de Bothezat GB-5

by Wes Smith

Oct2013mysteryThe GB-5 known as THE BUG had twin co-axial rotors operating in opposite directions through gearing at both ends of the engine crankcase.

Georghe Bothezatu (Georgii Ivanovich Botezat–one source states his middle name was Aleksandrovich), was born in St. Petersburg, Russia on 7 June 1882. According to a Romanian source, he was born in N. Bassarabia, which was than under Russian occupation. The source goes on to state that he was born into a Romanian peasant family, with part of the family moving to Lasi, while the remainder stayed in Bessarabia. A differing account ( states that he was the son of Bessarabian landlords of Romanian extraction.

He graduated from school in Chrisian in 1902 and from 1905 to 1907 attended the Electro-Mechanical Institute in Belgium. In 1908 he graduated from Kharkov Polytechnik before pursuing graduate studies at Gottingen and Berlin. Later, after two years of study he earned his Ph.D. from the Universitaire de Sorbonne in Paris with a dissertation on aircraft stability. In 1911 he joined the faculty of St. Petersburg Polytechnical University to pursue advanced studies in stability. At St. Petersburg he worked with Aleksei Lebedev, Stephen Timoshenko and Alexander Vanderfleet, his area of interest shifting to propeller theory.

During 1914, Georgii Botezat became Director of the Polytechnical Institute at Novocherkassk. After the outbreak of the First World War, Botezat joined the technical commission of the Imperial Russian Air Service (IRAS), and published the standard bomb aiming tables for the IRAS in 1915. These tables are said to have had a far-reaching effect, as they are considered to have been the basis for some of the moon landing calculations made during the US luner program of the 1960s.

In 1916 he was appointed chief of the St. Petersburg airfield and managed the DEKA Stock Company, (Duflon, Konstantinovich and Co.) aircraft plant. The following year he is credited with the design of two single-engined aircraft. First proposed in the summer of 1915, only a single example of the military aircraft was built. It was a large three-place pusher biplane powered by a 220hp Renault. The nacelle carried a 37mm gun (presumably a Hotchkiss), and the empennage was similar to that of a Voisin. The first and only test of the two-bay biplane took place on 20 December 1917. However, it crashed due to the inexperience of the (unknown) pilot. Apparently there was a second aircraft, a twenty-place enclosed cabin pusher, again powered by a 220hp engine and incorporating “automatic stability” in the form of a gyroscope, possibly added to the control system (speculation on my part). It was built concurrently with the military machine and cost 26,000 rubles. Completed in October 1917 the aircraft suffered serious undercarriage damage on the first flight, and was abandoned. In any case, the company was taken over by the military, and with the revolution of 25 October little more was heard of either Botezat airplanes. It was apparently proposed to rebuild the military aircraft in 1919, but this was not done.

While Botezat was initially accepted by the Bolsheviks, he immigrated first to France, and then to America with the aid of the American Embassy in May of 1918. The following month, Botezat, now with the revised name of “George de Bothezat”, was hired by the National Advisory Committee for Aeronautics (NACA). He went on to lecture at the Massachusetts Institute of Technology (MIT), and Columbia University. In 1920 he published his first NACA Report (No. 28), titled “An Introduction to the Study of the Laws of Air Resistance on Aerofoils.” This was followed by a second paper “Airplane Performance as Influenced by the Use of a Super Charged Engine” (NACA Technical Notes No. 2). His third NACA paper “General Theory of the Steady Motion of an Airplane” (NACA Report No. 97) followed in 1921. de Bothezat was also active in the aeronautical press. His super charger article was reprinted in Aerial Age Weekly (V12 N6, Oct. 18, 1920, pp 174—179). Also in UK periodicals Aeronautics and Flight.

