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WWII Tech Pubs Briefing
Vickers-Supermarine
Spitfire Mks.I and II
Written by
Duane Godwin
East of Dunkirk,
Spitfires from 602 Sqn down a Bf 109 as part of the frantic effort to
provide air cover the BEF as it evacuates under continuous Luftwaffe assault.
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Country of Origin:
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Great
Britain
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Manufacturer:
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Supermarine Aviation Works (Vickers
Ltd ) Southampton; Castle Bromwich, Westland Aircraft.
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Designer:
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RJ Mitchell (died 1937). Joseph
Smith took over position as Chief Designer.
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Major Variants:
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Mk.I; Mk.II
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Role:
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Single-Seat Fighter; Air
Sea
Rescue
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Operated by:
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Great
Britain, France (1), Portugal, Turkey (2). Various other nationalities represented in Royal Air Force
including Canadian, Czech, Polish, and American (Eagle) squadrons.
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First Flight:
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Prototype ( K5054 ) -
5th March 1936. First production flight 14th May 1938.
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In Service:
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August 4th 1938. Delivered to No 19 Squadron based at Duxford .
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Number Built:
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2,549 (Prototype – Mk.II)
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Overview
The Supermarine Spitfire is probably
the most famous fighter aircraft of all time, and arguably one of the
most beautiful, with its unmistakable elliptical wings and sleek lines.
The Spitfire was based on the Rolls-Royce-Goshawk-powered Supermarine
Type 224, designer Reginald Mitchell’s ugly gull-winged entry into the
1934 British Air Ministry Specification F7/30 fighter competition. The
224 was a disappointment, but Mitchell persevered with development.
Mitchell decided to fit the new
Rolls Royce PV12 engine (soon to be renamed the Merlin) and refined the
design, introducing retractable landing gear and the familiar elliptical
wings. The new Type 300 showed such promise that the Air Ministry drew
up a specification (F37/34) and funded the prototype. The all-metal Type
300 was a stressed-skin, low-wing monoplane with a tail skid and a fixed-pitch,
two-blade wooden propeller. Soon after its first flight, Mar. 5, 1936,
the Air Ministry ordered 310 Spitfires. Mitchell, ill with cancer since
1933, died June 1937.
Supermarine immediately ran into
problems. The small company only had experience building small quantities
of flying boats and a few racing seaplanes - “Supermarine”, the opposite
of “submarine”, means flying boat. Other companies signed on to build
parts of the aircraft (around 80% of the construction), but the technology
to build this advanced fighter was just too much for the unskilled labor
that was available. Nine months after construction began, only a few
pairs of wings and fuselages were complete and the Spitfire order was
very nearly canceled. Furthermore, the eight machine guns froze up at
high altitudes. It took over a year to develop effective gun heating.
But the production problems were sorted out, and the first production
Spitfire Mk.I flew May 1938. It differed from the prototype in that it
had a tail wheel, a stiffer wing, a bigger fuel tank, and increased flap
travel.
By 1939, about 50 Spitfires had
been delivered; the first squadron to equip was 19 Squadron at Duxford.
The first Mk.I Spitfires employed the Merlin II engine driving a two-blade,
fixed-pitch propeller, and only four of the eight planned .303-in (7.7-mm)
Browning machine guns due to a shortage. Supermarine introduced improvements
during production: the bulged canopy (starting with aircraft no. 8); a
two-position, three-bladed propeller (no. 74); and the Merlin III engine
with a Rotol or de Havilland three-bladed, constant-speed propeller (no.
194). Armour protection improved in stages.
By 1939, about 50 Spitfires had
been delivered; the first squadron to equip was 19 Squadron at Duxford.
The first Mk.I Spitfires employed the Merlin II engine driving a two-blade,
fixed-pitch propeller, and only four of the eight planned .303-in (7.7-mm)
Browning machine guns due to a shortage. Supermarine introduced improvements
during production: the bulged canopy (starting with aircraft no. 8); a
two-position, three-bladed propeller (no. 74); and the Merlin III engine
with a Rotol or de Havilland three-bladed, constant-speed propeller (no.
194). Armour protection improved in stages.
When Britain
declared war on Germany
and sent forces to France,
it considered the Spitfire too valuable to risk and retained the planes
in Britain.
Spitfires started flying sorties from southern England
May 12, and were committed in large numbers as the fighting moved closer
to the English Channel. Spitfires shot down about
260 aircraft during the Dunkirk
evacuation at a cost of 72 losses.
