DSTO-Sharpening the Edge

F/A-18 Full Scale Fatigue Testing

The Aeronautical Research Laboratory is currently involved in a joint programme with Canada to gain vital information on the airframe life of the Hornet. The collaborative programme, known as the International Follow-On Structural Test Programme (IFOSTP), is designed to yield information which will enable efficient management decisions on airframe usage to be taken and will provide information onwhere structural fatigue is likely to occur.

Fatigue testing on Hornet airframes has been undertaken in the United States by both the US Navy and McDonnell Douglas, however the IFOSTP test programme is unique in that it’s designed to test effects of usage by both Australia and Canada who use the aircraft in similar, land based, roles, different to that of the USN. Australia is responsible for testing the aft fuselage and tail. This is a particularly complex operation, particulary since the test programme involves testing the effects of intense vortices which cause intense vibration on the fins, caused by high angles of attack, and high G maneuver loadings simultaneously.

A demonstration test rig has already been set up and used on a fuselage on loan from the US Navy, while full scale testing using a more complex test apparatus on a brand new fuselage purchased by the RAAF from Northrop will begin at the end of 1993.

Allison T56 Smoke Reduction Modifications

The Aeronautical Research Laboratory has been able to achieve an impressive 80% reduction in smoke emissions from the Allison T56 turboprop. The T56 is traditionally known as a smokey engine and smoke reduction, particularly for engines fitted to the P-3C Orion, was seen as essential by the RAAF to reduce its visibility and therefore its vulnerability. (Other aircraft which feature the T56 include the C-130 and the E-2).

ARL was initially requested by the RAAF to reduce smoke emissions from the T56 engine of the P-3 Orion in October 1984. This was seen as of importance because of the high visibility of smoke trails to submarines. Water tunnel testing of the combus tion chamber of the T56,where the smoke originates, was followed by modifications to improve mixing within the combuster, which yielded smoke reductions in the order of 80%, twice that specified by the RAAF. Other advantages have also arisen as a result of the modifications, most significantly a cut in fuel burn of one per cent, decreases in infrared signature and a reduction in the amount of carbon monoxide produced.

Transferring this technology to Australian industry is seen as a major priority, considering the importance of this modification and the widespread use of the T56 worldwide. To take advantage of the latent demand for the modification of the T56, (there are more than 8,000 fitted to Hercules and Orions worldwide) a joint company was setup by the DSTO with Ansett owned Pacific Aviation, called Defence Technologies Australia. Much of the success of this programme relies on the engine manufacturer, Allison, giving the modified combustion chamber an official part number, due later this year under a business agreement recently signed with Allison, if the modification can be validated. Needless to say, the long term commercial benefits of the modification will be quite substantial.

Currently in Australia 14 RAAF T56 engines have been modified and over 4,000 flying hours have been logged with the modification.

Austower Air Traffic Control Simulator

Austower has been developed for the RAAF as an Air Traffic Control simulator, designed to train and give controllers experience in a very large variety of scenarios.

The Austower simulator involves projecting the images of an airfield, actual RAAF airfields or a generic model, onto the walls of a full scale model of a control tower. Aircraft then take off, land and taxi just as at a real ATC tower. The fully interactive simulator can provide experience in directing aircraft around and near the airfield. As well as normal operating procedures, variables such as changing weather, differing light conditions and emergencies such as engine failure on takeoff are incorporated in the programme. Up to ten independent ground and air movements can take place simultaneously.

Training in Air Traffic Control procedures has largely taken place ‘on the job’ as controllers slowly built up experience in dealing with different situations which arise. Austower, a fully operational version of which will come on line at the RAAF School of Air Traffic Control at East Sale this year, will enable the controller to gain experience in dealing with a full range of scenarios in a much shorter space of time.

Air-to-Air Combat Modelling

ARL scientists have developed a whole system simulation designed to improve the RAAF’s capability in counter air defense by simulating combat between teams of opposing aircraft.

Air-to-air combat modelling is able to simulate various situations involving the airforces’ reaction to arange of threats including air-to-air and air-to-ground hostile aircraft. The mathematical model enables the effects of systems changes and technological advances on the outcome of combat to be studied. The model considers the effects of various degrees of outside control and warning such as AWACS and ground control, information exchanges, the effects of different tactics, aircraft types and capabilities, missile characteristics and performance envelopes, jamming and counter jamming on the course of the engagement. It will provide the RAAF with a means for evaluating the effectiveness of systems which are presently in service or which may be under consideration for purchase by the ADF.

