Cannon-armed Spitfires?
Tony Crompton
Hurricane for installation of the Hispano cannon. This installation in the
thin-winged Spitfire was a problem since the cannon had to be turned partly
on its side to be accommodated and still required blisters to contain the
breech. There were inordinate gun-jamming problems with this arrangement
and 19 squadron - the first to get cannon-armed Spitfires - reverted to the
8-Browning version. In contrast to the Spitfire, the Hurricane had thicker
wings and was, later, fitted with four wing-mounted cannon without
difficulty.
Although the Air Staff might have been unaware of the tactical
considerations when the decision was made to fit cannon to Spitfires, the
Hurricane, as the less nimble aircraft but a steadier gun platform, was the
obvious aircraft to take on bombers with increasing armour protection, where
the sustained weight of fire from cannon was important. The more
manoeuvrable Spitfire, however, was the obvious candidate for
fighter-on-fighter engagements. With fleeting opportunities with your enemy
in your sights, the advantages of faster-firing machine guns would be
obvious. Indeed, many pilots - including Bader - preferred a machine gun to
a cannon armament for dogfighting at the time.
Why was the possibility of mounting the cannon under the Spitfire's wing
considered? This presumably would have cured the gun-jam problem. This
configuration was not unknown at the time - the French were considering
fitting the MS406 with a Merlin in place of the Hispano-Suiza "moteur canon"
before the war and proposed two cannons slung under the wing.
I'd welcome any references to documents explaining this decision.
TIA
Tony Crompton
--
Geoffrey Sinclair
Tony Crompton wrote in message ...
>I have been unable to find why, in 1939/40, the Spitfire was chosen over the
>Hurricane for installation of the Hispano cannon.
While I do not have the full timeline for the experiments with
cannon armament in the Hurricane the IIC version, 4 by 20 mm
cannon was delivered around the same time as the production
cannon armed Spitfires.
Hurricane L1750 was fitted with a pair of externally mounted
20 mm cannon May 1939, the slow rate of fire and limited
ammunition did not make it popular compared with the
8 machine gun version, the machine lost about 8 mph in
top speed. The Air Ministry approached Hawker about a
4 20 mm cannon version, but it took until June 1940 to
begin the project. In August 1940 Hurricane V7360 was
modified and took part in patrols starting at the end of
August, by September 15 eight Hurricane IIs were being
fitted with cannon. Problems were encountered from the
long protruding cannon barrels.
An order for 30 cannon Hurricanes was made in November
1940, V7360 flying first on 5 December, then in January
1941 the orders were placed for another 100, upped by
another 200 in February.
Spitfire L1007 was also fitted with a pair of internally mounted
20 mm cannon around the same time as L1750 received it's
external mountings. The Spitfire had jamming problems but
during trials on 13 January 1940 helped shoot down a He111.
The higher muzzle velocity showed up with an increase in
firing accuracy. An order for 30 was placed in 1940 with 24
of the aircraft delivered by 16 August 1940. Apart from the
ammunition feed problems aeroelasticity in the wing meant
tight manoeuvres could cause the ammunition drum to come
into contact with the wing's surface and jam. By August the
2 cannon 4 machine gun wing was being trialled Modified
cannon Spitfire Is (finally called Mark IB) were issued in
October 1940. Most of the mark1Bs were ultimately converted
to mark VBs, again a loss of performance was noted compared
with the 8 machine gun version.
Sources Spitfire by Morgan and Shacklady, British Interceptor
Fighters by Bowyer.
>This installation in the
>thin-winged Spitfire was a problem since the cannon had to be turned partly
>on its side to be accommodated and still required blisters to contain the
>breech. There were inordinate gun-jamming problems with this arrangement
>and 19 squadron - the first to get cannon-armed Spitfires - reverted to the
>8-Browning version. In contrast to the Spitfire, the Hurricane had thicker
>wings and was, later, fitted with four wing-mounted cannon without
>difficulty.
Yes, note the Spitfire was reworked to 2 20 mm and 4 0.303
machine guns. Note there was a need to rework the ammunition
feed system for the Hurricane as well, but yes the thicker wing
made it easier to install cannon.
