Will The Blackhawk Wear RAAF Roundels?

Most operational use of Australian helicopters, such as in Vietnam and the Middle East, has been in conjunction with US allies. If Australia had been operating a non-American helicopter in these roles, it would have been considerably more difficult to support.

The RAAF approves of the selection of the Sea Hawk for the RAN because its Black Hawk stablemate gives a high level of engine and airframe commonality for the two services. The Black Hawk also emerges operationally as a clear favourite with the RAAF – pilots find it difficult to conceal their enthusiasm for it and be even-handed in their comments on other contenders.

They point out that the Black Hawk is built like a truck and designed to be as foolproof as possible – although this has apparently led to some over-confidence in the US Army where a worrying rise in the accident rate has been attributed mainly to pilot error.

In the words of one officer, “It is the only one purpose-built for the job we do. It is ugly but effective – just like the F-4 Phantom. ” The one problem with the Black Hawk may be that it is the most expensive of the competing machines, but as the officer observed, “In any business, you get what you pay for. ”

Designed to replace the US Army’s UH-1 Huey in the ratio of 15 for 23, the Sikorsky UH-60A Black Hawk is that army’s first true squad-carrying assault helicopter. Its primary mission is to transport infantry units into combat, resupply those units while in combat, and perform the associated functions of aeromedical evacuation and repositioning of reserves. However, its inherent growth potential has enabled an improvement programme that will develop its capability in a number of roles.

The Huey is known as a dangerous and cantankerous beast with a reputation resembling the Sopwith Pup of World War I. The probability of mechanical failure is quite high with the Hueys and they have probably been responsible for more death and injury than the rest of the RAAF put together.

Since the Huey first flew in the mid-1950s there have been major developments in helicopter technology and efficiency, with the pace of new design developments coming particularly fast in the last few years.

For example, when a Huey lost oil from its gearbox, it would be lucky to keep running for three minutes. The Black Hawk is required to keep running for 30 minutes without oil. In addition, the Huey has the old Bell teetering rotor system which will not tolerate negative G. Helicopter experts emphasise that the Bell system is a very good one provided you understand this one lethal limitation.

Unfortunately, it largely precludes nap of the earth flying, down among the weeds, where helicopters are increasingly forced to fly – often at considerable speeds – in the modern battlefield.

In Europe today, 50ft altitudes are operations normal for military helicopters which spend much of their time with their landing gear brushing the tree tops. Helicopters use their speed and manoeuvrability at low levels to limit their exposure to small-arms fire. Their main worry today is the shoulder-launched missile which can now reach well above the old 1500 ft level where most helicopters once felt safe from small arms ground fire.

The original utility Huey – the UH-1B – has been used for transport, light SAR and training by the RAN and RAAF for 20 years and is being phased out and replaced by the AS350B Squirrel. The search for a replacement of the later workhorse H model Huey has been precipitated by losses of about one per year which has reduced the total number in service from about 40 at the height of the Vietnam War to 30, with no replacements bought since the early 1970s.

With eight Hueys committed to UN peacekeeping forces in the Middle East, the RAAF is left with only 22 H models as its main utility helicopter force. A request for tenders to replace the UH-1Hs which hit the road on April 19, 1984, is deliberately written to keep options as wide as possible.

The three principal contenders are the Aerospatiale Super Puma (reviewed in our December ’84 edition), Sikorsky UH-60A Black Hawk and the Westland W30-300/400 series – a development of the Lynx series.

The Australian Army’s fundamental requirement is to be able to lift a minimum squad of 10 fully equipped troops along with a crew of four – two pilots and two gunners.

Production models of the Black Hawk began to leave the line in early 1979 and the army is committed to the acquisition of about 1100 of these through the eighties.

The Black Hawk – developed in response to the army’s utility tactical transport aircraft system (UTAS) requirement is designed to not only replace the ubiquitous Huey in combat support aviation companies, air cavalry units and aeromedical evacuation units, but to offer a significantly improved capability in all these roles. In combat support for instance, a single Black Hawk can, in the space of one hour and 20 minutes, make eight 16km trips into a hostile landing zone to put 88 men on the ground, whereas a Huey at the same time could make only five trips and deliver 35 infantrymen. Development of the Black Hawk began in 1972 and the first YUH-60A prototype went into a competitive fly-off with a design by Boeing-Vertol in 1975.

Features of the design included –

TITANIUM rotor blade spars for a lighter, stronger structure and unlimited service life.

GLASSFIBRE rotor blade skin to protect the spar and permit repairs in the field.

AFT-SWEPT rotor blade tips to reduce control loads and give substantial increases in speed.

ELASTOMETRIC rotor heads, requiring no lubrication, to improve reliability and maintainability, reduce cost and lessen vulnerability.

