v1.2.1 / 01 dec 01 / greg goebel / public domain
* The rapid evolution of aircraft design in the 1950s led to new aircraft types with sleek lines and impressive performance. One such aircraft was the North American A-5/RA-5 "Vigilante".
The Vigilante was designed as a carrier-based strategic nuclear bomber, but would see action over Vietnam as a fast reconnaissance aircraft. This document outlines the history of the Vigilante.
* In the postwar period, the US Navy became determined to acquire a nuclear strike capability, first acquiring the North American AJ "Savage" and Douglas A-3 "Skywarrior" bombers. These were both subsonic aircraft, and with the rapid advance of aircraft design, both quickly became obsolete for the missions for which they had been designed.
North American Aviation (NAA) felt they could provide something more capable for the nuclear strike mission, and in November 1953 the company's Columbus, Ohio, division began a program on their own initiative using company funding to build such an advanced carrier-based nuclear-strike bomber. The development team was led by Frank G. Compton.
The new aircraft was originally referred to as the "North American General Purpose Attack Weapon (NAGPAW)" and later given the company designation of "NA-233". After discussions with the Navy, the NAA-233 concept took shape as a twin-engine aircraft with advanced combat avionics, Mach 2 performance, and an interesting "linear bomb bay" in which a nuclear weapon was popped out the tail to give the aircraft a better chance of escaping the atomic blast.
North American engineers also considered fitting the aircraft with a rocket engine powered by jet fuel and hydrogen peroxide for an additional burst of speed over the target area, but the Navy didn't like the idea of handling a nasty, reactive, and unstable substance like hydrogen peroxide on board a ship, and it didn't happen.
* The Navy gave North American the go-ahead for two prototypes in mid-1956. The first prototype of the "YA3J-1 Vigilante", as it was formally designated, was rolled out on 16 May 1958. First flight was on 31 August 1958, with North American chief test pilot Dick Wenzel at the controls.
The Vigilante was long and sleek, with a relatively small high-mounted swept-back wing, and all-moving slab horizontal and vertical tailplanes. The aircraft had tricycle landing gear, with the main gear retracting into the fuselage. All three gear had single wheels and retracted forward, with the main gear rotating 90 degrees to fit into the wheel wells.
The Vigilante was powered by twin General Electric YJ79-GE-2 engines, with engine bays made mostly of titanium, and covered with gold film to reflect heat. The aircraft had a large fuel capacity to give it long range and permit extended flight in afterburner.
The aircraft achieved good low-speed landing performance through the use of large flaps. The ailerons were eliminated to make room for the flaps, with roll control provided by differential movement of the horizontal tailplanes and an innovative scheme of spoilers on the wing leading edge and small "deflector" flaps near the trailing edge. A "boundary layer control (BLC)" scheme was incorporated, in which air bled from the engines was automatically blown over the flaps when they were extended, in order to lower landing speed.
The wingtips folded up to allow carrier hangar storage. North American had considered twin vertical tailplanes to meet the height restrictions of a carrier hangar deck, but although such a configuration is common now, it was too bold for the Navy at the time. North American went with a single tall vertical tailplane that folded to one side.
The Vigilante featured a long list of new technologies, including wing skins made of aluminum-lithium alloy; critical structures made of titanium; variable engine inlets; a windshield of stretched acrylics; and a retractable mid-air refueling probe. The two crewmen flew in tandem cockpits with individual "clamshell" canopies, sitting in North American HS-1 rocket-boosted ejection seats. The pilot could control ejection for both crewmen, though the back-seater could also eject on his own if necessary.
While the pilot had a good forward view, the "bombardier-navigator" in the back seat had only a small window to each side. Originally, North American engineers hadn't intended to provide any windows for the back-seater on the premises that he would be able to see his displays better in the dark and would be protected from nuclear flash, but feedback on the idea from prospective bombardier-navigators was very negative. The engineers added the two little windows as a compromise.
The Vigilante had the advanced North American Autonetics "AN/ASB-12 Bomb Directing Set", which included:
The Vigilante was also one of the first aircraft to have a "fly by wire" flight control system.
