Hawk Improves With Age

The Hawk’s engine, in current export aircraft, the 2585 kg Rolls-Royce Adour Mk 861 turbofan, is almost certainly the most economical and well-proven powerplant in its class, i. e. of engines suitable for a transonic trainer and ground attack aircraft. The Adour’s SFC is clearly not as low as that for the Garrett TFE731 used in the CASA C-101, but such high bypass engines pay a steep price in terms of thrust decrease with forward speed, making them more suitable for the basic training role, rather than advanced flying training and close support duties.

The extensive operating experience of the Adour in the far more demanding environment of the Sepecat Jaguar and Mitsubishi T-2, coupled with the vice-free handling characteristics of the Hawk, must be given much of the credit for the aircraft’s remarkably good safety record. Although the type is now approaching a worldwide total of 200,000 flying hours, only one Hawk has ever been written off in the course of RAF flying training duties.

Another noteworthy feature of the Hawk is its fatigue life, a safe 6000 hours of flying to the most severe design load spectrum ever applied to an aircraft in this class. Although other trainers claim longer lives, in every case the design spectrum was far less demanding. To be cynical, it might be argued that Britain knows more about fatigue loads because of structural failures in some early postwar commercial British transports (in certain cases first encountered in Australia due to intensive regional utilisation), as a result of which the RAF started gathering fatigue load data well ahead of most other air forces. The manufacturer’s thorough approach to fatigue life is also illustrated by the fact that a complete aircraft is being tested, whereas certain of BAe’s competitors use only a partial structure.

Testing of the Hawk fatigue specimen is proceeding well ahead of aircraft utilisation. One technically interesting sidelight arises from the fact that, although symmetric loadings are well understood from previous RAF records, fin loads had to be estimated by the aircraft’s designers. Recently two Hawk fins have been strain-gauged, and their loads were recorded in the course of flying training at RAF Valley and weapons training at RAF Brawdy. It transpired that the Hawk’s fin fatigue loads had been over-estimated by a factor of four, which was clearly better than an error in the opposite direction.

The principal aim in developing the Hawk as a trainer was to produce an aircraft that was better than any of its competitors, yet had an operating cost that was more in line with that of a basic trainer such as the MB-326. Aside from avoiding costly rework programmes at part-life, and using a turbofan to give the same fuel flow as a much less powerful turbojet (such as the Viper), a great deal of attention was paid to reliability and ease of maintenance. For example, in replacing the Gnat and Hunter in RAF service, the Hawk reduced defect rates by 36 and 70 per cent respectively, winning substantial bonus payments for BAe. Maintenance man-hours per flying hour were immediately reduced by 32 and 40 per cent respectively. At RAF Valley, Hawks have averaged up to 40 hours/month, and individual aircraft have flown up to 60 hours in a month.

Although operational use is of no immediate relevance in the Australian context (the situation could change if the RAAF saw the need for a low-cost close support aircraft, or if local industry acquired regional rights), the Hawk was designed from the outset with equal emphasis on the ground attack role. In this area it again has some major advantages, notably a 500 knot attack speed and the ability to carry a 30 mm cannon in combination with six 450 kg bombs and full internal fuel. The need for a high attack speed is worth emphasising since it has been found in several shooting wars that the SA-7 man-portable weapon is now widely available and is lethal against slow-flying aircraft.

The Brits found in Oman that the BAe Strikemaster (roughly equivalent to late production MB-326s) was initially very effective as a light attack aircraft, but the advent of the SA-7 forced its withdrawal in favour of the Hunter and Jaguar, which were operated above 450 knots. The Israelis found in the 1973 Middle East war that the earlier models of A-4 were much more susceptible to damage from the SA-7 than later, faster variants. In the mid-1970s a cross-border raid by the Rhodesian forces into Mozambique led to the acquisition of SA-7 operating manuals, quoting a maximum target speed of 420 knots, which effectively ruled out the use of the Vampire. This cut-off speed may have been increased somewhat, but an aircraft that can fly at 450-500 knots with external stores is clearly a safer bet than one capable of only 400-450 knots.

In the light of the Hawk’s undoubted qualities in both the trainer and ground attack roles, sales have not been as widespread as was originally predicted, reflecting the generally inactive state of the market. The Hawk was launched on the back of a British MoD order for 176 aircraft, all but one of these T Mk 1s being supplied to the RAF for flying training and weapons instruction, In war, 80-90 of these RAF aircraft would have an operational role, primarily in the low-level air defence of key airfields, although the two-pylon T1 is sufficiently flexible for use in ground attack, should this be required. All 176 T1s have now been delivered, and work has commenced to modify selected aircraft to the ‘war-role’ standard. The T1 was always seen as a minimum-cost variant, but some money is being spent to upgrade it to a better equipment standard, with improved ratios and AOA indication.

