Tag Archives: Flight Test

27 September 1956

Captain Milburn G. Apt, U.S. Air Force, with a Bell X-2. (U.S. Air Force)
Captain Milburn Grant Apt, United States Air Force, with a Bell X-2. (U. S. Air Force)

27 September 1956: Captain Milburn G. (“Mel”) Apt, United States Air Force, was an experimental test pilot assigned to the Air Force Flight Test Center at Edwards Air Force Base, California. After Frank Everest and Iven Kincheloe had made twelve powered flights in the Bell X-2 supersonic research aircraft, Mel Apt was the next test pilot to fly it.

The X-2 was a joint project of the U.S. Air Force and NACA (the National Advisory Committee on Aeronautics, the predecessor of NASA). The rocketplane was designed and built by Bell Aircraft Corporation of Buffalo, New York, to explore supersonic flight at speeds beyond the capabilities of the earlier Bell X-1 and Douglas D-558-II Skyrocket.

In addition to the aerodynamic effects of speeds in the Mach 2.0–Mach 3.0 range, engineers knew that the high temperatures created by aerodynamic friction would be a problem, so the aircraft was built from stainless steel and K-Monel, a copper-nickel alloy.

The Bell Aircraft Corporation X-2 was 37 feet, 10 inches (11.532 meters) long with a wingspan of 32 feet, 3 inches (9.830 meters) and height of 11 feet, 10 inches (3.607 meters). Its empty weight was 12,375 pounds (5,613 kilograms) and loaded weight was 24,910 pounds (11,299 kilograms).

Bell X-2 46-675 on its transportation dolly at Edwards Air Force Base, California, 1952. (NASA)
The second of two Bell X-2 supersonic research rocketplanes, 46-675, on its transportation dolly at Edwards Air Force Base, California, 1952. On 12 May 1953 this X-2 exploded during a captive test flight, killing Bell’s test pilot Jean L. “Skip” Ziegler. (NASA)

The X-2 was powered by a throttleable two-chamber Curtiss-Wright XLR25-CW-1 rocket engine that produced 2,500–15,000 pounds of thrust (11.12–66.72 kilonewtons)

Rather than use its limited fuel capacity to take off and climb to altitude, the X-2 was dropped from a modified heavy bomber as had been the earlier rocketplanes. A four-engine Boeing B-50D-95-BO Superfortress bomber, serial number 48-096, was modified as the drop ship and redesignated EB-50D.

The launch altitude was 30,000 feet (9,144 meters). After the fuel was exhausted, the X-2 glided to a touchdown on Rogers Dry Lake at Edwards Air Force Base.

Bell X-2 46-674 after drop from Boeing EB-50D Superfortress 48-096. (U.S. Air Force)
Bell X-2 46-674 after drop from Boeing EB-50D Superfortress 48-096. (U.S. Air Force)

With Mel Apt in the cockpit on his first rocketplane flight, the B-50 carried the X-2 to 31,800 feet (9,693 meters). After it was dropped from the bomber, Apt ignited the rocket engine and began to accelerate. He passed Mach 1 at 44,000 feet (13,411 meters) and continued to climb. Apt flew an “extraordinarily precise profile” to reach 72,200 feet (22,007 meters) where he put the X-2 into a dive. The rocket engine burned 12.5 seconds longer than planned, and at 65,589 feet (19,992 meters) the X-2 reached Mach 3.196 (2,094 miles per hour, 3,377 kilometers per hour).

Milburn Apt was the first pilot to exceed Mach 3. He was The Fastest Man Alive.

