Quest for Performance: The Evolution of Modern Aircraft
Chapter 11: Early Jet Fighters
Through the Transonic Range
[299] Many knowledgeable engineers once thought that reasonably safe and controllable flight past Mach 1.0 was highly unlikely, if not completely impossible. By the mid-1940's, much had been written in the popular press about the so-called "sonic barrier." That an aircraft could successfully fly past Mach 1.0, however, was convincingly demonstrated on October 14, 1947 by Captain Charles E. Yeager flying the rocket-propelled Bell X-1 research airplane. This historic event set the stage for an intensive research and development effort, which had as its objective the production of jet fighters capable of passing through Mach 1.0 and into the once forbidden supersonic speed range. During this stimulating time period, from the late 1940's to the mid-1950's, a number of supersonic fighter aircraft were developed that later served in the United States air forces as well as those of a number of other countries. Some of these aircraft types saw extensive action in the Vietnam conflict, and some are still in service.
To put the firs t-generation supersonic fighters in proper perspective, these aircraft should be thought of as basically high-performance subsonic machines with design features that allowed flight through Mach 1.0 and at supersonic speeds for very brief periods of time. In no sense were they designed for sustained cruising flight at supersonic speeds. The following considerations of drag, thrust, and specific fuel consumption readily show this to be so. As the supersonic fighter accelerated from high-subsonic speed to supersonic speed, the drag coefficient usually increased by a factor of 2 or more. The increase in actual drag force, however, was much larger than that of the coefficient. For example, the dynamic pressure at Mach 2.0 for a given altitude is about five times that at Mach 0.9 for the same altitude. Thus, the actual drag force and the thrust required to balance this force in steady flight increases by a factor of at least 10 as the Mach number increases from 0.9 to 2.0. Further, the specific fuel consumption (pounds of fuel per pound of thrust per unit time) of the afterburning turbojet at Mach 2.0 is two to three times the value of that for the nonafterburning engine at subsonic Mach numbers. At Mach 2.0 the actual fuel consumption per unit time may accordingly be 20 to 30 times that at Mach 0.9. To compound the problem further, the time required by the early supersonic [300] jet fighters to accelerate from Mach 0.9 to Mach 2.0 was usually in the range from 3 to 10 minutes depending on the aircraft, engine, and altitude. The long acceleration times, which resulted from the relatively small margin between thrust and drag, when coupled with the high fuel consumption per unit time during acceleration, severely restricted the time available for cruising flight at maximum Mach number. The range available to fighter aircraft operating at supersonic speeds was accordingly quite limited. For these reasons, even modern supersonic fighters spend most of their flying lifetime at subsonic speeds. Most of the design features of the supersonic fighters, however, also increased the operational capability of these aircraft at high-subsonic speeds. Accordingly, these aircraft should really be thought of as highly effective subsonic fighters with a supersonic dash capability that is useful and important in certain military missions. For example, a short burst of supersonic speed might be necessary in overtaking or escaping from a hostile aircraft or in avoiding antiaircraft fire in a bombing run at low altitude.
The supersonic fighters developed in the 1950's shared a number of important technical features. All the aircraft had afterburning engines that provided a substantial boost in thrust as well as fuel consumption throughout the speed range. A large increase in thrust as the Mach number increased was also characteristic of the afterburning engines. Both fixed- and variable- geometry inlets were used. Power-operated control surfaces with artificial "feel" provided to the pilot were standard features; and, in some cases, rudimentary stability augmentation was incorporated to improve the inherent stability characteristics of the aircraft. The increased control effectiveness of the all-moving horizontal tall at supersonic and transonic speeds dictated its use rather than the more conventional elevator. Wing thickness ratios fell in the range from about 7 to 4 percent. By comparison, the thickness ratio of a typical World War II propeller-driven fighter was about 14 percent. Wing planforms were usually of the swept or delta type, although one fighter of this period had a straight wing.
By the end of 1956, prototypes of seven supersonic fighters for the USAF had been developed and flown. Six of these aircraft reached production status and operational service. In the same period, two supersonic fighters were developed for the Navy. To illustrate interesting design features of supersonic fighters developed during the 1950's, four USAF and one Navy aircraft, all capable of supersonic flight, are briefly discussed in the following paragraphs. Some of the physical and [301] performance characteristics of these aircraft are given in table V. Where two values of engine thrust are given (16 000/10 000, for example), the first value indicates the sea-level static thrust with maximum afterburning and the second value indicates maximum thrust without afterburning. Also note that the values of zero-lift drag coefficient CD,O, drag area f, and maximum lift-drag ratio (L/D)max are for subsonic speeds. As mentioned, the values Of CD,O increased by a factor of 2 to 3 as the Mach number increased from subsonic to supersonic values. The maximum lift-drag ratio at supersonic speeds for the fighter aircraft discussed were usually in the range from 3 to 4.
A glance at the data in table V indicates that the weights, wing loadings, and thrust loadings of the supersonic fighters were usually greater than those of earlier subsonic machines. The afterburning supersonic fighters were designed to achieve both their maximum speed and corresponding Mach number at high altitudes. The maximum speed at low altitudes was usually restricted to values near Mach 1.0 by high drag was well as by airframe or engine limitations imposed by the high temperatures and dynamic pressures encountered in low-level flight at high speeds. At high altitudes, the maximum speeds of most of the aircraft approached or exceeded Mach 2.0.
The Century Series Fighters
Because the first of their number was designated the F-100, the USAF supersonic fighters developed in the 1950's were aptly christened with the appellation "Century Series." Design studies of an F-86 equipped with a thin 45° swept wing, known as the Sabre 45, marked the genesis of the F-100; but the aircraft that finally emerged with that designation was an entirely new machine.
First flight of the F-100, the world's first fighter capable of sustained supersonic speeds in level flight, took place on May 25, 1953. Views of the F-100, known as the Super Sabre, are shown in figures 11.11 and 11.12. The low-mounted wing had a sweepback angle of 45° a taper ratio of 0.25, and an airfoil-section thickness ratio of about 7 percent. Like the wing of its ancestor the F-86, the leading edge was equipped with automatic slats for stall control and the trailing edge incorporated plain flaps. Location of the ailerons mounted a short distance inboard of the tip reduced adverse wing twisting due to aileron deflection. (Under conditions of high dynamic pressure, adverse wing twist due to aileron deflection can become so large that, on some...

