Mr Chairman, Ladies and Gentlemen,

It is a pleasure to introduce our lecturer this afternoon Although as a fellow-member he has remained modestly in the background until now, DR SISSINGH is known internationally as a leading aerodynamicist in the rotary-wing field

Perhaps his first notable contribution was a paper published in “Luftfahrtforschung” exactly 10 years ago, this was later translated into English and became an N A C A Technical Memorandum In his calculations DR SISSINGH was not content with a rough estimate of the average values of drag coefficient and induced velocity but took into account their distribution along the blade This unwillingness to make empirical assumptions merely for the sake of mathematical simplicity is typical of his subsequent work

For a number of years DR SISSINGH has devoted his attention to helicopter stability and has written extensively on this important problem His investigations were conducted first at the Flettner Company near Berlin, then at the well-known Kaiser Wilhelm Institut at Gottingen, and recently at the Royal Aircraft Establishment