GRAUPNER Starlet 50 Instruction Manual

GRAUPNER GmbH & Co. KG D-73230 KIRCHHEIM/TECK GERMANY

Liability for printing errors excluded. ID# 52068 5/04
We reserve the right to introduce modifications

Starlet 50

Model helicopter

Order No. 4445 Kit
Order No. 4446 Complete kit including motor and silencer

Warning!

The contents of this kit can be assembled to produce a working model which is by no
means a harmless plaything. It is a complex flying machine, and if built incorrectly or
handled incompetently or carelessly it can cause serious injury to persons and damage
to property.
You alone are responsible for completing the model correctly and operating it safely.
Please be sure to read the sheets SHW3 and SHW7 which are supplied in the kit. They
include much important safety information, and represent an essential part of these
instructions.

Starlet 50

2

Foreword

The STARLET 50 is a model helicopter of open-frame construction for .50-size engines, based
on the proven UNI-Expert mechanics. The model is of considerable interest to the beginner as a
robust and affordable trainer with unlimited scope for upgrading, but at the same time it will also
suit the more advanced heli flyer with aerobatic ambitions, who is looking for a compact model
with plenty of power reserves. The motor is started from above through the air intake for the
cooling system. The silencer you use depends to a large extent on your individual requirements:
a tuned pipe silencer is one choice, but the model can also accommodate a low-cost standard
silencer and even a super-silencer, and since the recommended motor provides a generous
excess of power this is a perfectly valid option.
With its large-diameter tail rotor the helicopter boasts an excellent tail rotor response, and the
tail rotor continues to be driven in auto-rotations. The high chassis together with the curved tail
boom provides plenty of tail rotor ground clearance; the tail rotor shaft runs through the boom in
a curve and therefore cannot run out of true.
For the beginner the STARLET 50 represents a future-proof investment, as it can be upgraded
directly to UNI-EXPERT mechanics or UNI-mechanics 2000 status; the mechanics can even be
installed directly in many fuselage kits with the existing motor, i.e. without requiring an upgrade
to a .60 engine. The STARLET 50 therefore forms an ideal starting point for a helicopter system
which extends from a small beginner’s machine to a model suitable for the expert or scale
modeller.
The lightweight vacuum-moulded cabin fairing which surrounds the mechanics includes an in­tegral cooling air duct, and is mounted on rubber grommets to provide insulation from vibration;
the fairing can also be fitted and removed very easily, providing complete access to the radio
control system components and mechanics. The fueltank is mounted in the cabin in a clearly
visible location, level with the carburettor, so you can easily check the fuel supply with the model
in the air. The long black eloxided tail boom is supported rigidly by two braces, and can easily
be replaced in just a few minutes if it should be damaged. It is long enough to provide real
flexibility: the beginner can learn to fly using short, low-cost wooden rotor blades with a reflex
section, while the expert can install longer symmetrical-section GRP blades for unlimited „3-D"
aerobatics.

Specification

Length excl. rotor approx. 1310 mm
Width excl. rotor approx. 240 mm
Height approx. 430 mm
Rotor Ø range 1160 ... 1365 mm
All-up weight min. approx. 3300 g

Starlet 50

3

Warnings

•

• •

•

The contents of this kit can be assembled to produce a working model helicopter, but
the model is by no means a harmless plaything. If built incorrectly or handled
incompetently or carelessly it can cause serious injury to persons and damage to
property.

•

• •

•

When the model helicopter’s engine is running, the two rotors are spinning at high
speed and contain an enormous quantity of rotational energy. Anything and
everything that gets into the rotational plane of the rotors is either damaged or
destroyed - and that includes parts of your body. Please take extreme care at all times
with this machine.

•

• •

•

If any object obstructs the rotational plane of the revolving rotors, the rotor blades will
probably be severely damaged as well as the object. Broken parts may fly off and
cause enormous imbalance; the whole helicopter then falls into sympathetic vibration,
you lose control and have no way of predicting what the model will do next.

•

• •

•

You may also lose control if a problem arises in the radio control system, perhaps as
a result of outside interference, component failure or flat or faulty batteries, but in any
case the result is the same: the model helicopter’s response is entirely unpredictable.
Without prior warning it may move off in any direction.

