HAL Intermediate Jet Trainer HJT-36

Introduction.

Aviation that brought about an unprecedented revolution during the last century is just completing its first hundred years in 2003. Milestones in Aviation History have filled volumes. The first flight of a newly developed aircraft brings a great sense of achievement to every aircraft designer and manufacturer, besides deep emotional sentiments. 7th March 2003 was a red letter day for Hindustan Aeronautics Ltd (HAL), for it was on that day that the IJT carried out its first flight. Sqn Ldr Baldev Singh (Retd), Chief Test Pilot (Fixed Wing (FW)) of HAL took up the IJT on its maiden flight, which lasted for about 20 minutes. The flight was reported to be flawless.

It is heartening to note that the IJT flew in less than four years after commencing development work. The project was sanctioned and given a go ahead in July 1999. It speaks volumes of the capability of HAL (always underrated and understated). The most unique feature of IJT programme was that it was launched without fanfare or making tall claims that are a regular feature of other R&D organisations. Although HAL operated on a low key, the precision and efficiency with which the project was managed is obvious. IJT was rolled out in 18 months after metal cutting and flew during the 20th month.

IJT to Replace Kirans.

HAL made HJT-16, Kiran subsonic jet trainer that first flew in 1964 and inducted into the IAF in 1973, has done yeomen service. Flight Cadets after completing their initial flying training stage on the piston engined HPT-32 aircraft, do the next phase of “intermediate” training on the Kiran and Iskra (Polish origin) aircraft types. Kiran aircraft variants are Mk I, Mk IA and Mk II and the fleet has flown over 0.75 million flying hours during the last three decades. Kiran has an excellent track record with one of the lowest accident rates among the contemporary aircraft in the world. A suitable aircraft to replace Kirans was an inescapable necessity, as the fleet was nearing its fatigue life. An aircraft with state-of-the-art features to enable easy transition to modern aircraft including the Advanced Jet Trainer (AJT) was desirable, as training requirements would be perennial.

HAL took a pro-active role and made proposals to Air Headquarters (Air HQ) about the IJT, being very certain that it was well within its design capability and resources. The proposals were followed up with the concept mock-up. IAF and HAL got together and finalised the Air Staff Requirements (ASR). A quick decision was taken to launch the IJT project and sanctions were given in mid 1999, setting a stringent target for the first flight and certification. Thus the work on HJT-36 (IJT) project (successor to HJT-16-Kiran jet trainers) commenced full steam from July 1999.

Design Initiatives.

In order to meet the stringent timeframe, it was decided to carry out the detail design through advanced Computer Aided Design Techniques, with adequate hardware and software support. For the first time in HAL and possibly in India, aircraft design was carried out in 3D modelling. The Numerical Master Geometry (NMG) was finalised as a first step. Immediately, the NMG was made available to various groups like, aerodynamics, structural design and analysis, systems and tool engineering, enabling concurrent engineering. Thus the fabrication of wind tunnel model, design of major frames, layout of systems were all carried out concurrently.

All the details were captured into a central database, enabling the sequence of sub-assembly, major assembly and equipping to be worked out. The layout of pipes, control rods and looms was easy, as the earlier time consuming method of soft template could be done away with. Assembly teams found that the parts fitted very well and did not require much of suiting on assembly. Most importantly there was no physical movement of drawings, as they were on line and net worked.

Majority of the system components had been taken off-the-shelf. An innovative approach for system design made it possible to integrate reliable components from different programmes to minimise risk and cost. The layout of systems also caters for ease of maintenance. At this stage, use of composites has not been contemplated, but may be considered, if required, at a later stage of development.

Verification. The aerodynamic configuration was verified through wind tunnel testing. A 1:8 scale model was used in the HAL low speed wind tunnel and a 1:15 scale used in National Aerospace Laboratory’s (NAL) high speed wind tunnel. The results validated the design assumptions. The intake geometry was verified through computational fluid dynamics techniques. A 1:4.781 scale model was tested in ONERA wind tunnel facility in France and the intake engine compatibility established. Spin model tests are planned to be carried out in the vertical wind tunnel of TsAGI, Russia.

All the design drawing information was verified by standard checking procedures before release. The structural components such as wing, vertical tail, horizontal tail and the control surfaces were successfully tested up to limit loads. Landing gears were subjected to drop and strength tests. The undercarriage jacks and brakes built in-house were subjected to qualification and endurance tests.

Configuration of IJT.

A striking feature of the configuration is the excellent all round visibility and the raised rear cockpit to provide good visibility and look over for the instructor. IJT has large cockpits, providing a spacious environment compared to cluttered, narrow cockpits of earlier generation trainers. IJT has a large side opening canopy, with two individual bubbles for the front and rear cockpits.

IJT is fitted with zero-zero K36LT ejection seats provided by M/s Zvesda of Russia. These seats have been derived from the highly successful SU-30 seats and modified for application on the MiG-AT. IJT uses Miniature Detonation Cord (MDC) to shatter the canopy prior to ejection. The seats also have a secondary capability of through canopy ejection Cockpit Displays & Systems.

