DEVELOPMENT PERSPECTIVES OF PISTON AND TURBOPROP TRAINERS AND THEIR COIN DERIVATIVES

Transcription

1 DEVELOPMENT PERSPECTIVES OF PISTON AND TURBOPROP TRAINERS AND THEIR COIN DERIVATIVES SLAVIŠA VLAČIĆ Department for Planning and Development (Ј-5), Abstract: Modern piston and turboprop trainers are the main tool for the primary and basic flight training. According to business forecast, the market for these categories of airplane will grow up in the near future. Beside that, modern piston and especially turboprop trainers are also basis for the development of their COIN derivatives. Some aircraft types of this subcategory have achieved significant market success. This paperwork is describing main characteristics of modern piston and turboprop trainers and their COIN derivatives and possible trends and perspectives in their development. The paperwork mainly indicates on aerodynamics, avionics and weapon systems development aspects. Some considerations of domestically developed aircraft Lasta is also included. Key words: trainer, flight training, COIN derivatives. Flight training is a course of study used when learning to pilot an aircraft. Given the expense of military pilot training, air forces typically conduct training in phases to winnow out unsuitable candidates. The cost to those air forces that do not follow a gradated training regimen is not just monetary but also in lives. Flight training is generally performed in three stages, in this paperwork described as primary, basic and advanced. The first stage, primary or ab initio training, is used to weed out those students who lack the aptitude to quickly become military pilots. It is generally performed in fixed-gear pistonengined aircraft with side-by-side seating [1]. The second stage is basic flight training. It practices fundamental skills of handling the plane and guiding the plane through the airspace. It consists basing handling, aerobatic flying, navigation flying, and sometimes formation flying. The total flight time in this phase of training is between flight hours, depends on type of plane and syllabus. Generally, piston and turboprop powered plane are used, and the jet plane in this phase becomes rarity. Jet training planes is typical for the advanced flight training, as a third stage. In any case, the main tool in the process of making a pilot, throughout the flight training, is an adequate training plane or simply trainer. There are many different types of training aircraft, especially in the primary and basic flight training phase. Also, there are many different divisions of the training planes, but the most important and common used is the division according to the type of powerplant, which determines its main characteristics and performances. In this paperwork, basing on topics, the main attention is paid to the piston and turboprop powered training planes, and their COIN derivatives. 1. PISTON ENGINED TRAINERS Airplane piston engines of today are, generally speaking, simple, air-cooled, horizontally opposed, four-stroke internal-combustion devices with low operating speeds and low specific output. Trainers driven by the piston engine belongs to the sort of the most economical trainers. Piston engined trainers are often divided based on the aerodynamical and cockpit configuration by following: fixed landing gear, side by side seats, retracting landing gear, side by side seats, retracting landing gear, tandem seats. The first subcategory is intended for the very basics, and it is represented by light aircraft not too dissimilar from civilian training aircraft. Representatives are ZLIN- 142/242, T-67 Slingsby Firefly, Valmet L-70, Saab Supporter MFI 17, Grob G-120A and Utva-75. For many decades after the Second World War there was considerable agreement that the primary training phase demanded an aircraft of around 150 kw, with fixed gear and side by side seating. The other two subcategories are more familiar with military training and can cover up to the 100 flight hours of syllabus. First considerable trainers in these subcategories has emerged during the 1970s and 80s. It was Italian SF.260 which has been followed by TB.30 Epsilon, T-35 Pillan and Lasta 1. They are also characterized by more powerful engines of around 250 kw. For training aircraft, side by side seating has the advantage that pilot and instructor can see each others' actions, allowing the pilot to learn from the instructor and the instructor to correct the student pilot. The tandem 105

