Improving the breed
The UH-1B to UH-1P
The introduction of the UH-1A into ser vice had revealed restrictions in the performance of the aircraft particularly in hot and high environments. In July 1959, the US Army issued a contract to produce four prototypes of a new version of the helicopter, one which was to solve these issues and spawn an incredible series of variants.
Even though the first production variant of the Bell UH-1, the UH1A was considered an evaluation and trials version of the type by the US Army, it was already proving its reliability and adaptability in the medevac and armed helicopter escort roles on active service in Vietnam. Prior to these first deployments, the US Army had recognised the need for greater power and performance from the helicopter, particularly during an exercise held in Panama and earthquake relief mission in Chile, where the heat and altitude reduced the useful payload of the UH-1 and limited its mission effectiveness. Bell was already considering a number of improvements to the rotor and airframe and Lycoming had developed a more powerful version of the T53. All of these were discussed with the army, resulting in a contract in July 1959 for four prototypes designated YUH-1B, the first of these flying on April 27, 1960.
The new variant of the engine, the T53-L-5, produced 960hp, an increase in power that was absorbed by a redesigned main rotor. The blades were increased in chord from the original 14in (35.56 cm) to 21in (53.34 cm) wide but retained the original span of 44ft (13.41m). The blades were now made with an extruded aluminium D section leading edge spar covered in a protective stainless steel anti-erosion strip. Behind the spar the body of
the blade was built with a lightweight honeycomb core covered in a glass fibre skin, making the new blades both stronger and lighter than those of the earlier Hueys. The most obvious change was in the rotor mast, which was increased in height by 13in (33.02cm) giving the main rotor greater ground clearance and improving its aerodynamics. The cabin was enlarged again and was now able to accommodate three stretchers, two ambulatory casualties and a medical attendant in the medevac role. As a transport, two aircrew and seven troops and their equipment could be carried or the canvas seats could be quickly and easily removed and up to 3000lb of cargo loaded internally. The maximum loaded weight of the Huey had increased from 5800lb (2631kg) in the UH-1A to 8500lb (3850kg) in the B model, nearly a third increase in load lifting capability. The US Army began testing the first UH-1BS in November 1960 with the first production aircraft entering service in March the following year. Two sub-types were designated, a single NUH-1B which was used for testing a variety of new systems and a pair of GUH-1BS which were ground instructional airframes. With the deployment of UH-1AS to Vietnam with the Utility Tactical Transport Helicopter Company (UTTHCO) in October 1962, the limitations of the early armed Huey became apparent as they carried out their role as armed escorts to larger transport helicopters. These first field modifications allowed both rockets and machine guns to be carried, but fixed in the direction of the line of flight, limiting their usefulness. The increased lifting capacity of the UH-1B allowed a greater range of weapons to be carried; to complement this a variety of mounts were developed to improve the UH-1S offensive and defensive capabilities. A complete description of the weapons systems and mounts developed for the Huey would fill this issue on its own, so the major systems fitted to the early ‘short body’ models are listed in the accompanying table.
XM156/M156 – The first ‘universal’ mount developed for a variety of weapons, usually fitted on the fuselage sides at the rear of the cabin under the centre of gravity. During trials these were also fitted at the forward end of the cabin, a practice used rarely on operational aircraft due to centre of gravity limitations. A similar mounting, known as a Kellett pylon had been developed by UTTHCO during early 1963 and allowed a similar variety of weapons to be carried, including bombs and napalm tanks, but these were quickly replaced by the M156 on service aircraft. Both types could be fitted with two pylons per mount for weapons, or carry a single pylon with machine guns mounted on the ends. Fitted to examples of all of the early models of the UH-1.
XM6/M6 – The famous ‘Quad’ or ‘Flex’ gun system was the first to use the new M156 mounts with four M60C 7.62mm machine guns fed by electric drive motors from ammunition boxes in the cabin. Trials took place in the forward and rear mounted position, the latter becoming standard on operational aircraft.the M6, as it was designated in May 1963, could also be fitted with four twin tube MA-2/A 2.75in rocket launchers on each mount.this was a tremendous increase in firepower and capability for the UH-1, not least because the co-pilot could steer the guns by depressing a ‘dead man switch’ on the pantographic sight mounted in the roof.this sight allowed the guns to be elevated up to 15º above or depressed to 60º below the helicopters line of flight, or moved up to 12º inboard or 70º outboard, the guns having a safety cut off to prevent firing into the fuselage. If the deadman switch were released, the hydraulically driven mounts automatically returned to the fixed forward position, the pilot being able to fire them in this mode using the trigger on his cyclic.the four guns fired 2200 rounds a minute, the ability to offset them from the line of flight making them far more effective than the earlier mounts. Simple and reliable, the M6 system often had rocket launchers added in the field, the additional firepower being further supplemented by door gunners with bungee slung M60 machine guns.a development, the XM9, saw the four M60 machine guns removed and two M75 40mm grenade launchers fitted in their place, but this was not widely adopted.the M6 was fitted to the UH-1B and C models. XM16/M16 – A development of the M6, this added two M157 or M158 rocket pods to the M156 universal mount along with the four machine guns. Both pods contained seven tubes for 2.75in rockets and were aimed via an M60 reflex sight mounted in the cockpit. Like the M6, this system was fitted to both UH-1B and Cs.
