Sukhoi T6

A predecessor to the Su-24 "Fencer", it had a cranked-delta wing and had four Kolesov RD-36-35 liftjets installed in a bay behind the cockpit to achieve STOL capability. However, tests confirmed that the short-field performance was achieved at the cost of significant loss of flight distance as the lift engines occupied space normally reserved for fuel, loss of under-fuselage hardpoints, and instability during transition from STOL to conventional flight. So the lift-engine approach was abandoned in favor to the variable-geometry wings

credit : war machines