The Science
of Aviation
Balance the four forces of flight, see how a wing makes lift and why it stalls, climb through the layers of the atmosphere, read Alberta’s wild flying weather, from chinooks to Hailstorm Alley, and find out what flying does to the human body.
- 00First Principlesp.2
- 01The four forcesp.4
- 02How wings liftp.5
- 03The atmospherep.6
- 04Alberta weatherp.7
- 05The body in flightp.8
- ✦Self-check · Make it · 5 Questions · Side Questp.9
You'll need: paper, tape, a pencil or straw, a desk fan with a guard, a protractor and a notebook.
Principles
A first principle is a basic truth you can build on. The science of flight rests on four: four forces act on every aircraft, wings turn moving air into lift, air gets thinner and colder as you climb and the body needs oxygen and steady senses.
What do I already know?
What is necessary?
Everything in this module is built from four bricks. Rate yourself on each one, then check the example to see if your rating holds up.
What is the objective?
By the end, you’ll be able to name and balance the four forces, explain lift with both Bernoulli and Newton, describe a stall, name the layers and gases of the atmosphere, explain chinooks, hail and icing, and describe how flying affects oxygen, ears and balance.
- 01Name the four forces.
- 02Explain lift two ways.
- 03Explain a stall.
- 04Name 3 layers of air.
- 05Explain a chinook.
- 06Describe hypoxia.
The list on the left is ours. Now make it yours. What do you want out of this?
How much do you know about the science of aviation right now? Shade the boxes in pencil. You'll come back at the end (p.9) and shade it again in pen.
Why start this way? When you know what you already have (1), what you need (2) and where you're going (3), you learn faster and you notice the gaps. Every module on the Aviation Path starts with these same three questions.
The four forces
Every aircraft balances lift, weight, thrust and drag.
Always at work
- Lift pushes up, made by the wings.
- Weight pulls down: gravity on the mass.
- Thrust pushes forward, from a propeller or jet.
- Drag pulls back: air resistance.
Level flight
Climb, dive, speed up
To climb, a pilot adds power and raises the nose so lift and thrust win for a while. To slow down, reduce thrust and drag wins. Every change in motion means the forces are unbalanced.
- Which of the four forces do you think is hardest to manage?
- Why can a heavy jet fly but a light brick can’t?
Force diagram
Draw a plane during takeoff, cruise and landing. Label all four forces with arrows. Make bigger forces longer arrows.A plane cruises level at steady speed. Which forces are equal?
How wings lift
Wings make lift by turning and speeding up air.
Both are true
Newton: the wing is tilted and curved, so it pushes air down; the air pushes the wing up (3rd law).
Bernoulli: air speeds up over the top of the wing, where the pressure is lower. Higher pressure underneath pushes up. Scientists use both to describe the same airflow.
Too steep
The angle of attack is the angle between the wing and the oncoming air. More angle gives more lift, up to a point.
Past a critical angle (often around 15°), the air can’t follow the top of the wing. It breaks away and lift drops suddenly: a stall. It has nothing to do with the engine.
The “equal transit” story
Some books say air over the top must “meet up” with air underneath at the back edge. That isn’t true: air over the top actually arrives first. The real reasons are the pressure differences and the downward push of air.
- Why do you think two explanations of lift are both taught?
- What do birds do with their wings when they land?
Spoon test
Hold a spoon loosely by the handle so its curved back just touches a gentle stream of tap water. What happens? Which way does the water bend, and which way does the spoon move?Does a stall mean the engine stopped?
The atmosphere
Pressure, gases and layers set the limits of flight.
From the ground up
- Troposphere: the bottom layer, where weather happens. Its top is roughly 8 km up near the poles and 16–18 km near the equator.
- Stratosphere: above it; contains the ozone layer. Airliners often cruise near the top of the troposphere or low in the stratosphere.
- Mesosphere and thermosphere above that.
And how it thins
Dry air is about 78% nitrogen and 21% oxygen, plus argon, carbon dioxide and traces of other gases.
The mix stays nearly the same as you climb, but the air gets thinner: at about 5,500 m (18,000 ft), pressure is roughly half of what it is at sea level.
Rivers of wind
Fast winds high in the atmosphere, the jet streams, flow mostly west to east. Flights eastbound across Canada are often faster than westbound ones because of them.