XM17/M17 – The Kellett two pylon mount was used to fit four M159 rocket pods carrying 19 2.75in rockets each, a system fitted to a number of UTTHCO UH-1BS and Cs.there is some evidence to suggest a version based on the M156 mount was also tested, but the weight of the M17 system limited its usefulness and it was not widely adopted.
XM21/M21 – Another development of the M16 system in which the four M60 machine guns were replaced by a pair of M134 six barrelled machine guns known as Miniguns.the high speed rate of fire was a devastating 4800 rounds per minute with both guns firing together. Either the original seven tube or a 19 tube rocket launcher could also be carried on the M156 mount.
XM22/M22 – Experiments to fit guided missiles to the UH-1 began with the AGM-22A, a licence built version of the Nord S-11 wire guided anti-tank missile aimed via an XM-70 sight.the M22 system was developed from this, six missiles being carried, three on each side of a UH-1B or C on an extended M156 mount.the M22 system had a number of improvements over the early trials, including the upgraded AGM-22B missile and the XM58 stabilised sight.the first 12 UH-1BS with the M22 system were deployed to Vietnam in September 1965, but saw limited use due to the lack of suitable targets. One other system was developed to use the AGM-22, built by Warrant Officer Robert Maxwell in theatre.the Maxwell system as it became known adapted the M3 weapons system fitted to his unit’s helicopters by removing one or two banks of six rockets from the 24 tube packs on either side of the UH-1. A custom built short pylon was then added to the outside of the M3 packs with a launch rail for a single AGM-22B.
XM26/M26 – The second generation of anti-tank missiles were also carried by the UH-1 in the form of a triple tube launcher pod for the Hughes BGM-71 TOW developed in 1963.These pods were supported by a specialised raised pylon, the system including the sight and sensor turret mounted in the copilot’s nose glazing. Two UH-1BS, 62-12553 and 62-12554, were modified and firing trials were conducted in Germany in 1964.The development of the AH-56 attack helicopter cancelled the UH-1 TOW programme and these aircraft were stored.the Easter Offensive and the increased use of armour by the North Vietnamese Army in 1972 meant the two TOW Hueys were deployed to Pleiku with the 1st Air Battalion. Here they were a decisive factor in the Battle of Kontum in late May, striking 47 targets which included 24 tanks.
XM29 – The bungee mounted door guns on the UH-1BS and Cs had a number of shortcomings, so the XM29 pintle mount was developed to support an M60D 7.62mm machine gun. While more effective than the bungee cords, the mount meant that no other armament could be carried so limited its use. Due to this, a frame mount that could swing out from the rear of the cabin was developed, known as the Sagami mount.this could take a single or pair of M60s, an M2HB machine gun or an M134 Minigun and was fitted to UH-1BS, Cs, Fs, Ps and Ms, including those of the US Navy.
XM50/M50 – A number of UH-1BS, Cs and Ms were fitted with both the M5 and M16 or M21 armament systems, designated M50 in combination.
XM52/M52 – An oil tank and pump were mounted in the rear cabin under the seats which sprayed oil into a ring of nozzles in the engine exhaust.this produced a thick white smoke for up to three minutes to cover assault landings and was best delivered at less than 90kts (166kph) and 50ft (15.2m) in altitude.
US AIR FORCE
XM93/XM93E1/M93 – Two M134 Miniguns were fitted on door mounts in USAF UH-1FS and Ps.the E1 version of the system included an M60 reflex sight for the pilot who could fire the guns remotely when locked forwards. A separate mount and pylon was often fitted along with the door guns to carry a pair of seven tube rocket launchers of varying types.
XM94/M94 – As per the XM93, but one or both of the M134 Miniguns was replaced by an M129 40mm grenade launcher. This system was also fitted to USAF UH-1FS and Ps.
US MARINE CORPS
TK-2 – The US Marine Corps developed the Temporary Kit 2 weapons system for its UH-1E helicopters, designing and fabricating its own mounts to support two M60C 7.62mm machine guns on each side of the rear cabin. Outboard of these a single pylon was fitted at the end of the mount and could take a variety of weapons, most frequently seven tube rocket launchers, but could also carry General Electric SM-14 pods housing Browning .50 cal machine guns.the first of these kits was delivered to VMO-6 at Camp Pendleton in January 1965.
