PAUL LEWIS / STRATFORD CUTAWAY DRAWING: MICHAEL BADROCKE & TIM HALL
The US Army's UH-60 utility helicopter fleet is to get a new lease of life. But can modernisation be done on time and within budget?
Helicopter remanufacturing in recent years has gained something of a reputation within the US Department of Defense for producing unpleasant surprises in terms of cost growth and development slippages. The US Army and Sikorsky are hoping to put the record straight with one of the largest remanufacturing programmes undertaken to date to modernise more than 1,200 UH-60 Black Hawks over the course of the next 20 years.
The UH-60M programme is intended to give the army's utility helicopter fleet a new lease of life, adding capability while achieving a significant cut in operating and support costs. The key to doing this successfully is to keep the cost of remanufacturing competitively priced, something the US Navy failed to achieve with the SH-60R Seahawk programme. It subsequently abandoned remanufacturing in favour of all-new MH-60R airframes.
"There is nothing wrong with remanufacturing aircraft as long as you address operating and support cost drivers," says Lt Col Keith Robinson, US Army UH-60 modernisation product manager. "For us it will cost significantly less to remanufacture our UH-60s to the M configuration. We're getting new cabins, refurbished cockpits and tails, new black boxes, upgraded engines and transmissions. We're attacking all the things that need to be attacked."
With 30% of the army's Black Hawk fleet already more than 20 years old and two-thirds of the 1,562-strong inventory comprised of older UH-60As built before 1988, the only alternative to avoiding a drop-off in helicopter numbers is buying new machines at roughly $12 million a time. The UH-60M upgrade is designed to field a machine, with not only another 8,000h of life, but one that is digitally compatible with the army's future Objective Force and the civil global air traffic management (GATM) network, all for around 70% of the cost of a new helicopter.
Modernisation process
The UH-60M programme is subdivided into three major areas focusing on the helicopter's structure, powerplant and dynamic components and avionics systems. The modernisation process will induct a mixed fleet of UH-60As, and more powerful UH-60Ls, UH-60Q and HH-60L medical evacuation (medevac) variants and turn out a commonly configured fleet of 1,217 UH-60Ms, of which about one in four will be equipped for the medevac mission.
Troy, Alabama-based Sikorsky Support Services will be the initial recipient, tasked with assessing and disassembling each helicopter. Of the major structural components, the cockpit, tailcone and tailrotor pylon will be refurbished and shipped to Sikorsky's main Stratford plant for re-assembly and joining with new-build cabin sections and horizontal stabilisers. The UH-60M will feature around 65% new components compared with the Boeing AH-64D Apache attack machine, which reuses 70% of the original helicopter's parts.
The decision to build all-new cabins was driven by the fact that the dynamic and external-stores load bearing mid-section represents the critical path in terms of the Black Hawk's 8,000h airframe fatigue life. "We also wanted to move towards a common configuration and incorporate into the design the lessons learned from corrosion studies, such as from water penetration. Through the use of high-speed machining and CATIA data, we expect recurring costs will be significantly lower than the current sheet-metal design," adds Steve Cross, Sikorsky UH-60M air vehicle lead.
High-speed machining has allowed for a significant reduction in the structural parts count. Examples include the Stage 485 lower frame assembly, which now totals five parts and 56 fasteners compared with five times that number on the UH-60L, integral wiring clip provisions on virtually every tub frame and a single-piece design external-stores support system. Plans to shift to die forging promises to further reduce machine parts in the future, including possibly rivetless butt line beams.
A folding horizontal stabiliser is being added for better transportability, and may be constructed in composite material if a new Israel Aircraft Industries design is adopted. Sikorsky is aiming for a 7kg (15lb) weight saving on the current aluminium design to improve centre of gravity.
The US Army Special Operations Forces (SOF), which operates the Black Hawk at a higher gross weight and with considerably more aft-mounted self-protection systems, plans to adopt all-composite tail cones as part of its parallel MH-60M modernisation. This reduces weight by a further 20kg and is being looked at for the UH-60M in the longer term.
