Tag Archives: Mach 1

21 August 1961

Douglas DC-8-43 N9604Z is accopmanied by a U.S. Air Force Lockheed F-104A Starfighter, near Edwards Air Force base, California.
Douglas DC-8-43 N9604Z is accompanied by a U.S. Air Force Lockheed F-104A Starfighter, near Edwards Air Force Base, California. (Douglas Aircraft Co.)

On 21 August 1961, a Douglas DC-8-43, N9604Z, c/n 45623, Line Number 130, flown by Chief Test Pilot William Marshall Magruder, Paul Patten, Joseph Tomich and Richard H. Edwards climbed to 50,090 feet (15,267 meters) near Edwards Air Force Base. Placing the DC-8 into a dive, it reached Mach 1.012 (668 miles per hour/1,075 kilometers per hour) while descending through 41,088 feet (12,524 meters). The airliner maintained this supersonic speed for 16 seconds. This was the first time that a civil airliner had “broken the Sound Barrier.”

An Air Force F-100 Super Sabre and F-104 Starfighter were chase planes for this flight. Reportedly, the F-104 was flown by the legendary test pilot, Colonel Chuck Yeager.

The Douglas DC-8 is a commercial jet airliner, a contemporary of the Boeing 707 and Convair 880. It was operated by a flight crew of three and could carry up to 177 passengers. The DC-8 was powered by four turbojet or turbofan engines mounted on pylons suspended below the wings. The wings’ leading edges were swept to 30°, as was the vertical fin and horizontal tailplane.

The DC-8-40 series is 150 feet, 6 inches (45.872 meters) long with a wingspan of 142 feet, 5 inches (43.409 meters) and overall height of 42 feet, 4 inches (12.903 meters). It had an empty weight of 124,790 pounds (56,604 kilograms) and maximum takeoff weight of 315,000 pounds (142,882 kilograms).

The DC-8-40 series had a cruising speed of 0.82 Mach (542 miles per hour/872 kilometers per hour) at 35,000 feet (10,668 meters). Its maximum range was 5,905 nautical miles (6,795 statute miles, 10,936 kilometers).

N9604Z was powered by four Rolls-Royce Conway RCo.12 Mk 509 two-shaft axial-flow turbofan engines, rated at 17,500 pounds of thrust (77.844 kilonewtons) at 9,990 r.p.m. The 509 is 11 feet, 3.9 inches (3.452 meters) long, 3 feet, 6.2 inches (1.072 meters) in diameter, and weighs 4,542 pounds (2,060 kilograms).

N9604Z was delivered to Canadian Pacific Airlines 15 November 1961, re-registered CF-CPG, and named Empress of Montreal. It later flew under CP Air as Empress of Buenos Aires. The DC-8 was scrapped at Opa Locka Municipal Airport, north of Miami, Florida, in May 1981.

© 2016, Bryan R. Swopes

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26 April 1948

est Pilot George Welch flying the prototype North American Aviation XP-86 Sabre, 45-59597. (U.S. Air Force)
Test Pilot George Welch flying the prototype North American Aviation XP-86 Sabre, 45-59597. (U.S. Air Force)

26 April 1948: At Muroc Field (now known as Edwards Air Force Base), in the high desert of southern California, North American Aviation test pilot George Welch put the prototype XP-86 Sabre, 45-59597, into a 40° dive and broke the Sound Barrier. It is only the second U.S. aircraft to fly supersonic. The first was the Bell X-1, piloted by Chuck Yeager, only a few months earlier.

Or, maybe not.

In his book, Aces Wild: The Race For Mach 1, fellow North American Aviation test pilot Albert W. Blackburn makes the case that George Welch had taken the prototype XP-86 Sabre supersonic on its first flight, 1 October 1947, and that he had done so three times before Chuck Yeager first broke the Sound Barrier with the Bell X-1 rocketplane, 14 October 1947. Blackburn described two runs through the NACA radar theodolite with speeds of Mach 1.02 and 1.04 on 13 November 1947.