2 configuration has the advantage of being closer to the normal working environment that a fast jet pilot is likely to encounter. Also, the tandem configuration usually has the higher ceiling skills as mentioned before. For many years, there were no significant changes in the piston engine trainer category. But, the appearance of the new sort of piston engines called ROTAX at the beginning of 90s, and new technologies in the producing of aircrafts, had great impact in application of trainers. Instead of trainers with engines of around 150 kw and gross weight more than 1000 kg, air forces choose lighter and less powered aircraft. On that way, for the purpose of student screening, some air forces procured America s new Light Sport Aircraft (LSA) category. The 2004 LSA regulations apply to twoseaters with a maximum weight of 600 kg, a maximum speed of 220 km/h, a stalling speed no greater than 83 km/h, a fixed gear and one non-turbine engine. Intended to provide more affordable powered flying, this concept has generated about 100 new designs. Manufactured in low-cost regions, light sport aircraft sell for around $ ; less than half the price of a Cessna 172 [2]. A good example in this category is the $ Cessna 162 Sky Catcher, which has a 75 kw engine and a gross weight of 599 kg. Another lightweight US product is the Cirrus SRS (a derivative of Germany s 520-kg B&F Technik Fk-14 Polaris). The current LSA leaders in delivery terms are European products such as the Flight Design CT series. The other European noteworthy types are Czech s Evetkor Sportstar and Italy s Tecnam P92. Even the most powerful air forces started to use LSA category in primary flight training. For example, the US Air Force now has its initial flight screening (IFS) carried out by Doss Aviation of Pueblo, Colorado, using the 750- kg Diamond Aircraft DA20, powered by a 93-kW Teledyne Continental engine and costing around $ The IFS course includes 19 sorties and 25 flight hours. The program is deal with up to 1900 students annually. In USAF practice, DA20 have replaced T-67 which is typical piston engine trainer. Many of LSA use ROTAX engine which differs from conventional aircraft engines (such as the Lycoming O- 235) in that it has air-cooled cylinders with liquid-cooled heads and uses a 2.43:1 gearbox (PSRU) to reduce the engine's relative high 5800 rpm shaft speed to a more conventional 2400 rpm for the propeller. Lubrication is dry sump, and fuelling is via dual constant velocity carburetors or fully redundant electronic fuel injection. Early ROTAX 912 series engines have a shorter time between overhaul (TBO) than traditional engines but are more fuel efficient than similarly sized engines, e.g., Continental O-200. Effective 14 December 2009, 912 engines have had their recommended TBO raised from 1200 hours to 1500 hours, or 1500 hours to 2000 hours, depending on serial number. In addition to the lower fuel consumption they are certified to run on automotive fuel (mogas) further reducing running costs, especially in areas where leaded AVGAS (AViation GASoline) is not readily available. The engines are popular in Europe and in USA LSA due to high power-to-weight ratio, low fuel costs and relatively quiet operation. There is some demands for the development of diesel aircraft engines, but the scale of application is still at the very low level. But, many air forces would prefer not to use avgas fuel for reciprocating piston engine aircraft. It is not universally available, is expensive and introduces the risk of misfueling. This will presumably lead in the longer term to the acceptance of a new generation of dieselpowered trainers burning avtur (AViation TURbine) fuel. The leaders in this field are the Thielert Aircraft Engines with the 100 kw Centurion 1.7 and SMA with the 170 kw SR Applications for the Centurion 1.7 include the Diamond Aircraft DA40 TD1, which has been ordered for the Lufthansa Flying School. Both engine manufacturers are developing units in the 225 kw class. The main representatives of the piston engine trainer, including LSA, are shown in Table 1. Table 1: Representatives of the piston engine trainer Aircraft Cessna 162 Da 20 EV97 G-120A Lasta Performance Powerplant, kw Length, m Wingspan, m Wing area, m Empty weight, kg Useful load, kg Max.speed, km/h Rate of climb, m/sek Service ceiling, m Take off distance, m Landing distance, m Range, km Price, U$ Combining the use of light alloys and composites the low gross weight of the LSA is achieved. On that way, the possibility of achieving relatively high performances was performed. These performances are comparable with performances of the aircraft with classic piston engines powered by 150 kw class engine. The small weight of the airplane also enabled the use of Ballistic Recovery Systems (BRS), which main part is parachute. It allows the forced landing of the aircraft in the case of engine failure or other critical situations. Heavier piston trainers are equipped with modern ejection/extraction seats which today can be used even in 106