During 1921 he visited McCook Field in Dayton, Ohio where he became acquainted with Major (later Col.) Thurman H. Bane, Chief of the US Air Service Engineering Division. The exact sequence of events are unclear, but de Bothezat was subsequently retained to build a helicopter, apparently based on a US Air Service specification. In May of 1921 de Bothezat published another technical paper titled “The Actual State of the Helicopter Problem.” (Aerial Age Weekly V13 N11, May 23,1921, pp 247—249). Indeed, the idea of a man-carrying helicopter was far from new, and was not entirely without prior limited success. There was the second Newton-Williams Helicopter that had lifted from the ground at Emile Berliner’s farm outside Washington, D.C. in June of 1909. Abroad there were many other claims, some of which predate the Newton-Williams.

scan0003Upon retaining de Bothezat, he was appointed Deputy Chief of the Special Engineering Research Division. Construction of the helicopter was begun in July of 1921, without prior testing of models or the use of wind tunnels. The work was done by de Bothezat and Ivan Jerome in the hangars at McCook (later Wright Field), and relied solely on the theoretical calculation of de Bothezat. The machine was completed early December of 1922 and the first flight took place on 18 December with Maj. Bane at the controls thus making him the first US Army helicopter pilot. This flight was also 19 years and one day after the four flights of the 1903 Wright Flyer at Kitty Hawk. Although this flight was nothing more than a hover in ground effect, the maximum altitude being about 10 ft., and the duration lasting 1 min. 42 sec.with the machine drifting about 500 ft. from its original staring point. The flight was 43 seconds longer than the longest Wright flight on 17 December 1903. Nevertheless the helicopter was considered a success. The following day a second flight was made with de Bothezat at the controls, and this time carrying a passenger. The altitude reached was slightly higher and on 21 February 1923 the “Flying X” carried four people hanging from the four rotor outrigger booms for two full minutes,, reaching an altitude of about 15 ft.

As originally built, the de Bothezat helicopter had a complex set of controls. The four rotors, arranged in an “X” pattern had six-bladed rotors at each tip, each having an individual collective pitch control. Two small horizontal propellers were fitted to provide some horizontal thrust, The maximum distance from rotor tip-to-tip was about 65 ft., and the overall height was approximately 10 ft. The two-spar rotor blades when fitted to the central hub had a maximum diameter of about 23 ft., each blade having approximately 37.5 sq. ft. of area, the total disc area being 2,204.66 sq. ft. The empty weight of the de Bothezat was 3,306 lbs., the initial take-off weight being 3,600 lbs., then increasing to 3,693 lbs. and finally to 3,803 lbs. The maximum weight lifted on any flight was 4,851 lbs. The transmission system of the machine was highly complex, and was constructed by Allison. Unsurprising, de Bothezat was a difficult person to work with. For years stories of his secretive behavior and tantrums have been repeated in various forms. Yet, a plaque in the corner of the Allison library commemorates his accomplishments. He obtained two US patents on his 1921-22 helicopter, No. 1,573,228 (1923), and 1,749,471 (1924). Interestingly the “X” configuration has been revived at least twice. First by the Germans and second by today’s miniature remotely piloted vehicles. The reason being the high stability of the design.

As originally constructed, the “Flying Octopus” was fitted with the comparatively rare LeRhone Model R. This engine was developed during the first World War, and the nine-cylinder air-cooled rotary radial developed 170hp (normal) at 1,360 rpm, with a maximum output of 180hp, thus accounting for the two figures seen in different sources. The high compression ratio of 5.65:1 was comparatively new as were aluminum pistons, a revised induction system and auxiliary cooling intakes on the front of the crankcase. At a later date the LeRhone was replaced with a 230hp Bentley R.R.2. Initially rated at 200hp the Bentley could actually produce 230 to 250hp at 1,300 rpm. The gear reduction system of the de Bothezat lowered the maximum multi-rotor rpm to 70—90 rpm, roughly half of modern helicopters.

After about 100 test flights little had been accomplished despite the ability to hover in an extremely stable mode. After having spent $200,000.00 since 1921, the cash strapped USAS ordered an end to the tests, and this historic machine was scrapped. During the flight tests, a maximum altitude of about 30 ft. had been obtained, with a maximum horizontal speed of about 31 mph. De Bothezat had been one of the first to address the problem of auto-rotation in his Aerial Age article. This, along with the dynamics of the rotor blades in flight make it something of a seminal work. However, de Bothezat was not the first to understand the concept of a thrust component in lift. That honor belongs to Wilbur Wright, and was discovered by this author in 1998 while conducting research at the Library of Congress. Subsequently Juan de La Cierva would take this idea to create the C-4 autogiro. First tested on 9 January 1923 with Lt. Alejandro Gomez Spencer as pilot. In February 1923 de Bothezat sent a photo of his helicopter in flight to Thomas Alva Edison, one of the prophets of rotary winged flight. Edison responded: “You have certainly made a great advance, in fact, as far as I know, the first successful helicopter.” Two final points of interest, according to a 1943 Mechanix Illustrated article by Boris Sergievsky (as told to George Daniels), sand was poured into the crankcase of one of the engines. Even more disturbing, de Bothezat was mailed a very cleverly disguised poisonous snake, which he apparently avoided. Just who, and why this was done (if true), remains a mystery.