Mr. Blackburn speculates—convincingly, in my opinion—that Secretary of the Air Force W. Stuart Symington, Jr., ordered that Welch’s excursions beyond Mach 1 were to remain secret. However, during a radio interview, British test pilot Wing Commander Roland Prosper (“Bee”) Beamont CBE, DSO and Bar, DFC and Bar, stated that he had flown through the Sound Barrier in the number two XP-86 Sabre prototype (45-59598). Once that news became public, the Air Force released a statement that George Welch had flown beyond Mach 1 earlier, but gave the date as 26 April 1948.

Test pilot George S. Welch, wearing his distinctive orange helmet, in the cockpit of the prototype XP-86. This photograph was taken 14 October 1947. (U.S. Air Force)
Test pilot George S. Welch, wearing his distinctive orange helmet, in the cockpit of the prototype XP-86. This photograph was taken 14 October 1947. (U.S. Air Force)

It wasn’t long after the first flight of the XP-86 on October 1, 1947, that Welch dropped into Horkey’s [Edward J. Horkey, an aerodynamicist at North American Aviation] office at the Inglewood plant. He wanted to talk about his recent flight and some “funny” readings in the airspeed indicator. He had made a straight-out climb to more than 35,000 feet. Then, turning back toward Muroc Dry Lake, he began a full-power, fairly steep descent.

“I started at about 290 knots,” Welch was explaining to Horkey. “In no time I’m at 350. I’m still going down, and I’m still accelerating but the airspeed indicator seems stuck like there’s some kind of obstruction in the pitot tube. I push over a little steeper and by this time I’m through 30,000 feet. All of a sudden, the airspeed indicator flips to 410 knots. The aircraft feels fine, no funny noises, no vibration. Wanted to roll off to the left, but no big deal. Still, I leveled out at about 25,000 and came back on the power. The airspeed flicked back to 390. What do you think?”

“. . . You may be running into some Mach effects. . . .”

— Aces Wild: The Race For Mach 1, by Al Blackburn, Scholarly Resources Inc., Wilmington, Delaware, 1999, at Pages 147–148.

The “funny” reading of the airspeed indicator became known as the “Mach jump.” George Welch was the first to describe it.

The Sabre became a legendary jet fighter during the Korean War. 9,860 were built by North American, as well as by licensees in Canada, Australia and Japan.

George Welch had been recommended for the Medal of Honor for his actions as a P-40 Warhawk fighter pilot in Hawaii, December 7, 1941. He was killed while testing an F-100A Super Sabre, 12 October 1954.

Test pilot George S. Welch with a North American Aviation F-86 Sabre. (San Diego Air and Space Museum Archives)
Test pilot George S. Welch with a North American Aviation F-86 Sabre. (San Diego Air and Space Museum Archives)

© 2016, Bryan R. Swopes

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26 February 1955

A North American F-100A-1-NA Super Sabre, 52-5757 (the second production airplane) takes off at Los Angeles Airport. (This airplane, flown by NAA test pilot Bob Hoover, crashed east of Palmdale, California, 7 July 1955, when he could not recover from a flat spin. Hoover safely ejected but the Super Sabre was destroyed.) North American Aviation
A North American F-100A-1-NA Super Sabre, 52-5757 (the second production airplane) takes off at Los Angeles Airport. (This airplane, flown by NAA test pilot Bob Hoover, crashed east of Palmdale, California, 7 July 1955, when he could not recover from a flat spin. Hoover safely ejected but the Super Sabre was destroyed.) North American Aviation

26 February 1955: Although it was his day off, North American Aviation production test pilot George F. Smith stopped by the office at Los Angeles Airport (today, known as Los Angeles International airport, or simply “LAX”, its international airport identifier). The company’s flight  dispatcher told him that a brand-new F-100A-20-NA Super Sabre, serial number 53-1659, was sitting on the flight line and needed to be test flown before being turned over to the Air Force.

North American Aviation production test pilot George F. Smith (left) walks away from an F-100 Super Sabre. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineeers)
North American Aviation production test pilot George F. Smith (left) walks away from an F-100 Super Sabre. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineeers)

Smith was happy to take the flight. He departed LAX in full afterburner and headed off shore, climbing to 35,000 feet (10,668 meters) over the Pacific Ocean to start the test sequence.

