Fifty-eight years ago this month, the USAF/North American F-107A aircraft flew for the first time. Interestingly, the Mach 2-capable fighter-bomber prototype went supersonic on its maiden flight.
The F-107A was designed, developed and tested by North American Aviation (NAA) in the mid-1950′s. With it, the contractor hoped to satisfy Tactical Air Command’s (TAC) need for a front line fighter-bomber. However, Republic Aircraft also had a candidate for the same role; the F-105 Thunder Chief.
The competition between Republic and North American for the TAC fighter-bomber production contract has a story of its own. Suffice it to say here that the competitive effort was (1) extremely close and (2) tinged with political intrigue. In the end, Republic Aircraft reaped the spoils of victory.
Although the F-107A came out on the short end of the stick in the TAC fighter-bomber competition, such did not imply an inferiority in fulfilling the intended role. Indeed, like the Northtrop YF-23′s loss to the General Dynamics YF-22 in the ATF competition of the early 1990′s, North American’s failure to get the nod with the F-107A is still a subject of passionate debate.
The F-107A measured 60.8 feet in length and had a wing span of 36.6 feet. Gross take-off weight was around 41,000 pounds. The aircraft was powered by a single Pratt and Whitney YJ75-P-11 turbojet that produced 15,500 pounds of thrust in military power and 23,500 pounds of thrust in full afterburner.
F-107A longitudinal control was provided by an all-flying horizontal tail. Similarly, an all-flying vertical tail was employed for directional control. Lateral control was provided by a unique 3-segment spoiler-deflector system mounted on each wing. The aircraft was also configured with inboard flaps and leading edge slats for lift augmentation at low speeds.
A unique and prominent feature of the F-107A was its dorsal-mounted air induction system known as the Variable-Area Inlet Duct (VAID). Internally, this unit incorporated a system of adjustable ramps to efficiently decelerate and compress freestream prior to entering the engine compressor face. Ramp deflection scheduling with Mach number was controlled automatically. Ramp boundary layer bleed air was vented from the top of the VAID.
The F-107A carried weapons externally. In addition to wing pylon-mounted stores, the aircraft was designed to carry a single “special weapon” from a semi-submerged recess located on the aircraft ventral centerline. The term “special weapon” means that it was a tactical nuclear bomb. The Sandia-developed store could also be used in combination with a special saddle fuel tank to extend aircraft range.
A total of three (3) F-107A aircraft were built and flown. USAF-assigned tail numbers include 55-5118, 55-5119 and 55-5120. On Monday, 10 September 1956, the No. 1 ship (55-5118) took-off from Edwards Air Force Base on its first flight. NAA Chief Test Pilot Robert Baker, Jr. was at the controls. The aircraft attained a maximum Mach number of 1.03 in a 43 minute flight test.
The F-107A could really scream. The type had a maximum climb rate of around 40,000 feet per minute in full afterburner. The max demonstrated Mach number attained by the F-107A was Mach 2.18. Program engineers estimated that by increasing the inlet area slightly, the F-107A was capable of reaching roughly Mach 2.4.
The trio of F-107A aircraft flew 272 flight tests totalling 176.5 hours. Included in this testing was successful separation of a special store prototype at Mach 2. Test pilots of note who flew the F-107A included XB-70A pilot Al White and X-15 pilots Scott Crossfield, Bob White, Jack McKay and Forrest Peterson.
Though it never became a production aircraft, the F-107A contributed in significant ways to aviation progress. Indeed, many future aircraft would greatly benefit from F-107A flight control and air induction technology including the A-5 Vigilante, XB-70A, A-12, SR-71, YF-12A and F-15.
The F-107A was the last of NAA’s fighter aircraft which includes such notables as the P-51 Mustang, the F-86 Sabre and the F-100 Super Sabre. While the F-107A has often been referred to in print as the Ultra Sabre, Ultimate Sabre, Super Super Sabre or such, it was never officially assigned a nickname. Alas, there was never an XF-107A or YF-107A designation either. North American Aviation’s TAC fighter-bomber candidate was simply known as the F-107A.
