would have been difficult with French defence procurement in the state it was in but politics doesn't account for the galvanising effect that invasion has on a country.

My own view is that the D520 would progressively fall behind into obsolescence owing to the crisis that France's defence industry was in, not far behind the Hurricane, which is a shame.

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## Thorlifter (Mar 30, 2010)

Equal? Not IMO, but it sure was close. I'm at work and doing this from memory so I may be wrong. I believe the Mk.I and the Emil were both faster, armament was good on the D.520. I know the early models were very slow and had issues with the engines or cooling or something like that. Later models had a bigger engines. Not sure of their manuverability vs the Mk. I and 109E.


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## Shortround6 (Mar 30, 2010)

A problem with making a comparison of this type is that there were in effect several MK I Spitifires and the most up to date version was being replaced by the MK II within 3 months of France falling. 

The DeWoitone D.520 never really had a chance to have armor or self sealing tanks fitted so it's survival is suspect compared to later Spitfire MK Is. On the other hand it's performance didn't suffer from the installation of the extra weight either. 
The Hispano engine probably wouldn't be able to offer much increased performance from 100 octane fuel. The Hispano engines usually had rated altitudes thousands of feet below the Merlin and DB engines. With the design of both aircraft and engine essentially "frozen" by the Germans it is a little hard to estimate what later improvements might have been.


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## Vincenzo (Mar 30, 2010)

the actual project D 520 with H12Z engine can give a idea of development for the dewoitine fighter.

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## tomo pauk (Mar 30, 2010)

Agree with vicenco - the 12Z,capable for 1300 HP, was tested in Dewoitine, Morane-Saulnier Arsenal hulls, providing speeds in excess of 600 km/h.


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## Shortround6 (Mar 30, 2010)

tomo pauk said:


> Agree with vicenco - the 12Z,capable for 1300 HP, was tested in Dewoitine, Morane-Saulnier Arsenal hulls, providing speeds in excess of 600 km/h.



Could you please tell me when these test flights took place and where?


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## zoomar (Mar 30, 2010)

I've always liked the looks of the D.520, with its long nose and cockpit set way back. Given the overal situation in France during 1940 it is hard to know for sure how it really would have compared to the Bf-109 in conditions of numerical equality. My own prejudice is to believe it would have been better than the Hurricane, but not equal to the Spit. Also, I doubt the basic design had the inherent "stretch" that the Spit and 109 had. The D520 was linked at the hip to its powerplant and might not have been amenable to progessive engine upgrades. If memory serves the D-521 was an experimental version reengineered to take the Merlin...and it was a poorer performer than the D520.


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## Kurfürst (Mar 30, 2010)

I don't see either why it would be any more troublesome for the Hispano engine to see similiar development as did the Daimlers, R-Rs or Allisons... it was certainly an outstanding engine in 1940.

As to the subject, the French did tactical trials with their fighter materiel against that of the captured 109E, it might gives some idea about strenghts and weaknesses:

http://www.kurfurst.org/Tactical_trials/109E_FrenchCEAMtrials/french_109e_tt.html

Similiar German and British tactical trials:

Kurfrst - Vergleichsfliegen Bf 109 E, Bf 110 C, Spitfire, Hurricane und Curtiss.
Kurfürst - R.A.E. - Messerschmitt Me.109 Handling and Manoeuvrability Tests


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## Colin1 (Mar 30, 2010)

Kurfürst said:


> I don't see either why it would be any more troublesome for the Hispano engine to see similiar development as did the Daimlers, R-Rs or Allisons...
> 
> it was certainly an outstanding engine in 1940


If I recall
It was a physically small engine with a large displacement, there wasn't alot of room for development.

Maybe it was, but in mid-1940 the Merlin III was also an outstanding engine; in early 1941 however, the BMW801 could run rings around both it and the BMW's contemporary, the Merlin 45.


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## Glider (Mar 30, 2010)

From what I remember the performance of the D520 in combat was below average. In Syria they had a difficult time against Tomahawks and Gladiators and I am not aware of any great victories in France.


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## Vincenzo (Mar 30, 2010)

Glider said:


> From what I remember the performance of the D520 in combat was below average. In Syria they had a difficult time against Tomahawks and Gladiators and I am not aware of any great victories in France.



afaik it go good in BoF


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## vanir (Mar 31, 2010)

The Soviet Klimov M-105P series is basically a remanufactured 12Y fitted with a two speed blower. Its development history could easily be considered predictive for the Hispano, international rating for the first series on standard octane (low grade aviation fuel) 1100hp, first series on high octane (standard grade aviation fuel) 1260hp, second series on high octane 1300hp, 3rd series on high octane 1360hp. Maximum emergency output at 2800-3000rpm is necessarily higher than these figures which are the international ratings at 2600rpm.

