Journal of Aeronautical History Paper No. 2013/01 The HAWK Story Harry Fraser-Mitchell Formerly British Aerospace Ltd FOREWORD On 10th October 2011, a joint presentation on the Design, Development and Future Prospects for the HSA / BAE “Hawk” aircraft was made to an audience in the Lecture Theatre of the Royal Aeronautical Society, under the auspices of the Historical Group. The speakers were the author, dealing with Design and Development, Mr C. Roberts, Project Pilot, on the T-45 for the US Navy, and Dr A. Bradley, the current Chief Engineer, Hawk, on the Present and Future Prospects. With only a total of just over an hour for the whole presentation, it was impossible for any of the speakers to go into any detail, and the Author felt that it was desirable for the whole story to be written up as a paper, in three parts as presented by the speakers above. He has attempted to do this himself, but relying heavily on data provided by the other speakers and other sources for Parts 2 and 3. It is to be hoped that a future issue might encompass further information from the other contributors to “The Hawk Story”. This paper consists of three parts. PART 1 Starting from the initial investigations by HSA in 1968, the evolution of the HS 1182 project is shown, eventually becoming the Hawk T.Mk.1. The development of the export and strike versions, series 50, 60, 100 and 200 are covered. The U.S. Navy T-45A is only briefly mentioned here – it is covered more fully in Part 2. The evolution of the Rolls-Royce Turbomeca RT 172 Adour is outlined with the help of RR- TM documentation. The Author’s opinions as to why the Hawk has been so successful are given towards the end of this part. PART 2 This covers the adaptation and development of the basic Hawk airframe for the use of the U.S. Navy for training and carrier qualifications, in collaboration with the McDonnell Douglas Corporation, St Louis (originally with Douglas Aircraft Co, Long Beach), both now incorporated into The Boeing Aircraft Corporation. 1 Journal of Aeronautical History Paper No. 2013/01 The competition, initial developments and the critical design drivers of the modifications eventually agreed are all covered in some detail. Brief mention is made of the lawsuit brought by the US Navy to determine who should be responsible for the extra costs incurred by the need for extra modifications, deemed necessary to meet the requirements of the Specification. PART 3 Since 1995, the approximate time covered by Part 1, the Hawk design has been greatly advanced in many respects, resulting in a large and healthy sales ledger, with new, updated systems and powerplant improvements. Some details of these developments are given in this Part, relying on data provided by the original Speaker, and other published sources. This is not the end of the Hawk story, as further avenues are being actively explored. 2 Journal of Aeronautical History Paper No. 2013/01 PART 1 DESIGN AND DEVELOPMENT SUMMARY Starting in 1968 with early feasibility studies into what the RAF might need to replace the aircraft in their fast jet pilot training programme, the HS 1182 aircraft was defined. When the Air Staff Target became known, further refinement took place, and the resulting design was selected. Some details of the development of the aircraft’s aerodynamics, structure and systems are described and a few of the problems that arose in the flight testing and their subsequent solutions are briefly dealt with. It was always intended that the Hawk should have an appeal as a light strike aircraft for the export market and the development of the Mk.50, 60, and 100 series is covered as well as the single seat attack version, the Mk.200 series. One section deals with the parallel development of the Rolls-Royce Adour, the engine chosen for the aircraft. 