GREASE-lubricated gearboxes for lower maintenance needs and reduced vulnerability.

8/-F/LAR vibration absorbers on the rotor head, giving smoother flight, greater reliability and a 40 per cent reduction in maintenance man-hours required.

PRESSURISED blade spars with gauges to provide a fail-safe system for confirming blade structural integrity.

A CANTED tail rotor, for increased vertical lift and greater centre of gravity travel.

The requirement that the UTTAS helicopter should be air-transportable in the C-130 Hercules (two in a C-141 Starlifter and six in a C-5 Galaxy) imposed limits on overall dimensions and is a major factor in the Black Hawk’s notably squat profile. Even more stringent was the time allowed and the number of men required to prepare, load, unload and erect the helicopter ready for flight. Original army targets were not fully achieved but a seven-man team prepared a YUH60-A for loading in one and a half hours and loaded it in 30 minutes. Reassembly by a six-man team requires less than two hours.

(Its original profile was even lower but the main rotorhead had to be raised 38cm to reduce vibration caused by the main rotor blades passing through the airflow deflected upward by the nose of the helicopter. The rotor is now dropped to its original position for air transport by removing a rotor shaft e)(tender. )

Much of the new technology in the S-70 and the key to its ability to meet the performance and maintainability requirements is to be found in the design of the main rotor and rotor-head. Sikorsky combined a specially developed high-lift aerofoil section (SC-1095), which provides the required lift at low speed and performance at high Mach numbers, with a titanium spar that resists the torsional loads that the use of such an aerofoil incurs. The blades have 18 deg of twist from root to tip and the tips are swept back 20 deg over the outer five per cent of the span to reduce control loads and Mach number effects.

Blade construction around the oval-section spar comprises a Nomex honeycomb core, graphite trailing edge and root, plastic skin, plastic leading edge counterweight and titanium abrasionproof leading edge.

The spars are pressurised to simplify blade inspection – although Sikorsky is also developing an all-composite blade to match those already available on the Super Puma. The main rotor blades are fully articulated and connected by elastomeric drive bearings to a one-piece forged titanium rotor head. The bearings require no lubrication and have an average life of about 3000 hours before being replaced on condition on the basis of visual inspection.

The four-bladed tail rotor uses the same SC1095 aerofoil section as the main rotor and is of graphite-epoxy construction. With only about 10 per cent of the number of parts used in older tail rotors and 20 per cent of the weight, the Black Hawk’s tail rotor needs no lubrication and has greatly improved reliability.

Sikorsky claims that the unusual mounting of the tail rotor on a pylon that is canted 20 degrees off the vertical produces 180kg of lift at a cost of 22kg in main rotor lift, thus allowing the main rotor diameter to be 14 per cent smaller with a 454kg reduction in gross weight for a given performance.

The area of the pylon on which the tail rotor is mounted is sufficient to allow a controlled landing to be made if the tail rotor is shot off under combat conditions. A large one-piece tailplane is fitted to keep the fuselage at optimum angle with speed variation.

In the hover the tailplane has an up-angle of about 34 degrees and this decreases gradually to zero as speed increases from 30kt to 80kt. In addition, the tailplane is used through a range of about two degrees for auto stabilisation. Tailplane control is based on sensing the airspeed, collective-lever position, pitchattitude rate and lateral acceleration, and serves to damp out turbulence as well as the fore-and-aft pitching that tends to be set up by the canted tail rotor pylon during power changes or gust-induced sideslips.

This feature resulted in the triple-fatal loss of one aircraft during development flying when the airspeed sensor for the tailplane actuating system was inadvertently left unconnected during routine maintenance. As the aircraft transitioned from hover to forward flight, the tailplane did not automatically change angle and as speed built up the nose was forced down to an attitude from which recovery was impossible.

A manual backup system was available and functioning and the reason for it not being used remains unexplained, although the pilots may have failed to analyse the nature of the problem in time.

The cockpit of the UH-60A is laid out for two-pilot operation with full dual controls and duplicated instrument panels. A centre console and overhead panels carry the radio and systems controls. Power and engine indicators and warning panels are on the centre of the main panel between the flight instruments.

Full IFR instrumentation is included and a flight director computer is carried for navigation tracking and ILS, along with a Hamilton Standard digital autopilot (AFCSA) and Bendix Autostabiliser. US Army specified radio include VHF/AM, UHF/ AM and VHF/FM and there is space for battlefield equipment such as an AN/ALQ-144 infra-red jammer, AN/APR-39 radar warning receiver and XM-30 chaff dispenser.

