Wren 44 K Helicopter

Wren 44 K Helicopter
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Availability: Delivery (3 - 4 weeks)
Price: $3,932.25 $3,735.64
Ex Tax*: $3,491.25
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*7% Sales Tax is applicable for orders made within the State of Indiana (does not apply to used engines)

Description Specification Related Products (4)

This new development from the highly popular Wren 44 Gold thrust engine stable, has been long awaited. It has built on the success of the Wren 44 Turboprop which has now been on sale since the beginning of 2008. The engine has been the outcome of a long R&D programme primarily concerned with maximising the performance and minimising the aggravation of installing and operating, allowing the flier to get on with the business of flying.

We have been careful to keep the weight of the unit down but have not compromised stiffness, which has shown itself to be a major concern for turbines. The gas turbine is not modified for use in this application apart from a small lubrication port fitted to the case, enabling the full throughput to be used in driving the helicopter rotors, producing performance usually described as “awesome” by all those witnessing it and meaning it is never needed to use maximum power, thus ensuring long life and ease of operation.

The gearbox assembly is strongly built to withstand many hours of operation and is designed for lubrication with a fuel take-off from the engine. All this is automatic and the user need only put fuel (clean!) into the tank, charge battery and go fly!

We have tried hard to produce a compact high power to weight engine capable of filling the gap currently occupied by the noisy and smoky 90’size heli I/C engines and yet keep the package bulk and weight down to allow simple conversion without throwing all the standard parts away. There are a large number of airframes already available in the 15cc (90) size that are attractive for conversion to turbine for the reasons outlined above and are suited for the average club flier to expert flier alike. The low installed weight around 1.5kg compares well with equivalent 2-cycle engines plus tuned pipe and helps to keep the rotor loading sensible.

A major plus factor for this engine is the mountings and output shaft dimensions are exactly mirroring the standard OS91H helicopter engine, therefore any airframe, clutch and fan, designed for this I/C engine will fit onto the 44 Heli engine. The main areas for modification will be the fan shroud and main frames.

Noise is becoming a major concern and the 44 Heli enjoys a remarkably low noise figure, rivalling electric models in many cases. The noise is predominantly rotor noise and a low background whistle, with the smooth application of torque and total absence of power pulses enables a very low perceived noise level to be achieved and which dissipates very quickly with distance. This has major implications for choice of flying site as those in noise sensitive areas will benefit from the absence of 2-stroke 'buzz' associated with normal I/C engined helis.

The Wren 44 Heli enjoys the same highly responsive engine as the Wren 44 Gold thrust version so the absolute minimum throttle lag can be appreciated by those keen on the usual aerobatics and 3D manoeuvres, though we would not pretend the engine can rival the lightning fast response of a racing 2-stroke heli engine, but users will be pleasantly surprised at the enormously wide power band enabling very simple throttle curve programming and flying.

The small engine size (in turbine terms) enables the fuel consumption to be described as 'stingy' so no need for dragging a big fuel tank around like typical turbine heli’s, together with the C-of-G issues this presents. Importantly, the engine is already well established so you are not buying an unproven design. Parts and service is readily available and the hundreds of Wren 44 Gold customers across the world will testify to the longevity and ease of use of this world-beating engine.

Above all – Be Safe and be Wowed!


  • The World's smallest production 2-shaft Helicopter Engine
  • Small physical size – extremely short length enhances install options
  • Integral high quality FOD screen and starter mounting
  • Neat new rotateable, low current kerosene ignitor
  • Solid stainless steel bearing carrier system
  • High precision ceramic bearings
  • Inconel combustion chamber for long service life
  • High quality Anodised case for excellent service life and superb finish
  • 50 hour service interval

WARNING - It is most important that there must always be some load on the output shaft as otherwise the 2nd stage turbine will be running unrestrained and may easily speed up beyond it's safe running speed, even when the gas generator is running at only a modest rpm. The unit should NEVER be run without a suitable load attached.


Max. Power Output 6.8HP / 5Kw @ 190,000 rpm
Weight 1480gms / 3lbs 4oz
Overall size centre section 305mm x 75mm / 12" x 3"
Ancillaries weight (inc battery) 280g / 10oz
Mounting As for OS91 heli engine
Output Shaft Size 3/8" dia + 5/16" UNF (as for OS91H)
Gearbox output shaft rpm range 4,000 to 15,000 rpm
Fuel Consumption @ max thrust 176ml per minute / 5.8oz per minute
Max. Torque 4Nm / 2.9 ft Lbs @ 13,500 rpm