The Sikorsky UH-60 Black Hawk has been a cornerstone of US Army aviation for a long time, but its enduring qualities have persuaded the army to begin a huge drive to update the aircraft
Paul Lewis / WASHINGTON DC / fort eustis, virginia
Not only has the Sikorsky UH-60 Black Hawk been in production for close to a quarter of a century, but nearly 25% of the US Army's fleet of 1,500 machines are at least 20 years old. Even more remarkable is the fact that, as a component of the future US Army Objective Force, the UH-60 will remain the cornerstone of army aviation to 2025 and beyond. To get there, the US Army has embarked on a massive modernisation drive that will give virtually every Black Hawk a new lease of life.
To this end, in March the Pentagon's Defense Acquisition Board (DAB) approved a two-step programme, starting in 2004 with the recapitalisation and upgrade of 1,217 UH-60A/L helicopters to the improved UH-60M standard.
The DAB also recognised the longer-term requirement for an increased payload/range helicopter, which Sikorsky hopes to fulfil with 225 heavily modified Black Hawks, more loosely designated the UH-60X.
"Black Hawk will be the army's Objective Force utility helicopter and so is going to be around for some time to come," says Col William Lake, utility helicopter project manager, US Army Aviation and Missile Command. "The 'M' programme gets all older UH-60A models into the future. The smaller contingent of 'X' aircraft will be able to lift, in hot/high conditions, a 9,500lb [4,300kg] external load and that would give us the remaining capacity we need to lift the future Objective Force family of equipment."
The 'X' hinges, to a large extent, on the development of a new centreline engine capable of delivering a significant jump in fuel efficiency (see accompanying story), for which the necessary technology will take the rest of the decade to mature. The army has elected to take an evolutionary route, starting by fixing some of the more pressing problems with its older machines, followed by the UH-60M package of structural, mechanical and avionics enhancements, which will later serve as the building blocks to the UH-60X.
Recapitalisation plan
Army plans call for the modernisation of up to 60 helicopters a year up to 2024, starting with a low-rate initial production batch of 12 machines to be delivered in 2005. "Full-blown production of the UH-60M will start in 2007," says Lake. "In many cases these aircraft are already over 20 years old, and so we've come up with an 'A to A' recapitalisation designed to give older Black Hawks another 10-15 years of extra life until they become Ms."
Recapitalisation is focused on co-ordinated overhaul, repair and, where needed, replacement of all of the helicopter's primary items, such as engines, transmissions, rotors and actuators. At the same time, corrosion is treated and maintenance processes are reworked to tighter tolerances, with the aim of reducing recurring depot visits, keeping helicopters operational for longer and cutting costs. The army plans to recapitalise 250 predominantly National Guard UH-60As over the next 12 years to buy breathing space for the UH-60M programme.
At the heart of the UH-60M upgrade is a new 1553B databus and avionics suite, including four 8 x 6in (20 x 15cm) multifunction displays (MFD) in place of the Black Hawk "boiler gauge cockpit", as well as two control display units (CDU) and dual digital flight controls. The displays will be competitively bid over the next 18-24 months. To expedite the programme, in the interim, the first three test helicopters will be baselined on the UH-60Q medevac conversion equipped with Litton MFDs and CMC CDUs.
The lead helicopter, a modified UH-60A, is to fly in 2003, followed by a converted UH-60L. The third test machine will also be a UH-60A, but modified to the HH-60M medevac configuration. The army requirement is for up to 357 such helicopters, most of which are expected to be UH-60M conversions supplemented by about 50 UH-60Qs and new HH-60Ls. The fourth and final test machine is planned to be a new-build "M" and will be equipped with production standard cockpit displays.
Bare minimum
The initial intent had been to equip the UH-60M with just two MFDs. "Two displays provide just the bare minimum," says Mike Cuppernull, Sikorsky UH-60M/X programme manager. "There is a strong case to be made for a utility machine to have four MFDs for the sake of information display flexibility, but the real reason is battlespace situational awareness and digital connectivity."
