On the aerodynamic optimization of mini-RPV ... - CAFE Foundation

The aerodynamic efficiency index is over 12.0.The schematic layout of the 4-seat GA configurationis shown in Fig. 17; a high-wing arrangement wasselected with a span of 360 in. and a 0.45 taperratio. The useful fuselage length i s 147 in. whilethe overall fuselaoe lenoth i s 174 in. The emDennageis supported -by twin booms and it comprisestwin rudders.ConclusionsIt has been shown that the simole addition ofa conventional NACA wing to the tested optimizedsystem comprising axisymmetric body, boundary-layercontrol and stern jet propulsion yields a predictedaircraft perfonnance which is superior to currentmini-RPV and small GA aircraft levels.Schematic Layout4-Seat GA AircraftConfiguration2903 Ib Gross Weight2% MPH Speed120 HP (Tripped Trans. )A 250 lb gross weight mini-RPV could be flownat 100 Kn with 7.0 HP; a 2-seat 1675 lb GA aircraftcould be flown at 200 MPH with 69 HP, and a 4-seat2900 lb GA aircraft could be flown at 200 MPH with120 HP.The general trend of the aerodynamic efficiencyindex E against the thrust coefficient CT is shownin Fig. 18 for both free transition and transitiontripped at 10% length; it can be seen that thethrust coefficient should be kept above a valueof 0.025 in order to achieve aerodynamic efficiencyindex values above 12.0. This can be done byadjusting the gross weight Wo against the fuselagevolume V and the speed Uo.Better results can be expected if the liftsystem should be integrated, i.e. if the fuselagesuction air mass flow should be directed laterallyinto the wings to supply jet flaps or circulationcontrolwall-jets. The limitation then would bethe allowable wing loading and the wing's induceddrag, as the lift coefficient is substantiallyincreased by the jet-flap or by the circulationcontrol.The air mass flow would serve three purposes:(a) fuselage boundary-layer control, (b) wing liftenhancement, and (c) propulsion. Also the suction'smomentum drag is minimized since only theinner boundary-layer flow i s drawn into the slotat Sta. 1 (Fig. 5); it is estimated that a 33%drag saving is achieved, as compared to free-streamflow intake, at the point of equilibrium for thebody alone. The next step of this program is expectedto be the wind-tunnel test of the 20 in.diameter model in the arrangement of Fig. 14; thewing pylon would be installed exactly as thepresent strut. A second step would be the investigationof the optimum fineness ratio; the 2.72fineness ratio was selected originally for LTAapplication. A preliminary theoretical parametricstudy indicates that the optimum should be near6 and that further power reduction can be expected.174" I181 Free Transitionand16 - Transition TrippedT aQ 58%\,**--o-C 14 - # .ox-Ea-.$< 12E=-lO-"35u II 8.-gi0- ,2'6--I'2-SeatGAB 123 MPH- I// Mini-RPV2 -,'@1WKn 701I I I I0 0.01 0.02 0.03 0.04 0.05Thrust Coefficient CT = T/qoVo'66-_/--/'# s t Transition,*' Tripped B 10%;:LMPH 7Fig. 17Schematic layout of 4-seat GA aircraftconfigurationFig. 18 Aerodynamic efficiency index E vsThrust coefficient CT11