Modern-Aviation

VL Myrsky (English: Storm) was a Finnish World War II fighter, designed by the State Aircraft Factory (Valtion lentokonetehdas) for the Finnish Air Force. The models of the aircraft were Myrsky I, Myrsky II, and Myrsky III.

The Myrsky (storm) was the only warplane of indigenous Finnish design to enter production during the course of World War II and, like the altogether more advanced Heinkel He 162, was designed to avoid use of scarce light alloys by adoption of an airframe of mixed construction, using wood and steel which were not in short supply. However, the development and production of this fighter were very slow, and the type was basically obsolescent even as it entered service in the later part of 1944.

It was on 8 June 1939 that the Valtion Lentokonetehdas (state aircraft factory) received a contract from the Finnish Ministry of Defence to design this new single-seat fighter. The chief designer was Dipl.-Ing. Arvo Ylinen, who was assisted by Torski Verkkola (structure) and Martti Vainio (aerodynamics), but Ylinen moved to the Helsinki University of Technology in August 1940 and Edward Wegelius was then appointed as the head of the VL’s design department. Within nine months of the receipt of the definitive prototype contract on 20 December 1940, the prototype of the resulting Myrsky, later the Myrsky I, was in final assembly.

In basic concept and configuration the Myrsky was an orthodox fighter of the low-wing cantilever monoplane type with an enclosed cockpit and tailwheel landing gear that included wide-track main units which retracted inward into wells in the underside of the wing. The type was designed around the most powerful radial engine currently available to the Finns, namely the SFA STWC3-G unit that was the unlicensed Swedish copy of the Pratt & Whitney R-1830-SC3G Twin Wasp air-cooled 14-cylinder two-row unit with a nominal rating of 1,065 hp (794 kW) and driving a constant-speed propeller with three compressed-wood blades. The fuselage was of welded steel tube construction skinned over its front and rear sections with light alloy panels and plywood, and the single-piece wing was of plywood-covered wooden construction based on two box spars plywood ribs and plywood skinning. This wing was dihedralled, tapered in thickness and chord, and carried over virtually the full span of its trailing edges was the standard combination of outboard ailerons and inboard flaps; the latter of the split type. The cantilever tail unit was of similar construction to the rear fuselage, and all the control surfaces were covered with fabric.

The prototype recorded its maiden flight on 23 December 1941, but immediately encountered the first of what were to be a host of teething as well as more fundamental problems, including defective bonding of wooden components, weakness in the main landing gear units, inadequate longitudinal stability, and failures in the wing attachments. These problems demanded a complete redesign and restressing of the wing.

On 30 May 1942 the VL received a contract for three development aircraft which were to embody numerous detail structural and other changes, these including an increase in wing area of 13.99 sq ft (1.30 m²) and a change in the fixed forward-firing armament from two 0.5-in (12.7-mm) and four 0.303-in (7.7-mm) machine guns to three or four of the larger-calibre weapons in the first and second aircraft, and in the third aeroplane respectively. The first of these development aircraft was completed on 30 April 1943, but crashed only one week later, and the second suffered damage in a wheels-up landing some three months later, and then broke up in the air shortly after resuming its flight test programme. The third aeroplane was evaluated in service and, on 17 March 1944, lost both wings in a dive.

The VL had meanwhile initiated production of the first production variant, which was known as the Myrsky II. All the progressive changes that had been introduced in the prototype and development aircraft were incorporated, and the fixed forward-firing armament was standardised as four 0.5-in (12.7-mm) LKk/42 machine guns. By the end of July 1944 the VL had completed 14 Myrsky II aircraft, a further 16 having been delivered by the time of the 4 September 1944 truce which ended Finland’s ‘Continuation War’ with the USSR. Production continued after the truce, however, and the last five of the 47 aircraft were delivered straight to the Air Force Depot on 30 December 1944 without flight testing.

The Myrsky II was assigned to the TLeLv 12 tactical reconnaissance squadron, which received its first aeroplane on 23 July 1944, 20 being delivered to the squadron before the armistice, and the TLeLv 16 squadron began conversion to the Myrsky II during this period. The Myrsky II was flown operationally over Lapland against the German forces under the terms of the Finnish-Soviet armistice agreement, but the Ilmavoimat (Finnish air force) flew this fighter only to a limited extent, and the service’s doubts as to its durability and sturdiness, despite continuous reinforcement of various components, finally came to a head on 9 May 1947 when a Myrsky II broke up in a dive. All the aircraft of this type were then grounded.

Service had showed that the Myrsky II was manoeuvrable enough to dogfight contemporary Soviet aircraft, and it was the second fastest aeroplane in Finnish service after the Messerschmitt Bf 109G. Its basic aerodynamic design was excellent, and was later reused on the VL Pyörremyrsky fighter and the Valmet Vihuri trainer, and the wide track of its main landing gear units gave it good ground-handling properties on Finland’s indifferent airfields. The type’s main failing however was its construction, which could not adequately handle the harsh Finnish weather.

The Myrsky II was neither popular nor successful, and plans for an improved Myrsky III variant were terminated in 1945 when the initial 10 aircraft were already under construction.