* The second prototype flew in November 1958. The flight test program went well, though the second prototype was lost on 3 June 1959 when its hydraulic and electrical systems failed.
The first production "A3J-1" Vigilante flew in 1960. Production aircraft were progressively fitted with more powerful J-79 engine variants, leading to J-79-GE-8 engines, with 4,945 kilograms (10,900 pounds) dry thrust and 7,710 kilograms (17,000 pounds) afterburning thrust. These were the same engines used on many of the Navy's McDonnell Douglas F4H-1 (F-4B) Phantom fighter, simplifying logistics and maintenance.
Carrier trials began in July 1960. To promote the Vigilante with the US Congress, the Navy also established several speed and altitude records with the aircraft. On 13 December 1960, Navy test pilots Commander Leroy Heath and Lieutenant Larry Monroe took their Vigilante to Mach 2.1 and then nosed it up into a climb that brought it to a record 27,750 meters (91,000 feet).
At that altitude, the aircraft was no longer aerodynamic and tumbled onto its back as it fell down the far side of the arc, the engines flamed out in the thin atmosphere. However, such problems had been encountered in practice flights leading up to the attempt. Heath simply neutralized the controls; once the Vigilante reached thicker air halfway through its fall, it naturally adopted a nose-down attitude, and Heath was able to relight the engines.
* Deliveries of the A3J-1 to operational units began in 1961, with last deliveries of the type in 1963. By that time it had been redesignated the "A-5A", due to a Defense Department decision to come up with a common designation scheme for all US military aircraft, implemented in September 1962.
Carrier air group commanders were not entirely pleased with the Vigilante. Although the aircraft had excellent performance and the airframe proved reliable, it was full of "bleeding edge" electronic technologies and was a maintenance headache. During the testing phase, the VERDAN computer had a "mean time between failure (MTBF)" of 15 minutes! However, within a few years the computer's MTBF was up to a reasonable 240 hours.
The Vigilante was also something of a handful to land on a carrier, being not only big but very sleek and "hot". On a hard landing, the aircraft would "bounce", with the nosewheel tire popping and tearing apart on the second strike to shed pieces of rubber into the engines.
In addition, the nosewheel strut proved weak and had to be eventually reinforced. Some Vigilante pilots claimed that the aircraft's reputation for being difficult to land was exaggerated, but did admit that it was unforgiving. The aircraft acquired a reputation as something of a beast that required particular skill to fly, and of course Vigilante pilots were not quick to disagree. Egos were involved, which could be big and antagonistic in the male-oriented, hyper-competitive Navy Air culture.
Fighter pilots of course tended to look down on the big bomber, comparing it to an elephant, though apparently at least as much for the wild sounds made by the Vigilante's twin J79s when they were throttled up or down during landing approach. Leroy Heath, back in normal fleet service, picked up the comparison and ran with it, naming his Vigilante the PASSIONATE PACHYDERM. He also bought a wind-up toy elephant, painted the PACHYDERM's aircraft number "701" on its side, and took to setting it on strolls across the closed-circuit TV camera that gave the pilot ready rooms a view of carrier-deck landings.
One A-5A pilot, Lieutenant Commander Ken Enney, decided to fight back more aggressively by "bouncing" a Vought Crusader fighter. The fighter pilot eventually called out over radio: "I can't get rid of this guy!" This set off quite a buzz among the flight crews, though Enney himself later admitted that his Vigilante was lightly loaded and that he could only have gotten away with such a stunt at altitudes above 6,000 meters (20,000 feet).
* By this time the last A-5As were delivered to the fleet, there was no interest in using the Vigilante for nuclear strike, or even conventional attack. Partly the issue was political, partly it was technical.
The political issue was that the Navy's Polaris submarines were coming on line, and the Navy decided to focus on Polaris as their strategic nuclear strike weapon. The Vigilante development program cost about $200 million USD in contemporary dollars, with the pricetag of each aircraft rising to about $10 million USD, and the Navy felt that their other existing strike aircraft, such as the new Grumman Intruder, were more cost-effective for conventional strike missions.
