Dewoitine D.520

Design

An all-metal structure was used, except for fabric-covered ailerons and tail surfaces.

The wing, even if single-spar, was a solid and rigid unit with a secondary spar and many reinforced parts.

The inwardly retracting undercarriage had a wide 2.83 m (9.3 ft) track, and was fitted with wide, low pressure tyres.

A self-sealing fuel tank with a capacity of 396 l (87 imp gal) was mounted between the engine and cockpit, along with two wing tanks which, combined, carried another 240 l (53 imp gal), for a total of 636 (131 imp gall); this was considerably more than the contemporary Bf 109E, Spitfire I and early Italian fighters, each with about 400 l (88 imp gal) fuel capacity.

The ferry range was from 1,300 km (810 mi) to 1,500 km (930 mi) at 450 km/h (280 mph) which, from June 1940, allowed D.520s to escape to North Africa when France fell.

The handling changed according to the amount of fuel carried; using the fuselage tank alone fuel consumption had no appreciable affect on handling because the tank was on the [Vous devez être inscrit et connecté pour voir ce lien], but, with full wing tanks, directional control was compromised, especially in a dive.

The flight controls were well harmonized and the aircraft was easy to control at high speed.

The maximum dive speed tested was 830 km/h (520 mph) with no buffeting and excellent stability both in the dive (depending on fuel load) and as a gun platform.

Engine

The [Vous devez être inscrit et connecté pour voir ce lien] engine was an underpowered, older design, with 850 CV (840 hp) at takeoff at 2,400 rpm, or 935 CV (922 hp) emergency power at 2,520 rpm and at a height of 1,900 m (6,200 ft).

The Hispano engine had some advantages over some later engines; for example, the weight was only 515 kg (1,140 lb), compared to the 620 kg (1,400 lb) of the [Vous devez être inscrit et connecté pour voir ce lien].

Fuel was fed via six [Vous devez être inscrit et connecté pour voir ce lien] S.V. 56 carbureteurs mounted on an inlet manifold which directed compressed air from the
supercharger to the engine cylinders; the 12Y-45 and -49s fitted to production D.520s used either [Vous devez être inscrit et connecté pour voir ce lien] fuel.

The -45 drove an electrically operated [Vous devez être inscrit et connecté pour voir ce lien] three-bladed, 3 m (9.8 ft) diameter, variable pitch propeller, while D.520s from № 351 were fitted with the 12Y-49 960 CV (950 hp) engine driving a [Vous devez être inscrit et connecté pour voir ce lien] pneumatically operated propeller, also 3 m (9.8 ft) in diameter.

Fire suppression system

The D.520 had a fire suppression system with a fire extinguisher activated from the cockpit.

The engine was started by a simple but effective system, operating with compressed air.

A Viet 250 air compressor charged several air bottles (one with 12 l capacity, as well as another 8 l tank, three smaller 1 l units matched to the weapons).

The 12 l air bottle was used for the brakes and later, for the Chauvière propeller's constant speed adjustment.

The small air bottles provided up to 12 seconds at 9,000 m (30,000 ft) or 20 seconds pressure at low level, before the Viet air compressor re-charged them.

The pilot had a complete set of cockpit instruments, and a 10 l oxygen bottle located in the fuselage just behind his seat, with either Munerelle or Gourdou oxygen regulator systems mounted on the right instrument panel.

Equipment included a [Vous devez être inscrit et connecté pour voir ce lien] radio-receiver set, an OPL RX 39 [Vous devez être inscrit et connecté pour voir ce lien] (less effective than the Revi system), a height adjustable seat, and a sliding canopy with large, clear panels.
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Except over the long nose, the pilot's view was good, since the pilot was seated quite high over the forward fuselage, however, no rear-facing mirrors were fitted.

Armament

Production-standard armament consisted of a 20 mm HS.404 moteur-canon, with an ammunition capacity of 60 rounds, firing through the propeller hub, and four belt-fed MAC 1934 M39 7.5 mm (.295 in) machine guns in the wings, each with 675 rounds per gun.

