As the conflict in Vietnam raged, the UH-1 Huey was modified into a gunship, but the ubiquitous helicopter was slow and underpowered at times, thus prompting the need for a dedicated attack aircraft.
Bell Helicopter had anticipated the eventual need for a pure attack helicopter and had already started research and development even before the conflict in Southeast Asia. This gave Bell the upper-hand when the Unites States Army would request just such a machine for close air support and escorting troop transport helicopters over the dense jungles of Vietnam.
Bell’s Early Efforts
1958 saw the Bell D245 Combat Reconnaissance Helicopter design, a narrow-body gunship concept. The design was presented to the United States Army’s 7292nd Aerial Combat Reconnaissance Company, but with no applicable doctrine or priority given to armed helicopters, support waned and eventually the idea died.
Despite the lack of interest by the Army, Bell continued the work, funding the research within the company. Bell intended to design an attack helicopter utilizing many existing components used on the UH-1.
The result of these efforts produced the D255 Iroquois Warrior in June 1962. The D255 featured tandem ‘stepped’ seating with both a pilot and a gunner seated in a narrow fuselage with stub wings and a streamlined ventral gun pod along with a nose turret.
The design produced excellent visibility for the crew members as well as presenting a slender target when viewed head-on. The aerodynamics offered good handling characteristics along with improved delivery of ordinance. They finally got the Army’s attention.
In December 1962, after the Army allocated funds for researching and developing an attack helicopter, Bell received approval to build a testbed aircraft. The result was the Model 207, a combination of OH-13S and Model 47J-2 components. Known as the Sioux Scout and completed in 1963, trials made an impression and the Army asked for a similar aircraft only with a turbine engine.
Meanwhile, in 1964 the Army presented a Request for Proposal (RFP) known as the Advanced Aerial Fire Support System (AAFSS). Keeping the United States Air Force (USAF) in the dark with somewhat ambiguous specifics but stringent requirements, several manufacturers went to work designing dedicated close air support (CAS) aircraft.
Lockheed produced the AH-56 Cheyenne design while Sikorsky’s entry was known as the S-66 Blackhawk. Both these designs were chosen for further evaluation by the Army, while Bell’s entry, the D262, a version of the Iroquois Warrior, was eliminated from the competition.
Undaunted, Bell continued work on the idea, convinced they could produce what the Army needed. In January 1965, engineers at Bell took the proven components from the D262 and the Super Sioux and produced a prototype. The idea was to convince the Army that a short lead time and low development cost could result the Army having the helicopter in service much quicker.
The Bell Model 209
Bell’s efforts produced the Model 209 that again featured a narrow fuselage with a crew of two sitting tandem in tiered seats. The co-pilot/gunner was seated in the front and lower seat, with the pilot seated behind and above. An Emerson Electric turret located on the chin of the aircraft contained a GAU-2B/A 7.62 mm minigun. Stub wings provided both lift and hard points for various ordinance and weapons.
The 209 received power from a Lycoming T53-L-11 turbine engine producing 1,100 shp (shaft horsepower). The transmission and rotor system was that of the UH-1C. The traditional stabilizer bar system was replaced by a Stability Control Augmentation System (SCAS) which reduced weight. The landing skids retracted allowing for less drag and a wider firing radius for the chin turret.
Bell called the new helicopter the Cobra, bucking the tradition of naming Army helicopters after Native Americans. A distinctive collective-lever in the shape of a cobra snake’s head supported the branding.
The first Model 209 prototype flew Sept. 7, 1965, and on Oct. 25 the helicopter broke the world speed record for its weight class of 180.1 mph when it recorded a sustained speed of 200 mph. Meanwhile, the UH-1C, incorporating a more powerful engine than previous models, struggled to keep pace with the CH-47 Chinook transports they were escorting in the skies over Vietnam.
The capable Lockheed AH-56 would not be available until 1970 and things were heating up in Southeast Asia. The Army would need something to fill the gap and soon.
Bell had made a presentation to the Army in August 1965 on the need for a faster and heavily armed helicopter for escorting transports in Vietnam. They suggested the Model 209 could be put into production rapidly utilizing UH-1 components, and pointed out the AAFSS was not arriving in time. The Army agreed with Bell, however the helicopter would not be considered for adoption without facing contenders from other companies.
The contenders the 209 faced were converted and modified utility helicopters already in existence. Only the Bell entry was designed from the beginning as an attack helicopter, and after a two-month trail at Edwards Air Force Base in California, the Model 209 was chosen by the Army. Finally, on April 4, 1966, a contract with an order for two preproduction prototypes was awarded to Bell.
The AH-1G Cobra
Designated the AH-1G, the Army placed an order for 110 Huey Cobras on April 13, 1966. The designation stood for ‘Attack Helicopter Type 1’. 838 AH-1s would be ordered by late 1968, with a total of 1,126 being purchased by the Army and Marine Corps when production of the G model ended in 1973.