Bonded Composite Repair Technology

The Aeronautical Research Laboratory is a recognised world leader in the field of bonded composite repair technology. In line with the DSTO’s role of providing support in the operation of defence assets, the ARL has been called upon many times in recent years to provide suitable repairs to stress related damage in various aircraft systems.

Pioneered in the 1970s, bonded composite repairs involve using high strength composites bonded to areas which have been subjected to high stress and are in need of repairs. Known as crack patching, significant repairs have been executed on RAAF aircraft over the years. Fin and wings of the Mirage, Macchi landing gear, wing pivot fittings of the F-111 and wing cracks in the C-130 have all been repaired using boron/epoxy, a stronger yet lighter composite material than conventional aluminium. Projected long term savings through the use of crack patching totals tens of millions of dollars for these projects.

There is also an enormous potential for civil applications of this technology and demonstrator work has been carried out including fatigue testing and simulated fuselage lap joint repairs on a Qantas 747, keel beam repairs on a 767 and simulated lap seam region repairs on a 727.

Other aviation related research is carried out by the Surveillance Research Laboratory in South Australia. Two major projects currently under development are a synthetic aperture radar and a radar target generator.

Australian Synthetic Aperture Radar

Synthetic Aperture Radar (SAR) is a relatively recent development which enables terrain to be mapped by radar, free of hindrances such as weather. Numerous synthetic aperture radars are in use around the world, epitomised by the US’s Joint STARS, while modern combat aircraft such as the F/A-18 feature conventional radar which possess a limited SAR capability. However, all high resolution systems, particularly JSTARS are of exceptionally high cost and the DSTO at Salisbury in South Australia is in the process of developing a low cost SAR.

Conventional radar is only able to create images of very poor detail, largely because the aperture of the receiving antenna is very narrow when compared to the size of a microwave wavelength. The human eye which is able to produce images of good detail, for example, is able to receive many more light waves across its aperture due to the small nature of light waves. Synthetic Aperture Radar is able to increase the information gathering aperture of the radar synthetically, ie by attaching the radar to an aircraft, the aperture is increased artificially by the movement of the aircraft in a straight line. With the increased aperture comes increased image definition.

Amajor project undertaken by the DSTO is the development of a low cost SAR called AuSAR which is hoped to be tested on an ARDU Dakota within the next few years. An operational AuSAR will be able to be deployed from aircraft such as the Nomad or King Air, depending on underfuselage clearance. Application of SAR is potentially enormous, as the geographic charting and reconnaissance information it can yield the defence forces is essential in providing intelligence. Civil applications are also of great importance, as SAR will be able to be used in mineral exploration and topographic mapping, and has maritime surveillance uses such as customs, drug enforcement and fisheries patrols.

Radar Target Generator

To many, radar target generation is very much an unglamorous and virtually unknown area of defence science, however it is of importance as it enables a defenceforce to evaluateand test radar equipment.

The DSTO developed Radar Target Generator enables the RAAF to evaluate and test the APG-65 multimode radar of the Hornet without actually subjecting the aircraft to a simulated combat environment. Instead, a radar target generator subjects the radar to a realistic combat environment by simulation, rather than incurring the costs of flying an aircraft in realistic conditions. The Radar Environment Generator, as marketed by licensee MRad, is a self contained ground based system which creates signals which are received by the radar, such as targets, ground clutter and electronic countermeasures and injects radar return signals directly into the radar.

The substantial cost benefits of this system has attracted much international curiosity with Saudi Arabia, Israel, Korea, France, the UK, Singapore and the United States being among the nations which have expressed interest in this system.

A number of other aviation related projects are under development by the DSTO, most notably LADS, the Laser Airborne Depth Sounder, a project undertaken by the DSTO for the Navy (refer p. 61 Apr 92 AA). This involves the use of a laser mounted under a Fokker F27 to determine ocean depth. One other important project is Nulka, a missile decoyfor naval vessels. Aship under missile attack will launch Nulka, a hovering rocket which will simulate the movement of a surface vessel, while the ship under attack can escape the inbound sea skimmer. Details of this project are scarce due to the extreme sensitivity of the project, as it is in partnership with the US Navy, however, all is reported to be well with the project.