The Giant Flying Cranes: Hughes XH-17 And Hughes XH-28.
The American company Hughes Aircraft first took to the air an experimental helicopter XH-17 Flying Crane in October 23, 1952. On the basis of this experimental machine was created a full transport helicopter XH-28.
The XH-28 capacity was raised to 18-20 tones. The calculations showed that such characteristics are real, but this project would be very complicated.
The Hughes Company, together with the relevant scientific organizations have conducted studies and found the optimal design of the rotor. The rotor blades used titanium for an extra strength.
In parallel with the research, the company "Hughes" led the design work of XH-28. In mid-1952 construction began on a full-size prototype of the advanced helicopter.
From the point of view of the scheme and the overall architecture of the future XH-28 was similar to the existing XH-17.
XH-28 powerplant was two jet engines. This time the engines are placed inside the fuselage. Engine torque through the gearbox is transferred to a separate compressor. It took the atmospheric air and under pressure it was served in a piping of the rotor hub. Also the gearbox had a withdrawal power for the tail rotor.
In size XH-28 almost identical to the previous XH-17. Maximum take-off weight reached 47.6 tones. The calculated payload was 22.7 tones – almost half of the max weight. The helicopter could fly at speeds up to 140-150km/h at a distance of 150-170kms.
For the transportation of cargo there was the platform placed between the chassis. Due to the unique design, the helicopter could carry a heavy transport such as armored vehicles, artillery, etc.
The work on the project, the XH-28 was in accordance with the schedule until the end of 1952. But in December the Air Force has taken a fundamental decision to focus on the future tactical aircraft. Further stages of the project were cancelled.
By this time Hughes Aircraft company only managed to build a full-sized model of advanced XH-28. Soon this product was dismantled as unnecessary.
Experienced XH-17 was more fortunate. The flights continued until 1955, when the rotor is worn out. After this test was stopped, and the helicopter was scrapped.