TAT-101 – The Emerson Tactical Armament Turret 101 was only fitted to US Marine Corps UH-1ES and consisted of two M60 machine guns mounted under the centre of the nose with 1000 rounds of ammunition. Used from April 1967 until the end of 1972, the turret could rotate through 220º of arc, elevate 15º and depress 45º, giving the weapon a similar ability to the US Army’s M6 system. Maintenance and ammunition feed difficulties led to the turret being withdrawn at the end of the Vietnam War.
Between March 1961 and early 1965, 1030 UH-1BS were to be built, forming the backbone of the US Army helicopter forces in Vietnam and achieving the Huey’s first overseas sales, to Australia and Norway. By the end of 1964 there were 300 UH-1S in the South East Asia theatre, having replaced such types as the Piasecki H-21 that they had previously escorted. As a result the role of the UH-1 in Vietnam became that of the primary transport for troops, equipment and supplies alongside its escort and gunship missions. To better fulfil these roles, as production continued the engine was changed to the 1100hp Lycoming T53-L-9 or 9A and later still the -11 version of the turbine, the extra 140hp these offered increasing the payload capabilities of the Huey still further. As the aircraft developed, so did the tactics governing their use. The UTTHCO took a page out of the US Marine Corps book in April 1963 with the introduction of the ‘Eagle Flights’, a technique the Marine helicopter units had begun using the previous year. The fluid nature of the guerrilla war against the Viet Cong meant the reaction time of the forces combating them had to be reduced to a minimum, or the fleeting enemy forces could disappear as quickly as they emerged from the countryside and were discovered by reconnaissance forces. To achieve this speed of response, self contained flights of helicopters were organised, consisting of a command Huey, between six and eight transports or ‘Slicks’ as they were known, five or six gunships, referred to as ‘Frogs’, ‘Guns’ or ‘Cobras’ depending on the unit and the weaponry carried, and finally a single Medevac or ‘Dustoff’ Huey was included on many missions. These Eagle Flights were essentially troops and helicopters arranged in a quick reaction force, able to respond swiftly to reconnaissance and other intelligence data regarding enemy movements. Once the Eagle Flight had engaged the enemy force, then a decision could be made about the level of reinforcement required, another flight could be despatched, or a larger response organised, depending on the size of the enemy force encountered. As the US helicopter forces in Vietnam were built up, the companies of the newly arrived Aviation Battalions each formed their
own flight, a reorganisation that gathered pace as the UH-1 replaced the CH-21 completely. One problem began to emerge from these ‘Huey only’ escorted troop transport and assault missions. The Slicks were some 20 knots faster than the armed Hueys, hence their nickname, which meant they had to reduce their cruising speed to keep the formation together. It also meant that if the formation was broken up for any reason, the Hogs often had a difficult time in regaining their escorting position. This problem was already being addressed by the US Army, Bell and several other helicopter manufacturers.
In a related sideshoot to these developments of the Huey, its success in the armed roles had highlighted the need for a faster and more manoeuvrable helicopter to perform attack and fire support missions, although this had been recognised by Bell very early in the development of the type. The company had proposed a two seat attack version based on the Huey powerplant, rotor and tail boom as early as 1958 with the D-245 Warrior, followed by a refined design known as the D-255 Iroquois Warrior in 1962. Interest from the US Army led to Bell funding a concept demonstrator, the Model 207 Sioux Scout, a much modified OH-13S with a tandem two seat cockpit, chin turret and stub wings for weapons carriage. This flew on June 27, 1963, and was sent for evaluation by the 2nd Air Assault Division at Fort Benning in Georgia. The pilots who flew the aircraft were impressed, but called for more power and a larger weapons capability. The Army launched its Advanced Aerial Fire Support System (AAFSS) programme for a dedicated attack helicopter in 1964 which was won by the Lockheed AH-56 Cheyenne, but the development problems with this helicopter were to cause its cancellation in 1972. The complexity of the AH-56 and the apparent delays almost from the outset of the project prompted Bell to further develop its D262 AAFSS entry in March 1965, the intention being to offer an interim attack helicopter to the US Army. Known as the Model 209, the prototype of this two-seat attack helicopter first flew on September 7 of that year, its speed of development being attributable to its extensive commonality with the UH-1 airframe and systems. A highly successful evaluation by the US Army that began in December, combined with the worsening situation in Vietnam, led to an order being placed for 110 production aircraft being placed in April 1966. These were designated the AH-1G and named Hueycobra, most often shortened to just Cobra, the first of these fast gunships being deployed to Vietnam in 1967. The full story of this remarkable aircraft will be the subject of a future issue of Aviation Classics. As the attack concept was progressing, Bell began investigating the civil applications of the Huey at the same time. The performance and economical operating costs of the turbine powered helicopter made good financial sense a variety of civil roles that had been previously limited by the capabilities of the earlier piston powered aircraft. As a consequence, Bell found a ready market for a civil variant, the first Bell 204B, based on the UH-1B, being delivered in 1961. The civil Huey variants, roles and customers will be covered later in this issue.
