Bell XP-39 Airacobra 38-326 in the NACA Full Scale Wind Tunnel at Langley Field, Virginia, 9 August 1939. The man at the base of the supports shows scale. (NASA)
9 August 1939: After General Henry H. Arnold had ordered that the prototype Bell Aircraft Corporation XP-39 Airacobra be evaluated in the National Advisory Committee for Aeronautics (NACA) Full-Scale Tunnel at the Langley Memorial Aeronautics Laboratory, Langley Field, Virginia, it was flown there from Wright Field. It was hoped that aerodynamic improvements would allow the prototype to exceed 400 miles per hour (644 kilometers per hour).
NACA engineers placed the full-size airplane inside the large wind tunnel for testing. A number of specific areas for aerodynamic improvement were found. After those changes were made by Bell, the XP-39’s top speed had improved by 16%.
Bell XP-39 Airacobra 38-326 in the NACA Langley Memorial Aeronautical Laboratory Full-Scale Wind Tunnel, Langley Field, Virginia, 9 August 1939. The fuselage has had all protrusions removed. Right profile. (National Aeronautics and Space Administration NACA 18423)
The Bell XP-39 Airacobra was a single-place, single-engine prototype fighter with a low wing and retractable tricycle landing gears. The airplane was primarily built of aluminum, though control surfaces were fabric covered.
As originally built, the XP-39 was 28 feet, 8 inches (8.738 meters) long with a wingspan of 35 feet, 10 inches (10.922 meters). The prototype had an empty weight of 3,995 pounds (1,812 kilograms) and gross weight of 5,550 pounds (2,517 kilograms). Changes recommended by NACA resulted in a recontoured canopy, lengthened the airplane to 29 feet, 9 inches (9.068 meters) and reduced the wing span to 34 feet, 0 inches (10.362 meters). Its empty weight increased to 4,530 pounds (2,055 kilograms) and gross weight to 5,834 pounds (2,646 kilograms).
Bell XP-39 Airacobra 38-326 in the NACA wind tunnel at Langley Field. The man at the base of the supports shows scale. (NASA)
The XP-39 was unarmed, but it had been designed around the American Armament Corporation T9 37 mm autocannon, later designated Gun, Automatic, 37 mm, M4 (Aircraft). The cannon and ammunition were in the forward fuselage, above the engine driveshaft. The gun fired through the reduction gear box and propeller hub.
The XP-39 was originally powered by a liquid-cooled, turbosupercharged and supercharged 1,710.597-cubic-inch-displacement (28.032 liter) Allison Engineering Co. V-1710-E2 (V-1710-17), a single overhead cam (SOHC) 60° V-12 engine with a compression ratio of 6.65:1. The V-1710-17 had a Maximum Continuous Power rating of 1,000 horsepower at 2,600 r.p.m. at 25,000 feet (7,620 meters), and Takeoff/Military Power rating of 1,150 horsepower at 3,000 r.p.m. at 25,000 feet, burning 91 octane gasoline. The engine was installed in an unusual configuration behind the cockpit, with a two-piece drive shaft passing under the cockpit and turning the three-bladed Curtiss Electric constant-speed propeller through a remotely-mounted 1.8:1 gear reduction gear box. The V-1710-17 was 16 feet, 1.79 inches (4.922 meters) long, including the drive shaft and remote gear box. It was 2 feet, 11.45 inches (0.900 meters) high, 2 feet, 5.28 inches (0.744 meters) wide and weighed 1,350 pounds (612 kilograms).
Bell XP-39B prototype, s/n 38-326, at Bell Aircraft Co., Buffalo, New York
Army Air Corps strategy changed the role of the P-39 from a high-altitude interceptor to a low-altitude tactical strike fighter. The original turbocharged V-1710-17 was replaced with a V-1710-37 (V-1710-E5) engine. The turbosupercharger had been removed, which reduced the airplane’s power at altitudes above 15,000 feet (4,572 meters). The V-1710-37 had a maximum power of 1,090 horsepower at 3,000 r.p.m. at 13,300 feet (4,054 meters). With the NACA-recommended aerodynamic changes and the new engine, the prototype Airacobra was redesignated XP-39B.
A Bell P-39 Airacobra fires all of its guns at night. (U.S. Air Force)
9 August 1896: Pioneering aviator Karl Wilhelm Otto Lilienthal was fatally injured when his glider stalled on his fourth flight of the day.