The technical issue was that the Vigilante wasn't looking very promising in the nuclear strike role anyway. The linear bomb bay scheme sounded nice on paper, but it was a nightmare in practice. The bomb bay tube ran up the fuselage between the engines, and since it was much longer the nuclear store, expendable fuel tanks were tacked on in the rear of the store.
During a strike, the entire assembly was popped out the tail with an explosive cartridge driving it down launch rails. Not only did the scheme prove unreliable, the store also tended to "draft" behind the aircraft, preventing the pilot from laying it down accurately. The linear bomb bay would never actually be used in practice.
The Vigilante, in short, had become an expensive aircraft without a clear mission. However, rather than simply getting dropping it, the US Navy decided that the Vigilante should be used in a different mission, the fast reconnaissance role.
* The decision to develop the Vigilante strictly as a reconnaissance aircraft was taken at a time when efforts were already being made to enhance its attack abilities, as well as adapt it to the reconnaissance mission. An improved attack variant, the "A3J-2" (later "A-5B"), and a reconnaissance version, the "RA-5C", were both built.
Work began on the A-5B in 1961, with the first example flying at the end of April 1962. The most visible change from the A-5A was a modified "humpback" fuselage that offered a substantial increase in fuel capacity. Longer and wider flaps were fitted, as well as a new BLC scheme, in which high-pressure engine bleed was fed to the front of the wing rather than the back.
Four stores pylons were fitted, two under each wing, each with a load capability of up to 950 kilograms (2,000 pounds). The engine inlet ducts were also modified, and the brakes were improved to handle the increase in aircraft weight.
18 A-5Bs were ordered, but by the time the first of them was flying the Navy had given up on the Vigilante as a bomber. Only six A-5Bs were completed. They were used in an interim training role for the reconnaissance version, the RA-5C, and never reached fleet service. The remaining twelve in the batch were completed as RA-5Cs.
* The RA-5C was developed in parallel with the A-5B, and first flew on 30 June 1962. The RA-5C incorporated all the new features of the A-5B, such as the humpback fuselage, the big flaps, and the leading-edge BLC system. The new BLC scheme proved a little tricky, as it required more engine power. As the RA-5C was substantially heavier than the A-5A, this meant that once the BLC system was engaged the aircraft lost power and tended to drop abruptly.
The tunnel-store system was retained, and in fact it appears that the RA-5C was still capable of carrying the old primary store train and could also be fitted with the four stores pylons. In practice, however, the RA-5C was never armed.
The major difference from the A-5B was the RA-5C's equipment fit, which featured a suite of reconnaissance gear that was state-of-the-art for the time. The TV camera under the nose became part of the reconnaissance suite, but most of the gear was carried in a long slender "canoe" on the bottom of the aircraft's fuselage and running from the nose gear back towards the tail.
The reconnaissance suite consisted of the following sensor systems, listed from front to rear:
An electronic strobe flash pod, powered by a spinner on its tail, could be carried under one wing to provide illumination for night reconnaissance. The sensor systems on the RA-5C worked in conjunction to bring back a flood of information from a reconnaissance mission, stored on magnetic tape and photographic film.
The RA-5C's reconnaissance systems were under control of the back-seater, who was designated the "reconnaissance-attack navigator (RAN)". The AN/ASB-12 system was retained, to be used for navigation and camera targeting.
An RA-5C's mission was conducted by an aircraft carrier's "Integrated
Operational Intelligence Center (IOIC)". Electronic intelligence experts
studied the information stored on magnetic tape, while the film was passed
through a one-hour film processing system, which at the time was a
classified system though it is available everywhere today. The processed
film was then inspected by photographic intelligence specialists.
