 During testing it was discovered that the engines would not produce the required thrust, so the N-20.20 project was started.The aircraft was similar to the N-20.10, but had one conventional engine, a Rolls-Royce Avon or Armstrong Siddeley Sapphire turbojet in each wing root.The wing was a little thinner and the main landing gear came a little closer to the fuselage because now there was no need to place the engines within the wing.