Flying at the Rhinow Hills, near Stölln in what is now northern Germany, he had been gliding as far as 820 feet (250 meters). The weather was windy. As he sailed off the slope, his glider suddenly pitched up. Lilienthal tried to correct the attitude by swinging back and fourth, but he had lost lift and the glider fell about 50 feet (15 meters) to the ground.
Seriously injured, he was taken to a doctor who determined that he had fractured the third cervical vertebra. He was then transported by train to Berlin where a very successful surgeon, Professor Ernst von Bergman, had a clinic.
Lilienthal died about 36 hours after his injury, 10 August 1896. Among his last words were, “Sacrifices must be made.”
His discoveries in controlled flight inspired the Wright Brothers to pursue aviation. He is considered to be one of the most influential of the early pioneers of flight, and is known as The Father of Flight.
Photo prise par l’observatoire de Meudon.par l’astronome Jules Janssen.
9 August 1884: At the parade grounds at Chalais-Meudon, a town on the banks of the Seine near Paris, France, engineers Charles Renard and Arthur Constantin Krebs made the first controllable free flight when they piloted their airship, La France, over an approximately 4¾ mile (7.6 kilometers) course and returned to their starting point. The airship completed the circuit in 20 minutes at an average speed of 15.75 feet per second (10.74 miles per hour, or 17.28 kilometers per hour).
Track of La France, 9 August 1884
Charles Renard later said,
“As soon as we had reached the top of the wooden plateaus which surrounded the valley of Chalais we started the screw, and had the satisfaction off seeing the balloon immediately obey it, and readily follow ever turn of the rudder. We felt we were absolutely masters of our own movements, and that we could traverse the atmosphere in any direction as easily as a steam launch could make its evolutions on a calm lake. After having accomplished our purpose we turned our head toward the point of departure, and we soon saw it approaching us. The walls of the park of Chalais were passed anew, and our landing appeared at our feet about 1,00 feet below the car. The screw was then slowed down, and at a pull of the safety valve started the descent, during which, by means of the propeller and rudder, the balloon was maintained directly over the point where our assistants awaited us. Everything occurred according to our plan, and the car was soon resting quietly upon the lawn from which we had started.”
—The Practical Engineer, Volume 9, Number 371, Friday, 6 April 1894, Page 266, Column 1
From 9 August 1884 to 23 September 1885, La France made seven flights and was able to return to its starting point five times. On its final flight, it reached an average speed of 21.33 feet per second (14.54 miles per hour, or 23.40 kilometers per hour).
Plan de l’enclos de l’étang de Chalais et de ses dépendances. (Bibliothèque nationale de France)
La France was a powered, steerable, gas balloon, approximately 167 feet long (50.9 meters) and 27½ feet (8.4 meters) in diameter. Buoyancy was provided by 65,000 cubic feet (1,841 cubic meters) of hydrogen.
Under the balloon envelope hung a 108 foot (32.9 meter) long gondola made of bamboo and covered with silk. This was where the airmen and any passengers, the 8½ horsepower (6.25 kilowatts) electric motor and a chromium chloride storage battery were placed. The motor weighed 220.5 pounds (100 kilograms), and the battery, 580 pounds (263 kilograms.)
At the forward end of the gondola was a four-bladed wooden propeller with a 23-foot (7.0 meters) diameter and 28-foot (2.4 meters) pitch, providing thrust to drive the airship. The propeller was driven by a 49 foot (14.9 meters) drive shaft. On the 9 August flight, the propeller turned 42 r.p.m. On later flights, this was increased to a maximum 57 r.p.m.
La France was controlled by a rudder and elevator. A sliding weight allowed for changes in the center of gravity.
Drawing of le dirigeable ballon La France de Charles Renard et Arthur Krebs.
La France was designed and built by Captain Paul Renard, Captain Charles Renard and Captain Arthur Constantin Krebs, all officers of the French Armée de Terre Corps du Génie (Corps of Engineers) at the central military aeronautics establishment at Chalais-Meudon.
Charles Renard
Charles Renard was born at Damblain, Viosges, France, 23 November 1847. In 1873, he had developed an unmanned glider which was controlled by a pendulum device linked to its control surfaces. The glider was flown from a tower at Arras.