photo of F-100
[302Figure 11.11 - Alorth American F-100 Super Sabre single-engine jet fighter. [ukn via AAHS]


....aircraft, roll takes place in a direction opposite to that intended. This condition is known as aileron reversal.)

The low-mounted horizontal tail of the F-100 is clearly shown in figure 11.12. As discussed in chapter 10, this tail position assists in preventing pitch-up. As a further assist to stall control, most models of the F- 100 had wing fences. Also shown in figure 11. 12 is the variable-area nozzle necessary for efficient operation of the afterburning engine; the nozzle is in the nonafterburning configuration in figure 11. 12. The petals of the nozzle open to a larger diameter for afterburning. The boxlike structure on the vertical tail about one-third of the span from the tip, evident in figure 11. 12, housed a radar warning antenna.
The oblong nose inlet shown in figure 11. 11 provides an immediate recognition feature of the F-100 series of aircraft. As compared with a circular inlet, the oblong design provides better pilot visibility over the nose and, since the duct passes under the pilot's seat, the vertical dimension of the fuselage is reduced at this location. No area ruling was incorporated in the design of the F-100.
All new aircraft encounter problems of varying degrees of seriousness, particularly in new and largely unexplored regimes of flight or with new configuration concepts, and the F-100 was no exception. An unanticipated problem was encountered during flight tests of the F-100 that resulted in loss of the aircraft as well as its well-known North American test pilot. Compared with piston-engine fighters and earlier jets, aircraft such as the F-100 had much higher values of the ratio of....

View of F100 with service steps near cockpit
[303Figure 11. 12 - Rear view of North American F- 100 Super Sabre single-engine jet fighter. [USAF via Martin Copp]

....lengthwise to spanwise mass. As a consequence, a gyroscopic couple that caused large yaw excursions occurred during dive pull-out maneuvers accompanied by large rolling velocities. During the performance of such maneuvers in an early model F-100, the angle of vaw became so large that the aerodynamic loads on the vertical tall exceeded its structural strength and the tall separated from the aircraft. A larger and stronger vertical tail solved the problem on the F-100. All new fighter aircraft under development at that time, however, were carefully scrutinized for possible "rolling pull-out" problems; this maneuver is now a standard one that must be analyzed on all new fighter designs.
Maximum speed of the F-100D was 927 miles per hour, or Mach 1.39, at 35 000 feet; at sea level, the maximum speed was just below the sonic value. Maximum sea-level rate of climb was 22 400 feet per minute, or about three times that of the F-86, and the service ceiling was 51 300 feet. With a lift-drag ratio of 13.9 at subsonic speeds, the F-100 had a ferry range of 1971 miles. According to reference 200, the combat radius was 599 miles with maximum external fuel load and 279 miles with only internal fuel and six Snakeye bombs.
Originally intended as an air-superiority fighter, the F-100 was used operationally as a fighter-bomber and saw extensive service in this [304] role with the USAF in the Vietnam war. As a fighter-bomber, armament consisted of four 20-mm cannons mounted in the bottom of the fuselage below the cockpit with provision made for up to 6000 pounds of external ordnance such as bombs and rocket pods.
Before production was terminated, a total of 2194 F-100 aircraft were manufactured. Although no longer a part of the USAF inventory, the type was still in service in 1980 with four foreign air forces (ref. 177).
Since the end of World War II, the primary mission of interceptortype aircraft has been to prevent attacking enemy aircraft from reaching targets on United States territory. Several subsonic jet-powered interceptors, including the F-86D Sabre, filled the air-defense role until the supersonic Convair F-102A Delta Dagger entered the inventory in 1956. As described in chapter 10, the F-102, which first flew in 1953, was able to fly in the supersonic speed range only after being redesigned according to the precepts of the transonic area rule. Even with this modification, however, the F-102A was underpowered and could achieve a maximum Mach number of only about 1.2 at 35 000 feet.
First flight of a vastly improved Convair interceptor with the same general configuration layout as the F-102A took place on December 26, 1956. Known as the F-106 Delta Dart, this aircraft is pictured in figures 11. 13 and 11. 14 and is described by the physical and performance data given in table V.
Instant recognition features of the F-106 are the distinctive low-mounted delta wing, fuselage-mounted inlets just forward of the wing,....

aerial view of F-106
Figure 11.13 - In-flight view of Convair F- I 06A Delta Dart interceptor. [mfr via David A. Anderton]


ground photo of a F-106A
[305Figure 11.14 - Convair F-106A Delta Dart interceptor. [USAF via Martin Copp]

