The Bell AH-1 HueyCobra

v1.0.1 / 01 sep 02 / greg goebel / public domain

* The very first operational purpose-designed helicopter gunship, the Bell AH-1 HueyCobra, was designed in the mid-1960s as an "interim solution" to support the US Army in the Vietnam War. This "interim solution" is still being manufactured and improved in the 21st century, making it a success far beyond the wildest dreams of its creators. This document provides a short history of the AH-1 Cobra.



* As the United States Army ramped up its involvement in Vietnam in the early 1960s, Bell's UH-1 "Iroquois" or "Huey" turbine-powered helicopter, first flown in 1956, became the workhorse of Army heliborne combat operations. When the "UH-1A" was deployed to Southeast Asia in 1962, it was the Army's first operational armed helicopter.

The UH-1A was followed by the bigger and more powerful "UH-1B" and the still more powerful "UH-1C", but combat experience demonstrated that the Huey left something to be desired in the helicopter gunship role. Something faster and less vulnerable was needed.

The Bell company had been interested in the concept of a dedicated helicopter gunship since 1958, and unveiled a mockup of such a rotorcraft in June 1962. The "D225 Iroquois Warrior" was based on the engine and mechanics of the Huey, but had a new sharklike fuselage that gave it the looks of a fighter. It had a tandem two-seat cockpit with a gunner in front and a pilot in back, with the seats stepped to give the pilot good forward visibility; a turret with an automatic grenade launcher in the nose; a forward-firing 20 millimeter cannon in a belly pack; and stub wings with stores pylons to carry munitions, such as six SS-11 wire-guided missiles.

The Army liked the idea, and awarded Bell a contract in December 1962 to develop a proof-of-concept demonstrator. Bell engineers quickly modified the company's well-established Model 47 / OH-13 Sioux piston-powered helicopter to produce the "Model 207 Sioux Scout", which was completed in August 1963.

The Sioux Scout featured a streamlined fuselage, with a tandem cockpit and a chin turret with two 7.62 millimeter M60 machine guns. It only generally resembled the Iroquois Warrior mockup, and was obviously too light for actual combat use. However, it was strictly a demonstrator, and even though it was something of a "toy" gunship, it allowed the Army to explore the possibilities of such a weapon.

* The Army decided to obtain an operational gunship, issuing requirements for a powerful "Advanced Aerial Fire Support System (AAFSS)" competition in August 1964. Several companies submitted proposals, and the Army selected the Lockheed AH-56 "Cheyenne" for development.

However, the Cheyenne wasn't scheduled to be available until 1970, and so the Army also initiated a competition for an interim gunship, based on an existing helicopter type. They received proposals for a modified Chinook from Boeing-Vertol; a modified Sea King from Sikorsky; a modified Sea Sprite from Kaman; and a "modified UH-1" from Bell designated the Model 209.

Although Bell had been eliminated from the AAFSS competition early on, the company had continued to work on a dedicated helicopter gunship using company funds. Calling the Model 209 a "modified UH-1" was substantially stretching the truth, since it could not possibly be mistaken for a Huey, though it shared many common systems and parts. Bell was able to convince Army officials that the Model 209 could be available when they wanted it, and the Army accepted the fiction.

The Model 209 demonstrator strongly resembled the D225 Iroquois Warrior, featuring a sharklike fuselage, tandem seats, and stub wings. It was powered by an Avco Lycoming T53-L-11 turboshaft engine with 1,100 horsepower. Traditionally, Bell helicopters used a two-bladed rotor with a crosswise stabilizing bar, but to save weight the stabilizing bar was eliminated by an electromechanical "Stability Control Augmentation System" (SCAS). The engine and rotor system were taken directly from the UH-1C Huey, and in fact the entire tail boom was a UH-1C assembly.

The Model 209 featured an Emerson Electric chin turret with a General Electric (GE) GAU-2B/A six-barreled 7.62 millimeter "Minigun". The stubby wings were fitted with a total of four stores pylons, which could carry unguided missile packs, gun pods, or other stores. The Model 209 had retractable skid undercarriage, which appears to have been adopted as least as much to improve the turret's field of fire and ensure clean stores release as to improve aerodynamics. Forward fuselage panels were flush-riveted and antennas were fitted internally to keep the design as clean as possible.

* Bell proposed the Model 209 to the Army in August 1965, and the new helicopter made its first flight a month later, on 7 September 1965. In October, it set a world helicopter speed record for its class of 320 KPH (200 MPH). The Army conducted a flyoff competition for the interim gunship in November 1965, with the optimized Model 209 declared the winner. The Army placed a contract with Bell for two prototypes of an operational version on 7 April 1966, followed by a production contract for 110 of the gunships on 13 April.

