The UH-1D and H
As already explained, the original Hueys had been a tremendous success in every role the aircraft was asked to fill, the turbine powered helicopter being a quantum leap in capability over earlier types. The higher powered B and C models fitted with the broader chord rotors had the lifting capability to manage heavy weapon loads in the gunship role while dedicated attack helicopters were being developed. Indeed, the only criticism levelled at the Huey was regarding its limited internal cabin space in the troop transport role, especially when carrying door gunners for defence and covering fire of the troops they were delivering to landing zones.
ENTER THE DELTA
In July 1960, the US Army ordered seven service test examples of a stretched version of the helicopter known as the YHU-1D, later to become the YUH-1D after the US Forces designation standardisation of 1962. Referred to by Bell as the Model 205, the most obvious change was the longer cabin, stretched by 3ft 5in (1.05m) to increase the capacity to 220cu ft (6.23cu m).
The limited internal cabin space of the early UH-1S caused Bell and the US Army to discuss a larger version of the helicopter that could carr y more troops in 1960. This was to lead to the two most produced variants of the Huey which would be exported worldwide.
This allowed an extra four seats to be fitted, facing outboard on either side of the transmission housing that now extended into the centre of the cabin, bringing the total number of seats to 15. This typically allowed a crew of four, two pilots, a crew chief and a gunner, to be carried along with an infantry section of 10 troops and their equipment. The cabin stretch was greatly facilitated by the original construction of the Huey, the two main beams under the cabin floor being extended forward and the sides of the centre section being moved aft to leave the transmission housing box in the middle of the cabin instead of forming the rear wall as had previously been the case. Externally, the most obvious differences, aside from the longer transmission and engine housing with its revised cooling louvres, were the stretched main cabin sliding doors which now featured two windows instead of the original one, forward of which was a short hinged door with its own window. Both of these doors could be quickly removed in the field and the Huey flown without them, greatly speeding entry and exit from the cabin in the troop or cargo transport roles. The longer cabin also allowed a total of six stretchers to be carried along with medical attendants in the medevac role, or up to 4000lb (1814kg) of cargo internally. The first YUH-1D built, 60-6028, constructor’s number 701, made its maiden flight on August 16, 1961, the test aircraft being fitted with the 44ft (13.41m) span rotor and the T53-L-9 version of the turboshaft engine. However, flight tests quickly proved the rotor and engine combination were insufficient to enable the helicopter to achieve its full load potential. Bell addressed the deficiencies the test flights revealed by changing the main rotor for one with blades of 21in (53.34cm) chord and 48ft (14.63m) span, which also required a redesign of the tail boom, lengthening it to accommodate the new longer rotor. This was driven by the 1100hp T53-L-11 version of the turboshaft and solved the performance shortfalls, the new rotor and engine increasing the maximum operating weight of the Delta model Huey to 9500lb (4309kg). US Army trials began at Edwards Air Force Base in California in March 1962 with the second YUH-1D, 60-6029, breaking
three world records for differing aspects of performance in April that year. These included two time-to-height climb records and a speed record over a closed circuit of 134.96mph (217.197kph). These successes led to the first of several large production orders being issued, with the first production UH-1D, 62-2106, being delivered to the US Army’s Aviation Test Board on May 31, 1963. Between September and December 1964, the UH-1D was to capture no fewer than 17 world performance records for helicopters, including a speed record of 180.17mph (289.95kph) over a two mile (3.2km) course and an altitude record of 35,147ft (10,712.8 m). The first operational unit to receive the UH1D was the 11th Air Assault Division (Test) at Fort Benning in Georgia on August 9, 1963, which, as already related, was sent to Vietnam in July 1965 and redesignated as the 1st Cavalry Division (Airmobile). These two helicopters were to be the first of 2008 UH1Ds built for the US Army between 1962 and 1966, by far the majority of the total production run of 2561 of this version of the Huey, which includes 352 built under licence in Germany which will be covered later in this issue.