The Luftwaffe used several D.520 as advanced conversion trainers (ostensibly Ergänzungsgruppen I assume, combat capable as reserves) but as the Emil became available for this purpose most were handed over to Bulgarian, Rumanian and Vichy forces, later Italian.
This suggests without further Hispano engine development the Emil was a superior warplane, ergo so was the Spit, but there is no reason to think the type wasn't perfectly contemporary had the Hispano 12Y engine development continued along the same lines as the Klimov.

In fact when you think about it the Hispano probably would've kept its Szydlowski blower until 1941 and then had a dual stage fitted just like the Merlin 60/70 series. On standard grade in France I think we can assume an output in the 1500hp class with certainty and a maximum throttle height of at least 7000m. These are conservative projections and would keep it contemporary with a Spit IX or a 109F/G so long as you didn't bolt 50mm cannon on the thing.

The early series Hispano 12Y on standard grade fuel seems to have performed very similar to an early Allison in the P-40 on similar grade, with a throttle height at least 5000 feet taller (so the alt performance of something like a P-40N). Continued production however would've undoubtedly produced engines basically the same as the PF-2/3 series Klimovs but with Merlin style two-stage blowers.


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## tomo pauk (Mar 31, 2010)

Shortround6 said:


> Could you please tell me when these test flights took place and where?



Here is for Arsenal, from Arsenal VG 39 - fighter:



> The final development in the VG 30 series of fighters to be flown, the VG 39 commenced its flight test programme on 3 May 1940, and the prototype differed from the VG 33 primarily in having a 1200hp Hispano-Suiza Type 89ter 12-cylinder liquid-cooled engine with an elongated propeller shaft, a revised wing structure which retained the profile and contours of the earlier wing, and a wing-mounted armament of six 7.5mm MAC 1934 M39 machine guns. During flight testing the prototype VG 39 attained a maximum speed of 625km/h at an altitude of 5750m.


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## Shortround6 (Mar 31, 2010)

There were considerable difference between the mid series Hispano "Y" series engines and the last of the 'Y" series (the 50-51) let alone the "Z" series engines. 
"Z" series engines in 1940 were prototypes and there may be considerable confusion as to what aircraft were fitted with exactly which configuration of engine. ALL "Z" series engines being fitted with carburetters at this time. Plant evacuations and relocations also confuse things.

The "Y" series of engines were certainly not outstanding engines in 1940. They were in 1934 but not in 1940.
Large in displacement and slow turning but light in weight, they were competitive in power to weight in the 30s but loosing ground by 1940. Supercharger development was also behind the curve. While it's intake system might have looked OK at the time to modern eyes it can't be seen as anything but an abomination.
With out throwing the whole thing out and starting over modifications were not much more than palliatives.
even the Russian modifications are behind the times and do little or nothing for performance at much over 4000 meters.


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## JoeB (Mar 31, 2010)

Glider said:


> From what I remember the performance of the D520 in combat was below average. In Syria they had a difficult time against Tomahawks and Gladiators and I am not aware of any great victories in France.


In the Battle of France period, as given case by case in "Battle of France Then and Now" by Cornwell:
Spitfires downed 24 Bf109E's for 32 Spitfires shot down by Bf109E's, .75:1
Hurricane: 74:151, .49:1
Hawk 75: 23:38, .61:1
D.520: 14:30, .47:1

In the much smaller sample of Syria, per "Dust Clouds Over the Middle East" by Shores:
D.520's downed 2 Tomahawks for 3 losses
4 Hurricanes for 2 losses
3 Fulmars for no losses
no Gladiators for 4 losses

North African based D.520's, per "L'Aviation Vichy au Combat T.1" by Ehrengardt and Shores:
18 May 1942: D.520's downed 1 Fulmar (of 807 Sdn from Argus) for 1 loss 
North Africa landings from 8 Nov 1942,
FAA Sea Hurricanes and Seafires downed a total of 4 D.520's without loss (respective victories hard to determine, 4-5 Albacores were downed by D.520's)
USAAF Spitfire V's downed 3 D.520's for1 loss
USN F4F's of VGF-26 probably accounted for the disappearance of a D.250 of 1F, Aeronavale.

Joe


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## zoomar (Mar 31, 2010)

JoeB said:


> In the Battle of France period, as given case by case in "Battle of France Then and Now" by Cornwell:
> Spitfires downed 24 Bf109E's for 32 Spitfires shot down by Bf109E's, .75:1
> Hurricane: 74:151, .49:1
> Hawk 75: 23:38, .61:1
> ...