1. INITIAL STUDIES 1.1 Establishment of the requirements In the mid-Sixties, the Air Staff was already thinking of updating the RAF pilot training programme, and in 1964 issued Air Staff Target (AST) 362 for a Gnat replacement. It called for a twin-engine, two seat advanced trainer capable of dash speeds of up to 1.5 Mach number, something like the USAF T-38 aircraft. International collaboration was the ‘flavour of the month’ and the Breguet 121 airframe seemed to be a suitable basis for collaborative study. However, as it evolved, it became clear that it was going to be an expensive trainer, with twin reheated engines, and the drag was such that it even required partial reheat in the approach. But it did look like a candidate for an attack aircraft – as it eventually became, as the SEPECAT Jaguar, the majority of which were single-seaters. This left the RAF trainer programme unfulfilled and in the late sixties it was becoming apparent that the aircraft then used for the Royal Air Force’s fast jet pilot training were increasingly expensive to fly and maintain, and would need to be replaced in the fairly near future. In particular, the Folland Gnat Trainer and the Hawker Hunter two-seater were well into the second half of their service lives. Thus in 1968, on the basis of discussions by Gordon Hodson with Gnat operators, the Future Projects Office of the Kingston-on-Thames works of Hawker Siddeley Aviation started to investigate the requirements for a suitable replacement aircraft, preferably to combine the duties of advanced flying and weapon training. 3 Journal of Aeronautical History Paper No. 2013/01 K. Gordon Hodson, then in the Kingston office, had seen RAF service and had also been closely associated with the Gnat at Follands. Backed by the Assistant Chief Engineer, R. B. Marsh, he embarked on a series of liaison visits to RAF Training Establishments, with a view to finding out what they would ideally like to see in a new trainer aircraft, and the duties it should perform. He found that features that were highly desired were (not in any order of priority) as follows: Low acquisition and life cycle costs Low fuel consumption and a wide speed range up to high subsonic. High reliability and hence high utilisation and low maintenance cost. High structural integrity and from the point of view of the Company: Low risk. Ease of manufacture Simple design. Development potential. Export considerations were crucial to cover costs. As a result of the investigations, an internal brief specification was drawn up (see Section 1.7), and the Project Office went to work producing a series of feasibility studies, covering a wide spectrum of types using single and twin engines, tandem and side-by-side seating, straight and swept wings, low, mid or shoulder mounted. A few of these are illustrated in Figures 1 to 8. These are only a selection of perhaps 20 layouts that were studied and assessed. The table below summarises the features of the illustrated configurations. U/C Figure Type Wing position Cockpit Intake Powerplant Mounting 1 1182-1 Unswept, high Tandem Wing root Fuselage 1 x Adour 2 1182-2 Unswept, low Tandem High Wing 1 x Adour 3 1182-4 Unswept, mid Tandem Wing root Wing 1 x Adour 4 1182-7 Swept, high Tandem Low Fuselage 1 x Adour 5 1182-8 Swept, low Side / Side High Wing 1 x Adour 6 1182 - Swept, low Tandem Pods Wing 2 x BS 153/ Larzac 7 1182 - Swept, low Side / Side Pods Wing 2 x BS 153/ Larzac 8 1182 - Swept, high Side / Side Wing root Fuselage 2 x BS 153/ Larzac Notes: All had fixed tailplane with elevators and balanced manual controls. Unswept wings were rejected as being unlikely to exceed M = 0.8 4 Journal of Aeronautical History Paper No. 2013/01 Notes: The tandem cockpit was judged to have better vision and lower frontal area, and hence cont. less drag, than the side-by-side cockpit The high wing position with a low tail was thought to be more favourable at high speed The low wing position was potentially easier to service and equip with stores A fuselage-mounted undercarriage (necessary with a high wing) gave an undesirably narrow track The low intake had a potential ingestion problem, whereas the high one should be clear Twin engines were awkward to install for low drag. There was potential for high speed problems due to interference between podded engines, and a high tail would be necessary. The conclusion