Windjammer
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Wednesday, July 19, 2017
IDN TAKE: The Elusive Star
HJT-36 SITARA Subsonic Intermediate Jet Trainer developed by Hindustan Aeronautics Ltd
There was palpable excitement in the aviation circles as it was only four years since project approval that the aircraft had flown. Alas, it was not to be. As often happens in the development of a new aircraft, unforeseen problems derailed the program to such an extent that today, one does not know when it will enter service.
The Hindustan Aeronautics Limited the largest defence public sector undertaking (DPSU) under the Ministry of Defence (MoD), is also the premier aeronautical complex in South East Asia, but with a dubious record and some credits. It had proposed the development of a replacement to its HJT-16 Kiran trainer aircraft for the intermediate training stage (Stage 2) of the trainee pilots of the Indian Air Force (IAF). In 1997, HAL on its own initiative commenced designing an intermediate jet trainer (IJT). The MoD accorded approval in 1999, after the IAF had reviewed the project details.
Two prototypes were cleared with an initial budget of `180 crore which was subsequently increased to `465 crore in 2005. The expenditure so far is `635 crore. The IAF has been committed to the project from its inception and has even placed an order for 73 aircraft. It has also promised to provide additional funds to the program.
Plagued With Problems
The Larzac engines from France powered the first two prototypes of the HJT-36 Sitara. However, the IAF felt the aircraft was under powered as the engine developed only 14.1 kN thrust. It is standard practice that an engine is decided during the initial design phase itself, when the designers, giving margin for some additions, estimate the all-up weight. It is also accepted that the final weight of an aircraft will be slightly higher than the earlier estimates. In the case of the HJT-36, however, the final weight was much higher than the earlier approximation, leading HAL to turn to Russia for another engine with a higher thrust rating. The NPO Saturn AL-55I engine, which produces 16.9 kN thrust, was selected and a contract signed for an initial production of 250 engines, with the option for more. The agreement also included assistance in setting up production in HAL’s Koraput Engine Centre. The first of the engines was delayed by two years, the first of the many delays to follow and was delivered only in December 2008. Fitted with the new engine, the PT-1 flew on May 9, 2009.
Although the new engine performed well on the aircraft, it has problems. First, the engine is yet to be certified; second, it is reported that this engine has a very short ‘flight-life’. It requires an overhaul at every 150 hours of flying, when ideally it should be around four times this figure and with a total life of about 1,800 to 2,400 hours. Considering the intensity of flying that the aircraft would be subjected to in training, the short lifespan translates to an overhaul every two months or so, which further translates to extended down time for every aircraft, at a colossal utilisation of man-hours. This would inflict extra pressure on the maintenance staff and engine production factories and would require an increased buffer stock of engines. As per the manufacturer, subsequent to flying a certain number of hours, the engine life may be increased. The change, however, in the overhaul schedule can be incorporated only after a strip examination of each component and exhaustive ground testing. The Russians are confident that the requirement of 600 hours between overhauls and a total lifespan of 1,800 hours can be achieved as the IAF gains experience on the maintenance of the engine. One can be optimistic, but should not take it at face value.
Endemic Delay
Apart from the engine, there are other reasons for the delay. In February 2007, during a flight display at the Aero India show at the Yelahanka, the first prototype aircraft, PT-1, suffered serious damage when its canopy flew off during take-off causing the aircraft to veer off the runway, thus damaging the right wing. In the process of regaining control of the aircraft, and getting back on to the runway, one of the tyres burst. The accident caused a delay, although the aircraft flew again after extensive repairs. The second accident occurred exactly two years later, on February 4, 2009, when after a routine test sortie, the aircraft landed on its belly, damaging the structure, undercarriage and the wing tips. The investigation into the cause of the accident delayed the project further. Yet another accident occurred after two years in April 2011, wherein the pilots ejected and the aircraft was lost. The remaining aircraft were grounded and major changes had to be initiated in the flight control system, leading to associated design changes for recovery and resolution.
Apart from these three major accidents, which have considerably delayed the certification of the aircraft, there was another incident, comparatively very minor, when one of the ejection seats fired inside the hangar. Though there was no damage to the aircraft, the flight testing process was delayed as another ejection seat had to be imported; till the seat arrived, the aircraft remained on the ground.
