July 28, 2011

Battle of Britain: Part IV - Legend of the Spitfire

The Spitfire captured the fascination and imagination of generations the world over. It became a legend during the Battle of Britain and was hailed as the best fighter aircraft in the RAF fleet. Although the Hurricane faced a larger proportion of enemy aircraft it was the Spitfire which had a higher ratio of victory to loss. It was the ambition of every pilot to fly it, and the dreams of every young boy to grow up and become a Spitfire pilot!

Those who flew them marveled at its wide-ranging capabilities. It was not only a fighter aircraft, but an interceptor, bomber, and dealt with photo-reconnaissance as well as training. There were numerous variants of the design which featured different wing configurations but also horse power. The Spitfire had its origins at Supermarine Aviation Works and was the brainchild of its chief designer, R.J. Mitchell. After Mitchell`s death from cancer in 1937 one of his colleagues, Joseph Smith carried on as chief designer. The original airframe, powered by a Rolls-Royce Merlin engine, produced 1,030 hp (768kW) and was easily adapted to increasingly more powerful engines, such as the Rolls-Royce Griffon engines that eventually produced 2,035 hp (1,520 kW).

The first Griffon-powered Spitfire DP 845 flown by Jeffrey Quill 1942

The most striking feature of the Spitfire was its sleek elliptical wings which had a thin cross-section allowing a higher top speed than other fighers of its time, including that of the Hawker Hurricane. The Spitfire was built for speed which allowed it to accomplish its mission so successfully against enemy aircraft.

Spitfire, the legend, the facts and its opponent (5 of 5) (00:08:17m)

However, the Spitfire had its growing pains. The British Air Ministry had set specifications for a new fighter aircraft that was capable of 251 mph (404 km/hr) and in 1931 H.J. Mitchell designed the Supermarine Type 224. It was an open cockpit monoplane with bulky gull wings and a large fixed spatted undercarriage powered by a evaporative-cooled Rolls-Royce Goshawk engine of 600 hp (450 kW). It made its virgin flight in February 1934 but without the expected fanfare. It was a big disappointment. Mitchell and his team embarked on refining its design. Among the seven variations, it was the Gloster Gladiator biplane that was accepted for service.

Gloster Gladiator Biplane
His next aircraft was not accepted by the Air Ministry either. It was the Type 300, based on Type 224 but with a retractable undercarriage and its wingspan was reduced by 6 ft (1.8m). The design went through several modifications and incorporated a faired, enclosed cockpit, oxygen-breathing apparatus, smaller and thinner wings and the newly developed and more powerful Rolls-Royce PV-XII-V-12 engine, later christened the "Merlin". Mitchell began refining its design and the final version was completed on December 1, 1934.

In response to a recommendation by Squadron Leader Ralph Sorely of the Operational Requirements section of the Air Ministry, the Spitfire's armament was changed from two .0303 in (7.7 mm) Vickers machine guns in each wing to four .303 Brownings.

A prototype K5054 took its first flight on March 5, 1936 flown by the chief test pilot for Vickers Aviation, Captain Joseph "Mutt" Summers. This flight was made just four months of the maiden flight of the Hurricane.

The K5054 was fitted with a new propeller and taken on a test flight by Summers on March 10, 1936  It was the first time that the undercarriage was retracted.  After the fourth flight, the plane was fitted with a new engine and it was test-flown by Summers' assistants, Jeffrey Quill and George Pickering.  In their assessment, the Spitfire was very good, but not quite perfect. The rudder was too sensitive at speeds of 330 mph (528 km/hr) . In May the design incorporated a new and better shaped wooden propeller, allowing the Spitfire to reach a velocity of 348 mph (557 km/h) in level flight. After Summers had flown the prototype to RAF Martlesham Heath, Ft. Lt. Humphrey Edwardes-Jones took over the prototype for the RAF. He took it on a test flight and gave it a positive report with one recommendation - that the plane be equipped with an undercarriage position indicator. In the span of a week, on June 3, 1936, the Air Ministry had placed an order for 310 Spitfires without so much as looking at an offical report. (Interim reports were later issued).

The Spitfire made its public debut on Saturday, June 27, 1936 at the RAF Hendon air-display. Mass production was supposed to begin immediately but was postponed due to numerous problems that took some time to resolve.It was not until mid-1938 that the first Spitfires (K9787) rolled off the assembly lines at the Supermarine factory at Woolston, Southampton. This delay was attributed to the fact that the production was already working at full capacity filling orders for Walrus and Stranraer flying boats (and particularly due to the reluctance of Vickers-Armstrong (the parent company) in dealing with outside contractors). Consequently, the Air Ministry decided that after the initial order of 310 Spitfires, production should be stopped and henceforth instructed Supermarine to build Bristol Beaufighters. On March 24, 1938 the management teams of Supermarine and Vickers were able to persuade the Air Ministry that the problems could be overcome and thus received orders for 200 Spitfires for the K, L and N prefix serial numbers.

