The term “(L/D)max” refers to the maximum lift-to-drag ratio that an aircraft can achieve. It is a crucial parameter in aircraft design and performance analysis because it indicates the point at which the aircraft is operating most efficiently in terms of generating lift for a given amount of drag. Pilots and engineers use this ratio to optimize an aircraft’s performance, especially during cruising flight.
The formula for estimating the maximum lift-to-drag ratio, or (L/D)max, is relatively straightforward:
    
- (L/D)max” is the maximum lift-to-drag ratio, which is a dimensionless quantity.
- “L” is the lift generated by the aircraft (typically measured in newtons or pounds-force).
- “D” is the drag experienced by the aircraft (typically measured in newtons or pounds-force).