As already mentioned, the UH-1D was to excel in the troop transport and medevac roles in the South East Asia theatre, becoming immortalised as a symbol of that conflict in television news programmes at the time and in movies and documentaries since the war’s end. However, there were a number of other remarkably specialist roles for the UH-1D, some of which are little known. One of these was the use of the UH-1D in the night interdictor and counter insurgency roles, a necessary and growing role as the North Vietnamese Army and Viet Cong shifted more of their attacks, as well as their transport and resupply activities, to the hours of darkness to avoid the overwhelming US air power now deployed in country. The development of the night attack Hueys had begun with UH-1BS and Cs in 1964, the Army gunships initially working with US Air Force illuminator platforms known as flareships, often cargo aircraft such as C-47s or C-119s. However, flareships were not always available, so the Hueys were modified to carry their own flares and other
illumination and sensor systems to detect and track enemy movements at night. These initially consisted of mounts for the same Mk.24 parachute flares dropped by the flareships, which produced two million candlepower and burned for about three minutes. These mounts, built and fitted in the field by individual units, attached differing racks with six flares on the M156 universal weapons mounts or loaded them in containers in the cabin doorways of the Huey where they could be dropped manually. Eventually, the official XM19 system was introduced, which stored 24 Mk.45 parachute flares in the cabin and ejected them sideways through the doors. The Huey flareships began working in teams with accompanying gunships, but the flare system proved limited so alternative illumination systems were developed. One of the first was again locally produced, using seven spare landing lights from USAF transport aircraft arranged in a cluster on a manually steerable mount in the cabin door of a Huey, creating a flexible and powerful searchlight and area illumination device. These locally produced light clusters were eventually replaced by purpose built searchlights and other illumination devices. The advent of the UH-1D with its larger cabin allowed these lights to be mounted next to a door gun, such as a Browning .50 cal or M60 machine gun, the gunner engaging illuminated targets directly. Using this system, the lightships flew in cooperation with a command aircraft or helicopter which flew at high level and directed the illuminator on to targets. Once illuminated, the target would be engaged by the door gunner in the lightship, distracting the enemy from the approach of the gunships flying at low level which would then engage the illuminated area with their heavy weapons. These missions were known as Firefly or Lightning Bug operations, the command platform usually being a low light TV or infrared sensor equipped helicopter or other aircraft type to provide initial target information and direction. While the Firefly/lightning Bug system was an improvement over the flareships alone, the night and low light sensor technology was developing to allow the lightship Hueys to detect their own targets, speeding the process from detection to attack. A number of UH-1DS were equipped with the powerful AN/VSS-3 Xenon 50 million candlepower searchlight from the M551 Sheridan light tank pintle mounted in the cabin door and steered by a crew member. This searchlight could operate in both white light and infrared modes, in a focussed or defocused beam. Alongside this was a new development, the AN/TVS-4 Night Observation Device (NOD), a medium range light intensification device resembling a large zoom lens mounted on a tripod. The NOD had an 8in (20.32cm) aperture and a 40mm three stage first generation light intensifier tube with 6x magnification which gave it a range of 6560ft (2000m) in moonlight and 4000ft (1200m) in starlight. The range of the NOD was increased when used in conjunction with the Xenon searchlight in infrared mode as it increased the radiation levels the NOD had available to intensify. Alongside the NOD and Xenon was an M134 Minigun on a pintle mounting with a pair or single M60 on a similar mount on the opposite side of the cabin.
In this guise the UH-1DS became known as Nighthawks, operated by two pilots, a NOD and Xenon operator and two or three gunners to man the weapons. Nighthawk missions usually saw a single lightship flying at low level, steered into known target areas by ground radar operators. Accompanying it were two gunships, flying at a distance to evade detection by the enemy forces. Once the target was detected by the NOD and Xenon operator, either the Xenon was switched to white light mode to illuminate it, or the lightship’s minigun was used with tracer to pinpoint the position on the ground for the gunships to attack. Occasionally, a flareship also accompanied the Nighthawk team to provide area illumination from altitude. As mentioned in the short bodied article, the Nighthawks were supplemented by the INFANT and FLIR equipped UH-1MS in the latter stages of the Vietnam conflict. Like other models of the Huey, the UH-1D was also to be used for special forces and psyops missions, as well as a version fitted with an aerial spray bar and cabin mounted drum to act as defoliant delivery aircraft, spraying Agent Orange and other chemicals to reduce the cover available to the North Vietnamese forces. Only one other variant of the UH-1D was produced, the HH-1D, specially equipped as a rescue and fire fighting helicopter for use at US Army and USAF bases. The cabin contained a 50 gallon (190 litre) tank that could deliver either water or foam via a spray system which included a 16ft (4.9m) retractable boom to allow the helicopter to remain clear of the hot air above a fire. This would later be produced as a more powerful variant based on the next model of the Huey.
