Misplaced Pages

#989010

80-601: Although the USAF Wright Air Development Center was the key sponsor of the Republic Project 3347 turboprop fighter, the initial inception came from a U.S. Navy requirement for a carrier fighter not requiring catapult assistance. Originally known as XF-106 (a designation later reused for the Convair F-106 ), the project and its resultant prototype aircraft were redesignated XF-84H, closely identifying

160-416: A {\displaystyle {\tfrac {1}{\mathrm {Ma} }}} of the plane's Mach number M a = v object v sound {\displaystyle \mathrm {Ma} ={\tfrac {v_{\text{object}}}{v_{\text{sound}}}}} . Thus the faster the plane travels, the finer and more pointed the cone is. There is a rise in pressure at the nose, decreasing steadily to

240-404: A Mach cone , similar to a vapour cone , with the aircraft at its tip. The half-angle α {\displaystyle \alpha } between the direction of flight and the shock wave is given by: where v sound v object {\displaystyle {\tfrac {v_{\text{sound}}}{v_{\text{object}}}}} is the inverse 1 M

320-476: A $ 247.5 million contract to construct a design known as the Low Boom Flight Demonstrator , which aims to reduce the boom to the sound of a car door closing. As of October 2023, the first flight was expected in 2024. The sound of a sonic boom depends largely on the distance between the observer and the aircraft shape producing the sonic boom. A sonic boom is usually heard as a deep double "boom" as

400-404: A boom to reach the ground, the aircraft's speed relative to the ground must be greater than the speed of sound at the ground. For example, the speed of sound at 30,000 feet (9,100 m) is about 670 miles per hour (1,080 km/h), but an aircraft must travel at least 750 miles per hour (1,210 km/h) (Mach 1.12) for a boom to be heard on the ground. The composition of the atmosphere is also

480-399: A corresponding decrease or increase in sound speed. Under standard atmospheric conditions, air temperature decreases with increased altitude. For example, when the sea-level temperature is 59 degrees Fahrenheit (15 °C), the temperature at 30,000 feet (9,100 m) drops to minus 49 degrees Fahrenheit (−45 °C). This temperature gradient helps bend the sound waves upward. Therefore, for

560-404: A distinctive "double boom" from a supersonic aircraft. When the aircraft is maneuvering, the pressure distribution changes into different forms, with a characteristic U-wave shape. Since the boom is being generated continually as long as the aircraft is supersonic, it fills out a narrow path on the ground following the aircraft's flight path, a bit like an unrolling red carpet , and hence known as

640-405: A factor. Temperature variations, humidity , atmospheric pollution , and winds can all affect how a sonic boom is perceived on the ground. Even the ground itself can influence the sound of a sonic boom. Hard surfaces such as concrete , pavement , and large buildings can cause reflections that may amplify the sound of a sonic boom. Similarly, grassy fields and profuse foliage can help attenuate

720-558: A massive reorganization ensued, however, ASC retained its leading role in the acquisition of new systems and the upgrade and modification of existing systems to support the Air Force's Core Competencies into the 21st century. In light of the new security climate ASC moved to upgrade the B-1 Lancer and B-2 Spirit from exclusively nuclear to conventional weapons. Subsequently, both airframes have seen active combat roles. ASC has also placed

800-408: A negative pressure at the tail, followed by a sudden return to normal pressure after the object passes. This " overpressure profile" is known as an N-wave because of its shape. The "boom" is experienced when there is a sudden change in pressure; therefore, an N-wave causes two booms – one when the initial pressure rise reaches an observer, and another when the pressure returns to normal. This leads to

880-410: A number of substitutes, including synthetic rubber for tires, nylon for parachutes, and plastic for canopies. The Armament Laboratory developed armored, self-sealing fuel tanks, increased bomb load capacity, gun turrets, and defensive armament. Despite the immediate needs of World War II the command continued to work on future projects. In 1944, Major Ezra Kotcher undertook pioneering work that led to

SECTION 10

#1732847573990

960-469: A premium on Information Superiority and focused heavily on building sensors for the U-2 and unmanned aerial vehicles . The Aeronautical Systems Center was inactivated on 20 July 2012; its units were merged into Air Force Life Cycle Management Center . [REDACTED]  This article incorporates public domain material from the Air Force Historical Research Agency Sonic boom A sonic boom