NORTH AMERICAN RA-5C VIGILANTE:
_____________________ _________________ _______________________
spec metric english
_____________________ _________________ _______________________
wingspan 16.2 meters 53 feet 2 inches
length 23.3 meters 76 feet 7 inches
height 5.9 meters 19 feet 5 inches
empty weight 17,000 kilograms 37,500 pounds
max loaded weight 36,100 kilograms 79,600 pounds
maximum speed 2,125 KPH 1,320 MPH / 1,150 KT
service ceiling 15,900 meters 52,100 feet
range 3,300 kilometers 2,050 MI / 1,785 NMI
_____________________ _________________ _______________________
The RA-5C proved so useful in Vietnam that the Navy ordered 46 more RA-5Cs in 1968. Only 36 were actually completed, however, with the last rolling off the production line in August 1970. This final batch featured J-79-GE-10 engines with 8,100 kilograms (17,860 pounds) afterburning thrust, as well as a leading-edge wing extension trailing back from the air intakes, plus slightly modified air intakes. By this time, the RA-5C had plenty of power and it was no longer such a handful on carrier deck landings.
* After the RA-5C's introduction to fleet service in 1964, the aircraft was almost immediately sent into combat over Southeast Asia, with the first reconnaissance missions flown in August 1964. Initially, the Navy was so concerned about the secrets of the Vigilante falling into enemy hands that operations of the aircraft were restricted to South Vietnam, but an asset is no good if it can't be used, and the Vigilante was soon sent north.
RA-5Cs were used to observe enemy troop concentrations and movements; obtain pre-strike information on a target and post-strike evaluations on the same target; and, in one large-scale endeavor early in the war, obtain imagery for the construction of detailed maps of all of South and North Vietnam.
The RA-5C was generally the last aircraft launched from a carrier during an operations cycle, since it was one of the fastest aircraft the Navy had. The Vigilante was heavier than the F-4 Phantom but used the same engines, so the RA-5C had a poorer thrust-to-weight ratio than the F-4, making it underpowered on paper. However, the Vigilante always flew "clean", unencumbered by external stores, which was never the case for a combat-configured F-4.
The Navy assigned F-4s to protect the valuable RA-5Cs from North Vietnamese MiGs, as well as provide additional "eyes", since a Vigilante pilot's rear view was nonexistent. F-4 pilots often had to call to the Vigilante pilots to slow down so the fighter could keep up.
Once over enemy territory, the Vigilante flew continuously in full afterburner, keeping above Mach 1 at all times. It would fly into the target area at 2,100 to 2,400 meters (7,000 to 8,000 feet), and could in many cases use its oblique cameras and other reconnaissance gear to obtain information without flying directly over the target. The aircraft was fast and agile, and was able to dodge surface-to-air missiles on many occasions.
The electronic strobe system devised for the Vigilante was not used in combat, as it made the aircraft too good of a target. During night missions, infrared and SLAR were used instead. However, while the optical cameras in the sensor suite worked reliably, keeping the electronic sensor systems working proved difficult under operational conditions. One Vigilante squadron circulated a fake advertisement for the "RA-5C Vigilantoy", saying: "You can't afford to buy less than a dozen -- that way you can have one to fly while the others are being repaired."
The old tunnel store system, now reduced to accommodating fuel tanks, was also sometimes a source of trouble. On a few occasions, the fuel tanks came loose during catapult shots, smashing through the tail cone to fall back on the deck, causing a fire. In most cases, the fire was quickly extinguished and the Vigilante was not much the worse for wear, but at least one went out of control and was lost in such an incident, the two flight crew punching out successfully.
* 18 RA-5Cs were lost in combat during the war, giving it the highest loss rate of any Navy aircraft in the conflict. 13 Vigilantes were shot down by flak, two were shot down by surface-to-air missiles (SAMs), one was shot down by a MiG-21, and the other two were lost to unknown causes over enemy territory.
The loss rate was high because the missions were unusually hazardous. Vigilantes were used for both pre-strike and post-strike reconnaissance. Pre-strike missions were relatively safe, but the North Vietnamese quickly realized after a target was bombed a reconnaissance aircraft would soon arrive to evaluate the damage, and so post-strike missions were generally conducted in the face of an enemy that was thoroughly alert and waiting. Vigilantes flying post-strike reconnaissance missions tried to follow the strike elements in just after the last bombs fell to reduce the risk.