The IJT would introduce trainee pilots to the glass-cockpit layout in just their second stage of flying training. Trainee pilots would benefit as adaptation would be easy when they move on to aircraft like the AJT (when acquired) and modern fighters. Main display for the pilot is the Smith’s Head-Up-Display (HUD). This will have all the flight information required to operate the aircraft besides display of the required weapon symbology to carry out air-to-ground and air-to-air armament tasks. However, primary flight instruments such as Air Speed Indicator, Altimeter, Vertical Speed Indicator, etc., are 3 ATI (Air Transport Instruments) active matrix liquid crystal displays. Each of these can be swapped to display format of the other instruments. The Horizontal Situation Indicator and the Attitude & Direction Indicators are 4 ATI displays. Both the displays are swappable and the format of one can be displayed on the other in case of failure of either instrument. If the Air Data Computer fails, the pilot has all the required flight information available on an integrated standby information system.

An angle of attack indicator is also installed; an important feature for preparing pupils for operating MiG-21, Jaguar and Mirage aircraft types. No gyro-gun sight is fitted, as it would have been extremely difficult to support it in future. A Mission Computer provides air-to-ground weapon symbology for guns, rockets and bombs, and air-to-air weapon symbology for guns. A radio altimeter will provide the required range information for air-to-ground armament work. No inertial navigation platform is fitted. Instead, extensive use is made of the Global Positioning System (GPS). This can store up to 26 flight plans, each with 20 waypoints. The display of waypoint number, track and distance to it will be shown on the HUD. The GPS can be adapted for differential correction if required. Navigation equipment also includes the VOR/DME.

The instructor from the rear cockpit can simulate various failures and emergencies to check reactions of the trainee pilot; valuable in enhancing the training value.

Power Plant.

IJT is powered by a single highly reliable Larzac 04-20 engine, a twin spool turbofan with 2 stage LP and 4 stage HP axial compressors. The basic weight of the engine is 295 kg with a static thrust of 1440 kg (14.12 kN). It has an electronic fuel control system. These engines have already completed nearly 3 million hours on the Alpha Jets. Larzac 04-20 engine is also being produced under licence in Russia and powers the MiG-AT (in twin engine configuration). In order to provide good access to the engine, rear fuselage is a boom type of construction. The option to go in for a higher thrust version of Larzac engine (1700 kg with Full Authority Digital Electronic Fuel Controls (FADEC)) for the production version of the IJT is also being considered.

Controls.

The primary flight controls are manually operated and the arrangement is conventional, with an electrically actuated tail plane. Additional electrical trim facility has been provided for both aileron and rudder. Five hard points are available, with the centre line station dedicated to gun pods; drop tanks are carried on wing outboard pylons. IJT can carry an assortment of armament stores up to a total load of 1000 kg, distributed on the hard points.

Performance.

The performance of IJT would be the same as that of Kiran. However, a major advantage of IJT is the enhancement of training value, with more repetition per unit time. This has been made possible due to low Specific Fuel Consumption (SFC) of Larzac engine (SFC: 0.76 kg/kg/hr: Bypass ratio: 1.04) and resultant fuel economy. Pilots will also have a good feel of high speed as the aircraft has a maximum speed of 750 kmph, and maximum Mach No of 0.75. Take-off and landing distances would be within 1000 mtrs in clean configuration. Stalling speed in clean configuration is expected to be around 175 kmph and in landing configuration 155 kmph. IJT would be cleared to +7g and –2.5g. It would have a range in excess of 1200 kms and endurance in excess of 2.5 hours. The rate of climb at sea level is expected be in excess of 1200 mtrs/min.

Flight Testing & Development.

HAL is planning to accelerate the process of flight testing and development so that the aircraft is inducted into service as early as possible. It is reported that the second prototype, which is under fabrication, is expected fly towards the end of this year. This would certainly help in increased effort toward flight testing. It is learnt that about 500 flights are planned towards development flight testing. Aircraft and Systems Testing Establishment (ASTE) of IAF would participate in the joint development trials. This would help in compressing the timeframes.

Induction to Service.

HAL has planned to initially produce 12 aircraft as Limited Series Production for early induction to the IAF. Thereafter, HAL expects to produce 200-250 IJT aircraft at the rate of 20 per year.

INAUGURAL FLIGHT OF IJT – HJT-36 ON 21st MARCH 2003

The official function, Inaugural Flight of IJT as it was called, was held on 21st March 2003 at HAL Bangalore Complex (BC). Defence Minister Mr. George Fernandes was the Chief Guest. The other dignitaries present were, Mr. O. Rajagopal, Minister of State, Defence Production; Air Chief Marshal S Krishnaswamy, Chief of the Air Staff; Shri N.S. Sisodia, Secretary, Defence Production & Supplies (DP&S), Govt of India; Dr. V.K. Aatre, Scientific Advisor to Defence Minister (SA to RM). There were a large number of invitees from the world of Aeronautics including many former personnel of HAL. The print and electronic media was also well represented.

