|Weights and loads|
|Wing Load (kg/m2)||171|
|Power load (kg/hp)||2.52|
|Gun Type (Position)||Ammo|
|20mm ShVAK (engine)||1*120|
|7.62mm ShKAS (engine)||2*750|
High altitude fighter-interceptor of the I-26 family. Major difference - experimental M-105PD engine, equipped with 2-stage turbocharger E-100 designed by V.A.Dollezhal (so 'D' in the engine designation). I-28 was designed specially for service with PVO forces. In addition to the Yak-5 designation, I-28 also appears in documents as 'samoliot N°28', I-28-N, I-28-V and I-26V (here 'N' stays for 'nagnetatel'/compressor, 'V' for 'vysotnyj/high altitude).
Since the I-28 was just 100kg heavier than series Yak-1, it had a sensible advantage not only high altitude interceptor, but also as a mid-altitude (2500 to 5000m) front-line fighter.
Factory trial results of the new engine were promising, with substantially higher output than standard M-105P and much higher altitude capability. It was planned to install automatic supercharger control for hydraulically-operated turbine, but reliable solution was not found in time. Here troubles of the I-28 began. Manual supercharger control placed additional stress on the pilot, distracting his attention. Since pilot could not constantly adjust the supercharger, nominal engine power was never achieved in flight.
I-28 was designed and built within 3.5 months: July 10 to October 29, 1940. Its layout was similar to the I-26, but fuselage and tail surfaces were of all-metal construction. Wooden wing was ow slightly smaller span and less rounded tips, and was fitted with wide-span automatic leading edge slats. Landing gear - identical to one of UTI-26-2 (improved design). Tailplane and elevators were same as on UTI-26-2, what provided I-28 with better handling during landing approach than I-26. Engine cradle and fuel system of the I-26 were changed to accommodate modified engine. I-28 carried RSI-3 radiostation.
Aircraft (single airframe) was assembled on October 29, 1940 and arrived to the OKB testing ground. Ground trials continued until the end of November by senior pilot P.Ya.Fedrovi, senior engineer V.V.Barsukov, mechanic M.M.Schipanov.
First flight (December 1, 1940) lasted only 20min. Engine 'behaved' - smoke, vibration, misfiring forced pilot to shot it down and go for emergency landing. Aircraft was not damaged. The cause was prosaic: tube supplying oil to the engine was ruptured.
After installation of new M-105PD I-28 was transferred to LII for engine tuning and flight evaluation. Persisting engine 'issues' stretched the tuning process well into late 1942, providing no positive outcome.