With the end of the flights of de Bothezat’s helicopter, he returned to New York in 1926 to establish the de Bothezat Impeller Company, Inc. He wrote extensively on various subjects ranging from flight dynamics to the economic causes of the Great Depression. He even did special effects for the movie “The Love of Sunya” by Dudley Murphy in 1927. In 1936 he wrote the book “Back to Newton” in which he declared Albert Einstein’s work to be invalid. Einstein personally defended his theories in a debate at Princeton, refuting de Bothezat’s claims that Einstein’s space-time theories were in error. Inadvertently an anti-semitic audience member spoke to de Bothezat after the encounter and may have potentially set the stage for the Nazi rejection of “Jewish physics” thus possibly costing Nazi Germany the opportunity to construct a nuclear weapon in advance of the United States. (A lack of highly enriched uranium and heavy water undoubtedly made construction impossible. Nevertheless, there is an unconfirmed story that a dirty bomb, or radiologic device was actually tested at the end of the war).
After World War II Prof. Werner Heisenberg explained precisely how to build a working atomic bomb in a secretly recorded discussion. His failure to act on this knowledge has never been fully explained. Could de Bothezat inadvertently caused Nazi scientists to reject Einstein’s equations in the same way Stalin negatively influenced genetic studies in the Soviet Union?

de Bothezat married in 1926 and after the debacle at Princeton 10 years later, he established the “Air Screw Research Syndicate.” The Axial Impeller Company continued to thrive, the devices being fitted to USN cruisers for ventilation. A year later de Bothezat renamed the company The Helicopter Corporation of America. He hired Boris Sergievsky a colorful World War I Russian ace who had previously flown for Sikorsky until the orders for flying boats began to decline. Sergievsky was born near St. Petersburg at Gatchina, site of one of the most prominent airfields in Russia. Years later, while attending the Polytechnik College at Kiev, Sergievsky became acquainted with Igor Ivanovick Sikorsky, and during his second year there an aviation club was formed, in which he took great interest. While still at school Sergievsky married and had a son. He then entered mandatory military service, becoming an officer before returning to his studies. Following graduation he was assigned to the 129th Bessarabian Infantry Regiment as a Paporchik (Ensign). He was called to arms in early August 1914 and soon saw heavy combat. Kaptain Petr Nesterov landed near his regimental headquarters and used some colorful language after having been fired upon by Russian troops.

Sergievsky’s military service continued unabated and was awarded the Order of St. George Fourth Class and earned a promotion to Podporuchik (2nd Lt.). He suffered a serious head wound which caused temporary blindness in his left eye. This was corrected by surgery and he continued fighting throughout 1915. He was again severely wounded in his right ankle, and during while recouperating heard that volunteers were being asked to serve in the Imperial Russian Air Service. On 15 March 1916 he was assigned as officer/observer with the 25th Corps., assigned to Voisin Type LA pushers. He was promoted to Poruchik (Lt.) and by mid-July had flown 15 missions, with 26 hours in the air. On 20 June his aircraft was attacked and the pilot severely injured. Sergievsky managed to land the heavily damaged Voisin.

Sergievsky served throughout the Brusillov offensive of 1916 before finally being sent to flight school. By 1 June 1917 he was assigned to the 2nd fighter detachment at Radzivilov. The squadron consisted of nine pilots, flying ten airplanes of six different types. He was assigned a Nieuport 21 to fly. Soon he encountered an Imperial German Air Service Roland D.II and with the end of his ammunition was able to hit the German’s engine causing a forced landing. Requisitioning a car, Sergievsky arrived at the trenches to learn that the German aviator had fled, having thrown off his heavy flying clothes in order to outrun his Russian pursuers. Sergievsky was promoted to Stabs-Kaptain 26 October 1917. His final aerial battle took place when he and two other pilots shot down a Brandenburg D.I over Smolino. After the Russian armistice 15 December, Sergievsky returned to Kiev, to offer his services to the White Army.