While the UH-1B was an marked improvement in performance over the A model, particularly in the later batches with the 1100hp versions of the T53 turbine, Bell considered that there was still a great deal more that could be done aerodynamically to improve the Huey still further in its rapidly developing roles. While the new AH-1 gunship was in development, a faster and more manoeuvrable Huey to fill this role in the interim was obviously a desirable goal, but there were other issues that needed addressing too. One of the problems encountered by Huey pilots in Vietnam had been the phenomena of ‘retreating blade stall’, where the rotor blade moving in the opposite direction to the line of flight would experience an aerodynamic flutter or stall as it was moving in a much slower airflow relative to the direction the blade was turning. This was particularly found in high speed flight, especially in diving attacks where the helicopter accelerated rapidly, or in tight turns or other manoeuvres that increased the loading on the aircraft. The vibration and other undesirable effects this had on the Huey caused strict limitations to be placed on the ‘velocity never exceed’ (VNE) or maximum permissible speed the early Hueys were allowed to fly at, as well as restricting their manoeuvrability. Bell had a solution already in hand for this problem in the shape of its new Model 540 rotor system which had begun development in 1960. The new rotor featured a unique pitch change bearing called a ‘Door Hinge’, all of the new hub bearings being Teflon coated which meant they did not require lubrication. The major difference was in the blades themselves, which were increased in chord from 21 to 27in (53.3 to 68.5cm) and had a larger 45lb (20.4kg) balance weight in the rotor tips. It was developed by Bell at its own expense and fitted to a civil Model 204B for testing by the US Army. In a varied flight programme the new rotor proved to have much reduced vibration characteristics at all airspeeds and at no time was retreating blade stall approached during any of the manoeuvres. The aircraft was flown to 75º and 45º of angle of bank in tight turns and abrupt pull ups were made at maximum gross weight, all with positive control and no tendency to ‘mush out’ of a manoeuvre.
Throttle chops and autorotations were also flown, the 70% increase in rotor inertia caused by the greater blade mass making this a far less critical manoeuvre over the earlier models as more energy was stored in the blades, allowing a straightforward engine out recovery to be made even at maximum gross weight. In short, the 540 rotor meant that the maximum speed restrictions on the Huey were no longer applicable, the rotor noise and vibration were much reduced, the Huey was much more manoeuvrable and very much easier to fly and finally, due to the lubrication free hub and fewer parts in the new system, easier to maintain. The improved aerodynamics of the new rotor was complemented by improvements to the airframe, partly to assist in absorbing the greater power and partly to improve the manoeuvrability still further. A new tailboom was designed, 2ft 11.5in (0.9m) longer than the original including a wider chord fin which was cambered 7º to reduce the loads on the tail rotor during manoeuvres. Added to this, new larger elevators were fitted to improve pitch stability and a new dual hydraulic control system provided redundancy in the event of battle damage. Also specific to operations in Vietnam was the redesigned engine inlet, often known as a bell mouth, which could be fitted with an improved air filter system to counter the extremely dusty conditions in theatre. The 1100 hp T53-L-9 was fitted, and as production continued the -11 model of the same power was substituted. The internal fuel capacity was increased to 242 US Gallons (916 litres) and the gross weight was increased to 9500lb (4309kg), giving the new model a load capability of 4673lb (2120kg). Finally, the pitot static head and antenna that were mounted on the nose had proved vulnerable to damage, so were relocated , the pitot head ending up on top of the cockpit. In this guise the new version was designated UH-1C, production beginning in June 1965 with the first deliveries to the US Army in September. A total of 755 C models were built, its arrival in Vietnam and its improved weapons payload capability and performance meant the gunship escorts could maintain their position in formation with the Slicks, and their increased manoeuvrability made them far more effective in bringing their weapons to bear on the fleeting targets the opposing forces presented.