Bell X-2 46-674 in flight over Southern California, 1955–56. Note the supersonic diamond-shaped shock waves in the rocket engine's exhaust. (Bell aircraft Corporation)
Bell X-2 46-674 in flight over Southern California, 1955–56. Note the supersonic diamond-shaped shock waves in the rocket engine’s exhaust. (Bell Aircraft Corporation)

It was known that the X-2 could be unstable in high speed maneuvers. The flight plan called for Apt to slow to Mach 2.4 before beginning a gradual turn back toward Rogers Dry Lake where he was to land, but he began the turn while still at Mach 3. Twenty seconds after engine burn out, the X-2 began to oscillate in all axes and departed controlled flight. His last radio transmission was, “There she goes.” ¹

Mel Apt was subjected to acceleration forces of ± 6 Gs. It is believed that he was momentarily unconscious. Out of control, the X-2 fell through 40,000 feet (12,192 meters) in an inverted spin. Apt initiated the escape capsule separation, in which the entire nose of the X-2 was released from the airframe. It pitched down violently and Mel Apt was knocked unconscious again. He regained consciousness a second time and tried to parachute from the escape capsule, but was still inside when it hit the desert floor at several hundred miles per hour. Mel Apt was killed instantly.

Since 1950, Milburn G. Apt was the thirteenth test pilot killed at Edwards Air Force Base.

Wreckage of the Bell X-2, 46-674. (U.S. Air Force)
Wreckage of the Bell X-2, 46-674, in the Kramer Hills, east of Edwards Air Force Base. (U.S. Air Force)
Wreckage of the Bell X-2, 46-674. (NASM 9A08208)

Milburn Grant Apt was born at Buffalo, Kansas, 8 April 1924. He was the third child of Oley Glen Apt, a farmer, and Ada Willoughby Apt.

“Mel” Apt enlisted as a private in the Air Corps Enlisted Reserve, United States Army, 9 November 1942. On 23 June 1943, Private Apt was appointed an Aviation Cadet. After completing flight training, Cadet Apt was commissioned a Second Lieutenant, Army of the United States (A.U.S.). He was promoted to First Lieutenant, A.U.S., 4 September 1945. Apt was released from active duty on 11 August 1946. On 10 October 1947, he was reclassified as a Second Lieutenant, Air Corps, United States Army, with date of rank 8 April 1945.

In February 1950, Lieutenant Apt, then stationed at Williams Air Force Base, Arizona, married Miss Faye Lorrie Baker of Phoenix. They would have two children.

Mel Apt earned a Bachelor of Science degree from the University of Kansas, Lawrence, Kansas, in 1951, and a second bachelor’s degree in aeronautical engineering from the Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio. He then attended the U.S. Air Force Experimental Test Pilot School at Edwards Air Force Base, California, graduating in September 1954. Apt was assigned to the Fighter Operations Branch, Air Force Flight Test Center, as a test pilot.

On 22 December 1954, Captain Apt was flying a chase plane during a test at Edwards. The test aircraft crash-landed on the dry lake and caught fire with its pilot trapped inside. Mel Apt, with his bare hands, rescued the other test pilot, saving his life. For this courageous act, he was awarded the Soldier’s Medal.

Captain Apt was posthumously awarded the Distinguished Flying Cross for his flight in the X-2. The medal was presented to his widow in a ceremony at Edwards in March 1957.

Captain Milburn Grant Apt, United States Air Force, was 32 years old at the time of his death. His remains were buried at the Buffalo Cemetery, Buffalo, Kansas.

Captain Iven Carl Kincheloe and Captain Milburn Grant Apt (seated in cockpit) with the Bell X-2 at Edwards Air Force Base, 1956. (Jet Pilot Overseas)

¹ Recommended: Coupling Dynamics in Aircraft: A Historical Perspective, by Richard E. Day, Dryden Flight Research Center, Edwards AFB, California NASA Special Publications 532, 1997.

© 2018, Bryan R. Swopes

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27 September 1946

Geoffrey Raoul de Havilland, Jr., OBE. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)
Geoffrey Raoul de Havilland, Jr., O.B.E. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

27 September 1946: Geoffrey Raoul de Havilland, Jr., O.B.E., Chief Test Pilot of the de Havilland Aircraft Co., Ltd., and the son of the firm’s founder, was killed during a test flight of a prototype DH.108 Swallow, TG306.

