In the Drone Zone

The United Arab Emirates Air Force and Air Defence has been an early and enthusiastic adaptor of UAV technology and the UAE has mounted a sustained effort to establish indigenous design, development and production capabilities. ADCOM Systems is at the forefront of these efforts. Jon Lake reports.

The UAE’s armed forces have operated the South African Denel Seeker fixed-wing UAV since the early 1990s and opened a UAV Research and Technology Centre in Abu Dhabi in 2004, with the Gulf Aircraft Maintenance Company (Gamco) providing some facilities and expertise.

The centre oversaw the introduction of two new rotary-wing UAVs – the Austrian Schiebel Camcopter S-100 (known locally as the Al Sber), and the Swedish Cybaero Apid 55 – as well as a common ground station developed in association with South Korea’s Uconsystem.

The first Al Sber was delivered in October 2005 and 60 were ordered, with options on 20 more. The UAE has deployed the type to quietly support NATO operations in Afghanistan, according to the UK’s chief of the air staff, Air Marshal Sir Stephen Dalton, speaking at the Dubai Air Chiefs Conference in November 2009.

The nascent UAV programme enjoyed heavyweight support, not least from Crown Prince General Sheikh Mohammed Bin Zayed Al-Nahyan, deputy supreme commander of the armed forces, who publicly stated: “UAVs are an integral part of any efficient combat force,” highlighting their importance for homeland security, early-warning, surveillance, data gathering and targeting, and underlining their importance for a small wealthy UAE sandwiched between larger and militarily powerful neighbours.

Indigenous unmanned vehicle development in the UAE started even before the air force began testing the Seeker in 1992. That was the year that the Mussafah-based ADCOM Group established its advanced target system division.

Since then, ADCOM has developed a succession of highly successful unmanned target drones, winning valuable export orders and building the foundations for a family of operational UAVs.

The most successful product in ADCOM’s range of targets is the SAT-400, a fully-programmable 85-kg drone with a 2.75 metre wingspan, used by the armed forces of the UAE and Canada. The drone has a flying body configuration, with an aft-mounted wing mounting endplate fins, and with a pusher propeller. The drone has a two-hour endurance, can reach speeds of up to 420km/h and can carry a range of payloads, including flares, smoke generators or radar reflectors/augmenters.

The turbine-powered Yabhon-HM is of broadly similar configuration to the SAT-400, but enjoys superior performance, reaching up to 550km/h, while the twin-turbine Yabhon-HMD is 20 per cent larger, has longer endurance than the HM (up to 72 minutes), can exceed 650km/h, and carries miss distance indicator equipment. The HMD is capable of low altitude, sea-skimming flight and of making simulated diving attacks, allowing it to replicate a wide range of threats, including tactical ballistic missile threats such as the ‘Scud’ surface-to-surface missile.

With its extensive experience of unmanned target drones, ADCOM has naturally turned its attention to the design and development of more advanced UAVs for operational roles, and has produced a staggering array of designs, some of which have been revealed at successive trades shows amid great ceremony, only to subsequently disappear. Others seem to have led to longer-term development programmes.

Confusingly, many of these use the same Yabhon name, with different designation suffixes.

At the Dubai air show in November 2005, for example, ADCOM unveiled an experimental medium-altitude, long-endurance (MALE) UAV called the Yabhon Excellency, with a 16 metre (52ft) wingspan and a 500-kg payload. The company announced that it was intending to fly a prototype in April 2006, though nothing further was heard of the programme. At the same event, ADCOM also revealed the Yabhon – VTOL, a tactical extended endurance UAV with coaxial rotors, to be powered by a Rotax 912ULS engine. This was also expected to fly in 2006, and also disappeared.

ADCOM’s more modest, less ambitious UAV projects seem to have made greater progress. The 3.28 metre wingspan Yabhon-H began life as a target drone, in broadly the same category as the SAT-400, but was soon adapted for reconnaissance use with the addition of a nose-mounted electro optical sensor turret. Powered by a single piston engine driving a pusher propeller, the Yabhon-H has a new aerodynamic lay-out, with canard foreplanes and a high aspect-ratio double delta wing with highly efficient laminar flow airfoils optimized for long-range/extended endurance cruise. The airframe was built from fibre-epoxy material completely vacuum-bagged for maximum strength.

