Now you understand the basic principles of flight. You understand lift, weight, thrust, and drag. You know what an airfoil is and how it works.  You have a solid grasp of the physics of how an airplane flies.

Now let’s talk about the powered parachute.  You probably already realize a powered parachute doesn’t look exactly like the fixed-wing aircraft we used in the examples. You may be asking yourself why you bothered to read about airfoils and the physics of how an airplane flies when a powered parachute is different. It doesn’t even have wings!  It flies under a parachute.

You’re right.  A powered parachute is different from a fixed-wing aircraft.  However, the forces of lift, weight, thrust, and drag and the concepts of airfoils still apply. The application in some cases is a little different for powered parachutes, but it is still applicable.

The airfoil on a powered parachute isn’t as obvious as it is on a fixed-wing aircraft. In fact, when it’s packed in its storage bag or even when it’s laid out on the ground behind the cart in preparation for takeoff, the ram-air parachute doesn’t look like an airfoil at all.  Once you bring it up and the cells are inflated, it takes on the shape and function of an airfoil.  Just like the airfoils of fixed-wing aircraft, it has a leading edge, trailing edge, chord, and camber.

Since the ram-air parachute takes on the shape and function of an airfoil once it is inflated, lift works the same on a parawing as it does on any other airfoil.  Once the chute is up and inflated, think of it like you would any rigid airfoil.

Gravity acts on powered parachutes the same way it does on any other object. In a powered parachute, weight is the opposing force to lift.  There is a difference here, though. Not only does weight oppose lift in a powered parachute, it also provides thrust. That will be covered in more detail in the discussion of thrust.

When dealing with thrust affecting a powered parachute, you must first determine if the aircraft is on the ground or in flight. On the ground, the engine and propeller provide thrust.  Increased RPMs yield increased thrust and result in an increase in the speed of the forward motion. If the chute is up and inflated, the increased speed will increase lift.  When lift is greater than weight, you will take off.  Once airborne, the engine and propeller no longer control speed.  They only control the rate of ascent and descent by altering the angle of attack. Weight gives the powered parachute its forward motion. By design, as the chute falls through the air, it moves forward instead of straight down. The more weight the powered parachute is carrying, the faster it flies.  A lighter flight weight will yield a lower airspeed, but increase the climb rate. Air speed is constant. Thrust from the engine has nothing to do with it.

The most noteworthy aspect of drag when considering powered parachutes is the tremendous amount of drag on the chute. All that drag explains why such a lightweight aircraft with such a powerful engine flies at only 25 to 32 miles per hours (depending on weight).

So, if the parawing creates so much drag, why not go with a faster, more efficient fixed-wing design?  If you’re asking that question, you have the wrong attitude.  The relatively slow speed of the powered parachute isn't a liability; it’s an asset.  Flying slow and low is one of the best things about flying an ultralight aircraft. If you’re interested in breaking speed records, you’re looking at the wrong aircraft.

Another feature of the parawing is safety. The powered parachute has excellent stability in flight due to the phenomena known as the pendulum effect.  Because of the fixed air speed and pendulum effect of the cart riding under the parachute, the wing is virtually impossible to stall.  In addition, other types of ultralight aircraft, when equipped carry ballistic recovery systems (BRS). The BRS is a parachute in a canister.  If things go horribly wrong, the pilot shuts down the engine and pulls a handle to activate the BRS. In a powered parachute, your BRS is already activated. Finally, because forward thrust is caused by weight instead of the engine, if the engine quits, the powered parachute flies with no loss of speed or maneuverability (except of course that you can’t climb anymore). In fact, it flies better because the torque from the engine isn’t turning the aircraft to the left any more.

That’s a quick overview of how the physics of flight relate to the powered parachute.