While these electronic devices give some protection against the increasingly worrying threat of SAM missiles, US Army Black Hawks also carry two 7. 62mm M-23D machine guns at the cabin doors. However experience such as Grenada has proved that these are insufficient. Black Hawk main rotor blades can absorb hits from 23mm HE or incendiary shells and fuel tanks in the rear fuselage can absorb a hit by a 12. 7mm shell.

The Black Hawk has demonstrated to the army’s satisfaction that it can fly for a minimum of 30 minutes after being hit anywhere in the lower hemisphere by a 7. 62mm round fired at a range of 100m. To this end, the main and standby systems are widely separated, electrics and hydraulics are duplicated, avionics are grouped in the nose well away from the fuel tanks and essential components are given protection wherever possible by redundant equipment.

The Black Hawk’s fixed tail-wheel type undercarriage has the remarkable ability to absorb a landing impact of 9G at a descent rate of 35ft/sec (10. . m/sec) without allowing the fuselage to touch the ground. This is the equivalent of an autorotating descent at 2500ft/min (762m/min) with the use of collective pitch. The cabin structural box is designed, in these conditions, to withstand parallelogram distortion under simultaneous loads of 20G forwards and 10G downwards. Internal equipment will not break away from the structure at less than 25G.

During early autorotation tests, one prototype encountered unexpected wind shear and hit the ground tail wheel first at a descent rate of 42ft/sec (12. 8m/sec) before flopping onto the main wheels. Only the tailwheel, axle and tyre were damaged and flying was resumed next day.

In another test incident separation of glassfibre covering a rotor blade trailing edge during a low-level night flight resulted in vibration requiring an immediate landing through a plantation of young pine trees. None of the 14 occupants was injured and the helicopter was flown out next day after main and tail rotors had been changed.

Black Hawks had their baptism of fire when US forces invaded Grenada during 1983 and demonstrated their inherent combat survivability when several sustained heavy ground fire damage but completed their missions.

Although a number of Black Hawks were damaged and disabled in Grenada, it proved to be a reliable and durable bird. The army proudly pointed to one UH-60 that a wounded pilot kept flying with 45 holes in the airframe, two in the main rotor and one in the tail rotor. An enemy soldier had reportedly lain on the ground, emptied an AK-47 into the helicopter, reloaded and continued to fire.

However, as the RAAF points out, it is the location of the hits that counts, not their numbers. One RAAF Huey in Vietnam came back with 23 hits while others went down after two or three. (Of 11,000 helicopters lost in Vietnam, about 6,000 were due to accidents rather than enemy action. )

In Grenada the Black Hawk operated in the assault, transport and medical evacuation roles and it was found that in combat conditions, they were able to fly with 20 or more troops on board, provided that seats were removed. The Black Hawk actually “cubes out before it weights out” as one officer put it, which bodes well for Australian region operations in hot and high conditions.

Although it worked well in combat assault, the Black Hawk was found to lack protection from small arms fire for the troops being carried, the pilots’ visibility was not very good and it could not really be used in a fire-suppression role. Although the pilot positions are armoured, the aviators would like to see more protection for the troops, perhaps using Kevlar floor mat protection, despite a small weight penalty.

They say that a 50 calibre mounting on each side is not adequate for fire suppression and the Calvigny (Grenada) barracks, in which three Black Hawks were lost to small arms fire and landing collisions re-emphasises the need for dedicated gunships to suppress the LZ (landing zone) before the assault helicopters arrive.

The UH-60A matches or exceeds the original UTTAS requirements, carrying 11 troops with a 2. 3-hour endurance, cruises at 145kt at 4000ft on a 33degC day with a rate of climb at this altitude and temperature of 496fpm.

Current Black Hawk power comes from two GE T700S in four independent and easily-replaced modules. The T700-GE-700 variant in the Black Hawk is rated at 1,543shp for max continuous single-engine operations, although the normal continuous power with both engines in use is 2,791shp. There is a two-minute limit of 3,210shp and a 10-second burst at 3,768shp is permitted.

Sikorsky foresees a likely requirement for at least 25 per cent more engine power in order to lift the US Army’s new 3,402kg high mobility multipurpose wheeled vehicle (HMMWV}, an uprated transmission, upgraded avionics that may involve fly-by-wire or light, better air transportability, improved aircraft survivability equipment (ASE), better capability in desert environments, single and dual external cargo loads up to 5443kg compared with the single-point 3630kg external load at present and possibly provision for air-to-air self-defence weapons such as the GD Stinger. Sikorsky has foreshadowed installing the more powerful Rolls Royce/Turbomeca in an “Anglicised” version it has proposed in conjunction with Shorts for the UK Air Staff Target (AST) 404 Puma helicopter replacement programme. This requires a helicopter to carry 13 fully-equipped troops at speeds up to 150kts over a 65nm radius of action.

