Supermarine Spitfire Mk IX

The Spitfire Mk IX was originally developed as a stopgap measure as a response to the appearance of the Focke-Wulf FW 190A. The first response to this threat was the Mk VIII, but this aircraft involved a significant redesign of the basic Spitfire, and would take time to produce in the numbers required.

The Mk IX provided an alternative solution to the problem. It used the same Merlin 60/70 series engines at the Mk VIII, but in a slightly modified Mark Vc fuselage. This allowed for rapid development and production of the new model. Work on fitting the more power Merlin 61 with its two-stage supercharger had begun in the summer of 1941, and on 27 September Spitfire N3297 (the only Mk III Spitfire built) flew for the first time (the same month as the FW 190 became operational). Three marks of Spitfire would be developed from this experimental aircraft. The Mk VII and Mk VIII would use a redesigned fuselage, and this meant that they would take too long to produce. The crisis was so serious that the RAF was forced to stop all but the most important daytime operations over occupied Europe in November 1941. When operations were resumed again, between March and June 1942, losses were unacceptably heavy, and had to be stopped again.

Supermarine Spitfire F.Mk IX of No.602 Squadron
Supermarine Spitfire F.Mk IX of No.602 Squadron

Work began with great urgency on an interim Spitfire. The aim was to fit the Merlin 61 engine to a Mk V fuselage while making as few changes as possible. The first test aircraft flew on 26 February 1942. It was so successful that it was ordered into full production. Progress was rapid, and full production began in June 1942. It entered service the next month with No.64 squadron at Hornchurch.

The Mk IX was a significant improvement on the Mk V. It had a top speed of 409 mph at 28,000 feet, an increase of 40 miles per hour. Its service ceiling rose from 36,200 feet to 43,000 feet. It could climb at 4,000 feet per minute. In July 1942 an early Mk IX was flown against a captured Fw 190A, and the two aircraft were discovered to have very similar capabilities. The RAF had its answer to the Fw 190 problem. When the Mk VIII appeared later in 1942, its performance was very similar to that of the Mk IX.

There were three main versions of the Mk IX. The standard F.IX used the Merlin 61, and was the only version produced until early 1943 1,255 F.Mk IXs were produced. It was then joined by a version powered by the Merlin 66. This engine produced its best performance at slightly lower altitudes than the Merlin 61. Spitfires equipped with this engine were designated LF Mk IX. This was the most numerous version of the Mk IX, with 4,010 produced. Finally, 410 high altitude HF.Mk IXs were produced using the Merlin 70 engine, with an improved performance at high altitude.

Spitfire F.Mk IX side view
Spitfire F.Mk IX side view

The majority of Mk IXs of all types used the standard “c” wing, which could carry four 20mm cannon or two 20mm cannon and four .303in machine guns. From 1944 some were built with the “e” wing, which replaced the four .303in machine guns with two .50in heavy machine guns.

The Mk IX (and very similar Mk XVI) was produced in greater numbers than any other type of Spitfire. 284 were converted from older versions, 557 built by Supermarine around Southampton, and another 5117 at Castle Bromwich. With the 1053 Mk XVIs (the same aircraft with a Packard Merlin engine) that amounts to a total of 7,011 aircraft.

Plans of Spitfire Mk.IX
Plans of Spitfire Mk.IX

Spitfire IX at low level
Spitfire IX at low level

The Mk IX replaced the Mk V from June 1942. It allowed the RAF to go back onto the offensive in occupied Europe, and resume the “circus”, “ramrod” and “rodeo” raids. Its first combat success came on 30 July 1942, when an Spitfire Mk IX shot down a Fw 190. Amongst other notable achievements, the Mk IX took part in the highest altitude combat of the Second World War, when it intercepted a Ju 86R at 43,000 feet over Southampton on 12 September 1942. On 5 October 1944 Spitfire Mk IXs of 401 Squadron were the first allied aircraft to shoot down an Me 262 Jet. The Mk IX remained in service until the end of the war, even after the appearance of the Griffon powered Mk XIV.


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

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How to cite this article: Rickard, J (12 March 2007), Supermarine Spitfire Mk IX,

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