There are other causes for delay, apart from the three accidents. Any trainer aircraft has to have safe stalling and spinning characteristics. This is essential as inexperienced trainee pilots could get into a difficult situation due to mishandling of controls. Even inexperienced pilots should have the confidence to effect a safe recovery from a stall or spin. As per reports, stall tests were aborted on the HJT-36, as the aircraft was rolling 16 degrees at the point of stall. This was a very undesirable characteristic and had to be rectified on priority.
On July 5, 2014, Shiv Aroor, a defence correspondent, had filed an exclusive report (Livefist, “Exclusive: Totally Cornered, HAL to Redesign Lumbering Intermediate Trainer”): “The HJT-36 aircraft presently weighs around 4,150 kg in its normal training configuration….HAL is envisaging achieving maximum possible weight reduction/optimisation for the aircraft….The design of the above need to be revisited, analysed and the scope for weight reduction/optimisation studied while ensuring the required strength, stiffness and fatigue criteria….Towards this HAL is looking forward for partnership/technical assistance/consultancy from a well experienced airframe design house….This weight reduction/optimisation study must be comprehensive, encompassing all the Structure, Mechanical Systems and Electrical Avionics Systems.”
The then Defence Minister, Arun Jaitley (not by mere coincidence), made it official on August 5, 2014, in response to a question said: “HAL, which has been developing the IJT to replace the Kiran aircraft, has not so far been able to resolve critical wing and airframe design and development issues related to stall and spin."
On account of the inordinate delay in the IJT project, the IAF initiated the process for extending the technical life of the Kiran aircraft. The IAF has also initiated action to look for alternative options for the IJT.” According to a report in the New Indian Express on October 10, 2013, “Engineers and designers at HAL’s Aircraft Research & Design Centre have the daunting task of identifying and correcting the inherent asymmetry of the aircraft. HAL hopes to get the initial operational clearance for the IJT by the end of December 2013, though insiders said the deadline might get pushed to next year.” The HAL had hired BAE Systems to act as consultants to evaluate the stall and spin tests of the aircraft. Unconfirmed information of October 2014 is that the tests have been successful and all issues in this regard have been resolved. If this is so, there is still some hope of the aircraft flying with the IAF by 2016.
Alternative Options for the IAF
Apart from the accidents and asymmetry issues, there is also the issue of increasing weight from the initial design estimates. While it is acceptable for the weight to increase from the initial approximations, here is a case of “obesity”! It is rather difficult to reduce weight when the aircraft has completed a major share of the flight-testing and is heading towards certification. One can only hope that along with the asymmetry corrections, the foreign design experts that the HAL hired, have also been able to resolve the problems of increased weight, failing which, the IAF would have to accept an under powered aircraft for its training purposes.
The HAL hopes to get the initial operational clearance in 2015. While the IAF has been patiently waiting for the aircraft, gaps are developing in its training program. The HAL has to live up to its commitment of delivering the 12 limited series production aircraft to the IAF and later the balance 73 of the series production. The time frame for delivery of the IJT however remains uncertain.
In the meanwhile, the IAF has reportedly published a nonbinding global request for information (RFI) regarding the IJT. The delivery of the HJT-36 is nowhere confirmed, hence, in the interim, the present trainer, HJT-16, planned to be phased out of service, has been given a fresh lease of life to 2018, albeit with maintenance support problems. The induction of a limited number of new trainer aircraft from abroad has been done earlier too, when in 1974, 50 Iskra jet trainers were purchased to plug training gaps due to the delayed induction of the HJT-16!
Training is an important phase in a pilot’s life. The basic and advanced training in the IAF has been taken care of with the induction of the Pilatus PC-7 and the Hawk respectively. Hopefully, the Raksha Mantri would appreciate the predicament of the IAF and fast-track the procurement of an IJT from abroad as an interim solution, since there is no word on the aircraft in the public domain. One also hopes that the IJT Sitara does not go the LCA way and is indefinitely delayed. Any further delay, for reasons whatsoever, would give acceptance to the old nursery rhyme, “Twinkle, twinkle, little star. / How I wonder what you are”!