MASS PRODUCED HOTEL
Even given the more powerful rotor of the UH-1D, there were still limitations on performance imposed by the hot and high altitude conditions found in South East Asia. Hovering, particularly out of ground effect at high loaded weights was simply not an option on many days, and it became obvious that more power was required. This came in the form of the new 1400hp T53-L-13 version of the Lycoming turboshaft, which was added to the UH-1D airframe to produce the Huey variant produced in greater numbers than any other, the UH-1H. Aside from the new engine, there were few changes between the UH-1D and H, the most obvious being the moving of the pitot head from the nose to the cabin roof. As with the short bodied variants, this was to avoid damage while the aircraft was on the ground, the nose mounted probe being prone to this. The production H also had a fully instrument flight equipped cockpit to allow operations at night and in bad weather. The first H was in fact modified from D, designated the YUH-1H and making its first flight in July 1966. The first production UH1H, 67-17145, was delivered the following year and still exists today, as a gate guardian at the Veterans of Foreign Wars Post 5202 at Waynesville in North Carolina. The first unit to be deployed to Vietnam equipped with the UH-1H was the 45th Medical Company who arrived at Long Binh in July 1967, the new type quickly replacing the UH-1D in the medevac role due to its greater performance. Like other Huey models, the UH-1H was to be produced under licence, in this case in Italy, Japan and Taiwan, with an astounding 5435 of this model being produced by Bell, Agusta, Fuji and AIDC. Bell’s production of 4845 UH-1HS ended in December 1980, only to be restarted to fulfil an order for 55 helicopters from Turkey, the last one of which was delivered in 1987. With the end of the Vietnam War, mixed fleets of UH-1DS and Hs formed the backbone of the US Army’s transport and airborne assault units, as well as equipping the majority of the National Guard units in these roles. The H model Huey was also used in training roles at Fort Rucker and to equip the multinational observer unit in Sinai that monitored the military presence in the area. The introduction of the Sikorsky UH-60 Black Hawk in 1979 saw the steady replacement of the UH-1 in US Army service from then onwards, with the last being retired from front line units in the US in 2005, the last leaving the US Army’s Joint Multinational Readiness Centre in Germany in April 2011.
The National Guard units began to retire their UH-1HS in 2009 as they were replaced by the Eurocopter UH-72 Lakota. However, UH-1HS were to go into battle again in 1991 during Operation Desert Storm, being used by the 101 Airborne Division, the 1st and 24th Infantry Divisions, the 1st, 2nd and 3rd Armoured Divisions and the 1st Cavalry Division in that conflict. The type also equipped 3 Squadron of the Sultan of Oman’s Air Force and 12 Squadron of the Royal Saudi Air Force during operations to end the occupation of Kuwait by Iraq. By 2014, 55 UH-1HS were still listed as active with the US Army, mostly in training, test and reserve roles.
