Wednesday, February 3, 2010


Time for aerodynamics! I bought the ASA Complete Private Pilot, and so I have been making an effort to crack the books and learn the principles of flight. I've got several other supplements, but since the ASA book is reportedly the test prep for the FAA knowledge exam, I've been reading it and taking notes. It's very good and I recommend it to any student pilots out there. That plus Rod Machado's guide should get you ready.

I'm on aerodynamics, which is all wings and lift and Center-of-Gravity and drag. Very important information to know--it's good to understand the unseen hand of lift that will guide you as you fly, because it can reach out and swat you from the sky if you misuse it.

So, to reinforce it in my own head, here are some of the terms and concepts I have been trying to grasp:

Camber: The curvature of the upper surface of a wing.

Angle of Incidence: The angle at which the wing is fastened to the fuselage of the aircraft--usually the Angle of Incidence is one to three degrees.

Downwash: Airflow that is "washing off" the trailing edge of the wing. Related to Newtonian lift, in that "each action must have an equal and opposite reaction."

Chord Line: An imaginary line drawn from the leading edge of the wing to the trailing edge of the wing.

Relative Wind: The wind relative to the flight path. Typically opposite and parallel the flight track. If you are stationary and the wind is blowing from 020 degrees, that is the wind; if you are on a bicycle moving north at 20 knots the relative wind is south 20 knots.

Angle of Attack:
The angle between the chord line and the relative wind.

Mushing Flight: An attempt to maintain altitude with angle of attack alone and no power. Leads to a nose-up attitude with a loss in altitude. STALL IMMINENT IN MUSHING FLIGHT.

In addition to these concepts, I am trying to master the relationship between velocity and lift. According to the text, when you double your airspeed, you quadruple your lift. However when you halve your airspeed, you quarter your lift. The practical upshot of all this is that staying aloft requires speed. Don't slow down lest the ground rise up to befriend you.

Lift is also balanced by drag, which is broken into "parasite drag" and "induced drag." Parasite drag is from protuberances off the airframe (landing gear, antennae, etc.) Parasite drag will quadruple if you double your airspeed, which is the practical limiting factor in attaining high speeds.

Induced drag is a result of the meeting of high and low pressure air off the wing. Rotational forces as air spirals off the wingtips can also cause induced drag, and changes in the angle of attack will increase or decrease induced drag.

Fascinating stuff, no? These concepts are the building blocks of flying. Not as glamorous as slamming throttles and doing loop-de-loops, but by gum it's important to know the principles of flight.

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