I'm never really sure what operational records mean when comparing warplanes. So much depends on pilot morale, skill, tactics, numbers, and the overall tactical and strategic situation. The Me262 had, I believe, a piss-poor won-loss record against the USAAF and RAF, but most people would agree it was superior to its opponents in speed, climb, armament, dive, and most other measures except turning circle. But because they had to take of and land from field haunted by Tempests and P-51s they were easy pickings.


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## JoeB (Mar 31, 2010)

zoomar said:


> I'm never really sure what operational records mean when comparing warplanes. So much depends on pilot morale, skill, tactics, numbers, and the overall tactical and strategic situation. The Me262 had, I believe, a piss-poor won-loss record against the USAAF and RAF, but most people would agree it was superior to its opponents in speed, climb, armament, dive, and most other measures except turning circle. But because they had to take of and land from field haunted by Tempests and P-51s they were easy pickings.


Well, the specific example and general point have been covered lots of times but,

specific example: the Me262 operated under lots of disadvantages, but most kills of 262's by piston engined planes (bulk of which were by P-51's, a few each by other types, US, British and Soviet) were *not* of a/c just taking off or landing. And a lot of it also involved the piss poor combat persistance, low fuel capy compared to consumption, of early jets, compared to P-51's which could hang around a relatively great distances from base, and turn into the firing passes of a jet till the jet had to go home even though much closer to base. And that *was* a characteristic of the planes, just like speed. But it's off topic, lots of other threads can be resurrected to debate that one, and I agree anyway in a controlled combat right over an airfield both planes were operating from, the Me-262 would have most of the advantages.

General point: one discussion to have about any plane in comparison to others is basic statistics of speed, climb, etc in any detail we might have, plus turn data etc, assuming we really have such data (ie. we're not semi making it up with canned software and a few assumptions) and it's really apples and apples (beaten up captured plane v well tuned 'our' plane, different countries testing their own a/c with differnt conditions of engine boost and so forth). We can just list those statistics and have that be the discussion.

The limitation there is, there is *no analytical way* to relate a 15 mph speed advantage to a specific advantage in overall combat effectiveness, especially if it's combined with a 500fpm climb disadvantage, a roll rate advantage, an armament disadvantage, a tendency to lose performance in rought field conditions, etc etc. If the discssion is overall combat effectiveness between basically comparable airplanes (and P-51 and Me-262 aren't really so comparable so kind of an extreme example), one way or another the argument will always turn to how the plane actually did in combat. But often that will be 'well I read this airplane claimed this many victories' or 'so and so pilot had a mock combat with the other type and he was able to stay on its tail'. I think it's better to find as many actual two sided combat results as possible. Sometimes real combat results are surprising, and definitely add perspective compared to just arguing performance stats. No they don't answer the whole question, but which plane is faster according to official stats does not answer the question either, of which was plane was *more effective*.

In this case the general picture of BoF stats is that the D.520 was comparably successful to the second best British fighter, the Hurricane, and also second best itself to the Hawk among French fighters, though not by a large margin. Those Hawk and D.520 units were operated by the same air arm at the same time and place v same opponent so that seems a pretty fair comparison. For that matter, the conditions weren't greatly different for the British fighters, though Spiftires (and some though not most of the Hurricanes) were Fighter Command a/c operating from Britain so, at that time still, they were safer around their own airfields and generally had better knowledge and options when and where to attack the enemy advantageously via ground control. I would also add that the older French types (Bloch, Morane, etc) had a noticeably worse record v Bf109 than the D.520 (32:105, .30:1) in the campaign. 

I don't think much can be drawn from the Syria or North Africa cases because they are so small, mainly provided for info, and to show that the Tomahawk did not actually demonstrate a great superiority over the D.520 in combat. It might have in a longer campaign, and the Gladiator might not have shown up as well in a longer campaign if tasked with handling a comparable number of D.520's all by itself.

Joe


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## NZTyphoon (Apr 3, 2010)

According to Raymond Danel Jean Cuny (Docavia 4 _ Le Dewoitine D.520_), in February 1940 Dewoitine converted one D.520 into a D.521 by fitting a Rolls-Royce Merlin III driving a de H propeller; maximum speed was 570 km/h or 354 mph (height not mentioned) at a weight of 2,835 kg (6,251 lbs), a weight increase of 158 kg (348 lbs) over the D.520. There were problems:

1) The heavier Merlin changed the cg of the D.521

2)The Merlin rotated in the opposite direction to the H.S 12 Y 45

3) The aircraft was unstable in the yaw at low speeds

Another major problem was that the D.521 couldn't be fitted with the 20 mm Hispano, its most potent weapon. 