With the new capabilities bestowed by the UH-1B and C came the need for a new organisation to make the maximum use of the helicopters. The development of the Eagle Flight quick reaction forces has already been discussed, but other units had been transferred to Vietnam during 1965 as the US moved out of its advisory role and began committing ground forces to the fighting. Most significant of these was the 1st Cavalry Division (Airmobile) which boasted a force of 428 helicopters on its own, mostly UH-1S. The unit had been formed by redesignating the 11th Air Assault Division (Test) on July 1, 1965, and sending it directly to Vietnam, the first of the Division’s 15,787 men arriving at An Khe in late August. The lessons learned in the UTTHCO experiments and early operational experience of the Aviation Battalions and Helicopter Transport Companies in supporting ARVN forces prior to mid-1965 had been put to good use in the development of the first US Army unit specifically trained and equipped for airmobile warfare. The first major action for the 1st Cavalry Division (Airmobile) was in the Ia Drang Valley during the Pleiku Campaign that November, countering a North Vietnamese Army (NVA) offensive in the Central Highlands. Between November 14 and 17, air assaults into Landing Zone (LZ) X-ray in the valley brought the 1st Cavalry Division troopers into contact with the 32nd and 33rd Regiments of the NVA. The fighting over the next three days and nights was unbelievably bloody and without pause, and has become the subject of a famous book, We Were Soldiers Once… And Young by the commander of the 1st Battalion of the 7th Cavalry Regiment, the first unit into LZ X-ray, Lieutenant Colonel Hal Moore, and one of the greatest journalists of the period, Joseph L Galloway. Galloway was in LZ X-ray for the entire battle and despite being a civilian, was awarded the Bronze Star for repeatedly
rescuing wounded soldiers during the battle. It is one of the most vivid accounts of modern warfare ever committed to paper and highly recommended for a full understanding of Airmobile operations. This first major battle was to set the stamp on future US helicopter operations in Vietnam, as well as the use of artillery and air power to support them. Interestingly, it also developed the NVA’S response to such operations, which was to get in so close to the US troops that the defensive use of supporting firepower was impossible. The Division’s UH-1S were used in every possible role during this battle, including the new UH-1D which will be covered in the ‘long bodies’ article in this issue. Mention must be made of two pilots in particular, Captain Ed Freeman and Major Bruce Crandall, both of A Company of the 229th Helicopter Assault Battalion, the unit that had lifted Moore’s troopers into LZ X-ray. On November 14, 1965, as the fifth load of troops was being taken into LZ X-ray, the enemy fire was so heavy that the second flight of eight UH-1S was told to abort their mission. Crandall immediately recognised that supply and medevac missions for the troops already on the ground would become critical, so he and Freeman volunteered to maintain supporting flights into X-ray with water, food and ammunition, as well as bringing wounded soldiers out. Freeman flew 14 missions that day, Crandall 22, successfully evacuating some 75 wounded troopers and keeping vital supplies reaching those engaged in the fighting. Other units, not unreasonably, had refused to land in the intensely ‘hot’ LZ, but Crandall and Freeman, in what can only be described as a display of sheer old fashioned guts, kept going back and forth. Their effect on the morale of the troopers so desperately engaged with the NVA is incalculable, as the soldiers knew supplies would be maintained and the wounded would be taken care of. Quite rightly, the sustained and repeated gallantry of both pilots was later recognised with the award of the Congressional Medal of Honour.
The increasing number of helicopter units in Vietnam, some independent such as the UTTHCO, others a part of Infantry or other US Army Divisions, gave rise to an unusual problem. In this, the infancy of airmobile helicopter warfare, training, procedures and tactics were a matter of individual unit policy and operational requirements, rather than a central doctrine. As operations became larger and more complex, these differences in practices became critical as units found it difficult to work together. Standardisation became vital, so on May 23, 1966, the 1st Aviation Brigade was formed as the command and training centre for all the independent helicopter units in theatre. Much to the US Army’s credit and clear thinking, despite this being an entirely new form of warfare, the brigade was responsible for standard procedures in training, supply, operational methods and maintenance, but combat command of the helicopters remained with the unit commander on the ground, achieving maximum interoperability, but costing none of the flexibility and speed of response of the original arrangements.
Essentially, assault transport helicopters were attached to infantry units, to which reconnaissance, gunship, cargo, medevac and other assets were allocated as the need arose. By 1968, the Brigade included 95 units operating 4230 aircraft across the entire country, most of which were UH-1S.