•

• •

•

Helicopters have many parts which are naturally subject to wear, including gearbox
components, motor, ball-links etc., and as a result it is absolutely essential to check
and maintain the model regularly. It is standard practice with full-size aircraft to give
the machine a thorough „pre-flight check" before every flight, and this is equally
important with your model helicopter. Constant checking gives you the opportunity to
detect and correct any faults which may develop before they are serious enough to
cause a crash.

•

• •

•

The kit also includes two further information sheets - SHW 3 and SHW 7 - which
include safety notes and warnings. Please be sure to read them and keep to our
recommendations. They are an essential part of these instructions.

•

• •

•

This helicopter is designed to be constructed and operated by adults, although young
people of 16 years or more may do so under the instruction and supervision of
competent adults.

•

• •

•

The model features sharp points and edges which may cause injury.

•

• •

•

Flying model aircraft is subject to certain legal restrictions, and these must be
observed at all times. For example, you must take out third part insurance, you must
obtain permission to use your intended flying site, and you may have to obtain a
licence to use your radio control system (varies from country to country).

•

• •

•

It is important to transport your model helicopter (e.g. to the flying site) in such a way
that there is no danger of damaging the machine. Particularly vulnerable areas are the
rotor head linkages and the tail rotor generally.

Starlet 50

4

•

• •

•

Controlling a model helicopter successfully is not easy; you will need persistence and
determination to learn the skills, and good hand-eye co-ordination is a pre-condition.

•

• •

•

Before you attempt to fly the model you should study the subject of helicopters in
depth, so that you have a basic understanding of how these machines work. Read
everything you can on the theory of helicopters, and spend as much time as you can
watching other model helicopter pilots flying. Talk to chopper pilots, ask their advice,
and enrol at a specialist model flying school if you need to. Many model shops will
also be prepared to help you.

•

• •

•

Please be sure to read right through these instructions before you start work on the
model. It is important that you clearly understand each individual stage of assembly
and the correct sequence of events before you begin construction.

•

• •

•

Don’t make modifications to the model’s construction by using parts other than those
specifically recommended, unless you are certain of the quality and suitability of
these other parts for the task.

•

• •

•

We have made every effort to point out to you the dangers inherent in operating this
model helicopter. Since neither we, the manufacturer, nor the model shop that sold
you the kit have any influence on the way you build and operate your model, we are
obliged to disclaim any liability in connection with it.

Liability exclusion / Compensation

As manufacturers, we at GRAUPNER are not in a position to influence the way you
assemble your model, nor how you install, operate and maintain the radio control system
components. For this reason we are obliged to deny all liability for loss, damage or costs
which are incurred due to the incompetent or incorrect use and operation of our
products, or which are connected with such operation in any way.
Unless otherwise prescribed by binding law, the obligation of the GRAUPNER company
to pay compensation, regardless of the legal argument employed, is limited to the
invoice value of that quantity of GRAUPNER products which was immediately and
directly involved in the event which caused the damage. This does not apply if
GRAUPNER is found to be subject to unlimited liability according to binding legal
regulation due to deliberate or gross negligence.

Starlet 50

5

Contents

•

Foreword

.........................................

P.2

•

Warnings

.........................................

P.3

•

Accessories, additional items required

....................

P.6

•

1. Assembling the main mechanics

......................

P.7

•

2. Installing the radio control system

.....................

P.21

•

3. Assembling the main rotor head

......................

P.24

•

4. Assembling the tail rotor gearbox

.....................

P.29

•

5. Assembling the control bridge

........................

P.31

•

6. Assembling the tail rotor head

........................

P.32

•

7. Tail boom

.......................................

P.33

•

8. Assembling the skid landing gear

.....................

P.36

•

9. Installing the silencer

..............................

P.36

•

10. Tail rotor control system

...........................

P.36

•

11. Cabin

.........................................

P.37

•

12. Main rotor blades

................................

P.38

•

13. The set-up procedure

.............................

P.39

•

14. Final pre-flight checks

.............................

P.43

•

15. Adjustments during the first flight, blade tracking

..........