Early export aircraft were better equipped but had basically the same 2420 kg engine, the Adour Mk 151 becoming the Mk 851 for overseas customers. The principal order was the Finnish contract for 50 Mk 51s, which was finalised in 1978, with deliveries commencing in 1981. The Finnish manufacturer Valmet is making the fins for these aircraft, and assembling all but the first four, which were supplied directly by BAe. The company is reticent on its other export orders, but various published reports refer to 12 Hawk Mk 52s having been delivered to Kenya in 1980, and a total of 20 Mk 53s having been ordered for Indonesia.

The introduction of the 2585 kg Adour Mk 861 led to the ’60-series’ Hawk, of which eight are reported to have been ordered by Zimbabwe. The first four to be delivered were the subject of a guerilla attack last year (plastic explosive charges were thrown down the intakes); one was written off, one was repaired locally, and two were repaired in the UK.

Recent BAe stationeries to the effect that a total of 114 Hawks have been ordered for export add credence to newspaper reports that 16 are on order for Dubai (Mk 61) and eight for Abu Dhabi (Mk 63). It might also be conjectured that the missing Mk 62 relates to some of the aircraft in a Venezuelan order, which was cancelled last year, probably due to a clash of funding demands with the F-16A programme. Since the Mk 62 designation has not been reallocated, it seems possible that this deal may yet be consummated.

The manufacturer is legally committed not to confirm the existence of several of these Hawk export orders, but BAe is in any event relieved of the pressure to publicise its smaller successes by the Hawk’s outright Win in the US Navy VTX Contest. As the world’s most important competition for aircraft in this class, the VTX programme has undoubtedly been a valuable endorsement for the Hawk. What makes_ this victory all the more noteworthy is that the US Navy had originally envisaged the winner as being a twin-engined aircraft yet chose the single-engined Hawk in preference to five twins: the Alpha Jet, an updated T-2 Buckeye, and three new projects designed specifically to meet the VTX requirement!

The Hawk is the basis of a new US Navy training system that will take over from both the T-2 and the TA-4. For this system, the Douglas Aircraft division of MDC is the prime contractor, with responsibility for systems integration and final assembly of the Modified Hawks at Long Beach. The principal subcontractor for The airframe is BAe, and that for the simulators is Sperry. It may be noted that simulators account for only 10 per cent of VTX programme costs, but reduce the number of aircraft required by 40 per cent. Computer-based management of training is worth a further saving of eight per cent. Some 70 per cent of the programme Costs will be spent in the US, but BAe will receive 50 per cent of The airframe workload, making the VTX an even bigger programme for the company than the AV-8B.

The Hawk’s win was announced on 19 November 1981, and The team was kept going until the following September on a ‘sustaining engineering’ contract. This was followed by the ‘preFSD’ (pre-full-scale development) phase, which will run until mid-1984, and is worth $US15. 6 million, of which $US8. 0 million was voted in FY82. This will be followed by the FSD and production phases.

As currently envisaged, production will take the form of 253 carrier-capable T-45A Hawks, preceded by 54 T-45Bs, an Interim version capable of Navy-type approach arid landings for ‘field carrier landing practice’, but not capable of carrier operation.

The T-45B is scheduled to fly in February 1987, with Deliveries starting in the following year. It will have an undercarriage strengthened for a 5. 2 m/sec sink rate, and lateral airbrakes. in place of the current ventral one, and a modified cockpit, but it will not have an arrester hook or catapult facilities. The T-45A will have a 7 m/sec undercarriage, twin nosewheel catapult provisions, a new nose section, and a modified rear fuselage with an arrester hook. It will first fly in April 1988, and enter service. in 1991. Other changes planned include the use of Martin-Baker US10LV seats and the Adour 851-49 with strengthened intermediate casing.

Whereas the RAF Hawk has a clean gross weight of 4934 kg with 1272 kg of fuel, the T-45A will gross 5624 kg with 1327 kg of fuel. It is also reported to have an approach speed of 121 knots, a maximum level speed of Mach 0. 85, and an average fuel consumption of 621 kg/hr. Mean flight hours between Failures is estimated at 3. 0-3. 5, and it will require 8-10 maintenance man-hours per flight hour. During May, the company demonstrator (G-HAWK/ZA101) visited the States for what BAe terms ‘hands-on familiarisation by key Navy personnel,’ and the RAF Red Arrows aerobatic team gave several displays in the US. There have also been reports that the US Navy is negotiating to lease 12 RAF Hawks on a government-to-government basis, but this is apparently not Linked directly to the VTX programme.