The production version of the Model 209 was originally designated "UH-1H", in keeping with the fiction that the gunship was just a "modified UH-1". However, in July 1966, the designation was changed to "AH-1", similar enough to the UH-1 designation to keep up the fiction.

Traditionally, the Army named their aircraft after American native tribes, such as "Mohawk", "Iroquois", "Sioux", "Cheyenne", and so on, but the service was engaged at the time in an odd exercise in litigation with Piper Aircraft, who also used tribal names for their aircraft. This permitted a break with tradition.

UH-1 Hueys operating in Vietnam at the time were known as "Slicks" if they were unarmed transports; "Hawgs" if they were armed with rockets; and "Cobras" if they were armed with machine guns and rockets. It was in keeping with the fiction that the AH-1 was really just a modified Huey to name it the "HueyCobra". In practice, the AH-1 would become forever known as the "Cobra", with the original use of this name for the UH-1 generally forgotten.

* The Model 209 demonstrator was kept in service for almost six years to test different weapon and equipment fits, ultimately being brought up to something very similar to production AH-1 standard. It was returned to an approximation of its original form when it was retired, to be placed on display at the Patton Museum at Fort Knox, Kentucky. There are also some rumors that a second Model 209 demonstrator was built, but if so the details are very unclear.



* The initial production HueyCobra was given the designation "AH-1G". The first of the two prototypes, sometimes referred to as "YAH-1Gs", flew on 15 October 1966, with the second making its first flight in March 1967.

The AH-1G was very similar to the Model 209, with some minor changes. The AH-1G was fitted with an uprated T53-L-13 turboshaft engine with 1,400 horsepower, and the retractable landing skids were changed to fixed skids, since the benefits of retractable skids did not seem to outweigh potential reliability problems. Incidentally, there were attachment points on the skids to allow wheels to be clipped on for towing the HueyCobra over a runway.

The Model 209 also had a small ventral fin at the end of the tail boom for improved directional stability, but flight tests demonstrated that the HueyCobra was perfectly stable, and so the AH-1G had no ventral fin.

* The AH-1G defined the "baseline" configuration for subsequent members of the family. The highly streamlined fuselage was built with honeycomb aluminum, with plenty of access panels for easy maintenance. The AH-1G had a 936 liter (247 US gallon) self-sealing fuel tank, plus armor protection for engine, fuel systems, and hydraulic systems.

The two crew members sat in armored seats with side panels that could be pulled up in a pinch for more protection, and an armored nose plate was fitted to shield the gunner. Although the Model 209 demonstrator had been fitted with armor glass, it was judged too heavy, and no production AH-1 would ever be rolled out with armor glass.

The AH-1G was originally fitted with the Emerson Electric "TAT-102A" turret with a single GE GAU-2B/A Minigun with 8,000 rounds of ammunition. This was a temporary fit, installed until the improved "TAT-141" turret became available. The TAT-141 was fitted with either two Miniguns with 4,000 rounds each, or a single Minigun and a M-129 40 millimeter grenade launcher with 300 (some sources say 231) rounds of ammunition. Apparently the TAT-141 could in principle also be fitted with two grenade launchers, but this was rarely, if ever, done.

The Minigun could be selected for rates of fire of 2,000 or 4,000 rounds per minute (RPM), while the grenade launcher had a rate of fire of 450 RPM. The turret could be aimed 25 degrees upward, 60 degrees downward, and over 230 degrees of arc. Although the gunner normally operated the turret, the pilot could also fire it in the fixed-forward position in an emergency. The gunner also had simple flight controls to allow him to fly the machine if push came to shove.

* The AH-1G arrived at Bien Hoa Air Force Base in South VietNam in August 1967, and found itself in the thick of combat immediately. HueyCobras were used to escort transport helicopter forces and provide fire support for ground operations. They were also used in conjunction with fast Hughes OH-6A Cayuse scout helicopters in devastatingly effective "hunter killer" or "pink" teams. Cobras were also used in other roles when necessity demanded, including armed reconnaissance, target spotting, and even search and rescue. By the end of 1968, there were 337 Cobras in Vietnam.

While many gunship crews liked the speed, agility, and hard-to-hit slender lines of the Cobra, there was another faction that preferred the old Huey gunships, since the door gunners not only provided additional eyes and ears, but could lay down suppressive fire to the rear of the helicopter. The debate between the two factions went on through the war.

The Cobra's primary external warloads were 7-round or 19-round 70 millimeter (2.75 inch) rocket pods, with rockets fitted with high explosive, flechette anti-personnel dart or "nail", white phosphorus incendiary, or smoke marking warheads. Four-round 127 millimeter (5 inch) Zuni rocket pods were also qualified, but rarely used. The rocket pods were called "Hog pods" and a Cobra with a full load of four Hog pods was called a "Heavy Hog".