>Although the Air Staff might have been unaware of the tactical
>considerations when the decision was made to fit cannon to Spitfires, the
>Hurricane, as the less nimble aircraft but a steadier gun platform, was the
>obvious aircraft to take on bombers with increasing armour protection, where
>the sustained weight of fire from cannon was important. The more
>manoeuvrable Spitfire, however, was the obvious candidate for
>fighter-on-fighter engagements. With fleeting opportunities with your enemy
>in your sights, the advantages of faster-firing machine guns would be
>obvious. Indeed, many pilots - including Bader - preferred a machine gun to
>a cannon armament for dogfighting at the time.
Welcome to the debate about whether a large number of small
bullets is better than a smaller number of larger bullets/shells,
with the addiitonal trade offs on ammunition supply and weight
of the weapons.
Firstly there was no guarantee the Spifires would only encounter
fighters. Then there was the fact the Hurricane was due to be
replaced by the Typhoon (which originally was postulated to
come in 12 0.303, 8 0.50 cal or 4 20mm gun versions). The
20 mm cannon had a higher muzzle velocity, making shooting
more accurate and the high explosive made hits more deadly.
The overall increase in aircraft size and defensive armour
demanded an increase in fighter firepower.
The Spitfire was going to be the RAF's main interceptor at
least until 1942 under the 1940 plans, it was already clear
the Hurricane could not be modified to match the Bf109 in
performance.
Note according to Bader's biography he changed his mind later
about the merits of cannon.
>Why was the possibility of mounting the cannon under the Spitfire's wing
>considered? This presumably would have cured the gun-jam problem. This
>configuration was not unknown at the time - the French were considering
>fitting the MS406 with a Merlin in place of the Hispano-Suiza "moteur canon"
>before the war and proposed two cannons slung under the wing.
Under wing installations are even worse than partially in wing
solutions, see the comments of all those Bf109G pilots with
underwing cannon, the installation has to include the gun and
ammunition. Also it was the ammunition feed to the gun that
had originally had problems and the Spitfire installation
aggravated this.
Geoffrey Sinclair
Remove the nb for email.
Gavin Bailey
> I have been unable to find why, in 1939/40, the Spitfire was chosen over the
> Hurricane for installation of the Hispano cannon.
The short answer is that it wasn't: a cannon-armed Hurricane was
operationally tested in the Battle of Britain, and production of the
four-cannon armed Hurricane IIc began in 1941.
> The more
> manoeuvrable Spitfire, however, was the obvious candidate for
> fighter-on-fighter engagements. With fleeting opportunities with your enemy
> in your sights, the advantages of faster-firing machine guns would be
> obvious. Indeed, many pilots - including Bader - preferred a machine gun to
> a cannon armament for dogfighting at the time.
The verdict of the majority of pilots who expressed a preference at the
time were clearly in favour of cannon - e.g. John Kent, who commanded 92
Squadron in late '40 - early '41 when they got Spitfire Ibs (for the
second time, after their brief and unsuccessful use in September 1940)
and then Spitfire Vbs with cannon. Multiple hits from .303 were
frequently not enough to cause immediately fatal damage to enemy
aircraft - fighters included.
> Why was the possibility of mounting the cannon under the Spitfire's wing
> considered? This presumably would have cured the gun-jam problem. This
> configuration was not unknown at the time - the French were considering
> fitting the MS406 with a Merlin in place of the Hispano-Suiza "moteur canon"
> before the war and proposed two cannons slung under the wing.
This is what they tried with the Hurricane, initially. It caused
aerodynamic penalties similar to those complained about by Bf 109 G6/R6
pilots with the same arrangement. Installing cannon in the body of the
wing was a better option.
Gavin Bailey
--
Emmanuel Gustin
news:ab73k9$1rke$1...@nntp6.u.washington.edu...
> I have been unable to find why, in 1939/40, the Spitfire was chosen over
the
> Hurricane for installation of the Hispano cannon.
The Hawker and Supermarine teams were, as always, competing.
Supermarine made a much earlier start; a Spitfire was fitted with
a cannon in each wing in June 1939. Hawker initially exploited
the thick wing by fitting twelve .303"s (not possible in a Spitfire,
of course, as they were quick to point out), but that installation
was not very useful because of poor accessibility of the outer
guns.