The Mk.Ib introduced
two wing-mounted Hispano 20-mm (0.79-in) cannon, each fed by a
60-round drum. Initially, wing flexing often jammed the cannons and four
Browning machine guns were later added as a supplement. Only a few Mk.Ibs
were built. The machine-gun-armed Spitfire was retroactively renamed
the Mk.Ia.
The Spitfire offered performance
similar to that of the superb Bf 109E. It was slightly faster than the
109 below 15,000 ft (4,500 m), and slower above. The 109 out climbed
the Spitfire, but the Spitfire held the edge in a turning fight. The
109 and its fuel-injected engine could perform negative-G nose-overs that
the Spitfire could not follow because its carburettor-aspirated Merlin
cut out during negative-G manoeuvres.
The Mk.II entered the
Battle of Britain in August. A more powerful version built by the Castle
Bromwich Aircraft Factory; it used the Rolls-Royce Merlin XII. A cannon-armed
Mk.II was built in small numbers, and a long-range version was used as
an escort and on intruder raids. Lastly, a dedicated Air Sea Rescue Spitfire
was created by converting Mk.IIb’s.
The top Spitfire Mk.I ace was Eric
Lock with 23 victories (three more on the Mk.V). Other Mk.I aces include
the Kiwis Colin Gray, Brian Carbury, and “Al” Deere, South African air
tactician “Sailor” Malan, and “Bob” Tuck.
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Variants
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Type
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Variant
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Number
Built
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Remarks
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Prototype (K5054)
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-
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One
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Single-seat, single-engine, low-winged
monoplane with all-metal stressed skin monocoque construction. Immensely
strong elliptical wing, Alclad skinning overall, fabric-covered
control surfaces, narrow-tracked outwards retracting main undercarriage,
and tailskid. Large radiator under starboard wing, oil cooler under
port wing. Powered by Rolls-Royce Merlin “C” driving two-bladed
fixed pitch wooden propeller. Change to Merlin “F” (became Merlin
II), different propeller, and ejector exhausts boosted speed to
required 350 mph. Eight BSA Browning 0.303 in (7.7
mm) belt-fed machine guns in wings.
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Mk.I
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Mk.I
(later Mk.Ia)
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1,537
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Similar to Prototype. Tail skid replaced
with tail wheel, stiffer wing, larger fuel tank, and increased flap
travel. Powered by Rolls-Royce Merlin II driving two-bladed fixed
pitch wooden propeller. Improvements made during production run
were bulged canopy (from aircraft no. 8); two-position, three-bladed
propeller (no. 74); and Merlin III engine with Rotol or de Havilland
three-bladed, constant-speed propeller (no. 194), better armour
protection, and gun camera.
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Mk.Ib
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30
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Cannon equipped version of Mk.I. Initially
with 2x Hispano 20 mm cannon in wings; later with definitive B wing
(2x Hispano 20 mm cannon and 4x 0.303 in (7.7 mm) belt-fed machine guns in wings).
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High Speed Spitfire
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One
(converted from
Mk.I)
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Converted Mk.I for planned attempt
on World Speed Record. Streamlined canopy, reduced wing span with
clipped wings, modified cooling system, Watts fixed-pitch four-bladed wooden propeller, and tail skid. Powered
by Rolls-Royce Merlin II Special (2,100 hp – 1,550kW)
running on special fuel. Estimated top speed at sea level was about
400 mph (644 km/h). Attempt abandoned
after Heinkel He 100 reached 464 mph (747 km/h) in March 1939 and Messerschmitt Me 209 achieved
469 mph (755 km/h) in April. Fitted
with a Merlin XII, its reduced fuel capacity was inadequate for
use on operations. Saw out the war as a hack in the Photographic
Reconnaissance Unit, and was scrapped.
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Mk.II
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Mk.IIa
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751
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Minor development of Spitfire Mk.I
built exclusively by Castle Bromwich Aircraft Factory in Birmingham.
Powered by Rolls-Royce Merlin XII that could use 100 octane fuel,
allowing higher boost, and therefore more power. Also used Coffman
starter cartridge instead of electric starter.
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Mk.IIa
(LR)
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60
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Version of Mk.IIa with fixed 30 gallon
(136 l) tank fitted under port wing. The asymmetric configuration
caused handling problems, and increased drag affected top speed.
Famously, on July 24, 1941, Mk.II (LR) Spitfires escorted the bombers that attacked the Gneisenau
in Brest
harbour.
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Mk.IIb
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170
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Cannon equipped version of Mk.II.
B wing (2x Hispano 20 mm cannon and 4x 0.303 in (7.7 mm) belt-fed machine guns in wings), but with revised
feed and ejection system. Cannon mounted on their sides which solved
jamming problem encountered in Mk.Ib, and introduced the “B wing
blister” on top of wing.