Early Cobras with the one-gun turret also sometimes carried one or two SUU-11/A Minigun pods with 1,500 rounds each on the stub wing pylons. The range and killing power of the Minigun was limited, however, and though the 70 millimeter rockets had much more reach and punch, they were inaccurate and had to generally be fired in salvos to blanket a target.

To provide more hitting power, beginning in 1969 many AH-1Gs were fitted with the XM-35 cannon system, which was a GE M61A1 Vulcan 20 millimeter six barrel Gatling gun carried on a pylon, with a streamlined fairing attached to the left side of the helicopter on the top of the landing skid for ammunition storage, and panels added below the cockpit to provide protection from muzzle blast. Aircrews had to hang on to canopy panels when firing to keep the panels from popping open.

* The AH-1G underwent a number of changes during its service in Vietnam. Early production AH-1Gs had landing lights built into the tip of the nose. Later production moved the landing lights into a retractable fixture in front of the turret.

The Cobra's big canopy made for a pretty good greenhouse, turning the cockpit into a "hotbox". While the AH-1G was originally delivered with ventilation blowers to keep the flightcrew comfortable, these were totally inadequate for service in Vietnam, and a much more effective air-conditioning system or "environmental control unit (ECU)" was installed in the field and in later production.

One of the more significant changes was the switch of the tail rotor from the left to the right side of the helicopter. This was done to improve directional control. Retrofits were made in the field by swapping out the entire tail boom with a replacement unit.

Very late in the war, during the North Vietnamese spring offensive of 1972, two Cobras were shot down by enemy SA-7 shoulder-launched surface to air missiles (SAMs), some Cobras were fitted with an upturned "sugar bowl" exhaust to reduce their infrared profile, with some minor detriment to performance, and were fitted with an an AN/ALQ-144 infrared countermeasures (IRCM) unit on the engine cowling just forward of the exhaust.

The AN/ALQ-44 is what is known as "hot brick" jammer. It is a little cylindrical "lighthouse" faced with a hot ceramic brick core that radiates strongly in the infrared. The core is surrounded by a rotating shutter that turns the infrared output on and off. A heatseeking SAM tries to home in on the hot jammer module, but when it is pulsed "off", the missile then assumes it has lost lock and veers off target.

* The AH-1G Cobra was basically a daylight weapon, though it could be used at night in a pinch when supported with illumination flares and searchlights.

The Army performed two experiments to develop a night-capable Cobra. The first was the "Southeast Asia Multi-Sensor Armament Subsystem for HueyCobra (SMASH)" program. SMASH featured an AH-1G fitted in the nose with an Aerojet ElectroSystems AN/AAQ-5 "Sighting System Passive Infra-red (SSPI)" sensor turret, basically what would later be called a "forward looking infrared (FLIR)" imager; and an Emerson Electric AN/APQ-137B "moving target indicator (MTI)" radar pod carried under the right wing.

Incidentally, the SMASH experiment was conducted under the umbrella of the "Expedite Non-Standard Urgent Requirement for Equipment (ENSURE)" program. The military was into "cutesy acronyms" in those days.

The second experiment was the "Cobra Night Fire Control System (CONFIGS)", which was fitted in the nose with a low-light TV (LLTV) imager. The imager resembled a length of pipe bent into a "U" shape, and gave the the Cobra a peculiar look of having a "mustache". The CONFIGS imager could rotate to track turret movements.

These sensor technologies were new and immature in the Vietnam era, and neither SMASH nor CONFIGS were successful. However, the idea of a night-capable Cobra would be back.

A total of 1,126 AH-1Gs were ultimately built, with the last delivered in February 1973. About 300 were lost in Vietnam, with about a third of them lost in non-combat-related accidents. Precise numbers of losses are difficult to tally, because in some cases the Cobras were recovered and rebuilt by enterprising ground crew teams.



* The US Marine Corps was very interested in the HueyCobra, but preferred a twin-engined version for improved safety in over-water operations, and also wanted a more potent turret-mounted weapon. Although at first the Department of Defense had balked at providing the Marines with a twin-engined version of the Cobra, in the belief that commonality with Army AH-1Gs outweighed the advantages of a different engine fit, the Marines won out, and awarded Bell a contract for 49 twin-engined AH-1J "SeaCobras" in May 1968. As an interim measure, the US Army passed on 38 AH-1Gs to the Marines in 1969.

The first AH-1J made its initial flight in November 1969. The most prominent features of the SeaCobra were its Pratt & Whitney Canada (P&WC) "T400-CP-400 Twin Pac" engine system, and its GE "M197" 20 millimeter cannon mounted in a "universal turret".

The T400-CP-400 engine system was basically two P&WC PT6 turboshafts driving a common gearbox, and in fact was also known as the "PT6T-4". Total output power of the engine system was 1,530 horsepower, a comfortable boost upward from the 1,400 horsepower of the AH-1G's Lycoming T53-L-13 engine. The Twin Pac provided enough power to keep the helicopter flying with an engine out. The Twin Pac engine system was actually capable of providing 1,800 horsepower, but the helicopter's drive train wasn't strong enough to support it and when both engines were running, they were power-limited. When one went out, the other could be run at full power.