1040-465: A reduction in boom by about one-third. Although one-third is not a huge reduction, it could have reduced Concorde's boom to an acceptable level below FM = 1. As a follow-on to SSBD, in 2006 a NASA - Gulfstream Aerospace team tested the Quiet Spike on NASA Dryden's F-15B aircraft 836. The Quiet Spike is a telescoping boom fitted to the nose of an aircraft specifically designed to weaken the strength of

1120-480: A strong and downwards-focused ( SR-71 Blackbird , Boeing X-43 ) shock at a sharp, but wide angle nose cone, which will travel at slightly supersonic speed ( bow shock ), and using a swept back flying wing or an oblique flying wing to smooth out this shock along the direction of flight (the tail of the shock travels at sonic speed). To adapt this principle to existing planes, which generate a shock at their nose cone and an even stronger one at their wing leading edge,

1200-513: A workforce of more than 11,000 people located at Wright-Patterson Air Force base and 38 other locations worldwide. ASC's portfolio included capabilities in fighter/attack, long-range strike, reconnaissance, mobility, agile combat support, special operations forces, training, unmanned aircraft systems, human systems integration and installation support. ASC was deactivated during a 20 July 2012 ceremony held at Wright-Patterson Air Force Base, Ohio. The Airplane Engineering Department, precursor of ASC,

1280-550: Is a sound associated with shock waves created when an object travels through the air faster than the speed of sound . Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to the human ear. The crack of a supersonic bullet passing overhead or the crack of a bullwhip are examples of a sonic boom in miniature. Sonic booms due to large supersonic aircraft can be particularly loud and startling, tend to awaken people, and may cause minor damage to some structures . This led to

1360-874: Is also inconsistent with data from the National Museum of the United States Air Force, which gives a top speed of 520 mph (840 km/h) (Mach 0.70), nonetheless, making the XF-84H the fastest single-engine propeller-driven aircraft until 1989 when " Rare Bear ", a highly modified Grumman F8F Bearcat , reached 528 mph (850 km/h) (Mach 0.71). Two prototypes were built (51-17059 and 51-17060), with buzz numbers FS-059 and FS-060 . General characteristics Performance Related development Aircraft of comparable role, configuration, and era Related lists Wright Air Development Center The Aeronautical Systems Center ( ASC )

1440-406: Is an inactivated Air Force product center that designed, developed and delivered weapon systems and capabilities for U.S. Air Force , other U.S. military, allied and coalition-partner warfighters. ASC formed in 1961, and over its lifetime it managed 420 Air Force, joint and international aircraft acquisition programs and related projects; executed an annual budget that reached $ 19 billion and employed

1520-421: Is considerably below that of subsonic aircraft, gunfire and most industrial noise . Duration of sonic boom is brief; less than a second, 100  milliseconds (0.1  second) for most fighter-sized aircraft and 500  milliseconds for the space shuttle or Concorde jetliner. The intensity and width of a sonic boom path depend on the physical characteristics of the aircraft and how it is operated. In general,

1600-455: Is heard. The "length" of the boom from front to back depends on the length of the aircraft to a power of 3/2. Longer aircraft therefore "spread out" their booms more than smaller ones, which leads to a less powerful boom. Several smaller shock waves can and usually do form at other points on the aircraft, primarily at any convex points, or curves, the leading wing edge, and especially the inlet to engines. These secondary shockwaves are caused by

1680-419: Is rare and is well below structural damage thresholds accepted by the U.S. Bureau of Mines and other agencies. The power, or volume, of the shock wave, depends on the quantity of air that is being accelerated, and thus the size and shape of the aircraft. As the aircraft increases speed the shock cone gets tighter around the craft and becomes weaker to the point that at very high speeds and altitudes, no boom

SECTION 20

#1732847573990

1760-529: Is the pressure wave moving down the airplane – it indicates the instruments. And that's what we see around Mach 1. But we don't hear the sonic boom or anything like that. That's rather like the wake of a ship – it's behind us." In 1964, NASA and the Federal Aviation Administration began the Oklahoma City sonic boom tests , which caused eight sonic booms per day over six months. Valuable data

1840-684: The Norden bombsight , internal bomb bay, and power-operated gun turret. The Material Division was re-designated the Material Command in 1942 as the role of the Army Air Force expanded. By 1943, well over 800 major, and thousands of minor research and development projects were in progress at Wright Field. Because many materials were scarce or unavailable during the war, scientists in the Materials Laboratory were involved in developing and testing