3 this category of trainers. All piston engined trainers are also equipped with the modern avionic systems which were common for more expensive and sophisticated trainers. On that way, we can find some sort of the glass cockpit (a term denoting a cockpit featuring electronic instrument displays) even in the smallest LSA. The main disadvantage of LSA category is the small applicability in terms of syllabus (up to 30 flying hours), according to their flight characteristics. It is noteworthy that military users still prefers classic piston engines, like Continental or Teledyne instead of ROTAX. Some other military users still favors classic piston engined trainers, because they have high ceiling skills (up to 100 hours), and also can be used in the COIN role. This category includes Italian SF.260 and Serbian Lasta. They can also been used as a light combat plane for the COIN (Counterinsurgency) role. Whether aircraft in the primary/basic have a realistic operational capability depends on the local environment. There have been instances in which 150 kw primary trainers have carried out useful ground attack sorties, but these have generally relied on surprise and the absence of effective air defenses. According to the Forecast International [3], market for piston-powered military trainers is dying out and consequently, will account only a small number of aircraft during the next decade. But the market analysis for civil piston engine trainers which can be used in military training centers show different trends. 2. TURBOPROP TRAINERS A turboprop trainer is a trainer powered by turboprop engine. A turboprop engine is a type of turbine engine which drives an aircraft propeller using a reduction gear. The gas turbine is designed specifically for this application, with almost all of its output being used to drive the propeller. The engine's exhaust gases contain little energy compared to a jet engine and play only a minor role in the propulsion of the aircraft. The propeller is coupled to the turbine through a reduction gear that converts the high RPM, low torque output to low RPM, high torque. The propeller itself is normally a constant speed (variable pitch) type similar to that used with larger reciprocating aircraft engines [4]. Turboprop engines are generally used on small subsonic aircraft. Turboprops are very efficient at flight speeds below 390 knots (725 km/h) because the jet velocity of the propeller (and exhaust) is relatively low. Due to the high price of turboprop engines, they are mostly used where high-performance short-takeoff and landing (STOL) capability and efficiency at modest flight speeds are required. The first military turboprop trainers have appeared during 70s, when some of older piston engined trainer has been radically modified. The main reason was rising oil prices and shrinking defense budgets, which forced air forces to review operating costs. The turboprop basic trainer category was pioneered by Switzerland's Pilatus, and subsequent developments have mainly resulted from the company's battles with Brazil's Embraer. The dominant engine throughout has been the Pratt & Whitney Canada (P&WC) PT6A series. During the 80s, new models of real turbprop trainers, (not modified piston trainers) were designed. The first trainer designed from the outset for a turboprop engine was EMB-312 Tucano powered by 560 kw PT6A-25C. Turboprop trainer performances are better than their piston predecessors. More powerful engines in the scope between кw provides higher operational speeds ( km/h), rate of climb (12-20 m/sec) and ceiling of m. Except the more powerful engines, improvements were achieved in the field of aerodynamics, because the whole airframe from the very beginning was designed around turboprop engine. Turboprops can fly with higher G-loads, in wider flight anvelope and use of integrated airbrake provide better speed control. Ejection seats, pressurized cockpit, hydraulic systems, anti-g suits, helmets, Hands on Throttles and Stick system (HOTAS), digital displays, oxygen system, etc. are standard part of the equipment. Rear cockpit is usually raised giving the instructor a better field of view. Turboprop prevails in category of basic flying training, which typically consists of flying hours in a high-powered turboprop with tandem seating. During this phase, students learn such skills as aerobatics, night flying, formation flying and cross-country navigation, i.e. improve some of their skills learnt in the primary phase. It is important to stress that some air forces still use relatively low-powered turboprop which were derived from typical piston engine trainers. This is another way to avoid using avgas in the primary training phase. However, no low-powered turboprop trainer has ever been a major commercial success. Although the Rolls-Royce (formerly Allison) Model 250 is one of the most successful gas turbines ever developed, no trainer with this engine (many of which have flown as prototypes) has sold in big numbers. There may be little interest because the fuel capacity is not increased, but it may also be that trainers in this power category fall awkwardly between the primary and basic training phases. Most prominent representatives of turboprop trainers of today are PC-9M, powered by a PT6A-62 derated to 708 kw and EMB-312 Tucano powered by 560 kw PT6A- 25C or 809 kw TPE331-12B Garret in variant for British RAF. For the US Joint Primary Aircraft Training System (JPATS) competition, an air force/navy programme, the PC-9M competed with the EMB-314 Super Tucano, powered by a 970 kw PT6A-68. In 1995, a modified PC- 9M was selected to be built by Raytheon under license as the T-6A Texan II. The latter differs from the PC-9M in several ways. It has a pressurized cockpit redesigned to accommodate 95% of eligible pilots; Martin-Baker zerozero ejection seats; single-point refueling; improved bird strike resistance; and a Raytheon-patented rudder trim 107

