By David Gladwin
(See Photo Slideshow below)
In the past few years, the emergence of ARF (Almost Ready to Fly) models has had a huge effect on the model aircraft scene, in some cases, virtually eliminating building (and associated necessary skills), as well as simple trainers. This is where the ARF trend really started and much more complex models have evolved, mostly from the Far East. The range of models intended for gas turbine power is now very extensive, the quality has constantly improved and is now at a very high level. One Asian manufacturer, PST Jets, which has established a fine reputation for its range of top-quality gas turbine engines, has recently released another in its series of models. This one features an exceptionally high degree of completion, as well as exceptional build quality. . . the model is the PST Reaction.
The Reaction is virtually a finished model requiring very little assembly followed by equipment installation. The fuselage is a glass-fiber molding of very good quality with all formers installed and the wing and stab are of balsa and ply construction with a covering of Herex foam. The skins of the wings, tailplane and fins are manufactured with vacuum-sandwich technology using aircraft-grade Herex C75 lightweight foam insert, which laminates with the outer skin to give exceptional strength. Herex C75 is a closed-cell, moisture-resistant material that ensures consistent bonding strength under changing environmental conditions and time. All surfaces are painted in the mold and can be enhanced by the application of decals to the owner’s choice. PST supplies U.S. stars and bars with the kit
The wings are plug-in using a large alloy tube and the stab and fin are glued into position. I made the tail units removable to ease transport, a modification which is now available from the factory. Virtually everything is included in the airframe kit, but the landing gear is an option, which allows the purchaser to choose his own equipment. PST offers a custom-made set of landing gear to exactly suit the Reaction. Instructions are on CD or can be downloaded from the PST web site (PSTjets.com). The kit does not include the fuel tank, but PST offers a choice of 2.5 or 3.8 liter units; the latter size was installed in the review model.
The Reaction is a licensed-built version of the original design by Bruce Tharpe and is very easy to assemble, great fun and very docile to fly, which makes it suitable for beginners (in gas turbine flying, not to basic RC) right through to expert pilots.
The Reaction is intended for gas turbine power, using engines of between 80 and 130 kilos of thrust; although, 16 kilo thrust engines have been used and the airframe has proven it can handle such power. The big, thick, straight wing of 77 inches-span is completely prefinished, in a choice of colors. The only work required by the builder is to install the precut glass horns (using Hysol) and then install the servos, PST supplying the clevises and pushrods cut to the exact length. Servo holders are precut-ply, requiring the builder to assemble using CA with a fillet of Hysol for strength. For the elevator servo, that is a machine aluminium unit already mounted in the fuselage. Flaps, ailerons and elevator are prehinged using “live” hinging and the rudder uses Robart hinges, the holes being predrilled.
Installation of the retracts is very simple and requires only the drilling of the holes (total 12) to suit the landing gear chosen. Job done! The supplied retracts and wheels are PST’s own and the large wheels, 4 inches in diameter, makes the model very suitable for grass field operation. Brakes are also included.
The fuselage is beautifully molded in two parts, which are bolted together and fit perfectly, with all formers very well installed. The canopy frame is cut to exact size with mounting spigots and catch installed. This requires the builder to only trim the beautifully clear canopy and glue to the frame using Hysol or something similar before installing the cockpit base and a pilot bust.
The fuselage incorporates a metal servo mount for the stab, servo and even the carbon-fiber pushrod is cut to size and predrilled to accept the threaded rods for the clevises. These clevises, Sullivan 4-40, and all other hardware is included with the kit, even the threaded rods being cut to size. Fuel-tank retention is made by the preassembled plywood clips, simple, quick and effective.
The only real construction required for the fuselage is the installation of the engine bearers, trimmed as required to suit the chosen engine, and the application of the lower fuselage and engine bay heat shield, both of these units being supplied and cut to size from litho plate. Installation of the engine requires the drilling of leader holes for just four screws. The engine is angled downwards at almost 20 degrees, which deflects the exhaust gas clear of the rear fuselage and makes inverted flight very easy.
Such is the degree of prefabrication that this model could easily be assembled; there really is no building and it’s ready for gear installation in one day, with an extra day for engine and radio installation. It’s quite possible to make the model ready for the field in a weekend.
