Multi-Disciplinary Optimization of a Near Sonic Airliner

Abstract

In the highly competitive world of commercial passenger aircraft, many have attempted to create an aircraft that completes its mission efficiently without sacrificing speed. Many believe that these parameters are mutually exclusive; high speed flight comes with a loss of efficiency. In this paper we rebut that proposition and propose a design that combines both speed and efficiency. Here, we size and configure a commercial transport aircraft with mission parameters similar to a Boeing 737-900 but with a significantly higher cruise speed and lower fuel burn. Our transonic cruise airliner carries up to 215 passengers in a single class high-density layout, flying a mission of 3,235 nM plus a 200 nM divert to alternate at a Mach 0.95 cruise. It performs this mission more efficiently than a Boeing 737-900. A byproduct of this design for maximum performance and minimum fuel burn is an aircraft that cruises at a high altitude (46,000-ft) and greatly exceeds the take-off and landing capability of conventional airliners (an estimated take-off field length less than 5,200 feet at maximum takeoff weight and an estimated landing distance at maximum landing weight less than 3,500 feet). This study documents our MDO tool construction process. It also explains our reasoning, developed by performing numerous MDO trade studies, which leads us to a novel configuration.Pressure Coefficient (i.e. at Mach=0) D = Drag (lbf) _ = Dynamic yaw coefficient E = Modulus of elasticity (lbf/in 2 ) F = Force (lbf) FF = Fuel flow (lbm/hr) I = Moment of Inertia k = Airfoil technology factor L/D = Lift to drag ratio λ = Taper ratio LCDP = Lateral Control Departure Parameter Λ LE = Leading edge sweep (deg) M cruise = Mach number at cruise M D = Mach number during dive maneuver M(L/D) = Aerodynamic efficiency parameter MTOW = Maximum takeoff weight (lbm) MZFW = Maximum zero fuel weight (lbm) n = Load factor (g's) n z_max = Maximum load factor along the z axis (g's) OEW = Operational empty weight (lbm) ROC = Rate of climb (ft/min) SET = Specific excess thrust S L = Landing field length (ft) SM = Static margin SR = Specific range (nM) S ref = Wing reference area (ft 2 ) S TOBFL = Take-off balanced field length (ft) W/S = Wing loading (lbm/ft 2 ) σ = Density ratio of air relative to sea-level T = Thrust (lbf) TOP 25 = Take-off parameter t/c = Wing thickness (%) T/W = Thrust to weight ratio (lbf/lbm) V = Air speed (nm/hr) V A = Design maneuvering speed V C = Design cruise speed V D = D e s i g n d i v e s p e e d V E = Design slow down speed V F = Design flap speed V H = Design level flight speed ω dr = Dutch roll natural frequency (Hz) ω sp = Short period natural frequency (Hz)