1920-499: The boom carpet . Its width depends on the altitude of the aircraft. The distance from the point on the ground where the boom is heard to the aircraft depends on its altitude and the angle α {\displaystyle \alpha } . For today's supersonic aircraft in normal operating conditions, the peak overpressure varies from less than 50 to 500 Pa (1 to 10 psf (pound per square foot)) for an N-wave boom. Peak overpressures for U-waves are amplified two to five times

2000-605: The 1950s; the Boeing B-52 Stratofortress and Lockheed C-130 Hercules . WADC also developed experimental systems, known as the X-series aircraft , in an effort to advance aviation technology and the flight envelope, including the first flight of a vertical takeoff and landing ( VTOL ). WADC programs have also contributed to the space program through the X-20 and Zero-G training. The XQ-6 and XQ-9 target drones were conceived by

2080-634: The ASD. In addition to equipment engineering the ASD worked on process improvement as well by introducing Total Quality Management (TQM). ASD also helped operationalize stealth technology which had been introduced in the 1970s. Work also began on a system of very high speed integrated circuits that would allow advanced avionics architectures to integrate many aircraft subsystems such as weapons delivery, flight controls, and communications into smaller, more reliable subsystems. The Avionics and Flight Dynamics Laboratories coordinated research on an "all-glass" cockpit of

2160-561: The Air Force Flight Test Center, Edwards Air Force Base . Some flight testing continued at Wright-Patterson but was confined to component and instrument testing and other specialized kinds of flight test. The most important addition to postwar flight testing at Wright Field was all-weather testing. It represented the first major attempt to solve the many problems encountered in flying under all weather conditions, both day and night. WADC developed two "workhorse" aircraft during

2240-572: The Materials, Avionics, Aero Propulsion, and Flight Dynamics Laboratories were established and placed under one organization, the Research and Technology Division. Research during this time included examining different materials for aircraft structure, phased-array radar , and improved power plants. During the Vietnam War , ASD set up a special division called Limited War/Special Air Warfare to respond to

2320-450: The N-wave, but this amplified overpressure impacts only a very small area when compared to the area exposed to the rest of the sonic boom. The strongest sonic boom ever recorded was 7,000 Pa (144 psf) and it did not cause injury to the researchers who were exposed to it. The boom was produced by an F-4 flying just above the speed of sound at an altitude of 100 feet (30 m). In recent tests,

2400-628: The Republic test pilots assigned to the program, flew the aircraft once and refused to ever fly it again, claiming "it never flew over 450 knots (830 km/h) indicated, since at that speed, it developed an unhappy practice of 'snaking', apparently losing longitudinal stability". Hendrix also told the formidable Republic project engineer, "You aren't big enough and there aren't enough of you to get me in that thing again". The other test flights were fraught with engine failures, and persistent hydraulic, nose gear, and vibration problems. Test pilot Hank Beaird took

2480-663: The Russian Yakovlev Yak-9 and the British Supermarine Spitfire and de Havilland Mosquito , and enemy aircraft including the German Junkers Ju 88 , Messerschmitt Bf 109 , Focke-Wulf Fw 190 , Messerschmitt Me 262 , and the Japanese A6M Zero . Out of need for a secret location to test experimental aircraft, the flight testing of airframes moved to Rogers Dry Lake, Muroc, California, later named

Republic XF-84H Thunderscreech - Misplaced Pages Continue

2560-583: The Supply Division in 1926 to form the Material Division. The new unit required more space than McCook Field offered, so in an effort to keep the Air Service presence at Dayton , Ohio a local interest group led by John H. Patterson and his son Frederick bought 4,520 acres (18.3 km ) of land, including Wilbur Wright Field and donated it to the Air Service, creating Wright Field . From Wright Field

2640-751: The Wright Aeronautical Development Center but never reached the hardware phase. WADC was inactivated and replaced by the Wright Air Development Division in 1959 then by the Aeronautical Systems Division (ASD) in 1961. That year, the Air Force merged the Air Research and Development Command with the procurement functions of Air Material Command to form the Air Force Systems Command. In 1963,

2720-482: The XF-84H had incredible acceleration but soon its impracticality was discovered. It was unsuited to combat due to the engine's 30-minute warm-up time, but the most serious concerns were vibration generated from the 12-foot diameter propeller and mechanical failures of the prop pitch gearing. The prototypes flew a total of 12 test flights from Edwards, accumulating only 6 hours and 40 minutes of flight time. Lin Hendrix, one of