P.44

•

Adjusting the motor

...............................

P.45

•

16. General safety measures

...........................

P.46

•

17. Some basic terms used in model helicopter flying

.........

P.47

The instructions

We have invested considerable effort in producing these instructions, with the aim of ensuring
that your model helicopter will fly reliably and safely.
Please take the trouble to follow the instructions step by step, exactly as described, as this is
your guarantee of success. This applies to you whether you are a relative beginner or an
experienced expert.

•

The mechanics have to be assembled as shown in the drawings. Explanatory texts are
provided.

•

All the joints marked with this symbol

need to be secured with thread-lock fluid,
e.g. Order No. 952, or bearing retainer fluid, Order No. 951. Remove all traces of grease
from the joint surfaces before applying the fluid.

•

All bearings, whether plain, ballrace or needle roller, must be lubricated thoroughly. The
same applies to all ball-links and gears, even if the instructions do not state this specifically.

•

You will find parts lists, replacement parts lists and the associated exploded drawings at the
end of this instruction manual.

Starlet 50

6

Accessories

Recommended motors and accessories for the Starlet 50

Motor CapacityccOrder

No.

Expansion silencer Exhaust

manifold

(Tuned pipe)

silencer
OS MAX 46
FX-HG

7,45 1893 1809.33

1871.72

2259 1783A or

2272

OS MAX 50
SX-HG

8,17 1921 1809.33

1871.72

2259 1783A or

2272

Glowplug battery,

e.g.
Varta RSH 4 Order No. 1353
Varta RSH 7 Order No. 1352
2 V glowplug battery Order No. 3694 ( Use only with resistor,
2 V glowplug battery Order No. 771 Order No.1685 or 1694. )

Fuel

TITAN S 12 Order No. 2612
AeroSynth COMPETITION SX-10 Order No. 2811

Starter

Electric starter, Order No. 1628 or 1626
12 V starter battery, Order No. 2592 or 2593.

Suitable main rotor blades

Order No. 1291.1 Wood, reflex, 500 mm long Rotor Ø 1157 mm (supplied)
Order No. 1296 GRP, reflex, 552 mm long Rotor Ø 1261 mm
Order No. 1269 GRP, symm., 552 mm long Rotor Ø 1261 mm
Order No. 1271 GRP, symm., 602 mm long Rotor Ø 1361 mm

Radio control equipment: see main Graupner catalogue

We recommend that you use a radio control system equipped with special helicopter functions,
or a micro-computer radio control system such as the mc-12, mc-14, mc-15, mc-19, mc-22, mc-

24.

As a minimum your RC system must include a 3-point swashplate mixer and the ability to
control five servos for the functions pitch-axis, roll, collective pitch, tail rotor and
throttle.

Servos

:

Use only high-performance

servos

such as the C 4041, Order No. 3916, or other servos of

equal or better quality.

Gyrosystem

:
Gyro-System PIEZO 5000, Order No. 5146 with Super-Servo DS-8700G, Order No. 5156 or
Gyro-System PIEZO 550, Order No. 5147 or Gyro-System G490T, Order No. 5137

Electronic speed governor:

mc-HELI-CONTROL, Order No. 3286

Receiver power supply

:
For safety reasons we recommend that you install a battery with a capacity of at least 1800
mAh, and a switch harness designed to cope with heavy currents, i.e. with heavy-duty cables.
We recommend the “Power switch harness“ with charge socket, Order No. 3050, in conjunction
with the 4RC-3000 MH receiver battery, Order No. 2568

On no account use a receiver battery with more than four cells.

You can monitor the state of your battery voltage constantly by using the NC battery controller,
Order No. 3138.

