Alekseyev I - 21 The Alekseyev I - 21 was a twin - engine d , single - seat , jet fighter , designed and produced in the USSR from 1945 to 1948 . Development . After working as Lavochkin ' s right hand man during World War II , Semyon Alekseyev was appointed as Chief Designer of OKB - 21 at Gor ' kiy . The Council of the People ' s Commissars directed Alekseyev ( among others ) to develop jet fighters using more powerful engines than the captured German examples and their Soviet - built copies . The result of Alekseyev ' s efforts was the I - 21 ( " istrebitel " , fighter ) , which was planned to be produced in several variants . The I - 21 was a twin - engined all metal single seat jet fighter , with straight wings , mid - set on a round streamlined fuselage , and engines mounted in front of the wings at about one third span . The slightly swept tail unit was cruciform in layout with the tailplane set at approximately half - fin span with slight dihedral . The aircraft ' s structure was constructed from high strength B - 95 aluminium alloy , high strength steel for highly loaded parts and " Elektron " magnesium alloy for cast fittings . A hydraulically retractable tricycle undercarriage was fitted , using twin wheels for nose and main undercarriages . Hydraullically actuated airbrakes were fitted either side of the rear fuselage . Construction of the first two airframes began at the end of 1946 , with extreme pressure from the Ministry of Aircraft Production to complete Initial flight testing by 1 August 1947 , to enable the aircraft to take part in the Aviation Day Flypast at Tushino on 18 August 1947 . While one of the two airframes initially produced was used for static testing , the other was completed as the I - 211 ( I - 21 version 1 ) with Lyul ' ka TR - 1 turbojet engines . ( The Lyul ' ka TR - 2 was the intended powerplant , but was not available ) . Despite pressure from above , the I - 211 was unable to participate in the Tushino display . Flight testing started in the Autumn of 1947 , but only six test flights had been carried out before the I - 211 struck a pothole on landing , which collapsed the undercarriage . Repairs were carried out and the opprtunity taken to replace the troublesome TR - 1 engines with Rolls - Royce Derwent V engines . The result was the I - 215 which had been in development before the first flight of the I - 211 . Other minor modifications were carried out , the most noticeable being the larger engine nacelles . Despite good results from flight testing the I - 215 lost out in production orders to the newer generation of swept winged fighters . A third I - 21 was built as the I - 215D ( " dooblyor " , second prototype ) , with a bicycle undercarriage , using wider - diameter paired wheels in a bicycle arrangement , retracting into the fuselage , along with small outrigger wheels under the engine nacelles which retracted into fairings . to order from OKB - 1 . This was used to test this arrangement for " Aircraft 150 " and other projects ( OKB - 1 was supervised by Dr . Brunolf Baade , who later designed the VEB type 152 airliner , in the DDR , as a direct descendent of " Aircraft 150 " , and indirectly of the I - 215D ) . The main undercarriage of the I - 215D also incorporated a kneeling feature which could increase the incidence of the aircraft by 3 to assist take - off . Trials with this undercarriage arrangement proved successful and paved the way for its use in many other Soviet aircraft . Armament of the I - 211 comprised two , three , four , or six cannon in the chin , depending on variant . < / div >