Today, the No. 1 F-107A (55-5118) is displayed at the Pima Air and Space Museum (PASM) in Tucson, Arizona. The No. 2 ship (55-5119) resides at the USAF Museum at Wright-Patterson Air Force Base in Dayton, Ohio. The No. 3 airplane (55-5120) no longer exists as it was relegated to the status of a fire fighting prop and ultimately destroyed in that role sometime in 1961 or 1962.
Forty-nine years ago this month, NASA astronauts Leroy Gordon Cooper and Charles M. “Pete” Conrad set a new spaceflight endurance record during the flight of Gemini 5. It was the third of ten (10) missions in the historic Gemini spaceflight series. The motto for the mission was “Eight Days or Bust”.
The purpose of Project Gemini was to develop and flight-prove a myriad of technologies required to get to the Moon. Those technologies included spacecraft power systems, rendezvous and docking, orbital maneuvering, long duration spaceflight and extravehicular activity.
The Gemini spacecraft weighed 8,500 pounds at lift-off and measured 18.6 feet in length. Gemini consisted of a reentry module (RM), an adapter module (AM) and an equipment module (EM).
The crew occupied the RM which also contained navigation, communication, telemetry, electrical and reentry reaction control systems. The AM contained maneuver thrusters and the deboost rocket system. The EM included the spacecraft orbit attitude control thrusters and the fuel cell system. Both the AM and EM were used in orbit only and discarded prior to entry.
Gemini-Titan V (GT-5) lifted-off at 13:59:59 UTC from LC-19 at Cape Canaveral, Florida on Saturday, 21 August 1965. The two-stage Titan II launch vehicle placed Gemini 5 into a 189 nautical mile x 87 nautical mile elliptical orbit.
A primary purpose of the Gemini 5 mission was to stay in orbit at least eight (8) days. This was the minimum time it would take to fly to the Moon, land and return to the Earth. Other goals of the Gemini 5 mission were to test the first fuel cells, deploy and rendezvous with a special rendezvous pod and conduct a variety of medical experiments.
Despite fuel cell problems, electrical system anomalies, reaction control system issues and the cancellation of various experiments, Gemini 5 was able to meet the goal of an 8-day flight. But it wasn’t easy. The last days of the mission were especially demanding since the crew didn’t have much to do. Pete Conrad called his Gemini 5 experience “8 days in a garbage can.”
On Sunday, 29 August 1965, Gemini 5 splashed-down in the Atlantic Ocean at 12:55:13 UTC. Mission elapsed time was 7 days, 22 hours, 55 minutes and 13 seconds. A new spaceflight endurance record.
Gemini 5 was Gordon Cooper’s last spaceflight. Cooper left NASA due to a deteriorating relationship with management. Pete Conrad flew three (3) more times in space. In particular, he commanded the Gemini 11, Apollo 12 and Skylab I missions. Indeed, Conrad’s Apollo 12 experience made him the third man to walk on surface of the Moon.
Sixty-one years ago today, the USN/Douglas D-558-II Skyrocket soared to an unofficial world record altitude of 83,235 feet. The Skyrocket’s record altitude mission was piloted by USMC test pilot and World War II triple-ace Lieutenant Colonel Marion E. Carl.
The D-558-II was a United States Navy (USN) X-aircraft and first flew in February of 1948. It was contemporaneous with the USAF/Bell XS-1. The aircraft measured 42 feet in length with a wing span of 25 feet. Maximum take-off weight was 15,266 pounds. Douglas manufactured a trio of D-558-II aircraft (Bureau No.’s 37973, 37974 and 37975).
The original version of the swept-wing D-558-II had both rocket and turbojet propulsion. The latter system provided a ground take-off capability. However, like other early X-aircraft such as the XS-1, X-1A, X-2 and X-15), the D-558-II achieved maximum performance through the use of a mothership and rocket power alone.
