Lift-to-Drag Ratios
Summary
On Table 1 we have a summary of aerodynamic efficiency L/D (for high speed flows, transonic as well as supersonic, the efficiency is M L/D, with M = free stream Mach number). Some data are estimated. The L/D quantity is important because it also appears in the Breguet range equation.
The ratio L/D is sometimes called glide number, or glide ratio, or
finesse.
[*] Estimated data
Wings for Racing Cars, Re > 
2.5-3.5 Hypersonic Waverider , M=8-10 [*] 3 ÷ 4 Supersonic Jet Transport (Concorde) 8 Tilt-rotor aircraft 9÷10 New Supersonic Transport [*] 15 Oblique Flying Wing [*] 16÷17 Subsonic Jet Transport 16÷18 Bomber B-52 20 Airfoil Eppler E 193 , Re=0.1 50 Airfoil Liebeck L 1003, Re= 220
Aircraft (year) (L/D)max
Boeing B707-320 19.4
Douglas DC-8 17.9
Airbus A320 17.
Boeing 767-200 19.
Boeing 747-100 17.7
Douglas DC-10 17.7
Lockeed Tristar L1011 17.0
Douglas DC-9 (1966) 16.5
Boeing B727-200 16.4
Fokker 50 (1966) 16
Douglas DC-3 (1935) 14.7
Ford Trimotor (1927) 12.
Wright Flyer I (1903) 8.3
Bird L/D House Sparrow (passer domesticus) 4. Herring Gull (larus argentatus ) 10. Common Tern (sterna hirundo ) 12. Albatross (diomeda exulans ) 20.