The effort at the Lockheed-Georgia company to explore the use of the cross-flow fan in a propulsive wing was published by Hancock in 1980 [14]. Fig. 42 shows in some detail one example of how cross-flow fans could be integrated into a wing. Because conventional transonic wings are swept and flexible, a number of cross-flow fans would be used and distributed along the span of the wing from root to tip, and mounted internally in the trailing edge region. These fans would be connected via universal or flex-couplings at appropriate intervals and could be powered by turbines from gas generators mounted at the wing root and tip locations. In the Lockheed arrangement shown in Fig. 42, the cross-flow fans can be thought of as replacing conventional turbofans to provide the bypass ratio for improved propulsion efficiency. Hancock noted that the boundary layer over the entire suction surface of the wing can be ingested into the fans, offering the potential of reduced drag by delaying flow separation. Furthermore, the use of multiple gas generators was intended to provide some degree of safety in the case of one-engine failure and potential reduction in induced drag through favorable interference with the tip vortex. It should be pointed out, however, that the swept fan arrangement in Fig. 42 is potentially problematic as the inflow and outflow to the fan is not normal to the fan axis. Fig. 43 shows two possible sectional arrangements of cross-flow fan installations in wing trailing edges, as proposed by Hancock [14]. In both cases, the inlets of the fans can be flush or ram types, and they can ingest air from both the wing upper and lower surfaces. The fan exhaust can also be integrated with a Coanda-flap or jet-flap for circulation control.