Aero-engines - UDF - Part 24

UDF aircraft engines

Silnik UDF. 1984 year. Photo by NASA
Silnik UDF. 1984 year. Photo by NASA

Boeing and General Electric.

In 1981, General Electric joined the UDF program. The General Electric project surprised NASA specialists. The powertrain was bigger, stronger, and was supposed to be air-tested earlier, already in 1986. In 1983, General Electric released a mock-up of the UDF engine to the public. The engine received two counter-rotating propeller-fans, 3.60 m in diameter. Its base is the F-404 engine used as a drive for F-18 combat aircraft. The drive unit has a thrust of 1 x 111.20 kN. This engine, compared to a two-flow engine (flow ratio 6: 1), with the same thrust consumes 25-30% less fuel. It was predicted that the engine would provide a cruising speed of Ma = 0.6 - 0.8. It should be noted that the interior of the engine has two shafts. One turned to the right and the other to the left. There was no gear in the engine. The propeller blades were moved directly from the turbines.

General Electric planned to use this type of drive in the currently designed Boeing 7J7. The aim was to achieve the lowest possible cost of transporting one passenger, at least below the cost of the Boeing B.737. That's why Boeing reworked one of the Boeing B727s to include one fan-propeller engine. The plane first flew on August 20, 1986. After the first tests, the constructors' opinions were divided. Not all were UDF enthusiasts. The noise was higher than expected, but it was not an insurmountable problem.

Boeing management continued to promote the B7J7 design. In 1987, he made nearly 100 presentations, symposia and shows promoting the B7J7 aircraft. At the same time, it was decided to enlarge the plane. The offered UDF engines were too weak for him, so General Electric was commissioned to build a larger and more powerful engine.

At that time, professional and daily press published articles with the message - "In the future, the aircraft engine will have propellers".

In fact, Boeing needed a competitor to the Airbus A320, which it fled on February 22, 1987, which sold well. In addition, it began to conquer the US market. Northwest Airlines and United Airlines purchased A320 aircraft in 1987. Boeing B737-300 / -400 / -500 aircraft were not as competitive. The UDF on paper was very competitive.

Of course, everything was related to oil prices. In 1986, Saudi Arabia lowered the price per barrel, looking at declining crude oil revenues. In fact, the profitability of the new UDF engine depended on fuel prices. Suddenly, sales of Boeing B737s with CFM56 engines rose in 1987. This was because the waiting time for B737s was shorter than for A320s. In 1987, Boeing announced the postponement of the UDF program for one year. The design of the B7J7 aircraft turned into a completely different design, the B777.

Written by Karol Placha Hetman