Supermarine Spitfire Mk I

Although it was only a front line fighter for eighteen months, the Spitfire I earned one of the most enduring reputations of any aircraft. Its sleek lines, graceful appearance and impressive performance combined with its role in the battle of Britain to make it a British icon. The Mk I Spitfire was in constant development during its production run. Amongst the pre-war changes the most visually obvious was the replacement of the level cockpit of the prototype with the instantly familiar curved bubble cockpit. Of perhaps more importance to the pilot, armour plating was added behind the engine and a bullet proof windscreen was fitted.

Supermarine Spitfire I of No.65 Squadron
Supermarine Spitfire I
of No.65 Squadron

From the 78th aircraft the two blade wooden propeller was replaced by a de Havilland two-speed 3-blade propeller. From the 175th aircraft the engine was changed from the 1030 hp Merlin II to the similar Merlin III, which could take either the de Havilland propeller or a more advanced Rotol propeller. These changes increased the performance of the Spitfire at different speeds, as the angle of the propeller blade could be altered to suit high or low speed situations. The maximum speed of the Mk I was reduced from 363 mph at 18,500 in early version to 353 mph at 20,000 feet after the new armour and other extra equipment was added, but the decrease would have much more significant without the new propellers. The de Havilland propeller had increased the maximum speed by 10 mph; the Rotol propeller had a huge impact on rate of climb. One change that did not work out was an attempt to install two 20mm cannon in the Spitfire I. The cannon were unreliable and prone to jam, and would not enter front line service in the Spitfire until the IIb.

Production began slowly. The first production aircraft was completed in June 1938. In August No. 19 Squadron became the first one to receive the new aircraft, when it converted from Gloster Gauntlets. By the outbreak of war on 3 September 1939, 306 Spitfires had been delivered (of which 36 had already been written off!). The RAF went into the war with only eight Spitfire squadrons.

Over the next nine months the most important battles facing the Spitfire were the battle of production and the political battle to keep them out of France. The production battle was slowly won – in all 1566 Spitfire Is were produced before the type was phased out in favour of the Mk V. At the end of the Dunkirk evacuations the RAF had 19 Spitfire squadrons. The Hurricane was still being produced quicker, and despite heavy losses in France was still more numerous during the battle of Britain.

Just as crucial was the political battle. As the battle in France developed into a crisis, the RAF came under intense pressure to sent Spitfire squadrons to France. Fortunately Air Marshal Hugh Dowding, the head of Fighter Command, was able to resist this pressure, and the Spitfires were retained for home defence.

The Spitfire I’s first major contribution to the fighting in France came over Dunkirk. Here, home based squadrons could reach the beaches, admittedly at extreme range. Their presence changed the balance of the fighting in the air. The Hurricane squadrons had suffered heavily in France, partly because of the rapid German advance, so it was over Dunkirk that the Bf 109 finally met an equal. Dunkirk stands as the Luftwaffe’s first defeat.

Worse would soon follow. At the start of the battle of Britain the Spitfire I represented just under half of Fighter Command’s available aircraft (321 out of 848 in July 1940, 372 out of 1081 on 30 August 1940). With the help of the home defence chain of radar stations, and a brilliantly designed control system, the Spitfire and the Hurricane defeated the Luftwaffe’s daytime offensive during the battle of Britain. In fairness one must remember that the Hurricane was responsible for the majority of German losses, but it was the Spitfire that captured the imagination. Even German pilots were said to suffer from “Spitfire snobbery” – at least one Hurricane pilot, when meeting with German airmen he had personally shot down, found the Luftwaffe pilot quite convinced he had been shot down by a Spitfire! The Spitfire did perform better against the Bf 109, accounting for 180 of the around 330 Bf 109s shot down by the two types of British fighters.

