Lockheed C-5 Galaxy Operations Limits Practice Test 2026 – Complete Exam Prep

At a given weight, altitude, and Mach number, the aircraft must produce a certain amount of lift to stay level. The flap/slat configuration changes the lift coefficient achievable at a given angle of attack, and it also changes drag. Leading-edge slats extend to increase lift at lower speeds with relatively modest drag increase, while trailing-edge flaps (especially heavy settings) add a lot of lift but also a lot of drag.

So, achieving the same condition that yields 215 knots at Mach 0.45 with 40% flaps and slats extended can also be done with slats extended only, no flaps. The slats provide enough lift to reach that speed/condition, but without the extra drag that flaps introduce. The other configurations rely more on trailing-edge lift and drag, which would shift the comfortable flight speed away from the 215 knots target at the same Mach.

In short, extending the slats alone delivers a similar lift effect to the partial-flap setup while keeping drag lower, making it the configuration that matches 215 knots at Mach 0.45.