Sukhoi T-3
The Sukhoi T-3 was a prototype Soviet fighter aircraft. Development. Starting in the early 1950s, the development of the T-3 proceeded in parallel with the S-1 which would eventually become the Sukhoi Su-7. While the S-1 was a conventional swept wing aircraft ("S" stood for "strelovidniy", стреловидный, swept wing), the T-3 had a delta wing with a leading edge sweep of 57° ("T" stood for "treugolniy", треугольный, delta wing). Aside from the wings, the two aircraft shared the basic design as well as the Lyulka AL-7 turbojet engine. Since the T-3 was intended to be an interceptor , it was fitted with the "Almaz" (Алмаз, Diamond) radar housed in the air intake. The prototype first flew on 26 May 1956. The T-3 was ordered into production at Factory No.153 but events overtook it when a revised specification was issued for the Interceptor fighter role. Three aircraft were completed and transported by rail to the OKB-51 factory near Moscow, where only one was to fly in as-built condition and all three prototypes were modified for various test programmes, becoming, for example, the T-39, T-49, PT-7, PT-8 and other experimental aircraft. To investigate different radar radome configurations as well  as develop radar and missile sub-systems, two of the prototypes were converted to become the PT-7 and PT-8. The PT-7 had a variable intake ramp, while the PT-8 had an extended nose with a translating centerbody. Although not proceeded with, the T-3 served as the basis for what would eventually become the Sukhoi Su-9, forming the backbone of the PVO during the 1960s.