Product Strategy

Planning for future Hawk sales is based on a three-pronged approach, making use of the current Mk 60 series, the proposed Mk 100 series with an advanced nav-attack system, and a further Series with day/night bad weather capability, probably eventuating as a single-seater with internal cannon.

The Mk 50 series was sold to Finland, Kenya and Indonesia, and is felt. to have represented a worthwhile improvement over the RAF T1, in having introduced a five-pylon capability, drop tank provisions, better nav/comm systems, AOA indication, slim seat head-boxes for the improved view from the rear seat, and an optional brake parachute for hot/high airfields. Entering service three years after the T1, the Mk 50 series increased its maximum disposable load by 70 per cent, and maximum operating weight and range by 30 per cent.

However, to simplify the production tasks at BAe and R-R, the Mk 50 series is no longer promoted, although it is available on request to meet follow-up orders from the three existing customers.

The Mk 60 series with its Adour Mk 861 benefits from an eight per cent increase in static thrust and a 20 per cent thrust increase under typical low level combat conditions. Although the basic wing 1s unchanged, the leading edge devices have been refined, and a three-quarter flap angle (37.5 deg) has been added to optimise take-off performance at high weights. Previous tests had shown that half-flap (25 deg) produced insufficient lift, while full flap (50 deg) resulted in too much drag; the new setting was found to be a good compromise.

Regarding leading edge refinement, the RAF configuration was (BAe admits) a quick fix to achieve acceptable handling characteristics without delaying deliveries, although a significant penalty was paid in terms of maximum lift coefficient. In essence, two triangular-section breaker strips were added to the leading edge on either side, triggering premature flow separations. The aim of wing development for the export market was to get rid of these strips and thus allow the full lift potential of the wing to be exploited. As things now stand, there is only one small breaker strip. The change is worth only two or three knots off the stall speed, but it has been found to give a significant improvement 1in maximum turn rate, providing an extra ½ g with extremely good control.

A further important line of development concerns drop tanks the Hawk initially using 100 Imp gal (454 litre) tanks, each weighing 413 kg full. As a first step, the tank was stretched to
230 Imp gal (591 litres) to exploit the strength of the pylon, while retaining a full 8 g capability. Secondly, with an eye on increased ferry range, the old Hunter mild steel 230 Imp gal (104 litre) tank has shortened to 190 Imp gal (864 litres), the practical limit being set by ground clearance. In comparison with the original tank of roughly half the capacity, this was found to give very little extra drag, and to improve buffet characterist1cs in some configurations. This tank will probably be limited to around 5.5 g and thus has a useful combat capability (it is already in use on the Sea Harrier). It is currently flying on the demonstrator G-HAWK, and will go on future sales tours.

Turning to armament development, the RAF Hawk T1 has already been cleared to fire Sidewinder from the inboard pylons, and the corresponding Matra Magic is due to be cleared for the Mk 60 (presumably on the outboard pylons, with tanks inboard) during the course of this year, for at least one export customer. The Mk 60 series also has some detail cockpit improvements, stronger wheels and tyres to take maximum gross weight from 7350 kg up to 9100 kg, and an adaptive anti-skid system. When anti-skid systems were first introduced, they simply released braking pressure when the wheel locked, and resulted in reduced tyre wear, rather than reduced landing distance. Making use of modern electronics, anti-skid systems can be made far more ‘smart’, so that they can develop the optimum braking pressure for any given conditions. Such an ‘adaptive’ system is now under development for export Hawks. A further change to the undercarriage is the introduction of a low friction nose leg, originally developed to improve nosewheel centring on icy runways. The new bearing was found to enhance general ground handling (BAe has always resisted the idea of giving the Hawk nosewheel steering), hence it will be applied as standard to future export aircraft.

Entering service three years after the Mk 50, the 60-series gave worthwhile improvements in airfield performance, climb, acceleration, and turn rate. It increased disposable load by 33 per cent, maximum operating weight by 17 per cent, and maximum range by 30 per cent. Further improvements under consideration include chaff/flare dispensers, a radar warning receiver, and podded jammers. It is also possible that the Mk 60 may be fitted with a simple laser ranger and FUR, although heavier sensors would tend to take the CG too far forward, and could force the change to a single-seater.