Renard also developed the powered Renard Road Train, in which the trailers were powered by drive shafts from the forward power car, and each car was steered through a system of linkages attached to the car ahead of it. He also developed the concept of preferred numbers. (ISO 3)¹
Charles Renard remained in charge of the aeronautical establishment at Chalais-Meudon until his death. He committed suicide, 13 April 1905.
Arthur Constantin Krebs was born 16 November 1850 at Vesoul, France.
Arthur Constantin Krebs
Krebs was a prolific inventor. Following his work with La France, he completed the development of Gymnote (Q1), the world’s first all-electric submarine. His work on automobiles was extensive. He developed the concept of the front engine/rear wheel drive (Systeme Panhard); engine balancing; caster in the steering and suspension system, which allowed the steering wheels to self-center; the steering wheel; shock absorbers; four-wheel drive and four-wheel steering, etc. He invented the electric brake dynomometer which is used to measure power output of engines.
Arthur Krebs died 22 March 1935.
Airship La France at Hangar Y, Chalais-Meudon, circa 1885. (NASM)
¹ “Preferred numbers were first utilized in France at the end of the nineteenth century. From 1877 to 1879, Captain Charles Renard, an officer in the engineer corps, made a rational study of the elements necessary in the construction of lighter-than-air aircraft. He computed the specifications for cotton rope according to a grading system, such that this element could be produced in advance without prejudice to the installations where such rope was subsequently to be utilized. Recognizing the advantage to be derived from the geometrical progression, he adopted, as a basis, a rope having a mass of a grams per metre, and as a grading system, a rule that would yield a tenth multiple of the value a after every fifth step of the series. . . .”
—ISO 17:1973, International Organization for Standardization
Mikoyan-Gurevich Ye-50/3 (Mikoyan Design Bureau via The Corner of the Sky)Nikolay Arkadevich Korovin
8 August 1957: At Ramenskoye Airfield, Moscow, Russia, senior test pilot Lieutenant Colonel Nikolay Arkadevich Korovin (Коровин Николай Аркадьевич) was scheduled to take an experimental prototype interceptor to an altitude of 20,000 meters (65,617 feet).
The airplane was the Mikoyan-Gurevich Ye-50/3 (also known as the E-50/3). It was powered by an afterburning turbojet engine and a liquid-fueled rocket engine. This was the third prototype of the series.
The three Ye-50 prototypes were variants of the MiG 21. They were developed from the earlier MiG Ye-2, with a rocket engine installed. This was not merely a booster engine, but the aircraft carried sufficient fuel for as much as 20 minutes of rocket-assisted flight. A planned production interceptor, the Ye-50A, was designated MiG 23U. Only one of these was built.
Mikoyan-Gurevich Ye-50/3 (Mikoyan Design Bureau via The Corner of the Sky)
The Ye-50/3 differed from Ye-50/2 with an increased fuel capacity and extended air intake with sharp leading edge. The Ye-50/3 was 4.85 meters (48.72 feet) long with a wingspan of 8.11 meters (21.61 feet). The aircraft had an empty weight of 5,920 kilograms (13,051 pounds), and maximum takeoff weight of 8,500 kilograms (18,739 pounds).
The Ye-50/3 was powered by an A.A. Mikulin AM-9E afterburning turbojet engine rated at 3,800 kilograms force ( pounds thrust) and a liquid-fueled Dushkin S-155 rocket engine. The S-155 used a hypergolic mixture of nitric acid and kerosene as fuel. It produced 1,300 kgf (2,866 pounds of thrust).
Mikoyan-Gurevich Ye-50/3 (Mikoyan Design Bureau via The Corner of the Sky)
The Ye-50/3 had been completed in April 1957. Prior to 8 August, Ye-50/3 had made 10 test flights, 6 of which successfully used the rocket engine. It had a maximum speed of 2,460 kilometers per hour (1,529 miles per hour), or Mach 2.33. The service ceiling was 23,000 meters (75,460 feet. Its range was 475 kilometers (295 miles).
The Ye-50/3 was the only one of the three prototypes to be armed. It carried two Nudelman-Rikhter NR-30 30 mm autocannon.
Mikoyan-Gurevich Ye-50/3 (Mikoyan Design Bureau via The Corner of the Sky)
Ramenskoye Airfield was very busy that day. Colonel Korovin’s launch was delayed by traffic on the runway. Finally, he took of at 12:50 p.m. and accelerated into a climb.
