Development
In late 1941 and early 1942, the
Admiralty assessed the Spitfire for possible conversion.
In
late 1941 48 Spitfire Mk. Vb were converted by Air Training Service Ltd. at
Hamble to become "hooked Spitfires".
This was the Seafire Mk.
Ib
and would be the first of several Seafire variants to reach the Royal Navy's
Fleet Air Arm. This version of the Seafire was mainly used to allow the
Royal Navy to gain experience in operating the Spitfire on aircraft
carriers. The main structural change was made to the lower rear fuselage
which incorporated an A-frame style arrestor hook and strengthened lower
longerons.
It was
soon discovered that the fuselage, especially around hatches, was too weak
for sustained carrier operations. In an attempt to alleviate this condition,
reinforcing strips were riveted around hatch openings and along the main
fuselage longerons.
A
further 118 Seafire Ibs incorporating the fuselage reinforcements were
modified from Spitfire Vbs by Cunliffe-Owen at Eastleigh and Air Training
Service. These aircraft were equipped with Naval HFradio equipment and IFF
equipment as well as a Type 72 homing beacon. In these and all subsequent
Seafires the instruments were re-calibrated to read kn and nmi rather than
mph and mi. The fixed armament was the same as that of the Spitfire Vb; two
20 mm (.79 in) Hispano Mk II cannon with 60 rpg fed from a "drum" magazine,
and four .303 in (7.7 mm) Browning machine guns with 350 rpg.
Provision was also made to carry a 30 gal (136 l) "slipper" fuel tank under
the fuselage.
One
frontline unit, 801 Squadron operated this version on board HMS Furious from
October 1942 through to September 1944.
The
second semi-navalised variant of the Seafire, and the first to be built as
such, was the Seafire F. Mk IIc which was based on the Spitfire Vc.
The Vc
had several major refinements over the Spitfire Vb.
Apart from the modifications included in the main batch of Seafire Ibs this
version incorporated catapult spools,and a single slinging lug on either
side of the fuselage, just behind the engine bulkhead.
Three basic subtypes were produced, the F
Mk.
IIc
and F.R Mk IIc (fighter reconnaissance), powered by a Merlin 46, and the L.
Mk IIc powered by a low altitude Merlin 32 specifically manufactured for
naval use This version of the Merlin used a "cropped" supercharger impellor
to provide greater power at low altitudes than the standard engines;
delivering 1,585 hp (1,182 kW) at 2,750 ft (838 m). Both engine models drove
a four bladed 10 ft 9 in (3.28 m) diameter Rotol propeller.
Because
this version used the "C" wing the Hispano cannon were now fed from a
120-round belt magazine, otherwise the armament was the same as that of the
Ib; the F.R also carried two F.24 aerial cameras.
After trials of Rocket Assisted Take Off Gear or RATOG apparatus (small
rocket engines which could be attached to the fuselage or wings of aircraft
to help shorten the take-off run) in February 1943, this equipment became a
standard fitting available for all Seafires.
The
IIc was the first of the Seafires to be deployed operationally in large
numbers, with Supermarine building 262 and 110 being built by Westland, who
also built 30 Seafire Mk III (Hybrid) (Mk IIIs without folding wings).
Although developed for aircraft carrier use, this version still lacked the
folding wings needed to allow them to be used on board some Royal Navy
carriers, some of which had small aircraft elevators unable to accommodate
the full wingspan of the Seafires.
The Seafire F. Mk. III was the first true
carrier adaptation of the Spitfire design. It was developed from the Seafire
Mk. IIC, but incorporated manually folding wings allowing more of these
aircraft to be spotted on deck or in the hangers below. Supermarine devised
a system of two straight chordwise folds; a break was introduced immediately
outboard of the wheel-wells from which the wing hinged upwards and slightly
angled towards the fuselage. A second hinge at each wingtip join allowed the
tips to fold down (when the wings were folded the wingtips were folded
outwards). This version used the more powerful Merlin 55 (F. Mk. III and F.R.
Mk III) or Merlin 55M (L. Mk. III), driving the same four-bladed propeller
unit used by the IIC series; the Merlin 55M was another version of the
Merlin modified to give maximum performance at low altitude. Other
modifications that were made on the Spitfire made their way to the Seafire
as well including a slim Aero-Vee air filter and six-stack ejector type
exhausts.