- Why does it get colder as you climb a mountain?
- What would happen to a plane above the atmosphere?
Bottle test
On your next road trip into the mountains or a flight, close an empty plastic bottle tightly at the high point. What happens to it when you come down? Explain why.Where does most weather happen?
Alberta weather
Chinooks, hail, ice and heat change how pilots fly.
Warm wind from the west
A chinook is a warm, dry wind that comes down the east side of the Rockies. Temperatures in southern Alberta can jump many degrees in hours. A band of cloud, the chinook arch, often marks it.
Air flowing over mountains can cause strong turbulence on its way down.
Hazards to pilots
- Hailstorm Alley: the area around Calgary and Red Deer gets some of Canada’s worst hail. Planes avoid thunderstorms, and a cloud-seeding program run for insurers tries to make hailstones smaller.
- Icing: super-cooled droplets freeze on wings and spoil lift.
- Density altitude: hot days and high airports thin the air, so planes need more runway.
Pilots check before every flight
Pilots read official reports and forecasts for wind, cloud, visibility, temperature and pressure. You’ll learn to read one, a METAR, in Lens 6.
- Which Alberta weather would worry a small-plane pilot most?
- How do you decide whether weather is “good enough”?
Weather diary
For 5 days, record the temperature, wind, cloud and any fog, rain or snow where you live. Which day would be best for a small plane? Which would be worst? Why?Why do planes need a longer runway on a hot day?
The body in flight
Oxygen, ears and balance all react to flight.
Thin air, slow brain
High up, each breath carries less oxygen. Hypoxia (too little oxygen) can cause headache, poor judgment and sleepiness, and some people feel oddly happy, so they don’t notice.
Canadian rules require oxygen for flight crew at higher altitudes; airliners keep the cabin pressurised.
Sense check
- Ears: pressure changes push on the eardrum. Swallowing or yawning opens a tube to balance it.
- Balance: the inner ear (vestibular system) senses turns. In cloud, with no horizon, it can be fooled into “feeling” level while turning: spatial disorientation.
- G-forces: tight turns press you into your seat.
A life-saving rule
Pilots without instrument training are told not to fly into cloud, because their senses can lie to them within minutes. Instrument-rated pilots train to trust the gauges over their feelings.
- Why might a pilot not notice they’re short of oxygen?
- Have your ears ever popped? What was happening?
Spin and stop
Sit on a swivel chair, close your eyes and have a friend turn you slowly for 20 seconds, then stop. Do you feel like you’re still moving? Stop at once if you feel sick. What does this tell you about the inner ear?Why do your ears pop when a plane descends?
Quick self-check
Six questions, covering every stop. Show your thinking. Answers are upside down at the bottom; no peeking till you're done.
1 · Name the four forces of flight.
2 · Give one explanation of lift.
3 · What is a stall?
4 · About what percent of air is oxygen?
5 · What is a chinook?
6 · What is hypoxia?
Re-shade your knowledge meter
How much do you know about the science of aviation now? Flip back to p.3 and shade the meter again in pen (or shade this one). Did any of the four bricks on p.2 move from "Not yet" to "Got it"?
Test a paper wing
When does a wing stall?
1 · Plan
Fold a paper wing (curved on top, flat underneath) and tape it to a pencil so it can tilt. Hold it in front of a desk fan on low at 0°, 10°, 20° and 30°. Watch how much it pushes up, and when it starts to flutter.
- Fan has a guard
- Same fan speed
- Angle measured
- Prediction written first
2 · Results
| Angle | Lift (none/some/lots) | Flutter? |
|---|---|---|
| 0° | ||
| 10° | ||
| 20° | ||
| 30° |
3 · Must-haves
- Fair test (one change)
- Stall angle estimated
- One explanation
- One way to improve
4 · What I found
Use a fan with a guard and keep fingers, hair and paper away from the blades. Ask an adult before using the fan.
5 Questions
I Still Have
This module didn't answer everything. Good. Write 5 new questions it didn't answer, one of each type below. There are no wrong questions, only ones nobody's asked yet.
★ Star the one question you'd most like answered. You'll need it on the next page.
1What I'll find out
Break your big question into 2 or 3 smaller ones you could actually answer.
2Where I'll look
3How I'll share it
Who I'll share it with:
Done by: