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Wren Turbines 44i Kerostart Owner's Manual

Model helicopter engine
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Excite your sensors!
Unique, miniature gas turbine two-stage
engine, fully internal automatic starting
(no-gas req'd), kerosene fuelled,
precision gearbox.
Up to 7hp (5.2kw) of output shaft power
up to 20k rpm, for superb performance
in sport, scale or 3D aerobatics.
Gearbox matches OS91H dimensions
and accessories.
Many airframe conversions available.
Wren 44i Kerostart HELICOPTER ENGINE
Owner's Manual
April 2014

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  • Page 1 Up to 7hp (5.2kw) of output shaft power up to 20k rpm, for superb performance in sport, scale or 3D aerobatics. Gearbox matches OS91H dimensions and accessories. Many airframe conversions available. Wren 44i Kerostart HELICOPTER ENGINE Owner’s Manual April 2014...

  • Page 2: Table Of Contents

    Front cover, Ian Erskines beautiful TRex 800, Wren 44Heli power, hmmmmm! WREN 44i Turbine Helicopter Manual Congratulations on your purchase of the latest version of our miniature Wren44 Helicopter gas turbine engine. The new 44”i” means your heli engine now has the Wren kero burner internal to the engine, no pipes or wires to get in the way of your installation! This manual has been prepared to help you set up and safely operate your engine in your airframe.
  • Page 3 Critical components adjacent to hot parts may need protection or spacing away from heat damage by distance or physical protection. An aluminium foil faced insulation material is suitable for wrapping around hot parts of the engine and is available from Wren Turbines if required.

  • Page 4: Introduction

    The Wren 44 Helicopter Turbine Introduction This development from the highly popular Wren 44 Gold thrust engine, has been on sale since 2005. It was built on the success of the Wren 44 Turboprop and uses the same engine and 2 stage components.
  • Page 5 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.
  • Page 6 The Wren 44 Helicopter package contains the following: 1) Wren 44 Heli engine, complete with spacing washer and clutch nut 2) Fuel pump and harness 3) Autostart ECU (Engine Control Unit) 4) ECU data display terminal 5) ECU Battery (2-cell LiPo) 6) Fuel and kero burner solenoids (identical) + “Y”...

  • Page 7: Specifications

    Height – total engine to tip of output shaft – 125mm (5”) Width across exhausts – 160mm (6.3”) Exhaust exit diameter – 45mm (1-3/4”) Shaft nut size 12mm A/F Kerosene burner voltage – 6.5v / 20w Nominal fuel tank for most heli’s, 650-1000cc, 22-34oz (6 to 10mins flying) Performance specifications Practical rpm range –...

  • Page 8: Fuel Consumption

    Fuel Consumption Fuel Consumption Fl/oz to Engine RPM f l / Charts showing the fuel consumption used for the t i o unit in fl.oz/min Engine RPM x 1000 Fuel Consumption in ml/min to Engine RPM 160.0 l / m 120.0 Charts showing the fuel consumption used for the...

  • Page 9: General Description

    General description of the Wren 44 two-shaft drive system The following notes introduce the main parts of the assembly and offer an insight to the use and operation of the unit as a whole; The Wren 44 Helicopter Unit is the world’s smallest commercial 2-shaft helicopter engine. It is designed for use in miniature helicopter applications in place of an I/C engine.
  • Page 10 What is the gearbox arrangement? The gearbox housing is made up of three pieces, the main gearbox body (green), output housing and blanking cap (both gold) in the base. The output housing is not intended to be undone by customers as it is preset with shims for correct gear backlash and loctited, so please do not undo it.
  • Page 11 How do I lock the output shaft to fit my clutch and fan components? To enable the output shaft to be locked for attaching output components, clutch etc, unscrew the lower part of the gearbox using the simple plastic tool supplied. DO NOT attempt to jam the gearbox shaft by sticking a screwdriver or metal rod in between the 2 stage turbine blades –...
  • Page 12 There are several kits for conversions to the popular helicopter airframes. Each has its own method of securing the engine but all are simple and effective. Allowance for heat expansion of the unit should be considered in the mounting. The aim is to eliminate engine movement while attached firmly via the gearbox as this places very high point loads on the hot section coupling point in the centre of the unit and at the gearbox fixings.
  • Page 13 gasoline engine but with very low weight levels allows the operator a level of dial-in performance previously enjoyed by only those operating high performance specialist engines with tuned pipes etc, with all the attendant noise, extreme vibration and operational issues associated with such equipment.
  • Page 14 The Align T-Rex 700 is shown overleaf offered up into the airframe to see how and what modifications are needed. As it turned out, the standard fuel tank with the kit and of good size so was retained. The obvious difference is that though the gearbox is largely modelled on the comparable i/c engine outline the turbine and 2 turbine section is clearly something which has to be accommodated within the fuselage structure itself.
  • Page 15 It is very important however, that users do not change other settings from those set without referring back to Wren Turbines. The ECU is the new V10 Xicoy type supplied by Gaspar Espiell and which the engine, fuel pump and ECU battery plugs into.
  • Page 16 To orientate these servo-type leads, the “-“ refers to the brown wire. There are various timers that are used to keep track of running hours – see the detail section on setting the ECU. Data Terminal The ECU is accessed from the outside world by a port with a three pin servo connector and a hand-held unit called the Data Terminal.
  • Page 17 ALWAYS carefully filter the fuel going into the tank, don’t rely on the pickup to stop particles getting in. If a tank gets badly contaminated then discard it – this engine is far too costly to risk a dirty tank. Be careful also to ensure any tank vents cannot suck grit into the tank. A filter on the air vent is not going too far to keep the fuel pump in tip-top condition.
  • Page 18 Hopper Tanks and UAT’s Hopper tanks and UAT’s (originally the Ultimate Air Trap from BVM Models but others are available now) are a popular choice and can help with continuity of fuel supply – especially on aerobatic or 3D helis. The standard hopper tank is simply a small capacity fuel tank which is fully sealed and has a single fuel-in pipe and a fuel outlet positioned centrally so it can pull fuel from any attitude the heli finds itself in without the possibility of pulling in air.

  • Page 19: Safety Notes

    SAFETY NOTES We make no apologies for positioning these notes early in the manual. Please read the following for your own safety and those around you - thank-you. This engine is not a toy and can cause bodily harm to you or others if misused. It is your responsibility as owner, to ensure safe, careful and considerate operation of your engine at all times, and in accordance with these instructions.
  • Page 20 sudden movement rearwards will at least be limited by the tail rotor. The area sideways on and to the front of the helicopter is potentially the most dangerous area due to the rotating rotor and you will have little notice if the heli suddenly starts to tilt towards you. In certain light a turning rotor blade can become almost invisible –...

  • Page 21: Installation

    It is good practice but not absolutely required to fit a coarse wire mesh at the entrance of this area to prevent buildup of grass, flies etc from clogging the engine intake. An ideal material for this is the high quality stainless mesh available from Wren Turbines at modest cost.
  • Page 22 In all cases, pipe-work used must be of the type supplied by Wren Turbines or an approved turbine supplier. NEVER use silicon (glow type) tube as the fuel and oil will melt it.
  • Page 23 Fire Extinguisher Equip yourself with an appropriate fire fighting extinguisher whenever you are planning to run your engine. The best extinguisher for our purposes is the Carbon Dioxide (CO ) or any gas extinguisher. Use of dry powder, foam or water based extinguishers will cause serious damage to the engine and should only be used as a last resort when there is nothing else.

  • Page 24: Autostart System

    Autostart ECU system The Autostart ECU (Engine Control Unit) supplied with 44 Helicopter engines is a Full Authority Digital Engine Control (FADEC) from Gaspar Espiell. It handles all aspects of starting, operating and shutting down the engine and maintains temperature and operating rpm within safe levels.

  • Page 25: Radio Setup

    Setting up ECU (Engine Control Unit) Remove all rates, mixes and throttle travel settings in the transmitter. The setup assumes the use of a transmitter with manual trims. If you have a transmitter with digital trims see note on previous page. As the display does not photograph well we have reproduced the display readings as a green box.
  • Page 26 Raise PW to 650 for up to 185k rpm, 700 for up to 190k rpm, or 750 up to 195k rpm. Do not raise the setting if you are staying with the 175k rpm limit as it can cause throttle instability. Do not change the values present in your ECU without referring back to Wren Turbines. Wren 44 Gold Helicopter Owners Manual...