The MAC 1934 machine guns had a high [Vous devez être inscrit et connecté pour voir ce lien] of 1,200 rounds per minute (rpm), while the effective HS.404 fired at
600 rpm and was accurate up to 500 m (1,600 ft); the ammunition capacity meant that the MAC 1934s could be fired for a total of 30 seconds, while the HS. 404 had 10 seconds worth of ammunition.

In combat the MS.406 had only two 7.5 mm and was, therefore, at a disadvantage when the HS.404 had used up its ammunition, while a D.520 could continue to fight effectively because it had four fast-firing machine guns (over 80
rounds/sec), with 20+ seconds of ammunition still available.

The D.520 had provisions for two BE33 "illuminating bombs", useful for nocturnal interception missions, but these were rarely used because French fighters rarely flew night-time missions.

Maintenance

The D.520 was designed to be maintained easily with many inspection panels, a rare feature for its time.

Re-charging the D.520 ammunition was swift and easy; the machine gun magazines required five minutes each and three minutes for the 20 mm cannon.

To fill the machine gun ammunition boxes took 15 minutes, while five minutes were needed to empty the 20 mm box (the cartridges were not expelled).

The D.520's cockpit was set well back in the fuselage, aft of the trailing edge.

That gave the pilot good downward visibility, but the long nose in front of him was a drawback when taxiing on the ground

Production time

Production was optimized with a reduced 7,000 man/hour each, roughly half the time compared to the previous D.510 and MS.406, and far less many other fighters of the time, such as the MC.200/202 (21,000 hours), but around 50% more than a Bf 109E (4,500 hours).

The French Air Ministry planned for over 300 aircraft/month and managed to reach this goal, especially in June 1940, but it was too late to affect the tide of battle.

After the armistice with Germany, a further 180 machines were built, bringing the production total to 905.

Flight difficulties


Although employing a modern design philosophy for its time, the D.520 was considered more difficult to fly than the older MS.406.

Capt. [Vous devez être inscrit et connecté pour voir ce lien], commanding officer of the RAF's Captured Enemy Aircraft Flight, tested the D.520 at [Vous devez être inscrit et connecté pour voir ce lien],
saying that

“It was a nasty little brute.

Looked beautiful but didn’t fly beautifully.

Once you get it on the ground, I was told not to leave the controls until it was in the hangar and the engine stopped.

You could be taxiing toward the hangar and sit back when suddenly it would go in a right angle.”

Operational history

France

Battle of France

The [Vous devez être inscrit et connecté pour voir ce lien] was the first unit to get the D.520, receiving its first aircraft in January 1940.

These were unarmed and used for pilot training.

In April and May 1940, operational units received 34 production D.520s; the type proving to be very popular with the pilots.

In comparative trials on 21 April 1940 at CEMA at Orleans-Bricy against a captured Bf 109E-3, the German aircraft had a 32 km/h (20 mph) speed advantage owing to its more powerful engine.

However, the D.520 had superior maneuverability, matching its turning circle, although displaying nasty characteristics
when departing and spinning out of the turn repeatedly during the tests.

The Bf 109, owing to its [Vous devez être inscrit et connecté pour voir ce lien], could easily sustain the turn on the edge of a stall.

By 10 May 1940, when Germany invaded France and the Low Countries, 228 D.520s had been manufactured, but the Armée de l'Air had only accepted 75, as most others had been sent back to the factory to be retrofitted to the new standard.

As a result, only GC I/3 was fully equipped, having 36 aircraft.

They met the Luftwaffe on 13 May, shooting down three [Vous devez être inscrit et connecté pour voir ce lien] and one [Vous devez être inscrit et connecté pour voir ce lien] without loss.

Four more Groupes de Chasse and three naval Escadrilles rearmed with the type before France's surrender. GC II/3, GC III/3, GC III/6 and GC II/7 later completed conversion on the D.520.