2800-412: The XF-84H up 11 times, with 10 of these flights ending in forced landings . The XF-84H was almost certainly the loudest aircraft ever built, earning the nickname "Thunderscreech" as well as the "Mighty Ear Banger". On the ground "run ups", the prototypes could reportedly be heard 25 miles (40 km) away. Unlike standard propellers that turn at subsonic speeds, the outer 24–30 inches (61–76 cm) of

2880-474: The XF-84H's crew on the flight line by light signals . After numerous complaints, the Air Force Flight Test Center directed Republic to tow the aircraft out on Rogers Dry Lake , far from the flight line, before running up its engine. The test program did not proceed further than the manufacturer's Phase I proving flights; consequently, no USAF test pilots flew the XF-84H. With the likelihood that

2960-505: The aerodynamics of the model for thruster power. Other models use the efficiency and power of the thruster to allow a less aerodynamic model to achieve greater speeds. A typical model found in United States military use ranges from an average of $ 13 million to $ 35 million U.S. dollars. The pressure from sonic booms caused by aircraft is often a few pounds per square foot. A vehicle flying at greater altitude will generate lower pressures on

3040-426: The air being forced to turn around these convex points, which generates a shock wave in supersonic flow . The later shock waves are somewhat faster than the first one, travel faster, and add to the main shockwave at some distance away from the aircraft to create a much more defined N-wave shape. This maximizes both the magnitude and the "rise time" of the shock which makes the boom seem louder. On most aircraft designs

3120-406: The air, it creates a series of pressure waves in front of the aircraft and behind it, similar to the bow and stern waves created by a boat. These waves travel at the speed of sound and, as the speed of the object increases, the waves are forced together, or compressed, because they cannot get out of each other's way quickly enough. Eventually, they merge into a single shock wave, which travels at

3200-413: The aircraft is usually some distance away. The sound is much like that of mortar bombs , commonly used in firework displays . It is a common misconception that only one boom is generated during the subsonic to supersonic transition; rather, the boom is continuous along the boom carpet for the entire supersonic flight. As a former Concorde pilot puts it, "You don't actually hear anything on board. All we see

3280-614: The aircraft length. The lower this value, the less boom the aircraft generates, with figures of about 1 or lower being considered acceptable. Using this calculation, they found FMs of about 1.4 for Concorde and 1.9 for the Boeing 2707 . This eventually doomed most SST projects as public resentment, mixed with politics, eventually resulted in laws that made any such aircraft less useful (flying supersonically only over water for instance). Small airplane designs like business jets are favored and tend to produce minimal to no audible booms. Building on

Republic XF-84H Thunderscreech - Misplaced Pages Continue

3360-629: The already considerable noise from the subsonic aspect of the propeller and the T40's dual turbine sections, the aircraft was notorious for inducing severe nausea and headaches among ground crews. In one report, a Republic engineer suffered a seizure after close range exposure to the shock waves emanating from a powered-up XF-84H. The pervasive noise also severely disrupted operations in the Edwards AFB control tower by risking vibration damage to sensitive components and forcing air traffic personnel to communicate with

3440-401: The blades on the XF-84H's propeller traveled faster than the speed of sound even at idle thrust, producing a continuous visible sonic boom that radiated laterally from the propellers for hundreds of yards. The shock wave was actually powerful enough to knock a man down; an unfortunate crew chief who was inside a nearby C-47 was severely incapacitated during a 30-minute ground run. Coupled with

3520-503: The boom exposure area is approximately 1 statute mile (1.6 km) for each 1,000 feet (300 m) of altitude (the width is about five times the altitude); that is, an aircraft flying supersonic at 30,000 feet (9,100 m) will create a lateral boom spread of about 30 miles (48 km). For steady supersonic flight, the boom is described as a carpet boom since it moves with the aircraft as it maintains supersonic speed and altitude. Some maneuvers, diving, acceleration, or turning, can cause

3600-430: The characteristic distance is about 40,000 feet (12,000 m), meaning that below this altitude the sonic boom will be "softer". However, the drag at this altitude or below makes supersonic travel particularly inefficient, which poses a serious problem. Supersonic aircraft are any aircraft that can achieve flight faster than Mach 1, which refers to the speed of sound. "Supersonic includes speeds up to five times Mach than

