Dornier Do 31
Do 31 | |
---|---|
Dornier Do 31 in 1968 | |
Role | VTOL transport |
Manufacturer | Dornier Flugzeugwerke |
First flight | 10 February 1967 |
Status | Project cancelled in April 1970 |
Primary user | German Air Force |
Number built | 3 |
Variants | Dornier Do 231 |
The Dornier Do 31 is an experimental, jet-propelled, vertical take-off and landing (VTOL) cargo aircraft that was designed and produced by West German aircraft manufacturer Dornier.
The development of the Do 31 was motivated principally by heavy interest expressed by the
In addition to performing test flights, Dornier often demonstrated the Do 31 prototypes to officials and the general public, such as at the 1969 Paris Air Show. Several world records were set by the type during its limited flying career. When the high cost, technical and logistical difficulties of operating such an aircraft were realized, the German Air Force opted to cease trials involving VTOL aircraft, such as the Do 31, VJ101, and the later VFW VAK 191B. In the face of limited sales prospects and a lack of state support, the Do 31 and other VTOL projects lingered as research projects for a time prior to their manufacturers abandoning all activity. The Do 31 remains the only VTOL-capable jet-powered transport aircraft to ever fly.
Design and development
Background
During the late 1950s and 1960s, the
As early as 1959, West German aircraft manufacturer Dornier had been informally working on several VTOL-related concepts,[3] although it would not be until 1961 that the design team would formalise what would become the Do 31.[4] Early activity centred around a series of studies on the topic of a VTOL-capable utility transport aircraft. Dornier's design team, based at the company's facility in Friedrichshafen, was headed by the aeronautical engineer Gustav Wieland. Already at this stage, Dornier was liaising with foreign companies, including British engine manufacturer Bristol Siddeley, who were independently working on their own VTOL-orientated engine already.[3]
The design of the flight control system was considered to be a critical element of any aircraft performing vertical flight, particularly in how it handled control failures.[5] To support the development programme, a purpose-built flight control test rig was constructed by Dornier, which allowed their design team to explore and evaluate different attitude control laws and flying qualities.[6][7] To solve the differential equations necessary to model the aircraft in detail, the Dornier DO-960 hybrid computer was developed.[8] In spite of allowances to facilitate control during vertical flight, the flight control philosophy used upon the Do 31 was more akin to a conventional aircraft than that of a helicopter.[9]
Programme launch and design
During February 1962, the formal launch of the Do 31 programme occurred with the issuing of a development contract from the West German government.[3] By the start of 1964, Dornier had started building a pair of prototype aircraft; their manufacture was largely performed at the company's Oberpfaffenhofen plant.[10][11] A total of three test prototypes were constructed, these being E1, E2 and E3 - the "E" indicating Experimentell (Experimental). E1 was powered only by the Pegasus engines, having been designed to test horizontal flight. E2 was a static test airframe, and did not ever fly. E3 was furnished with both Pegasus and RB162 lift engines installed, being intended to evaluate the design's vertical flight mode.[citation needed]
The design of the Do 31 was heavily reliant upon its engine configuration. Dornier had opted to incorporate the
By mounting the engines in pods, the fuselage could accommodate a capacious hold for storing cargo, which was primarily accessed via a rear-facing loading ramp. Early designs of the Do 31 used more than four Rolls-Royce RB162s; the availability of more powerful versions of the Pegasus engine enabled the reduction to four supplemental lift engines.[13] Due to the engines being placed in nacelles, as opposed to within the fuselage as on the Harrier, the Pegasus had to be specially modified for the Do 31.[14]
Beyond providing adequate lift and control, other factors influenced the propulsion system. According to Dow, noise was a considerable concern, particularly as the airframe's critical frequency was close to that which was naturally generated by the lift engines.[15] The re-ingestion of hot exhaust gasses was another critical area, complicated by there being 16 'fountains' of gas being generated during vertical hover, 12 of which being hot. Following intense study during the flight testing phase of development, it was determined that positioning the nozzles at an angle of 85-degrees, rather than 90-degrees, was sufficient to avoid encountering any issue during takeoff, while no such issues were observed during landings at all.[16] Several different types of air intakes were also trialled, both to deter ingestion issues and the uneven start-up of the lift engines. Bleed air was also drawn from the Pegasus engines to the lift engines as a measure to address ingestion issues, while dedicated studies were performed on ground erosion effects.[17]
Into flight
On 10 February 1967, the first prototype (E1) conducted its maiden flight, powered by just the two Pegasus engines. During July 1967, the third prototype (E3), which was furnished with all ten of its engines, performed the first hovering flight.[4] During December 1967, forward-and-backward transitions between vertical and horizontal phases of flight were successfully conducted. On 28 February 1968, the first flight involving multiple transitions was performed.[4] According to aviation author Andrew Dow, while some initial teething issues were encountered, confidence in the aircraft grew quickly.[18] As the flight envelope was explored, test pilot Drury W. Wood performed several exploratory manoeuvres while flying the Do 31, on one occasion deliberately flying it backwards to prove it could be done and performing a barrel roll on another.[19]
Seeking to garner publicity for its new aircraft, Dornier flew one of the prototypes to the 1969
The Do 31 was the first, and so far only, vertical takeoff jet transport ever built. During April 1970, it was announced that the project had been terminated, although the Do 31 performed its final public flight on 4 May 1970 during the
During a later stage of development, Dornier planned to dispense with the Do 31's outer nacelles and their engines; in their place, larger
Aircraft on display
Both flying prototypes have been preserved in Germany, but the fate and current location of the non-flying testbed (E2) is not known.