On Friday, 21 August 1953, D-558-II (Bureau No. 37974; NACA 144) was carried to a drop altitude of approximately 30,000 feet over Edwards Air Force Base by a USN P2B-1S launch aircraft. Following drop, Carl fired his LR-8 rocket motor and executed a pull-up in an effort to extract maximum altitude from the D-558-II. Carl hit a maximum Mach number of 1.728 and exceeded the existing altitude by about 3,800 feet.
Flying the D-558-II to altitudes beyond 65,000 feet required Carl to wear a full-pressure suit. The versions available to test pilots in the early 1950′s were crude by today’s standards. They were extremely uncomfortable and very confining. The pilot had to use reverse breathing to supply adequate oxygen to the lungs.
Reverse breathing involves the inhalation of air under pressure wherein oxygen is forced into the lungs by simply opening the mouth. One then has to make a conscious effort to exhale against that pressure in order rid the lungs of carbon dioxide. This unnatural breathing process had to be practiced by a pilot until it became second nature.
Flying the D-558-II (and other 1950′s high-speed research aircraft such as the X-1, X-1A and X-2) to extreme altitude was a sporty proposition. These aircraft exhibited disturbing lateral-directional control characteristics at low dynamic pressure. None of the early X-planes were configured with a 3-axis reaction control system. Control had to be maintained solely by aerodynamic means.
Marion Carl’s altitude mark in the D-558-II would stand until September of 1956 when USAF Captain Iven Kincheloe flew the USAF/Bell X-2 to an altitude of 126,200 feet. Today, the record-setting D-558-II (NACA 144) is displayed at the National Air and Space Museum in our Nation’s capital.
Marion Carl went on to serve his country until he retired from the Marine Corps in 1973 after having attained the rank of Major General. Sadly, Carl was shot to death in 1998 at the age of 82 as he defended his wife Edna from a home invader. A true American hero, Marion E. Carl was buried with full military honors at Arlington National Cemetery.
Fifty-four years ago this month, the United States successfully launched the Echo 1A passive communications satellite into Earth orbit. The 100-foot diameter balloon was among the largest objects ever to orbit the Earth.
A plethora of earth-orbiting communication satellites provide for a global connectivity that is commonplace today. Such was not always the case. Roll the clock back a half-century and we find that a global communications satellite system was just a concept. However, keen minds would soon go to work and provide mankind with yet another tangible space age benefit.
Communications satellites are basically of two types; passive and active. A passive communications satellite (PCS) simply reflects signals sent to it from a point on Earth to other points on the globe. An active communications satellite (ACS) can receive, store, modify and/or transmit Earth-based signals.
The earliest idea for a PCS involved the use of an orbiting spherical balloon. The balloon was fabricated from mylar polyester having a thickness of a mere 0.5 mil. The uninflated balloon was packed tightly into a small volume and inserted into a payload canister preparatory to launch. Once in orbit, the balloon was released and then inflated to a diameter of 100 feet.
The system described above materialized in the late 1950′s as Project Echo. The Project Echo satellite was essentially a huge spherical reflector for transcontinental and intercontinental telephone, radio and television signals. The satellite was configured with several transmitters for tracking and telemetry purposes. Power was provided by an array of nickel-cadmium batteries that were charged via solar cells.
Echo 1 was launched from Cape Canaveral, Florida on Friday, 13 May 1960. However, the launch vehicle failed and Echo 1 never achieved orbit. Echo 1A (sometimes referred to as Echo 1) lifted-off from Cape Canveral’s LC-17A at 0939 UTC on Friday, 12 August 1960. The Thor Delta launch vehicle successfully placed the 166-lb satellite into a 820-nm x 911-nm orbit.
An interesting characteristic of the Echo satellite was the large oscillation in the perigee of its orbit (485 nm to 811 nm) over several months. This was caused by the influences of solar radiation and variations in atmospheric density. While these factors are just part of the earth-orbital environment, their effects were much more noticeable for Echo due to the type’s large surface area-to-weight ratio.
