Today’s Monochrome Monday post is an addendum to last week’s Monochrome Monday post that talked a bit about how airplanes change the shape of their wings to maintain lift in slow flight.

An accurate explanation of the theory of lift is complicated. One simple but essential requirement for generating lift is that air must move smoothly across the surfaces above and below the wing. Maintaining the smooth airflow and producing sufficient lift is harder for wings to do in takeoffs and landings where they operate at a higher angle of attack (generally nose up or nose down attitude) compared to straight-and-level flight and slower airspeed. Operations in the takeoff and landing phases can be referred to as “slow flight.”

In slow flight situations, maintaining smooth airflow over the wings to produce sufficient lift requires that airplanes change the shape of their wings. That is what last week’s post illustrated. A portion of the wing’s leading edge, the slats, move forward and down. On the trailing edge of the wing, flaps move down and to the rear.

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Slats move forward and down.  Cathay Pacific A330-300 takeoff from Ninoy Aquino International Airport Manila, Philippines. 
Flaps move to the rear and down.  Japan Airlines 767-300 takeoff from Naha International Airport Okinawa, Japan

Today’s Monochrome Monday photo (below) shows how birds accomplish the same thing. They have been doing it for millions of years without knowing a thing about fluid dynamics, aerodynamics or aeronautical engineering.

Seagull landing in slow flight configuration.

My seagull photo depicts a seagull in ideal, slow-flight configuration for landing — nose-up high angle of attack, wing leading edge tilted down (like slats), wing trailing edge extended downwards like flaps), and landing gear down.

Final Thought

Fortunately pilots don’t need to be able to know all of the scientific theory and mathematical equations behind flight. Like birds, they just need to know what works and what doesn’t as far as safely flying the plane in all phases of flight.