....and absence of a horizontal tail. The F-102A can be distinguished from the F-106 by its pointed vertical tail and by inlets located farther forward and lower down on the fuselage than on the F-106. (See fig. 10.19.) As with the F-102A, the F-106 was carefully area ruled to reduce the drag rise accompanying an increase in Mach number from subsonic to supersonic values. This careful attention to drag reduction, together with the large 24 000-pound-thrust (with afterburning) Pratt & Whitney J75 turbojet engine, gave the Delta Dart a maximum speed of 1525 miles per hour (M=2.31) at 40000 feet and the capability of climbing to its combat ceiling of 51 800 feet in 6.9 minutes; service ceiling was 52 700 feet. Together with excellent handling qualities, the high maximum speed and good climb characteristics of the F-106 have made it an outstanding interceptor that first began to replace the F-102 in 1960. As a result, the F-106 is still in use today with many interceptor squadrons (ref. 177).
Roll and pitch control of the F-106 is provided by elevons, which are flaplike movable surfaces on the trailing edge of the wing. Working in phase in response to fore and aft motions of the control stick, these surfaces provide longitudinal control moments about the pitch axis; differential deflection of the surfaces in response to lateral movement of the stick gives roll control. The lack of a horizontal tail for pitch trim prevents the use of high-lift flaps on the wing. The landing speed of the 34 510-pound-gross-weight airplane is maintained at an acceptable value (173 mph according to ref. 200) by the large wing area of nearly 700 square feet, which gives a relatively low wing loading of 49.5 [306] pounds per square foot. (Compare this wing loading with that of some of the other supersonic fighters.)
Primary armament of the F-106 consists of a Genie missile with nuclear warhead and four Falcon, radar-homing, infrared, heat-seeking missiles. Immediately after takeoff on an interception mission, control of the aircraft passes from the pilot to a ground controller who, by radio signals to the autopilot, directs the aircraft to the vicinity of the enemy intruder as displayed on a radar scope. Once within range of the enemy aircraft, the radar on board the Delta Dart locks onto the intruder, guides the interceptor to a favorable attack position, and initiates firing of the missiles. Then ground control again takes over and flies the aircraft back to its base where the pilot performs the landing. Throughout this automatic mission, the pilot can at any time assume manual control of the aircraft.
A total of 875 F-102A's had been completed, by April 1958, as well as 111 TF-102 two-place trainer versions of the aircraft. The last Delta Daggers were retired from the active Air Force inventory in 1973. Only 340 of the much more capable F-106's were built, the last of which came off the production line in 1961. The relatively few F-106's manufactured, as compared with the number of F-102A's, reflects the changing nature of the threat from enemy bombers to ballistic missiles that took place in the 1960's. Although still in use after more than 20 years, the F-106 is now being gradually replaced in the air-defense role by an interceptor version of the McDonnell Douglas F-15 Eagle. In contrast with most fighter aircraft adapted to a variety of missions, the F-102A and the F-106 were never employed for any role other than interception.
Based on lessons learned in the Korean war, the Lockheed F-104 Starfighter was originally intended as a lightweight interceptor with very high maximum speed and rate of climb. However, the aircraft saw only limited service in that role with the USAF, perhaps because it was too small to accommodate the sophisticated all-weather navigation and fire-control systems required by the Air Defense Command. A redesigned fighter-bomber version of the F-104 saw limited service with the USAF Tactical Air Command, including action in the Vietnam war, but enjoyed spectacular success in export sales to foreign governments. The aircraft has been in the inventory of 15 different countries and manufactured in 7 countries including the United States.
The North American F-100 and Convair F-102/106 just described are examples of supersonic aircraft configurations having sweptback [307] and delta wings. Most supersonic aircraft have wings of one or the other of these shapes, or some hybrid form derived from a blending of the two types. In contrast, the Lockheed F-104 was designed in accordance with an entirely different configuration concept, which featured an almost vanishingly small straight wing and a horizontal tail mounted in the T-position at the top of the vertical tail. Different views of the F-104 are shown in figures 11.15 and 11.16, and physical and performance characteristics of the F-104G version of the aircraft are Oven in table V.
With an area of 196.1 square feet, the wing of the F-104 was about one-half as large as that of the F-100 and less than one-third as large as that of the.F-106. From the side of the fuselage to the wingtip measured only 7 feet, 7 inches. The actual thickness of the wing varied from a maximum of 4.2 inches at the root to 1.96 inches at the tip. The corresponding airfoil thickness ratio was 3.4 percent. Sharp leading-edge airfoil sections (sharp enough to pose a safety hazard to ground personnel) were used to minimize the drag rise in passing through Mach 1.0. Even so, experimental data show that the transonic drag rise on this straight-wing aircraft with no area ruling was about 40 percent higher than that of the F-106 (in terms of drag coefficient). Both leading- and trailing-edge flaps were used to increase the lifting capability of the wing. Effectiveness of the simple trailing-edge flaps was augmented by boundary-layer control employing high-pressure bleed air from the engine. Ailerons were used for lateral control. Clearly shown....

