Educational by Chapter of the Powered Paragliding Bible

I: First Flight

01 Training Process

02 Gearing Up

03 Handling the Wing

04 Prep For 1st Flight

05 The Flight

06 Flying With Wheels 

II: Spreading Wings

07 Weather Basics

08 The Law

09 Airspace   

10 Flying Anywhere

11 Controlled Airports

12 Setup & Mx

13 Flying Cross Country

14 Flying With Others

III: Mastery

15 Adv Ground Handling

16 Precision Flying

17 Challenging Sites

18 Advanced Maneuvers

19 Risk Management

20 Competition

21 Free Flight Transition

IV: Theory

22 Aerodynamics

23 Motor & Propeller

24 Weather & Wind

25 Roots: Our History

V: Choosing Gear

26 The Wing

27 The Motor Unit

28 Accessories

29 Home Building

VI: Getting the Most

30 Other Uses

31 Traveling With Gear

32 Photography

--- Not in book ---

33 Organizing Fly-Ins

34 Places To Fly

35 Preserving the Sport

36 Tandem

Chapter 22: Aerodynamics

Nov 8, 2007 | Section IV Theory & Understanding

There's more than meets the eye on how our unusual craft flies and it's not all intuitive.

Flight is a fine dance of forces that must remain in step to keep you aloft and under control. We follow the same basic aerodynamic rules as our fixed-wing brethren with a few important differences.

The PPG Bible goes into great detail about these but some additional material is included here including what may be added to the aerodynamics chapter (was added at page 226).

More Power to Fly Downwind?

Does it take more power to fly downwind?

Of course not! Your wing doesn't care which way the air is moving. Or does it?

It turns out that there is one little exception where the downwind demon is real, albeit in a minor, rare way. Check out the PDF file. It covers an obscure situation where it can require more power to fly downwind than upwind.

The gist is that, with a wind gradient very close to the ground, the wing may be flying in different airflow than the motor 15 feet below. The PDF explains how that requires less power when flying upwind than downwind in such situations.

The discovery of this was kind of funny. At a fly-in Nick Scholtes quietly pulled me aside and said "Jeff, now we both know that there is no difference in flying upwind or downwind but I just got back and swear that it took me more power to fly downwind than upwind." He went on to explain how he did several runs to verify it and only noticed it down low, at maybe five feet high. So I went out to see if I could duplicate his observation and, sure enough, I did—needing several hundred more RPM to go downwind as upwind. That's what got me trying to figure out what was going on and a few days later put it all together. Read the PDF to see what was happening.

Wing Loading

See also Choosing a wing.

One important area of understanding is wing loading. How much weight is carried per square meter of wing. It is the all-up flying weight (pilot, motor, fuel, wing) divided by the wing's projected area.

Sales literature may not always say flat or projected so double check that you're using the projected value. Add up your weights, including fuel and wing then divide that number into the wing area.

For example, a Spice 22 has a projected area near 19 m². My 145 pound self with a 70 pound paramotor and 10 pounds of gas under a 12 pound wing gives an all up flying weight of 237 lbs. Wing loading is then 237 / 19 or  12.5 lbs per m².

This important value should be considered buying a different wing. Go here to see how.

This illustration was included on page 216 but reduced in contrast for layout purposes and because its content is repeated in others. The full contrast version here clearly shows the basic forces at work during level flight including chord line and angle of attack.

© 2016 Jeff Goin & Tim Kaiser   Remember: If there's air there, it should be flown in!