Other new items for the UH-60M will include commercial off-the-shelf cockpit voice and data recorders, dual Honeywell embedded GPS satellite /inertial navigation systems, digital map, Stormscope, digital communications with HF radio, an improved data modem to be furnished by the army, and provision for mission planning equipment.
Structural rework of the helicopter is to be focused on the upper deck and cabin area, with the aim of strengthening the centre section and producing an airframe good for another 8,000h. The intention was to remanufacture the cabin and upper deck, along with the transmission beams, servo beam rails and tail cone. A new plan now being pursued is to build and fit new cabins, similar to that originally planned by the US Navy for the SH-60R upgrade before it was dropped in favour of new build MH-60Rs.
"In the upper deck area we have a lot of parts like transmission beams that have no life limits," says Cuppernull. "We believe that to remove these from the surrounding structures, put in strengthening and rebuild the area piece by piece would require excessive recurring labour, compared with breaking off the tail at the known manufacturing point and just building a new cabin section."
Retrofitted airframes
Early-build UH-60A airframes will be retrofitted with the External Stores Support System (ESSS), which is already used in half the army's fleet of 1,000 later 'A' models and all its 500 UH-60Ls. The UH-60M will be equipped with the new extended-range fuel system in the form of either 1,700litre (450USgal) or new 870litre crashworthy external tanks, up to four of which can be mounted on the two ESSS pylons.
A third major task is to bring the UH-60A's powerplant in line with the UH-60L's more powerful 1,445kW (1,940shp)-rated General Electric T700-701C engine. As well as providing a 24% boost in power, the engine offers more robust, longer-endurance components and ultimately lower support costs. The older Black Hawk model will also be retrofitted with the latest uprated 2,535kW improved durability gearbox. This, combined with new 0.41m (16in) wide-chord main rotor blades, will give the UH-60M a 20% increase in payload/range performance over the UH-60A and the ability to lift an external load of 2,383kg out to a radius of 135km (75nm).
The DAB has been much more circumspect about the proposed UH-60X, endorsing the operational requirement (ORD), but leaving open the option of selecting a type other than Black Hawk. What is clear is that neither the UH-60L nor the improved M version is capable of meeting the threshold requirement of lifting 4,300kg over 135km, at 4,000ft (1,200m) on a 35íC (95íC) day. "That's roughly twice the maximum capability of the UH-60M," says Lake. "The T700 engine will give you either the range or the lift, but not both."
Common answer
The answer, according to the US Army's Aviation Applied Technology Directorate, is the Common Engine Programme (CEP), which is focused on developing an all-new 2,235kW-class turboshaft - not just for the UH-60X, but also for other members of the Black Hawk extended family and the Boeing AH-64. The engine has some major goals to meet if it is to comply with the ORD, including a 25% cut in specific fuel consumption and a 60% improvement in power-to-weight ratio.
The UH-60X, as defined, would incorporate a number of major structural and dynamic component changes over and above those planned for the UH-60M. The additional range will require a larger, 1,560 litre fuel tank and the adoption of the larger S-92 helicopter's 0.41m longer main rotor blades, drive train and controls. This, is turn, would dictate a corresponding 0.41m plug in the tail cone to ensure main and tail rotor clearance and, to maintain the centre of gravity, a 0.51m extension to the forward cabin.
Given the drawn-out schedule for fielding the helicopter in 2017, it is not yet certain whether the UH-60X will be based on a remanufactured UH-60L/M, a new-build airframe or a completely different machine such as the S-92. "What we love about the Black Hawk is that it has great crashworthy features, something that a commercial helicopter would not," says Lake. "So there is great impetus to do the UH-60X, but when you start plugging the fuselage, you add risk and the CEP is part of this. We're going to have to do a good bit of research and see how things go."
Source: Flight International