Geoffrey de Havilland, Jr., in the cockpit of the second DH.108 Swallow prototype, TG/306. (Flight)
Geoffrey de Havilland, Jr., in the cockpit of the second DH.108 Swallow prototype, TG306. (FLIGHT)

De Havilland had taken off from the company airfield at Hatfield at 5:26 p.m. for a planned 45 minute flight. Flying over the Thames Estuary, east of London, England, de Havilland put the swept-wing jet into a high-speed dive from 10,000 feet (3,048 meters). As it approached 5,000 feet (1,524 meters) at 0.88 Mach, (658 miles per hour, 1,060 kilometers per hour), the shock waves building up along the wings’ leading edges disrupted the air flow over the wings, causing them to stall. TG306 pitched violently downward. A NASA report called this “. . . an undamped violently divergent longitudinal pitching oscillation at Mach 0.875. . . .”  The extreme aerodynamic loads cracked the main spar and both wings failed. The DH.108 crashed into Egypt Bay, Gravesend, Kent.

The wreck was located the following day. The body of Geoffrey de Havilland was found ten days later. He had suffered a broken neck and fractured skull as a result of his head striking the canopy during the violent oscillations of the aircraft.

(Grace’s Guide)

FLIGHT reported:

Geoffrey de Havilland was one of the outstanding test pilots in the country, and his work has played a vital part in the perfecting of such noteworthy types as the Mosquito, Hornet, Vampire and 108. His death is a serious blow not only to the company but to the country, for in the exploration of the unknown threshold of sonic flight, a combination of skill and cool courage are qualities demanding the utmost of test pilots. Geoffrey de Havilland had these qualities in a very high degree.

FLIGHT and AIRCRAFT ENGINEER, No.1971, Vol. 1, Thursday, 3 October 1946, at page 364

De Havilland DH.108 TG/306. (Unattributed)
De Havilland DH.108 TG306. (Unattributed)

The DH.108 was a single-seat, single-engine jet fighter prototype with swept wings and no conventional tail. It was similar in configuration to the Messerschmitt Me-163 rocket-powered interceptor. The first two prototypes, TG283 and TG306, were built using production English Electric DH.106 Vampire F.I fuselages. TG283 had a 43° sweep to the wings’ leading edge, while TG306 had a 45° sweep. The airplane was powered by a de Havilland Goblin 3 centrifugal-flow turbojet engine (a development of the Halford H.1) which produced 3,350 pounds of thrust (14.90 kilonewtons).

The first and third DH.108s also crashed. VW120 was destroyed on 15 February 1950 when it crashed after a dive. The left wing had separated and the pilot, Squadron Leader Stuart Muller-Rowland, also suffered a broken neck as a result of the airplane’s violent oscillations. On 1 May 1950, while conducting low-speed tests, TG283 went into an inverted spin. Squadron Leader George E.C. Genders, AFC, DFM, bailed out but his parachute did not open before he hit the ground and he was killed.

Geoffrey de Havilland, Jr., exits the cockpit of one of the company's jet aircraft. (Photograph Courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)
Geoffrey de Havilland, Jr., OBE, exits the cockpit of a DH.108 Swallow prototype. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

© 2018, Bryan R. Swopes

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21 September 1942

A Boeing XB-29 takes off from Boeing Field, Seattle, Washington. (SDASM)
Edmund T. ("Eddie") Allen
Edmund T. (“Eddie”) Allen

21 September 1942: At Boeing Field, Seattle, Washington, the Boeing Model 345, the first of three XB-29 prototypes, Air Corps serial number 41-002, took off on its first flight.

Edmund T. “Eddie” Allen, Director of Aerodynamics and Flight Research, was in command, with Al Reed, Chief of Flight Test and Chief Test Pilot, as co-pilot. They climbed to 6,000 feet (1,829 meters) and began testing the XB-29’s stability and control, control power and response, and stall characteristics.

