The Yak-1 was better than Bf 109E but inferior to Bf 109F [9] - its main opponent - in rate of climb at all altitudes. And although it could complete a circle at the same speed (20–21 seconds at 1,000 meters [10]) as a Bf 109, its lack of agility made dogfights difficult, demanding high levels of concentration. In comparison, a Bf 109, with its automatic flaps, had a lower stall speed and was more stable in sharp turns and vertical aerobatic figures.[7] A simulated combat between a Yak (with M-105PF engine) and a Bf 109F revealed that the Messerschmitt had only marginally superior manoeuvrability at 1,000 meters (3,300 ft), though the German fighter could gain substantial advantage over the Yak-1 within four or five nose-to-tail turns. At 3,000 meters (9,800 ft) the capabilities of the two fighters were nearly equal, combat essentially reduced to head-on attacks. At altitudes over 5,000 meters ( 16,400 ft) the Yak was more manoeuvrable. The engine’s nominal speed at low altitudes was lowered to 2,550 rpm and the superiority of the Bf 109F at these altitudes was reduced.[8]
Its armament was too light but to reduce weight, modifications were made both on front line and on about thirty production aircraft: the 7,62 mm ShKAS machine-guns were removed, retaining only the single ShVAK cannon. Nevertheless, those lighter aircraft were popular with experienced pilots, for whom the reduction in armament was acceptable, and combat experience in November 1942 showed a much improved kill-to-loss ratio. Also, in the autumn of 1942 the Yak-1B appeared with the more powerful M-105P engine and a single 12,7 mm UBS machine gun instead of the two ShKAS. Although this did not increase the total weight of fire by much, the UBS machine-gun was much more effective than the two 7,62 mm ShKAS. Moreover, the simple VV ring sight replaced the PBP gun-sight, because of the very poor quality of the lenses of the latter. [9] The Yak-1 had a light tail and it was easy to tip over and to hit the ground with the propeller. Often technicians had to keep the tail down and that could lead to accidents, with aircraft taking off with technicians still on the rear fuselage.[11] Nonetheless, the Yak-1 was well liked by its pilots. For Soviet pilot Nikolai G. Golodnikov, overall, in its tactical and technical characteristic, the Yak-1B was equal to the Messerschmitt Bf 109G.[12] French Normandie-Niemen squadron selected the primitive model Yak-1M (that had a cut-down fuselage to allow all-round vision) when it was formed, in March 1943.[13] Twenty-four of these aircraft were sent to the elite all-female 586 IAP whose pilots included the world's only female aces: Katya Budanova, with 11, and Lydia Litvyak (11 plus three shared). Litvyak, the most famous fighter pilot woman of all time, flew Yak-1 “Yellow 44”, with aerial mast, at first in 296.IAP and then with 73.Gv.IAP, until her death in combat, on 1 August 1943.[14] Another famous ace who flew the Yak-1 was Mikhail Baranov, who scored all his 24 victories on it,[15] including five on a day (four Bf 109s and one Ju 87, on 6 August 1942).[16] Yak-1s were also the first type operated by the 1 Pułk Lotnictwa Myśliwskiego "Warszawa" ("1st Polish Fighter Regiment 'Warsaw'").
The importance of this type in World War II is often underestimated. Soviet naming conventions obscure the fact that the Yak-1 and its successors — the Yak-7, Yak-9 and Yak-3 — are essentially the same design, comparable to the numerous Spitfire or Bf 109 variants. Were the Yaks considered as one type, the 37,000 built would constitute the most produced fighter in history.[3][4] That total would also make the Yak one of the most prolific aircraft in history, roughly equal to the best known Soviet ground attack type of World War II, the IL-2 Shturmovik. But losses were proportionally high, in fact the highest of all fighters type in service in USSR: in 1941-1945 VVS KA lost 3,336 Yak-1s; 325 in 1941, 1,301 the following year, 1,056 in 1943, 575 in 1944 and 79 in 1945.[17]