The M197 was essentially a three-barrel version of the six-barrel "M61" Vulcan cannon, and would eventually become the standard turret weapon for both Marine and Army Cobras. The M197 had a rate of fire of 750 rounds per minute, though it could only fire 16-round bursts, and the AH-1J carried a supply of 750 rounds. The gun could be aimed 20.5 degrees upward, 50 degrees downward, and over 240 degrees of arc.

The AH-1J also had a slightly larger fuel tank, with a capacity of 1,023 liters (270 US gallons) instead of 936 liters (247 US gallons), and had a number of minor equipment fits to tailor it for USMC service.

Initial delivery of the AH-1J was in October 1969, with the type beginning service evaluation in July 1970. Four AH-1Js were sent to South Vietnam in February 1971 for a two-month combat evaluation. They participated in the South Vietnamese invasion of Laos, which lasted until April. These SeaCobras were then withdrawn, but AH-1Js were re-deployed to the theater from Okinawa during the North Vietnamese offensive of 1972.

The Marines bought a second batch of AH-1Js, bringing total procurement to 69, with the last rolled out in February 1975. The AH-1J and later twin-engine HueyCobra variants are sometimes referred to as "TwinCobras".



* The AH-1G was purchased by the US Army as an "interim type" for the "jungle fighting" role, but the Army's broader concern was the task of protecting Western Europe from the legions of Warsaw Pact armor to the east.

The Army had initiated the AAFSS program to develop the Lockheed AH-56 Cheyenne for the anti-tank gunship role, but development of the Cheyenne did not go smoothly, and as one writer put it, "the vultures began to gather", with Sikorsky and Bell trying to sell unsolicited alternatives to the Army.

The Sikorsky offering was the "S-67 Blackhawk", a sleek gunship, which despite the name was no real relation to the later S-70 Black Hawk utility-transport helicopter. The Bell offering was a refined HueyCobra, the "Model 309 KingCobra".

Bell announced the KingCobra program in January 1971. Two prototypes were actually built, one with a P&WC T400-CP-400 Twin Pac dual turboshaft engine system much like that used on the AH-1J, but with a stronger drive train allowing full 1,800 horsepower operation, and the other with a single Lycoming T55-L-7C turboshaft engine with 2,000 horsepower.

The Twin KingCobra first flew on 10 September 1971. It looked much like an AH-1J, except for a longer and distinctive "buzzard beak" nose and a ventral fin like that on the original Model 209 demonstrator. However, there were significant changes that were less noticeable:

The primary weapon of the KingCobra was to be the new wire-guided "BGM-71 TOW" anti-tank missile, which had proven highly effective in combat test firings in Vietnam from Huey gunships. This weapon could be carried in a pack of four missiles, with one pack under each stub wing. On launch, the TOW trailed out wires to communicate command guidance updates.

The missile had two infrared flares on its tail to allow the SMS to track it. All the gunner had to do was keep the target in his sight, and the missile fire control system adjusted its flight appropriately. Both the gunner and the pilot had Sperry Univac helmet-mounted sights to allow them to acquire targets for the KingCobra's missiles and gun.

A long-span "big wing", 4 meters (13 feet) wide, was designed for the KingCobra, but apparently never fitted except as a static mockup. The "big wing" was to provide additional fuel and stores capacity.

The single-engine KingCobra first flew in January 1972. Other than engine fit, it was almost identical to the twin-engine KingCobra. In fact, the the single-engine prototype was wrecked in an accident in April, and to complete US Army evaluation the twin-engine KingCobra was modified to the single-engine configuration.

The evaluation, which pitted the KingCobra against the Lockheed Cheyenne and the Sikorsky S-67 in a competitive fly-off, began in the spring of 1972 and was completed in July. In August, somewhat to everyone's shock, the Army rejected all three helicopters!

* The simplest way to explain such a drastic action was that the Army's requirements had changed enough to require a serious rethinking of their helicopter gunship requirements, and the whole AAFSS program had become completely bogged down in politics anyway. The cancellation of AAFSS was immediately followed by the initiation of a new "Advanced Attack Helicopter (AAH)" program.

The Army specified that the AAH was to be powered by twin General Electric T700 turboshaft engines with 1,500 horsepower each, the same powerplant fit specified for a new Army utility helicopter competition that would be won by the Sikorsky S-70 Black Hawk. The AAH would be armed with a 30 millimeter cannon and sixteen TOW anti-tank missiles. The missile armament specification was later modified to include an alternate load of 16 "AGM-114 Hellfire" anti-tank missiles. Hellfire was then in development and promised greater range and lethality than TOW.