In
addition the shorter barreled, lightweight Hispano Mk V cannon were
introduced during production as were overload fuel tank fittings in the
wings. This Mark was built in larger numbers than any other Seafire variant;
of the 1,220 manufactured Westland built 870 and Cunliffe Owen 350. In 1947
12 Mk IIIs were stripped of their naval equipment by Supermarine and
delivered to the Irish Air Corps
After the Mk III series the next Seafire variant to appear was the Seafire
F. Mk XV, which was powered by a Griffon VI (single-stage supercharger,
rated at 1,850 hp (1,379 kW) at 2,000 ft (610 ft) driving a 10 ft 5 in Rotol
propeller. Designed in response to Specification N.4/43 this appeared to be
a navalised Spitfire F. Mk XII; in reality the Mk XV was an amalgamation of
a strengthened Seafire III airframe and wings with the wing fuel tanks,
retractable tailwheel, larger elevators and broad-chord "pointed" rudder of
the Spitfire VIII.
In addition, the engine cowling
was different to that of the Spitfire XII series, being secured with a
larger number of fasteners and lacking the acorn shaped blister behind the
spinner. The final 30 Mk XVs were built with the blown "teardrop" cockpit
canopy and cut down rear fuselage introduced on the Spitfire Mk XVI.
On
the first 50 aircraft manufactured by Cunliffe-Owen a heavier, strengthened
A-frame arrestor hook was fitted to cope with the greater weight. On
subsequent Mk XVs a new form of "sting" type arrestor hook was used; this
version was attached to the reinforced rudder post at the rear of the
fuselage and was housed in a fairing below the base of the shortened rudder.
A vee-shaped guard forward of the tailwheel prevented arrestor wires getting
tangled up with the tailwheel.
390 Seafire XVs were built by
Cunliffe-Owen and Westland from late 1944. Six prototypes had been built by
Supermarine.
One
problem which immediately surfaced was the poor deck behaviour of this mark,
especially on take-off.
At full
power the slipstream of the propeller, which swung to the left (as opposed
to the Merlin, which swung to the right), often forced the Spitfire to swing
to starboard, even with the rudder hard over on opposite lock. This
sometimes led to a collision with the carrier's island. The undercarriage
oleo legs were still the same of those of the much lighter Merlin engined
Spitfires, meaning that the swing was often accompanied by a series of hops.
As an interim measure it was recommended that pilots avoid using full power
on take-off (+10 lb "boost" maximum was recommended). There were also
problems involved with this swing being strongly accentuated in the event of
an asymmetric firing of the RATOG equipment.
In
the event none of the "first generation" Griffon-engine Seafires were to use
RATOG at sea unless they were ranged forward of the first crash barrier on
deck.
The Seafire F Mk. XVII was essentially a
modified Mk XV; the most important change was the reinforced main
undercarriage which used longer oleos and a lower rebound ratio. This went
some way towards taming the deck behaviour of the Mk XV, reduced the
propensity of the propeller tips "pecking" the deck during an arrested
landing, and the softer oleos stopped the aircraft from occasionally
bouncing over the arrestor wires and into the crash barrier. Most production
XVIIs had the cut down rear fuselage and teardrop canopy (the windscreen was
modified to a rounded section, with narrow quarter windows, rather than the
flat windscreen used on Spitfires) and an extra 33 gallon fuel tank fitted
in the rear fuselage.
In
addition the wings were reinforced, with a stronger mainspar necessitated by
the new undercarriage, and they were able to carry heavier underwing loads
than previous Seafire variants. 232 of this variant were built by Westland
(212) and Cunliffe-Owen(20).
The Seafire F. and F.R Mk. 45 was the
next version of the Seafire to be built, and the first to use a Griffon 60
series engine with a two-stage, two speed supercharger.
The
prototype TM379 had been modified from a Spitfire F. Mk 21 prototype by
Cunliffe-Owen and featured a "sting" type arrestor hook.
Because
this version was considered to be an "interim" type the wing, which was
unchanged from that of the Spitfire 21, was non-folding.
The
Seafire F. Mk 45 entered service with 778 Squadron in November 1946 and a
few were modified to F. R Mk 45s in March 1947 by being fitted with two F.24
cameras in the rear fuselage. Fifty F. Mk 45s were built by the Castle
Bromwich factory.
The Seafire F. and F.R Mk. 46 was a
Spitfire F. Mk 22 modified to naval standard and featured the cut down rear
fuselage and "teardrop" canopy. Again the wing had not been modified to fold.
The electrical equipment was changed from using a 12 volt system to one
using 24 volts.
