Tag Archives: Speed of Sound

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 Browning AN-M2 .50-caliber 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

Facebooktwittergoogle_plusredditpinterestlinkedinmailby feather

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

Facebooktwittergoogle_plusredditpinterestlinkedinmailby feather

13 February 1923

Brigadier General Charles E. Yeager, U.S. Air Force (Retired), at Edwards AFB, 14 October 1997, the fiftieth anniversary of his Mach 1 flight. (Photograph © 2017 by Tim Bradley Imaging. Used with permission.)

13 February 1923: Brigadier General Charles Elwood Yeager, United States Air Force (Retired), was born at Myra, West Virginia.

Who is the greatest pilot I ever saw? Well, uh. . . Well, let me tell you. . . .

The following is from the official U.S. Air Force biography: (Photographs from various sources)

“The world’s first man-made sonic boom told the story. On Oct. 14, 1947, over dry Rogers Lake in California, Chuck Yeager rode the X-1, attached to the belly of a B-29 bomber, to an altitude of 25,000 feet. After releasing from the B-29, he rocketed to an altitude of 40,000 feet. Moments later he became the first person to break the sound barrier, safely taking the X-1 he called Glamorous Glennis to a speed of 662 mph, faster than the speed of sound at that altitude. His first words after the flight were, ‘I’m still wearing my ears and nothing else fell off neither.’

Captain Chuck Yeager on Rogers Dry Lake with the Bell X-1, 1948.
Captain Charles E. (“Chuck”) Yeager, USAF, at Rogers Dry Lake with the Bell X-1, 1948.

“Yeager was born in February 1923 in Myra, W. V. In September 1941, he enlisted as a private in the Army Air Corps. He was soon accepted for pilot training under the flying sergeant program and received his pilot wings and appointment as a flight officer in March 1943 at Luke Field, Ariz.

Aviation Cadet Charles E. Yeager, U.S. Army Air Corps. (U.S. Air Force)

“His first assignment was as a P-39 pilot with the 363rd Fighter Squadron, Tonopah, Nev. He went to England in November 1943 and flew P-51s in combat against the Germans, shooting down one ME-109 and an HE-111K before being shot down on his eighth combat mission over German-occupied France on March 5, 1944. He evaded capture by the enemy when elements of the French Maquis helped him to reach the safety of the Spanish border. That summer, he was released to the British at Gibraltar and returned to England. He returned to his squadron and flew 56 more combat missions, shooting down 11 more enemy aircraft.

Second Lieutenant Charles E. (“Chuck”) Yeager, U.S. Army Air Forces, standing on the wing of his North American Aviation P-51D-5-NA Mustang, 44-13897, Glamorous Glenn II, at Air Station 373, 12 October 1944. (U.S. Air Force)
First Lieutenant Charles E. (“Chuck”) Yeager, U.S. Army Air Corps, standing on the wing of his North American Aviation P-51D-5-NA Mustang, 44-13897, Glamorous Glenn II, at Air Station 373, 12 October 1944. (U.S. Air Force)

“Returning to stateside, Yeager participated in various test projects, including the P-80 Shooting Star and P-84 Thunderjet. He also evaluated all the German and Japanese fighter aircraft brought back to the United States after the war. This assignment led to his selection as pilot of the nation’s first research rocket aircraft, the Bell X-1, at Muroc Army Air Field (now Edwards Air Force Base, Calif.). After breaking the sound barrier in 1947, Yeager flew the X-1 more than 40 times in the next two years, exceeding 1,000 mph and 70,000 feet. He was the first American to make a ground takeoff in a rocket-powered aircraft. In December 1953 he flew the Bell X-1A 1,650 mph, becoming the first man to fly two and one-half times the speed of sound.

Captain Charles E. Yeager, USAF with a North American Aviation F-86A Sabre, Los Angeles, 21 January 1949. (© Bettman/CORBIS)
Captain Charles E. Yeager, USAF with a North American Aviation F-86A Sabre, Los Angeles, 21 January 1949. (Bettman/CORBIS)
Major Charles E. Yeager, U.S. Air Force, in the cockpit of the Bell X-1A rocketplane. (U.S. Air Force)
Major Charles E. Yeager, U.S. Air Force, in the cockpit of the Bell X-1A rocketplane. (U.S. Air Force)
Major Charles E. Yeager, USAF, Ramstein Air Base, Germany, 1958. (Stars and Stripes)
Lieutenant Colonel Charles E. Yeager, USAF, 1st Fighter Day Squadron, with North American Aviation F-100F-15-NA Super Sabre, 56-3950, George Air Force Base, California, 1958. (U.S. Air Force)
Lieutenant Colonel Charles E. Yeager, USAF, 1st Fighter Day Squadron, 413th Fighter Day Wing, with North American Aviation F-100F-15-NA Super Sabre, 56-3950, George Air Force Base, California, 1958. (Jet Pilot Overseas)
Colonel Charles E. (“Chuck”) Yeager, United States Air Force, 306th Tactical Fighter Squadron, 31st Tactical Fighter Wing, 1958. (U.S. Air Force)
Colonel Charles E. (“Chuck”) Yeager, USAF, commanding the 405th Fighter Wing, with crew chief TSGT Rodney Sirois, before a combat mission with a Martin B-57 Canberra during the Vietnam War. (Stars and Stripes)

“After a succession of command jobs, Yeager became commandant of the Aerospace Research Pilot School (now the U.S. Air Force Test Pilot School), where all military astronauts were trained.

Colonel Charles E. Yeager, USAF, in the cockpit of a Lockheed NF-104A Aerospace Trainer, 4 December 1963. (U.S. Air Force)
Colonel Charles E. Yeager, USAF, in the cockpit of a Lockheed NF-104A Aerospace Trainer, 4 December 1963. (U.S. Air Force)

“On Dec. 10, 1963, he narrowly escaped death while testing an NF-104 rocket-augmented aerospace trainer. His aircraft went out of control at 108,700 feet (nearly 21 miles up) and crashed. He parachuted to safety at 8,500 feet after battling to gain control of the powerless aircraft. He thus became the first pilot to make an emergency ejection in the full pressure suit needed for high altitude flights. Yeager has flown more than 200 types of military aircraft and has more than 14,000 hours, with more than 13,000 of them in fighter aircraft.

Brigadier General Charles E. Yeager, United States Air Force, July 1969. (Stars and Stripes)

“Yeager retired from active duty in the U. S. Air Force in March 1975, after serving as the United States defense representative to Pakistan and director of the Air Force Inspection and Safety Center, Norton AFB, Calif.

Brigadier General Charles E. Yeager, U.S. Air Force, made his final flight as an active duty officer aboard A McDonnell F-4C Phantom II at Edwards AFB, 25 February 1975. (U.S. Air Force)
Brigadier General Charles E. Yeager, U.S. Air Force, made his final flight as an active duty officer aboard a McDonnell Douglas F-4E Phantom II at Edwards AFB, 25 February 1975. (U.S. Air Force)

“Retirement was never part of his plans. He remains an active aviation enthusiast, acting as adviser for various films, programs and documentaries on aviation. He has published two books, entitled Yeager, An Autobiography and Press On: Further Adventures in the Good Life.”

Brigadier General Charles E. Yeager, United States Air Force

© 2017, Bryan R. Swopes

Facebooktwittergoogle_plusredditpinterestlinkedinmailby feather