BARNARD MICROSYSTEMS LIMITED

helping you keep an eye on things...

unmanned air ...

engines

Turbine engines

The A.M.T. Pegasus turbine engine  from http://www.amtjets.com/

• AMT of The Netherlands
• Graupner JetCat series
• Wren turbines
• The turbine powered helicopter...
• EADS turbine powered target UAV

AMT Mercury (left) and Pegasus (right) turbine engines from http://www.amtjets.com/

Notes

• S.T.P.  Standard Temp. & Pressure:

• Temp: 15 Degrees Celcius / 59 Degrees Fahrenheit
• Pressure: 1013 Mbar / 29.91 in

• Suitable oils are

• AeroShell  500 (delivered with AMT Netherlands engines)
• AeroShell  560
• Mobil Jet oil II

• Table and notes from http://www.amtjets.com/

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The Graupner JetCat P80 turbine, from http://www.jetcatusa.com/p80.html

• Jet-tronic ECU (fuel control electronics)
• GSU (Display and Programmer)
• LED I/O board
• Miniature fuel pump
• Electronic starting gas valve
• Electronic Fuel valve
• Fuel tubing, tubing connector set, filters, and cable set
• 6 cell, 1250mA battery pack
• Starting gas tank
• Turbine mounting clamp, RamTec compatible
• Detailed instruction manual

P80 thrust chart

The values are approximate and can vary slightly from engine to engine. Values at Standard Temperature and Pressure.

JetCat SPT5 turboprop using a P60 turbine from http://www.jetcatusa.com/spt5.html

Notice the greater thrust for a given fuel consumption for the turbprop engine relative to the turbine engine alone. Data taken from http://www.jetcatusa.com/spt5.html site.

Product information from https://shop.graupner.de/webuerp/servlet/AI?ARTN=6797

Turbine technology offers many advantages, but model aircraft with conventional propeller power systems have never been able to exploit them. Now they can: the Graupner/JetCat SPT5 turbo-prop engine represents a successful combination of high power reserves and High-Tech engineering. In the world of full-size aviation most types of propeller-driven machine have already been converted to turbo-prop power, but the engine´s relentless progress has only just begun in the model arena. As the name indicates, the turbo-prop engine - its full name is a turbo-jet propeller engine - comprises a gas turbine driving an airscrew.

The primary advantages of the turbo-prop in full-size aviation lie in its compact shape and its economy and reliability at speeds below 700 km/hr. The basic design and method of working of the new model engine correspond quite closely to those of the full-size power plants.The principle is very easy to understand: it is simply a matter of finding a suitable method of converting the high power of the turbine engine into usable shaft power. However, this is not necessarily a straightforward matter, especially when you consider the turbine´s very high rotational speed. In the engine presented here the rotational speed is reduced in two stages: the first a gas reduction, the second a geared reduction. This means: when the turbine is running, the gas flow from the core engine drives a turbine wheel which is mounted on a second shaft. This second shaft is mechanically completely independent of the rotor of the base engine and not connected to it it receives its motive power solely from the kinetic energy of the exhaust gas flow.

The secondary shaft directly drives a gearbox designed to cope with high rotational speeds, and this in turn reduces the speed to a value suitable for a propeller. The gearbox is fitted with anintegral axial fan which provides the necessary airflow for cooling the components subject to high temperature. Another completely new feature of the engine is the electronic control system, which processes the speed information derived from both shafts: primary and secondary. This simply means that the pilot can concentrate entirely on flying, while the complex engine management processes are carried out fully electronically. The reduction gearbox is a specially developed planetary design, highly efficient and very compact.

When ever a new kind of power system concept is introduced, the model flyer is obliged to immerse himself in the subject in order to gain the necessary expertise, and this certainly applies to turbines. However, once the operator has become familiar with the procedure, it is actually simpler to handle a turbine installed in a model aircraft than to operate a piston engine: only a single radio control system channel is required to control the engine, and starting preparations for the engine simply boil down to filling the fueltank and a small auxiliary gas tank required to start the turbine.

The engine starts at the press of a button from the transmitter, where upon the entire starting process runs automatically, controlled by the turbine's on-board electronics (ECU). Initially the integral electric motor accelerates the turbine to a speed of around 6000 rpm, then the auxiliary gas supply is opened and the gas is ignited in the turbine's combustor. The turbine then continues to accelerate until the burning gas overtakes the starter motor's speed the motor then disengages, and the turbine continues to accelerate until it reaches a speed high enough to support running on kerosene.

Once the start-up process is completed successfully, the ECU sets a stable idle speed before transferring control to the pilot. After the flight the pilot reduces engine speed in the usual way, then - using the same channel - he initiates the power-down process, which is again entirely automatic, under the control of the on-board electronics: first combustion is halted, then the starter motor is switched on again to push fresh air through the turbine until the internal temperature has fallen to below 100°C. An LED in the model lights up to indicate that this cooling-off phase is complete, at which point the receiving system can safely be switched off.

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Wren SuperSport turbine, from http://www.wrenturbines.co.uk/product.php?pid=4

Wren helicopter engine

Photograph and data from http://wrenturbines.co.uk/product.php?pid=5

The complete system package contains:

• Helicopter Engine
• Autostart ECU
• Hand Data Terminal
• Solenoid valves
• Pump
• Engine mount
• Gas and fuel pipes
• Gas bottle valve
• Gas connector
• Onboard gas tank
• Operator's manual

Price: £ 2,700

Wren turboprop

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The turbine powered helicopter has several advantages:

• electric start
• low vibration level
• high engine power (typically 6 kWatts)

and several problems:

• very high fuel consumption
• noisy
• relatively expensive

The Robbe Nova Cuatro owned by Birger Hovland.

Photograph from http://wrenturbines.co.uk/gallery/show.php?imgid=192&category=0&engine=0&order=datedesc&page=4

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Above and below photographed at the EADS stand at the Dubai 2007 Air Show.

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