While the majority of the UH-1HS produced were used as troop and utility transports with all of the US forces, like the earlier short bodied Hueys, the power and flexibility of the UH-1H led to a number of specialist sub types being produced. The HH-1H was based on the fire fighting and rescue HH-1D variant, with 30 of these being delivered to the US Air Force between 1970 and 1973. These equipped the 37th and 304th Aerospace Rescue and Recovery Squadrons as well as the 6512th Test Squadron and were fitted with an electric rescue hoist above the cabin door, similar to that fitted to the US Marine Corps UH-1ES. The tail rotor was also moved to the starboard side of the fin. The US Air Force also acquired the UH-1H in the early 1970s for use by its Special Operations units, the last one of these being retired and transferred from the 1st Special Operations Wing at Hurlburt Field in Florida to the New York State Police in June 2013. In 1976, the US Army began to modify UH1Hs under Project Quick Fix IA and IB to
develop an electronic warfare version of the Huey to locate and jam enemy radio communications among other tasks. Aside from the AN/ARQ-33 radio interception, location and jamming equipment, a suite of defensive aids was fitted to these aircraft, including chaff and flare dispensers, an infrared jammer and a radar warning receiver. A total of 22 helicopters were modified to become EH-1HS, first issued to the 82nd Airborne and 2nd Armoured Divisions. The 82nd were to deploy their EH-1HS in combat during the invasion of Grenada in 1983. The lessons learned from the EH-1HS led to a more advanced AN/ALQ-151 locating and jamming suite being fitted to at least 10 more UH-1HS, which were designated as EH-1XS under Project Quick Fix IIA. Another system that was tested on a UH1H airframe in 1977 was the Multi Target Electronic Warfare System (MULTEWS),
aimed at providing counter mortar and counter battery radar jamming. This was known as the EH-1U, but the weight and vibration of the large externally mounted elements of this complex electronic warfare suite severely reduced the performance of the helicopter, which crashed during testing at Edwards Air Force Base. Two of the odder versions of the UH-1H went under the same designation, JUH-1H. The first of these were five UH-1HS modified as part of the Stand Off Target Acquisition System (SOTAS) programme. These were fitted with longer undercarriage legs which could be retracted sideways to clear the AN/APS 94 Sideways Looking Radar (SLAR) mounted in a canoe shaped pod under the Huey’s cabin. The radar head was mounted where the cargo hook had previously been and could rotate in flight, the variant being equipped with improved navigation systems and a datalink to download the radar images to a ground station. Known as JUH-1H (SOTAS) helicopters, they were deployed to Germany and Korea in 1975 as part of an evaluation of the system, but were not replaced until 1986 with the introduction of the EH-60 Black Hawk variant. The second version known by the JUH-1H designation is a small number of UH-1HS modified in the late 1980s and early 1990s with a false gunner’s cockpit in the centre of the nose to simulate the Mil Mi-24 Hind attack helicopter at the National Training Centre and other US Army training units. The helicopters were all painted with Soviet style camouflage and markings and essentially filled the aggressor role by simulating the air threat these helicopters represent to ground and other helicopter forces. Aside from these two sub types, there were a number of other JUH-1HS used for trials and testing of a wide variety of modifications and equipment.
MODIFICATIONS AND UPGRADES
The longevity and reliability of the UH-1H convinced the US Army to begin looking at a mid life upgrade programme for the helicopter in the early 1980s. This was to upgrade the avionics with new radios, navigation aids and a radar altimeter as well as adding new defensive systems such as
an infrared jammer, modified exhaust and a chaff and flare dispenser. The fuel system was upgraded as were the main and tail rotor control systems and an improved stabiliser bar was added to the main rotor hub. In November 1981, the US Army issued a request for proposals to provide composite main rotor blades for the UH-1H, Bell and Boeing responding with a joint programme to develop the blades. Test flying began in 1985 and proved the new blades improved the hover performance and reduced the fuel consumption in forward flight, so they were ordered into production with deliveries beginning in January 1988. Aside from the UH-1H utility helicopter fleet, the navigation upgrades, which included the radar altimeter, distance measuring equipment and an instrument landing system, were all added to the 220 UH-1H airframes during this period along with a cabin roof mounted rescue hoist. The modifications were carried out by the US Army Electronics Command in order to produce an upgraded medevac and rescue variant of the Huey which was known as the UH-1V. These equipped both Army and National Guard units until the mid 1990s when they began to be replaced by the UH-60A and later the UH-60Q variants of the Black Hawk, the last three UH-1VS retiring on August 8, 2012. The most recent modified variant of the UH-1H is the thoroughly upgraded TH-1H pilot training version for the US Air Force. This has all the features of the Huey II upgrade kit offered by Bell, including a new all glass digital cockpit, completely rewired airframe, an upgraded 1800hp T53-L-703 engine, transmission and rotor and the more streamlined nose shape of the Bell 212. The TH-1H is intended to allow trainee pilots to easily transition to such advanced rotary winged aircraft as the Bell CV-22 Osprey. The first TH-1H was rolled out in November 2005, and an initial contract for nine helicopters was issued on January 25, 2006. Testing the aircraft and developing the training programme had the system ready for the first class of trainees in the summer of 2007 and by 2014 40 TH-1HS were in service.
