The VISh-23Ye propeller was delayed, and early test runs were conducted using a different propeller with manual pitch control (VISh-3Ye). Consequently, the engine was prone to overheating, and to compensate for this the cowling flaps restricting airflow around the engine were removed. Despite these problems, and the fact that the prototype had not completed all ground tests, the authorities were demanding a test flight as soon as possible.
Polikarpov himself objected to flying the prototype before it would be ready, around February 1939, but he could not stop it. The series of events which took place on 15 December 1938, while not entirely clear, are tragic. Neither Polikarpov nor Tomashevich approved the initial flight, and no one had signed the form releasing the prototype from the factory. The famous Soviet test pilot
Valery Chkalov took off and made a low-altitude circuit around the airfield. For the second circuit, Chkalov flew farther away, climbing to over 2,000 m (6,560 ft), even though the flight plan specifically forbade exceeding 600 m (1,970 ft). Chkalov apparently miscalculated his landing approach and came in short of the airfield but, when he attempted to correct, the engine stalled. The pilot was able to avoid several buildings but crashed into a power line. Chkalov was thrown from the cockpit, badly injured, and died two hours later. The official government investigation concluded that the engine stalled because it became too cold in the absence of the cowl flaps. Others hypothesized that Chkalov rapidly advanced the throttle and flooded the engine. As the result of the crash, Tomashevich and several other officials, including Arms Industry Department director S. Belyakin, who urged the first flight, were immediately arrested. Years later, fellow test pilot
M.M. Gromov blamed the designers for flawed engine cooling and Chkalov himself for deviating from the flight plan. Chkalov's son also claimed that a plot to assassinate his father had been brewing in the months preceding his death, but the circumstances of the crash make foul play unlikely. Regardless, with Chkalov's death Polikarpov's reputation with
Joseph Stalin suffered a blow from which he would never recover. Nevertheless, work on the I-180 continued. The second prototype
I-180-2 with a bigger wingspan of 10.09 m (33 ft 1 in) and M-87A engine flew on 27 April 1939, It was armed with two 12.7 mm
Berezin BS and two 7.62 mm
ShKAS machine guns on a common gunbed over the engine. Finally in April 1940, three aircraft designated
I-180S were completed, these being similar to the I-180-3, but reverting to an open cockpit and the I-16 type wing structure. Their test flights were favorable. The new fighter resembled I-16 in agility but was more stable. Top speed was 575 km/h (357 mph). Major criticisms included the open canopy and poor build quality. It was believed that fixing these defects would raise the top speed to 600 km/h (373 mph). However, the I-180-3 prototype crashed on 6 July 1940, when it entered an inverted spin due to pilot error. Especially after Chkalov's death, the Soviet authorities started to promote young designers, in preference to Polikarpov, despite the fact that the I-180 was the best performing Soviet fighter at the time of its cancellation and that it was faster than the Bf 109. One prototype series I-180 developed a speed of 585 km/h that could be improved after projected changes, such as adding a closed canopy. The next best fighter, Yakovlev's
I-26 (
Yak-1 prototype), suffered from a troublesome and protracted development cycle, but
Alexander Sergeyevich Yakovlev was one of Stalin's favorites, which most probably saved his design. In addition, the I-180 could have been available much earlier than the Yak-1 and LaGG-3 types, and producing it with a temporary M-87 engine, until the M-88 could be improved, was a possibility. Crashes of I-180 prototypes were mostly accidental, and should not be regarded as disqualifying the design. Moreover, the I-180 showed much fewer "teething problems" than its counterparts, especially the Yak-1, confirming Polikarpov's competence in aircraft design. Another advantage was that the construction of the I-180 was similar to the I-16, which was familiar to the Soviet industry and pilots, but handling of the I-180 was even easier and it was more stable. The same situation recurred with Polikarpov's next design, the advanced
I-185, based on the I-180 design. ==Operators==