Background During the 1950s, rapid advances in the field of
jet propulsion, particularly in terms of increased thrust and compact engine units, had contributed to an increased belief in the technical viability of vertical takeoff/landing (
VTOL) aircraft, particularly within
Western Europe and the
United States. During 1950s and 1960s, multiple programmes in Britain, France, and the United States were initiated; likewise, aviation companies inside
West Germany were keen not to be left out of this emerging technology. Shortly after 1957, the year in which the post-
Second World War ban upon West Germany operating and developing combat aircraft was lifted, German aviation firms
Dornier Flugzeugwerke,
Heinkel, and
Messerschmitt, having also been allowed to resume their own activities that same year, received an official request from the
German Federal Government that urged them to perform investigative work on the topic of VTOL aircraft and to produce concept designs. As such, multiple companies commenced work on their own conceptual designs for VTOL-capable
interceptor aircraft; in order for these designs to be operationally relevant and viable, it was recognised that it would be necessary for the flight performance to equal that of conventional interceptors of the era, such as the contemporary
Lockheed F-104G Starfighter. Over time, two separate and distinct requirements emerged, one calling for a VTOL-capable successor to the F-104G interceptor while the other sought a VTOL successor to the Italian
Fiat G.91 ground-attack fighter. According to aerospace publication
Flight International, this call for a Fiat G.91 replacement, which came under a
NATO requirement, known as
NBMR-3, was a crucial trigger and greatly influenced the development programme that would lead to the VAK 191B. In conjunction with these requirements being on offer, Germany's
Federal Ministry of Defence (BMVg) championed for the merger of the competing companies; it deliberately withheld the issuing of a development contract in order to incentivise companies to undertake such activities. As such, during September 1961, a new German aircraft company, known as
Vereinigte Flugtechnische Werke (VFW), was formed as
joint venture between
Focke-Wulf and
Weser Flugzeugbau, to develop its own VTOL strike aircraft. Initially,
Italian aircraft manufacturer
Fiat was also a participating company in VFW, however, Italy later chose to withdraw from the joint development agreement with Germany during 1967. Despite this decision, Fiat remained as a major sub-contractor for the venture, being responsible for the production of various structural elements such as wings, tailplanes and some of the fuselage. Ultimately, VFW's design team decided to adopt the
Rolls-Royce/MAN Turbo RB.193-12 engine to provide both
lift and
cruise, which was augmented by a pair of Rolls-Royce vertical lift engines. In practice, this arrangement meant during vertical hover, all of the lifting thrust could either be generated by the propulsion engine, or entirely produced by the two lift engines, or some combination thereof; analysis determined that the optimum thrust-generation configuration would be a 50–50 split between both engine types. During mid-1963, the in-development aircraft received its design designation of
VAK 191B. Reportedly, the initials in this designation stood for
Vertikalstartendes Aufklärungs-und Kampfflugzeug (in English: vertical take-off reconnaissance and fighter aircraft), the numbers were to indicate its role as a successor to the Fiat G.91, while the
B suffix was to show that the aircraft was the second of the four designs to be studied for this purpose. During April 1969, the first prototype was rolled out at VFW's facility in
Bremen, and was later displayed at that year's
Hannover Air Show. ==Surviving aircraft==