At 1:01 p.m., Colonel Korovin radioed that the aircraft was in a spin. 30 seconds later, he called that he was ejecting.
The Ye-50/3 crashed near the village of Radovitsy, approximately 100 kilometers (62 miles) southeast of Ramenskoye. The body of Colonel Korovin was located about 150 meters (164 yards) from the crash site, still in his ejection seat. The parachute had not opened, and the test pilot had been killed on impact.
The accident investigation found that during the delay to takeoff, the liquid oxidizer accumulated in the combustion chamber. This caught fire as the prototype took off. The rocket engine’s turbopump exploded. The explosion damaged the flight control system and the prototype caught fire. The fire burned away a portion of the airplane’s vertical fin. When it entered a spin, Colonel Korovin was unable to recover. It was found that he had removed his gloves and tried to manually pull the ejection seat parachute release cable, but to no avail.
On 9 September 1957, Lieutenant Colonel Korovin was posthumously named a Hero of the Soviet Union.
Cockpit of Mikoyan-Gurevich Ye-50/3. (Mikoyan Design Bureau via The Corner of the Sky)Коровин Николай Аркадьевич
Nikolay Arkadevich Korovin was born 7 May 1920 at the village of Galanovo in the Votsk Autonomous Oblast (now, the Udmurt Republic). His family were peasants who worked on a collective farm. Korovin completed six grades of formal education.
In 1938 Korovin joined the Red Army. He received further education at a military school in Perm, a city in Russia near the Ural Mountains, graduating in 1939. The following year, he completed pilot training at the Stalingrad Military Aviation School.
From 1941 through 1944, Korovin served as a pilot instructor at Chkalovskaya (now Orenburg, Kazakhstan). In March 1944, he was assigned to combat operations, first with the 91st Guards Aviation Regiment (Ground Attack), and then the 92nd Guards. He fought on the second Ukrainian Front, and in Hungary, Checkoslavakia and Austria. He flew 66 combat missions in the Ilyushin Il-2 Штурмовик (Šturmovík) during the Great Patriotic War.
The Ilyushin Il-2 Šturmovík was the most-produced aircraft of the Second World War. (NASM)
Korovin remained in the Soviet Air Force following the War. He graduated from a senior officers tactical school at Taganrog, Rostov Oblast, in 1950, and then, in 1951, became a senior test pilot for the State Red Banner Scientific-Testing Institute for the Air Force (GK NII VVS). In 1955, Korovin flew government tests of the MiG 19.
During his military career, Lieutenant Colonel Nikolay Arkadevich Korovin was awarded the Order of Lenin, Order of the Red Banner, Order of the Patriotic War 1st Degree, and Order of the Red Star (two awards). His remains were buried at the military cemetery at Chkalovskaya.
8 August 1955: While being carried aloft by a Boeing B-29 Superfortress, the Bell X-1A was being readied for it’s next high-altitude supersonic flight by NACA test pilot Joe Walker. During the countdown, an internal explosion occurred. Walker was not injured and was able to get out. The X-1A was jettisoned. It crashed onto the desert floor and was destroyed.
A number of similar explosions had occurred in the X-1D, X-1-3 and the X-2. Several aircraft had been damaged or destroyed, and Bell Aircraft test pilot Skip Ziegler was killed when an X-2 exploded during a captive flight. A flight engineer aboard the B-29 mothership was also killed. The B-29 was able to land but was so heavily damaged that it never flew again.
Debris from the X-1A crash site was brought back to Edwards AFB for examination. It was discovered that a gasket material used in the rocket engine fuel systems was reacting with the fuel, resulting in the explosions. The problem was corrected and the mysterious explosions stopped.
Test pilot Joe Walker “horsing around” with the Bell X-1A, 1955. (NASA)
9 August 1939: After General Henry H. Arnold had ordered that the prototype Bell Aircraft Corporation XP-39 Airacobra be evaluated in the National Advisory Committee for Aeronautics (NACA) Full-Scale Tunnel at the Langley Memorial Aeronautics Laboratory, Langley Field, Virginia, it was flown there from Wright Field. It was hoped that aerodynamic improvements would allow the prototype to exceed 400 miles per hour (644 kilometers per hour).