4 device. The engine is a PT6A-68 flat-rated at 1100 kw with a power management system that is modified to simulate the response of a turbofan engine. Although not chosen for JPATS, the Brazilian Air Force (FAB) selected the EMB-314 Super Tucano in 2001 to meet its ALX advanced trainer and light attack requirements. The ALX cockpit is pressurized and its PT6A-68 can be rated at 1195 kw for the attack role and 932 kw for training. It will be built in both single and two-seat forms, with FAB designations A-29 and AT-29 respectively. It can carry 1500 kg of stores on five pylons and is unusual in having two 12.7 mm machine guns mounted inside the wings. In a bold attempt to bridge the basic/advanced phase transition, Pilatus used royalties from the T-6 programme to help fund development of a completely new advanced turboprop trainer: the PC-21. Pilatus intends the PC-21 to perform better than any competitor while retaining life-cycle costs roughly in line with current turboprops, despite having a more powerful engine and ejection seats equivalent to the Eurofighter Typhoon. The PC-21 is powered by a PT6A-68B driving a Hartzell propeller with five graphite blades. Unlike the engines in the T-6A and Super Tucano, it is flat-rated at 800 kw up to 130 km/h and power can be increased in a linear manner to the full 1195 kw at 370 km/h. To provide the widest possible speed range and jet-like handling, the PC- 21 has a relatively short wing span with spoilers, allowing the use of relatively small ailerons and thus long-span Fowler flaps. The result is a stall speed of 148 km/h and a maximum speed of around 600 km/h. By increasing the fuel capacity to allow two consecutive flying training sorties to be made without refueling, the centre of gravity range has extended aft, necessitating a small degree of wing sweepback. To improve on the marginal directional stability of the PC-7 and PC-9, the rear fuselage of the PC-21 has been stretched by 1.5 m. The PC-21 has Pilatus' own yawcompensation system. The cockpit is pressurized and the field-of-view of both pilots benefits from the absence of a front canopy arch. A new trailing-link landing gear has been introduced to allow a higher sink rate at touchdown. One of the basic aims of the PC-21 is to include mission system management training that would normally be carried out on an advanced jet trainer, which Pilatus estimates would have a direct operating cost three to six times higher. External loads totaling up to 1150 kg can be carried on five hardpoints, but stores clearance will be the responsibility of the buyer. One of the latest turboprop trainers is the Korea Aerospace Industries (KAI) KT-1, equipped with a 708 kw PT6A-62A. KAI realize agreement with the Korean Air Force on the procurement of 20 examples of the KO- 1, a forward air control/counter-insurgency variant. According to recent forecasts, more than 1,600 military training aircraft will be produced in the next decade, almost half of which will be turboprop-powered trainers, with jet trainers accounting for nearly all of the remainder. Overall, annual production will reach a high of 150 in 2014 before gradually falling throughout the remainder of the forecast period. Hawker Beechcraft is forecast to lead the market share with 31 percent from 2011 to 2015, although most of these will be made up of T-6B trainers for the US Navy [5]. The market for pistonpowered military trainers is on the decline. The main representatives of the turboprop trainer are shown in Table 2. Table 2: Representatives of the turboprop trainer Aircraft Performanc e Powerplant, kw PC-9 EMB-312 PZL-130 PC-21 KT Length, m Wingspan, m Wing area, m Empty weight, kg Max.speed, km/h Rate of 20.8 climb, m/sek Service ceiling, m Range, km Right because of that, there are several new turboprop models in different developing phases. Some of them are Turkish Hurkus, Argentinean IA-73, Serbian Kobac and German G-120 TP. Amongst the new turboprop designs, as in the case of modernization of older turboprop models, the following trends are noticeable [6]: further engine power increase ( 1200 kw); further increase of flight speed ( 650 km/h), enabled with curved prop tips and application of lightly swept wing; integration of automatically trim devices to compensate torque momentum (auto yaw compensation); power management system that is modified to simulate the response of a turbofan engine; integration of modern flight computers which in combination with FBW controls can simulate different flight characteristics; providing all-through training between the primary trainer and first line combat aircraft with turboprops; cockpit digitalization (color displays, HOTAS system, NVG devices); cockpit embedded simulation (customization of MFD pages, HOTAS functionality and HUD to resemble the 108