Echo 1A orbited the Earth until it reentered the Earth’s atmosphere on Saturday, 25 May 1968. Echo 2 was a larger and improved version of Echo 1A. It measured 135-feet in diameter and weighed 547-lb. Echo 2 orbited the Earth between January of 1964 and June of 1969. Other than the Moon, both satellites were the brightest objects observable in the night sky due to their high reflectivity.
The Echo satellites served their function admirably. For a time, they were quite a novelty. However, progress on the ACS scene quickly relegated the PCS to obselescence. Today, virtually all communication satellites are of the ACS variety.
Sixty-three years ago today, a United States Navy Viking rocket soared to an altitude of 136 miles. In doing so, it eclipsed the previous single stage altitude record of 114 miles set by a captured German V-2 rocket on Tuesday, 17 December 1946. The mission was part of the Navy’s 12-flight Viking Rocket flight test series conducted between May 1949 and February 1955.
At 1659 UTC on Tuesday, 07 August 1951, Viking No. 7 was fired from LC-33 at White Sands Proving Ground (WSPG), New Mexico. Burnout velocity was 5,865 feet per second following a rocket motor burn time of 72 seconds. Viking No. 7 weighed 10,730 pounds at lift-off (roughly 8,000 pounds of which were propellants) and carried a scientific payload of 394 pounds.
Viking No. 7 was the last of the early Viking rocket configurations which measured 49-feet in length and had a diameter of 32-inches. Starting with Viking No. 8, the rocket’s airframe was modified to carry more propellants for greater altitude performance and measured 42-feet (length) by 45-inches (diameter). This modification allowed Viking No. 11, flown from WSPG on Monday, 24 May 1954, to capture the all-time Viking altitude record of 158 miles.
Although almost forgotten today, the Viking Rocket Program played a vital role in the history of American rocketry. Viking was the first large, liquid-fueled rocket developed by the United States. It’s rocket motor generated 21,000 pounds of lift-off thrust and employed an innovative two-axis gimbal system for pitch and yaw control. Fin-mounted reaction jets provided roll control.
The Viking Rocket Program provided a tremendous amount of scientific data about Earth’s atmospheric properties such as pressure, temperature, density, winds, and composition. Additionally, the Viking rocket formed the technological basis for a number of 1950′s launch vehicle systems including the Navy’s Vanguard satellite launcher and the USAF Titan ICBM.
Fifty-seven years ago this month, the United States successfully conducted the only live-fire test of the only known nuclear-armed air-to-air missile ever developed by the West. The test took place in the skies over the Nuclear Test Site located at Yucca Flats, Nevada.
The Cold War between the Soviet Union and the United States gave rise to the development of myriad nuclear weapons. Both superpowers ultimately relied on a triad of platforms, consisting of bombers, missiles and submarines, to deliver nuclear ordnance. Each side used these same types of platforms in a defensive role as well.
The United States employed land-based interceptor aircraft for defending against the Soviet bomber threat. These aircraft would go out to engage and destroy Soviet bomber groups before the latter could penetrate US airspace. The weapon of choice for taking out the bombers was the air-to-air missile.
The most fearsome of air-to-air missiles was armed with a nuclear warhead. The idea was simple. A defending aircraft would fire the nuclear-armed missile into a bevy of Soviet bombers. Detonation of the warhead would in theory destroy an entire bomber group with a single atomic blast.
The Douglas Aircraft Company produced just such a missile for the United States Air Force in the mid-1950′s. The subject missile was originally known as the MB-1 Genie (aka Bird Dog, Ding-Dong, and High Card). The type’s 1.5 kiloton nuclear device had a blast radius on the order of 1,000 feet.