The flight was uneventful. Landing after 1 hour, 15 minutes, Allen is supposed to have said, “She flew!”

Eddie Allen lean’s out of a cockpit window following the first taxi test of the XB-29. (Boeing)

The XB-29 was 98 feet, 2 inches (29.921 meters) long with a wing span of 141 feet, 3 inches (43.053 meters), and 27 feet, 9 inches (8.458 meters) high to the top of its vertical fin. The prototype bomber had a gross weight of 105,000 pounds (47,627 kilograms).

Boeing XB-29-BO, 41-002, the first XB-29 built. (U.S. Air Force)
Boeing XB-29-BO, 41-002, the first of three prototypes. (U.S. Air Force)

The prototype bomber was powered by four air-cooled, supercharged and fuel-injected 3,347.662-cubic-inch-displacement (54.858 liter) Wright Aeronautical Division Duplex-Cyclone 670C18H1 (R-3350-13) twin-row 18-cylinder radial engines with a compression ratio of 6.85:1. The R-3350-13 was rated at 2,000 horsepower at 2,400 r.p.m., and 2,200 horsepower at 2,800 r.p.m. for takeoff, burning 100-octane gasoline. These engines drove 17-foot-diameter (5.182 meters) three-bladed Hamilton Standard constant-speed propellers through a gear reduction of 0.35:1. The R-3350-13 was 76.26 inches (1.937 meters) long, 55.78 inches (1.417 meters) in diameter, and weighed 2,668 pounds (1,210 kilograms). Wright built 50 of these engines.

Boeing XB-29 41-002. (SDASM)

The XB-29 had a maximum speed of 368 miles per hour (592 kilometers per hour) and cruised at 255 miles per hour (410 kilometers per hour). Its service ceiling was 32,100 feet (9,784 meters).

The airplane was designed to carry 20,000 pounds (9,072 kilograms) of bombs. Though the prototypes were unarmed, the production B-29s were defended by 10 Browning AN-M2 .50-caliber machine guns in four remotely-operated power turrets, with 2 more .50-caliber machine guns and a single AN-M2 20mm autocannon in the tail.

Boeing XB-29 41-002. (SDASM)

The B-29 Superfortress was the most technologically advanced—and complex—aircraft of the War. It required the manufacturing capabilities of the entire nation to produce. Over 1,400,000 engineering man-hours had been required to design the prototypes.

The B-29 was manufactured by Boeing at Seattle and Renton, Washington, and at Wichita, Kansas; by the Glenn L. Martin Company at Omaha, Nebraska; and by Bell Aircraft Corporation, Marietta, Georgia. There were three XB-29 prototypes, 14 YB-29 pre-production test aircraft, 2,513 B-29, 1,119 B-29A, and 311 B-29B Superfortress aircraft. The bomber served during World War II and the Korean War and continued in active U.S. service until 1960.

The first prototype, 41-002, was scrapped in 1948.

Boeing B-29A-30-BN Superfortress 42-94106, circa 1945. (U.S. Air Force)
Boeing B-29A-30-BN Superfortress 42-94106, circa 1945. (U.S. Air Force)

© 2018, Bryan R. Swopes

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20 September 1904

Wilbur Wright, 1867–1912. (Library of Congress)

20 September 1904: In an effort to improve their airplane, the Wright Brothers moved their test flights from the windy Kill Devil Hills of North Carolina to Huffman Prairie, near Dayton, Ohio. Without the winds, however, they needed to achieve greater speed for the airplane to take off, so they devised a catapult which used a 1,200 pound (544 kilogram) weight dropped from a 20 foot (6.1 meter) wooden derrick to pull the Wright Flyer II down a wooden track.

The Wright Flyer II was very similar to the original Flyer. Some parts of the airframe were strengthened, which slightly increased the new airplane’s weight.

