The carriage of substantial payloads suggests helicopters with gross weights of at least four tonnes; hence this present discussion excludes light utility helicopters such as the AgustaWestland A109 series and the Eurocopter AS555 Fennec and EC635. The classic utility helicopter is the Bell UH-1 'Huey', the first of which flew in 1956. Over 16,000 examples were built and approximately 5000 are still in use today in more than 40 countries. Some Hueys have achieved an incredible 30,000 flight hours. The original UH-1A had a gross weight of only 2.63 tonnes, but over time the Huey has progressed (by means of increased power and improved rotors) into the medium-sized utility category.

Most significantly, the US Marine Corps is to acquire 100 Bell UH-1Ys, with a pair of 1363 kW (contingency rating) General Electric T700-GE-401C engines, four-blade rotors, new transmissions, a semi-automatic blade-fold facility on the main rotor, a crashworthy fuel system and a 'glass' cockpit. Compared to the Corps’ standard UH-1N with a 1342 kW Pratt & Whitney Canada PT6T-3 Twin Pac (US military designation T400), the UH-1Y has twice the power and twice as many rotor blades to absorb it. Gross weight is increased from the 4.763 to 8.39 tonnes, and maximum cruise speed is up from 204 to 293 km/hr. The UH-1Y also provides 85 per cent commonality with the upgraded AH-1Z attack helicopter.

	The AgustaWestland future Lynx was selected by the British Ministry of Defence to fill its Army and Navy needs and beats its competitor, the NH90, in the process. (AgustaWestland)

The original plan was for all 100 UH-1Ys to be produced by converting UH-1Ns, but it has been decided that the small financial saving (relative to new-build) is outweighed by the fact that aircraft chosen for conversion will be out of action for two years, thus substantially reducing the number available in the front line. In consequence, only twelve UH-1Ns will be converted and the remaining 88 will be new-build. Reopening the Huey line, which was closed in 1976, will clearly make it easier for Bell to market the UH-1Y to overseas customers.

Two UH-1Y test vehicles are currently being flown and in June 2005 they are scheduled to go for operational evaluation at Camp Pendleton Marine Corps Air Facility in California. The first low-rate initial production remanufactured UH-1Y is due to fly in the first quarter of 2006, and the first delivery is scheduled for May 2006. Initial operational capability is planned for March 2008. In the meantime, Bell was awarded a $ 104 million modification contract for a second low-rate production batch.

The US Army has even larger numbers of Hueys (around 380 UH-1Hs in service and 250 in storage), of which 114 have been allocated to Foreign Military Sales (FMS) programmes, 40 are being handed over to the US Air Force for aircrew training, and 380 are currently being retained in case they are needed for the Army's new Light Utility Helicopter (LUH) programme, a decision on which is due in August 2005.

	Although marketed primarily as an executive transport (as exhibited at Farnborough), the good-looking Bell/Agusta Aerospace AB139 is also available in military form as a Huey replacement. (Armada/RB)

Some UH-1H operators will prefer a relatively low-cost upgrade, rather than the massive advance provided by the UH-1Y. Bell's ’Huey II‘ has a 1342 kW Honeywell T53-L-703 engine, giving a maximum take-off weight of 4.76 tonnes, or up to 5.08 tonnes with external load. The performance improvement is especially marked under hot and high conditions, and the Huey II has proved particularly useful in patrolling the border between Pakistan and Afghanistan and in counter-drug operations in the mountains of Colombia. The tail-boom and dynamic systems are those of the Bell 212, more than doubling the TBO (time-between-overhauls). The company estimates a 42 per cent reduction in direct operating costs. More than 100 Huey II upgrades have so far been carried out, primarily for law-enforcement agencies, although the US Air Force ordered 24 upgrades in February 2005. The refurbished Hueys (to be delivered over a period of four years) will be used for pilot training.

The Huey 703 represents a more limited upgrading of the UH-1H by Global Helicopter Technology and Airwork, under which the 1044 kW T53-L-13B engine is modified to provide -703 performance, giving around 30 per cent more power under hot/high conditions. The helicopter is fitted with a tractor tail rotor and modifications to improve directional handling.