He next worked for the Inter-Allied Commission for re-evacuation of prisoners of war at Berlin. He and his wife had fled Kiev, leaving behind his son and mother. They next went to England where Sergievsky served as instructor at the Netheravon Flying School. In October 1919, he and his wife returned to Russia to fight for the White Army flying the R.E.8 in Estonia. With the collapse of the White Army, Sergievsky and his wife retreated to Poland where their former allies disarmed them. While working at an American YMCA helping ex-POWs, Sergievsky realized they could never return to Russia, so they headed for America.

He first worked as a manual laborer on the Holland Tunnel before becoming re-acquainted with Igor Sikorsky where he worked as a test pilot. Eventually he took a job with the Andean National Corporation in South America which was building a pipeline. In 1927 Sergievsky was reunited with his mother and son after nearly 10 years and was fortunate in obtaining permission for them to immigrate to the United States. He learned that his two brothers had been killed by Bolsheviks. He rejoined Sikorsky as a test pilot in 1932 and also served as chief pilot for the Martin and Osa Johnson African Expedition flying S-38 and S-39 amphibians. In 1933 he flew passengers in an S-38 at the Chicago World’s Fair. One particularly interesting passenger was a 95 year old Confederate Civil war veteran who had never experienced the magic of flight. He was enthralled following the ride!

Sergievsky’s next job with Sikorsky was flying the Prince of Wales on a South American tour. He delivered a twin engined Sikorski amphibian to Hollywood for Howard Hughes, and is known to have flown with Charles Lindbergh. He also set many world records for seaplanes and amphibians while working for Sikorsky.

Between 1938 and 1944 he served as test pilot and vice-president for de Bothezat’s Helicopter Corporation of America, later in 1944 joining the Office of Strategic Services.

scan0002de Bothezat had designed a co-axial helicopter known as the GB-3-4 during the 1930s. It was a new concept. It incorporated twin co-axial rotors with the engine placed between the rotors driving them in opposite directions through gearing at both ends of the crankshaft. Corporation headquarters were located at 31-45 Davis Street on Long Island, and as was the case with most companies during these depression days was always short of funds to carry out operations.

Powered with an 85hp Franklin (possibility a 4AC-199-D2, four cylinder, air-cooled, horizontally opposed engine) “The Bug” as the GB-5 was known as, was first test flown by Sergievsky on 9 May 1940. Unfortunately Dr. de Bothezat had passed away at a Boston hospital on 1 February 1940 of “an old and untreated illness” at age 58. The GB-5 was tested in various configurations, but de Bothezat’s successor, Watson M. Washburn was unequal to the task as set forth by de Bothezat. The tests were moved to Roosevelt Field where they continued into the summer of 1940. The aircraft was unable to climb higher that 5 ft. A crash put an end to the GB-5, and very little is known about its eventual disposal.
The rotor diameter was approximately 28ft. And the total weight was 606.375 lbs. An article on the internet doubts that the helicopter could have auto-rotated. Certainly this seems quite likely.

Before de Bothezat passed away he came up with the concept of the “Heli-Hop” a one man helicopter intended for use by the military. Two designations are used in Sergievsky’s 1943 article, the GV-2 and GV-5. Romanian Aeronautical Constructions does show two different versions, however, the unexplained GB-3-4 test rig is another possibility. The Wikipedia article seems to imply that the GB-3-4 was the SV-2, and the
GB-5 “The Bug” was the SV-5. In 1948 the de Bothezat Impeller Company, Inc., was involved in a lawsuit.

An air charter service operating out of New York City was started by Boris Sergievsky after World War II flying a Grumman Mallard amphibian. He died at age 83 having flown for 53 years.


The Otterbein Press, 1921, pp 80-81 and 303-304

Antoniu, Dan and George Cicos. ROMANIAN AERONAUTICAL CONSTRUCTIONS. Craiova, Romania. Avi SRL Cariova, 2013, pp 86-91

Mountain View, California, Flying Machine Press, 1995, pp 218-227

J.B. Lippincot Co, 1969, pp 20-24 and 35-48


Maslov, Mikhail RUSSIAN AEROPLANES 1914—1918 Old Saybrook, Conneticut
Icarus Aviation Publications, 2002, p 153

University of California Press, 1998

Young, Warren R. and the editors of Time-Life Books THE HELICOPTERS Alexandria, Virginia
Time-Life Books, 1982, pp 42-61


Mechanix Illustrated, September 1943, pp 48-49 and 148-149