Hawker Siddeley HS-121 Trident 3B BEA G-AYVF (1972). Classic Trijet with actually four engines: 3 Rolls- Royce Spey 512 two-shaft turbofans and a smaller Rolls-Royce RB.162.86 booster turbojet built into the tail below the rudder
Hawker Siddeley HS-121 Trident 3B BEA: the Trident 3B was the ultimate version of the trijet. It had a fourth smaller engine built into the tail below the rudder to boost climb out and take-off performance