A soaring success

Published : Jul 02, 2004 00:00 IST

The test flight of the Saras prototype proves the capability of Indian scientists. What has also been demonstrated is poor technology management in the making of the aircraft.

POSTERITY will regard May 29, 2004, as a landmark date in Indian aviation history. On that day, the first prototype (PT-1) of the indigenously designed and built civilian passenger aircraft took to the skies. The experimental flight, which lasted nearly 25 minutes, took a triangular detour at an altitude of about 2,100 metres above mean sea level (MSL) over Anekal and Malur near Bangalore, the hub of Indian aerospace activity, and touched speeds of 100-115 knots (185-215 km/h). During its second test flight on June 7, the aircraft flew at a higher altitude of about 2,400 m above MSL.

Named Saras, after the Indian crane known for its grace and beauty in flight, it is a Light Transport Aircraft (LTA), with the design objective of being able to carry between eight and 14 passengers and extendable to an 18-passenger variant, in multiple modes of operation. The successful flight - though it was late in coming after the roll-out in February 2003 - marks a milestone in the initiative of the National Aerospace Laboratories (NAL), a constituent laboratory of the Council of Scientific and Industrial Research (CSIR) in Bangalore, and the Hindustan Aeronautics Ltd. (HAL) to design and develop India's first commercial civilian aircraft. The inaugural flight is likely to be flagged off by Prime Minister Manmohan Singh later this month. The second prototype (PT-2) is expected to fly about a year later.

Although HAL has been involved in the licensed production of different military and small civilian aircraft such as the Dornier 228, which belongs to the Saras class, since the 1980s and had even started the production of the first indigenous military aircraft HF-24 (Marut, designed by the famous German designer Kurt Tank who had migrated to India) during the 1960s and 1970s, the Saras project is its first foray into manufacturing an indigenously designed civilian aircraft. NAL's research and development (R&D) agenda includes the design and development of small- and medium-sized aircraft and initiatives to promote a vibrant civil aviation industry. It was the late Satish Dhawan, former chairman of the Indian Space Research Organisation (ISRO) and the then chairman of NAL's research council, who urged NAL about 15 years ago to shift its focus to civil aviation and take up the designing of a commercially viable small civilian aircraft. A study by NAL in the mid-1980s revealed that there are many unused airfields in the country that could be suitable for air transportation using small, rugged passenger aircraft. Dhawan's prompting resulted in a series of reports by J. P. Singh and Raj Mahindra of NAL highlighting the tremendous potential of civil aviation, particularly of a `fourth level' feeder airline, in the country. In fact, in the 1960s Raj Mahindra had conceived of a `Hindustan Transport Aircraft' (HTA) that would use the shortest runways and the roughest airfields to link virtually every part of the country. In a sense, the concept of an LTA had its origins in that idea. And to honour these two visionaries, the first two prototypes have been labelled VT-XSD and VT-XRM respectively.

In the 1980s, NAL had hardly any experience in aircraft designing. It had only designed and built a small Light Canard Research Aircraft (LCRA) more from the perspective of designing an air-borne platform using composites, which was an emerging technology in aerospace applications. The project was taken up in 1985 and the first flight of the LCRA took place in 1987. The LCRA was based on the readily available Rutan kit and was built using fibre, foam and resin. But its aerodynamic characteristics were analysed extensively. A complete structural analysis, including vibration and aero-elastic behaviour, was done and flight tests were carried out to substantiate the analysis. This gave NAL the confidence to design, build and fly a completely new design with composite materials.

Thus NAL undertook the design of an all-composite two-seater trainer aircraft, the NALLA (NAL-Light Aircraft), which was later named Hansa. Work on the design began in 1991 and the aircraft flew for the first time on November 23, 1993. Hansa had three designs and the prototype that flew was based on the second design, Hansa-2. However, the type-certified production version was based on the second prototype of the third design, Hansa-3-II. Hansa-2 was re-engineered during 1995-96 to incorporate engine change and weight reduction. Hansa obtained the provisional type certification from the Director-General of Civil Aviation (DGCA) in December 1998, more than five years after it first flew. In fact, the final type certification came only in February 2000 and it has been cleared for both day and night operations.