Changes to the production models included the Avro Lycoming T53-L-13 engine replacing the L-11, producing 200 more horsepower. This gave the Cobra a cruising speed of 166 mph and a dive speed of around 220 mph. Self-sealing fuel tanks gave the aircraft a range of 362 miles. Maximum takeoff weight was 9,500 lb, and the service ceiling was 12,700 ft.
The retracting landing skids were replaced with fixed skids and the ventral tail fin extension of the 209 was eliminated, along with the distinctive cobra head collective-lever. Armor plating was added to protect vital systems and components. The crew also received armored seats, nose plate, armored side panels and a bulletproof windshield. The tail boom was carried over from the UH-1C, and most antennas were mounted flush or within the airframe to improve aerodynamic efficiency.
Initial production AH-1s had an Emerson Electric TAT-102A turret housing a single GE XM-134 7.62 mm minigun capable of firing 4,000 rounds per minute, but later production saw a TAT-141 turret with a GAU-2B/A minigun along with a M-129 40 mm grenade launcher, which could also be configured to carry two of the same of either of these weapons. The miniguns had a 4,000 round supply and the grenade launchers had 231 rounds available.
The gunner would normally control and fire the turret weapons utilizing a pantographic sighting system, but the turret weapons could also be fired by pilot if in the fixed-forward position. The gunner also had the capability of flying the aircraft if need be.
The stub wings could carry various types of ordinance on four pylons, including rocket pods, minigun pods, or even a six-barrel M61A1 20 mm cannon. These weapons were fired by the pilot using the Mk-18 adjustable rocket sight, with the gunner having the capability to fire the weapons as well in an emergency. The AH-1G Cobra carried up to 76 of the 2.75 in rockets.
Cobras Unleashed
First to receive the Cobras in Vietnam was the 334th Assault Helicopter Company (AHC) in late September 1967. The unit’s 1st Platoon, known as The Playboys, traded their UH-1Cs for the sleek new AH-1s and saw their first combat mission on Oct. 8. Four enemy bunkers and fourteen sampans were destroyed that day.
The speed and slender silhouette of the Huey Cobra proved a challenge to enemy gunners, and increased dive angle, maneuverability, and weapons allowed Army pilots to do things normally limited to fixed-wing aircraft. Soon the Cobras developed a reputation among friend and foe alike as the snake that bites.
The stifling heat of Southeast Asia coupled with the large canopy area heated up the enclosed cockpit making them unbearable. Small powerful air conditioners were soon installed to solve the problem. In addition, pilots used to relying on their door gunners when flying the UH-1s soon realized those extra eyes and ears were no longer present, along with their suppressive fire from the sides of the aircraft. Despite these shortcomings, the AH-1 found great success operating in Southeast Asia.
During the Tet offensive of February 1968, Cobras decimated communist forces during attacks at Tan Son Nhut Airbase, Bein Hoa, and even around the Saigon area, where the AH-1 was credited as a key component in defeating the communists. The ability to rapidly deploy as opposed to fixed-wing aircraft and the pinpoint accuracy of the helicopter’s weapons had demonstrated the effectiveness of the Cobras.
Before the conflict was over, AH-1s would be found performing a variety of missions including serving with Aerial Rocket Artillery Batteries, Air Calvary, Aerial Weapons Companies, Assault Helicopter Companies; flying escort or providing firepower on call to troops on the ground, assisting with rescues, or whatever would be asked of them.
The spring of 1972 saw the Cobra’s first confrontation with enemy tanks during an enemy offensive that saw one AH-1G unit destroy or damage over 20 tanks, most of them with unguided rockets. The aircraft were in the hands of F-Battery, 79th Aerial Field Artillery, 1st Calvary’s 3rd Brigade. Two helicopters were lost to heat-seeking SA-7 surface-to-air missiles (SAMs), resulting in the installation of an upturned exhaust directed into the main rotor to reduce infra-red signatures. ALQ-44 infra-red kits were also installed.
During the war, another modification that took place was moving the tail rotor from the port side to the starboard side to improve directional control, as the large tail fin was sensitive to tail winds.
A total of 38 AH-G models were diverted to the United States Marine Corps in 1969, taking on many of the same missions as those with the Army, with the addition of armed observation and assuming many roles previously done by UH-1s. The Marines eventually received their own version of the Cobra, a twin-engine model known as the Sea Cobra and designated the AH-1J.
Because of urgent needs during the Vietnam War, the deadly attack helicopter known as the Cobra was born. Both the United States Army and Marines utilized the helicopter with great effectiveness in Southeast Asia, despite the loss of nearly 300 Army and 10 Marine aircraft to both operational and combat causes.
The AH-1 design continued to be modified and upgraded and still serves several nations as well as private enterprises and even emergency services, although the United States Army retired the Cobra in 2001. The U.S. Marines and a handful of other countries still operate a version known as the AH-1Z Viper.