Wilbur Wright was at the controls of the Flyer II on 20 September 1904, when it made the first-ever complete circular turn by an airplane. This was witnessed by Ames I. Root, who wrote about it in his magazine, Gleanings in Bee Culture:

“When it turned that circle, and came near the starting-point, I was right in front of it, and I said then and I believe still, it was. . . the grandest sight of my life. Imagine a locomotive that has left its track, and is climbing right toward you – a locomotive without any wheels. . . but with white wings instead. . . Well, now, imagine that locomotive with wings that spread 20 feet each way, coming right toward you with the tremendous flap of its propellers, and you have something like what I saw.”

The 30th flight of Flyer II at Huffman Prairie, August 1904. (Wright State University)

The Wright Brothers flew the Flyer II 105 times that summer. Next would come the Flyer III.

Wilbur Wright and the Flyer II on Flight 85 at Huffman Prairie. (Wright State University)

© 2015, Bryan R. Swopes

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11 September 1953

A Grumman F6F-5K Hellcat drone awaits its fate on “death row” at Armitage Field, NOTS China Lake, California. (U.S. Navy)

11 September 1953: At Naval Ordnance Test Station China Lake, the experimental Philco/General Electric XAAM-N-7 “Sidewinder” heat-seeking air-to-air missile scored its first “hit” when it passed within 2 feet (0.6 meters) of a radio-controlled Grumman F6F-5K Hellcat. The missile was fired from a Douglas AD-4 Skyraider flown by Lieutenant Commander Albert Samuel Yesensky, United States Navy, the Officer-in-Charge (OIC) of Guided Missile Unit SIXTY-ONE (GMU-61).

XAAM-N-7 Sidewinder mounted under the right wing of Douglas AD-4 Skyraider Bu. No. 123920 (U.S. Navy)
XAAM-N-7 Sidewinder mounted under the right wing of Douglas AD-4 Skyraider Bu. No. 123920 (U.S. Navy)

The Sidewinder was later redesignated AIM-9. It entered service in 1956 as the AIM-9B and has been a primary fighter weapon for 60 years.

A Raytheon XAAM-N-7 Sidewinder I missile mounted under the left wing of a Douglas AD-4 Skyraider, Bu. No. 123920, circa 1952. (U.S. Navy)
This black-and-white photograph of a Philco/General Electric Sidewinder I missile shows better detail. It is mounted under the left wing of Douglas AD-4 Skyraider, Bu. No. 123920, circa 1952. (U.S. Navy)

The AIM-9 Sidewinder is a Mach 2.5+ missile, equipped with an infrared seeker to track the heat signature of the target aircraft. (The Hellcat drones used in the early test had flares mounted on the wingtips to give the experimental missile a target).

The current production version, AIM-9X Block II, is produced by Raytheon Missile Systems, Tucson, Arizona. It is 9 feet, 11 inches long (3.023 meters), 5 inches in diameter (12.70 centimeters), and weighs 188 pounds (85 kilograms). The warhead weighs 20.8 pounds (9.4 kilograms). The missile’s range and speed are classified. At current production levels, the average cost of each AIM-9X is $420,944 (FY 2015 cost). Block III development was cancelled for FY 2106.

Future Astronaut Wally Schirra flew many of the early test flights at NOTS China Lake. On one occasion, a Sidewinder came back at him, and only by skill and luck was he able to evade it.

This sequence shows the effects of a hit on an F6F-5K drone by an experimental XAAM-N-7 Sidewinder missile. (U.S. Navy)
This sequence shows the effects of a hit on an F6F-5K drone by an experimental XAAM-N-7 Sidewinder missile. (U.S. Navy)

NOTC China Lake is now designated as Naval Air Weapons Station (NAWS) China Lake. It is located approximately 55 miles (88 kilometers) north-northeast of Edwards Air Force Base in the high desert of Southern California.

© 2018, Bryan R. Swopes

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