Boeing-Vertol, Bell, Hughes, Lockheed, and Sikorsky all submitted proposals for the AAH program. In June 1973, Bell and Hughes were selected as finalists, and were each awarded contracts for the construction of two prototype aircraft.

The Bell entry, the "Model 409" or "YAH-63", was by no means "just another Cobra design", though it leveraged off Cobra technology where possible. Although it had what had become by then the typical configuration for a helicopter gunship, with a sharklike fuselage, tandem crew seating, and stub wings for armament, the YAH-63 was largely a new machine.

Distinctive features included wheeled tricycle landing gear; flat canopy window plates; an unusual "tee" tail; a large ventral fin; and a three-barreled GE XM-188 30 millimeter cannon. One less noticeable feature was that the pilot occupied the front seat rather than the back, the reverse of the AH-1's arrangement. This was felt to be more prudent as the YAH-63 was intended to fly "in the treetops", or what is more formally called "nap of earth (NOE)" operations.

The first prototype of the YAH-63 made its initial flight on 1 October 1975. This rotorcraft crashed in June 1976, but a static test prototype was brought up to flight standard and, along with the second prototype, entered the flyoff against the Hughes entry, the "Model 77" or "YAH-64".

The YAH-64 was selected the winner in December 1976, and entered service as the "AH-64 Apache". The Army felt the YAH-63's two-blade rotor was more vulnerable to damage than the Apache's four-bladed rotor, and the service didn't like the YAH-63's tricycle landing gear scheme, feeling it was less stable than the Apache's "taildragger" configuration. Some observers also suspected the Army didn't want to divert Bell from of AH-1 production.



* In December 1971, Bell signed a contract for $708 million USD with Iran to deliver 287 Model 214 Huey utility helicopters, and 202 improved AH-IJ Cobra gunships. The improved Cobra, known as the "International AH-1J", that resulted from this contract featured an uprated P&WC T400-WV-402 engine and stronger drive train to support 1,675 horsepower continuous. Recoil damping gear was fitted to the 20 millimeter gun turret, and the gunner was given a stabilized sight and even a stabilized chair.

62 of the International AH-1Js delivered to the Shah's forces were TOW-capable, while the rest were not. Bell also delivered eight TOW-capable International AH-1Js to Korea in 1978. It is possible that the Iranian International AH-1Js saw some combat against Iraqi forces in the later half of the 1980s, but they have all likely been grounded by lack of spares now.



* Although the US Army had selected the AH-64 to deal with hordes of Red armor, the Apache was not going to be ready for some time. Once more, the Army turned toward the Cobra as the "interim solution".

In March 1972, the service requested that Bell investigate arming the existing AH-1G with the TOW missile under the "Improved Cobra Armament Program (ICAM)". Bell promptly fitted eight AH-1Gs with the new Bell-Hughes XM26 "Telescopic Sighting Unit (TSU)" in the nose, and two M56 four-pack TOW launchers, with one launcher under each stub wing.

The M56 launchers were fitted to the outboard pylons, while the inboard pylon could still accommodate an unguided rocket pod or other stores. In some cases, twin-tube TOW launchers were fitted rather than quad-tube launchers, but this seems to have been an unusual fit. These eight Cobras were redesignated "YAH-1Q", and performed a long series of TOW test firings from early 1973 through early 1975.

The Army felt the YAH-1Q met their short-term needs, and ordered conversion of 101 AH-1Gs to the "production" AH-1Q "TOWCobra" configuration, featuring the M56 TOW launchers, the M65 production version of the M26 TSU, and Sperry-Univac helmet-mounted sights. The first AH-1Q was delivered to the Army in early 1975.

* Even as the AH-1Qs were going into operation, however, everyone realized they didn't have the power to carry the heavy quad TOW launchers and still easily perform NOE maneuvers. In 1975, the Army began the "Improved Cobra Agility & Maneuverability (ICAM)" program to address this problem. Bell fitted an AH-1G with an uprated Lycoming T53-L-703 turboshaft with 1,800 horsepower and a new drive train, with the result redesignated the "YAH-1R". An AH-1Q was converted to a similar configuration, and redesignated the "YAH-1S".

The new engine fit was satisfactory, and the Army ordered conversion of all 92 surviving AH-1Qs, plus 198 AH-1Gs, to the new configuration, with minor additional refinements such as the "sugar scoop" exhaust deflector. They were variously known as the "Improved AH-1S", "AH-1S Modified", or "AH-1S(MOD)", and blessedly redesignated "AH-1S" in 1988. For convenience, this variant will be simply referred to as "AH-1S" in the following discussion.