In
April 1947 a decision was made to replace the Griffon 61s or 64s driving a
five bladed Rotol propeller unit with Griffon 85s or 87s driving two three
bladed Rotol contra-rotating propellers. In addition, all but the first few
incorporated larger tail units from the Spiteful and Seafang.
These
two changes completely transformed the handling characteristics of the
aircraft by eliminating the powerful swing to starboard of previous Griffon
engined variants.
200
of the Mk 46s were ordered but only 24 were built, all by Supermarine.
The
final version of the Seafire was the Seafire F. and F.R Mk. 47.
There
was no true prototype, instead the first production aircraft PS944 and PS945
served as trials aircraft. As the "definitive" carrier based Seafire the Mk
47 incorporated several refinements over earlier variants. After the first
four aircraft, with manually folded wings, the Mk 47 incorporated
hydraulically powered wing folding, the outer wings folding upwards in one
piece, without the folding wingtips of earlier marks. All Mk 47s adopted the
Rotol contra-rotating propellers as standard. The Mk 47 also featured a long
supercharger air-duct, the intake of which started just behind the spinner,
and a modified curved windscreen, similar to that used on the Mk XVII. Other
features unique to the Mk 47s were the modified horizontal tail units, which
used spring-loaded elevator tabs, a large inertia weight in the elevator
control system and beading on the trailing edges of the elevators. These
changes improved longitudinal stability, especially when the aircraft was
fully loaded. The modified windscreen proved to be unpopular with pilots
because of continual problems with misting, and the thicker, repositioned
frames obstructed visibility during deck landings. In spite of
recommendations to change the windscreen back to a standard Spitfire 24 unit,
this was never done. Performance tests showed that the Mk 47 was slightly
slower than the Mk 46 in maximum and climbing speeds, mainly due to the long
supercharger air intake, which was less efficient than the shorter type
fitted to earlier Seafires.
The
Seafire 47 saw action with 800 Squadron on board HMS Triumph during the
Malayan Emergency of 1949 and during the Korean War in 1950. However, in
1951 all Seafires were withdrawn from front-line service. In all 90 F. and
F.R Mk 47s were built, all by Supermarine.
The
last aircraft of the 22,000 of the entire Spitfire/Seafire lineage VR971
left the production line at Supermarine on 28 January 1949.
Assessment
The Spitfire's original role, and the one
at which it proved to be a formidable aircraft was that of short-range
land-based interceptor. As a carrier based fighter the design was a
compromise and, once in service, suffered from a high attrition rate through
structural damage caused by heavy landings on carrier decks: this problem
continued even with the stiffening introduced by the Mk II. Also, the
Seafire had a narrow undercarriage track, which meant that it was not well
suited to deck operations. The many modifications had shifted the
centre-of-gravity aft, making low-speed control difficult, and the
aircraft's gradual stall characteristics meant that it was difficult to land
accurately on the carrier, resulting in a very high accident rate.
Other problems included the basic Spitfire's short range and endurance (fine
for an interceptor fighter, but not for carrier operation), limited weapons
load and that it was dangerous in ditching. The first Seafire variant to
overcome many of these problems was the Mk XVII with its new undercarriage
design, reinforced structure and extra fuel tanks, although there were still
some compromises, and it entered service well after the war was over.
The
low point of Seafire operations came during Operation Avalanche the invasion
of Salerno in September 1943.
Of the
106 Seafires available to the British escort carriers on 9 September only 39
of these were serviceable by the dawn of D-Day plus Two (11 September). Part
of this was attributed to flat, calm conditions meaning that there was not
enough headwind to stop the "Spitfire float" on landing: many Seafires
missed picking up the arrestor wires and flew into the crash barriers while
others had their arrestor hooks pulled off the fuselage because they caught
the wires at too high a speed.
In
spite of these problems the Seafire, especially the L. Mk II and III with
their low altitude rated Merlin engines found a role as a low to medium
altitude interceptor able to protect the RAN carrier fleet.
Operational history
Compared with other naval fighters, the Seafire II was able
to outperform the A6M5 (Zero) at low altitudes when the two
types were tested against each other in World War II.
