New flight students need to know the basics. Old hands do, too. So whether you’re new to the flying game or an experienced pro, we need to learn, review, and expand on our knowledge base on a regular basis.
So let’s start with the basics, the four forces of flight. They are, in no particular order…
Lift, Weight, Thrust, and Drag.
The lift part seems obvious. You need to have lift to fly. But how much lift do you need? Well, you need exactly as much, or slightly more than the total weight of the aircraft and everything in it.
Hot tip number 1: Lift opposes weight, and vice versa. If you have 1,000 lbs of lift and apply it to an airplane that weighs 2,000 lbs…well it’s not to hard to see that this particular flight isn’t going anywhere.
Hot tip number 2: Thrust opposes drag, and vice versa. When an airplane is sitting idle on the ground, it has no thrust and no drag. But when you fire up that engine (whether it’s a turbine or a piston engine driving a propeller) the thrust rises to its maximum, and the airplane starts to move. It will continue to accelerate until eventually the drag (which is the force opposing the thrust) equals the total thrust, and the airplane speed stops climbing.
Hot tip number 3: You will occasionally hear the term, “steady state, unaccelerated flight.” That can throw you when you’re just getting started. But what it translates to is, your airplane is flying but it isn’t speeding up or slowing down. You’re not climbing or descending. You’re just plugging along in level flight (which is another way of saying, you’re maintaining your altitude) at a steady airspeed. When you’re in steady state unaccelerated flight, the lift exactly equals the weight of the aircraft, and the thrust exactly matches the drag being produced.
Remember, lift acts straight up, weight acts straight down, thrust acts in a forward direction, and drag tries to pull the airplane straight backward. The diagram would look like four arrows, pointing 90 degrees apart from each other. As a matter of fact, it looks exactly like the image included with this post, which the FAA was kind enough to include in Chapter 4 of the Pilot’s Handbook of Aeronautical Knowledge.
So now you know about the four forces of flight. And you thought learning to fly was going to be difficult!