5 end user platform, customized synthetic A/A radar with on-board target generation and real time data link for A/A embedded simulation, customized synthetic A/G radar, weapons training A/G + A/A, including stores management); extensive use of ground training aids and devices. 3. COIN DERIVATIVES OF PISTON AND TURBOPROP TRAINER Transformation of conventional conflicts into irregular wars (IW), and so called long wars, changed the conditions in which modern multi-role combat aircraft are used. Their characteristics and high cost make them inappropriate for use in these kinds of conflicts. Arming the forces that participate in the irregular conflicts with this type of aircraft is also difficult and extremely unlikely. By analyzing the experiences of local conflicts that were waged over the past six decades, as well as analysis of the available technological solutions, the majority of expert sources point out that the light turboprop aircraft, which were developed from the training aircraft intended for primary and advanced flight training, can be effectively used in IW such as COIN operations. In the role of close air support (CAS) in COIN operations, an optimal platform would be a turboprop, single-seater plane with flight speeds up to 580 km/h, and the ability to remain in the air at least five hours. In principle, the aircraft weapons consist of 12.7 mm machinegun, 250 kg bombs, and guided and unguided missiles. Companies have accelerated the integration of a greater array of precision guided munitions. In addition to fire support, these aircraft will also be effective for use in basic and advanced flight training, surveillance, monitoring, and forward air control. The main models of light combat aircraft for the close support in COIN operations are A-29 Super Tucano, KA-1, and AT-6B. The Serbian piston aircraft Lasta is less expensive version of the light combat aircraft that can be used in COIN operations [7]. Validity of existing approaches, solutions, and concepts in the development and manufacture of light combat aircraft will be tested during the upcoming decade. On the basis of existing, available resources, it is possible to make assumptions about the basic concepts and ideas of the new light combat aircraft. Arthur Davis, author of a paper on this topic [8], recommends the acquisition of a single engine turboprop aircraft that meets the following characteristics: currently available in the commercial market, ability to loiter for extended periods, short landing and takeoff requirements, the ability to operate from unimproved runways with less chance of foreign object damage (FOD), able to employ a wide range of munitions, a high-quality attack navigation system, a good view from the cockpit, optimal combination of speed and flight maneuverability in medium and low altitudes, and armor for survivability from small arms fire. Development of this principle was based on a list of tactical-technical requirements; additional expert analysis added demands for installation of ejection seats with a protected shell of light alloys, installation of radio communication devices with a wide frequency range and tactical data-link as well defensive systems (chaff and flare dispensers), and a missile approach warning system (MAWS). In addition to meeting the above requirements, the price per flight hour for the aircraft must not exceed $1,000; this is the high-end, and a more realistic price is one far below this threshold. COIN derivatives of turboprop and piston trainer which meet these requirements are the A-29 Super Tucano, the KA-1, American version of Pilatus PC- 9, called the AT-6B (manufactured by Hawker Beechcraft), and the Serbian Lasta (Swallow). A comparison of these aircraft is shown in Table 3. A-29 Super Tucano. The A-29 Super Tucano is derived from the turboprop training aircraft EMB-312 Tucano, with over 650 of these aircraft built for 17 different air forces. Compared to its predecessor, the Super Tucano is more durable, the landing gear is strengthened, and it has an improved wing profile and a redesigned cockpit. The engine is a 1193 kw Pratt and Whitney PT-6A in subvariant 68. The cockpit is manufactured in Israel. It incorporates HOTAS controls, two displays compatible with night vision goggles, two mission computers, Forward Looking Infrared (FLIR), and GPS/INS navigation devices. Equipment includes an aircraft radar warning receiver (RWR), MAWS, chaff and flares, a data recorder, and radio altimeter. Armament consists of two 12.7 mm machine guns located in the wings, gun pod containers with 20 mm, conventional air-bombs