Trends in Military Trainers

Conversely, at the lower end of the performance spec­trum, speeds are increasing. The first stage of the training process is concerned with determining whether the applicant justifies selection for the course. To some extent, this can be established on the ground by physical examinations and psy­chological aptitude tests, but none of these will discover whether he is going to be airsick or can judge heights. The simplest way to weed out the misfits might arguably be to use a 100-150hp light aircraft of the type flown by civilian aero clubs, and indeed some air forces do make use of approved civil schools to carry out the grading process.

However, a number of air forces have found that this ap­proach is misleading. Civilian primary trainers are so easy to fly that they blur the distinctions between the better and worse students. Moreover, an enthusiastic pupil may well have paid for a few hours of prior instruction with acivil club, and thus appear much more promising than he really is. The current trend therefore appears to be toward the use of a more demanding aircraft, despite the higher operating costs that this involves.

Given that the typical military pilot of the future will start his flying training on a relatively high-powered propeller­ aircraft or something at the bottom end of the turbofan range, and will graduate in an aircraft capable of 550 knots at most, the problem now facing the planners is to select the steps by which training may be carried out at minimum overall cost. This means that not only must the cost of producing a successful trainee be minimised, but also that the funds wasted on these students who fail the course must be taken into account.

One way to reduce wastage is to “stream” the students part-way through the syllabus, weeding out those who are unlikely to become fighter pilots (the “fast jet stream” also includes ground attack and tactical reconnaissance pilots) and instead of training them for multi-engined transports, tankers, and bombers, or for helicopters. Some major air forces (notably the USAF) have traditionally been against this approach on the grounds that it produces only inferior graduates for the multi-engined and helicopter streams, but current indications are that these services will eventually be forced to adopt early streaming in order to cut training costs.

Since wastage is high in the earlier phases of the syllabus, it appears logical to start training on an aircraft that is relative­ ly inexpensive to operate. On the other hand, the Soviet and Czech Air Forces are now starting some students directly on the Aero l-39 Albatros, and using this type straight through to operational conversion on the MiG-21 (which is currently also employed for weapons training).

This all-through flying training on a single type arguably represents an extreme reaction against earlier programmes that involved as many as five different aircraft. In general, the high wastage costs of this Warsaw Pact syllabus are not felt to be justified by the engineering economies and the elimina­tion of inter-trainer conversion time that this approach offers.

In the West, the trend appears to be toward the use of a combination of two or three aircraft types to carry, out all phases of flying instruction and basic weapons training. However, new trainer projects are appearing in at least five different categories as a result of the various types of engines available and the differing performance requirements of the operators.

Primary-Basic

A typical present-day military primary trainer has side-by­ side seating and a piston engine in the 200-210hp bracket. Such aircraft include the BAe Bulldog and Saab Supporter, both with 200hp engines, and the NZAI CT-4 and Cessna T-41 Mescalero, each with 210hp. A new aircraft in this category, Finland’s 200hp L-70 Vinka/Miltrainer was shown (not flown) at the Paris Air Show this year. However, with the initial production run of 30 Vinkas for the Finnish Air Force costing around $330,000 a piece, prospects for export sales appear to rely on licence production. The established aircraft in this class sell for approximately $135,000.

The Yalmet aircraft apparently ignores the new trend toward higher-powered engines in primary trainers. Air forces are finding it more cost-effective to carry out a greater part of the syllabus on an inexpensive primary trainer, and are consequently demanding aircraft with more performance and more extensive avionics. One sign of the times is that Switzerland’s AS. 202 Bravo (built by FFA and marketed by Repair AG) began life with a 150hp engine, switched to 180hp as the standard production power plant, and is now being demonstrated with a 260hp engine.

This new AS. 202/26 is probably unique as a modern fixed-gear aircraft with such a powerful engine, and the type may have been stretched too far. The best-known trainer in the 260hp category is the Siai-Marchetti SF. 260M. This retains side-by-side seating and has a retractable gear, but is sometimes argued to be another “hot” for the student, presumably because of its wing loading. A new British contender in this class is the NDN-1 Firecracker developed by Des Norman of Islander fame, and using a much lower wing loading. The Firecracker is aimed primarily at licence manufacture in developing countries since the RAF’s own need for a Bulldog/Jet Provost replacement is still many years away.

However, there are indications that operators want even more powerful aircraft, which will sort out the less promising students very quickly. Some instructors wistfully recall the 445hp CAC Winjeel and the 550hp Provost and T-6 Texan, air­ craft that gave the pupil plenty to cope with, and were dif­ficult to fly really well. However, few would advocate a return to tailwheel undercarriages.