Although this programme, for deliveries beginning in 1989, appears to be out of phase with the RAAF requirement, the step up from the current 1600 to well over 3000shp would provide substantial improvements in performance.

A number of lifetime improvements are underway or planned for the Black Hawk, the most significant at the moment being the External Stores Support System (ESSS of ES3) of removable stub wings which attach to each side of the fuselage above the cabin windows and provide four wet hardpoints. These were designed to give the Black Hawk a transatlantic self-deployment capability with a range of 1,150nm against a 10kt headwind by carrying on the wing/pylons two 1703 litre and two 871 litre tanks.

This sort of self-deployment capability could be of great value to the RAAF which faces a fairly extensive potential theatre of regional operations with nothing like the density of support equipment which would be available for a major hot war in the northern hemisphere.

In view of the fact that it may be many years before the RAAF acquires dedicated attack helicopters, the armament carrying capability of the ESSS system is also of great interest.

The pylons allow the Black Hawk to carry additional armament such as the M-56 mine dispenser (80 mines in each) or Hellfire AGM missiles, or other gun pods up to 30mm calibre, rocket pods, side-looking radar, ECM pods or other sensors. The Black Hawk can carry 32 Hellfires – four on each hardpoint and 16 in the cabin, reloadable on the ground and the addition of an appropriate nose, canopy or mast sighting system would make it a versatile anti-armour weapon.

Another use for ESS is transporting scout motorcycles so that the cabin is free for personnel and other equipment. The motorcycles are ideal for mobility for light, ground reconnaissance teams and can also provide mobility for ground laser locator/designator (GLLD) teams which can be inserted by a Black Hawk which can then launch Hellfire missiles in the indirect fire mode at targets designated by the same teams.

Other improvements under development for the Black Hawk include – more durable gearboxes, low-cost composite main rotor blades that eliminate the titanium main spars used at present, composite rear fuselage using rigid foam construction to reduce cost and enhance survivability against 23mm hits and hover IR suppressor that will be less than half the weight of the present system.

In a battlefield without boundaries, where the fast-moving fighting Is intense and continuous during daylight and darkness and in all kinds of weather, force multipliers such as helicopters; will be vital for tactical flexibility and maximum combat effectiveness.

New battlefield concepts emphasise disruptive deep attacks against second-echelon forces with simultaneous close-in combat against first echelon forces.

This has become known as the “extended battlefield” – itself not a new concept, but one in which the ability to see and strike deeply at the right time provides the way to win even when the threat enjoys an overwhelming superiority in force ratios. To achieve this, the US Army has recognised the need for a modernisation plan involving force structure, training, doctrine and material. An important element of this is a high-technology “test bed” infantry division (DELTA FORCE) which will this year Transition into a technologically advanced, combat-ready light infantry prototype force, capable of rapid strategic deployment and characterised by tactical mobility, firepower, survivability and sustainability. While retaining utility on the European battlefield, emphasis will focus on the ability to execute worldwide contingency missions. The application of two Black Hawk companies (14 aircraft each) during field test exercises is a vital element of the unit’s development plan.

The importance of night flying capability has been realised and development programmes are underway to provide night vision for the crew, initially using the new lightweight night vision goggles.

Beyond this, particularly for the European theatre where ambient light at night is generally low because of overcast or fog, there are a number of forward-looking infrared (FUR) sensing systems under trial. The type of device and its sensitivity, display and symbology characteristics will depend on the type of flying involved. A maximum capability configuration could consist of a pilot night vision system (PNVS), integrated helmet display and sight system (IHDASS) and associated multiplex bus and symbol generator, similar to systems in use in high-performance combat aircraft.

The result due to be announced shortly of the AST404 contest between the three most serious contenders for the AMF order (Super Puma, Westland W30-404 and Black Hawk) will be an interesting indication of which way the RAAF might jump.

There is some concern in the UK that the Black Hawk designed originally to accommodate an 11-man squad is to small though Sikorsky has reconfigured the cabin for 13 troops.

The W30 has plenty of room but there is concern that it lacks sufficient scope for development through to the end of the century and while the Super Puma has plenty of size it cannot be really “slammed” quickly on the ground.

The Black Hawk’s tail wheel which allows it to make a low level, high-speed approach to the LZ before flaring for a, run-on tail-down landing, appears to have won it many friends.

But even the sturdiest and most battle-worthy helicopter is an easy target, being slow-moving, big and noisy. It is not only vulnerable to surface-to-air missiles and anti-aircraft fire, but ta small-arms fire, as events in Vietnam, the Falklands and Grenada has proved this.

The only self-protection on which it can depend is to get in and out of a hot zone as quickly as possible, taking full advantage of all available trees and hill cover.

This means that a prime requirement is the ability to offload and recover troops as fast as possible with the absolute minimum time spent on the ground.