Yak-1 variants with improved airdynamics (1942 and 1943), A.S.Yakovlev

(18k b/w) A 1943 'Standard' Yak-1, one of the last of its type. "Soviet Combat Aircraft of the Second World War" by Yefim Gordon and Dmitri Khazanov, Vol.1 p.130
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Efforts of the A.S.Yakovlev OKB aimed on the Yak-1 airdynamic refinement continued through all the production period. Normally, this work was performed on the team initiative and gradually introduced on the production lines.

But few cases really stay out of those regular efforts.

During Summer and Fall of the 1942 during Stalingrad Battle air combat situation for Soviet Army worsened: Luftwaffe put into action new Bf-109F-4 and Bf-109G-2 with more powerful engines. Those Messerschmitts had substantial advantage over series Yaks in climb and maneuverability and some in speed (specially when 3min boost system was engaged).

Following major efforts were undertaken by A.S.Yakovlev OKB:

• Installation of modified VK-105PF engine (see Yak-1 VK-105PF);
• Installation of new VK-106-1sk (see Yak-1 VK-106);
• Weight saving program (see Yak-1 light);
• Refinement of the fighter airdynamics, described here.

The GKO order was to increase aircraft speed by 20km/h: 525km/h at ground level and 590km/h at 3750m. Research centers TsAGI and LII recommended, and designers introduced following measures:

• Fuselage divided by walls into sealed sections;
• Tailwheel made retractable;
• Cowling and fairing shape improved;
• Grid protecting the water cooler removed;
• Spinner replaced by less pointed;
• Engine exhaust stacks covered by fairings;
• Exhaust stacks re-shaped to utilize exhaust reaction force;
• Cooler tunnels shape changed;
• Surface quality requirements tightened;

In October 1942 series built Yak-1 N°16-99 was flown before and after airdynamic improvements. Trials took place at LII by test-pilot V.N.Kochenuk (from Factory N°292) and engineer V.Ya.Molchanov (LII). Results were positive - performance of improved Yak matched demands of VVS.

As a part of research program influence of different factors on the aircraft speed were studied:

• Open canopy - 18...20km/h
• Unperfect sealing of the landing gear covers - 20...30km/h
• Tail wheel not retracted - 8km/h

Production lines quickly adopted required changes in construction. One year later (October-September 1943) another series built Yak-1 N°23-148 was taken through same procedure: flight test program, refinement of the plane, and another flight test. This time only minor gain was achieved in aircraft speed (~5km/h), proving that aircraft manufacturers used all reserves of the Yak-1 improvement. Technological process finally reached its perfection. Speed variation among series Yaks also was within +/-5km/h interval.

'Clean' series Yak-1 was superior to the Bf-109G-2 in all respects up to 5000m. On higher altitudes 'Messer' gained speed advantage (up to 96km/h at 7000m). This advantage was not that crucial - Yak's maneuverability and handling remained superior up to 8000m, and high altitude air combat was not typical for the East Front.

Improvements discussed here were introduced in mass production starting from 111th batch (December 1942) until the last 192th batch that rolled out in July 1944, totaling 4461 aircraft.

Predecessors	Modifications
Yak-1B	Yak-1M

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Created July 29, 2000

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