The last AH-1S conversion was delivered in early 1979. Fifteen of the AH-1S Cobras were converted by Northrop to specialized "TH-1S" trainers in the mid-1980s. The gun turret was removed and replaced with a plug, and they were fitted with the "Passive Night Vision System (PNVS)" from the AH-64 Apache and blackout curtains for the pilot. They were intended to be used to train Apache pilots in night landing techniques.

* The AH-1S led to a series of TOWCobra refinements, or "Steps". The "Step 1" variant was the new-build "Production AH-1S" or "AH-1S(PROD)", which was redesignated "AH-1P" in 1988.

100 AH-1P TOWCobras were built and delivered to the Army in 1977 and 1978. They featured a still further uprated engine system, as well as a distinctive new "flat plate" canopy. Although the new canopy gave the Cobra a more businesslike "flying tank" look, the change was made to reduce the glint off the window glass and did not include armor glass.

The AH-1P also featured an updated instrument panel for NOE flight; a radar altimeter and improved radios; a radar warning receiver; and, from the 67th production unit onward, Kaman K-747 composite rotor blades with tapered tips. The K-747 rotor blades were also retrofitted to older Cobra variants. Some of the gunships were temporarily refitted with metal blades in the mid-1980s, when a few K-747 composite blades lost their tips due to bonding problems, but this issue was quickly resolved.

* The "Step 2" variant was originally known as the "Up-Gun AH-1S", "AH-1S Enhanced Cobra Armament System", or "AH-1S(ECAS)", but was redesignated as "AH-1E" in 1988. All Army Cobra variants to this time retained the old TAT-141 turret, but the AH-1E featured the three-barrel 20 millimeter M197 cannon and universal turret introduced on the Marine AH-1J.

The AH-1E also featured an improved stores management system for 70 millimeter rockets, an improved sighting system, and a more powerful electrical generator to support the new stores management system. 98 new-built AH-1Es were delivered in 1978 and 1979.

* The "Step 3" variant was originally designated the "Modernised AH-1S", "AH-1S Modernised Cobra", or "AH-1S(MC)", but was redesignated "AH-1F" in 1988. It was the US Army's final operational standard for the Cobra gunship.

The AH-1F featured all the improvements of the AH-1P and the AH-1E, along with numerous refinements. The AH-1F had a new fire-control system with a laser rangefinder; a new computer; secure voice communications; a head-up display (HUD) for the pilot; an AN/ALQ-144 IRCM unit mounted above the engine; a cable cutter above and below the cockpit to protect the Cobra in NOE flight; and a long exhaust pipe to reduce the helicopter's infrared signature. The AH-1F had a distinctive blister at the front of the rotor transmission system housing for a laser spot tracker, but this sensor was never fitted.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   rotor diameter          13.4 meters         44 feet
   fuselage length         13.6 meters         44 feet 7 inches
   footprint length:       16.2 meters         53 feet 1 inch
   height                  4.09 meters         13 feet 5 inches

   empty weight            2,995 kilograms     6,600 pounds
   max loaded weight       4,535 kilograms     10,000 pounds

   maximum speed           225 KPH             14O MPH / 120 KT
   service ceiling         3,720 meters        12,200 feet
   range                   510 kilometers      315 MI / 275 NMI
   _____________________   _________________   _______________________

Two AH-1Ps were converted to AH-1F prototypes. 99 new-build AH-1Fs were built for the US Army and 50 were built for the US Army National Guard (ANG) from 1979 through 1986, which were the last new-build single-engine Cobras built for the US. In 1986, the US Army had 1,100 Cobras in their inventory.

378 AH-1Gs were also converted to AH-1F specification from 1979 through 1982, including 41 dual-control TAH-1F trainers.

* The AH-1F was the focus of small and incremental updates, such as a new engine air filter; improved rotor swashplate; laser warning sensor; Stinger air to air missile (AAM) support; and the the "Cobra Night Attack (C-NITE)" system, which gave the gunship a day-night, all weather TOW capability.

However, the machine was still becoming increasingly outdated, and was phased out of US Army combat service in 1999, with the type still retained in Army National Guard service in declining numbers. A few appear to remain in Army service in specialized roles. Two have been converted to drone configuration to experiment with robot gunships, and there has been talk of using the old AH-IFs as target drones.



* Although only 69 examples of the Marine AH-1J SeaCobra were built, the service had planned to acquire 124. However, the Marines wanted TOW capability and more power, and midway through planned production, two AH-1Js were converted to prototypes of a new SeaCobra variant, the "AH-1T". The first AH-1T prototype flew on 20 May 1976 and proved very satisfactory.

The AH-1T featured a new P&WC T400-WV-402 Twin Pac engine with 1,970 horsepower, plus a new transmission system taken from the Bell 214, a bigger 14.6 meter (48 foot) rotor with wider chord and swept tips, and a bigger tail rotor. The tailboom was lengthened to accommodate the new rotor system, resulting in a visible "kink" where the tailboom joined the fuselage. The forward fuselage was extended slightly as well to balance the longer tailboom, with the additional space allocated to increased fuel tankage. The AH-1T also had a small ventral fin.

