The Polikarpov SPB (D), also known as the High Speed Dive Bomber (Distance), was an aircraft developed by the Soviet Union as a twin-engined dive bomber prior to the outbreak of World War II.
Although the project saw the construction of a single prototype and five pre-production aircraft, unfortunate circumstances led to the cancellation of the program.
Two of the aircraft crashed, prompting the authorities to shift their focus towards the Petlyakov Pe-2.
Before the onset of World War II, the Soviet Union embarked on the development of the Polikarpov SPB (D), a dive bomber designed to excel in high-speed and long-distance missions.
Despite the construction of a lone prototype and five pre-production aircraft, the project faced setbacks when two of the planes met with accidents.
Consequently, the decision was made to discontinue the program and redirect resources towards the Petlyakov Pe-2, an alternative aircraft that showed greater promise.
The SPB (D) exhibited striking similarities to the Polikarpov VIT-2, a dive bomber that had received recommendations for production.
However, it is important to note that the former was actually an entirely novel design.
Distinguishing itself from the VIT-2, the SPB (D) boasted a smaller size and featured a monocoque fuselage.
The conventional undercarriage’s main gears retracted towards the rear of the engine nacelles, while the tail wheel retracted into the rear fuselage.
Positioned underneath the wings were two Klimov M-105 V12 engines, each with a power output of 783 kW (1,050 hp).
The SPB (D) retained the predecessor’s notable canopy and nose glazing but underwent a reduction in armament.
The bombardier/navigator was equipped with a single 7.62 mm (0.300 in) ShKAS machine gun, while the rear gunner had access to a retractable 12.7 mm (0.50 in) Berezin UB dorsal gun and a ventral ShKAS to safeguard the aircraft’s underside.
Internally, the bomb bay had a capacity of up to 800 kg (1,764 lbs), with an additional 700 kg (1,543 lbs) of bombs capable of being carried underneath the wings.
Even prior to the SPB (D) prototype’s inaugural flight, five pre-production models had already been ordered.
This demonstrates the confidence and anticipation surrounding the aircraft.
On 18 February 1940, piloted by Boris Kudrin, the prototype successfully completed its first flight without any incidents.
However, tragedy struck on 27 April 1940 when the first prototype crashed for reasons that remain unknown.
Regrettably, this accident resulted in the loss of test pilot Pavel Golovin’s life.
In the incident that occurred on 2 June 1940, test pilot Mikhail Lipkin narrowly escaped death when his SPB (D) aircraft collided with a parked Tupolev SB during landing.
However, on 30 June, tragedy struck again as the second SPB (D) disintegrated mid-flight.
Lipkin and flight engineer Bulychov, who were assigned to test wing flutter at an astonishing diving speed of 600 km/h (373 mph), lost their lives in the crash.
Surprisingly, the aircraft disintegrated even during horizontal flight.
Initially, investigators placed the blame on Polikarpov’s deputy, Zhemchuzhin, alleging that he had failed to properly install the balance weights in the leading edges of the ailerons, resulting in uncontrollable flutter.
Subsequently, they also held Lipkin accountable, despite his unfortunate demise, for supposedly recklessly increasing the speed.
Interestingly, TsAGI engineers and airfield personnel expressed suspicions about other potential factors contributing to the accidents, but unfortunately, these suspicions were never thoroughly examined.
Following these incidents, the third prototype, under the command of Kudrin, experienced the loss of its horizontal trim tab during flight.
Although the pilot successfully managed to land the aircraft, he adamantly refused to fly any further SPB (D) prototypes.
Consequently, on 29 July 1940, the project was abruptly terminated, as the necessary tests required for a comprehensive crash examination were left unfinished.
Instead, the government opted to develop twin-engined dive bombers based on the simplified Petlyakov VI-100 platform.
This conversion, known as the Petlyakov Pe-2, assumed the roles originally intended for the ill-fated SPB (D) aircraft. Specifications Crew 5 Length 11.2 m (36 ft 9 in) Wingspan 17 m (55 ft 9 in) Wing area 42.93 m2 (462.1 sq ft) Empty weight 4,480 kg (9,877 lb) Gross weight 6,850 kg (15,102 lb) Powerplant 2 × Klimov M-105 V-12 inline engines, 783 kW (1,050 hp) each Propellers 3-bladed Performance Maximum speed 520 km/h (320 mph, 280 kn) at 4,500 metres (14,764 ft) Range 2,200 km (1,400 mi, 1,200 nmi) Service ceiling 9,000 m (30,000 ft) Armament Guns 1x 12.7 mm Berezin UB machine gun 2x 7.62 mm ShKAS machine guns Bombs Up to 1,500 kilograms (3,307 lb) (800 internal, 700 external).