THE HUEY GOES TO SEA
The success of the UH-1 with the US Army and the helicopter’s obvious high performance attracted the attention of the other US services. First was the US Marine Corps in 1962, which ordered a small number of UH1Bs to evaluate the type as part of its Assault Support Helicopter (ASH) competition. The winner was to replace two dissimilar aircraft in the Marine Corps inventory, the Cessna O-1B and C Birddog light observation aircraft and Kaman OH-43D Huskie, an unusual twin intermeshing rotor observation and utility helicopter. On March 2, 1962, the Marine Corps selected the UH-1 with certain changes to its equipment and construction. All of the magnesium components were removed from the airframe and replaced by aluminium, due to the nature of the Marine operational environment, salt water having a particularly deleterious effect on magnesium. As the new aircraft would be operating from the confines of ships’ decks, a rotor brake was added to slow and park the blades quickly as a safety precaution. Since one of the roles of the earlier Huskies had been combat search and rescue (CSAR) missions, a personnel hoist was added to the cabin roof and lastly, some of the avionics and radios were changed for compatibility with existing Marine Corps systems. Based on the UH-1B airframe, the first of the new UH-1ES, Buno 151266, flew on October 7, 1963, conducting carrier trials aboard the USS Guadalcanal during December before entering service with VMO1 at MCAS New River, North Carolina, on February 21, 1964. Altogether 209 UH-1ES were built, but after the first 34 had been constructed, the Bell production line had geared up to build the UH-1C with its larger tailboom, increased fuel capacity and Model 540 main rotor. The remaining UH-1ES were therefore built to the C specification, and although a quite different aircraft it retained the original designation. Marine Corps deployments to the Vietnam theatre saw its Hueys used in the troop transport, gunship and CSAR roles with VMO2 and VMO-6 from May and August 1965 respectively, followed by VMO-3 in December 1967. Before this in September 1964, two weapons systems had been developed for the UH-1E, the TK-2 and TAT-101, both of which are described in the adjoining table. Also during the conflict, many UH-1ES were upgraded with the introduction of the 1400hp version of the Lycoming turbine engine, the T53-L-13, giving them greater payload capabilities and improving their hot and high performance considerably. These helicopters were to be a reliable and popular addition to USMC inventory, 128 surviving the Vietnam War, many remaining in service until the mid 1980s. One other version of the UH-1E was designated; a pilot trainer known as the TH-1E, for which 20 Bunos, 154730 to 154749, were allocated, but it is unclear if these were ever built as no constructor numbers are available. One UH-1E, 154778, was converted into a ground instructional airframe designated GUH-1E in 1986 and given the USAF serial of 84-0474, after which it was used at Chanute Air Force Base in Illinois before being transferred to the Dominican Republic Air Force.
USAF AND NAVY HUEYS
The US Air Force interest in the Huey began with a requirement for a helicopter to support the many Intercontinental Ballistic Missile bases all across the United States. This would have to be able to carry 4000lb (1815 kg) of cargo or a missile site crew of up to 10 personnel. One further stipulation was the use of the 1250hp General Electric T58-GE-3 turboshaft to provide a parts and maintenance commonality with the Sikorsky HH-3 Jolly Green Giant fleet then in service. Bell modified the short cabin UH-1B to take the new engine and added the longer 48ft (14.63m) span Model 540 rotor from the UH-1D. This was to absorb the additional power and provide the necessary performance to produce an aircraft initially designated the XH-48A. The longer rotor also meant the longer tailboom of the D also had to be fitted; resulting in a short but powerful version of the Huey, later redesignated the UH-1F. In 1963, the upgraded design was selected as the competition winner, the first of the 120 UH1Fs built flying on February 20, 1964, before entering service with the 4486th Test Squadron at Eglin Air Force Base on September 23 later that year.
An additional 26 airframes were built in 1967 to act as pilot and crew hoist trainers under the designation TH-1F, serving with a number of USAF flying schools. During the Vietnam War a first batch of 20 UH-1FS were modified to take the M93 and M94 weapons systems as described in the separate table. These were used in the gunship role, often alongside the unarmed UH-1F transports and were known as UH-1PS. The first of these gunships were supplied to the 1st Special Operations Squadron (SOS) at Hurlburt Field in Florida for trials, the batch sent to Vietnam being operated by the 20th SOS, known as ‘The Green Hornets’. The UH-1FS were to remain in service until replaced by the twin engined UH-1NS during the 1980s. The US Navy began using the UH-1 in 1965 with the formation of Task Force 116 in Vietnam. This force was established to keep the Mekong Delta free of enemy vessels and transport and was made up of Patrol Boats (PBRS) and SEAL special forces teams. Helicopters to support these forces were initially acquired from the US Army, which loaned eight UH-1BS from the 197th Aviation Company to form four two ship flights across the region, the flights becoming known as the Seawolves, the first to begin operations being Det 29 in October 1966. The flights were officially formed into Helicopter Attack (Light) -3 Squadron (HA(L)-3) in the spring of 1967, three more flights being formed to cover the delta more effectively with 33 UH-1BS being on strength by 1969. The navy recognised two specific requirements for the UH-1 during this period which resulted in two more models being developed. The first was on May 16, 1968, with Bell being awarded a contract to supply 45 TH-1L crew trainer helicopters based on the UH-1E but with the 1400hp T53-L-13 engine and improved avionics. The first were delivered in November 1969 and eventually 90 of this version were built, alongside eight of a utility transport variant known as the UH-1L, ordered at the same time as the trainers. Four of the L variant were sent to the HA(L)-3 detachment at Binh Thuy and took part in Operation Sealords, which stood for Southeast Asia Lake, Ocean, River and Delta Strategy, the systematic cutting of North
Vietnamese supply lines from Cambodia via the rivers and Mekong Delta between 1968 and 1971. Here they were armoured and armed with a similar system to the US Marine’s TK-2 weapons and pylons, capable of carrying machine guns, rockets and 500lb (230 kg) bombs, both conventional and fuel-air explosive types. These two models were used as the basis for 27 HH-1KS, an air sea rescue helicopter with additional mission equipment. The first was delivered in May 1970, three being sent to serve a CSAR aircraft with HA(L)-3 in November that year.