A naval unit, the 1^er Flotille de Chasse, was also equipped with the Dewoitine. But only GC I/3, II/7, II/6 and the naval AC 1 saw any action in the [Vous devez être inscrit et connecté pour voir ce lien]. GC III/7 converted to the D.520 too late to be involved in combat.

In air combat, mostly against Italians, the Dewoitine 520s claimed 114 air victories, plus 39 probables.

Eighty five D.520s were lost.

By the armistice at the end of June 1940, 437 D.520s had been built with 351 delivered.

After the armistice, 165 D.520s were evacuated to North Africa.

GC I/3, II/3, III/3, III/6 and II/7 flew their aircraft to Algeria to avoid capture.

Three more, from GC III/7, escaped to Britain and were delivered to the [Vous devez être inscrit et connecté pour voir ce lien].

A total of 153 D.520s remained in mainland France. One of the most successful D.520 pilots was [Vous devez être inscrit et connecté pour voir ce lien], who shot down 18 aircraft (four Germans, seven Italian and seven British), scoring all of his kills with the D.520, and ranked as the fourth-highest French ace of the war.

Under Vichy

In April 1941, the German armistice commission authorized [Vous devez être inscrit et connecté pour voir ce lien] authorities to resume production of a batch of 1,000 military aircraft for their own use, under the condition that 2,000 German-designed aircraft would later be manufactured in France and delivered to Germany.

As part of this agreement, 550 examples of the D.520 were ordered to replace all other single-seat fighters in service.

The plan was to have the Dewoitine eventually equip a total of 17 Groupes with 442 aircraft, three escadrilles of the Aéronautique navale with 37 aircraft each, plus three training units with 13 aircraft.

The agreement stated that aircraft of this new batch were to be similar to the ones already in service.

From serial number 543 on, however, D.520s used the 12Y-49 engine that had a slightly higher rated performance than the 12Y-45, although the [Vous devez être inscrit et connecté pour voir ce lien] explicitly prohibited replacing the original engines with the more powerful 12Y51 or 12Z engines.

In 1941, D.520s of GC III/6, II/3 and naval escadrille 1AC fought the Allies during the [Vous devez être inscrit et connecté pour voir ce lien]. The [Vous devez être inscrit et connecté pour voir ce lien] (Armée de l'Air de Vichy) was already relatively strong, but several units were sent to reinforce
it. D.520s were the only French single-seat fighters capable of making the trip to Syria.

The GC III/6 was sent first.

The ferry trip was very difficult for a 1940 interceptor and the pilots pushed their planes as far as their fuel tanks would allow them to.

They flew from France to Syria with intermediate stops at Rome, Brindisi or Catania.

Another route was available through Germany and Greece (Athens), but it was seldom used.

The trip always included a stopover in Rhodes (once an Italian base), before the final flight to Syria.

This meant several thousands of kilometers were flown over mountains and sea.

The most demanding part was Catania-Rhodes, which entailed no less than 1,200 km flown over the sea.

Even the trip from Rhodes to Syria was 800 km.

LeO 451s and [Vous devez être inscrit et connecté pour voir ce lien] bombers had few problems, but D.520s were forced to fly a strenuous and dangerous mission, without any help or external assistance.

Of the 168 French aircraft (of all types) sent to Syria, 155 accomplished their mission and successfully arrived.

The Vichy Air force was numerically strong, but with very few ground crew and spare parts, so the operational flying time for the D.520s was very limited. D.520s of GC III/6 first saw action against British aircraft on 8 June 1941, when
they shot down three [Vous devez être inscrit et connecté pour voir ce lien], losing one D.520 with its pilot taken prisoner).^{[Vous devez être inscrit et connecté pour voir ce lien]}

Over the following days several escort missions were made to protect Martin, LeO and Bloch 200 (3/39 Esc) aircraft from British [Vous devez être inscrit et connecté pour voir ce lien] fighters. On 9 June, Two Hurricanes were shot down (with another D.520 lost).