North American Aviation F-100A-10-NA Super Sabre 53-1530 during a test flight near Edwards Air Force Base, California. This aircraft has an extended pitot boom installed. Notice the very clean lines of the supersonic fighter. This F-100A is very similar to the one flown by George F. Smith, 26 February 1955. (U.S. Air Force)
North American Aviation F-100A-10-NA Super Sabre 53-1530 during a test flight near Edwards Air Force Base, California. This aircraft has an extended pitot boom installed. Notice the very clean lines of the supersonic fighter. This F-100A is very similar to the one flown by George F. Smith, 26 February 1955. (U.S. Air Force)

But it was quickly apparent that something was wrong: The flight controls were heavy, and then there was a hydraulic system failure that caused the Super Sabre pitch down into a dive. Smith couldn’t pull it out of the dive and the airplane’s speed rapidly increased, eventually passing Mach 1.

Smith was unable to regain control of the F-100. He had no choice but to bail out. As he ejected, Smith read the instruments: the Mach meter indicated Mach 1.05—785 miles per hour (1,263 kilometers per hour)—and the altitude was only 6,500 feet (1,981 meters).

George F. Smith recovering in hospital after his supersonic ejection. (Getty Images)
George F. Smith recovering in hospital after his supersonic ejection. (Getty Images)

The force of the wind blast hitting him as he came out of the cockpit knocked him unconscious. Estimates are that he was subjected to a 40 G deceleration. His parachute opened automatically and he came down approximately one-half mile off Laguna Beach. Fortunately he hit the water very close to a fishing boat crewed by a former U.S. Navy rescue expert.

George Smith was unconscious for six days, and when he awoke he was blind in both eyes. After four surgeries and seven months in the hospital, he recovered from his supersonic ejection and returned to flight status.

North American Aviation F-100A-15-NA Super Sabre 53-1575 crosses the runway threshold as it lands at Holloman AFB, New Mexico. This is similar to the F-100A-20-NA flown by George F. Smith when he was forced to eject, 26 February 1955. (U.S. Air Force)
North American Aviation F-100A-15-NA Super Sabre 53-1575 crosses the runway threshold as it lands at Holloman AFB, New Mexico. This is similar to the F-100A-20-NA flown by George F. Smith when he was forced to eject, 26 February 1955. (U.S. Air Force)

George F. Smith appears in this brief U.S. Air Force informational film:

© 2016, Bryan R. Swopes

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26 December 1948

The ç
The Lavochkin La-176 (NPO Lavochkin)

26 December 1948: Test pilot Ivan Yevgrafovich Federov (also reported as Ivan E. Fyodorov) became the first pilot in the Soviet Union to exceed Mach 1 when he flew the Lavochkin La-176 in a dive from 9,050 meters (29,692 feet) to 6,000 meters (19,685 feet).

It was first thought that the La-176’s airspeed indicator had malfunctioned, but during subsequent testing conducted the first week of January 1949, Federov repeated the dive and six times reached Mach 1.02.

The La-176 was destroyed when its canopy failed during supersonic flight. Test pilot I.V. Sokolovsky was killed.

Lavochkin La-176
Lavochkin La-176

The La-176 was a single-seat, single-engine fighter, derived from the earlier La-168. The leading edge of its wings and tail surfaces were swept at 45°. The fighter was 36 feet (10.973 meters) long with a wingspan of 28 feet, 2 inches (8.585 meters). It had an empty weight of 3,111 kilograms (6,858.6 pounds)  and loaded weight of 4,631 kilograms (10,210 pounds).

The La-176 was powered by a Klimov VK-1 centrifugal-flow turbojet, developed from the Rolls-Royce Nene. The British engines were reverse-engineered by Vladimir Yakovlevich Klimov and manufactured at Factory No. 45 in Moscow as the Klimov VK-1. The VK-1 used a single-stage axial-flow compressor, 9 combustion chambers and a single-stage axial-flow turbine. It produced a maximum 26.5 kilonewtons of thrust (5,957 pounds of thrust). The VK-1 was 2.600 meters (8 feet, 6.4 inches) long, 1.300 meters (4 feet, 3.2 inches) in diameter, and weighed 872 kilograms (1,922 pounds).