	Sikorsky's H-60 series is illustrated here by a US Air Force HH-60G Pave Hawk of the 301 st Rescue Squadron, operating from a forward deployed location in southern Iraq. (US Air Force)

The Bell 210 medium utility helicopter, which first flew in the form of a remanufactured UH-1H on December 18, 2004, is basically a Huey II with some changes to suit civil certification. It has an FAA-certified 1342 kW Honeywell T53-17B engine, different actuators, nose assembly modifications and a new electrical system. Although aimed primarily at commercial operators, the Bell 210 has attracted US Army interest in the context of its new LUH requirement. Flyaway cost to civil operators is expected to be around $ three million.

Several other Huey upgrades have been proposed, taking advantage of powerful engines such as the 1165 kW LHTEC T800-LHT-801 developed for the now-defunct RAH-66 Comanche, and the 1252 kW P&WC PT6C-67D used in the AB139.

The Bell/Agusta Aerospace (Baac) AB139, although aimed largely at civil operators, may also be regarded as a Huey replacement. Initially developed by Agusta as the A139, it became the AB139 in 1998, when Bell joined the programme and Baac was formed. The AB139 is a twin-engined six-tonne aircraft with a five-blade main rotor and a four-blade tail rotor. Other features include a stealthy hexagonal-section fuselage, a retractable landing gear and (on the military version) high-mounted external stores to maximise the field of fire of its internally mounted, side-firing machine guns. It first flew in February 2001. Deliveries began in 2003, and customers include the US Coast Guard and the United Arab Emirates Air Force.

	Bell first employed a four-blade main rotor for its Model 412, seen here in the form of an Agusta-Bell AB-412SP of the Royal Netherlands Air Force. (Armada/RB)

In Australia AgustaWestland has recently proposed a new 6.8-tonne helicopter, the A149, which would use AB139 technology, but would have a new fuselage and transmission. This project targets operators of the Huey and the 5.4-tonne, four-blade Bell 412, which has a 1342 kW P&WC PT6D-3D Twin Pac. Over 600 Bell 412s have been produced in Canada and under licence by Agusta and Indonesian Aerospace. Recent orders have included a total of 44 Bell 412TPs and Agusta-built AB412TPs for the Royal Saudi Air Force.

Before leaving developments in the Bell series, it is relevant to note that Honeywell has recently launched a new engine family, the 690 kW HTS900 derived from the LTS101, and the 745 kW HTS1000. The HTS900 has been selected for the relatively light Bell 407, but either of these powerplants could be used in twin-engined medium-sized utility helicopters.

The aircraft selected by the US Army to replace the Bell Huey was the twin-engined Sikorsky UH-60 Black Hawk, which can carry eleven troops and first flew in 1974. The current production model is the UH-60L with 1410 kW T700-GE-701C engines and rotor blades of new design, giving a gross weight of ten tonnes. In September 2003 the UH-60M flew with -701D engines, providing 1490 kW and twice the hot end life. The US Army plans to standardise all Black Hawks (and Apaches) on the T700-GE-701D. The service has also decided to buy new-build UH-60Ms, rather than having its fleet of around 1500 UH-60A/Ls remanufactured. There have been references to a replacement for the H-60 being introduced from 2020 in the form of the Joint Multirole Helicopter, which may be used in parallel with unmanned utility air vehicles.

The current US Navy equivalents of the Black Hawk are the multi-mission MH-60R Seahawk and MH-60S Knighthawk, of which 243 and 237 respectively are required. The MH-60R is in low-rate production, while the MH-60S entered service in 2002 and has been used in Iraq. The navalised engines are designated T700-GE-401C and produce 1268 kW.

	The German Army was a major customer for the Sikorsky CH-53G. Some have been deployed to Kabul to support the Nato peacekeeping force in Afghanistan. (Armada/RB)

Derived from the H-60 series, the 12.837-tonne Sikorsky H-92 Superhawk has two 1879 kW General Electric CT7-8A engines, and a much larger cabin that accommodates up to 22 troops. It has been adopted as the CC-148 Cyclone for the Canadian Forces' Maritime Helicopter Programme, with 28 aircraft required to replace the Sea King.