- Dornier Do 31 E1, D-9530, is preserved and displayed at the Dornier Museum Friedrichshafen.[30]
- Dornier Do 31 E3, D-9531, was initially put into storage at Oberpfaffenhofen, then for several years on display in the open in the courtyard of the Deutsches Museum in Munich and after restoration is now on display at the
Operators
- German Air Force (Luftwaffe)
Specifications (Do 31E)
Data from The Observers Book of Aircraft.[32]
General characteristics
- Crew: Two
- Capacity: 36 troops or 24 casualty stretchers and 3,500 kg (7,715 lb) useful load
- Length: 20.53 m (67 ft 4 in)
- Wingspan: 18 m (59 ft 3 in)
- Height: 8.53 m (28 ft 0 in)
- Wing area: 57 m2 (613.56 sq ft)
- Gross weight: 22,453 kg (49,500 lb) (VTOL)
- Max takeoff weight: 27,422 kg (60,500 lb)
- Powerplant: 2 × Rolls-Royce Pegasus BE.53/2 turbofan, 68.95 kN (15,500 lbf) thrust each
- Powerplant: 8 × Rolls-Royce RB162-4D Vertically mounted turbojet lift engines, 19.57 kN (4,400 lbf) thrust each
Performance
- Maximum speed: 730 km/h (452 mph, 393 kn)
- Cruise speed: 650 km/h (404 mph, 351 kn)
- Range: 1,800 km (1,120 mi, 970 nmi) with maximum payload
- Service ceiling: 10,700 m (35,100 ft)
- Rate of climb: 19.2 m/s (3,780 ft/min) -using Pegasus engines only
See also
Related development
Aircraft of comparable role, configuration, and era
Related lists
References
Notes
- ^ By the time of the first flight, Rolls-Royce had taken over Bristol Engines.
Citations
- ^ Jackson 1976, p. 143.
- ^ a b Jackson 1976, p. 29.
- ^ a b c Dow 2009, p. 233.
- ^ a b c d Hirschel, Prem and Madelung 2012, p. 375.
- ^ Hirschel, Prem and Madelung 2012, p. 380.
- ^ Hirschel, Prem and Madelung 2012, p. 611.
- ^ Dow 2009, pp. 237-238.
- ^ "The Dornier DO-960 Analog Computer." vaxman.de, Retrieved: 5 August 2019.
- ^ Dow 2009, p. 239.
- ^ Hoffert, Fritz. "The Dornier DO 31 Jet-Lift Concept, A Light Military Transport with VTOL Capability." SAE Technical Paper 640229, 1964.
- ^ Dow 2009, p. 236.
- ^ Dow 2009, pp. 233-234.
- ^ Dow 2009, p. 234.
- ^ Dow 2009, pp. 234-235.
- ^ Dow 2009, p. 246.
- ^ Dow 2009, pp. 246-247.
- ^ Dow 2009, p. 247.
- ^ Dow 2009, pp. 246-248.
- ^ Dow 2009, pp. 248-249.
- ^ "FAI Record ID #5536 - Speed over a recognized course, München - Paris. Class H (VTOL aircraft)[permanent dead link]" Fédération Aéronautique Internationale Record date 27 May 1969. Accessed: 4 October 2015.
- ^ "FAI Record ID #15153 - Speed, München - Paris. Class H (VTOL aircraft) Archived 2016-03-04 at the Wayback Machine" Fédération Aéronautique Internationale Record date 27 May 1969. Accessed: 4 October 2015.
- ^ "FAI Record ID #15151 - Altitude, München - Paris. Class H (VTOL aircraft) Archived 2016-03-06 at the Wayback Machine" Fédération Aéronautique Internationale Record date 27 May 1969. Accessed: 4 October 2015.
- ^ "FAI Record ID #15152 - Duration, München - Paris. Class H (VTOL aircraft)[permanent dead link]" Fédération Aéronautique Internationale Record date 27 May 1969. Accessed: 4 October 2015.
- ^ "FAI Record ID #6370 - Distance, München - Paris. Class H (VTOL aircraft) Archived 2016-03-04 at the Wayback Machine" Fédération Aéronautique Internationale Record date 27 May 1969. Accessed: 4 October 2015.
- ^ Dow 2009, p. 250.
- ^ Dow 2009, pp. 250-251.
- ^ Hirschel, Prem and Madelung 2012, pp. 375-376.
- ^ a b Dow 2009, p. 253.
- ^ Dornier: die Chronik des ältesten deutschen Flugzeugwerks. Dornier GmbH (Friedrichshafen). Aviatic-Verlag, 1985.
- ^ Dornier Museum press release (German language) Archived July 18, 2011, at the Wayback Machine Retrieved: 9 August 2009.
- ^ Deutsches Museum, Do 31 Archived 2015-04-28 at the Wayback Machine www.deutsches-museum.de Retrieved: 5 April 2010.
- ^ Green, 1968. p. 88.
Bibliography
- Dow, Andrew. Pegasus, The Heart of the Harrier. Pen and Sword, 2009. ISBN 1-848-84042-X.
- Green, William. The Observer's Book of Aircraft. London. Frederick Warne & Co. Ltd., 1968.
- Jackson, Paul A. German Military Aviation 1956–1976. Hinckley, Leicestershire, UK: Midland Counties Publications, 1976. ISBN 0-904597-03-2.
- Hirschel, Ernst Heinrich., Horst Prem and Gero Madelung. Aeronautical Research in Germany: From Lilienthal until Today. Springer Science & Business Media, 2012. ISBN 3-642-18484-7.
- "V/STOL YEAR A Review of Progress by Rolls-Royce Jet Lift". Flight International. 8 (2859): 1031–1034. 26 December 1963. Retrieved 22 April 2019..
External links
- Inside The Cockpit - Dornier Do-31 Military Aviation History