Göttinger Monograph N: German Research and Development on Rotary-Wing Aircraft (1939-1945) Edited by Berend G. van der Wall, German Aerospace Center (DLR) Book Review by Walter G.O. Sonneborn fter the end of World War II, the Origin of the AVA Monograph N; Short maximum takeoff weight of 4,300 kg British Ministry of Supply — Biographies; Index; Supporting Materials (9,480 lb) and a Vh of 210 km/hr (113 kt), Ainterested in German aeronautical This 245 page book is a must for and achieved a ceiling height of 7,100 m technology developed during war rotorcraft history buffs as it gives a (23,000+ ft). — ordered the German aeronautical comprehensive view of the efforts of Configurations from pure autogyros, research establishments in Göttingen the German rotorcraft pioneers during single rotor helicopters (some with and Braunschweig to summarize their the years from 1939 through 1945. Their transition to autogyro flight for high research. The Göttingen Monographs work was contemporaneous with that of speed), intermeshing rotors, and side- About Advancements of the German Ludwig Prandtl (1875-1953), the founder by-side configurations were developed. Aeronautical Research Since 1939 of modern aerodynamics, working at the With today’s renewed interest in comprised several volumes. Volume University of Göttingen and founder of compound helicopters, the Flettner N, German Research and Development the famous AVA (Aerodynamic Research Fl-185 helicopter deserves special on Rotary-Wing Aircraft – written by Establishment). mentioning, as it used two propellers Gerhard Sissingh and O.H. Nagel and However, this book should also for both automatically adjusted torque edited by Albert Betz (as in the Betz be of great interest to any student reaction as well as auxiliary thrust. This Limit for wind turbines) — was the only or practitioner of the rotary-wing arrangement is very similar to today’s volume not translated in its entirety sciences, as a reminder of how much experimental Airbus Helicopters X3. from German into English. This volume can be accomplished within a short However, the Fl-185 did not yet feature N was rediscovered some five years time and without computers, using wings. Other innovations of the industry ago by Prof. Berend G. van der Wall at slide rules and mechanical calculators. included automatic switching between the German Aerospace Center (DLR) In fact, the reviewer believes that this helicopter and autogyro mode, or in Braunschweig. Prof. van der Wall “lack” of computers resulted in a deep to complete autorotation mode, as translated and edited the material, understanding and clear presentation of well as landing on a flexible ship- which has now been published in the the physics and other issues involved. mounted platform with a rigid landing English language by the American Readers interested mostly in gear to save the weight of oleos. The Institute of Aeronautics and Astronautics hardware and testing will enjoy the configurations, test developments and (AIAA). initial two sections written by O.H. Nagel, practical operational achievements, CONTENTS: Introduction; Design of which describe all important rotorcraft as well as accidents of the above the Rotors; Description of Developed developed during the period, to include mentioned rotorcraft are described in and Planned Vehicles; Testing and the Fw-61, often considered the first Nagel’s sections. Accidents; Extension of Glauert- practical, functional helicopter, first Regarding development risk, Nagel Lock-Wheatley’s Rotary-Wing Theory; flown in 1936; the Fa-223, Fa-230, Fa-330, remarks: “Because the development Dynamic Rotor Problems; Performance Fa-284 (not flown), Fl-184, Fl-185, Fl-265, initially had to proceed on an empirical Investigations; Flying Qualities; Various Fl-282, Fl-282B, Fl-339 (not flown), and basis without noteworthy support of Other Topics; Prospects; Bibliography; others. The Fa-223, Germany’s largest theory and without larger scientific Modifications to the Original Text; helicopter flown during the War, had a research, every first takeoff of a new 54 VERTIFLITE November/December 2015 or modified model had the possibility of a surprise. This Flettner, Sissingh, Hohenemser and Doblhoff all continued improved only after the creation of a central helicopter working after WWII in the rotary-wing aircraft field in the research establishment in the Aerodynamic Research United States of America in various capacities at Lockheed, Establishment (AVA) Göttingen in 1943.” McDonnell, Kellett, Vertol and Hiller, with decided influence Sissingh’s chapters, comprising the main on the products under development at the time, particularly body of the Monograph, deal with all areas advanced configurations, such as the Lockheed Cheyenne of rotary-wing theory under development and the McDonnell XV-1 compound helicopters. Betz, at the time. The comprehensive Just and Focke remained in Europe contributing nomenclature section is most helpful significantly to the emerging European in reading these analytical sections rotorcraft industry, including the of the book; notations will generally education of the next be familiar to a reader living in the generation of US environment, while the use of rotary-wing the metric system may require engineers. some mental adjustment. (While The this reviewer contributed reviewer also to some translational and wants to take technical aspects, it should this occasion to be mentioned that some extend his gratitude Germanic expressions were posthumously to deliberately retained to his first mentor, Prof. preserve the flavor of the Walter Just. time. For example, rotor blades are frequently Title: Göttinger referred to as “wings.”) Monograph N: German The Germans Research and Development started with Glauert- on Rotary-Wing Aircraft Lock-Wheatley (1939–1945) (NACA) developed Editor: Dr.-Ing. Berend G. van theories and der Wall, German Aerospace extended them. Center (DLR), Institute of NACA on the Flight Systems, Helicopters, other hand Braunschweig, Germany immediately published Publisher: American Institute of some of Aeronautics & Astronautics (AIAA) Sissingh’s Series: Library of Flight early work — Format: 312 pages, Hardcover or PDF as long Publication: April 17, 2015 as it was available — in ISBN-13: 978-1624102721 1939 as NACA TM 921. Ordering: Books or pdfs can be ordered from The chapters on aeromechanics, AIAA at http://arc.aiaa.org/series/4.lof performance, flying qualities and (prices range from $35.95 to $49.95), special topics comprise 237 formulas and 62 Amazon.com and other resellers. illustrations, filling 90 fascinating pages. The accomplishments of mainly the companies Focke-Achgelis in Bremen and Anton Flettner in Berlin About the Reviewer led to practical rotary-wing aircraft, based on a practical understanding of the aeromechanical theories, coupled with alter Sonneborn began his career in 1962 in mastering materials and manufacturing technology suitable Germany under Prof. Walter Just. He worked at Bell for serial production. WHelicopter from 1965 until his retirement as a Vice A most valuable addition to the mostly technically- President in 2002. Since then he has been consulting for oriented original monograph is the appendix containing several aerospace companies and government agencies. short biographies — collected by Prof. van der Wall — of He is a recipient of the AHS Klemin Award, the Nikolsky the key players involved, namely Albert Betz, Friedrich L. Lectureship and an Honorary Fellowship. von Doblhoff, Anton Flettner, Henrich C.J. Focke, Kurt H. Hohenemser, Walter Just and Gerhard J. Sissingh. Vol. 61, No. 6 55.