Hawker converted a Hurricane Mk.I as a testbed for Hispano
cannon, but that flew in June 1940, when the first cannon-armed
Spitfires Mk.IB were already being delivered for service testing.
And Hawker's first installation was purely experimental;
the weapon was installed in a fairing under the wing of an early
production Hurricane (one with a fabric-covered wing).
The detail design of the production cannon-armed Hurricane,
with guns installed internally, was quite different.
Leslie Appleton claimed [in "Sydney Camm and the Hurricane",
ed. by John W. Fozard] that the Hurricane cannon wing was
designed "merely to help towards a decision for the armament
of the Typhoon" and that its use in combat was fortuitous.
He was responsible to aircraft armament development at Hawker's,
so he ought to know --- but there was also a RAF requirement
for cannon-armed fighters, so he may have been exaggerating.
In any case, Sidney Camm's team had to work on the N and R
fighters, and that probably slowed Hurricane work down:
You don't want to put too much effort into refining an already
obsolescent design while you are working on a replacement.
In contrast, the Spitfire was a suitable platform for future
development, so Joe Smith's team could concentrate its efforts
on it.
The Spitfire had the disadvantage of the thinner wing, but
the Hurricane had the more serious disadvantage of inferior
performance. The air staff seems to have felt that the Spitfire
could carry the additional weight and drag of cannon while
retaining a sufficient performance. The Hurricane, on the other
hand, really needed the more powerful Merlin XX engine
before a version with four cannon could be put into service.
Four cannon-armed Hurricanes Mk.I were built, but their
top speed was only 465 km/h, and that was not acceptable.
The Mk.IIC did not arrive until early 1941, also because
it was then considered a fighter-bomber and fighter for use
overseas, and so did not receive priority for the still scarce
cannon.
> thin-winged Spitfire was a problem since the cannon had to
> be turned partly on its side to be accommodated and still
> required blisters to contain the breech.
Not the breech, but the ammunition drum and later the belt-feed
mechanism. Actually the more serious problem was the insufficient
stiffness of the mount. The Hispano required separate support
points for the breech end and the sliding barrel. If the link between
these was not stiff enough, it would not function properly.
The HS.404 cannon had been designed as an engine cannon
for the Hispano-Suiza 12X and 12Y series of engines, with
the engine block providing suitable mounting points; its
installation in a wing (which always flexes a bit) was much
more difficult.
Hawker also had problems with their first cannon installation,
and had to do some redesign work to absorb the recoil better.
But they had more time to do so, the cannon-armed Spitfire
were rushed into combat.
> With fleeting opportunities with your enemy in your sights,
> the advantages of faster-firing machine guns would be obvious.
> Indeed, many pilots - including Bader - preferred a machine
> gun to a cannon armament for dogfighting at the time.
This controvery of course lead the 'universal wing' for
the Spitfire and Typhoon, able to accept various armament
combinations. With hindsight this was a bad decision,
demanding unnecessary design work that slowed down
deliveries. Cannon became the standard armament.
(There is the excuse of availability, however. Only 432
Hispano cannon were produced in 1939 and 3360 in 1940.
In 1941 BMARC and BSA delivered 12,022 cannon,
and production of the .303" was allowed to level out.)
The problem was the insufficient hitting power of the .303",
even against fighters. Germans fighters and bombers were both
being equipped with armour and self-sealing fuel tanks (better,
apparently, than their British equivalents) and the machine gun
was rapidly losing its effectiveness (which, as experience in
Norway and Spain showed, was not very great against modern
combat aircraft anyway.) Of course the rate of fire of the .303"
is about twice that of the Hispano Mk.II, but in effective firepower
a single cannon was worth about a dozen rifle-calibre machineguns.
The problem with the cannon was that they were not ready;
the mounts were not yet designed properly, the belt feeds were
still missing (60-rounds drums were not very practical) and
the explosive ammunition had fuses that were too fast (they
exploded before penetrating). So during the Battle of Britain
the .303" was still a more suitable weapon. That applied for
both fighters.
--
Emmanuel Gustin <gus...@NoSpam.uia.ac.be>
Fighter Guns Page: http://www.geocities.com/CapeCanaveral/Hangar/8217/
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