The most famous fighter aircraft in the Battle of Britain were the British Hawker Hurricane and Supermarine Spitfire Mk I and the German Messerschmitt Bf 109 single-engine fighters.  The Spitfire was a more glamorous fighter, even though it was the Hurricanes that tallied the most kills, especially in the early part of the battle. The Spitfire and the Bf 109E were similar in speed and agility yet both were faster than the Hurricane. It is noteworthy that the turn-around time (the amount of time to re-arm and fuel) was 26 minutes for the Spitfire and only 9 minutes for the Hurricane. 

Spitfires in formation

Both the Hurricane and the Spitfire were armed with eight .303 Browning machine guns in the wings, which were set to allow the bullets to converge at a distance.  Although the Brownings had a high rate of fire it was incapable of penetrating the armor plating on Luftwaffe aircraft.   The incendiary round, called the "De Wilde" was chosen as it could do more damage than the standard "ball" rounds.

During battle several Hurricanes flew missions armed with a single Hispano 20mm cannon in a pod under each wing. The experiment was unsatisfactory as the operation of the Hurricane became too slow and sluggish. Several Spitfires (Mk. IBs)  were also modified to carry a Hispano cannon however it experienced problems during combat: the guns often jammed and were unable to fire. But when it did function properly it was a highly effective weapon, capable of easily piercing the armored plating and self-sealing fuel tanks of the Luftwaffe aircraft.  An enemy fighter could be brought down with just three or four hits, or at the very least it would be damaged beyond repair.

No. 315 and No. 317 Polish squadrons flew the Spitfire Mk. Vb BM597 G-MKVB
Cockpit of BM597 Spitfire
From about the mid-1940s, the Spitfire had 73 pounds (33 kg) of steel plated armour, 6.5 mm thick for head and back protection on the seat bulkhead (4.5 mm) and covered the forward face of the glycol header tank while the Messerschmitt Bf 109 E-3 had 10mm of extra armour built in behind the pilot`s head and another 8mm armoured plate in the fuselage to protect the tank and the pilot from attacks from behind.

In the mid-1930s aviation design was developing all-metal, low-wing fighter aircraft, such as the French Dewoitine D.520 and the German Messerschmitt Bf 109. The refinements featured all-metal wings, retractable undercarriages, fully enclosed cockpits and low drag. The design of the Spitfire's airframe was a complex skeleton of 19 frames beginning at the main engine bulkhead (frame number one) to the tail unit frame. Five half-frames were built aft of the engine bulkhead to accomodate the fuel tanks and cockpit.  The frames were oval from the seventh frame to the nineteenth, each slightly reduced in size and each incorporating numerous holes drilled through them in order to lessen the weight as much as possible, and not weaken the structure.  Frame 20 was U-shaped and was the last frame of the fuselage proper and the frame to which the tail unit was attached. Frames 21, 22 and 23 formed the fin; frame 22 incorporated the tailwheel opening and frame 23 was the rudder post. Before being attached to the main fuselage, the tail unit frames were held in a jig and the eight horizontal tail formers were riveted to them.  A combination of 14 longitudinal stringers and two main longerons helped form a light but rigid structure to which sheets of alclad stressed skinning were attached. The fuselage plating was 24, 20 and 18 gauge in order of thickness towards the tail, while the fin structure was completed using short longerons from frames 20 to 23, before being covered in 22 gauge plating. There was ample room for camera equipment and fuel tanks which were to be fitted during the Spitfire's operational service life.

Polish Squadron in the Battle of Britain

The skins of the fuselage, wings and tailplane were secured by rivets and in critical areas such as the wing forward of the main spar, with flush rivets, where an uninterrupted airflow was required. The fuselage used standard dome-headed riveting. From February 1943 flush riveting was used on the fuselage, affecting all Spitfire variants.  In some areas, such as the rear of the wing, the top was riveted and the bottom fixed by woodscrews into sections of spruce; later, pop-riveting would be used for these areas. At first the ailerons, elevators and rudder were fabric-covered.  However combat experience demonstratd that fabric-covered ailerons were impossible to use at high speeds therefore fabric was replaced with a light alloy, improving control throughout the speed range.