Mk81 and Mk82, cluster bomb BLG-252, unguided missiles, and IR guided missile MAA-1 Piranha. On hardpoints, it is also possible to hang a FLIR pod or a laser designator pod. The Brazilian Air Force uses more than 90 Super Tucanos. Their primary purpose is to prevent illegal flight over the Amazon. For this task, the A-29 is continuously linked through data-link with R-99A (EMB-145A), a Brazilian aircraft with Airborne Warning and Control System (AWACS) systems. Loiter time for the A-29 with additional fuel tanks is six and a half hours. In addition to Brazil, other countries either using or having ordered the A-29 include the Dominican Republic, Ecuador, Chile, Guatemala, Columbia, Angola, Burkina Faso, Indonesia, Mauritania and USA. U.S.Air Force has apparently chosen the Super Tucano to meet the Light Air Support (LAS) requirement. Hawker Beechcraft's protest against its exclusion was dismissed. But the contract award was disputed and a stop-work was issued in the January KA-1. The KA-1 is an armed variant of the training aircraft. Its primary purpose is the detection and marking of combat aviation targets (forward air control). In this role, the KA-1 replaces the Cessna O-2. The Korean Air Force has bought twenty KA-1 aircraft, which have a slightly stronger structure and a greater mass in relation to the basic training variant KT-1. The KA-1 has four wingmounted hard points for 12.7 mm machine gun pods, Mk81 and Mk82 bombs, or a seven-barrel rocket launcher type LAU-131. The aircraft is equipped with a mission computer, HUD, INS/GPS system, and a multifunction display. The aircraft is powered by a Pratt and Whitney PT-62A-6A engine, which has a power output of 708 kw. New modifications are underway. The latest version of 109

6 the KA-1 includes FLIR devices, precision-guided munitions, HOTAS controls, and multifunction displays. In this way, the shortcomings of the KT-1 were corrected in the new variants, KA-1 and KT-1C. Loiter time for the KT-1 with maximum fuel is five hours. AT-6B. The AT-6B represents a further development of the American variant of the Pilatus PC-9. The concept of this aircraft was presented for the first time at the Farnborough Fair in Unlike basic training variants of the T-6A and advanced T-6B variants for simulated combat training, the AT-6B is an armed aircraft. In the glass cockpit, there are three lower displays, and one upper, head-up (HUD) display. The cockpit will be protected by Kevlar armor, and a dome for housing sensors will be belly-mounted. Aircraft have six hard points that can carry laser guided bombs, missiles, machinegun pods, and modern air-to-air AIM-9X-type short-range missiles. It is expected that the main advantage of this aircraft, in comparison to its competitors, will be network systems and devices that are based on a network centric concept of warfare. The armed variant aircraft T-6 Texan II may be the ideal aircraft for meeting the previously stated criteria. The AT-6B is the airplane that Hawker Beechcraft offered for the USAF s LAS competition. The LAS requirement includes 20 airplanes, training devices and support for the Afghan National Army Air Corps. The USAF had awarded the LAS contract to Sierra Nevada, which fielded Embraer s Super Tucano for the program. However, in March 2012, the Air Force canceled the contract and said it would issue a new request for proposal, which it did on May The LAS aircraft will naturally be used in that role beginning in Afghanistan, but the USAF has also indicated that there are 27 nations which it would like to have this kind of relationship that would benefit from an airplane like the AT-6. [9] Lasta (Swallow). Unlike its contenders, the Lasta pistonpowered aircraft allows the implementation of the initial selection (ab initio) and basic flight training of pilots and advanced combat training, bearing in mind the integration of machinegun pods, bombs, and unguided rockets. These aircraft, except for training purposes, could be used for small-scale fire support and are especially suitable for designating targets when serving as forward air controllers. Because of their low purchase price and operating cost, the aircraft Lasta could be commercially successful as a subcategory light combat aircraft for COIN operations. The Iraqi Air Force has procured twenty piston-engine aircraft from the Serbian aircraft factory UTVA Panchevo, including an armed variant. The aircraft is equipped with a less powerful piston engine, and because of that, the Lasta does not have the carrying capacity or other combat characteristics of the previously described COIN aircraft. However, the selection of the Lasta by the Iraqi Air Force is very indicative of the fact that the Lasta is almost tenfold cheaper than its competitors. Table 3: Representatives of the COIN turboprop Aircraft Performance Max. engine power, kw КA-1 Т-6B A-29 АТ-802U Lasta Length, m Span, m Wing area, m Empty weight, kg Payload, kg Max. speed, km/h Rate of