The swept-wing jet had a maximum speed of 648 miles per hour (1,042.85 kilometers per hour) and a range of 621 miles (999.4 kilometers).

Armament consisted of one Nudelman N-37 30 mm cannon and two Nudelman-Suranov NS-23 23 mm cannon.

Lavochkin La-176
Lavochkin La-176

Colonel Ivan Yevgrafovich Federov (b. 23 February 1914) was a Soviet Air Force fighter pilot who fought in the Spanish civil war (where he was known as Diablo Rojo, the Red Devil), the Russo-Finish War, World War II, China and Korea. He may have shot down as many as 135 enemy airplanes. He was personally awarded the Iron Cross by Adolf Hitler, Chancellor of Germany, in 1941. His Soviet Awards include Hero of the Soviet Union, the Order of Lenin, Order of Alexander Nevsky, Order of the Red Banner, Order of the Patriotic War 1st Degree, Order of the Patriotic War 2nd Degree, and Order of the Red Star.

Colonel Ivan Yegrafovich Federov, Soviet Air Force.
Colonel Ivan Yegrafovich Federov, Soviet Air Force.

© 2016, Bryan R. Swopes

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13 November 1942

Two Republic Aviation Corporation P-47C Thunderbolts of the 56th Fighter Group retract their landing gear after takeoff. (U.S. Air Force)
Two Republic Aviation Corporation P-47C Thunderbolts of the 56th Fighter Group retract their landing gear after takeoff. (U.S. Air Force)

13 November 1942: Lieutenants Harold E. Comstock and Roger B. Dyar were fighter pilots assigned to the 63rd Fighter Squadron, 56th Fighter Group, at Bridgeport, Connecticut. They were often sent to test new P-47 Thunderbolt fighters at the Republic Aviation Corporation factory in nearby Farmingdale, New York:

Lieutenant Harold E. Comstock, U.S. Army Air Corps, with his P-47 Thunderbolt, 1943.

Because of the need to manufacture airplanes quickly and the close proximity to the Republic Aviation factory, active duty pilots were used for some of the test flights of the new P-47. On 13 November 1942, Lts. Comstock and Dyar were ordered to test a new type of radio antenna on the P-47C. Lt. Comstock climbed to an indicated altitude of 49,600 feet (15,118 meters) while trying to reach 50,000 feet. Due to poor response from the controls, he decided to let the aircraft fall off rather than risk a spin. He started to dive straight down and after passing below 40,000 feet he found that his controls had frozen. He then felt a bump and was unable to move the controls as the aircraft continued to dive. Even with maximum exertion, he was unable to move the control stick so he started to roll the trim tab back and after passing below 30,000 feet, the aircraft started to pull out of the dive and he recovered between 20,000 and 25,000 feet.

Lt. Dyar started his dive and encountered the same conditions. After landing, Lt. Comstock reported what happened and the chief designer of the P-47 Thunderbolt, Alexander Kartveli, questioned Lt. Comstock at length and made numerous calculations. Republic Aviation soon issued a press release claiming that Lts. Comstock and Dyar had exceeded the speed of sound. This was picked up in the national media and also drawn in Ripley’s Believe It or Not!. Soon after the press release, the 56th Fighter Group received a telegram from Gen. Henry “Hap” Arnold that “there would be no more discussion about the dive.” The actual speed attained was probably less than the speed of sound but this speed which caused the flight controls to lock up was referred to as “compressibility.” This effect was encountered by many pilots flying in combat but training and proper procedures allowed them to recover from it. In 1959, the Air Force published “A Chronology of American Aerospace Events” and included an entry for 15 November 1942 which stated “Lts. Harold Comstock and Roger Dyar set a new speed record for airplanes when they power-dived their P-47 fighters at 725 mph from 35,000 feet over an east coast air base.” While the Air Force acknowledged the speed of 725 miles per hour, it is not known whether the P-47 could actually exceed the speed of sound in a dive. Capt. Roger Dyar was killed in action on 26 June 1943.Wikipedia