IDN wishes to thank Air Marshal Dhiraj Kukreja (Retd) for this excellent piece
IDN TAKE: The Elusive Star
HJT-36 SITARA Subsonic Intermediate Jet Trainer developed by Hindustan Aeronautics Ltd
There was palpable excitement in the aviation circles as it was only four years since project approval that the aircraft had flown. Alas, it was not to be. As often happens in the development of a new aircraft, unforeseen problems derailed the program to such an extent that today, one does not know when it will enter service.
The Hindustan Aeronautics Limited the largest defence public sector undertaking (DPSU) under the Ministry of Defence (MoD), is also the premier aeronautical complex in South East Asia, but with a dubious record and some credits. It had proposed the development of a replacement to its HJT-16 Kiran trainer aircraft for the intermediate training stage (Stage 2) of the trainee pilots of the Indian Air Force (IAF). In 1997, HAL on its own initiative commenced designing an intermediate jet trainer (IJT). The MoD accorded approval in 1999, after the IAF had reviewed the project details.
Two prototypes were cleared with an initial budget of `180 crore which was subsequently increased to `465 crore in 2005. The expenditure so far is `635 crore. The IAF has been committed to the project from its inception and has even placed an order for 73 aircraft. It has also promised to provide additional funds to the program.
Plagued With Problems
The Larzac engines from France powered the first two prototypes of the HJT-36 Sitara. However, the IAF felt the aircraft was under powered as the engine developed only 14.1 kN thrust. It is standard practice that an engine is decided during the initial design phase itself, when the designers, giving margin for some additions, estimate the all-up weight. It is also accepted that the final weight of an aircraft will be slightly higher than the earlier estimates. In the case of the HJT-36, however, the final weight was much higher than the earlier approximation, leading HAL to turn to Russia for another engine with a higher thrust rating. The NPO Saturn AL-55I engine, which produces 16.9 kN thrust, was selected and a contract signed for an initial production of 250 engines, with the option for more. The agreement also included assistance in setting up production in HAL’s Koraput Engine Centre. The first of the engines was delayed by two years, the first of the many delays to follow and was delivered only in December 2008. Fitted with the new engine, the PT-1 flew on May 9, 2009.
Although the new engine performed well on the aircraft, it has problems. First, the engine is yet to be certified; second, it is reported that this engine has a very short ‘flight-life’. It requires an overhaul at every 150 hours of flying, when ideally it should be around four times this figure and with a total life of about 1,800 to 2,400 hours. Considering the intensity of flying that the aircraft would be subjected to in training, the short lifespan translates to an overhaul every two months or so, which further translates to extended down time for every aircraft, at a colossal utilisation of man-hours. This would inflict extra pressure on the maintenance staff and engine production factories and would require an increased buffer stock of engines. As per the manufacturer, subsequent to flying a certain number of hours, the engine life may be increased. The change, however, in the overhaul schedule can be incorporated only after a strip examination of each component and exhaustive ground testing. The Russians are confident that the requirement of 600 hours between overhauls and a total lifespan of 1,800 hours can be achieved as the IAF gains experience on the maintenance of the engine. One can be optimistic, but should not take it at face value.
Endemic Delay
Apart from the engine, there are other reasons for the delay. In February 2007, during a flight display at the Aero India show at the Yelahanka, the first prototype aircraft, PT-1, suffered serious damage when its canopy flew off during take-off causing the aircraft to veer off the runway, thus damaging the right wing. In the process of regaining control of the aircraft, and getting back on to the runway, one of the tyres burst. The accident caused a delay, although the aircraft flew again after extensive repairs. The second accident occurred exactly two years later, on February 4, 2009, when after a routine test sortie, the aircraft landed on its belly, damaging the structure, undercarriage and the wing tips. The investigation into the cause of the accident delayed the project further. Yet another accident occurred after two years in April 2011, wherein the pilots ejected and the aircraft was lost. The remaining aircraft were grounded and major changes had to be initiated in the flight control system, leading to associated design changes for recovery and resolution.
Apart from these three major accidents, which have considerably delayed the certification of the aircraft, there was another incident, comparatively very minor, when one of the ejection seats fired inside the hangar. Though there was no damage to the aircraft, the flight testing process was delayed as another ejection seat had to be imported; till the seat arrived, the aircraft remained on the ground.
