A LITTLE SPITFIRE HISTORY
In 1934, the Royal Air Force put out specification F.5/34 for a fighter with all of the design features that Reginald Mitchell had told the RAF that he could put into a fighter: it would be a monoplane instead of a biplane and would have an enclosed cockpit, retractable landing gear and eight machine guns. Mitchell had good credentials: in 1931, he had redefined the concept of “speed” with his earlier Schneider Cup Racers (406.99mph). Also, in 1934, the Rolls-Royce Corp. had promised that it would make a 1,000hp version of its new, 12-cylinder PV-12 liquid-cooled engine for this aircraft.
Based on this engine, Mitchell’s design, with eight, .30-caliber wing guns, went far beyond the requirements of the F.5/34 specification. When it was submitted to the Air Ministry in January 1935, this aircraft specification was just changed to F-.37/34 for the purpose of signing the Spitfire contract. The RAF approved a Spitfire mock-up at the Wollaston plant in March 1935.
One year later, on March 5, 1936, at Eastleigh Airport in Hampshire, chief test pilot “Mutt” Summers of the Vickers and Supermarine companies successfully flew the first Spitfire to have the PV-12 engine— by then known as the Rolls-Royce Merlin C. This engine propelled the Spitfire at 349.5mph—a 100mph increase in fighter speeds. The RAF had used the Hawker Fury, Gloster Gamecock, Bristol Bulldog, etc., since the end of WW I, but this new Spit ended the era of British biplane fighters.
DELIVERIES BEGIN
The Spitfire’s guns were first fired in anger on October 9, 1939, when they shot down two German Heinkel 111 bombers over the Firth of Forth. This was only a prelude.
Spitfire airframes incorporated two developments that greatly aided pilots. The original ailerons were fabric covered and gave a poor rate of roll at combat speeds. On the Mk. V model, they were modified: a redesigned aerodynamic balance tab and metal covering greatly reduced stick forces and gave it a superb roll rate of more than 140 degrees per second—one of the highest rolling capabilities among WW II fighters.
The Malcolm partial bubble canopy from the Mk. I Spitfire provided very good all-around visibility for five years, and then, in 1944, the
full bubble American canopies were available. The British, however, delayed their installation until just after the war’s end—probably to avoid delaying the sorely needed Spitfire deliveries.
Another Spitfire asset of which its wartime pilots were probably ignorant was its 11.5-percent-of-chord main-wing thickness; this gave the Spit a critical dive Mach number of about 0.84—a higher dive speed than any other fighter used in the war.
Most WW II fighters that had wing thicknesses of 15 to 16 percent of chord had a 0.76 top Mach number; this greatly limited their ability to enter evasive dives and often caused them instant and difficult recovery-from-compressibility (transonic) control problems. On April 27, 1944, one RAF photorecon P.R. XI did a planned, instrument-recorded, vertical dive to 0.92 Mach and returned to base without its propeller and engine gearbox. I am sure that the test pilot was pulling on his control stick—“frozen” by compressibility shock waves— with both hands when his Spitfire decelerated through 0.84 Mach and instantly reverted to full control that caused him to make an unintended excessively high-G pullout. Goodbye, prop and gearbox! I have experienced this phenomenon in a Hellcat while exiting the critical transonic compressibility zone.
The Spitfire’s major shortcomings were that it couldn’t carry heavy external stores or large external fuel tanks, and it had a short range. This limited its role as a fighter-bomber. Provisions were made for late Mk. V series Spits to carry one, centerline, 500-pound bomb or a 170-gallon drop tank. In the 5,665 Mk. IXs built, the bomb load was increased to 1,000 pounds with the addition of two wing bomb racks. At this time, American fighters carried more than 2,000 pounds of bombs. Several later Spitfire marques also carried six wing racks for five-inch HVAR rockets. This limited externally carried armament remained until the Mk. XVI model, which appeared just before the war’s end.
SPITFIRES IN THE BATTLE OF BRITAIN
Because the Spitfire’s production was started later than the Hurricane’s, only 19 squadrons of them were available for the Battle of Britain, but there were 30 squadrons of Hurricanes. Typically, the 60mph-slower Hurricanes were assigned to attack bombers, and the Spitfires were ordered to a higher altitude to take on the faster Bf 109 fighter escort. Both aircraft were thus in their best fighting arena for this historic battle.
Fortunately, the Spitfire and the Messerschmitt were similarly vulnerable to enemy aircraft shooting from the rear: the oil cooler, coolant and intercoolers that were visibly located in the wings were easy targets for attacking aircraft. When, in 1941, the Focke-Wulf 190 entered the fray with its air-cooled engine and submerged oil coolers, the balance was tipped in favor of the Luftwaffe. The Hurricane and the Luftwaffe’s Heinkel 111 bombers had the same, vulnerable, wing-located cooling systems.
THE NAVY SPITFIRE: THE SEAFIRE
At the outbreak of WW II, among Allied navies, only the Royal Navy (RN) Fleet Air Arm flew biplanes, and it did so until early 1941. The Seafire production decision was probably not taken sooner because the RAF required all the available Spitfires for the Battle of Britain and the African campaigns.
Although the British RN had 1,620 Seafires before the end of the war, it didn’t do as well on carriers as the 4,313, designed-from-the-ground-up Grumman Wildcats, Hellcats, and Vought Corsairs (delivered to Great Britain under the
U.S. Lend-Lease Act). According to RN test pilot Capt. Eric Brown, “The Seafires had very limited range for combat air patrols, and “their deck-landing accident rate resulted in more operational losses than combat successes.”
Its idiosyncrasies notwithstanding, the Spitfire earned its reputation in all of the theaters of the war and was used by many nations long after hostilities had ceased.