The instrument panel of a Republic P-47D-40-RA Thunderbolt in the collection of the National Museum of the United States Air Force. The Airspeed Indicator is in the second row of instruments, just left of center. Note that the maximum speed marked on the face of the gauge is 700 miles per hour. (U.S. Air Force)
The instrument panel of a Republic P-47D-40-RA Thunderbolt in the collection of the National Museum of the United States Air Force. The Airspeed Indicator is in the second row of instruments, just left of center. Note that the maximum speed marked on the face of the gauge is 700 miles per hour. (U.S. Air Force)

Almost certainly, the diving Thunderbolts did not exceed the speed of sound:

In July 1944 Major [Frederic Austin] Borsodi [Chief, Fighter Test Branch, Army Air Forces Material Command, Wright Field] made a number of full power vertical dives from 40,000 feet in a North American P-51D to assess the compressibility effects on the aircraft’s handling. He achieved a maximum Mach number of 0.86, at which point severe buffeting of the empennage was noted. . . many World War II pilots remained firmly convinced that they had taken their propeller-driven fighters supersonic in steep dives, often as local shock waves rattled their craft and caused the angle of those dives to become uncontrollably steeper. More often than not the center of lift moved aft on their wings, and Mach-induced turbulence blanketed the normal control surfaces on the tail. For the lucky ones, the descent into denser air slowed the airplane, while the higher temperatures at lower altitude meant that the Mach number for a given true airspeed was lower. Consequently, local shock waves tended to disappear. A normal recovery as from any steep dive, could usually be effected. . . the later [Supermarine] Spitfires, with a demonstrated ceiling of 45,000 feet, a much thinner wing of elliptical planform, and a lower profile liquid-cooled engine, could never register a maximum speed greater than 0.9 Mach number. That is the highest recorded speed, by a substantial margin of any propeller driven fighter. Oh yes, in the course of one such dive, on entering the denser air around 20,000 feet, the Spitfire’s propeller and much of the engine cowling parted company with the rest of the aircraft. Getting to 0.90 Mach number wasn’t easy. . . the speed of sound at sea level and 59° Fahrenheit is 761 miles per hour. At an altitude of 40,000 feet, where our standard atmosphere charts tell us that the temperature is -67° Fahrenheit, sound travels at 662 miles per hour.

Aces Wild: The Race For Mach 1, by Al Blackburn, Scholarly Resources, Inc., Wilmington, Delaware, at Pages 6–7, 24–27.

Captain Harold E. Comstock, United States Army Air Corps. (U.S. Air Force)
Captain Harold E. Comstock, United States Army Air Corps, 1944. (U.S. Air Force)

Harold Comstock flew two combat tours in Europe with the 56th Fighter Group during World War II. He completed his second tour as commanding officer of the group’s 63rd Fighter Squadron. He flew 138 combat missions and is officially credited with destroying 5 enemy aircraft in aerial combat, with 2 probably destroyed and 3 damaged, and another 3 destroyed on the ground.

During the Vietnam War, Lieutenant Colonel Comstock commanded the 481st Tactical Fighter Squadron, 27th Tactical Fighter Wing from 1965 to 1968. He flew another 132 combat missions in the North American Aviation F-100D Super Sabre, and 38 as commander of an airborne command and control unit of the 7th Airborne Command and Control Squadron.

Colonel Comstock retired from the Air Force in 1971. He was twice awarded the Legion of Merit, and he held the Distinguished Flying Cross with six Oak Leaf Clusters, a Purple Heart, and 17 Air Medals.

Harold E. Comstock died at Clovis, California in 2009.