Only 9 of the 36 of the aircrew shot down were rescued, with others either killed or taken prisoner. In one case, the rescue was a grim adventure like something out of a movie. Lieutenant JG Francis Prendergast was the back-seat RAN on an RA-5C that was shot down over North Vietnam on 9 March 1967. He was captured near the seashore by North Vietnamese militiamen, with two of them assigned to guard him. One was armed with a rifle, the other with Prendergast's own 0.38-caliber revolver, standard equipment for aircrew and carried externally in a shoulder holster.
Prendergast carried the revolver with the first two chambers unloaded as a safety measure, and as a backup also had a small 0.22 caliber automatic pistol hidden inside his flight suit. When a rescue helicopter and support aircraft showed up, strafing drove off all the North Vietnamese except the guards, who felt safer staying with Prendergast than running for cover.
This proved a fatal mistake. While the two North Vietnamese were distracted by the noise and confusion, Prendergast pulled out the little automatic, cocked it, and shot the militiaman with the rifle in the head. The other militiaman tried to shoot Prendergast with the revolver, only to find that the hammer fell on an empty cylinder, and was shot himself an instant later. Prendergast swam out to the rescue helicopter and was retrieved.
* As the war wound down in the mid-1970s, so did Vigilante reconnaissance squadrons. With the aircraft out of production, obtaining spares became increasingly difficult, and so did keeping a complicated machine like the RA-5C flying. The Navy also increasingly regarded a dedicated reconnaissance aircraft as something of a luxury, preferring to fit fighter-attack aircraft with reconnaissance pods, trading capability for operational flexibility.
Vigilante squadrons began to be disbanded in 1974, and by 1979, the Vigilante was out of service. Most were sent to the "boneyard" at Davis-Monthan Air Force Base in Arizona. A number were used as nonflying targets, including one that was used a target for the Tomahawk cruise missile whose destruction is documented in a well-known video.
A total of 156 Vigilantes were built, including prototypes. Nine are known to survive as gate guards and static museum exhibits, including one the Naval Aviation Museum in Pensacola, Florida; another at the INTREPID Air-Sea-Space Museum in New York City; a third at the Pima Air Museum in Arizona; and two more at the Naval Air Test & Evaluation Center Museum at Patuxent River, Maryland.
* While the sleek Vigilante is largely forgotten, it was and remains an impressive aircraft, with many similarities to the controversial British BAC TSR-2 strike aircraft, designed and cancelled a few years after the introduction of the Vigilante.
The story of the Vigilante includes some minor details not mentioned in the preceding text:
* It's always slightly troublesome when writing up a Navy aircraft to have to convert the designation from the old-style ("A-3J1") designation to the new-style ("A-5A") designation. This particular decision came down from Defense Secretary Robert McNamara and his aides, the "Whiz Kids", and is still somewhat controversial.
McNamara and his Whiz Kids were, and remain, thoroughly despised by the military establishment for their attempts to apply corporate and academic bureaucratic methods to military affairs. They tended to be condescending to the military brass, and they've never been forgiven or forgotten.
The designation change is rumored to have come down because McNamara embarrassed himself in a high-level briefing by confusing Navy and Air Force aircraft types. Personally, I tend to be sympathetic to the change, since except for having to translate version numbers, I find it much less confusing. Navy hacks are quick to point out that the old Navy designation scheme was a bit more informative. Either way, it's an indication of the bitterness felt towards McNamara that this minor issue is still a source of complaint.
* Being a bookish sort and absolutely an aviation hobbyist, I make no pretensions of being very much like a combat-jet jock. However, I have to admit that after reading about Leroy Heath's pranks with his toy "pachyderm" I had to think: "Now this is my sorta guy!"
* Sources include:
* Revision history:
v1.0 / 01 mar 99 / gvg
v1.1 / 01 may 01 / gvg / Major update.
v1.2 / 01 jun 01 / gvg / Typo corrections.
v1.2.1 / 01 dec 01 / gvg / Minor cosmetic update.