So far, six versions of Hansa-3 have been built, including the two prototype versions, one pre-production aircraft and three productionised aircraft. The aircraft is currently produced by Taneja Aerospace and Aviation Ltd. (TAAL), Bangalore. The last three have been supplied to the Ministry of Civil Aviation for use in the flying clubs at Hyderabad, Thiruvananthapuram and Indore. Together, Hansa-3 is said to have clocked 2,000 hours of flying until 2003 without any incident and with highly satisfactory reports of its performance from the trainee pilots. Besides the confidence to undertake bigger projects, the more important outcome of the development of Hansa was the provision of expertise to write complex codes of Computational Fluid Dynamics (CFD) for precise aerodynamic analysis and numerical simulations needed for proper aircraft design.

Armed with the successful experience in aircraft designing, CFD tools and engineering in composites, NAL took up the challenge of developing a larger commercial aircraft like Saras. But the challenges have proved to be of a different order than imagined by NAL scientists and engineers. Given the shortcomings in design evidenced by the flight of the first prototype, it would be a highly creditable achievement if Saras gets type-certified by the DGCA by 2010.

Primarily, Saras is intended as an air-taxi and commuter service aircraft in short hauls. However, from the very beginning, it was conceived as a state-of-the-art aircraft that will be a cost-effective solution for a variety of air transport services. Its large cabin volume of 16 cubic metres has been designed with that objective in view. It is designed to have a seating capacity of 14 passengers (plus baggage), extendable to 18 seats with curtailed cargo-baggage space, in the high-density commuter version. The aircraft is intended to fulfil a variety of other roles, such as those of an eight-seater executive transport, a light package carrier and an air ambulance and for VIP transport, coastal and border patrol, disaster management, and aerial research services such as remote-sensing, surveillance, geophysical survey and mapping.

The decision to place the indigenous aircraft in this segment was based on three market surveys, conducted in 1991, 1994 and 1998, which consistently showed that there was a potential for a feeder airline, particularly in the northeastern sector. A detailed report by the Technology Information and Forecasting Council (TIFAC) of the Ministry of Science and Technology (MoST) in 1993 came out with similar conclusions. The surveys indicated a demand of over 200 Saras-type aircraft in the country over the next 10-15 years in various roles. On an average, about six aircraft of this class are purchased from abroad every year by the corporate sector. The demand would increase if the indigenous aircraft in this segment are priced competitively. The export potential of the aircraft was also considered.

The design goals for Saras included its all-weather, day-and-night operability, short take-off and landing characteristics, operability from semi-prepared runways even at high altitude airfields on hot days with little compromise on the take-off weight, high cruise speed, ruggedness and reliability, easy maintenance, low cabin noise and a cabin comfort level that can match regional airlines, high `specific range' (range per kg of fuel consumed) and low operating cost. Since a turbo-prop aircraft lends itself to meeting these objectives, Saras has been designed as a twin turbo-prop aircraft powered by two 850 hp (horse power) Canadian Pratt and Whitney PT6A-66 engines mounted on the rear, on stub wings located at aft fuselage. Besides being highly proven engines for this class of aircraft, modularity of the PT6A family of engines is stated to be greatly advantageous from the point of view of maintenance. The engines drive five-bladed propellers, 2.16 m in diameter, facing aft in the unusual `pusher configuration', to give the aircraft a unique appearance.

Aircraft have basically two types of propeller configurations - `pusher' and `tractor' - the former having the propeller assembly behind the engines. The thrust produced by the propeller pushes the aircraft forward. Although an old concept, the pusher configuration was never popular until recent times. Hansa-1 had been conceived in the pusher mode. However, even in the wind tunnel testing of a 1:5 scale model, severe problems with the design were revealed and therefore, it was abandoned. Before Saras, only two aircraft are known to have used the concept: the Gates Learjet-Piaggio P.180 Avanti, an Italian 8-10 seater executive aircraft, and the Beech Starship 2000, an American 18-20 seater aircraft, both during the 1980s. Both P.180 and Beech 2000 used PT6A-66. Avanti's design is in fact doubly unique. Besides its pusher propellers, it uses the three surface lift concept, with short additional wings in the nose cone region. Both proved to be commercial failures for a variety of reasons. At $4.5 -5 million, the price, which is comparable to or even exceeds that of turbojet aircraft in this class at 1980 rates, was one of the reasons. Avanti, it is learnt, has been revived. Saras has an estimated price tag of $3.75 million (Rs.16.5 crores) at current prices. Besides the engines and the propellers, the imported items in Saras include digital avionics system components, fuel system components, electrical power generation components, hydraulic system components, emergency system components and certain raw material and standard parts. The cost would come down if some of these get progressively indigenised.