The function commenced with a brief welcome address by Mr. N.R. Mohanty, Chairman HAL, followed by a presentation on the IJT project by Mr. Yogesh Kumar, Executive Director (Aircraft Research & Development Centre, HAL ((ED (ARDC)). Yogesh Kumar highlighted the salient features of the project explaining as to how the conception to first flight took place in a record time; that is as good or even better than the world standards. He also brought out the innovative methods and management techniques that were adapted for the IJT project.

After the initial brief all the dignitaries and invitees moved to the tarmac at HAL Airport, Bangalore to witness the flight of the IJT. Sqn Ldr Baldev Singh took off at 10 AM to a thunderous applause from those present to witness the inaugural flight of the IJT. After take off, he raised the undercarriage turned right, climbed to a height of 200 mtrs and executed a horizontal figure of eight at a speed of 450 kmph. The aircraft looked neat with its impressive lines and was seen to perform the turns smoothly. After the initial manoeuvres, a Kiran Mk II aircraft joined up with the IJT in close formation. Both the aircraft flew past in formation over the runway at 50 mtrs at a speed of 500 kmph. The commentator rightly said “there you see the IJT of today and the IJT of tomorrow”. Thereafter, Baldev Singh came in and did a perfect landing. As he taxied back and switched off, he was carried on the shoulders by a large number of HAL personnel. The VIPs lead by the Defence Minister, Mr. George Fernandes met Sqn Ldr Baldev Singh and congratulated him.

Although called the inaugural flight, the flight of IJT on 21st March 2003 was its seventh flight, since it first flew on 7th March 2003.

Dignitaries and the invitees then moved for the main function that commenced at 11 AM at Dr. Ghatage Convention Centre, HAL (BC). In his emotionally charged welcome address, Mr. N.R. Mohanty described as to what a proud moment it was for the entire HAL family. He was particular in complementing the designers, engineers and technicians who had worked relentlessly, with dedication, to make the IJT flight possible in a record time. He set aside all scepticism being expressed in certain quarters as to whether HAL can handle so many projects at the same time. Chairman stated that if necessary the Company would be restructured and the manpower redeployed to take on additional tasks besides the ongoing programmes.

There is a whispering campaign by certain vested interests in spreading a canard that HAL was neglecting its commitment towards the Light Combat Aircraft (LCA). The LCA programme is managed by Aeronautical Development Agency (ADA) functioning under the aegis of Defence Research & Development Organisation (DRDO). HAL is the prime contractor for manufacturing the aircraft. A leading daily had also published a column with headlines “Don’t forget LCA”. Mohanty set aside all balderdash with a remarkable punch line “HAL is hungry for work”.

Addresses were given by the Chief of Air Staff, Air Chief Marshal S Krishnaswamy, followed by  Mr. N.S. Sisodia, Secretary (DP&S) , Dr V.K. Aatre, SA to RM , Mr. O. Rajagopal, Minister of State, Defence Production and Mr. George Fernandes, Defence Minister.

In appreciation of the excellent work done, Defence Minister honoured and presented mementos to a number of people involved in the IJT project. The first to receive the honour was Sqn Ldr Baldev Singh, followed by Mr. Ashok Baweja, Director (Design and Development), Mr. Yogesh Kumar, ED (ARDC). Mementos were also present to strategic partners like Certifying Authority, Directorate of Aeronautical Quality Assurance, Commandant, ASTE etc.

As it happens due to oversight or otherwise, the name of Mr P Jayasimha, Additional General Manager (ARDC) was not mentioned during the proceedings. This quiet and unassuming designer is the chief architect of the IJT project who has been with it since inception (the very first pencil mark). Jayasimha with his dedication and total commitment was able build a highly motivated team of young designers. He remained the unsung hero.

Most of the questions by the media to Mr George Fernandes pertained to security concerns and somehow the IJT went into a bit of background. Inaugural flight of the IJT, an important milestone in the History of Aviation in India was carried only in page 4 or 5 in most of the leading dailies, as Iraq war and cricket occupied the space in the front page.

As mentioned earlier, Kiran aircraft has an excellent track record with one of the lowest accident rates among the contemporary aircraft in the world. It is our earnest hope that HJT-36 would do even better.

HAL has the capability to develop and build our own AJT and it is in the National interest that this project is taken up as a challenge. HAL should start developing an AJT on priority with a plan to drastically reduce the gestation period. Aircraft should be designed with growth potential to add systems, cater for changes in technology and make variants. AJT project could easily be launched with present level of confidence generated by the ongoing IJT project. This would also ensure that only a limited number of aircraft are bought out to take care of training during the gestation period. HAL should not fall in to the trap of licence production.

---

This article was first published in Indian Aviation Magazine.  Our thanks to Wg Cdr Kukke Suresh and Indian Aviation for the permission to reproduce this on our website. Wg Cdr Suresh had also written the article AJT and the IAF.

The photographs are the kind courtesy of Mr. Sanjay Simha.

 

---

 

Text Copyright © WG CDR KS SURESH (RETD) .  Photos Copyright © SANJAY SIMHA . All rights reserved.