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(ASR)
Mk.IIc
later ASR Mk.II
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50
(converted from
Mk.IIb)
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Version of Mk.II used in Air Sea Rescue
role. Survival and rescue gear (including flares, rations, a dinghy,
and smoke bombs) was stowed internally behind the pilot. These were
dropped through the existing flare chutes under the fuselage. Smoke
bombs could be carried under the wings on racks. Powered by Rolls-Royce
Merlin XX of 1,460 hp (1,089 kW).
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Specifications
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Model
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Prototype (K5054)
Supermarine Type
300
Figures for aircraft fitted with Merlin “C”
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Mk.Ia
Supermarine Type
300
Figures for aircraft fitted with Merlin III
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Mk.IIa
Supermarine Type
329
Figures for aircraft fitted with Merlin XII
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First Flight
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Mar. 5, 1936
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May 14, 1938
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Sept. 24 1939
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Into Service
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-
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August
1938
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August
1940
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Dimensions
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Span
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36
ft 10 in (11.23 m)
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36
ft 10 in (11.23 m)
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36
ft 10 in (11.23 m)
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Length
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29
ft 11 in (9.12 m)
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29
ft 11 in (9.12 m)
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29
ft 11 in (9.12 m)
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Height
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8
ft 2 ˝ in (2.5 m)
Tip of Prop:
12 ft 8 in (3.86 m)
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Tip
of Prop:
11 ft 5 in (3.23 m)
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Tip
of Prop:
11 ft 5 ˝ in (3.48 m)
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Wing Area
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242
sq ft (22.5 sq m)
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242
sq ft (22.5 sq m)
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242
sq ft (22.5 sq m)
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Powerplant
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Type
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Rolls-Royce Merlin C, then
Rolls-Royce Merlin F, then
Rolls-Royce Merlin II
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Rolls-Royce Merlin II
(1st 64), then
Rolls-Royce Merlin III
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Rolls-Royce Merlin XII
some
Rolls-Royce Merlin 45
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Cubic Capacity
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12-cylinder
Vee
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12-cylinder
Vee
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12-cylinder
Vee
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Cylinders
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1,647
in3 (27 l)
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1,647
in3 (27 l)
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1,647
in3 (27 l)
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Horsepower
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Merlin C: 990 hp (738
kW)
Merlin F: 1,035 hp (772 kW)
Merlin II: 1,030 hp (768 kW)
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Merlin II: 1,030 hp (768
kW)
Merlin III: 1,030 hp (768 kW)
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Merlin XII: 1,175 hp
(876 kW)
Merlin 45: 1,210 hp (897 kW)
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Weights
and Loads (note - these figures vary for individual aircraft, and are often not
directly comparable)
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Weight (Max. Take-off)
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5,200
lb (2,360 kg)
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6,200
lb (2,812 kg)
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6,275
lb (2,850 kg)
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Weight (Normal Loaded)
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Unknown
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5,844
lb (2,651 kg)
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Unknown
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Weight (Empty)
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5,034
lb (2,280 kg)
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4,810
lb (2,182 kg)
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4,783
lb (2,170 kg)
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Performance
(note - these
figures vary for individual aircraft, and are often not directly
comparable)
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Maximum Speed
at Altitude
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349
mph at 16,800 ft
(562 km/h at 5,120 m)
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363
mph at 18,500 ft
(583 km/h at 5,640 m)
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357
mph at 17,000 ft
(575 km/h at 5,180 m)
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Stalling Speed
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Unknown
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Flaps
and gear up
73 mph (117 km/h)
Flaps and gear up
74 mph (119 km/h)
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Unknown
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Climb
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6 min 25 sec
to 15,000 ft (4,570 m)
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2,530 f/min
(12.9 m/sec)
9 min 25 sec to 20,000 ft (6,100 m)
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2,995 f/min
(15.2 m/sec)
7 min to 20,000 ft (6,100 m)
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Service Ceiling
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35,400
ft (10,790 m)
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35,400
ft (10,790 m)
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37,200
ft (11,300 m)
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Range
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Unknown
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Unknown
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Unknown
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Armament
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Gunsight
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None
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GM.2
reflector
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GM.2
reflector
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Armament
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None, then eight BSA Browning 0.303
in (7.7 mm) belt-fed machine guns
in wings (300 rpg).
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Four, then eight BSA Browning 0.303
in (7.7 mm) belt-fed machine guns
in wings (300 rpg).
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Eight BSA Browning 0.303 in (7.7
mm) belt-fed machine guns in wings (300 rpg).
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