THE LAST SHORT
The advent of the 1400hp version of the T53 engine gave rise to the several of the upgraded versions of the short bodied Huey as already discussed, the last of these being the US Army’s UH-1M. These were all conversions from UH-1CS with the larger engine to allow better performance when fully loaded with weapons in the gunship role. As the T53-L-13 was also fitted to the transport long body UH-1H Hueys, it made sense from a spares and maintenance point of view to have a commonality of engines between the types. A number of additional sensor systems were fitted to UH-1MS due to their increased lifting power, including the Hughes Iroquois Night Fighter and Night Tracker (INFANT) low light TV, image intensifier and Infra Red searchlight system to assist in aiming the M21 weapons system with its miniguns and rocket launchers. Five more UH-1MS were fitted with the AN/AAQ-5 Forward Looking Infra Red (FLIR) turret in a similar position to the earlier M5 40mm grenade launcher, again used in conjunction with the M21 weapons system. At the same time as all these developments of the short bodied design had been going on, the cabin had been stretched to produce high capacity transport version of the helicopter. These have already been mentioned in this narrative as the stories of the long and short bodied Hueys intertwine. Known as the Bell Model 205 by the company, these variants will be described in full on page 56 of this issue. Words: Tim Callaway
The classic image of the Huey in Vietnam and the lifeline it represented to the deployed troops in the field. Here, during Operation Macarthur in December 1967, a UH-1B flies a resupply mission for B Company, 1st Battalion of the 8th Infantry some 20 miles southwest of Dak To.
One of the lesser known roles for the UH-1B in Vietnam was conducting ‘psyops’, psychological warfare against enemy forces using powerful broadcast speakers.
The increased power of the UH-1B is evident in this photograph of one recovering another while on exercise in the southern US.
Later door gun mounts were developed to carry the M60, or as seen here mounted on US Navy UH-1S, the Browning .50 Cal or M134 minigun.the Sagami mount was widely adopted as were a number of other pintle systems for door gunners.
The M6, the famous ‘Quad’ or ‘Flex’ gun system used the new M156 mounts with four M60C 7.62mm machine guns fed by electric drive motors from ammunition boxes under the rear bench seat in the cabin.the guns are shown here in their depressed position.
A close up of the XM26 system on a UH-1B showing the front end of the missile pod and the nose mounted sensor and aiming turret.
The M17 system used the Kellett two pylon mount to fit four M159 rocket pods carrying 19 2.75in rockets each, a system fitted here to a UTTHCO UH-1B, but not widely adopted due to its weight.
The M22 system fitted six AGM-22A wire guided anti-tank missiles, a licence built version of the Nord S-11, aimed via an XM-70 sight.
The co-pilot’s cockpit of a UH-1B fitted with the XM26 system showing the sensor turret binocular sight and missile steering controller.
The M16 added two M157 or M158 rocket pods to the M6, each containing seven tubes for 2.75in rockets which were aimed via an M60 reflex sight mounted in the cockpit. Here the M60s are shown in the fully raised position.
A close up view of the AGM-22A missiles of the M22 system on their mount. Warrant Officer Robert Maxwell adapted the M3 weapons system by removing one or two banks of six rockets from the 24 tube packs then adding a launch rail for a single AGM-22B. A rare colour shot of one of the UH-1BS fitted with the XM26 system with two pods of three Hughes BGM-71 TOW anti-tank missiles with the nose mounted sensor and aiming turret.
Two views of the M21 system with a pair of M134 six barrelled machine guns known as Miniguns mounted on the ends of the M156 mounts which could also carry a seven tube or a 19 tube rocket launcher.
Two US Marine Corps UH-1ES fitted with the Temporary Kit 2 (TK2) weapons system with two M60C 7.62mm machine guns and seven tube rocket launchers. Note both aircraft also have the Emerson Tactical Armament Turret 101 with two M60 machine guns.
When the M16 or M21 machine gun system on the M156 mounts was fitted along with the M5 grenade launcher in the nose turret, the combination was referred to as the M50 as seen here.
One of the two XM26 equipped UH-1BS seen during the early trials before a period in storage after which the aircraft were camouflaged and sent to Vietnam.
A close up of the Temporary Kit 2 (TK2) weapons system with two M60C 7.62mm machine guns and a seven tube rocket launcher on a USMC UH-1E.
The sling holding this M60 is typical of the early bungee cord door gun mounts.
Loaded for bear. A UH-1B fitted with the M3 rocket packs containing 48 2.75in Mk.40 FFARS and the M5 nose mounted 40mm grenade launcher turret.