A total of 59 production AH-1Ts were built. Due to funding problems, the first 33 did not have TOW capability, but the last 24 were fitted with nose sights and Sperry-Univac helmet-mounted sights for TOW compatibility, and the survivors of the first 33 were eventually brought up to this standard. Modifications were later added to allow them to carry the Hellfire missile.

* In the late 1970s, Bell considered the AH-1T design as the basis for a new Cobra variant to be sold to Iran, and developed a prototype of an "AH-1T+" with twin GE T700-GE-700 providing 1,258 horsepower each and Hellfire capability. The fall of the Shah eliminated all prospects of a sale, but Bell did not abandon the effort, flying the AH-1T+ demonstrator in April 1980.

This was something of an exercise in faith, since the most likely remaining customer, the US Marine Corps, really wanted to buy the AH-64 Apache. However, Bell's gamble paid off, since in 1981 Congress refused to provide funding for the Apaches, and the Marines were forced to settle for "yet another warmed-over Cobra".

Bell was determined to give the Marines their money's worth, and reworked the AH-1T+ with a more powerful dual GE T700-GE-401 turboshaft power pack providing a total of 3,380 horsepower, as well as a wide range of other changes: new "cheek" fairings to accommodate missile guidance electronics; an ALE-144 IRCM unit; AN/ALE-139 chaff-flare dispensers mounted on top of the wingtips; and new engine nacelles and exhausts with infrared suppressors. The resulting "SuperCobra" prototype was first flown on 16 November 1983, and was painted with a gold cobra running down its length.

The production rotorcraft was redesignated "AH-1W". An initial order for 44 and a single TAH-1W trainer was followed by an additional order for 34, and 39 surviving AH-1Ts were upgraded to the AH-1W specification.

The "Whiskey Cobra" was qualified for a large number of stores, including TOW; Hellfire; twin-pack Stinger AAM launchers; the AIM-9L Sidewinder AAM; and the AGM-122 SideARM anti-radar missile, which is just an old AIM-9C Sidewinder with a radar seeker. 290 liter (77 gallon) external tanks are also carried, and "iron bombs" and cluster bomb units have been qualified though not used in practice. The Marines also qualified a new "sabot discarding armor piercing" round for the M197 cannon to improve its ability to kill armored vehicles.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   rotor diameter          14.6 meters         48 feet
   fuselage length         13.9 meters         45 feet 6 inches
   height                  4.44 meters         14 feet 7 inches

   empty weight            4,950 kilograms     10,920 pounds
   max loaded weight       6,690 kilograms     14,750 pounds

   maximum speed           278 KPH             173 MPH / 150 KT
   service ceiling         4,270 meters        14,700 feet
   range                   518 kilometers      322 MI / 280 NMI
   _____________________   _________________   _______________________



* The AH-1T that was modified to the AH-1T+ demonstrator and AH-1W prototype was later fitted with an advanced composite four-bladed rotor system that provided better performance, less noise, and greater resistance to battle damage. This "Four Bladed Whiskey (4BW)" Cobra didn't lead immediately to a production contract and the rotorcraft was returned to Marine service in a normal AH-1W configuration, but Bell continued development of the concept to come up with a new "AH-1Z" SuperCobra.

With the end of the Cold War, funds for buying new weapons dried up, and the US armed services increasingly had to make do with upgrade programs to bring their current weapons up to date. In 1996, the Marines signed a contract with Bell to upgrade 180 AH-1W SuperCobras to the AH-1Z standard.

The "Zulu Cobra" features a new, quieter four-blade composite rotor with an automatic folding mechanism to make the helicopter easy to store on ship, a 10,000-hour lifetime, and the ability to survive hits by 23 millimeter projectiles, as well as a new gearbox, transmission, and auxiliary power unit (APU). The new APU is the same as that used on the Sikorsky S-70 Black Hawk helicopter. A four-blade tail is also fitted. Fuel capacity is increased by 758 liters (200 US gallons), and the fuel tanks are filled with inert gas as they are emptied to reduce fire hazard.

The AH-1Z upgrade also increases stores capability to six wing stations, including two wingtip stations for missiles like the Sidewinder or Sidearm, and four for unguided rocket packs, or TOW or Hellfire quad missile launchers.

Cockpit and avionics are upgraded as well. The new cockpit features two multifunction 15 by 20 centimeter (6 by 8 inch) flat-panel displays for each crewman; secure radio communications; a tactical digital data system; a inertial-navigation system incorporating a GPS receiver; and a digital map display. Both sets of cockpit controls are largely identical, allowing either crewperson to fly the helicopter or fire its weapons. A rudimentary backup cockpit flight-control panel operated off battery power is also provided for each crewperson so that the AH-1Z can "limp home" if its AC power system is disabled.

