Book 23, Question 12
How Are Lift and Weight Balanced in Level Flight?
When a plane flies straight and level, all the forces balance. Lift matches weight, and thrust matches drag. But the balance keeps changing a little!
More fun facts
- When a plane cruises steadily, lift equals weight and thrust equals drag.
- With the forces balanced, the plane keeps the same speed and height.
- A cruising airliner is the best real example of this.
- The plane does get a little lighter as it burns fuel, but that's small next to its total weight.
- If the pilot changes the throttle, the forces stop being balanced and the plane speeds up, slows down, climbs or sinks.
Sources: NASA
Questions kids ask
How do you find a plane's speed over the ground?
Add the wind to the plane's airspeed. A tailwind speeds it up, and a headwind slows it down.