View source for Engineering:Vickers S

{{Short description|40 mm ground attack aircraft cannon}}
{{Infobox weapon
|name=Vickers 40 mm Class S
|image=Pilot 6 Sqn RAF with Hurricane IID at Shandur c1942.jpg
|caption= 1942. A [[Engineering:Hawker Hurricane|Hawker Hurricane]] fitted with two Vickers S, at Shandur, Egypt.
|origin=
|type= 
|is_ranged=yes
|is_UK=yes
|design_date=
|production_date=1942
|service=1942-
|used_by=Royal Air Force
|wars=Second World War
|spec_type=
|caliber={{convert|40|mm|in|abbr=on}}
|part_length={{convert|1.7|m|ftin|abbr=on|disp=flip}}
|cartridge_weight={{convert|4|lb|kg|abbr=on}} 40x158R
|feed=12-round drum<br/>later 15 rounds
|action=
|rate=100 rounds/min
|velocity=1,870 ft/s (569.98 m/s)<br>with {{cvt|3|lb|kg}} shot 
|weight=320 lb (134 kg)
|length=9 ft 9 inches (2.97 m)
|variants=Mk 1, Mk 2
|number=
}}

The '''Vickers 40&nbsp;mm Class S''',{{efn|The name of the gun is spelled differently throughout books and the internet, thus it has been standardised here as the ''Vickers 40&nbsp;mm Class S'' following the same format as the similar Molins Class M gun, which had the formal name "QF 6pdr Class M Mark I with Auto Loader Mk III".<ref>{{Cite web|title=THE 6 PDR 7 CWT AND THE MOLINS GUN|url=https://www.quarryhs.co.uk/Molins.htm|url-status=live|access-date=2021-08-14|website=quarryhs.co.uk}}</ref> Format: Company, Caliber, Class + type-letter, followed by mark-number etc.|group=Note}} often shortened to '''"S" gun''',<ref name=Goodrum>{{cite book |first= Alastair |last=Goodrum |title= They Spread Their Wings: Six Courageous Airmen in Combat in the Second World War |url=https://books.google.com/books?id=Ps8TDQAAQBAJ&pg=PT23 |page=23 |publisher= The History Press |date=2013|isbn=9780752492179 }}</ref> was a 40&nbsp;mm (1.57&nbsp;in) airborne [[Engineering:Autocannon|cannon]] designed by Vickers-Armstrongs for use as aircraft armament. It was primarily used during [[Social:World War II|World War II]] by British aircraft to attack ground targets.<ref>{{Cite web|title=THE VICKERS 40 MM CLASS S GUN WITH LITTLEJOHN ADAPTOR|url=https://www.quarryhs.co.uk/sgun.htm|url-status=live|access-date=2021-08-14|website=quarryhs.co.uk}}</ref> It was largely replaced by the RP-3 rocket from 1943 on.

== History ==
The Vickers 40&nbsp;mm Class S gun was developed in the late 1930s as an aircraft weapon. The [[Engineering:Ammunition|ammunition]] was based on the 40x158R cartridge case of the naval 2 pdr Anti-aircraft gun (the "Pom-pom"). The weapon was a long-recoil design derived from the [[Engineering:COW 37 mm gun|37&nbsp;mm (1½&nbsp;pdr) gun]] from Coventry Ordnance Works (COW). 

The gun was originally intended as a bomber defensive weapon and was tested as such in a [[Engineering:Gun turret|turret]] fitted to a modified [[Engineering:Vickers Wellington|Vickers Wellington II]]. This was not adopted for service.

In March 1941, researchers at the Fighter Interception Unit (RAF Tangmere), fitted the fourth prototype Mk I Bristol Beaufighter night fighter (s/n ''R2055'') with the Vickers&nbsp;S, installed asymmetrically, in the place of one of the standard 20&nbsp;mm cannon. In August, the [[Engineering:Rolls-Royce 40 mm cannon|Rolls-Royce 40 mm cannon]] ("R" model) was also trialled in the same Beaufighter. Both cannons were assessed when fired in the air and on the ground. In October, the Vickers&nbsp;S was recommended for any future service use, although it was never incorporated into production Beaufighters. (The reasons for this have remained unclear, although it may have reflected the perception that a single 40&nbsp;mm cannon lacked advantages over the 2x20&nbsp;mm configuration. In addition, Hawker Hurricanes, fitted with two Vickers&nbsp;S were trialled virtually simultaneously in North Africa, in the anti-tank role and this concept was also rejected; see following section.)

=== Combat history ===
Early operations by the Desert Air Force in the North Africa campaign demonstrated that existing weapons were ineffective against newer German vehicles like the [[Engineering:Panzer III|Panzer III]]. In April 1941 a group formed to study the issue, considered a series of 37 and 40&nbsp;mm weapons including the "S", the Rolls-Royce cannon ("BF" variant), and the US-built [[Engineering:M4 autocannon|M4 autocannon]], all firing armour-piercing ammunition.<ref name="Wallace,1972">{{cite book|last=Wallace|first=G.F.|title=The Guns of the Royal Air Force 1939-1945|publisher=William Kimber|location=London|year=1972|isbn=0-7183-0362-8|chapter=10, The 40mm Guns}}</ref> The Rolls-Royce"BF" was initially selected, as it used drum-fed ammunition rather than the "S" belt system, which was considered more reliable. About 200 BF guns were produced, but after a series of misfires and ammunition explosions,<ref name=Goodrum/> the decision was made to introduce ground attack variants of the [[Engineering:Hawker Hurricane variants#Hurricane IID|Hawker Hurricane]] with the "S". This had the added advantage that it carried 15 rounds of ammunition, compared to the "BF"'s 12.

Mark IID and Mark IV Hurricanes could mount one "S" under each wing, in conformal [[Engineering:Gun pod|gun pod]]s. The weight of the guns and ammunition, along with the dust filters and other equipment needed for desert operations, slowed the aircraft by a significant {{convert|40|mph}}. By October 1941 it was decided that the autocannon would not be suitable in the future, and the same research group turned their attention to rockets, eventually leading to the introduction of the RP-3 in 1943.

The weapon was cleared for service on the Hurricane in April 1942 and formed up with No. 6 Squadron RAF at RAF Shandur in [[Place:Egypt|Egypt]] in May. The weapon's champion, Wing Commander Stephen Dru Drury, trained the pilots on using the weapon, as it had so much recoil that the aircraft slowed significantly when fired. This caused the nose to drop, and while flying at a typical altitude of 50&nbsp;feet during the approach, firing without first re-adjusting the flight path was dangerous. The pilots eventually concluded that the guns could be fired twice before the aircraft flew past the target, although on rare occasions a third shot was possible.<ref name=Goodrum/>

Claims by pilots using the Vickers S included 47 tanks destroyed (of 148 tanks hit), as well as nearly 200 other vehicles. However, the Hurricane IID was poorly armoured for the ground attack role and ground fire caused heavy losses. In addition, 40&nbsp;mm ammunition was seldom effective against vehicles as well-armoured as the [[Engineering:Tiger I|Tiger I]] tank.

Mark IV Hurricanes (operational from 1943) had improved armour around their engine, cockpit and fuel tanks.

From 1944, Hurricanes armed with the Vickers S served in the South East Asian theatre. In most cases HE ammunition was used against road vehicles and river craft.

Assessments carried out in South East Asia showed a relatively high level of accuracy: an average of 25% of shots fired at tanks hit their target. (By comparison, RP-3 {{convert|60|lb|kg}} rocket projectiles only 5% against tank-sized targets.) However, 40&nbsp;mm HE rounds were twice as accurate as AP rounds, possibly because the lower weight and higher velocity of the HE round gave it ballistics similar to that of the [[Engineering:M1919 Browning machine gun|.303 in (7.7 mm) Browning]] [[Engineering:Machine gun|machine gun]] that were used for sighting.

== Aircraft weapons of comparable role and era ==
;{{flag|Empire of Japan}}
*37&nbsp;mm Ho-203 – automatic ground-attack/anti-bomber gun
*57&nbsp;mm Ho-401 – automatic ground-attack gun

;{{flag|Nazi Germany}}
*30&nbsp;mm MK 103 – automatic anti-tank/anti-bomber gun
*37&nbsp;mm [[Engineering:BK 3,7|BK 3,7]] – automatic anti-tank/ground-attack gun
*50&nbsp;mm BK 5 – automatic anti-tank/anti-bomber gun
*50&nbsp;mm MK 214A – automatic anti-tank/anti-bomber gun

;{{flag|Soviet Union}}
*37&nbsp;mm NS-37 – automatic anti-tank/anti-bomber gun
*45&nbsp;mm NS-45 – automatic anti-tank/anti-bomber gun

;{{flag|Sweden}}
*57 mm akan m/47 – automatic anti-ship/ground-attack gun

;{{flag|United Kingdom}}
*[[Engineering:Rolls-Royce 40 mm cannon|40&nbsp;mm Rolls-Royce Class BH]] – automatic anti-tank/ground-attack gun (development rival to the Vickers 40 mm Class S gun)
*57&nbsp;mm QF 6pdr Class M – autoloaded anti-ship gun (part of the same naming family as the Vickers 40 mm Class S)

== Footnotes ==
{{notelist}}

== References ==

=== Citations ===
{{reflist}}

== External links ==
*Anthony G Williams, [http://www.quarryhs.co.uk/37-40mm.htm 37MM AND 40MM GUNS IN BRITISH SERVICE]

[[Category:Aircraft guns]]
[[Category:Autocannon]]

{{Sourceattribution|Vickers S|1}}