The Morane-Saulnier Mörkö was the designation given to M.S.406s and M.S.410s in Finnish service after they had been given the Klimov M-105P engine.
The Finns received thirty M.S.406s during the Winter War of 1939-40 and the aircraft performed well against Soviet aircraft. Anther twenty seven aircraft, a mix of M.S.406s and M.S.410s, were purchased from Germany in 1941 and thirty more M.S.406s came from Vichy France in 1942.
By that date the Finns were fighting alongside the Germans in the Soviet Union (the Continuation War), and the M.S.406 was showing its age. The Finns decided to try and upgrade the existing aircraft. A large number of Klimov M-105P engines had fallen into their (or German) hands, and this engine was installed in an M.S.406, matching it with the VISh-61P propeller. The M-105P was a 1,100hp development of the Hispano-Suiza 12Y engine used in the M.S.406 and was thus the same size as the engine it was replacing but the extra power significantly improved the performance of the M.S.406. Its top speed rose from 302mph to 326mph, the service ceiling rose from 30,900ft to 39,370ft and the rate of climb increased.
The new aircraft was known as the Mörkö Moraani, variously translated as the 'ghost', 'bogey' or 'ogre' Morane (bugbear or bogeyman appears to be closest in meaning).
The first aircraft to be converted made its maiden flight on 4 February 1943. As well as the new engine it had the oil cooler of the Bf 109G and a 20mm MG 151 cannon in the engine. After successful trials the Finns decided to bring all of their M.S.406s and 410s up to the new standard, but only two more aircraft had been completed before the Finns agreed an armistice with the Soviets. The conversion programme continued and eventually 41 Mörkös were produced. Some were armed with the 20mm MG 151 cannon and others with captured Soviet 12.77mm machine guns. The wing armament also varied - two machine guns in aircraft based on the M.S.406 and four in those based on the M.S.410.
The Mörkö remained in front line service until 11 September 1948. They were then placed in store before being scrapped in 1952.
Engine: Klimov M-105P
Wing span: as MS405
Length: as MS405
Height: 27ft 6in
Empty Weight: 4,643lb
Loaded Weight: 6,280lb
Max Speed: 326mph at 13,125ft
Armament: Two or four 7.5mm machine guns and either one 20mm cannon or one 12.7mm Berezine UB machine gun