In total, during the Syria campaign 266 missions were flown by the Vichy French Air Force: 99 of them were made by D.520s, nine by MS.406s, 46 by Martin 167s and 31 by LeO 451s.

The D.520s were therefore the most active of the French aircraft in the campaign, where they claimed 31 kills over British and Australian units while losing 11 of their own in air combat and a further 24 to [Vous devez être inscrit et connecté pour voir ce lien] fire, accidents and attacks on their airfields..

On 10 July, five D.520s attacked [Vous devez être inscrit et connecté pour voir ce lien] bombers from [Vous devez être inscrit et connecté pour voir ce lien] that were being escorted by seven [Vous devez être inscrit et connecté pour voir ce lien] from [Vous devez être inscrit et connecté pour voir ce lien] (3 Sqn).

The French pilots claimed three Blenheims, but at least four of the D.520s were destroyed by the Australian escorts, including two by [Vous devez être inscrit et connecté pour voir ce lien]. The following day, a Dewoitine pilot shot down a P-40 from 3 Sqn, the only Tomahawk lost during the campaign. This Dewoitine was in turn shot down by F/O [Vous devez être inscrit et connecté pour voir ce lien].

The initial advantage that the Vichy French Air Force enjoyed did not last long, and they lost most of their aircraft during the campaign.

The majority of the lost aircraft were destroyed on the ground where the flat terrain, absence of infrastructure and absence of modern anti-aircraft (AA) artillery made them vulnerable to air attacks.

On June 26, a strafing run by Tomahawks of 3 Sqn, on Homs airfield, destroyed five Dewoitine D.520s of Fighter Squadron II/3 (Groupe de Chasse II/3) and damaged six more.

By the end of the campaign, the Vichy forces had lost 179 aircraft from the approximately 289 committed to the Levant.

The remaining aircraft with the range to do so, evacuated to Rhodes.

The known French losses of fighter aircraft were 26 in air combat and 45 in strafing and bombing actions.

Allied forces lost 41 planes, 27 of those shot down by French fighters.

During [Vous devez être inscrit et connecté pour voir ce lien], GC III/3 (previously known as GC I/3) was engaged in combat with the Allies over [Vous devez être inscrit et connecté pour voir ce lien].

Flotille 1F saw action versus the [Vous devez être inscrit et connecté pour voir ce lien] squadron [Vous devez être inscrit et connecté pour voir ce lien] (from the carrier[Vous devez être inscrit et connecté pour voir ce lien]), over [Vous devez être inscrit et connecté pour voir ce lien].

One D.520 was among 14 US victory claims, with the only Allied losses being due to ground and friendly fire.

Other Dewoitine-equipped units in North Africa such as GC II/7 or GC II/3 did not to take part in the fighting.

Overall, the known D.520 air strength in North Africa was 173 D.520s (143 combat ready) of GC II/3, III/3, III/6, II/7 and II/5, another 30 were in Senegal with GC II/6.

The Navy had Esc 1AC and 2AC. Many D.520s were destroyed on the ground by Allied bombing.

The French Air Force lost 56 aircraft, among them 13 D.520s.

The Navy lost 19 D.520s aircraft.

Among the 44 kills that the French scored overall, there was an entire squadron of nine Fairey Albacore, from the HMS Furious, all shot down by D.520s of GC III/3.

Free French Dewoitines

A very small number of D.520s were briefly operated by Free French Forces for training purposes.

Along with the three examples that had flown to Britain in June 1940, two other D.520s were recovered from
retreating Vichy forces in [Vous devez être inscrit et connecté pour voir ce lien], Lebanon.

These D.520s were flown by pilots of the [Vous devez être inscrit et connecté pour voir ce lien] unit before the unit was sent to the USSR, where they flew the [Vous devez être inscrit et connecté pour voir ce lien] that had many similarities with the D.520.