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Drag vs Speed. L/DMAX occurs at minimum Total Drag (e.g. Parasite plus Induced) Coefficients of drag C D and lift C L vs angle of attack. Polar curve showing glide angle for the best glide speed (best L/D). It is the flattest possible glide angle through calm air, which will maximize the distance flown.
The speed to fly is the optimum speed through sinking or rising air mass to achieve either the furthest glide, or fastest average cross-country speed. [1] Most speed to fly setups use units of either airspeed in kilometers per hour (km/h) and climb rate in meters per second (m/s), or airspeed in knots (kn) and climb rate in feet per minute (ft ...
Best power-off glide speed – the speed that provides maximum lift-to-drag ratio and thus the greatest gliding distance available. V BR: Best range speed – the speed that gives the greatest range for fuel consumed – often identical to V md. [35] V FS: Final segment of a departure with one powerplant failed. [36] V imd: Minimum drag [37] V ...
Glide ratio usually varies little with vehicle loading; a heavier vehicle glides faster, but nearly maintains its glide ratio. [22] Glide ratio (or "finesse") is the cotangent of the downward angle, the glide angle (γ). Alternatively it is also the forward speed divided by sink speed (unpowered aircraft):
Pearson needed to fly the 767 at the optimum glide speed to have the maximum range and, therefore, the largest choice of possible landing sites. Making his best guess as to this speed for the 767, he flew the aircraft at 220 knots (410 km/h; 250 mph). First Officer Quintal started to calculate whether they could reach Winnipeg.
A straight line from the origin to some point on the curve has a gradient equal to the glide angle at that speed, so the corresponding tangent shows the best glide angle tan −1 (C D /C L) min ≃ 3.3°. This is not the lowest rate of sink but provides the greatest range, requiring a speed of 240 km/h (149 mph); the minimum sink rate of about ...
where a 0 is 1,225 km/h (661.45 kn) (the standard speed of sound at 15 °C), M is the Mach number, P is static pressure, and P 0 is standard sea level pressure (1013.25 hPa). Combining the above with the expression for Mach number gives EAS as a function of impact pressure and static pressure (valid for subsonic flow):
The Netto variometer will always read zero in still air. This provides the pilot with the accurate measurement of air mass vertical movement critical for final glides (the last glide to the ultimate destination location). In 1954, Paul MacCready wrote about a sinking speed correction for a total energy venturi. MacCready stated, "In still air ...