Contemporary Allied carrier aircraft which were designed
from the ground up as naval fighters, such as the F6F
Hellcat and the F4U Corsair, however, were considerably more
robust and generally more powerful. The more powerful
Seafire III, though, still enjoyed better climb rates and
acceleration than these other fighters. Late-war Seafire
marks equipped with the Griffon
engines enjoyed a considerable increase of performance
compared to their Merlin-engined predecessors. However the
Griffon powered Seafires had some serious faults. The main
problem was a result of the increased power yielded by the
Griffon engine; the increase in torque meant the pilot had
to continuously correct the flight of the aircraft (to
prevent the frame of the aircraft rotating in the other
direction to that of the propeller). This was huge problem
when attempting to take off and land from an aircraft
carrier. The torque also affected the lift of the right wing
(the Griffon engines rotated anti-clockwise) which would
lose lift and even stall at reasonable speeds. The increased
weight of the engine meant that the take-off had to be
longer and proved very dangerous from most British carriers.
The increased weight of the engine further affected the
centre of gravity that Mitchell had concentrated on so
carefully in the original Spitfire. As a result the handling
of the aircraft suffered. Eventually most of these problems
were fixed in Seafire 47 when the 6 bladed contra-rotating
propeller was adapted.
The first use of Seafires in sustained carrier operations
was Operation Torch. Seafires saw most service in the Far
East Pacific campaigns, serving with No. 887 and 894
Squadrons, Fleet Air Arm, aboard
HMS Indefatigable
and joining the British Pacific Fleet late in 1944. Due to
their good high altitude performance and lack of
ordnance-carrying capabilities (compared to the Hellcats and
Corsairs of the Fleet) the Seafires were allocated the vital
defensive duties of Combat Air
Patrol (CAP) over the fleet. Seafires were thus heavily
involved in countering the
kamikaze attacks during the
Iwo Jima landings and beyond.
The Seafires' best day was
15 August 1945,
shooting down eight attacking aircraft for a single loss.
During the campaign 887 NAS claimed 12 kills, and 894 NAS
claimed 10 kills (with two more claims earlier in 1944 over
Norway).
The top scoring Seafire pilot of the
war was Sub-Lieutenant R.H. Reynolds
DSC of
894, who claimed 4.5 air victories in 1944–5.
Post war, the Fleet Air Arm replaced
its Merlin powered Seafires with Griffon powered aircraft,
initially with the Seafire Mk XV and Mk 17, and from 1948,
by the definitive Seafire Mk 47. In 1950, Triumph
started a tour of the Far East, embarking 800 Naval Air
Squadron with Seafire 47s along with 827 Naval Air Squadron
equipped with Fairey Fireflys. Following the outbreak of the
Korean War, Triumph was
diverted to operations to try and stem the North Korean
offensive, Seafires flying both ground attack and combat air
patrol missions from July until September 1950, when
Triumph was replaced on station by
HMS Theseus,
equipped with Sea Furys. During operations off Korea,
Seafires flew 360 operational sorties, losing one aircraft
shot down by friendly fire from
a B-29 Superfortress and a second aircraft lost when its
arrestor hook failed to extend. The Seafire, however, proved
more vulnerable to the stresses of carrier operation with
many aircraft suffering wrinkling of the rear fuselage
brought about by heavy landings. Following the end of
operations, when peacetime airworthiness rules were
re-imposed, all but three of 800 Squadron's Seafires were
declared unserviciable owing to wrinkling.
The Royal Canadian Navy and French
Aviation navale also obtained Seafires to operate from ex
Royal Navy aircraft carriers following the end of World War
II. Canada's Seafire Mk XVs were flown from HMCS
Magnificent
and HMS Warrior
before being replaced by Sea Furies in 1948. France received
65 Seafire Mk IIIs, 24 of these being deployed on the
carrier Arromanches
in 1948 when it sailed for Vietnam to fight in the First
Indochina War, the Seafires operating both from land bases
and from Arromanches on ground attack missions
against the Viet Minh before being withdrawn from combat
operations in January 1949. After returning to European
waters, the Seafire units were re-equipped with Seafire XVs,
but these were quickly replaced by F6F Hellcats from 1950.
The
Irish Air Corps operated Seafires for a time after the war,
despite having no naval air service nor aircraft carriers.
The aircraft were operated from Baldonnel (Casement
Aerodrome) much in the same way as normal Spitfires, but
retaining the folding wings. An attempt to recycle the
Merlin engines was made in the 1950s, by replacing the
ailing Bedford engine in a Churchill tank with an engine
from a scrapped Seafire. The project collapsed from lack of
funds.
In
the Fleet Air Arm, both Spitfires and Seafires were used by
a number of squadrons, the Spitfires used by training and
land based squadrons. Eleven operational squadrons (800
series) used Spitfires and Seafires.