The next major step forward, beyond the current Mk 60 series, is the Mk 100, formerly referred to as the EGA (Enhanced Ground Attack) Hawk. The company’s philosophy in developing the Mk 100 is that the Mk 60 with the big tanks provides twice the warlord/radius performance of the Hawk’s closest competitor, but that some customers will require an advanced nav-attack system. After studying the various equipment possibilities, BAe has selected the Singer-Kearfott inertial navigation system used in the F-16A, and combined this with a Smiths HUD derived from that used in the Sea Harrier. The system will also feature HOTAS (hands-on throttle and stick) operation, a digital databus, and optional laser ranging. Maintaining the three-year cycle of new models, BAe would like to see the Mk 100 enter service in 1985, and a lot of work is currently in progress at Kingston to keep this option open, should a launch customer (probably in the Middle East) sign in the near future.

Provisional data for the Hawk Mk 100 includes an empty weight of 3645 kg and a maximum take-off weight of 8340 kg. Armament options will include the TV-guided Maverick, making use of the multi-function display in the rear cockpit (that in the front cockpit replaces two of the flight instruments, but also shows checklists or a moving map, when selected). This colour MFD is currently under development jointly by Smiths and the Institute of Aviation Medicine at RAE Farnborough, the claim being that such colour displays reduce the time taken to absorb information by up to 90 per cent. Whereas Maverick is sufficiently light to be carried under the wings, Sea Eagle (the anti-shipping missile under development for the Sea Harrier and Tornado) would be carried on the centre-line pylon to avoid problems of asymmetry.

Such air-surface guided weapons would be offered in parallel with the many simpler stores already cleared for the earlier series, which include British, US and Spanish bombs, SNEB and SNORA rockets, the Thomson-Brandt BAP 100 rocket accelerated and BAT 120 retarded bombs, Matra Durandal, the Vinten VICON camera and IRLS pod, and a centre-line pod that can take either the 30 mm Aden or a 12. 7 mm machine gun for practice use. The Hawk is also cleared to tow the French SECAPEM target.

The rationale behind further development of the Hawk (i. e. beyond the Mk 100 series) is that the aircraft’s operational potential can only be exploited fully by giving it a night/all-weather capability, more firepower and a complete electronic warfare kit. The provision of an advanced radar in the nose drives the design toward a single-seater, in order to avoid the need to ballast the rear end. Placing the pilot between the two existing aircrew positions provides a good basis balance-wise, a much improved rear view, and space under the cabin floor for a pair of cannons (either 30 mm Aden or 27 mm Mauser), thus leaving the centre line free for a pylon-mounted store such as an ECM or reconnaissance pod. The centre and rear fuselage would be unchanged from the Mk 100 series, but the ‘cockpit module’ would be new. This fuselage section would include the guns, ammunition tanks, OBOGS (on-board oxygen generation system) and the nose leg mounting, which would be moved aft to provide more space for sensors in the nose. The equipment module ahead of the cockpit would be designed as a separate entity to accommodate various sensors.

The ‘Operational Hawk’ offers a remarkable warlord-radius performance. For example, in a CAP (combat air patrol) mission, it could remain on station with two AIM-9 and two cannons for four hours at 50 nm (93 km) radius. In an antishipping strike with the Sea Eagle missile, it would have a radius of up to 817 nm (1513 km). For armed reconnaissance duties, it could perform a LO-LO mission of 384 nm (712 km) radius with a centre-line pod and two air-air missiles. In close support missions, it would carry seven 454 kg bombs over a LO-LO radius of 131 nm (243 km), while for interdiction a HI-LO-HI radius of 529 nm (980 km) could be flown with four 454 kg bombs. Ferry range would be 2000 nm (3700 km).

To summarise, in the current Hawk Mk 60 series BAe is producing an outstanding trainer and ground attack aircraft, which with an advanced nav-attack system will become the Mk 100. This will have further development potential for operational use by virtue of nose-mounted sensors, probably to be associated with production in single-seat form and with internal cannon.

Reverting to the RAAF’s ‘Macchi replacement’ plans, if the prospects are examined purely in terms of the fatigue life of the MB-326H with recent structural modifications, then it is probably true to say that no new trainer is needed before 1992. On the other hand, with deliveries of the F/A-18 commencing in 1985, there may also be a plausible argument in favour of having a number of more advanced trainers in the mid-1980s as a stepping stone between the MB-326H and the F/A-18. As argued earlier, such trainers might reduce conversion time on operational aircraft, and they could also be usefully and economically employed in target towing, air combat training, and other sorties in which a fairly high performance is required.

In any such considerations, the likely effect on Australian industry must also be considered. In this respect, it is important that the chosen trainer has a credible operational capability and worthwhile development potential so that the production workload associated with regional sales might reasonably be expected to continue far beyond that on RAAF aircraft alone. In terms of the needs of both the RAAF and industry, the BAe

Hawk certainly appears to be worthy of consideration.