Embry-Riddle Aeronautical University


No commercial airplane in service today is able to fly half great-circle distances over the globe and achieve the non-stop or the global range to any antipodal location on Earth. A subsonic jetliner has the optimum cruising speed at Mach numbers approaching the drag divergence Mach number while still preserving relatively high aerodynamic efficiency. Various fuel-flow laws were used to investigate the cruise performance of subsonic and supersonic aircraft. The effect of wind and aircraft weight and how it affects the optimal cruising airspeed was investigated. Of all different operational cruising techniques, the cruise-climb at high Mach numbers is the most efficient. In practice, due to airspace and ATC limitations it is substituted with the step-climb surrogate on long-range flights. The specific fuel consumption at upper tropospheric altitudes of about 0.45 lb/lb-hr is required in addition to cruise fuel-weight ratios in excess of 45% to hope for a subsonic jetliner achieving a global range with at least 10% of payload-fraction. Product of flight Mach number and the cruising aerodynamic efficiency will have to exceed 18 which is not going to be easy to achieve and will require substantial further improvements in supercritical airfoil designs. Supersonic airplanes, such as recently decommissioned, Concorde have dismal specific air ranges and range factors primarily due to the high specific fuel consumption of older turbojet engines, but also because the aerodynamic requirements necessitate thin delta-wings and long narrow bodies so that high fuel-weight ratios are only possible with relatively small payloads which drives the economy of the operation down. Essentially, accounting for wind and fuel reserves an airplane, weather subsonic or supersonic would require minimum range factors of about 22,000 NM in order to achieve the global ranges. Substantial improvements in subsonic and supersonic airfoil/wing aerodynamics, lightweight structures, lighter aircraft systems, improved and more efficient jet engine designs, flying higher, and perhaps introduction of the high-density fuels will be needed to achieve the global range.