Had the D.521 been fitted with a constant-speed propeller it would have probably been slightly slower but benefitted from a faster rate of climb; however the heavier prop would have meant further cg problems, without a substantial redesign of the airframe (eg: longer rear fuselage).


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## FalkeEins (Apr 4, 2010)

I'd like to make two points if I may ;

(i) as already pointed out the pilot made the difference in combat - as the comparative trials posted by Kurfurst point out the D520 was not superior in any way to the Emil, certainly couldn't turn with it or out-dive it

(ii) The D520 struggled into service principally with GC I/3 during May 1940 - serviceability as with any 'new' aircraft was pretty poor - the pilots complained of endless teething problems. FWIW GC I/3 was the third highest scoring Armée de l'Air Groupe de Chasse during the BoF with 75 victories (II/5 on Hawks had around 120 IIRC)

I have a copy of Hubert de Salaberry's privately published 'Récits de guerre' (GC I/3 pilot) and I've translated an account of one of his combats at the controls of a D520 here

FalkeEins - my Luftwaffe blog: D.520 vs. Me 109 E, Battle of France

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## Juha (Apr 5, 2010)

Thanks a lot FalkeEins!
very interesting article. D.520 was a fascinating plane. Eric Brown didn’t like it much, maybe as a carrier pilot he was overly negative towards planes with harsh stall characteristics. Some French on the other hand are fanatically for it. It is also interesting that de Salaberry says that he was slowly gaining the 109E, at least one French ace claimed that he could easily gain diving 109E in D.520 and the French test says that the diving speeds were same.

BTW thanks for Kurfürst for publishing the French test if I have not thanked for that earlier.

Juha


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## FalkeEins (Apr 5, 2010)

thank you Juha.....de Salaberry goes on to say that the D520 was some 30-50 km/h slower than an Emil in level flight but could catch it up in the dive due to the "finesse of its lines" - the D520's real problem was the inadequate power plant.. you're right, I get the impression that some 'enthusiasts' are a little more 'fanatical' about the D520 than is really merited


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## Iain Stewart (Nov 24, 2021)

My dad flew RAF Sunderlands in West Africa in 1941. One day they were bounced by three Vichy D520s which shot up the aircraft pretty well but didn't shoot it down. He won a DFM in that action.

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## nuuumannn (Nov 24, 2021)

I know thsi is a little late in the day, but the D.520 was a real handful to fly and operate on the ground, with a tendency to ground loop among other issues, visibility on the ground was not good either. I remember reading an account translated into Englissh about flying the type and a French pilot remarked, "That little She-Devil is never to be trusted until she is in the hangar..."

In saying that, it's unpredictability makes it an edgy little machine. I like it.





Musee de l&#x27;Air 23




Musee de l&#x27;Air 24

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## FalkeEins (Nov 29, 2021)

My piece from De Salaberry is no longer on my blog as I put it in my 'Luftwaffe aces' book. I've got a decent article on the D.520 with some great pictures all ready to go but not much interest out there I'm afraid.

BTW some 467 D.520s were constructed but only around 238 – five escadrilles - saw Armée de l'Air service of which 89 were lost. Over 50 of these 'losses' were the result of a lack of spares and inadequate front-line facilities. One factor in the indifferent performance of the D.520 in France is rarely mentioned - the CGT (French communist trade union at the Toulouse factory) had received an order from the PCF (French communist party) to 'go-slow' on the production of the D.520 as a direct result of the German-Soviet non-aggression pact. An account from GC II/7...

".. The Dewoitines were being delivered to us piecemeal ('..au compte-goutte..') Finally five pilots and five mechanics flew to Toulouse on board a Bloch 220 on the afternoon of May 14. Once there more surprises awaited us - although the airfield was awash with machines, the Dewoitines were not ready for a variety of reasons..(...) our pilots returned with their aircraft ten days later on the 24th.."

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## tomo pauk (Nov 29, 2021)

FalkeEins said:


> the CGT (French communist trade union at the Toulouse factory) had received an order from the PCF (French communist party) to 'go-slow' on the production of the D.520 as a direct result of the German-Soviet non-aggression pact.



What orders were sent to CGT from PCF on 4th September of 1939?


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## FalkeEins (Nov 29, 2021)

Don't know. The 11 April 1940 issue of 'Flight' described the D.520 as " a considerable advance over the other French types now in service with the Armée de l'air" but added that "since June 1939 little has been heard of the D.520. " From December 1939 GC I/3 carried out operational testing and conversion training in the south of France on the type - more one hundred modifications were required before the type could be cleared for service.


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