Polikarpov I-180

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The Polikarpov I-180 (Russian: И-180) was a 1938 Soviet fighter aircraft prototype. It was the last attempt to extract performance from the basic Polikarpov I-16 design. The development cycle was plagued with problems and death of the Soviet hero pilot Valery Chkalov in one of the prototypes effectively ended Nikolai Nikolaevich Polikarpov's career as an aircraft designer.

1 Development
- 1.1 Technical description
2 Specifications (I-180S)
3 References
4 External links
5 Related content

[edit] Development

The I-180 represents further development of the basic Polikarpov I-16 design in order to take advantage of the more powerful two-row radial engines. The new fighter was to be powered by an 820 kW (1,100 hp) M-88 engine, a development of the license-built Gnome-Rhone Mistral Major 14K (known as M-85 in USSR), and represented the next step in evolution from the 1937 I-165-11 prototype. Proposed armament consisted of four 7.62 mm ShKAS machineguns and 200 kg (440 lb) of bombs. D.L. Tomashevich was assigned as the lead designer. The ill-fated development of the I-180 started early on. The only version of M-88 available at the time used reduction gear requiring a very large propeller at least 3.2 m (10 ft 6 in) in diameter -- massive for an airplane 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 M-88R 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 constant-speed propeller was delayed and early test runs were done with a different propeller with manual pitch control. As the result, the engine was prone to overheating and to deal with this the cowing flaps restricting airflow around the engine were removed. Despite these problems, the authorities were demanding a test flight. The series of events which took place on December 15, 1938, is not entirely clear but tragic. Neither Polikarpov nor Tomashevich approved the first 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 lap around the airfield. For the second lap, 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 powerline. Chkalov was ejected from the cockpit and died from sustained injuries 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 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 plan to assassinate his father had been in the works 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 Stalin suffered a blow from which he would never recover.

Nevertheless, work on 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 April 19, 1939, and participated in the May Day parade a few weeks later. The prototype demonstrated a top speed of 540 km/h (335 mph) and was recommended for mass production with the M-88 engine. Then, on September 5, 1939, I-180-2 piloted by T.P. Suzi crashed during high-altitude testing, killing the pilot. Again, the exact circumstances of the crash were unclear. According to eyewitnesses, the aircraft steeply dove (others claimed it fell in a spin) to 3,000 m (9,840 ft) where it leveled out, then entered a spin again leveling out once more at 300 m (985 ft). The pilot then abandoned the aicraft but did not use his parachute. No definite explanation was ever given but hypotheses include blinding of the pilot by oil from a leaking oil cooler, a heart attack, or loss of consciousness due to failure of oxygen equipment.

Preparations were carried out in 1940 to produce the first batch of 10 aircraft at the factory No.21 in Gorki. However, manufacturing was extremely slow with the first 10 aircraft taking more than 8 months. One of the reasons for this was that the local OKB lead by M.M. Pashinin was designing their own I-16 -based fighter Pashinin I-21 and factory management had devoted all of their resources to the hometown favorite, with only six brand-new engineers assigned to production of I-180. While this was being investigated, the third prototype I-180-3 with M-88 engine was completed, flying on February 10, 1940. It was armed with two 12.7 mm Berezin BS and two 7.62 mm ShKAS machine guns. There was also a proposal for I-180Sh with improved main landing gear. Test flights of the first three production I-180S 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). One of the production aircraft crashed on July 6, 1940, when it entered an inverted spin due to pilot error. The pilot was able to safely bail out. In preparation for production, Polikarpov produced the definitive I-180-5 with several modifications and M-88A engine without reduction gear. The aircraft could also accept the new M-89 engine with 1,007 kW (1,350 hp) (up to 1,165 kW (1,560 hp) with fuel injection) which would raise its top speed to over 650 km/h (404 mph).

Then, near the end of 1940, Polikarpov was suddenly informed that I-180 was being cancelled. The reason for this was a misconception that radial engines in NACA cowlings were poorly suited for aircraft with top speeds of over 500 km/h (310 mph) due to high drag. Former government officials later admitted that the fascination with liquid-cooled engines stemmed in part from attempts to imitate the then-state-of-the-art Messerschmitt Me 109. Stalin's dislike for Polikarpov after Chkalov's death likely also played a role. I-180 was the best-performing Soviet fighter at the time of its cancellation and it was faster than the Me 109. The next best fighter, Yakovlev's I-26 (Yak-1 prototype), suffered from a troublesome and protracted development cycle, but Yakovlev was one of Stalin's favorites which may have saved his design.

[edit] Technical description

I-180 was a single-engine, low-wing monoplane fighter aircraft of mixed construction with a duraluminum frame covered in plywood and fabric. Pilot sat near the tailfin in an open cockpit with a windshield similar to I-16. Landing gear was retracted pneumatically with a retractable tail wheel.

[edit] Specifications (I-180S)

[edit] General characteristics

Crew: One
Length: 7.0 m (23 ft 0 in)
Wingspan: 10.09 m (33 ft 1 in)
Height: 2.45 m (8 ft 0 in)
Wing area: 16.11 m² (173.34 ft²)
Empty weight: 1,815 kg (3,993 lb)
Loaded weight: 2,429 kg (5,344 lb)
Maximum gross takeoff weight: 2,650 kg (5,830 lb)
Powerplant: 1x M-88R, 820 kW (1,100 hp)

[edit] Performance

Maximum speed: 585 km/h (363 mph) at altitude
Range: 900 km (560 mi)
Service ceiling: 11,000 m (36,080 ft)
Maximum rate of climb: 16.7 m/s (3,280 ft/min)
Wing loading: 151 kg/m² (31 lb/ft²)
Power/mass: 0.34 kW/kg (0.21 hp/lb)

[edit] Armament

2x 12.7 mm Berezin BS machine guns; 2x 7.62 mm ShKAS machine guns; 200 kg (440 lb) of bombs

[edit] References

Kopenhagen, W (ed.) (1987) Das groβe Flugzeug-Typenbuch. Transpress. ISBN 3-344-00162-0
Маслов, М. И-180 / И-185 (Maslov, M. I-180 / I-185). ISBN 5-93848-003-7
Гугля, Ю.А., Иванов, В.П. Роковой И-180 (Guglya, Yu.A., Ivanov, V.P. The fatal I-180)