3680-486: The concept of buying a weapon system as a complete, finished package, and reorganized the acquisition cycle into five phases: conceptual, validation, development, production, and deployment. The Air Force viewed this as a more flexible approach; providing oversight, review, and evaluation during each phase. Under this new process the ASD continued enhancing airframes, and developing armaments. The 1980s brought additional funding restraints led to additional reorganization for

3760-416: The current prohibition on supersonic overflight in place in several countries, including the United States. The cracking sound a bullwhip makes when properly wielded is, in fact, a small sonic boom. The end of the whip, known as the "cracker", moves faster than the speed of sound, thus creating a sonic boom. A bullwhip tapers down from the handle section to the cracker. The cracker has much less mass than

3840-407: The division continued to work on aviation advancements including engine design, navigation and communications equipment, cockpit instrumentation, electrically heated flight clothing, and in-flight refueling equipment. The Physiological Research Laboratory led pioneering research in pilot exposure to extremes of speed, pressure, and temperature. Specific advancements of the division in the 1930s include

3920-427: The division's roll shifted from design and building of to acquiring and evaluating aircraft prototypes submitted by the commercial aircraft industry. This left division engineers were left free to concentrate on developing standards unique to military aircraft, reviewing designs, modifying and testing procured machines, and developing ancillary equipment to enhance military aircraft. The Engineering Division merged with

4000-486: The earlier research of L. B. Jones, Seebass, and George identified conditions in which sonic boom shockwaves could be eliminated. This work was extended by Christine. M. Darden and described as the Jones-Seebass-George-Darden theory of sonic boom minimization . This theory, approached the problem from a different angle, trying to spread out the N-wave laterally and temporally (longitudinally), by producing

4080-621: The engine and equipment failures coupled with the inability to reach design speeds and subsequent instability experienced were insurmountable problems, the USAF canceled the program in September 1956. Although The Guinness Book of World Records recorded the XF-84H as the fastest propeller-driven aircraft ever built, with a design top speed of 670 mph (1,080 km/h) (Mach 0.9) and 623 mph (1,003 km/h) (Mach 0.83) during tests, this claim has been disputed. The unofficial record speed

SECTION 50

#1732847573990

4160-468: The event of engine failure, it would automatically swing out into the airstream to provide hydraulic and electrical power. Due to frequent engine problems, as a precaution, the unit was often deployed in flight. After manufacture at Republic's plant in Farmingdale, Long Island, the two XF-84Hs were disassembled and shipped via rail to Edwards Air Force Base for flight testing. First flown on July 22, 1955,

4240-662: The first supersonic airplane, the Bell X-1 . The new independent Air Force created the Air Research and Development Command and placed the principal elements of engineering, the laboratories, and flight testing under Air Development Force, soon renamed Wright Air Development Center' (WADC). It had divisions including Weapons Systems, Weapons Components, Research, Aeronautics, All-Weather Flying, Flight Test, and Materiel, and 12 laboratories. Engineers at Wright Field evaluated captured foreign aircraft during and after World War II. Aircraft brought to Wright Field included allied aircraft such as

4320-450: The focus of the boom. Other maneuvers, such as deceleration and climbing, can reduce the strength of the shock. In some instances, weather conditions can distort sonic booms. Depending on the aircraft's altitude, sonic booms reach the ground 2 to 60  seconds after flyover. However, not all booms are heard at ground level. The speed of sound at any altitude is a function of air temperature. A decrease or increase in temperature results in

4400-627: The fuselage below the wing is shaped according to the area rule . Ideally, this would raise the characteristic altitude from 40,000 feet (12,000 m) to 60,000 feet (from 12,000 m to 18,000 m), which is where most SST aircraft were expected to fly. This remained untested for decades, until DARPA started the Quiet Supersonic Platform project and funded the Shaped Sonic Boom Demonstration (SSBD) aircraft to test it. SSBD used an F-5 Freedom Fighter . The F-5E

4480-706: The future that would allow a pilot, through voice activation, to mix or "enhance" data presented in picture-like symbols on one large TV-like screen. In the post Cold War environment the Air Force again realigned its commands, merging the Air Force Logistics Command and the Air Force Systems Command to form the Air Force Materiel Command (AFMC). ASD was then relabeled the Aeronautical Systems Center (ASC) in 1992 and

