Aviation & Avionics, Thursday September 18, Period 2

[crazypilotman.livejournal.com]

Murdock was sitting at the desk, giving lots of pets and scritches to a dog. An Afghan Hound to be precise.

"Morning class," Murdock chirped as the students filed in. "We've got a bit to cover today, so let's get started, okay?"

Abby Irene just settled herself quite like the lady she was and watched as Murdock went about his class instruction.

(ocd coming up! AbbyIrene!doggie modded with permission)

Comments

Re: Lecture!. part II

[crazypilotman.livejournal.com]

"Now let's look at the angle between the wing and the airflow," he continued, turning back to the classroom. "This is known as 'angle of attack'. If you stick your hand out the window of a moving car, keeping your hand level, you feel only air resistance. But turn your wrist, your hand wants to move up or down. That is aerodynamic lift. But as you increase the angle of your hand," and he moved his own hand around, "you start generating more resistance while losing much of the lift. The angle of attack can be changed by a set of wings to fit a certain circumstance. Nose up, with a high angle, for flying slowly; nose down when speeding. In long-distance cruising, 6 degrees is a reasonable average."

"Since wings have to support the weight of the craft, the lift L must equal the weight W. The lift is proportional to the wing area S and to dV^2, and so is the weight." He wrote W=0.3 dV^2S. on the board. "Now, you're probably wondering where the 0.3 comes from. That's also simple, it's related to the angle of attack in long-distance flight, for which the average value of 6 degrees has been adopted."

"Clear and consistent definitions for the units in which d, V, and S are expressed are needed. The best way to ensure consistency is to express S in square meters, V in meters per second, and d in kilograms per cubic meter. The rules of physics then require that the weight W in the equation be given in kilogram-meters per second squared. This frequently expressed in newtons. A newton is slightly more than 100 grams (3.6 grams)."

"A Boeing 747 has a wing area of 5500 square feet (511 square meters) and flies at a speed of 560 miles per hour (900 kilometers per hour; 250 meters per second). At an altitude of 12 kilometers (40,000), where the air density is only one-fourth its sea-level value of 1.25 kilograms per cubic meter, V = 250 meters per second, and S = 511 square meters." He scrawled all that out on the board as well. "Then we calculate from the equation that W must equal 2,990,000 newtons. And because a newton is about 100 grams, this corresponds to roughly 300,000 kilograms, or 300 tons. Which just happens to be the weight of a 747 at the midpoint of an intercontinental flight."

"So," he put the chalk down and spun to face the class, brushing his hands together to get the chalk dust off, "we now see how it all comes back to work together. Right?" he grinned. "Questions?"

Re: Lecture!.

[ktarian-wildman.livejournal.com]

Naomi listened carefully to the lecture and took detailed notes.

Re: Lecture!. part II

[death-of-hope.livejournal.com]

Anemone was making faces at all the math, but she was taking notes as quickly as she could.