The Dornier Do-31: A Visionary but Doomed VTOL Jet Transport
Have you ever wondered what it would be like to fly in a jet airliner that can take off and land vertically, without needing a runway? Well, back in the 1960s, a German company called Dornier tried to make this dream a reality with the Dornier Do-31, an experimental VTOL (vertical take-off and landing) jet transport that was designed to carry troops and cargo to remote and improvised locations. The Do-31 was a remarkable feat of engineering, but also a complex and costly project that faced many technical and political challenges. In this blog post, we will explore the history, design, and fate of the Do-31, and why it remains the only VTOL jet transport to ever fly.
The Origins of the Do-31
The idea of a VTOL jet transport was born out of the Cold War context, when the German Air Force (Luftwaffe) was concerned about the vulnerability of its airfields to a potential attack by the Soviet Union. The Luftwaffe wanted a STOVL (short take-off and vertical landing) aircraft that could operate from short and improvised runways, such as highways, in case of a war. The Do-31 was also intended to comply with the NATO specification NBMR-4, which called for a VTOL-capable tactical support aircraft that would be operated in conjunction with the EWR VJ 101, a West German VTOL strike aircraft designed under the NATO contract of BMR-3.
Dornier, a West German aircraft manufacturer, started working on several VTOL-related concepts as early as 1959, but formalized the design of the Do-31 in 1961. Dornier received funding and support from the German Ministry of Defence, the US Air Force, and the British Ministry of Aviation, as well as technical assistance from other companies, such as Bristol Siddeley, Rolls-Royce, and Hawker Siddeley.
The Design of the Do-31
The Do-31 was a twin-engine jet transport that had a conventional fuselage, a high-mounted swept wing, a T-tail, and a tricycle landing gear. The Do-31 had a maximum speed of 750 km/h, a range of 1,800 km, and a payload of 36 troops or 6 tons of cargo. It was the largest and heaviest VTOL jet ever built, and the only VTOL jet transport to ever fly.
The Do-31 used two Bristol Siddeley Pegasus turbofans, the same engines as the British Harrier Jump Jet, which had rotatable nozzles to direct the thrust vertically or horizontally. It also had eight Rolls-Royce RB.162 lift jets in wing-tip pods, which provided extra thrust and stability for vertical take-off and landing. The lift jets could be shut off in forward flight to save fuel.
The Do-31 had a complex and sophisticated control system that used a combination of mechanical, hydraulic, and electrical components to regulate the thrust and attitude of the aircraft. The pilot had a conventional control stick and rudder pedals, as well as a throttle lever and a nozzle lever. The nozzle lever allowed the pilot to adjust the angle of the main engine nozzles from 0 to 98 degrees. The control system also had a stability augmentation system (SAS) and a transition control system (TCS) that automatically controlled the lift jets and the reaction control system (RCS) during the transition from hover to forward flight and vice versa.
The Development and Testing of the Do-31
The development and testing of the Do-31 was divided into several stages, with four different vehicles: a control system test rig, a hovering test rig, a conventional flight prototype, and a VTOL prototype. The first flight of the Do-31 took place on 10 February 1967, and the first hovering flight on 22 July 1967. The first transition from hover to forward flight was achieved on 16 December 1967.
The Do-31 set five world records for VTOL aircraft in 1969, when it flew from Munich to Paris for the Paris Air Show. It demonstrated its capabilities to the public and the officials, and attracted a lot of attention and interest. However, the project was cancelled in 1970, due to several reasons:
- The high cost and complexity of the Do-31, which required a lot of maintenance and support.
- The technical difficulties and risks of operating a VTOL jet transport, especially in adverse weather conditions and hostile environments.
- The changing strategic priorities of the German Air Force and NATO, which shifted their focus from STOVL aircraft to conventional aircraft and helicopters.
- The lack of interest and support from other NATO allies, who preferred to develop their own VTOL projects or buy the Harrier.
- The emergence of new technologies and concepts, such as tiltrotors and STOL aircraft, which offered better alternatives for VTOL transport.
The Legacy of the Do-31
The Do-31 was a visionary and ambitious project that showed the potential of VTOL jet transport for both military and civil applications. Some envisioned that VTOL airliners could operate from helipads or rooftops, bypassing the need for airports and reducing travel time and congestion. However, the Do-31 was also a victim of its own complexity and challenges, and was ultimately abandoned as a research project. The Do-31 remains a unique and impressive achievement in aviation history.
I hope you enjoyed this blog post about the Dornier Do-31. If you have any comments or questions, please feel free to share them below. Thank you for reading!