The Genie measured 9.67 feet in length and had a nominal diameter of 17.5 inches. Firing weight was 822 pounds. Genie’s Thiokol SR49-TC-1 solid rocket motor had a rated thrust of 36,500 pounds. The resulting high thrust-to-weight ratio allowed the missile to quickly accelerate to the target. Genie had a top Mach number of 3.3 and a range of slightly over 6 miles.
Genie was carried by the top USAF interceptor aircraft of its day; the Northrop F-89 Scorpion, McDonnell F-101B VooDoo and Convair F-106 Delta Dart. The missile was unguided. That is, Genie was simply a point and shoot weapon. The warhead would detonate only after rocket motor burnout. This delay permitted the carrier aircraft to quickly depart the area following launch.
The only in-flight detonation of a Genie warhead occurred during the summer of 1957 as part of Operation Plumbbob. This program was series of nuclear weapons tests conducted from May to October of the subject year at the Yucca Flats Nuclear Test Site in Nevada.
At 1400 UTC on Friday, 19 July 1957, USAF Captain Eric Hutchison fired a single Genie missile from his Northrop F-89J aircraft. The missile’s W25 warhead detonated at 15,000 feet above ground level shortly after rocket motor burnout. A group of USAF officers was positioned directly below the air burst to prove that the missile could be used over populated areas. The men were reported to be unharmed.
Genie was never fired in anger. Approximately 3,150 missiles were produced by the time Thiokol closed down the production line in 1963. This production run included a number of improved variants known as the MB-1-T, ATR-2A, AIR-2A and AIR-2B. Genie ultimately served with both the USAF and the Canadian Air Force. It was withdrawn from service in 1985.
Forty-five years ago yesterday, the United States of America first landed men on the surface of the Moon.
The Apollo 11 Lunar Module Eagle landed in Sea of Tranquility region of the Moon on Sunday, 20 July 1969 at 20:17:40 UTC. Less than seven hours later, astronauts Neil A. Armstrong and Edwin E. Aldrin, Jr. became the first human beings to walk upon Earth’s closest neighbor. Fellow crew member Michael Collins orbited high overhead in the Command Module Columbia.
As Apollo 11 commander, Neil A. Armstrong was accorded the privilege of being the first man to step foot upon the Moon. As he did so, Armstrong spoke these words: “That’s one small step for Man; one giant leap for Mankind”. He had intended to say: “That’s one small step for ’a’ man; one giant leap for Mankind”.
Armstrong and Aldrin explored their Sea of Tranquility landing site for about two and a half hours. Total lunar surface stay time was 22 hours and 37 minutes. The Apollo 11 crew left a plaque affixed to one of the legs of the Lunar Module’s descent stage which read: “Here Men From the Planet Earth First Set Foot Upon the Moon; July 1969, A.D. We Came in Peace for All Mankind”.
Following a successful lunar lift-off, Armstrong and Aldrin rejoined Collins in lunar orbit. Approximately seven hours later, the Apollo 11 crew rocketed out of lunar orbit to begin the quarter million mile journey back to Earth. Columbia splashed-down in the Pacific Ocean at 16:50:35 UTC on Thursday, 24 July 1969. Total mission time was 195 hours, 18 minutes, and 35 seconds.
With completion of the flight of Apollo 11, the United States of America fulfilled President John F. Kennedy’s 25 May 1961 call to land a man on the Moon and return him (them) safely to the Earth before the decade of the 1960′s was out. It had taken 2,982 demanding days and much national treasure to do so.
Mission Accomplished, Mr. President.
Forty-five years ago today, the epic flight of Apollo 11, the first mission to land men on the Moon, began with launch from the Kennedy Space Center (KSC) at Merritt Island, Florida. Nearly 1-million people gathered around America’s famous space complex to witness the historic event. An estimated 1-billion viewers worldwide watched the proceedings on television.
The names of the Apollo 11 crew are now legend: Mission Commander Neil A. Armstrong, Lunar Module Pilot Edwin E. Aldrin, Jr., and Command Module Pilot Michael Collins. Each astronaut was making his second spaceflight.