The old stabiliser, together with the Black Hawk's main rotor blades, will be returned to the army for reuse as spares. The UH-60M will be fitted with a new all-composite blade adapted from the larger Sikorsky S-92 and featuring a 90mm (3.5in) wider chord, improved aerofoil and anhedral tips.
Blade benefits
The blade delivers a 240kg improvement in hover weight performance at sea level; or, at a 10,000kg maximum take-off weight at 8,000ft (2,440m), a 12kt (22km/h) faster maximum cruise speed and 37km (20nm) increase in range.
The tailrotor and landing gear are both reused by the UH-60M. In the case of the older UH-60A, the gearbox will be replaced by the same improved durability gearbox used on the UH-60L, increasing the transmission rating across the two engines from 2,800shp (2,085kW) to 3,400shp. Provision will also be included for a rotor brake.
The General Electric T700-701A on the UH-60A and the -701C on the UH-60L versions of the Black Hawk are returned either to the manufacturer or the army's Corpus Christi depot for upgrading to the new -701D configuration at 2,015shp. The new uprated turboshaft will deliver about 4% more power than the -701C.
Upgrading the -701C involves only a handful of changes centred on the combustor liner, material changes to the first- and second-stage blades, along with cooling modifications to the power-turbine third stage, stator nozzles and shroud. A more extensive rework is required for the -701As, including fitting an all-new high-pressure turbine, first-stage compressor blisk, digital electronic controls and anti-icing bleed valve, says Scott Reed, General Electric director T700 US military programmes.
Longer-term plans for an even more powerful Black Hawk hinge on the Improved Turbine Engine Programme (ITEP), formerly known as the Common Engine Programme, which is developing a 3,000shp-class powerplant.
With the funding and timing of ITEP in a state of flux, the army has dropped reference to the UH-60X and instead talks of the more generic Future Utility Rotorcraft (FUR) when describing its future need to externally lift 4,085kg over 135km, or roughly twice the payload/range of today's UH-60A.
The army SOF has a more pressing need for extra power and is looking at the 1,860shp-class GE CT7-8C or Rolls-Royce Turbomeca RTM322 as an interim solution, neither of which will deliver the 25% improvement in fuel efficiency promised by ITEP, however. "The -701D will remain our engine of choice until we get ITEP," says Robinson.
Perhaps the most visible difference in the upgraded Black Hawk will be in the cockpit, with the installation of new instrumentation based around four 200 x 150mm Rockwell Collins liquid-crystal displays. The new multifunction displays (MFD), in addition to providing primary flight, navigation and tactical information, are fully integrated with a digital moving map from Harris and Goodrich Stormscope lightning sensor. An FLIR Systems AQS-22 forward looking infrared imager will be standard on the medevac version.
Meeting requirements
The original intent was to baseline the cockpit on the upgraded HH-60L with two MFDs, but the decision was taken to install a full glass cockpit and replace Northrop Grumman with Collins as the supplier. "We looked at the emerging requirements from the user for battlefield interoperability, situation awareness, GATM and other emerging requirements, and our trade studies showed using four MFDs better positioned us to meet those needs," says Mike Ambrose, Sikorsky UH-60M chief system engineer.
Glass cockpits feature on a number of international S-70s, including Austria's and Turkey's machines, while the army SOF had previously selected the same MFDs for the Common Avionics Architecture System in its MH-60M, Boeing MH-47G and MD Helicopters MH-6 Little Bird upgrades. While the SOF has opted for five MFDs in a portrait layout, the army has chosen a landscape configuration to minimise the size of the instrument panel. As a result, designers have managed to shave 150mm off the dashboard length to improve pilot chin window vision.
The UH-60M suite includes two CMC Electronics flight management systems and dual Honeywell H764 embedded global positioning/inertial navigation systems (EGI) hooked up to a 1553 databus. There is also a triple Arinc 429 databus interface to each EGI for improved redundancy. The helicopter will feature a Smiths Aerospace 16-port Ethernet hub linking radio communications, the new improved data modem (IDM) for messaging and data transfer.
Although not part of the UH-60M Block 1 suite, the Joint Tactical Radio System is a planned addition into which the radios and IDM will be absorbed. The EGI and 8.33kHz VHF/FM radio will provide an initial GATM capability, with a multimode receiver and highway-in-the-sky MFD symbology planned for later blocks.
