The Polikarpov I-180 () was a 1938 Soviet fighter prototype. It was the last attempt to extract performance from the basic Polikarpov I-16 design. The development cycle was plagued with problems, especially with the death of the star Soviet test pilot Valery Chkalov in one of the prototypes. Design and development The I-180 represented a further development of the basic I-16 design in order to take advantage of the new radial engines coming into service. It was designed to meet a requirement of the Soviet Air Force of January 1938 for a new interceptor aircraft with a radial engine. It was preceded by a series of projected I-16 variants with a more powerful Tumansky M-88 two-row radial engine: I-161, I-162, I-163, I-164, I-165, I-166 and I-167. The I-180 was a single-engine, low-wing monoplane aircraft of mixed construction with a duraluminum frame covered in plywood and fabric. The pilot sat near the tailfin in an open cockpit with a windshield similar to the I-16. The landing gear was retracted pneumatically, including the tail wheel. The main visual difference between the I-180 and I-16 was a new wing with a perpendicular straight leading edge, and an aerodynamically refined fuselage with a longer slim engine cowling. The new fighter was to be powered by an 820 kW (1,100 hp) M-88 engine, a development of the license-built Gnome-Rhône Mistral Major (known as M-85 in the USSR), and represented the next step in evolution from the 1937 I-165-11 prototype. The proposed armament consisted of four 7.62 mm (0.3 in) ShKAS machine guns and 200 kg (440 lb) of bombs. Dmitriy Tomashevich was assigned as the lead designer. The ill-fated development of the I-180 started early on. The only version of the M-88 available at the time used reduction gear requiring a very large propeller, at least in diameter – massive for an aircraft that in layout and dimensions resembled an I-16 with an elongated nose. Even before leaving the drawing board, the fighter had to be redesigned for an M-88R engine with reduction gear and a constant-speed propeller. The projected top speed fell from 572 km/h (355 mph) to 557 km/h (345 mph). The first prototype, however, was eventually fitted with a similar M-87 950 hp engine, because the M-88R was not ready. The prototype was built at Number 156 Factory in Moscow. Testing and evaluation The VISh-23Ye propeller was delayed, and early test runs