One of the first aircraft in the new 300-400hp primary­ basic trainer class was the 340hp Fuji T-3 (formerly KM-2B), a tandem-seater developed for the JASDF. Earlier 300hp trainers included the Yak-18A and Brazil’s Neiva T-25 Univer­ sal, although both are employed for the second stage of train­ ing, rather than ab initio. Another new 300hp aircraft is the Sequoia, designed by David Thurston, who was responsible for the Lake and Teal amphibians. Intended as a build-it­ yourself military trainer, it is now being sold in kit form in the US. At the upper end of the current piston-engined series, the Neiva Universal II is fitted with a 400hp powerplant.

Both the French and Spanish Air Forces appear to be planning on a new 300hp primary-basic trainer as the lead-in to their turbofan trainers. France’s “Epsilon” requirement is likely to be met by the Aerospatiale TB-30, a tandem-seater with retractable gear and a predicted maximum cruise speed of 190 knots. The Epsilon syllabus of 50-70 hours will include blind flying, IFR navigation, and basic aerobatics.

Spain’s CASA C-102 is proposed for both flying training and liaison duties. It differs from the TB-30 in being a lighter, simpler aircraft with a fixed undercarriage, and in being somewhat later in timescale.

The apparent trend toward engines of 400hp for the first phase of training means that piston engines may be replaced by gas turbines, ie turboprops or turboshafts. Such a move involves far higher flyaway costs, but maintenance costs are reduced, and turbine fuels are cheaper than avgas and have far better worldwide availability. This change also provides an engine that handles much more like the powerplants the student will operate later in his flying career. A turboprop such as the P&W PT6A not only responds in the right way but virtually eliminates the workload associated with propeller control.

The Allison 250 turboprop (as used in the GAF Nomad) provides a direct alternative to the 400hp piston engine. This powerplant is now proposed for the Swiss-AS. 32T project, a tandem-seat, retractable-gear derivative of the piston­ engined FFA Bravo discussed earlier. A maximum cruise speed of 185 knots is predicted.

However, most turboprop trainers are based on the 550shp P&W PT6A, the -25 version of which has its lubrication system modified to permit inverted flight. In the case of the Beech T-34C Turbine Mentor, which is now used by the US Navy for the first 65 hours of pilot training, the engine is flat­ rated at 400shp for longer life. Export T-34C-1s have the full 550shp, as does Switzerland’s Pilatus PC-7 Turbo-Trainer. Both types are based on piston-engined trainers (the T-34B and P-3), whereas Embraer’s proposed EMB-312 would use the same engine in a brand-new airframe, taking advantage of modern construction techniques to reduce weight and cost. The T-34C and PC-7 are generally similar in performance, with a maximum level speed of 230 knots, but the PC-7 is reportedly much better to fly and is significantly more expensive. The in­ dications are that a PC-7 sells for around $800,000, compared to $550,000 for the T-34C-1. Perhaps because of this price difference, the PC-7 has been exported to only four countries (including Burma), whereas the T-34C-1 has been sold to six overseas operators (including the Indonesian Air Force).

The PC-7 and T-34C had been in competition with West Germany’s own Rhein Flugzeugbau ATl-2 Fantrainer 400 for a Luftwaffe order for a new grading aircraft to replace the old Piaggio P. 149D. Using a 429shp Allison 250 turboshaft to drive a ducted fan in the rear fuselage, the Fantrainer is claimed to handle more like a jet than its turboprop competitors.

The ducted fan is certainly less of a danger to the ground crew than a normal propeller, but its thrust appears to fall off very sharply with forward speed, giving a maximum of only 195 knots. The Fantrainer certainly represents far higher development costs than the PC-7 to T-34C, but Germany may well persist with the project, if only because it is rumoured that the USAF favours an uprated version (with 600shp Avco- Lycoming LTP101) as a T-37 replacement. Advocates of Fan-trainers claim that it can be employed for the first 160 hours of flying training, ie two-thirds of a typical syllabus.

Just as the turboprop provides a means to develop an ex­isting piston-engined trainer, some of the new small high­ bypass turbofans intended for executive aircraft give the designer a chance to breathe life into an ageing turbojet air­ craft. Aerospatiale’s private-venture Fouga 90 is a con­ siderably rehashed CM170 Magister, with two Turbomeca Astafan IVGs of 787kg thrust giving a maximum cruise speed of 375 knots. For the French Air Force, the Fouga 90 is ex­pected ultimately to fit between the Epsilon and the Alpha Jet, but smaller air forces may well use it for both primary and basic flying training.

Italy’s Siai-Marchetti is private-venturing a brand-new design, the S211 powered by a P&W JT15D-1 of 1000kg. Despite its modest thrust, the use of a supercritical wing is predicted to give a level speed of 360 knots. A mockup was shown in Paris in June, and the first prototype was to fly in 1981. Marchetti is talking of a price of around $700,000.

