Bramwell's Helicopter Dynamics


At the time of publication of the first edition of the book in 1976, Bramwell’s Helicopter Dynamics was a unique addition to the fundamental knowledge of dynamics of rotorcraft due to its coverage in a single volume of subjects ranging from aerodynamics, through flight dynamics to vibrational dynamics and aeroelasticity. It proved to be popular, and the first edition sold out relatively quickly. Unfortunately, before the book could be revised with a view to producing a second edition, Bram (as he was known to his friends and colleagues) succumbed to a short illness and died.

As well as leaving a sudden space in the helicopter world, his death left the publishers

with their desire for further editions unfulfilled. Following an approach from the publishers, the present authors agreed, with considerable trepidation, to undertake

the task of producing a second edition.
Indeed, being asked was an honour, particularly so for one of us (GD), since we had been colleagues together at City University for a short period of two years. However, although it may be one thing to produce a book from one’s own lecture notes and published papers, it is entirely a different proposition to do the same when the original material is not your own, as we were to discover. It was necessary to try to understand why Bram’s book was so popular with the helicopter fraternity, in order that any revisions should not destroy any of the vital qualities in this regard.

One of the characteristics that we felt endeared the book to its followers was the way explanations of what are complicated phenomena were established from fundamental

laws and simple assumptions. Theoretical expressions were developed from the basic mathematics in a straightforward and measured style that was particular to Bram’s way of thinking and writing. We positively wished and endeavoured to retain his inimitable qualities and characteristics.

Long sections of the book are analytical, starting from fundamental principles, and do not change significantly in the course of time; however, we have tried to eradicate errors, printer’s and otherwise, and improve explanations where considered necessary. There are also many sections that are largely descriptive, and, over the space of 25 years since the first edition, these had tended to become out of date, both in terms of the state-of-the-art and supporting references; thus, these have been updated.

Opportunities, too, have been taken to expand the treatment of, and to include additional

information in, the vibrational dynamics area, with both the additional and updated content introduced, hopefully, in such a way as to be compatible with Bram’s style.

Another change which has taken place in the past quarter century is the now greater familiarity of the users of books such as this one with matrices and vectors. Hence, Chapter 1 of the first edition, which was aimed at introducing and explaining the necessary associated matrix and vector operations, has disappeared from the second edition. Also, some rather fundamental fluid dynamics that also appeared in this chapter was considered unnecessary in view of the material being readily available in undergraduate textbooks. What remained from the original Chapter 1 that was thought still necessary now appears in the Appendix. Readers familiar with the first edition will notice the inclusion of a notation list in the present edition. This became an essential item in re-editing the book, because there were many instances in the first edition of repeated symbols for different parameters, and different symbols for the same parameters, due to the fact that the much of the material in the original book was based on various technical papers published at different times. As far as has been possible, the notation has now been made consistent throughout all chapters; this has resulted in some of the least used symbols being changed.

Apart from the removal of the elementary material in the original Chapter 1, the overall structure of the book has not changed to any great degree. The order of the chapters is as before, although there has been some re-titling and compression of two chapters into one. Some of the sections in the last three chapters have been rearranged to provide a more natural development.

Since publication of the first edition, there have appeared in the market-place several excellent scientific textbooks on rotorcraft which cover some of the content of Bram’s book to a far greater depth and degree of specialisation, and also other texts which are aimed at a broad coverage but at a lower academic level. However, the comprehensive nature of the subject matter dealt with in this volume should continue to appeal to those helicopter engineers who require a reasonably in-depth and authoritative text covering a wide range of topics.

 

Sherborne David Balmford

Kew George Done

2001

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