 In the 1970s, Pavel Sukhoy asked Arkhip Lyul'ka to design a new engine with unorthodox characteristics for installation on the projected Su-27.The challenge was taken up, and although Pavel Sukhoy died in 1974, his work was carried on by his successors and colleagues, including Lyulka.The primary difficulty in designing this aircraft appeared to be in the engines, which had to be constantly redesigned and upgraded.