reached was to have a swept wing, either high or low (to be investigated), a tandem cockpit, high intake and a single engine. At the same time, studies were made of methods of cost estimation based on past experience – these were fed back to the design people to guide them in offering schemes having significant savings in cost. Over the next two years, all these studies were refined and assessed. One can recall one famous and lengthy meeting in the Project Office, chaired by the Chief Future Projects Engineer, J. E. Allen, when some 17 competing designs, each with its own advocates, were whittled down to one, plus a few variants. This was dubbed the HS 1182 (with later variants 1182 A, 1182 V and 1182 AJ). Figure 1 HS 1182 – 1 Unswept high wing, wing root intake, fuselage mounted u/c, tandem cockpit, 1 x Adour engine 5 Journal of Aeronautical History Paper No. 2013/01 Figure 2 HS 1182-2 Unswept low wing, high intakes, wing mounted u/c, tandem cockpit, 1 x Adour engine Figure 3 HS 1182 – 4 Unswept mid wing, wing root intakes, wing mounted u/c, tandem cockpit, 1 x Adour engine. 6 Journal of Aeronautical History Paper No. 2013/01 Figure 4 HS 1182 -7 Swept high wing, low intake, fuselage mounted u/c, tandem cockpit, 1 x Adour engine Figure 5 HS 1182 – 8 Swept low wing, high intakes, inboard mounted u/c, side-by-side cockpit, 1 x Adour engine 7 Journal of Aeronautical History Paper No. 2013/01 Figure 6 HS 1182 Swept low wing, podded engines, inboard mounted u/c, tandem cockpit, 2 x BS 153 or Larzac Figure 7 HS 1182 Swept low wing, podded engines, inboard u/c, side-by-side cockpit, 2 x BS 153 engines. 8 Journal of Aeronautical History Paper No. 2013/01 Figure 8 HS 1182 – 7 Swept high wing, underwing engines, inboard u/c, side-by-side cockpit, 2 x BS 153 engines 1.2 Choice of engines. Different types of engine were also investigated, as shown in Tables 1 and 2. These were appropriate to both single and twin installations. Considering the twins first, it was observed that the J-85 had relatively high fuel consumption. The JT-15 was much better in this respect, but because it had a higher by-pass ratio, its performance suffered at height and speed (Table 2). The Larzac was good all round but was committed to the Alpha Jet and there was some doubt of its availability and of its support from a relatively small company. The argument for the choice of a single engine over a twin was well exercised. For twins, it was said that there must be a better degree of safety in that an engine failure was unlikely to be critical. Against this it was argued that the reliability of jet engines, particularly for those well established, was very good anyway. Furthermore, more training would be required to introduce a student to coping with the deliberate shutting down of one engine to simulate failure. Wryly, some multi-engine training pilots remarked that it was not unknown for students to shut down the good engine when faced with the situation, often with disastrous results. 9 Journal of Aeronautical History Paper No. 2013/01 Table 1 Comparison of engines at Maximum Take-off Rating, Sea Level, ISA, Static Engine Type Thrust SFC Fuel Flow Air Mass Net Dry (lb) (lb/hr/lb) (lb/hr) Flow Weight (lb/sec) (lb) Twin Engines GE 85 – 13 5440 1.03 5603 88 1140 JT 15 D – 3 5760 0.525 3025 187 1258 Larzac – 04 5940 0.705 4190 122 1170 Single Engines Avon Mk.121/122 7575 0.98 7420 123 2502 Orpheus 101 4400 1.061 4670 83 920 RB 199 8394 0.603 5062 156 1160 M 45 H 7760 0.451 3500 233 1500 Viper 600 4000 0.97 3880 58 825 Viper 21 F 4800 0.758 3640 108 925 Adour RT 172-06 5000 0.691 3455 93 1162 Walter Titan/A1 – 25 4000 0.62 2480 Table 2 Comparison of engines at Maximum Continuous Rating, 30000ft, ISA, 0.8 Mach Net Thrust SFC Fuel Flow lb lb/hr/lb lb/hr Twin Engines GE 85 – 13 2160 1.285 2775 JT 15 D – 3 1741 0.846 1472 Larzac – 04 2000 0.973 1946 Single Engines Avon Mk.121/122 3200 1.19 3810 Orpheus 101 1550 1.315 2040 RB 199 2954 0.835 2473 M 45 H 2240 0.77 1722 Viper 600 1425 1.155 1642 Viper 21F n/a n/a n/a Adour RT 172 – 06 1770 0.942 1667 Walter Titan/A1 – 25 n/a n/a n/a 10