BEA returned to Hawker-Siddeley and instead chose a stretched version of the basic Trident, the HS.121 or Trident 3. The 3 included a fuselage stretch of 5 m for up to 180 passengers, raised the gross weight to 143,000 lb (65,000 kg), and made modifications to the wings to increase its chord. However the engines remained the same, and BEA rejected the design as being unable to get off the ground in hot-and-high conditions, given that the 2E was having so many problems already. Since the Spey 512 was the last of the Spey line extra power would be difficult to add. Instead of attempting to fit a new engine, which would be difficult given that one was buried in the tail, Hawker-Siddeley decided to add a fourth engine in the tail, the tiny RB.162 turbojet, fed from the same intake as the middle Spey. The engine added 15% more thrust for takeoff, while adding only 5% more weight, and would only be used when needed. BEA accepted this somewhat odd mixture as the Trident 3B. BEA ordered 26, the first flight was on December 11th, 1969, entering service on April 1st, 1971. A simple change resulted in the Super Trident 3B, two of which were sold to CAAC.
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