4560-418: The greater an aircraft's altitude, the lower the over-pressure on the ground. Greater altitude also increases the boom's lateral spread, exposing a wider area to the boom. Over-pressures in the sonic boom impact area, however, will not be uniform. Boom intensity is greatest directly under the flight path, progressively weakening with greater horizontal distance away from the aircraft flight track. Ground width of

4640-515: The ground because the shock wave reduces in intensity as it spreads out away from the vehicle, but the sonic booms are less affected by vehicle speed. In the late 1950s when supersonic transport (SST) designs were being actively pursued, it was thought that although the boom would be very large, the problems could be avoided by flying higher. This assumption was proven false when the North American XB-70 Valkyrie first flew, and it

4720-454: The horizontal stabilizer/elevator surfaces from propeller wash. The XF-84H was destabilized by the powerful torque from the propeller, as well as inherent problems with supersonic propeller blades. A number of exotic blade configurations were tested before settling on a final design. Various design features were intended to counteract the massive torque, including mounting the left leading edge intake 12 in (30 cm) further forward than

4800-401: The maximum boom measured during more realistic flight conditions was 1,010 Pa (21 psf). There is a probability that some damage—shattered glass, for example—will result from a sonic boom. Buildings in good condition should suffer no damage by pressures of 530 Pa (11 psf) or less. And, typically, community exposure to sonic boom is below 100 Pa (2 psf). Ground motion resulting from the sonic boom

4880-462: The program as an F-84 variant, rather than an entirely new type. With a projected contract for three prototypes, when the US Navy canceled its order, ultimately, the remaining XF-84H prototypes became pure research aircraft built for the Air Force's Propeller Laboratory at Wright-Patterson AFB to test supersonic propellers in exploring the combination of propeller responsiveness at jet speeds. The XF-84H

SECTION 60

#1732847573990

4960-435: The prohibition of routine supersonic flight overland. Although sonic booms cannot be completely prevented, research suggests that with careful shaping of the vehicle, the nuisance due to sonic booms may be reduced to the point that overland supersonic flight may become a feasible option. A sonic boom does not occur only at the moment an object crosses the sound barrier and neither is it heard in all directions emanating from

5040-477: The right, and providing left and right flaps with differential operation. The two prototypes were equally plagued with engine-related problems affecting other aircraft fitted with T40 engines, such as the Douglas A2D Skyshark and North American XA2J Super Savage attack aircraft. A notable feature of the design was that the XF-84H was the first aircraft to carry a retractable/extendable ram air turbine . In

5120-464: The rise time of the over-pressure is sufficiently long. A new metric has emerged, known as perceived loudness, measured in PLdB. This takes into account the frequency content, rise time, etc. A well-known example is the snapping of one's fingers in which the "perceived" sound is nothing more than an annoyance. The energy range of sonic boom is concentrated in the 0.1–100  hertz frequency range that

5200-521: The shock waves forming on the nose of the aircraft at supersonic speeds. Over 50 test flights were performed. Several flights included probing of the shockwaves by a second F-15B, NASA's Intelligent Flight Control System testbed, aircraft 837. Some theoretical designs do not appear to create sonic booms at all, such as the Busemann biplane . However, creating a shockwave is inescapable if it generates aerodynamic lift. In 2018, NASA awarded Lockheed Martin

5280-457: The special requirements dictated by the conflict. Part of this concept was "Project 1559" which provided a means for rapidly evaluating new hardware ideas to determine their usefulness for conducting limited war. Support systems included a highly mobile tactical air control system, disposable parachutes, intrusion alarms for air base defense, and a grenade launcher for the AR-15 rifle. In response to

5360-402: The speed of sound, a critical speed known as Mach 1 , which is approximately 1,192 km/h (741 mph) at sea level and 20 °C (68 °F). In smooth flight, the shock wave starts at the nose of the aircraft and ends at the tail. Because the different radial directions around the aircraft's direction of travel are equivalent (given the "smooth flight" condition), the shock wave forms

5440-406: The speed of sound, or Mach 5." (Dunbar, 2015) The top mileage per hour for a supersonic aircraft normally ranges from 700 to 1,500 miles per hour (1,100 to 2,400 km/h). Typically, most aircraft do not exceed 1,500 mph (2,414 km/h). There are many variations of supersonic aircraft. Some models of supersonic aircraft make use of better-engineered aerodynamics that allow a few sacrifices in