A UH-1B fitted with the M3 Aerial Rocket Artillery or ARA system, with the second 24 rocket pack in the cabin.
A UH-1B showing the ‘bell mouth’ air intake to the engine, nose mounted antenna and pitot head and the base of the M156 common weapon mounts just aft of the cabin doors.
The UH-1B was also used to conduct long range and ferry experiments with external tanks.
The increased lifting power of the UH-1B allowed combinations of armament such as t he M50 to be carried, here consisting of the M5 nose mounted 40mm grenade launcher turret and a pair of M156 mounts with the quad M60 flex guns and two seven tube rocket pods.
A grainy but interesting shot of the USS Garret County, a Second World War Landing Ship Tank (LST) converted for use as a helicopter platform and patrol craft tender. Moored in the Mekong Delta, the ship has a UH-1B furthest from the camera, with either a UH-1C or M with its broader fin closer to the camera.
The Bell D-255 Iroquois Warrior mock up presented to the US Army for the Advanced Aerial Fire Support System (AAFSS) programme.
The US Army’s build up and reorganisation of helicopter forces in Vietnam included the 1st Cavalry Division (Airmobile) which boasted a force of 428 helicopters on its own, arriving in theatre in August 1965. The sheer air power these forces could deploy was an impressive introduction of a whole new form of warfare.
The UH-1C featured a broader chord fin cambered 7º to port to help unload the tail rotor at high speeds.
Bell funded an AAFSS concept demonstrator, the Model 207 Sioux Scout, a much modified OH-13S with a tandem two-seat cockpit, chin turret and stub wings for weapons carriage.
The developments led to a further Bell funded project, the Model 209.This is the second prototype of the Bell AH-1 Cobra helicopter gunship, seen with the early retractable undercarriage. Its roots in the UH-1 design are unmistakeable.
Bruce Crandall was to win the Congressional Medal of Honour for his sustained bravery during the first major 1st Cavalry Division (Airmobile) engagement, the battle of the Ia Drang Valley in November 1965. Here he is seen leading a formation of UH-1 helicopters from Alpha Company of the 229th Aviation Regiment just prior to takeoff in Vietnam later in 1966.
The UH-1C solved many of the aerodynamic problems of the earlier Hueys through the addition of the Model 540 rotor with its broader 27in chord blades, simplified hub and pitch control mechanism.
This serpent is painted on the door of Bruce Crandall’s UH-1D helicopter, a Huey variant covered in detail later in this issue. Such images enabled fellow pilots and ground commanders to identify pilots by their distinctive call signs and door markings. Crandall’s callsign was Ancient Serpent Six.
The US Marine Corps was the first service after the US Army to develop its own versions of the Huey. Here Marine UH-1ES touch down with their loads at Fire Support Base Cunningham in 1969.
US Marine Corps UH-1ES were also fitted with a personnel hoist on the cabin roof, seen here in the stowed position with hoist arm retracted and hook in its recess above the cabin door.
Major Bruce Crandall’s UH-1D lifts off after discharging infantrymen on a search and destroy mission.
A US Marine Corps UH-1E fitted with the TK-2 weapons mounts with four M60 machine guns and a 500lb Fuel Air Explosive bomb.the door gunner also has an M60 machine gun.
The USAF UH-1FS all featured the 1250hp General Electric T58-GE-3 turboshaft engine with a starboard facing exhaust.this is a Bell TH-1F pilot trainer version seen in 1975 when serving with the Instrument Flight Centre at Randolph Air Force Base.
A number of the USAF UH-1FS were converted with weapons mounts as the UH-1P, including pintle machine gun door mounts as seen here.this is a preserved example in the National Museum of the United States Air Force at Wright Patterson Air Force Base in Ohio.
A Bell TH-1L Iroquois crew trainer of Helicopter Training Squadron 8 (HT-8) pictured in flight over Northwest Florida.
A UH-1P ready for a covert mission, note the flexible ladder that could be extended to pick up personnel when the helicopter could not land.
Before the development of the UH-1L for the US Navy, a number of UH-1BS, Cs and Ms were transferred from the US Army to HA(L)-3 to escort PBRS operating in the Mekong Delta, as seen here in 1968.
Above: On display at the National Museum of Naval Aviation at Pensacola Florida is this Bell HH-1K, the US Navy’s search and rescue version of the Huey.this aircraft is displayed in the markings of HA(L)-3, but actually saw service in Vietnam with HA(L)-5.
Two views of a UH-1M fitted with the M21 weapons system and the Hughes Iroquois Night Fighter and Night Tracker (INFANT) low light TV, Infra Red and searchlight system to assist in aiming the weapons at night.
Left: One USAF covert mission, known as Pony Express, supported secret missions and radar sites in Laos.this is a UH-1P of the 20th SOS at Duc Lap, South Vietnam, loaded with lumber and plywood sheets.