In the beginning of september I went on a little vacation which also took me to Friedrichshafen on the Lake Constance. Friedrichshafen has gathered quite some fame for being the birth place to the legendary Zeppelin lighter-then-air airship. But Friedrichshafen was also the birth place of the company Dornier. It was founded by Clause Dornier who started out as an engineer working for Ferdinand Graf von Zeppelin. His ingenuity soon led to his promotion to leading his own department ("Department Do") within the Zeppelin company where he was responsible for developing heavier-then-air airplanes. During those times he was responsible for the creation of many of the flying boats many people associate with the name Dornier (such as the 12 engine plane Do X). However, the companys spirit of innovation went beyond flying boats. One of said innovative creations is the Dornier Do 31, the only transport jet airplane amongst all aircrafts with VTOL (Vertical Take Off and Landing) capabilities. And one of those beauties (only three were built in total) is located in front of the Dornier Museum in Friedrichshafen.
The Do31 needs a crew of 2 persons and has a transport capacity of up to 36 soldiers. The length of the plane is 20.53 m with a wingspan of 18 m. The plane has a loaded weight of 22453 kg and carry a payload of up to 3600 kg.
The cruise speed of the Do31 is 650 km/h but it can go as fast as 730 km/h. With maximum payload onboard the plane has a range of 1800 km and can climb to up to 10700 m.
Bristol-Siddely developed the Pegasus 5-2 as main engine for the Do31 which is basically a vectored-thrust turbofan engine where the resulting stream can be directed downwards via four rotable outlet nozzles. Interesting side note: Those engines were lated used for the Harrier VTOL figher jet.
However, those engines were not enough to lift the heavy plane. They were supported by a total of eight Rolls-Royce RB162 lifting engines with four of them being mounted in a casked at the end of the wing on each side.
When the Do31 wanted to perform a vertical take off (or landing) manoveur the rotatable outlet nozzles were rotated in dowards position and the lifting engines in both wing-end caskets were started (also the air inlet and stream outlet had to be opened - on all pictures those hatches are closed).
A sophisticated flight controller was developed to support the pilots in the hovering flight mode and while transitioning from hovering to normal flight.
The maiden flight took place on February 10th, 1967. Back then there were no powerful digital processors or computers available like we have now to our disposal. In order to be able to deal with the complex mathematical problems related to an VTOL aircraft design Dornier developed the hybrid computer Do-960 which consists of digital and analog circuitry.
Unfortunately the project was cancelled in 1970 for various reasons. One of those factors was that the lifting caskets produced a huge drag and added quite some weight to the airplane. This in turn led to a reduced payload and range in comparison to an conventional aircraft.
Last but not least: Some videos to feast your eyes upon 🙂