ground photo of a F-104G
Figure 11.15 - Lockheed F-104G Starfighter single-engine jet fighter. [Denis Hughes via AAHS]


ground photo of pilot standing in cockpit of a F-104
[308Figure 11.16 - Front view of Lockheed F-104 Starfighter. [Clyde Gerdes via AAHS] figure 11.16 is the pronounced wing anhedral angle (droop) that served to partially offset the rolling moment due to sideslip induced by the tall surfaces. During the flight test program, the aircraft was found to have a severe pitch-up problem at the stall. Immersion of the highmounted horizontal tail in the wake from the stalled wing and long fuselage nose undoubtedly caused the problem. A stick shaker/pusher (see chapter 10) to limit the maximum attainable angle of attack eliminated the pitch-up problem.
The side-mounted inlets incorporated a fixed conical centerbody whose vertex angle and position were chosen so as to place the oblique shock from the nose of the centerbody on or just above the lip of the inlet at the maximum design Mach number. The conical centerbody inlet along with appropriate auxiliary inlet doors provided the proper engine airflow through the design Mach number range. Of lower performance than the production aircraft, the prototype XF-104 had normal shock inlets without the centerbody. [309] Photographs of this version of the aircraft are frequently seen in various references.
Armament carried on the F-104 consisted of one six-barrel 20-mm Vulcan rotary cannon. This weapon can be likened to the 19th-century Gatling gun but was, of course, power operated instead of hand cranked. Four thousand pounds of various types of external stores could also be carried. On a typical ground-attack mission, the aircraft was capable of delivering 2510 pounds of bombs at a combat radius of 620 miles. Both pylon and tip-mounted fuel tanks were dropped during the course of the mission, which was carried out at an average speed of 585 miles per hour. Cruise altitude varied from about 22 000 feet at the beginning of the mission to 34 000 feet at the return to home base. Weapons delivery took place at near sea-level altitude.
The data in table V show the F-104G to be significantly lighter than the other Century Series fighters and, with its small wing, to have the highest wing loading of the group. Maximum speed is Mach 2.0 at 35 000 feet and Mach 1.13 at sea level. Initial rate of climb at sea level is a spectacular 48 000 feet per minute. In May 1958, a world speed record of 1404 miles per hour was set by an F-104, and a record zoom-climb to an altitude of 91243 feet was made.
Before ending this discussion of the Lockheed Starfighter, some mention of its flying characteristics must be made. In many quarters, the F-104 has the unenviable reputation of being a difficult and dangerous aircraft to fly, an aircraft with unforgiving handling characteristics. Certainly, it has had an appallingly poor safety record in use with some air forces but a relatively good one in others. In fairness, the record seems to suggest that the aircraft can be flown with reasonable safety if the pilots are properly trained and the aircraft is maintained and flown strictly in accordance with the manufacturer's recommendations. Apparently, however, the aircraft can be terribly unforgiving of any departure from these recommended procedures. An interesting discussion of the F-104 and its safety record is contained in reference 186.
First flight of the F-104 prototype took place on February 7, 1954, and production aircraft first entered service with the USAF in January 1958. By the time the last Starfighter was built in Italy in 1978, a total of 2536 units had been constructed in this multinational program. A final question and observation on the somewhat controversial F-104: Why did the aircraft receive such wide acceptance by foreign air forces while, at the same time, it was essentially rejected by the USAF? Relatively light in weight, the aircraft offered a very high performance at a [310] reasonable price. These were no doubt important ingredients in the formula that assured its widespread safe abroad, as was the highly aggressive and effective sales campaign mounted by the Lockheed organization. Limited payload and range, however, restricted the usefulness of' the F-104 in service with the USAF - an organization that could and did pay for exactly what it wanted.
Designed from the outset as a fighter-bomber for long-range interdiction missions, the Republic F-105 Thunderchief was a large, heavy aircraft with Mach 2 performance. A unique feature for a fighter was the internal bomb bay intended to house a nuclear weapon. First flight of' the Thunderchief took place on October 22, 1955. After winning a flyoff competition with the North American F-107 in 1956, the F-105 first entered squadron service in 1958. (As an interesting sidelight, the F-107 was the last of the Century Series of fighters to fly and the last fighter aircraft to bear the name "North American.") Two views of the F-105B are shown in figures 11.17 and 11.18, and physical and performance data for the F-105D, the most numerous variant of the aircraft, are given in table V. The configuration incorporated a shoulder-mounted 45 sweptback wing with airfoil thickness ratios varying from 5.5 percent at the root to 3.7 percent at the tip. Trailing-edge Fowler....