The upper end of the current Sikorsky range is represented by the 33.340-tonne CH-53E/MH-53E, powered by three 3266 kW General Electric T64-GE-416 engines. Some 226 were built for the US Navy and Marine Corps. Sikorsky is developing an installation kit for the uprated 3542 kW T64-GE-419 engine. In December 2004 the company received a risk-reduction contract for an improved CH-53, originally referred to as the CH-53X and more recently as the Heavy Lift Rotorcraft (HLR). This is required to carry an external load of at least 12.25 tonnes (and ideally 13.6 tonnes) for at least 200 km. The corresponding payload for today's CH-53E is 5.45 tonnes. The engines under study include the 4585 kW Rolls-Royce AE1107 from the V-22. Sikorsky anticipates building 154 HLRs for delivery from around 2012.

	US Air Force Special Operations Command (Afsoc) has 13 Sikorsky MH-53J Pave Low IIIEs. This example is flown by the 551 st SO Squadron of the 58 th SO Wing. (US Air Force)

In the longer term, the US Marine Corps would like to carry a minimum payload of 18.1 tonnes (and ideally 22.7 tonnes) for 800 km, implying an aircraft in the 70-tonne class. Bell is studying the QuadTiltRotor (QTR), while Sikorsky is reportedly working on a coaxial rotor design, Lockheed Martin has a fan-in-wing project, and the Boeing approach has not been made public.

The Boeing CH-47 Chinook first flew in 1961 and saw service in the Vietnam War. The last of 481 for the US Army was delivered in 1995, but production continued for export. The US Army currently has around 463, and this number is to grow to 513 under plans for the 22.68-tonne CH-47F and the corresponding Special Operations Command MH-47G. Both versions have 3630 kW Honeywell T55-L-714A engines, a new digital cockpit and airframe modifications to reduce vibrations and shorten the time taken to dissemble the aircraft for deployment in a C-17 or C-5. It is planned that 397 CH-47Ds will be converted to -47F standard, and that 55 CH-47Fs will be new-built. Special Operations' eleven MH-47Ds and 23 MH-47Es will be upgraded to MH-47Gs, with new-build aircraft bringing the total to at least 58 (of 61 planned). Britain is interested in the idea of a Chinook with folding rotors for its Support Amphibious and Battlefield Rotorcraft (Sabr), which will replace the Puma and Sea King Mk 4. Around 70 aircraft are required; these are to enter service early in the next decade.

50 Years Ago On 12 March 1955 this Alouette II (Liron photo Collection) had its maiden flight in the hands of Jean Boulet – and made history. The helicopter was literally built around its engine – an Artouste II – and was to be the first of a breed that eventually led to the current Eurocopter family of rotary-wing aircraft. Always with its trustworthy test pilot Boulet, the machine set a number of records, including that of highest class-altitude by reaching 8209 metres on 6 June, beating the previous record held by a Sikorsky S-59 (which had the same engine) in the process. Apart from still holding the climb speed record to 9000 metres in 17 minutes and 44 seconds the Alouette II is also the first helicopter ever to carry out a rescue operation at an altitude of more than 4000 metres.

The most technologically advanced of America's rotary-wing aircraft is the 24-tonne tilt-rotor Bell-Boeing V-22 Osprey, which is powered by two 4585 kW Rolls-Royce T406-AD-400 engines and made its first flight in March 1989. Test flying was halted for 18 months following two fatal accidents in 2000, but measures have been taken to eliminate the 'vortex ring state' (VRS) problem, and the Pentagon is now set to buy 458 V-22s, subject to satisfactory operational evaluation and a reduction in production cost. The domestic total will consist of 360 MV-22s for the US Marine Corps, 50 CV-22s for the US Air Force Special Operations Command (Afsoc), and 48 modified MV-22s for the US Navy (originally designated HV-22s). Navy procurement is delayed until at least 2010. Initial operational capability for the MV-22 is scheduled for 2008, followed by the CV-22 in late 2009. It is planned to buy a total of 152 MV/CV-22s by FY2011. The provision of gun armament has not yet been finalised, and there may still be concern over the effects of high disc loading in operations from unprepared surfaces and when hovering over water.

On the subject of tilt-rotor aircraft, the much lighter (7.62-tonne) Bell/Agusta Aerospace BA609, which first flew in late 2001, is being marketed as a nine-passenger executive transport, but may yet find military application.