climb, m/sec Ceiling, m Takeoff runway, m Landing distance, m Range with internal fuel, km Price aircraft mil. $ 4. CONCLUSION Flight training is generally performed in three stages: primary, basic and advanced stage. In every of these stages the adequate training plane is needed. Primary phase or ab initio phase is conducted by the piston engine trainer in different configurations according to their aerodynamical and cockpit configuration. For many decades the lower end in this phase were trainers powered by engine of around 150 kw, with fixed gear and side by side seating. But, the appearance of the new sort of piston engines called ROTAX at the beginning of 90s, and new technologies in the producing of aircrafts, had great impact in application of trainers. Instead of trainers with engines of around 150 kw and gross weight more than 1000 kg, some air forces choose lighter and less powered aircraft which belongs to the LSA category (two-seaters with a maximum weight of 600 kg, a maximum speed of 220 km/h, a stalling speed no greater than 83 km/h, a fixed gear and one non-turbine engine). The application of these trainers regarding to syllabus and skill ceiling is low and these type of trainers are usually followed by turboprop trainers. Some other military users still favors classic piston engined trainers, powered by engine of around 250 kw because they have high ceiling skills (up to 100 hours), and also can be used in the COIN role. 110

7 LSA can use BRS, which allows the parachute helped forced landing of the aircraft in the case of engine failure or other critical situations. Heavier piston trainers are equipped with modern light ejection/extraction seats. All piston engined trainers are also equipped with the modern avionic systems. On that way, we can find some sort of the glass cockpit even in the smallest LSA. At the other hand, turboprop trainer of today prevails in category of basic flying training, which typically consists of flying hours in a high-powered turboprop with tandem seating. During this phase, students learn such skills as aerobatics, night flying, formation flying and cross-country navigation. According to recent forecasts, more than 1600 military training aircraft will be produced in the next decade, almost half of which will be turboprop-powered trainers, with jet trainers accounting for nearly all of the remainder. Overall, annual production will reach a high of 150 in The market for piston-powered military trainers is on the decline. Right because of that, there are several new turboprop models in different developing phases. In modernization and developing process of turboprops following trends are significant: further increases of engine power and flight speed, integration of auto yaw compensation and power management system which can simulate the response of a turbofan engine, cockpit digitalization, cockpit embedded simulation and extensive use of ground training aids and devices. Analyzing the IW, long wars and the experiences of local conflicts, the majority of expert sources point out that the light turboprop aircraft, which were developed from the training aircraft intended for primary and advanced flight training, can be effectively used in IW such as COIN operations. In the role of CAS in COIN operations, an optimal platform would be a turboprop, single-seater plane with flight speeds up to 580 km/h, and the ability to remain in the air at least five hours. In principle, the aircraft weapons consist of 12.7 mm machinegun, 250 kg bombs, and guided and unguided missiles. Companies have accelerated the integration of a greater array of precision guided munitions. In addition to fire support, these aircraft will also be effective for use in basic and advanced flight training, surveillance, monitoring, and forward air control. Validity of existing approaches, solutions, and concepts in the development and manufacture of light combat aircraft will be tested during the upcoming decade. USAF has already indicated that there are 27 nations who would benefit from an airplane like the AT-6 or A-29 Super Tucano. Reference [1] Braybrook, R., Valpolini, P.: Trainer order in prospect, Armada International, 1/2011. [2] Braybrook, R.: Trainers at a Cusp, Armada International, 5/2009. [3] The Market for Military Fixed-Wing Trainer Aircraft , Forecast International, Newtown, USA, [4] [5] Oliver, D.: Asia-Pacific Flight Capabilities and Requirements, Asian Military Review, December 2011/January [6] Vlačić, S.: Izbor varijanti školskog aviona za početnu i osnovnu letačku obuku borbenih pilota, master s thesis, Beograd, [7] Porter, L., Lang, T., Vlacic, S.: Combat Aircraft in Counterinsurgency Operations, JCWS, Norfolk, [8] Davis, A.D.: Back to the Basics: An Aviation Solution to Counterinsurgent Warfare, Air Command and Staff College Wright Flyer Paper No. 23., Air University Press, Maxwell Air Force Base, Alabama, [9] 08/t-6c-chases-trainer-deals-light-attack-6-awaits-usair-force-rethink 111