The AH-1Z is fitted with a nose-mounted AN/AAQ-30 "Hawkeye" Target Sighting System (TSS), featuring a FLIR imager, low-level-light color zoom TV, a laser rangefinder, and an "eye-safe" laser target designator. The new FLIR imager is the key to the TSS. Earlier FLIRs didn't have the range to allow combat crews to identify a target from more than a few kilometers away, but the third-generation FLIR used in the TSS has large-aperture optics and an extremely effective stabilization system, allowing target identification from beyond the range of the Hellfire missile.

Zulu Cobra flightcrews will be fitted with advanced flight helmets developed by BAE Systems of the UK that are one of the core elements of the flight system. The helmet features a high-resolution projection TV system that can display flight or targeting data and imagery on the visor in a "see-through" fashion, and also can be fitted with snap-in cameras to provide a highly integrated night-vision capability. The helmet weighs only 2.2 kilograms (4.8 pounds) with the cameras in place.

Other system enhancements include a new self-defense suite, airborne target handoff system, an onboard systems monitor, two mission computers, and a mission data loader. The self-defense suite includes four ALE-47 chaff-flare dispensers that can be set to manual, semiautomatic, and fully automatic modes, along with an APR-39A radar warning receiver, an AVR-2 laser-warning unit, and and AAR-47 missile warning unit.

The AH-1Z is stretched to accommodate the new hardware and preserve its center of balance, and the airframe has been "zero-lifed". The upgraded SuperCobra carries 450 kilograms (1,000 pounds) more payload than the AH-1W, and cruises at 290 KPH (180 MPH), 40 KPH faster than the AH-1W. Combat radius for the AH-1Z is 200 kilometers (125 miles), while the combat radius of the AH-1W is only 70 kilometers (44 miles). The AH-1Z has a maximum takeoff weight of 8,390 kilograms (18,500 pounds), compared to 6,690 kilograms (14,750 pounds) for the AH-1W.

First flight of a prototype AH-1Z was in late 2000, with initial remanufacture of operational aircraft beginning in 2003 and last delivery in 2013. The Marines plan to use the AH-1Zs through at least 2020. Cost of each upgrade is $11.5 million USD, and each upgrade takes 13 months.



* Although the US was not eager to engage in military interventions in the post-Vietnam "hangover" in the 1970s, such interventions were resurrected during the US Reagan Administration from 1980 to 1988, and increased with a vengeance in the 1990s, with the chaos following the fall of the Soviet Union. The Cobra has been a significant weapon for such foreign expeditions:



* Aside from the 202 International AH-1Js sold to Iran before the fall of the Shah, the Cobra has been obtained by a number of international buyers. Exact details of these foreign sales are not always clear, but it is possible to construct an outline:

In the mid-1990s, Romania tried to cut a deal with Bell for a locally-assembled Cobra variant, the "AH-1RO", but it didn't happen. The Philippines also apparently ordered a number of Cobras, but it appears this deal fell through.

* There were a few one-off Cobra modifications and applications that are worth noting here:



* When I was down at Fort Hood, Texas, from the spring of 1973 to the late summer of 1974, I became very familiar with the Cobra. I learned to distinguish different helicopters by sound, and the Cobra had a particularly aggressive sound to it. I used to see Cobra aircrew, lieutenants and warrant officers generally, in the base PX, wearing flight jumpsuits with oversized cobra patches.

I was a signalman, operating the popular Canadian Marconi AN/GRC-103 telecom radio relay set. One day we were setting up, as usual on top of a hill to get a clear field of view for the antenna. We'd staked down the antenna base, and I was sitting on top of it, straddling the antenna mast and fitting the "flyswatter" antenna, when I heard the distinctive sound of a Cobra.

I looked around, a little baffled since I had a clear view of the entire countryside, but I couldn't see the Cobra even though it was loud enough to be nearby. Then I looked down the hill and saw it coming up at me. In hindsight, this was a little creepy, since if it had been a real war it would have "ruined my whole day", as they liked to say.

* I was very surprised at how big this writeup turned out to be. If you tinker with something for going on 40 years, it gets a lot of history behind it. Trying to sort out all the minor variants was tricky, particularly because of the disorderly designation schemes. I used to pick on the Russians for having confusing designation schemes, but after writing this document I'll have to stop griping about it.

It is interesting to see how the Cobra has changed over its lifetime. The original Model 209 demonstrator was a sleek little "flying sports car", but after adding the flat-plate canopy, more formidable armament, and an array of sensors, it looks a lot more like a "flying tank", while still being recognizably the same rotorcraft.

* Sources include:

* Revision history:

   v1.0   / 01 mar 01 / gvg
   v1.0.1 / 01 sep 02 / gvg / Minor cosmetic update.