The design target parameters of the 15-m-long, 14.7-m-wide and 5.26-m-high Saras include a maximum take-off weight of 6,100 kg and a maximum payload of 1,232 kg, a high cruise speed of over 600 km/h, an endurance of six hours, a maximum flight altitude of 12 km (cruise altitude 10.5 km), short take-off and landing distances of about 600 m, the maximum rate of climb of 12 m/sec, a low cabin noise of 78 dB, a range of 600 km with 19 passengers, 1,200 km with 14 passengers and 2,000 km with eight passengers, a high `specific range' of 2.5 km/kg and a low cost of operation of Rs.5/km. If these parameters are achieved, which seems rather doubtful in its present design, then a comparison of Saras with turbo-prop aircraft in this payload segment will show that Saras scores much better.

Besides NAL, the prime agency responsible for design and development, system integration and project management, and HAL, the fabricator of some key systems and components, the agencies that are partners in the development of Saras include the Aeronautical Development Agency (ADA) and the Gas Turbine Research Establishment (GTRE) of the Defence Research and Development Organisation (DRDO), the Aircraft System Testing Establishment of the Indian Air Force, the Aerospace Design Engineers Group (ASDE), a private agency approved by the MCA, TAAL, the CSIR's Central Mechanical Engineering Research Institute (CMERI) at Durgapur, the Structural Engineering Research Centre (SERC) at Chennai and the Central Electrochemical Research Institute (CECRI) at Karaikudi, and 25 small and medium qualified component manufacturers.

One of the key technologies used in achieving the design objectives is the selective use of composite material for low structural weight. The aircraft uses a judicious mix of aluminium alloy (in wings, stub wings and fuselage) and composite material (in empennage or tail assembly structure, flaps, control surfaces and nacelle) to realise an efficient structure with a 30,000-hour life. The use of propellers in the `pusher' mode results in a quieter cabin unlike the usually noisy propeller-driven planes even while achieving an undisturbed air flow on the wings. Among the major assemblies in the prototype, NAL was responsible for the fabrication of the fairing, the flap, the aileron, the rudder, the elevator and the nacelle, HAL for the wing, TAAL for the horizontal tail, the vertical tail and the stub wing.

First taken up in the mid-1990s, Saras has taken quite a while to be realised. Initially it was intended to be a joint developmental project between the Russian Myasischev Design Bureau (MDB) and the Indian government, each meeting 50 per cent of the cost, originally estimated at Rs.40 crores, nearly one-fourth of the current actual cost. According to NAL, MDB was unable to raise resources and ultimately the partnership fell through. Then NAL looked to the private company TAAL. However, industrial slowdown forced TAAL to pull out as it did not have the money, says Vijaya Simha, managing director of TAAL. Also, with the government share not forthcoming, the time schedule was not followed. With no possibility of a private venture capital backing a maiden aircraft venture, the CSIR had to turn to the Technology Development Board (TDB) of the MoST for financial support. Says Vijaya Simha: "We decided to be a contractor for Saras and undertake job work."

Finally, in June 1999 the Cabinet Committee for Economic Affairs (CCEA) approved the Saras project at a total cost of Rs.131.38 crores and fixed the project duration at three and a half years. Of the total funds allowed, nearly 50 per cent or Rs.65.3 crores was given by TDB, part of it as grant (Rs.53.8 crores) and the rest as loan. This is the only project launched by a public-funded laboratory for which TDB has made an outright grant. It is also the largest sum committed by TDB for a single project. Of the remaining amount, the industrial partner HAL provided Rs.9 crores and the rest, amounting to Rs.42.58 crores, came from the budgetary allocations of the CSIR and the MCA. NAL's input has been valued at Rs.14.5 crores. In the Tenth Plan, the project cost has been revised to Rs.157.59 crores. However, TDB has rejected the CSIR's request for an increase in the former's share of funding and the escalation is expected to be met from the Tenth Plan allocations.

But funding approval alone was not sufficient for the project to take off. In the wake of the sanctions imposed following the nuclear tests at Pokhran, NAL was listed as one of the entities, which meant that items from the United States were denied export licence by the U.S. Department of Commerce. The items that were denied included the propeller and its speed governor, the engine oil cooler, the oil low pressure warning switch, the torque pressure switch, engine vibration isolators, the de-ice system, the pilot seat and fire sensors. These had to be procured from alternative sources resulting in an increase in costs by about Rs.3 crores and time delays of up to one year. Now with the Saras prototype flying, all is not well with the project.