aerial view of a F-105
Figure 11.17 - Republic F-105B Thunderchief single-engine jet fighter. [mfr via Martin Copp]


ground view of the F-105B underside
[311Figure 11.18 -Front view of Republic F-105B Thunderchief single-engine jet fighter. [mfr via Martin Copp]

....flaps together with leading-edge flaps were used to increase the maximum lift coefficient of the wing. Roll control was achieved by shortspan outboard ailerons assisted by upper-surface spoilers. The all-moving horizontal tail was mounted in the low position to aid in preventing pitch-up. Careful fuselage area ruling reduced the magnitude of the drag rise as the Mach number increased from subsonic to supersonic values. A most unusual feature of the aircraft are the two-dimensional variable-area supersonic inlets mounted in the wing-root position. The speed brake was an unusual petal-type arrangement that surrounded the jet nozzle.
Already mentioned is the internal bomb bay designed to accommodate a nuclear weapon. Not long after the F-105 became operational, however, the concept of carrying a nuclear weapon in the aircraft was [312] discarded, and the bomb bay was used to house additional fuel. A six-barrel Vulcan 20-mm rotary cannon was carried in the aircraft, and there were provisions for 12 000 pounds of external armament including bombs, rockets, and missiles. Such a large load could be carried only on short-range missions, however, with a more normal load being 6000 pounds. Combat radius for this load varied from 600 to 800 miles depending on the amount of external fuel carried. The F-105 was provided with all the necessary electronic equipment for full all-weather capability.
Maximum Mach number of the F-105D was 2.08, or 1372 miles per hour, at an altitude of 36 090 feet; at sea level, the maximum Mach number was 1.1, or 836 miles per hour. Normal cruising speed was 584 miles per hour. Sea-level rate of climb was a spectacular 38 500 feet per minute; only 1.7 minutes were required to reach an altitude of 35 000 feet. Ferry range with no war load was 2207 miles. With a maximum gross weight of 52 838 pounds, the F-105D is by far the heaviest fighter so far considered, nearly as heavy as the 55 000-pound, four-engine B- 17 bomber of World War II.
A total of 833 F-105 aircraft were manufactured before production ended in 1964. Extensively used in ground-attack operations in Vietnam, the Thunderchief continued to serve with the USAF for a number of years following the end of the conflict. Last of the F-105's was withdrawn from the Tactical Air Command in 1980, but a few are still in service with the Air National Guard.
The Navy Goes Supersonic
A number of Navy fighters developed during the 1950's were capable of flight at high-subsonic speeds, but only two production types could pass through Mach 1.0: the Grumman FIIF Tiger and the Vought F8U Crusader. Capable of a maximum Mach number of about 1.1, the Tiger was just barely able to enter the supersonic flight regime. With a maximum Mach number of 1.75 at 35 000 feet and a Mach 1.0 capability at sea level, however, the Crusader had much the higher performance of the two aircraft and is discussed in the next few paragraphs.
Before discussing the F8U, however, a few words on the change in the method of military aircraft designation that took place in 1962 is in order. Up until this time, the Navy designation system indicated the purpose of the aircraft, the manufacturer, and details of the aircraft geneology. For example, the designation F8U-1 is explained as follows:
indicates a fighter-type aircraft
is the identifying letter assigned to the manufacturer, in this case Vought
indicates the 8th fighter-type aircraft developed by Vought
indicates the first model of the aircraft
The Navy system was useful for those who understood it and knew the letter of the alphabet assigned to the various manufacturers. For the uninitiated, however, the system was clumsy and obscure. Further, when the same basic aircraft was used by both the USAF and the Navy, two distinctly different designations were used. For example, the USAF North American F-86 Sabre became the Navy F4J Fury. Following the introduction in 1962 of a simplified designation system for both USAF and Navy aircraft, the F8U Crusader became simply the F-8A where the number "8" indicates the fighter type and the letter "A" signifies the first model. The designation F-1A was assigned to the oldest Navy fighter then in service; Air Force aircraft then in service retained their original designations. (See refs. 171 and 200 for further discussion of designation systems.)
Three-quarter front and rear views of the Vought F-8A Crusader are shown in figures 11.19 and 11.20, respectively, and physical and performance characteristics are given in table V for the F-8H version of the aircraft. Configuration features of the F-8 include a variable-incidence,....