Head to head comparisons of fighter losses during the battle of Britain are misleading. The Spitfire and Hurricane were designed to intercept and destroy incoming bombers, and at that they excelled. On any given day of the battle, the bulk of German losses would be amongst the bombers. Worse for the Germans, every bomber carried several highly trained crew members, all of whom were lost, as were any fighter pilots shot down. In contrast, many of the British pilots were able to bale out of their damaged fighters and return to the action.

During the battle of Britain the Spitfire was outnumbered in British service by the Hawker Hurricane. The two aircraft had a lot in common – both used the Merlin III engine, both carried eight .303in machine guns. In theory the Hurricane had a higher service ceiling than the Spitfire I, but its performance was poor at height. The Hurricane was at its best at around 15,000 feet, the Spitfire at 18,000. This meant that the Hurricane was idea for intercepting the German bombers, who usually flew in at or below 17,000 feet, leaving the Spitfires to deal with the higher flying Bf 109s. Post war studies suggest that the two aircraft scored victories in proportion to the numbers present in the battle, suggesting that they were very well matched. Pilot accounts from both sides suggest that the Hurricane, Spitfire and Bf 109 were so close in performance for pilot skill and the element of surprise to decide most combats. The statistics support the idea that the Spitfire was better able to deal with the Bf 109. The German fighters shot down 219 Spitfires and 272 Hurricanes, reflecting the numerical dominance of the Hurricane. However, the Spitfire shot down 180 Bf 109s, the Hurricane only 153. This would suggest that the Bf 109 was superior to both British fighters. This was not the case. However, as the attacker the Germans normally had the advantage of numbers, and often of altitude. Finally, the German fighters were concentrating solely on destroying British fighters, while the British fighter’s main role was to stop the German bombers.

The Spitfire I owes at least part of its fame to the devoted loyalty of its pilots. The Spitfire was a beautiful aircraft to fly. It combined agility, manoeuvrability and speed with a generally forgiving nature. Many pilots described flying a Spitfire as like strapping on wings. In contrast the Bf 109, also loved by her pilots, may have been agile, but was also unforgiving. The Spitfire would remain a front line high performance fighter throughout the entire war, something not achieved by any other fighter of the Second World War. R. J. Mitchell’s basic design turned out to be more adaptable than anyone could have imagined when it first flew in 1936 .


Mk I

Mk V




Merlin II or Merlin III

Merlin 45, 46, 50

Merlin 61 or 63

Griffon 65 or 66


990 hp or 1,030 hp

1440 (45)
1190 (46)
1230 (50)

1560 (61)
1690 (63)

2035 at 7,000 ft (65)


36’ 10”

36’ 10”

36’ 10”

35’ 10”


29’ 11”

29’ 11”

31’ .5”

32’ 8”

Empty Weight

4,810 lb

5,065 lb

5,610 lb


Full Weight

6,200 lb

6,750 lb

7,500 lb

8,385 lb



“a”, “b”, “c”

“c” or “e”

“c” or “e”


31,900 ft


43,000 ft

43,000 ft


362 mph at 18,500 ft

369 mph at 19,500 ft

408 mph at 25,000 ft

446mph at 25,400ft (prototype)

Cruising Speed


272 mph at 5,000 ft

324 mph at 20,000 ft

362 mph at 20,000 ft

Speed at Sea Level



312 mph

357 mph

Climb rate

2,530 ft/min

4,750 ft/min

4,100 ft/ min

4,580 ft/ min

Prototypes - Mk I - Mk II - Mk III - Mk V - Mk VI - Mk VII - Mk VIII - Mk IX - Mk XII - Mk XIV - Mk XVI - Mk XVIII - Mk 21 to 24 - Photo Reconnaissance Spitfires - Spitfire Wings - Timeline

Spitfire Mark I/II Aces 1939-41, Dr Alfred Price. Slightly different to many books in the Aircraft of the Aces series, Price splits his material, concentrating on the wider picture in the first part of the book before looking at eleven of the top Spitfire aces in the last two chapters of the book [see more]
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How to cite this article: Rickard, J (12 March 2007),Supermarine Spitfire Mk I,

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