As a result of funding cuts, the inclusion of a full authority fly-by-wire (FBW) flight control system has been cut from the baseline upgrade and it is now a candidate for the follow-on Block IA version along with a health and usage monitoring system. "We've already established an FBW programme for the S-92 and intend to develop an architecture that is directly applicable to the Black Hawk. We're working with the Federal Aviation Administration to define the requirements for certification," says Leon Silva, Sikorsky manager avionics systems integration.
Replacing the cabling and control rods with the proposed BAE Systems triple-redundant FBW system is projected to shave another 90kg off the helicopter's weight. In place of the pedals, tailrotor thrust will be controlled via a twist grip on the cyclic stick. The position of the crew side egress doors effectively rules out fitting RAH-66 Comanche-style sidestick cyclic pitch controllers, however.
In place of FBW, the initial UH-60M Block 1 helicopter will feature a fully coupled flight director, effectively providing Black Hawk crews with the equivalent of an autopilot. It will permit hands-off approaches and hovering at a predetermined altitude. In the event of pilot disorientation, such as in desert brown-out conditions, there will be the option to execute an automated 500ft/min (2.5m/s) climb out recovery or a go around.
"The UH-60M will give pilots who lose outside visual references a high likelihood of making a safe recovery without hitting the ground. FBW will take this a step further by integrating control laws permitting the helicopter to be flown all the way to the ground hands-off," says Robinson.
New safety features in the UH-60M will include crash-survivable crew and passenger seats from Simula and Martin Baker, crashworthy external fuel tanks and better electric wire shielding from electromagnetic interference (EMI). For added self-protection, the T700-701Ds will feature GE's improved hover infrared suppression system, which further reduces exhaust temperature while delivering a 2% recovery in performance.
Aside from making provisions for the Goodrich AVR-2B laser warning system and integrating the existing radar warning receiver into MFD, the Black Hawk's aircraft survivability equipment has been left largely untouched. Plans to equip the helicopter with the BAE Systems ALQ-212 Suite of Integrated Infrared Countermeasures and ITT ALQ-211 suite of integrated RF countermeasures have been undermined by cost, which the army estimates could be as high as $3 million per machine. Short of a major change of tack following the Iraq war, both systems will have to await FUR.
Sikorsky has shipped the first of four UH-60M prototypes - a remanufactured UH-60A - to its West Palm Beach test facility in Florida ahead of a planned first flight on 19 September. The second test machine, a rebuilt UH-60L, will follow a month later. A shortfall in funding and the delay resulting from changing the MFD supplier has pushed back the first flight of the second pair of aircraft, a new build HH-60M and another rebuilt UH-60A, to January and April 2005.
Stretching the line
"We ran into some issues underestimating the cost of the programme and additional testing requirements, as the result of which there is a nine-month schedule delay," says Robinson. The brunt of the two-year flight-test programme will fall to the first two helicopters. The third machine will be used mainly for EMI chamber testing and the final HH-60M will be dedicated to validating medevac equipment. The army has added another four preproduction machines with which to conduct operational testing at the end of fiscal year 2006. Delivery of low-rate initial production helicopters is due to begin the same year.
Current plans call for remanufacturing a maximum of 60 helicopters a year, stretching the line close to 2025, by which time FUR is expected to be in service. The army had hoped for and would still like to see a higher remanufacturing rate, but plans to procure small numbers of new-build UH-60Ms starting in FY2008 to complete its purchase objective of 1,680 Black Hawks.
To sustain the fleet in the near term, the army is taking 193 of the worst shape UH-60As and putting the airframes, powerplants and components through an A-to-A recapitalisation programme at Corpus Christi. "Our intent is to give the machines another 20 years and carry the non-remanufactured fleet out far enough before inducting them on to the end of the M programme," says Robinson.
Early results from the UH-60M programme show the helicopter coming in over specification on external lift capability, under-weight and, compared with the UH-60A, $300 an hour cheaper to operate. "I think this will turn around some people's perceptions about remanufacturing programmes," predicts Robinson.
Source: Flight International