The only modification made to the review model was the installation of a removable stab and fin to ease transport problems. This was done using the same BVM components to install the removable fin on the Ultra Bandit; this was the most time-consuming part of the whole assembly, but the PST is now making this available as a factory option, something I would strongly recommend as this is a large model. One further modification was the installation of a small hatch below the nose area to allow access to the ECU battery. Like the receiver batteries, this should be installed as far forward as possible as the model DOES require lead in the nose to balance the aft engine installation. The kit includes a preformed lead noseweight! Apart from these two modifications, nothing was changed on the Reaction and such is the quality of the factory build, there is nothing of significance to criticize, indeed just the opposite, there is much to praise!
The review model has now completed 16 10-minute flights and has proven easy and delightful to fly. The big, thick-sectioned wing allows extremely docile slow-flying characteristics with absolutely NO unpleasant tendencies.
Ground handling with those big, wide wheels is exceptionally good with the brakes working effectively, but not at all harshly. The big wheels make the Reaction very suitable for grass field operation as well as from paved runways. On takeoff, the model tracks well with the rudder and nosewheel steering allowing easy directional control, even in significant crosswinds. Because the main whe
els are rather too far behind the C of G, attempting to unstuck at lowish speeds results in the model pitching sharply, but safely into the air. Very smooth unsticks were achieved by starting the takeoff roll with half up-elevator applied and allowing the model to rotate when it achieved the correct speed. 15 degrees of flap deflection aids these takeoffs, giving a ground roll in light winds of around 75 yards. Directional stability both in the air and on the ground is such that a gyro on rudder and nosewheel steering does not seem necessary.
Once airborne and cleaned up, the Reaction is a complete pleasure to fly. The low wing loading allows very tight turns and loops, both inside and out, with no tendency to flick out and the straight stall is also completely docile. The model simply dropped its nose gently at the stall and resumed flying, no nasty tendencies at all! Roll rate using 3/4 inch of aileron travel is just right and in knife-edge flight, the model shows vey little rolling or pitching tendency. However, if the nose is to be held up for sustained knife-edge, the smallish rudder means that speed should be high, otherwise the nose tends to drop. Tracking during looping maneuvers was excellent and with a little aileron differential, rolls were pleasantly axial. One surprising aspect of the Reaction is inverted flight. Although the model has a semi-symmetrical wing section, when inverted, the model requires just a tiny amount of down-elevator to maintain level flight, probably due to the large downthrust angle of the engine. This, of course, helps keeping the rolls axial.
Attempts to spin and snap the model were unsuccessful and the Reaction just fell into a gentle spiral with pro-spin control and gently rotated during attempted snaps. Perhaps more elevator travel and a more aft C of G may convince the model to spin.
In the circuit, the model was again totally docile. Selecting rear down and various flap selections produced very modest trim changes, just a little “up” trim being required for all three (gear, 15 degrees of flap for takeoff flap and approach, and 60 degrees of flap for landing) selections. Approach speed is very low with any flap selected producing touchdowns at very low speeds and if brakes are used, exceptionally short ground runs resulted, making this model just perfect for short field operations. The glide performance is outstanding and is very flat indeed if the flaps are kept retracted. Flaps increase the glide angle, of course, but even with full flap, 60 degrees, the model still has a very respectable glide performance. If using a large engine, say a 160 (36 pounds of thrust) the model may be fitted with an optional speedbrake to overcome the residual thrust.
- Exceptional build quality and completeness.
- Very fast and easy assembly.(there really is no building required)
- Exceptionally docile handling throughout the flight regime.
- Suitability for wide range of pilot skills.
Radio used: JR 12 X on 2.4GHz .with JR and Spektrum digital servos. Twin Duralite batteries with regulators.
Engine: PST 1300R gas turbine using Jet A1 fuel with 5% turbine oil. Duralite ECU battery.
Model: PST Reaction, fully composite ARF sport jet
Manufacturer: PST Jets (PSTjets.com)
Wingspan 77.6 in.
Length 77 in..
Weight: 24 lb.
Wing area: 1332 sq. in.
Wing Loading: .29 oz./sq in., 2.6 lb./sq. ft.
Radio required. 8 channels minimum.
Engine: Gas turbine from 18 pounds to 36 pounds of thrust (18 to 28 pounds is perfect).
Price: In the U.S., from $1200, plus landing gear, $650.
Distributors: See PST website for distributors outside U.S.
.BTE Engineering, Bruce Tharpe: www.btemodels.com; firstname.lastname@example.org
RCI RC International: www.airworld-usa.com/contact_page.htm; email@example.com
PST California: Ehab: www.pstjets.com; firstname.lastname@example.org
PST Washington: Chuck Bower: email@example.com
PST Texas/Florida: Barry Raborn: firstname.lastname@example.org
PST New York: Len McIntosh: email@example.com