Lieutenant Colonel Harold E. Comstock, U.S. Air Force, 481st Tactical Fighter Squadron, 26th Tactical Fighter Wing, with a North American Aviation F-100D-26-NA Super Sabre, 55-3623, at Cannon Air Force Base, New Mexico, 1964. (Jet Pilot Overseas)
Lieutenant Colonel Harold E. Comstock, U.S. Air Force, 481st Tactical Fighter Squadron, 26th Tactical Fighter Wing, with a North American Aviation F-100D-26-NA Super Sabre, 55-3623, at Cannon Air Force Base, New Mexico, 1964. (Jet Pilot Overseas)

The Republic P-47 Thunderbolt was the largest single-engine fighter that had yet been built. The first P-47C variant was completed 14 September 1942, only one month before Bunny Comstock’s famous dive. An early change (P-47C-1) was the addition of 8 inches (0.203 meters) to the forward fuselage for improved handling. The P-47C-5-RE was 36 feet, 1-3/16 inches (11.003 meters) long with a wingspan of 40 feet, 9-5/16 inches (12.429 meters) The overall height was 14 feet 3-5/16 inches (4.351 meters). The fighter’s empty weight was 9,900 pounds (4,490.6 kilograms) and maximum gross weight was 14,925 pounds (6,769.9 kilograms).

The P-47C was powered by an air-cooled, supercharged, 2,804.4-cubic-inch-displacement (45.956 liter) Pratt & Whitney Double Wasp TSB1-G (R-2800-21) two-row, 18-cylinder radial engine with a compression ratio of 6.65:1. The R-2800-21 had a Normal Power rating of 1,625 horsepower at 2,550 r.p.m. to 25,000 feet (7,620 meters) and a Takeoff/Military Power rating of  2,000 horsepower at 2,700 r.p.m. to an altitude of 25,000 feet (7,620 meters). A large General Electric turbosupercharger was mounted in the rear of the fuselage. Internal ducts carried exhaust gases from the engine to drive the turbocharger and the supercharged air was then carried forward to supply the engine. The engine drove a 12 foot, 2 inch (3.708 meter) diameter four-bladed Curtiss Electric propeller through a 2:1 gear reduction. The R-2800-21 was 6 feet, 3.72 inches (1.923 meters) long, 4 feet, 4.50 inches (1.340 meters) in diameter, and weighed 2,265 pounds (1,027 kilograms). Approximately 80% of these engines were produced by the Ford Motor Company. It was also used as a commercial aircraft engine, with optional propeller gear reduction ratios.

The P-47C had a maximum speed in level flight of 433 miles per hour (697 kilometers per hour) at 30,000 feet (9,144 meters). The service ceiling was 42,000 feet (12,802 meters), and it could climb to 15,000 feet (4,572 meters) in 7 minutes, 12 seconds. It had a maximum range of 1,250 miles (2,012 kilometers) with external fuel tanks.

Republic P-47D-6-RE Thunderbolt 42-74742 at RAF Duxford during World War II. The maintenance technicians show the fighter's enormous size. (Daily Mail)
Republic P-47D-6-RE Thunderbolt 42-74742 at RAF Duxford during World War II. The four maintenance technicians show the fighter’s enormous size. (Daily Mail)

The Thunderbolt was armed with eight .50-caliber Browning M2 machine guns, four in each wing, with 3,400 rounds of ammunition. It could also carry external fuel tanks, rockets and bombs. The structure of the P-47 could be described as “robust” and it was heavily armored.

602 P-47Cs were built in the five months before the P-47D entered production. A total of 15,683 Thunderbolts were built; more than any other Allied fighter type. In aerial combat it had a kill-to-loss ratio of 4.6:1. The amount of damage that the airplane could absorb and still return was remarkable. The P-47, though, really made its name as a ground attack fighter, destroying aircraft, locomotives, rail cars, and tanks by the many thousands. It was one of the most successful aircraft of World War II.

UN Y, Bunny Comstock's P-47C-5-RE Thunderbolt 41-6326. (U.S. Air Force)
UN Y, Bunny Comstock’s Republic P-47C-5-RE Thunderbolt 41-6326. (U.S. Air Force)
Colonel Comstock's Republic P-47C-5-RE Thunderbolt 41-6326 after a crash landing at Beccles, Suffolk, England, 3 February 1944. (U.S. Air Force)
Low on fuel after a combat mission, Lieutenant Comstock’s Republic P-47C-5-RE Thunderbolt 41-6326  crashed at Lyons Farm, Mutford, Suffolk, England, 3 February 1944. (U.S. Air Force)

© 2016, Bryan R. Swopes

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