Grigorovich I-Z

History of Grigorovich I-Z

In the early 1930s, Dmitry Grigorovich and the design bureau that bears his name were tasked with developing a new single-seat monoplane fighter for the Soviet Air Force. One of the main features of its design was the installation of a new 76.2mm recoilless rifle developed by L.V.

Kurchevski, so the aircraft had to be quite strong to handle this weapon. If successful, the fighter would be one of the most powerful fighters of its kind in the world - a threat to any bomber of its time.

Work began in the mid-1930s and the program was named "Z" (Zet). Grigorovich established a working relationship with another aircraft manufacturer, Nikolai Polikarpov, and helped Polikarpov's design bureau realize the I-5 biplane fighter program. This exposure enabled Grigorovich to use the I-5's forward fuselage and engine to accelerate the development of his Z-fighter, known as the "I-Z."

A low-wing shape was used, with the single pilot sitting in the open-air cockpit above. The fuselage tapers towards the stern, a rudder and high level plane are installed. The tail-tow landing gear rolls only on the two main legs, using skids under the tail.

Power comes from a French-origin Gnome-Rhone "Jupiter VI" 9-cylinder radial piston engine (air-cooled) that produces 525 hp and drives a single twin-blade propeller in the nose. The aircraft measures 25 feet long and has a wingspan of 37.8 feet, with an empty weight of 2,600 pounds and a maximum takeoff weight of 3,635 pounds.

The proposed weapon - key to the I-Z's success - is a 2 x 76.2mm Kurchevski DRP recoilless rifle, one under each wing unit. These guns are single-shot in nature, so there is no need to install ammunition supplies in the IZ's wings or frame. Of note is the high positioning of the fins to handle the hot exhaust from these guns. Secondary armament is a 7.62mm PV-1 machine gun in the fuselage, fired synchronously by rotating propeller blades.

This weapon is intended to be used more as a targeting device than an anti-aircraft measure.

Where possible, metal construction was used throughout the I-Z, marking a shift in aircraft design philosophy that will soon see full metal types appear on a regular basis. Cloth was used to cover the machine, and steel pipes reinforced the various elements.

The first IZ prototype entered service in mid-1931, and the second prototype appeared the following year as "I-Zbis". About 22 pre-production models were introduced in 1933, except that they were powered by the local Soviet version of the Gnome-Rhone engine, the "M-22" radial engine, which produced 480 horsepower under a modified fairing assembly.

Wooden wings were also used in the metal form of earlier models.

In the air, the I-Z has a top speed of 161 mph and a range of up to 375 miles. The aircraft has a service ceiling of 23,000 feet, with lift times ranging from 14 minutes to 5,000 meters.

50 production-quality I-Z fighters were ordered, but the design was ultimately left to a lifetime of testing and research due to the aircraft's poor spin recovery characteristics and the fact that the recoilless rifle pairing had little cost benefit.

Grigorovich then transferred to another fighter with a cannon - "IP-1".

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