Tejas UCAV? Here’s What HAL Needs To Do

A new effort to unman India’s LCA Tejas fighter platform to spin off a UCAV has been revealed in a fresh report in The Economic Times, reviving projections made a decade ago by the Defence Research & Development Organisation (DRDO). HAL, which has ambitious plans to enter the unmanned systems space with both partnerships and new in-house development projects, has been looking at the Tejas for years, a platform it is of course deeply familiar with. The proposition is however much more complex than both HAL and DRDO will immediately let on.

The conversion of a full-fledged fighter system into an unmanned platform is an onerous task. Apart from the easier material changes, including removal of non-essential items (actually not a simple task on the Tejas, as maintainability roadblocks have shown), the conversion of the Tejas — like Boeing’s conversion of the F-16 to the QF-16 — will involve major changes to the flight control system (FCS). The conversion will also involve the installation of a kill switch/flight termination system to make sure ground control can destroy the aircraft in flight and the addition of telemetry sensors and systems. But the centrepiece of the conversion will be the Tejas FCS.

Official literature on the Tejas FCS describes it as a ‘quadruplex digital fly-by-wire flight control system to ease handling by the pilot, employing a powerful digital flight control computer (DFCC) comprising four computing channels, each with its own independent power supply and all housed in a single LRU’. It further goes on to add:

The DFCC receives signals from a variety of sensors and pilot control stick inputs, and processes these through the appropriate channels to excite and control the elevons, rudder and leading edge slat hydraulic actuators. The DFCC channels are built around 32-bit microprocessors and use a subset of the Ada programming language for software implementation. The computer interfaces with pilot display elements like the MFDs through MIL-STD-1553B multiplex avionics data buses and RS-422 serial links.

Tejas is intentionally made longitudinally unstable to enhance manoeuverability. The Control laws (CLAW) recover Stability and provide good Handling Qualities to the Pilot. They also provide invariant response with respect to variation in aerodynamics, fuel etc. and facilitate robust performance. The CLAW is carefree and ensures that various aircraft parameters are limited automatically. This enables the pilot to fly the mission without worrying about exceedance of parameters beyond a safe limit.

The autopilot provides pilot relief functions. This helps the pilot to do more head down activities (especially mission critical activities) without being concerned about the aircraft departing from its flight path. The autopilot is also equipped with advanced features like auto level (which helps the pilot recover the aircraft if he gets disoriented and also during night flying), safe altitude recovery (which automatically pulls up the aircraft if it comes too close to the ground) and navigation modes (which steer the aircraft automatically along a pre-determined flight path).

HAL’s research will therefore centre around autonomous flight functions, the combat management system and the mission computer. As the LCA Tejas goes through the motions of proving itself across the gamut of precision and other weapons, HAL’s logic is that a proven flying platform makes sense as a non-stealth weapons delivery platform. The utility (and viability) of a non-stealth platform for weapons delivery by a country like India remains one of many questions. India, as Livefist has reported, is developing the Ghatak stealth UCAV for precisely the same mission, but with a specific emphasis on stealth qualities and therefore, missions into enemy airspace.

Economics and survivability issues aside, the research HAL is conducting on the familiar Tejas platform could have deep experimental value going forward. In a best case scenario, it gives HAL fundamental experience in flight control system architecture for unmanned/autonomous systems in combat envelopes — something very far from what it has even thought of attempting so far.  Skeptics would argue that HAL has chosen to do the most difficult task first, though others suggest that this is low-risk option for very valuable research and will not require additional resources, especially since this is technology no country will share without very expensive benefits. Of course, if things click, a possible target drone version of the Tejas for air combat training (like the QF-16) is a possibility.

HAL is also scouting an international partner to spin off an unmanned version of the Chetak helicopter.