  • Page 27: Ecu Failsafe Function

    ECU FAILSAFE FUNCTION The ECU contains a failsafe function that will stop the engine in the event of loss of radio link or continued radio interference that masks the normal signal, but will allow the engine to continue to operate in the case of short glitches. The system works with PCM, PPM and IPD systems. PPM systems In case of loss of radio link, corrupted or signal pulses outside the programmed window of operation, for the first 0.5 secs the FADEC will do nothing and keep the engine at its last valid...
  • Page 28 How does it work – the kero start system? You don’t need to know any of this to run the engine and fly your helicopter but for those who are interested the following may help to explain the kerosene starting process: The kerostart system is basically a form of pre-heating to raise the temperature of the combustion chamber to the point it can vapourise kerosene and make it combust.
  • Page 29 display then shows “FuelRamp”. The fuel pump power keeps rising until the starter is no longer needed (“RPM Off Starter”) and continues until the engine reaches idle at 55,000rpm. All this takes about 25 seconds. Note we have highlighted “Pump Power Ignition Kero” “Pump Start Point”...
  • Page 30 If there are any doubts about the serviceability of the engine and its accessories following such an incident or accidental crash damage the engine must be examined and serviced by Wren Turbines Ltd or their appointed service agent. Wren 44 Gold Helicopter Owners Manual...

  • Page 31: Starting The Engine

    Area Clear? Select a clear area for running – keep clear of areas with loose leaves, sand or other debris that could be picked up or drawn towards the rotors and intake. Turn on the receiver and verify the screen shows a reading. Using the up ”^”...
  • Page 32 If the engine slows down or makes smoke at switchover but keeps going, increase the value “engine min flow” as the flow is not quite high enough to make a successful switchover. At the end of “switchover”, burner turns off at around 20,000rpm, and “fuel ramp” begins. Engine continues accelerating and starter turns off as it passes 30,000rpm.

  • Page 33: Setting A Throttle Curve

    After running After a test start, lower stick and trim to zero for cooling. After landing from a flight, leave the engine for 30 seconds at idle for temperatures to stabilise before returning the trim to off to shut down the engine. ECU will spin engine in short bursts until the temp reading goes below 100’C where it will stop.
  • Page 34 These figures give us our starting point. The best option now is to fly the model and see what sort of head speed the 60% throttle will give at hover point. At mid stick the helicopter should be hovering with a comfortable amount of head speed. The right amount will both sound nice and will make the model feel good in the hover.
  • Page 35 economise and push it too hard. The harder you push your engine the more looking after and service support you will require as the engine and 2 stage will be running hotter. Watch the tail rotor rpms. It is easy to overspeed the tail and burst it when unloading the main rotor after a hefty dose of power so use the best you can get and set up carefully.
  • Page 36 Default settings used in ECU. A Wren supplied kerostart engine will already be adjusted for optimum ECU and pumps settings and should need little or no attention, so do not fiddle with the settings. As the fuel pump wears it may be necessary to adjust settings – see later. Please note, no two installations will be truly identical so do not swap settings with a colleague with a similar engine as they will most likely not be compatible.

  • Page 37: Problem Checklist

    ECU Default Settings, cont. Wren defaults: My supplied settings: RPM fuel ramp kero Preheat fuel Ignition timeout sec’s 24.5 24.5 *Items highlighted adjusted for fine tuning* PLEASE DO NOT TWIDDLE SETTINGS WITHOUT REASON Problem Checklist Symptom Problem Action RX not switched on or RX Verify connection and charge if battery discharged necessary...
  • Page 38 Symptom Problem Action Pump not connected Check wiring ECU display not showing Fuel pump not running See “Starting the engine” “Ready Pump jammed with foreign Investigate operation object Insufficient burner fuel Increase “pump power ignition kero” No or little temp’ rise on Temp’...

  • Page 39: Maintenance

    Check tank system for air leaks/fuel Air in fuel line flow problem Blocked FOD screen (if fitted) Unblock Engine slows or stops Stick may not have been fully Check TX setup during acceleration positioned on setup Tank vent blocked preventing Unblock fuel being supplied Pump battery discharged...

  • Page 40: Storage

    Wren Turbines Limited accepts no liability for any kind of damage which may occur. Wren Turbines Limited assumes no responsibility for any errors contained in this document and is not liable for any damages resulting from such errors.

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