Airline Transport Pilot and Type Rating for Airplane Category › I. Preflight Preparation › Task D. High-Altitude Aerodynamics (ATP) (AMEL, AMES)

AA.I.D.K7

Knowledge

Maximum Lift over Drag Ratio (L/DMAX).

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Get a short, cited explanation of this element written from the FAA handbooks: the core idea, the numbers that matter, common test traps, and a quick self-check.

From the FAA library

Pilot's Handbook of Aeronautical Knowledge p. 11-10
Chapter 11: Aircraft Performance › Climb Performance Factors › Range Performance
speed to power required is greatest. [Figure 11-11] The maximum range condition is obtained at maximum lift/ drag ratio (L/DMAX), and it is important to note that for a given aircraft configuration, the L/DMAX occurs at a particular…
Pilot's Handbook of Aeronautical Knowledge p. 5-5
Chapter 5: Aerodynamics of Flight › Lift/Drag Ratio
maximum lift/drag ratio (L/DMAX) occurs at one specific CL and AOA. If the aircraft is operated in steady flight at L/DMAX, the total drag is at a minimum. Any AOA lower or higher than that for L/DMAX reduces ... consequently increases the total drag for a given aircraft’s lift. Figure 5-6 depicts the L/DMAX by the lowest portion of the blue line labeled “total drag.” The configuration of an aircraft has a great effect…
Airplane Flying Handbook p. G-10
Glossary › Numbers and Symbols
speed (L/DMAX). The point on the total drag curve where the lift-to-drag ratio is the greatest. At this speed, total drag is minimized. Mixture. The ratio of fuel to air entering the engine’s cylinders. MMO. Maximum operating…