There are other causes for delay, apart from the three accidents. Any trainer aircraft has to have safe stalling and spinning characteristics. This is essential as inexperienced trainee pilots could get into a difficult situation due to mishandling of controls. Even inexperienced pilots should have the confidence to effect a safe recovery from a stall or spin. As per reports, stall tests were aborted on the HJT-36, as the aircraft was rolling 16 degrees at the point of stall. This was a very undesirable characteristic and had to be rectified on priority.
On July 5, 2014, Shiv Aroor, a defence correspondent, had filed an exclusive report (Livefist, “Exclusive: Totally Cornered, HAL to Redesign Lumbering Intermediate Trainer”): “The HJT-36 aircraft presently weighs around 4,150 kg in its normal training configuration….HAL is envisaging achieving maximum possible weight reduction/optimisation for the aircraft….The design of the above need to be revisited, analysed and the scope for weight reduction/optimisation studied while ensuring the required strength, stiffness and fatigue criteria….Towards this HAL is looking forward for partnership/technical assistance/consultancy from a well experienced airframe design house….This weight reduction/optimisation study must be comprehensive, encompassing all the Structure, Mechanical Systems and Electrical Avionics Systems.”
The then Defence Minister, Arun Jaitley (not by mere coincidence), made it official on August 5, 2014, in response to a question said: “HAL, which has been developing the IJT to replace the Kiran aircraft, has not so far been able to resolve critical wing and airframe design and development issues related to stall and spin."
On account of the inordinate delay in the IJT project, the IAF initiated the process for extending the technical life of the Kiran aircraft. The IAF has also initiated action to look for alternative options for the IJT.” According to a report in the New Indian Express on October 10, 2013, “Engineers and designers at HAL’s Aircraft Research & Design Centre have the daunting task of identifying and correcting the inherent asymmetry of the aircraft. HAL hopes to get the initial operational clearance for the IJT by the end of December 2013, though insiders said the deadline might get pushed to next year.” The HAL had hired BAE Systems to act as consultants to evaluate the stall and spin tests of the aircraft. Unconfirmed information of October 2014 is that the tests have been successful and all issues in this regard have been resolved. If this is so, there is still some hope of the aircraft flying with the IAF by 2016.
Alternative Options for the IAF
Apart from the accidents and asymmetry issues, there is also the issue of increasing weight from the initial design estimates. While it is acceptable for the weight to increase from the initial approximations, here is a case of “obesity”! It is rather difficult to reduce weight when the aircraft has completed a major share of the flight-testing and is heading towards certification. One can only hope that along with the asymmetry corrections, the foreign design experts that the HAL hired, have also been able to resolve the problems of increased weight, failing which, the IAF would have to accept an under powered aircraft for its training purposes.
The HAL hopes to get the initial operational clearance in 2015. While the IAF has been patiently waiting for the aircraft, gaps are developing in its training program. The HAL has to live up to its commitment of delivering the 12 limited series production aircraft to the IAF and later the balance 73 of the series production. The time frame for delivery of the IJT however remains uncertain.
In the meanwhile, the IAF has reportedly published a nonbinding global request for information (RFI) regarding the IJT. The delivery of the HJT-36 is nowhere confirmed, hence, in the interim, the present trainer, HJT-16, planned to be phased out of service, has been given a fresh lease of life to 2018, albeit with maintenance support problems. The induction of a limited number of new trainer aircraft from abroad has been done earlier too, when in 1974, 50 Iskra jet trainers were purchased to plug training gaps due to the delayed induction of the HJT-16!
Training is an important phase in a pilot’s life. The basic and advanced training in the IAF has been taken care of with the induction of the Pilatus PC-7 and the Hawk respectively. Hopefully, the Raksha Mantri would appreciate the predicament of the IAF and fast-track the procurement of an IJT from abroad as an interim solution, since there is no word on the aircraft in the public domain. One also hopes that the IJT Sitara does not go the LCA way and is indefinitely delayed. Any further delay, for reasons whatsoever, would give acceptance to the old nursery rhyme, “Twinkle, twinkle, little star. / How I wonder what you are”!
IDN wishes to thank Air Marshal Dhiraj Kukreja (Retd) for this excellent piece