The Spitfire had detachable wing tips which were fastened by two mounting points at the end of each main wing assembly. When the Spitfire took on a role as a high altitude fighter (Marks VI and VII and some early Mk VIIIs) the standard wing tips were replaced by extended, "pointed" tips which increased the wingspan from 36 ft 10 in (11.23 m) to 40 ft 2 in (12.3 m). The other wing tip variation, used by several Spitfire variants, was the "clipped" wing; the standard wing tips were replaced by wooden fairings which reduced the span to 32 ft 6 in (9.9 m). The wing tips used spruce formers for most of the internal structure with a light alloy skin attached using brass screws.

In late 1943, high diving trials were conducted in Farnoborough to test the handling characteristics of aircraft travelling at speeds near the sound barrier. The Spitfire XI was selected for the trials as it had it highest limiting Mach number of any other aircraft.  A fully feathering Rotol propeller was fitted to prevent overspeeding - due to the high altitudes necessary for these dives.  The EN409, flown by Squadron Leader J.R. Tobin reached 606 mph (975 km/hr, Mach 0.891) in a 45 degree dive. However in another test, the same aircraft suffered engine failure when the propeller and reduction gear broke off. The Squadron Leader who flew it, Anthoy F. Martindale RAFVR, successfully glided the Spitfire for 20 miles (32 km) back to the airfield and landed safely.  Martindale was decorated with the Air Force Cross for his bravery.

The Spitfire was modified by the RAE (Royal Aerospace Establishment)for high speed testing of the stabilator (aka "flying tail"). It was tested by RAE test pilot Eric Brown, in which he successfully reached Mach 0.86 in a dive.

The view from the Spitfire cockpit was considered fair however the curved plexiglass windscreen was poorly constructed and caused severe optical distortion making long-distance visual scanning laborious. The problem was solved when optically true glass was installed. Pilots flying the Hurricane had a better view over the nose than those flying Spitfires as the former had a higher seating position.

Many of the Spitfires used in the Battle of Britain were purchased privately. Money raised by towns, companies, clubs or individuals was used to buy Spitfires for £5,000 each with the purchaser having naming rights. Queen Wilhelmina of the Netherlands donated £215,000 to purchase 43 Spitfires.

The greatest compliment paid to this aircraft was by a German ace during the Battle of Britain. In frustration he turned to his CC and demanded a squadron of Spitfires!!

Specifications (Spitfire Mk Vb)

General Characteristics 
Length: 29 ft 11 in (9.12 m)
Wingspan: 36 ft 10 in (11.23 m)
Height: 11 ft 5 in (3.86 m)
Wing area: 242.1 ft² (22.48 m²)
Airfoil: NACA 2209.4(tip)
Empty weight: 5,090 lb (2,309 kg)
Loaded weight: 6,622 lb (3,000 kg)
Max takeoff weight: 6,770 lb (3,071 kg)
Powerplant: 1 × Rolls-Royce Merlin 45 supercharged V12 engine, 1,470 hp (1,096 kW) at 9,250 ft (2,820 m)

Maximum speed: 378 mph, (330 kn, 605 km/h)
Combat radius: 410 nmi (470 mi, 760 km)
Ferry range: 991 nmi (1,140 mi, 1,840 km)
Service ceiling: 35,000 ft (11,300 m)
Rate of climb: 3,240 ft/min (13.5 m/s)
Wing loading: 27.35 lb/ft² (133.5 kg/m²)
Power/mass: 0.22 hp/lb (0.36 kW/kg)

2 × 20 mm (0.787-in) Hispano Mk II cannon, 60 rpg (drum magazine)
4 × 0.303 in (7.7 mm) Browning machine guns, 350 rpg
: 2 × 250 lb (113 kg) bombs

Spitfire MK IIa P7350
The oldest airworthy Spitfire in the world, and the
only one left that had fought in the Battle of Britain

RAF pilots scramble to Spitfires  - Battle of Britain


Sources and Suggested Links:

Allied Aircrew in the Battle of Britain (British and other nations)

Untold Battle of Britain - Interview with Witold Urbanowicz

Polish Pilots of Battle of Britain - List of Victories (in Polish)

Ace Pilots

No. 308 Polish Fighter Squadron List

Fighter Ace Pilots of WW2  (Comprehensive List)

Supermarine Spitfire Aviation History

Supermarine Spitfire - Classic Warbirds of WW2

Spitfire Performance Testing

Aviation Gallery - paintings of Spitfires


No comments:

Post a Comment