I have noticed that nothing was published in this blog for a rather long period, and my readers have my apologies. This is largely attributed to the fact that I have had little time since the fourth year in the Engineering Tripos started, and partially because a lot of the interesting things that I work on cannot really be freely talked about.
Over the past year, in response to the initiative by the former Webmaster of the Cambridge University Gliding Club (CUGC) to add meat to the existing CUGC WiKi, I have created three articles there explaining the aerodynamics of sailplanes.
It has come to my attention that most people, despite having substantial scientific knowledge or engineering training, have difficulties in understanding how sailplanes fly without the use of engines. Many hold the belief that sailplanes fly with the wind and I have been asked questions such as ‘what if the wind stops blowing when you are in the air’ and ‘what if the wind blows you away from the airfield’. Some do not understand why a glider needs controls. Some, at least I have heard, having flown with the Air Force for the past 30 years and being one of the few pilots who flies the SR-71 Blackbird, got absolutely shocked by the fact that a glider can go cross-country. Such misunderstandings and misconceptions, not infrequently leading to an echoing connotation of ‘danger to life’ when the sport is considered, hinders the spread of gliding to the general public more than anything else in my opinion.
Cambridge University Gliding Club, part of a university renowned for its world-leading scientific and engineering achievements, and with approximately a half of its members pursuing advanced studies in engineering science, is duty bound to study soaring physics and educate both the pilot community and the general public. It is in the vision of the latter that the three articles presented below are written. Therefore, the physical and mathematical methods used are not particularly advanced, but I have aimed to draw insightful conclusions based on simple analytical processes with the minimum compromise of rigour.
The starting point is Aerofoils and Wings: a glider flies in the same way that any other aeroplane flies. This article assumes little physical and mathematical knowledge and starts from the first principles. It introduces some basic concepts used extensively in fluid mechanics. It then discusses the working principles of aerofoils and wings, both in normal flight and in abnormal conditions (stall). This article hopefully helps the reader to understand that staying airborne does not require an engine.
The second article, Pressure, Atmosphere, and Instrumentation, examines the myths behind the instrument panel. It introduces the most essential thermodynamic and gas dynamic concepts before the discussion of instrumentation proceeds.
The third article, Polar, Performance, and Water Ballast, is an advanced one. It examines the way gliders trade height for speed and mathematically determines the most efficient ways of doing so depending on the conditions. It is with such understandings and the ability to predict height losses can a pilot take glider cross country. To follow the derivations, algebraic fluency and familiarity with some rudimentary calculus are needed, but the conclusions and insights are always presented in words.
To read the articles mentioned above, you need to visit another site (CUGC WiKi) which is a trusted site.