One of the seven YUH-1DS ordered in 1960, still fitted with the short tail boom and 44ft span rotor.
UH-1D Iroquois helicopters airlift members of the 2nd Battalion, 14th Infantry Regiment from the Filhol Rubber Plantation during Operation Wahiawa, a search and destroy mission conducted by the 25th Infantry Division, northeast of Cu Chi,vietnam.
The UH-1D quickly became the standard troop transport for the US Army in Vietnam. Here a platoon from Troop B, 1st Reconnaissance Squadron, 9th Cavalry Regiment, 1st Cavalry Division (Airmobile) unload from a UH-1D helicopter hovering above the ridge line.
The production UH-1D featured a 48ft span rotor and therefore needed a longer tail boom to accommodate it.
The UH-1D also began equipping medevac units from its introduction into the Vietnam theatre. The vertical stanchions and hook mounts for three stretchers can be seen in the cabin.
The UH-1D and H night illuminators, known as flareships, initially used a variety of systems to deploy the Mk.45 flares, such as ejector racks mounted on the side, or simple bins where the flares could be dropped manually.
The temporary flare systems were replaced by the XM19 which stored 24 Mk.45 flares and deployed them through the cabin door.
The flareships began to be supplemented by the Firefly or Lightning Bug illuminators, initially equipped with seven landing lights on a manually steerable mount in the cabin door.
If the Nighthawk Huey did not wish to reveal its location to enemy forces by using the Xenon searchlight in white light mode, it could mark targets for the gunships with just the tracers from the M134 minigun. In the South East Asia theatre a number of UH-1DS and Hs were fitted with drum and pump or ram air systems in the cabin with spray bars extending from the sides to deliver a range of chemical defoliants and insecticides.
Two views of the AN/VSS-3 Xenon searchlight and the AN/TVS-4 Night Observation Device (NOD) mounted next to an M134 minigun on a Nighthawk UH-1H. Note the flash suppressor muzzles on the miniguns.
The UH-1H was the powerful medevac and troop transport helicopter the US Army needed, quickly filling both roles.this UH1H is fitted with an infrared jammer under the tail boom, air intake blanking plates and an exhaust that distributed the heat of the exhaust into the rotor, all of which were measures aimed at helping to defeat heat seeking missiles. Note the HF radio antenna zig-zagging down the tail boom.
Aside from being reliable, the UH-1H was also long lived in front line US Army service. Here, a UH-1H of Battery B, 1st Battalion, 159th Aviation Regiment, 18th Aviation Brigade, flies over an abandoned town in SaudiArabia during Operation Desert Shield on December 9, 1990.
Thirty HH-1HS, a fire fighting and rescue variant, were delivered to the US Air Force between 1970 and 1973. Note the tail rotor is on the starboard side of the fin.
The AN/ALQ-144 infrared jammer was fitted both above and below the UH-1H during its career, this one seen at Fort Rucker during cold weather trials in 1978.This UH-1H is also fitted with the air intake blanking plates and angled exhaust to help reduce the helicopters heat signature to a minimum. The JUH-1H(SOTAS) on the ground showing the longer undercarriage and the SLAR in the stowed position. The JUH-1H(SOTAS) version of the Huey in flight with the undercarriage legs in the retracted position and the AN/APS 94 Sideways Looking Radar (SLAR) rotated sideways.
A total of 220 UH-1H airframes were given a mid-life upgrade with improved avionics to become the UH-1V medevac and rescue version of the Huey. The latest upgrade to the long bodied single engined Huey is the TH-1H, an advanced pilot trainer for the US Air Force with the T53-L-703 engine and an all glass cockpit.
Another type known as the JUH-1H was fitted with a false gunner’s cockpit in the centre of the nose to simulate the Mil Mi-24 Hind attack helicopter for US Army training units.
The sole UH-1H fitted with the Multi Target Electronic Warfare System (MULTEWS), aimed at providing counter mortar and counter battery radar jamming. Known as the EH-1U, this helicopter crashed during testing at Edwards Air Force Base.