The Paths of Soaring Flight

The following sections are included:

• FOREWORD

• CONTENTS

The following sections are included:

• Units

• Dimensionless Coefficients and Other Numbers

• Lift Curve Slope

• True and Equivalent Speeds

• Boundary Layers

• The Effect of Flaps

• References

The following sections are included:

• Wings of Finite Span

• Three-Dimensional Lift Curve Slope

• Drag of Three-Dimensional Wings

• Tail surfaces

• References

The following sections are included:

• The Parabolic Polar

• Significant Speeds

• The Non-Parabolic Polar

• Reynolds Number Effects

• A Note on the Analytical Polar

• References

The following sections are included:

• The General Equations of Motion for Flight in a Vertical Plane

• Simplifications

• Remarks on These Equations

• Results for a Parabolic Polar

• Best speeds for Motor Sailplanes

• Performance in Turning Flight

• Ground Effect

• References

The following sections are included:

• The Variometer and Similar Devices

• Total Energy

• Electric Variometers

• Air Mass Movement

• References

The following sections are included:

• General

• The Altimeter

• The Airspeed Indicator

• Effect on Best Speeds to Fly

• Other Errors

• References

The following sections are included:

• Thermals in the Laboratory

• Thermals in Practice

• Mathematical Descriptions

• Power-Law Velocity Distributions

• Other Parabolic Thermals

• Spherical Bubbles

• A Modified Parabolic Distribution

• General Remarks on Thermals

• Cloud Streets

• Waves

• The Wind

• The Standard Atmosphere

• References

The following sections are included:

• The Optimum Rate of Climb

• A Little History

• The Classical Analysis

• Effect of Down-Currents

• The BGA Handicapping System

• References

The following sections are included:

• Little Tricks with Variometers

• Corrections to the Variometer

• References

The following sections are included:

• Dolphin Flying

• The Carriage of Water Ballast

• References

The following sections are included:

• The Calculus of Variations

• Analysis of the Best Speed to Fly

• Example of an Unflapped Sailplane Flying Under a Cloud Street

• A Numerical Example

• A Final Caution

• References

The following sections are included:

• Wind Components

• Optimum Glide Angles

• Use of Lee Waves

• References

It is common knowledge among soaring pilots that the tail lift force produces some extra induced drag, since the tail is simply a small wing. It is also common to suppose that down-loads are more unfavourable than up-loads, on the argument that up-loads relieve the wing lift, whilst down-loads increase it. On this basis, pilots have tended to think in terms of reducing the down-load on the tail at high speeds by ballasting the sailplane to get the centre of gravity (or centre of mass, as is now the more popular expression) at the aft limit (or perhaps even further aft). In fact a consequence of the mutual interference between the wing and tail is that the direction of the tail lift force is of no consequence. Other things being equal, a certain up-load on the tail produces the same increment in induced drag as a down-load of the same amount…

Since New Soaring Pilot was written, it has become possible to obtain electronic devices which will perform most of the calculations required in soaring flight. Many of the more complex sums, previously impossible to carry out in the heat of the moment, are now little more than pressing a few buttons. The complexity of the devices varies enormously. On the one hand, a relatively simple contrivance will work like a normal audio variometer in thermals while also giving the rate of climb averaged roughly over the previous turn, becoming a-best-speed-to-fly indicator between thermals and storing a vast number of polars probably in a simplified form such as Eq. (3.2), with the capability to deal with various weights due to the presence or abscence of water ballast and because the appropriate chips are very cheap, a few extras such as temperature and battery volts are thrown in for good measure. At the other end of the scale is the device with built-in Global Positioning System (GPS), which not only carries out most of the calculations in this book but records the entire flight as well. It will also provide instantaneous data on a vast number of parameters. The price of such a device would have bought quite a sophisticated sailplane not many years ago and it comes with an instruction manual of amazing complexity…

The following sections are included:

• Appendix 1: SOME USEFUL GENERAL REFERENCES

• Appendix 2: CONVERSION FACTORS

• Appendix 3: THE STANDARD ATMOSPHERE

• SYMBOLS

• INDEX

• LIST OF AUTHORS QUOTED AT THE END OF EACH CHAPTER