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VL Pyorremyrsky (Whirlwind) Fighter Prototype


The VL Pyorremyrsky became a rare wartime Finnish aircraft development - only one flyable form was completed before the end.

 Updated: 7/15/2015; Authored By Staff Writer; Content ¬©www.MilitaryFactory.com

The nation of Finland went to war twice with the Soviet Union during World War 2 (1939-1945). The first war came to be known as the "Winter War" and spanned from November 1939 into March of 1940 ending with the Moscow Peace Treaty favorable to the Soviets. From June of 1941 until September 1944, the pair went to war again, this time during the "Continuation War" which saw the Finns now aided by the Germans. It was during this period that Finnish authorities invested in a locally-designed, developed and produced fighter which came to be known as the VL Pyorremyrsky (or "Whirlwind" / "Hurricane").

The original plan was to devise a fighter type that would make heavy use of locally-available materials, particularly wood. As such, precious metals would only be used where absolutely necessary. By this time, the Finns were also flying German Messerschmitt Bf 109 fighters and gained considerable operational experience with a high-performance and modern monoplane fighter.

Finnish engineers developed a single-spar wing unit made of wood running through the fuselage. A steel tube frame made up the critical understructure of the aircraft while a plywood skinning technique was employed externally for a smooth, contoured finish. The resulting design was as sleek as any modern fighter of the period. The framed canopy marked the cockpit's position at midships with a raised dorsal spine running aft of the pilot to the base of the tail fin. The tail unit was conventional with a single vertical element featured along with low-set horizontal planes. Plywood was also used to cover the aft section which utilized a monocoque frame. The wing mainplanes were straight appendages and fitted forward of midships. A conventional "tail-dragger" undercarriage arrangement was used - though thought was put into widening the track of the main legs to remedy the shortcoming of the original German Bf 109 design. Ground running was therefore improved as was take off and landing actions. The available German Daimler-Benz DB 605AC 12-cylinder, liquid-cooled, inverted-Vee, inline piston engine of 1,475 horsepower was selected to power the airframe.




Proposed armament mimicked some of what was already seen in the German Bf 109 - a hub-mounted 20mm MG 151 series autocannon and a pair of wing-mounted 12.7mm LKK/42 series machine guns. Additionally, plans were laid for a pair of underwing hardpoints supporting 440lb conventional drop bombs.

On November 26th, 1942, the Finnish Air Force commissioned for a pair of prototypes to be constructed but commitments elsewhere in the war meant that the Whirlwind was forced to undergo a long gestation period. Its construction was painstakingly slow by wartime standards particularly when compared to development speeds witnessed in Britain, Germany and the United States. Authorities had targeted May 1944 for the prototype's initial availability but this was not meant to be. Everything changed when the armistice was signed with the Soviets on September 4th, 1944 and one of the ordered prototypes was cancelled and construction of the other was all but stalled. In January of 1945, work on the aircraft resumed which saw the DB 605 engine finally fitted. The war in Europe then ended in May of 1945.

The Whirlwind was able to achieve a first flight in the immediate post-war period when it took to the air on November 21st, 1945. The aircraft proved sound at the controls, highly maneuverable and a good climber but its maiden flight was marred by a panel coming loose from the nose forcing the test pilot to land his now-smoking aircraft. Some 34 test flights then followed and these covered some 30 hours of flight time. However there proved little need for the indigenous fighter and funding became limited while the glut of available post-war Bf 109s only served to doom the program in full. The Whirlwind did remain something of a design triumph for Finland but the aircraft came along much too slow and too late to be of much use in the war effort. The Whirlwind could very well have matched Soviet fighters toe-to-toe would it have been given more time and attention to finally come of age.

The prototype completed its last flight on July 22nd, 1947 and was terminated thereafter. The sole prototype has been preserved at the Aviation Museum of Central Finland (Tikkakoski). Performance specifications included a maximum speed of 385 miles per hour, a service ceiling of 37,000 feet and a rate-of-climb of 3,640 feet per minute. The prototype was never fitted with its proposed armament.



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VL Pyorremyrsky (Whirlwind) Technical Specifications



Service Year: 1945
Type: Fighter Prototype
National Origin: Finland
Manufacturer(s): Valtion Lentokoneteehdas (VL) - Finland
Production Total: 1


Structural (Crew Space, Dimensions and Weights)



Operating Crew (Typical): 1
Overall Length: 30.02 feet (9.15 meters)
Overall Width: 34.12 feet (10.40 meters)
Overall Height: 12.80 feet (3.90 meters)

Weight (Empty): 5,776 lb (2,620 kg)
Weight (MTOW): 7,297 lb (3,310 kg)

Installed Power and Standard Day Performance



Propulsion: 1 x Daimler-Benz DB 605AC 12-cylinder, liquid-cooled, inverted-Vee inline piston engine developing 1,475 horsepower.

Maximum Speed: 385 mph (620 kph; 335 knots)
Maximum Range: 513 miles (825 km)
Service Ceiling: 36,909 feet (11,250 meters; 6.99 miles)
Rate-of-Climb: 3,640 feet-per-minute (1,109 m/min)

Armament / Mission Payload



PROPOSED (Never Fitted):
1 x 20mm MG 151 cannon firing through the propeller hub
2 x 12.7mm heavy machine guns in wings.

OPTIONAL:
2 x 440lb conventional drop bombs underwing (one per wing).

Global Operators / Customers



Finland (cancelled)

Model Variants (Including Prototypes)



"Pyorremyrsky" - Base Project name
PM-1 - Prototype Designation; one completed and flown in testing.