The overall Apollo 11 spacecraft weighed roughly 100,000 pounds and consisted of 3 major components: Command Module, Service Module, and Lunar Excursion Module (LEM). Out of American history came the names used to distinguish two of these components from one another. The Command Module was named Columbia, the feminine personification of America, while the Lunar Excursion Module received the appellation Eagle in honor of America’s national bird.
The Apollo-Saturn V launch stack measured 363-feet in length, had a maximum diameter of 33-feet, and weighed 6.7-milllion pounds at ignition of its five F-1 engines. The vehicle rose from the Earth on 7.7-million pounds of lift-off thrust.
The acoustic energy produced by the Saturn’s first stage propulsion system was unlike anything in common experience. The sound produced was like intense, continuous thunder even miles away from the launch point. Ground and structure shook disturbingly and a person’s lungs vibrated within their chest cavity.
Lift-off of Apollo 11 (AS-506) from KSC’s LC-39A occurred at 13:32 UTC on Wednesday, 16 July 1969. The target for the day’s launch, the Moon, was 218,096 miles distant from Earth. It took 12 seconds just for the massive Apollo 11 launch vehicle to clear the launch tower. However, a scant 12 minutes later, the Apollo 11 spacecraft was safely in low earth orbit (LEO) traveling at 17,500 miles per hour.
Following checkout in earth orbit, trans-lunar injection, and earth-to-moon coast, Apollo 11 entered lunar orbit nearly 76 hours after lift-off. Now, the big question: Would they make it? Even Apollo 11′s Command Module Pilot, Michael Collins, estimated that the chance of a successful lunar landing on the first attempt was only 50/50. The answer would soon come. History’s first lunar landing attempt was now only 24 hours away.
Fifty years ago this month, the United States abandoned a 7-year effort to develop a nuclear-armed, supersonic cruise missile. The joint USAF-AEC program was known as Project Pluto. The centerpiece of this program was the nuclear-fueled, ramjet-powered Supersonic Low-Altitude Missile (SLAM).
The 1950′s saw the development of myriad aircraft, missile and submarine concepts designed for delivery of nuclear weaponry over strategic distances. This developmental activity was driven by the escalating Cold War between the United States and the Soviet Union. In addition to weapons, the power of the atom was also considered for propulsion applications during this era.
SLAM was perhaps the most fearsome weapon ever conceived. The missile was designed to deliver as many as 26 nuclear bombs over the Soviet Union in a single mission. It would do this while flying at Mach 3 and less than 1,000 feet above ground level. SLAM’s shock wave overpressure alone (162 dB) would devastate structures and people along its flight path. And, as if that were not enough, the type’s nuclear-fueled ramjet would continuously spew radiation-contaminated exhaust all over the countryside.
The SLAM airframe was huge. It measured 88 feet in length, nearly 6 feet in diameter and weighed 61,000 pounds at launch. The vehicle would be fired from a ground-based launch site and accelerated to ramjet takeover speed by a trio of jettisionable rocket boosters. The nuclear-fueled ramjet was rated at 35,000 pounds of thrust.
To find its way to the target area(s), the Ling-Temco-Vought (LTV) SLAM would use a guidance system known today as TERCOM – Terrain Contour Matching. At a target, SLAM would eject an atomic warhead upwards from its payload bay. The resulting lofted trajectory gave SLAM time to depart the hot target area prior to weapon detonation. Following completion of its mission, the missile would then ditch itself by diving into a deep ocean graveyard.
The heart of the Project Pluto missile was the nuclear-fueled ramjet. An unshielded nuclear reactor, code named TORY, was devised, built and successfully tested. Testing was conducted at a special-purpose test site in Nevada. In its Tory II-C configuration, the SLAM ramjet produced over 500 megawatts of power in 5 minutes of continuous operation during a test conducted in May of 1964.
