HAL HJT 39
| Industry | Aerospace and defense |
|---|---|
| Founded | 1940 |
| Headquarters | Bangalore , India |
| Products | Aircraft, aerospace components, defense equipment |
The HAL HJT 39, referred to as CAT (Combat Air Trainer), was an Advanced Jet Trainer (AJT) concept developed by Hindustan Aeronautics Limited (HAL) intended for service with the Indian Air Force. Introduced at Aero India in February 2005, the program unveiled a mockup of the forward fuselage and cockpit. It targeted a maiden flight within approximately three and a half years, utilizing shared airframe and engine components with the HAL HJT-36 Sitara, and featuring avionics systems akin to those found on both the HJT-36 and HAL Tejas.
Design
The CAT was envisioned as a twin-engine, transonic "Lead in Fighter Trainer" (LIFT) aircraft equipped with substantial ground attack abilities, designed to reach speeds up to 1,000 km/h.
Its avionics suite comprised Multi Function Displays (MFD) for tactical navigation, a Radar Warning Receiver (RWR), and an indigenous Head-Up Display (HUD) along with an Up Front Control Panel (UFCP) developed jointly by CSIO and BEL, similar to those implemented on the LCA. The HUD was intended to present navigation information and weapon targeting data.
To ensure operational reliability, the aircraft incorporated redundancy through standby instruments, a Fly-by-Wire (FBW) system featuring two digital channels plus one analog engine channel, hands-on-throttle-and-stick (HOTAS) controls, an Inertial Navigation System (INS) integrated with GPS, a flight control computer, and a display processor. The avionics were designed to conform to the 32-bit dual MIL-STD-1553B Bus standard. Engine management was to be enhanced by Full Authority Digital Engine Control (FADEC). Additional cockpit systems included automatic cabin pressure and temperature regulation, zero-zero ejection seats, and an emergency crew escape mechanism. While radar installation was optional, there were intentions to develop a new radar system.
Airframe
The design featured a moderately swept low wing without wing-body blending or root strakes, accompanied by a prominent vertical stabilizer. The low sweep angle of the wings was selected to improve low-speed handling characteristics, a vital aspect for training aircraft. The wing design included a clean leading edge combined with high-lift trailing-edge devices to optimize runway performance. The airframe construction was entirely composite.
Cockpit
The CAT’s cockpit utilized tandem seating with considerable stagger, placing the student pilot in front. This layout provided excellent visibility for both crew members, enabling instructors to monitor trainee activity effectively. It incorporated an advanced glass cockpit environment equipped with a Head-Up Display (HUD), traditional head-down instruments, and controls for weapon aiming. Ergonomic considerations were prioritized to boost pilot effectiveness.
Engine
Intended for ground attack missions, the aircraft was powered by two NPO Saturn AL-55 turbofan engines, each generating 2,200 kg of thrust—an increase compared to the single-engine 1,800 kg thrust variant used on the HJT-36 intermediate trainer.
Armament
The CAT was designed with five hardpoints capable of carrying training ordnance such as practice bombs, rockets, missiles, along with a centrally mounted fuselage gun. Its maximum takeoff weight carrying external stores was estimated at 9,500 kg. The platform also aimed to support virtual training features including radar simulation and computerized assistance tools. Optional systems included an On-Board Oxygen Generation System (OBOGS).
HAL planned to deliver prototypes within 39 months following government approval at an estimated cost of Rs 750 crore (2005). Nevertheless, the project appears to have been discontinued without further developments; instead, India acquired BAE Systems Hawk 132 AJTs for its training needs.