According to experts, the design seems to have hit an air pocket and it appears that the NAL team would have to go back to the drawing board to carry out a fair amount of redesign and re-engineering. There is a problem with regard to the empty weight of the aircraft - it is overweight by about 900 kg against the design value of about 4,100 kg. Obviously this increase in the empty weight would eat into the payload capacity designed to be 1,232 kg. The weight per passenger at about 75 kg plus the weight of internal fixtures, seats and upholstery means that it can carry two passengers at best. In addition, higher aircraft weight means lower fuel-carrying capacity and hence a lower range that it can fly with the maximum payload.

After the prototype flight, the flying range with 14 passengers has been scaled down to 400 km and with eight passengers to 1,400 km. But NAL continues to claim the specific range to be 2.5 km/kg and the cost of operation to be Rs.5/km. However, with such a greatly reduced range, the aircraft will no longer be state-of-the-art and, in terms of specific range and other relevant parameters, no longer a competition for other comparable aircraft in this segment.

Although weight increase in the development stage is not uncommon, the increase in this instance is almost equal to the total payload capacity. How much of this is due to the pusher configuration is not clear. In a letter to the Editor of The Hindu, S.R. Valluri, former Director of NAL and ADA, severely criticised the project management for not giving adequate importance to the Weight Control Group, which has a critical function in the development of an aircraft, and held the project leader entirely responsible for this. He had apparently written to the CSIR Director-General with no effect. While this may or may not be true, the problem is indeed serious as there appear to be no solutions short of significant design changes, which will incur significant costs.

Apparently, 150-200 kg of additional margins had to be built into the structures for meeting the FAR 25 certification standards of the U.S. Federal Aviation Administration (FAA), which the DGCA follows. Earlier this used to be applicable only for bigger aircraft like Airbus or Boeing 747, and for smaller aircraft FAR 23 was the standard. Now, under the recently revised certification procedure, FAR 25 is to be applied for all aircraft carrying more than 10 passengers. There is bound to be a greater degree of conservatism at various levels in the first prototypes and it might be possible to bring down the aircraft weight by 200-300 kg at best. Clearly, weight reduction has to be a priority for the designers if the aircraft has to compete in the marketplace and be economically viable.

Responding to this criticism, NAL has stated that the all-up weight of 6,100 kg was estimated long back only on the basis of preliminary design and drawings and it could not be taken as the weight of the final production standard. Apparently, the different subsystems chosen because of the sanctions added to the weight. The final production standard for a 14-seater aircraft will now be, according to NAL, 6,900 kg with the reduced range of 400 km. It seems to imply that much weight reduction is not possible.

NAL is thinking in terms of an engine of higher power with a suitable propeller for PT-2, which is expected to cost about Rs.3 crores, in order to achieve the final production standard. According to some experts, there is some room for increasing the all-up weight in the present engine through careful redesign. But that is not enough to solve the problem. Therefore it is not clear whether PT-2 will fly a year later. But even to achieve this higher production standard, a weight optimisation exercise - apparently a reduction of 300 kg is possible - is being taken up. A provision of Rs.40 crores has been made for this in the Tenth Plan by the Expenditure Finance Committee (EFC). But it must be pointed out that already about Rs.25 crores has been spent from the Tenth Plan funds, given the escalation in total cost. So, in all, the Cabinet will have to approve an additional funding of about Rs.70 crores.

Experts point out that increasing the power of the engine and changing the propeller would result in significant design changes. For instance, the gear-box may have to be redesigned. If the propeller has a higher diameter, the stub wing will have to be larger, which would warrant changes in the fuselage design. Knowledgeable sources say that this problem was known nearly one and a half years ago but it was ignored in a bid perhaps to get the aircraft off the ground in order to prove the workability of the basic design. But this has meant an additional developmental cost, which could have been greatly reduced through timely action.

There could be other issues of concern. For instance, TAAL has set up jigs and shop-floor tools according to the present design. A change in design could mean significant retooling which, Vijaya Simha says, would have to be evaluated carefully. So far, according to him, the company has not charged any fee above the labour cost for the prototypes. "Ultimately, the right of refusal is ours," he says. If that happens it could mean a big blow to the programme. The successful flight of PT-1, coming after the successes of LCRA and Hansa, has certainly demonstrated the basic scientific and technical skills of India's scientists. But what it has also perhaps shown is poor technology management, which is a crucial element when the attempt is to make a mark in the marketplace ultimately.

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