SLAM’s nap-of-the-earth, supersonic flight profile would subject the airframe to terrific airloads, vibrations and temperatures. The Project Pluto team successfully devised structural and thermal material solutions to handle the daunting flight environment. In addition, nuclear-hardened electronics and flight controls were successfully developed.
From a technological standpoint, Project Pluto proved to be entirely viable. However, doubts about its implementation started to arise as flight testing of the nuclear-powered missile was seriously considered. Where do you flight-test a radiation-spewing missile? What happens if you can’t turn-off the reactor? What do you do if the guidance system fails? Where do you dispose of the missile after a flight test? These and other disturbing questions began to trouble program officials.
Coupled with the above practical concerns of SLAM flight testing were growing political and mission obsolesence issues. Pentagon officials ultimately deemed Project Pluto as being highly provocative to the Soviet Union in the sense that the communist super power might feel compelled to develop their own SLAM. Further, American missilery was quickly developing to the point where ICBM-delivered warheads would do the job and at a lower per-unit cost.
So it was that on Wedneday, 01 July 1964, Project Pluto was canceled after 7 years of fruitful development. While no airframe was ever built and tested, SLAM technology was applied to a host of subsequent aerospace vehicle developments.
SLAM would truly have been “The Missile From Hades” had it matured to the point of flight. Indeed, the ethical issues concerning the missile’s use were quite sobering. And, owing to Murphy’s Law and its many corollaries, the chances for unintended catastrophe were high as well. Despite the allure of this ”technically sweet” solution to a national defense problem, the decision to cancel Project Pluto was ultimately the only correct course to follow.
Fifty-nine years ago this month, the USAF/Republic XF-84H experimental turboprop fighter took to the air for the first time. The test hop originated from and recovered at Edwards Air Force Base, California.
The turbojet-powered XF-84H was a variant of Republic Aviation’s F-84 Thunderstreak. An Allison XT40-A-1 turboprop engine, rated at 5,850 hp, served as the power source for this novel aircraft. The XT40 drove a variable-pitch, 3-blade, 12-foot diameter propeller at 3,000 rpm. The propulsion system’s thrust level was changed by varying blade pitch.
Owing to its high rotational speed and large diameter, the outer 2 feet of the XF-84H propeller saw supersonic velocities. The shock waves that emanated from the prop produced a deafening wall of sound. The extreme sound level produced intense nausea and raging headaches in ground crewmen. As a result, the XF-84H was dubbed the Thunderscreech.
The prop wash from the aircraft’s powerful turboprop necessitated the use of a T-tail to keep the horizontal tail and elevator in clean air flow. The engine’s extreme torque was partially countered by incorporating differential deflection on the left and right wing flaps and by placement of the left wing root air intake a foot ahead of the right intake.
A pair of XF-84H prototype aircraft (S/N 51-17059 and S/N 51-17060) was built by Republic Aviation. The first flight of an XF-84H took place on Friday, 22 July 1955 at Edwards Air Force. The flight was made by Republic test pilot Henry G. “Hank” Beaird, Jr. in Ship No. 1 (S/N 51-17059). The flight was cut short by a forced landing.
A total of twelve (12) test flights were made in the two Thunderscreech prototypes; eleven (11) in Ship No. 1 and one (1) in Ship No. 2. Total flight time accumulated by these experimental airframes was 6 hours and 40 minutes. The majority of flights experienced forced landings for one reason or another.
The XF-84H suffered from reduced longitudinal stability and poor handling qualities. The aircraft was also plagued by frequent engine, hydraulic system, nose gear and vibration problems. Faced with the type’s obvious non-viability, USAF opted to cancel the XF-84H Program in September of 1956.
Historical records indicate that the XF-84H reached a top speed of 520 mph during its brief flight test life. This mark was a full 120 mph short of the aircraft’s design speed. Nonetheless, the XF-84H held the speed record for single-engine prop-driven aircraft until Monday, 21 August 1989. On that date, a specially modified Grumman F8F Bearcat established the existing record of 528.33 mph.
