Compound Aircraft Transport 1) Mx – 1018 project B-29/F-84 2) Tom-Tom Project B-36F/F-84 Model Problems of Compound Flight Configuration IConfiguration II C-5 C-27

Compound Aircraft Transport Wind Tunnel Tests Vortex Lattice Calculations Water Tunnel Flight Controls Propulsion Studies Finite Element Structures Tools and Facilities

Compound Aircraft Transport Calculated C-5 / C-27 Drag Coefficients -Induced drag reduction as tips approach each other d

Compound Aircraft Transport

Scale of Hitchhiker System Range Ratio Effect of Hitchhiker Size on Range

Compound Aircraft Transport Mothership/Hitchhiker Attached by Hinge Carbon Fiber/foam fixed wing Balsa wood hinged wing (NACA airfoil) has option to add varying masses to the tip of the hinged wing Wind Tunnel Experiment

Compound Aircraft Transport In plane bending ( New mode) Normal mode analysis of C-5/C-27 C-5 Solo 1 st Bending Mode 1.4 Hz Mode # 1. Torsion, 0.25 HzMode # 3. In plane bending, 0.53 HzMode # 2. Bending, 0.50 Hz Mode # 4. Bending, 1.20 Hz Mode # 5. In plane ending, 2.11 Hz

Compound Aircraft Transport T HH /T HHsolo =1.275 T HH /T HHsolo =1.0 T HH /T HHsolo =0.0 Compound Aircraft Transport Minimal fuel consumption Beta: mother ship drag benefit a: Hitchhiker drag benefit

Compound Aircraft Transport C-5/C-27 Combined Maximum stress shifted closer to the tip FE Static Analysis Maximum stress lb/ft 2

Compound Aircraft Transport All Aircraft get Lift Benefit and Drag Reduction - Attached Flight: system drag is less than mother ship alone - Formation flight: hitchhiker benefits in lift and drag - Optimal position: hitchhiker behind, inboard and above mother ship wing

Compound Aircraft Transport Attached hitchhikers ride stably and with minimal control - Hinged connection should be stable with no need for active control - Hitchhikers may turn engines off or operate at low throttle

Compound Aircraft Transport  Local minimum fuel consumption can be achieved with:  transport providing all thrust or  by splitting thrust between transport and hitchhiker T HH /T HHsolo =1.275 T HH /T HHsolo =1.0 T HH /T HHsolo =0.0 Minimum fuel consumption Scale of Hitchhiker System Range Ratio  Hitchhikers ride for free and may even chip in gas.  Mother ship may save fuel. Significant fuel savings

Compound Aircraft Transport Structural modifications are needed to improve the static and dynamic response of the compound - Maximum stress shifted towards the tip of the wing - Presence of new normal modes of the compound system Problems can be solved by structural reinforcement and/or controls

Compound Aircraft Transport Attached or in Formation ? Attached: - a little greater drag benefit - with hitchhiker engines off, significant increase in range - stable and safe flight with no controls Formation: -flight control nightmare - requires running VSTOL engines that are inefficient for high speeds

Compound Aircraft Transport o Wind tunnel tests with hinged attached models o Measure forces and moments o Measure unsteady pressures on wing models o Monitor the wakes with high frequency-response 7- hole probes o Study the flow field with particle-image velocimetry o Model the dynamics of hinged aircraft motion o Couple aerodynamics with structural codes to predict aeroelastic behavior o Employ the codes thus develop in design.

Compound Aircraft Transport Structural analysis and design  Detailed high fidelity analysis of compound aircraft configurations  Steady and unsteady aeroelastic analysis  Identification of cost effective structural modification for existing aircraft  Development of design tools for new aircraft designed specifically for compound flight  Propulsion  Expand current engine fuel consumption analysis to account for various sized transport and hitchhikers.  Develop engine models to allow examination of engine configurations to allow high bleed flow rates.  Integrated computational/experimental study of the aerodynamics of a CAT  Design code for required camber /twist and simulation using devices

Compound Aircraft Transport  Multidisciplinary Design and Optimization (MDO)  Evaluation of MDO platforms (e.g. Model Center: Phoenix Integration, insight: Ingenious Software)  Parametric detailed (realistic) structural analysis models for MDO  Identification and coordination of systems and subsystems variables for MDO  Response surface models for representation of disciplines within the MDO