5520-406: The stockpile of aircraft and parts grew the division was able to spend more time finding ways to enhance tools and procedures for pilots. Advancements include things like an electric ignition system, anti-knock fuels, navigational aids, improved weather forecasting techniques, stronger propellers, advancements in aerial photography, and the design of landing and wing lights for night flying. In 1925

5600-437: The strength of the overpressure of a sonic boom. Currently, there are no industry-accepted standards for the acceptability of a sonic boom. However, work is underway to create metrics that will help in understanding how humans respond to the noise generated by sonic booms. Until such metrics can be established, either through further study or supersonic overflight testing, it is doubtful that legislation will be enacted to remove

5680-442: The supersonic object. Rather, the boom is a continuous effect that occurs while the object is traveling at supersonic speeds and affects only observers that are positioned at a point that intersects a region in the shape of a geometrical cone behind the object. As the object moves, this conical region also moves behind it and when the cone passes over observers, they will briefly experience the "boom". When an aircraft passes through

5760-531: The unique climate found in Southeast Asia ASD an evaluation of chemical rain repellents for fighter aircraft and discovered that varieties of repellant applied to cockpit windshields on the ground prior to the flight had a long life and could last several hours, even days. During the early 1970s the Department of Defense became concerned with the rising costs of military procurement and consequently abandoned

5840-520: The vibration. There has been recent work in this area, notably under DARPA's Quiet Supersonic Platform studies. Research by acoustics experts under this program began looking more closely at the composition of sonic booms, including the frequency content. Several characteristics of the traditional sonic boom "N" wave can influence how loud and irritating it can be perceived by listeners on the ground. Even strong N-waves such as those generated by Concorde or military aircraft can be far less objectionable if

5920-431: Was adjusted by changing the blade pitch of the 12 ft (3.7 m) diameter Aeroproducts propeller, consisting of three steel, square-tipped blades turning at a constant speed, with the tips traveling at approximately Mach 1.18 (1,446 km/h). To counter the propeller's torque and " P-factor ", the XF-84H was fitted with a fixed dorsal yaw vane. The tail was changed to a T-tail to avoid turbulent airflow over

6000-423: Was created by modifying a F-84F Thunderstreak airframe, installing a 5,850 hp (4,360 kW) XT40-A-1 turboprop engine in a centrally-located housing behind the cockpit with a long extension shaft to the nose-mounted propeller. The turbine engine also provided thrust through its exhaust; an afterburner which could further increase power to 7,230 hp (5,390 kW) was installed but never used. Thrust

6080-477: Was designed by resident engineers, Alfred V. Verville and Virginius E. Clark . Another aircraft tested was the MB-1, eventually used as the standard mail plane. The division also expanded operations to Wilbur Wright Field. The division also pioneered aviation safety with the use of free-fall parachutes and the development of protective clothing, closed cockpits, heated and pressurized cabins, and oxygen systems. As

6160-524: Was first established under the U.S. Army 's Aviation Section, U.S. Signal Corps in late 1917 at McCook Field . Early on the department's focus was flight testing and training. The department was renamed the Airplane Engineering Division following World War I , it continued its mission of flight testing and training, but also began development and engineering. One early native model, the VCP-1

6240-406: Was found that the boom was a problem even at 70,000 feet (21,000 m). It was during these tests that the N-wave was first characterized. Richard Seebass and his colleague Albert George at Cornell University studied the problem extensively and eventually defined a " figure of merit " (FM) to characterize the sonic boom levels of different aircraft. FM is a function of the aircraft's weight and

6320-534: Was gathered from the experiment, but 15,000 complaints were generated and ultimately entangled the government in a class-action lawsuit, which it lost on appeal in 1969. Sonic booms were also a nuisance in North Cornwall and North Devon in the UK as these areas were underneath the flight path of Concorde. Windows would rattle and in some cases, the " torching " (masonry mortar underneath roof slates) would be dislodged with

6400-511: Was modified with a highly refined shape which lengthened the nose to that of the F-5F model. The fairing extended from the nose back to the inlets on the underside of the aircraft. The SSBD was tested over two years culminating in 21 flights and was an extensive study on sonic boom characteristics. After measuring the 1,300 recordings, some taken inside the shock wave by a chase plane , the SSBD demonstrated

#989010