ground view of a F-8A
Figure 11.19 - Vought F-8A Crusader single-engine jet fighter. [NASA]


tail view of a F-8A
[314Figure 11.20 - Rear view of Vought F-8A single-engine Jet fighter. [NASA]

....35° swept wing mounted at the top of the fuselage, an all-moving horizontal tail mounted below the extended chord plane of the wing, and a chin inlet to feed air to the single 16600-pound-thrust Pratt & Whitney turbojet engine. Although not evident in the figures, the fuselage was carefully shaped in accordance with the transonic area rule.
The two-position variable incidence wing of the F-8 is a unique feature dictated by aircraft-carrier landing requirements. With the low-aspect-ratio swept wing of the F-8A, a high angle of attack was needed to reach the desired lift coefficient in the carrier approach and landing maneuver. To avoid tail scrape and possible damage at touchdown, the landing-gear configuration of the aircraft severely limited the maximum usable aircraft pitch angle. For this reason, and to provide the pilot with improved visibility during the approach, the required angle of attack was achieved by shifting the wing from the low to the high incidence position while, at the same time, maintaining the aircraft pitch angle within the desired range. Seven degrees was the amount by which the incidence changed as the wing was shifted from the low to the high position. In figures 11.19 and 11.20 the wing is in the high incidence position.
[315] Other features of the approximately 6-percent-thick wing included a chord extension, sometimes called a snag or dogtooth, beginning at about the midsemispan position and extending to the wingtip. A vortex generated at the beginning of the snag helps alleviate pitch-up in much the same manner as a wing fence (discussed in chapter 10). High-lift devices consisted of inboard and outboard leading-edge flaps and plain trailing-edge flaps. To further increase the maximum lift coefficient, the capability of the trailing-edge flap was augmented by blowing boundary-layer control using bleed air from the engine. Small inboard ailerons were used for lateral control; these surfaces could also be deflected symmetrically to increase lift at low speeds.
The fixed-geometry inlet seems, at first glance, to be somewhat incongruous on an aircraft of such high performance as that of the Crusader. The nose of the aircraft protrudes forward of the chin inlet, however, and probably serves much the same purpose as the fixed conical bodies employed on the inlets of the Lockheed F-104. As compared with a nose-mounted normal-shock inlet, the chin inlet would accordingly be expected to have better pressure recovery at the supersonic speeds achieved by the F-8.
The Crusader was the first carrier-based aircraft to reach a speed of 1000 miles per hour. Not quite as high in maximum speed or rate of climb as the later-model Century Series fighters, the F-8H is nevertheless shown by the data in table V to be a high-performance supersonic aircraft. As a fighter, it was usually equipped with four 20-mm cannons and two or four Sidewinder missiles. Initially, a clear-weather air-superiority fighter, the Crusader was later modified to have limited allweather capability.
First flight of the F-8 took place on March 25, 1955; and before production ended, 1261 Crusaders had been constructed. In addition to the U.S. Navy, the French Navy and the Philippine Armed Forces used various versions of the F-8. In the Vietnam conflict, the Crusader saw extensive service in photoreconnaissance, ground-attack, and fighter-escort roles. U.S. Navy fighter service for the Crusader ended in March 1976, but a few are still on duty as photoreconnaissance aircraft. According to reference 177, some F-8's are still in use with French and Philippine forces.