In broadly the same category, Gulfstream American is proposing to develop from its Hustler executive aircraft an aircraft to meet future US military training requirements. For the USAF, this Peregrine 600 would have side-by-side seating and probably a single JT15D-5 of 1360kg, while for the US Navy, the aircraft would have tandem seating and two Williams Research WR44s of 545kg each. Maximum speed in either case would be in the region of 390 knots.

Basic-Advanced

At this point in the survey we have arrived at the borderline between those aircraft on which the student could start his flying training and those on which he could graduate to an operational combat aircraft. Designs such as the S211 and Peregrine 600 would traditionally be categorised as basic trainers, but whether they are employed as primary-cum­ basic or basic-cum-advanced trainers is a matter of design emphasis and the individual views of the operator. As it happens, the Peregrine 600 would be used by the US Navy for the second phase of training, the student pilot coming to this aircraft from the T-34C replacement.

Spain’s CASA C-101 Aviojet is an example of a new basic­ advanced trainer built around a turbofan developed for ex­ecutive aircraft. The engine is a Garrett TFE731-2J with 1587kg thrust, giving a maximum speed of 416 knots. One disadvan­tage of the high-bypass engine is that thrust falls off steeply with increasing forward speed, which is probably why the current C-101 is unable to meet US Navy VTX performance requirements. However, such engines are comparatively low in first cost, much quieter than their predecessors, and are certainly modest in their fuel requirements.

The Czech equivalent of the C-101 is the Aero L-39 Albatros, employing the Shevchenko Al-25 as used in the Yak-40 feeder liner, but uprated to 1720kg. As stated earlier, the L-39 is already being used at some Czech and Soviet schools as an all-through trainer. The latest version (L39Z) with four wing pylons and an integral 23mm gun under the front fuselage will allow use in weapon training, although no gunsight is fitted in the rear cockpit. The L-39 is unique in being designed for compatibility with an automatic check-out system and for operation from grass fields and unpaved runways. The Ianding gear doors are therefore closed when the wheels are down, and the intakes are set high on the fuselage to be clear of debris, which also gives them a good clearance from the hot gases produced by the cannon. Maximum speed is a guaranteed 396.5 knots.

Within the Warsaw Pact, Poland has for many years adopted an independent approach to flying training, and is now modernising the TS-11 Iskra with an Al-25 turbofan similar to that of the L-39. However, in this case, the thrust is only 1470kg, as in the M15 agricultural aircraft (now being built in Poland) and the Yak-40.

Italy’s MB326 (as used by the RAAF and 13 other operators) has also been modernised, but in this case by the use of an uprated R-R Viper turbojet of 1815kg, a stronger wing, a new front fuselage with a redesigned cockpit. The maximum speed is 485 knots, and the flyaway price is approximately $3.25m.

Sweden, following a series of defence project cancellations, may well revive the Saab 105 with a pair of tur­bofan engines. The most likely contender is the TFE 1042 of 1930kg, developed by Garrett and Volvo from the TFE731. The Saab 105 is unusual in having side-by-side seating, but this arrangement may yet see a revival in popularity since the USAF is known to prefer it for basic training. The Saab 105, although straight-winged, almost belongs in the top category of trainers, ie that of the swept-wing BAe Hawk and the Dassault-Breguet/Dornier Alpha Jet.

The Hawk and Alpha Jet are broadly similar in perfor­ mance, but the Hawk has a single R-R Adour of 2420kg, while the Alpha Jet has two GRTS Larzacs of 1340kg each. At around $Sm, the Hawk is marginally less expensive than the Alpha Jet, but nonetheless has a longer-lasting structure and a more ad­vanced wing design, giving transonic performance in a dive. This class of aircraft has been described as overkill for RAAF needs since it provides unnecessarily high perfor­ mance and a ground attack capability that the service does not require. On the other hand, this dual-role capability appears essential for success in the export market, and the proliferation of man-portable SAMs has pushed the demand for attack speeds above the 450-knot level. This implies a clean maximum around the 535 knots of the Hawk and Alpha Jet.

To summarise, new military trainer projects appear to be falling into five or six categories. In planning a new flying training program for the late 1980s, Australia is faced with the task, of not only selecting a suitable combination of two aircraft types but of finding new slots in the market. A large number of possibilities exist, but in this writer’s view, one sen­ sible combination would be a primary-basic trainer powered by the 400shp Allison 250 as used in the Nomad, and a basic­ advanced trainer with a military version of the 2500kg RB401 turbofan now being developed as a Viper-replacement for executive jets.