The Yabhon-H boasts an eight-hour endurance and excellent ‘hands off’ stability and good turbulence resistance, together with docile stalling characteristics. The aircraft is designed to take off using a simple launcher, and then to be recovered by parachute.

The Yabhon-M is a scaled up  UAV using a broadly similar aerodynamic configuration, with a 5.7 metre span wing, and able to carry a 30-kg payload, with thermal imagers, EO and IR sensors, or even a Laser Designator & Range Finder, as payload options.

The aircraft has a UHF and 2.4GHz line-of-sight (LOS) video/data link and is claimed to have a 12-hour endurance (30 hours according to some sources), and a maximum speed of 240 km/h. The vehicle still has an integral emergency recovery parachute system, but is primarily intended to take off and land on its own retractable tricycle landing gear. The aircraft is controlled via an ADCOM-developed integrated digital fly-by-wire flight control system, and features a laser terrain avoidance system.

The Yabhon-R could be considered as the third and largest member in a family of UAVs with the Yabhon-M and Yabhon-H. It shares the same basic configuration as the others but has a 6.56 metre span, a 50-kg payload, and a claimed 30-hour endurance. Like the Yabhon-M, the R has a retractable tricycle undercarriage, and is intended to be operated from prepared strips. Payloads could include a synthetic-aperture radar, and a commercial Ku-band satellite link.

Classed as a MALE UAV, the Yabhon-R is optimized for real-time day and night reconnaissance and surveillance, search-and-rescue, border surveillance and patrol and the monitoring of remote areas. The Yabhon-R is built under licence in Malaysia by Unmanned Systems Technology (UST) Sdn Bhd, a subsidiary of Composite Technology Research Malaysia, as the Yabhon Aludra.

ADCOM’s Advanced Targeting Systems (ATS) division has made great efforts to expand the scope of its activities beyond the mere production of unmanned vehicles, and has developed and marketed launcher systems (including a highly-portable pneumatic launcher) and UAV control systems.

The ADCOM-3D flying control unit (FCU) makes use of the latest digital processing techniques and can provide monitoring, stabilisation and control of the UAV’s heading, altitude and angular movements using a strap-down inertial measurement unit with GPS and three-axis magnetometer input, and with measurement of both static and dynamic pressure.

Flight data is recorded and the system provides comprehensive fault identification and an automatic navigation capability, and pre-programmed flight plans can be changed at any stage of the flight.

The system provides fail-safe functionality in the event of any uplink interruption, and an automatic recovery function, with automatic guidance to a pre-set landing point in the event of an emergency. Normally, the UAV would take-off and land automatically, using GPS and an optional laser altimeter.

But the ADCOM-3D FCU also provides control of the UAV’s sensor and system payloads, controlling up to 16 payloads, including thermal compensation for EO/IR sensors.

But ADCOM’s core business remains the development of UAV and target drone platforms. ADCOM moved away from the canard configuration used by the Yabhon-H, -M and -R, and embraced a more conventional layout for subsequent reconnaissance UAVs.

The piston-engined Yabhon RX-6 tactical UAV had a conventional fuselage and high aspect ratio six-metre (19.7ft) wing, and had a horizontal stabilizer carried on twin tailbooms. The aircraft had a glider-type single mainwheel mounted in the belly. The new configuration was adopted in order to give improved controllability at high altitude. A prototype first flew in September 2006 and formed the basis of a Yabhon RX-18 MALE derivative, which was said to be under development in 2005, with a 1.2-1.3 tonne MTOW and a 16 metre (later 18 metre) wingspan.

The currently-offered Yabhon RX is of similar configuration, but with a 9.68m wing and a 60-kg payload and a claimed endurance of 42 hours. Such endurance would require the aircraft to soar like a glider, with the engine shut down, and many doubt that this is feasible, let alone practical under operational conditions or with an operational task to fulfil.

A similar concept of operations underpins ADCOM’s new Smart Eye high-altitude, long-endurance, or HALE, UAVs, which are intended to offer an alternative to UAVs like the Predator, and which will be described in detail in the next issue of Arabian Aerospace.