Wellington with 40mm Vickers.

Moderators: Messalina, Tandorini

Wellington with 40mm Vickers.

Berichtdoor Tandorini » 18 jan 2009, 21:43



Details of the under-wing mounting of the Hurricane



The Vickers S gun turret on the Wellington Mk II Prototype.

40 mm (1.57 in) Vickers S Gun
In 1936 the Air Staff decided to carry out a series of trials to find the minimum size of shell capable of destroying an aircraft with one hit. After various experiments it was found that any aircraft hit by a shell 40 mm (1.57 in) or over would probably not survive. So in 1938 a specification was issued for a 2 pdr gun suitable for aircraft. The obvious choice was Vickers-Armstrongs, but at a meeting at the Air Ministry E.W. (later Lord) Hives of Rolls-Royce announced that his company could produce such a weapon in 18 months, so both Rolls-Royce and Vickers-Armstrongs received development contracts.

The chief designer, at Crayford, Percy Higson, had foreseen the result of the projectile trials, and made sure by obtaining the conclusions long before they were officially announced. Thus by the end of 1938, only months after receiving the order from the Air Ministry, Higson's gun was complete.

The gun used the long recoil system similar to the COW(1) gun. The new gun was smaller, had a much faster rate of fire, and was fed by a magazine holding 15 of the big rounds. The gun fired the same 2 pdr shells as a much heavier naval gun also designed by Higson. In early 1939 Vickers submitted a scheme for mounting the gun in a large dorsal turret in a Wellington 'heavy fighter' with a predictor and a rangefinder. Such an aircraft it was claimed, could engage hostile formations at a range well beyond that of the fighters' defensive fire.

A prototype gun began testing in 1939, and suffered far fewer teething troubles than was usual with an entirely new gun. In early 1940 the gun was dispatched to Woolich for Ordnance Board certification, where no faults occurred during extensive testing. A small production order soon followed for the gun, known at Vickers as the Class S. Vickers also went ahead at Brooklands with fitting the prototype Wellington Mk II (L4250) with the big mushroom-shaped 40 mm emplacement.

The company also submitted a fighter design to Specification F.22/39, mounting an S gun in the nose, the gunner having a sighting cupola similar to the turret. The S gun was also used in the Bristol B.16 nose turret installed in some Coastal Command Flying Fortress II aircraft for anti-submarine operations.

After the fall of France in June 1940 it was obvious that some means would have to be devised to knock out German tanks. Ordnance experts suggested that, if a suitable armour-piercing projectile could be devised, the S gun might provide one answer. A warhead was produced which would penetrate the German Panzers frontal armour, and an S gun was tested in a Beaufighter. Vickers were given an immediate order for 100 more guns, and Hawker Aircraft were asked to make the necessary structural alterations to a Hurricane to take the weight and recoil shock of an S gun under each wing. A mounting was devised by Higson, the big magazine proving difficult to accommodate. In the meantime a Mustang (AM106) was used to test the mounting and devise the best method of attack (the Mustang might have been a more suitable aircraft to use than the lower performance Hurricane).

The trials carried out from Boscombe Down proved very successful, and the first two production guns were fitted to a modified Hurricane. Known as the Mk IID, it was flown to Boscombe Down for assessment in September 1941. Attacks were conducted against a Valentine tank at the Lulworth range. The AP shells penetrated both the front and turret armour, and the go-ahead was given for a Mk IID squadron to be sent to North Africa. As the guns were virtually hand-made, it was decided to air-test every gun fitted to the Hurricanes. In the first test the empty cases of both guns failed to eject and jammed. Why this should have happened after prolonged firing tests remained a mystery, until someone realised that hitherto Vickers-made shells had been used. The Kynoch shells used in these tests had a slightly softer brass case, so that when fired they expanded fractionally more than the Vickers, and their rims were torn off by the extractor. As an interim measure, the rounds were slightly oiled (usually a punishable offence in the RAF, but accepted in this case as a stop-gap solution).

The officer in charge of the project was Wg Cdr. 'Dru' Drury, who was the driving force behind the Mk IID programme. He nearly crashed during early trials, when the two guns were first fired: the recoil caused the aircraft to dip nose down. He recovered just in time, but this remained a problem, and was countered by easing the nose up slightly at the moment of firing. The first squadron, No.6, began training at Shanar in Egypt on 20 April 1942, Drury taking charge of the first period of training. The gun was aimed by the usual Mk II reflector sight, but two Brownings loaded with tracer ammunition were retained and they gave a good indication of the impact point.

The first operation took place on 7 June, when two tanks and a number of trucks were destroyed. The squadron was in continuous action from this time. In early August two DFCs were awarded to No.6 Sqn pilots, F/Lt. Hillier pressing home an attack so low that his tailpane struck the tank he had hit. A captured German tank commander described how his company of 12 PzKpw IV tanks were attacked by No.6 Sqn. Six tanks were knocked out, the other six managed to escape, though one of these had its turret pierced right through. On the other hand No.6 Sqn suffered a high casualty rate: the guns slowed the aircraft by 64 km/h (40 mph), and even the fighter version was no match for the more agile and powerful Bf109F. With the appearance of rocket projectiles, the Hurricane was withdrawn from service in North Africa, although a few were used on what were virtually suicide attacks on V1 launching sites. Most were dispatched to the Far East, where they were very effectively used by No.20 Sqn in Burma.

As the Vickers S gun was originally designed for air-to-air firing, the first shells used were HE. Although based on a naval projectile, the length of the round was increased to obtain the maximum explosive charge. In September 1941 Vickers designed the armour-piercing shell, known as the armour-piercing Mk I. Weighing 1.13 kg (2.5 lb), it was a solid projectile with a tungsten nose which could penetrate 50 mm (1.97 in) armour, and was the ammunition used in North Africa. Vickers-Armstrongs later produced a 3 lb shell for the gun which gave an increased penetration of 9 per cent. This was the final round, with the Service title AP Mark V. HE ammunition was used in Burma, where most targets were 'soft skinned'.

Details of the 40 mm Vickers S gun
Calibre: 40 mm (1.57 in)

Action: Recoil

Cyclic Rate: 125 rpm

Weight: 134 kg (295 lb)

Weight of Ammunition (HE):

(AP Mk 1): 1.134 kg (2 1/2 lb)

(AP Mk 5): 1.3608 (5 lb)

Armour Penetration (AP Mk 1): 50 mm (1.97 in)

(AP Mk V): 55 mm (2.17 in)

Muzzle Velocity: 549 m/sec (1,800 ft/sec)

Ammunition Feed: 15-round spring-loaded drum

Cooling: Air

Effective Range: 2,286 m (2,500 yds)
NEC JACTANTIA NEC METU ("zonder woorden, zonder vrees")

Avatar:De Siciliaanse vlag,oorspronkelijk uit 1282,de triskelion (trinacria) in het midden,is van oorsprong een oud Keltisch zonnesymbool.

Avatar gebruiker
Berichten: 2759
Geregistreerd: 30 mei 2008, 23:18

Keer terug naar Luchtmacht:Algemeen.

Wie is er online

Gebruikers op dit forum: Geen geregistreerde gebruikers. en 1 gast