Why Are Flaps Used in Some Soft-field Takeoffs?

Who said flaps don't increase lift? Flaps do increase lift. Reference Chapter 6 of the Pilot’s Handbook of Aeronautical Knowledge, which states, "Flaps are the most common high-lift devices used on aircraft. These surfaces, which are attached to the trailing edge of the wing, increase both lift and induced drag for any given angle of attack (AOA)."

Meg Godlewski

Tuesday, September 20, 2022 at 08:49 AM ET

Verified

A Cessna 170B with flaps extended. [Credit: Adobe Stock]

Key Takeaways:

Flaps are high-lift devices that increase both lift and induced drag, contrary to the initial premise that they do not increase lift.
A small amount of flaps is recommended for soft-field takeoffs because they lower the stall speed, allowing the aircraft to lift off at a lower airspeed.
Flap usage for takeoff varies by aircraft, with some requiring them for every takeoff and others only for special circumstances like soft fields; the specific setting is found in the Pilot's Operating Handbook (POH).
Using too much flap can create excessive drag, diminishing lift's effectiveness and potentially making takeoff difficult or impossible.

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Question: If flaps don’t increase lift, then why is a small amount of flaps used in soft-field takeoffs for some aircraft?

Answer: Who said flaps don’t increase lift? Flaps do increase lift. Reference Chapter 6 of the Pilot’s Handbook of Aeronautical Knowledge, which states, “Flaps are the most common high-lift devices used on aircraft. These surfaces, which are attached to the trailing edge of the wing, increase both lift and induced drag for any given angle of attack (AOA).”