Avia B-71

 

In May 1935 the First Czechoslovak Republic signed a non-aggression pact with the USSR, which included a mutual economic aid clause. That treaty also included that Czechoslovakia (one of the world's leading arms exporters at the time) granted license production rights for their 75mm Skoda C-5 mountain gun and 75mm Skoda R-3 anti-aircraft gun to the Soviets. In exchange, Czechoslovakia received a license to build the Tupolev SB.

In virtue of that agreement, a contract was signed between Technoexport (Soviet Union's external trade organization) and the Czechoslovak Ministry of National Defence on 15th April 1937. A total of 61 Tupolev SBs would be delivered straight from the USSR and Avia (subsidiary of Skoda) would build another 161 SBs at their Cakovice plant. The SB received the denomination of B-71 given by the Czechoslovenske Letectvo (CL - Czechoslovak Air Force) and was planned to serve both in the bomber and long-range reconnaissance roles.

The Soviet-supplied SBs were equipped with Czechoslovak-built engines, armament, radios and instruments. Those instruments were sent to Fili, Moscow, to be fitted to various airframes at GAZ 22 factory. It was estimated that the unit price for each of those SBs was set at $ 118.460 of the time, that's $ 2.519.362,55 adjusted for 2023 inflation. 

The Avia B-71 was powered by two Hispano-Suiza H.S.12 Ydrs engines, yielding 860 hp of power each and built under license by CKD-Praha. The original four 7,62mm ShKAS machine guns were replaced by three Czechoslovak 7,92mm ZB vz30 machine guns.

When compared to the SB 2M-100-A, it differed in various details. As we've just written, one vz30 machine gun was placed in the nose, instead of the origina two ShKAS. Two balance weights were added in the lower-right wing and the B-71s were equipped with radios, while the SB 2M-100As lacked any radio equipment. The B-71 had a retractable antenna fitted in the right rear fuselage. Those features were copied by the Soviets in the late-built SB 2M-100As. 

The first three Soviet-delivered machines were sent in March 1937. The first machine was assigned to the Vyzkummy a Skusební Letecky Ústav (VZLU - Research and Experimental Aviation Institute) at Prague-Letnany airport for trials on 17th April 1937. This first aircraft retained the cartridge case ejection tunnel present on every SB, but not in every subsequent B-71. The right nose step on these three initial aircraft, was mounted higher in production B-71s. The first three B-71 had front and back sights on the vz30 machine guns, however, those sights were not fitted in production aircraft.

The Soviet-built 61 B-71s were flown from Fili, Moscow to Kiev (Ukrainian SSR), where they were delivered to Czechoslovak pilots who flew the type from Kiev to Kocice (Czechoslovakia) via Romania. Once in Czechoslovak territory, the CL assigned the B-71 to their units. The first three were assigned to an operational squadron on 13th March 1938. Those B-71 intended for the bombardment role were assigned to the 5. Letecky Pluk (5.LP - Aviation Regiment) based at Brno-Turany airport and the 6.LP based at Prague. The B-71s intended for long-range reconnaissance were assigned to the 1.LP, at Prague and the 2.LP at Olomouc, Northern Moravia. 

The Germans invaded Czechoslovakia on 15th March 1939, so the B-71 was active with the CL for one year and two days, forming the Protectorate of Bohemia and Moravia. Avia had not begun license production of the B-71 yet, so every B-71 that fell into German hands was of Soviet production.

Sources:

1st Signal Squadron - Aircraft In action 194 - Tupolev SB in Action

2nd https://en.wikipedia.org/wiki/Tupolev_SB

3rd https://massimotessitori.altervista.org/sovietwarplanes/pages/sb/tapani/b-71/czech%2Bslovak/czech%2Bslovak.htm