Starlet 50

7

1. Assembling the main mechanics

The mechanical system of the STARLET 50 is based primarily on parts moulded in glass-fibre
reinforced nylon, a material which offers significant advantages for use in model helicopters
compared with aluminium, including high mass constancy combined with light weight, freedom
from fatigue effects, low noise, and the ability to absorb vibration generated by the motor. The
design of this type of mechanical system imparts a generous degree of robustness and rigidity;
in a „hard landing" the ideal situation is that the parts either survive undamaged (and can
therefore be re-used immediately) or alternatively fail completely, in which case there is no
doubt about whether they have to be replaced. Aluminium chassis components tend to bend or
become distorted, and this kind of subtle damage may not even be noticed; however, in the long
term it causes damage to other components, has a negative effect on the model’s flying
characteristics, and can even have a serious effect on the safety of the whole system. The type
of construction used in the Starlet 50 is simply not subject to this kind of damage.
Glass-filled nylon components therefore have many advantages, and the only drawbacks are
their greater complexity, and therefore higher cost of manufacture, and the requirement they
place on the builder to assemble and adjust the parts with greater care and a conscientious ap­proach; you may also find that some parts need to be trimmed slightly in order to obtain a per­fect fit. Provided that you invest a little extra care in constructing your machine, you will be re­warded by a model in which rates of wear are low, and which lasts much longer than conven­tional model helicopters.

Shafts, bearings, fits

Virtually all the rotating parts of the mechanics are ballraced. Wherever ballraces are used, it is
very important that the shaft is a tight fit in the inner ring of the bearing. This ensures that it
cannot rotate inside the ring; if this happens, the inner ring heats up (causing a blu-ish or yellow­ish discoloration), and the bearing is damaged and becomes unserviceable. In the worst case
the bearing can become so hot that it melts the nylon bearing seat, and this destroys the correct
location of the shaft relative to other components. Please note that this kind of damage is simply
a result of an incorrectly fitted bearing, and is not an indication that the bearing support material
is not up to the job.
A loosely fitted bearing can also cause another problem: the shaft starts to move axially inside
the inner bearing ring, and the shaft wears in that area and its diameter is reduced. If there are
gears mounted on that shaft, they now lose their correct meshing clearance, leading in turn to
increased rates of wear, and eventual failure of the parts.
In order to prevent the problems described above, the fits between shafts and ballraces in the
Graupner/Heim system are maintained on the „close" side of normal, and now and then this can
result in too tight a fit if manufacturing tolerances accumulate in the same direction. This
manifests itself in a bearing which cannot be fitted onto the corresponding shaft. If this should
happen, just reduce the diameter of the shaft slightly by rubbing it down using fine wet-and-dry
paper (600 - 1200 grit), until the bearing can be pushed into place using no more than moderate
force. If manufacturing tolerances accumulate in the other direction, i.e. the fit is uncomfortably
free or too loose, the solution is to fix the bearing to the shaft using LOCTITE 603 bearing
retainer fluid, which guarantees a firm seating. If you use this fluid, please note that its cure time
varies according to the fit; the closer the fit, the faster the cure. Under certain circumstances you
may have only a few seconds to locate the bearing correctly on the shaft before it is fixed
permanently.
If a shaft is supported in two or more bearings, it is important to ensure that the location of the
bearings does not place axial stress on them. There are two ways of achieving this: you can
either take the trouble to position the two bearings really accurately on the shaft, or use a com­bination of a fixed and sliding fit: one bearing is pressed or glued to the shaft to locate it per­manently, the other is left as a sliding fit, i.e. it can be moved axially along the shaft using
moderate force; in this case the second bearing will find its own optimum position once the
system has been installed.
In general terms you can assume that the danger of bearings slipping on the shaft varies with
shaft diameter and rotational speed: the smaller the shaft, and the higher the speed, the greater
the danger.
The danger of stress in multiple bearings is greater when the difference between the internal
and external diameters of the bearings is small.
If you are aiming to achieve maximum possible operational security and reliability, all these
factors have to be considered in each individual case. The building instructions for the Starlet 50
state which connections should be made using thread-lock fluid and/or bearing retainer fluid.

Starlet 50

8

1.1 Assembling the tail rotor drive system

(bag UM-1A

)

Please note that there must be no axial play at all in the quick-release coupling shaft 4618.57
when fitted in the bearings 4618.6. If the shaft does not seat securely enough in the bearings, fix
it to the bearings using bearing retainer fluid 603, Order No. 951. This is the procedure: first fit
the rear bearing on the shaft and secure it with a drop of bearing retainer fluid 603, and position
it so that it rests against the coupling yoke. Wait until the adhesive has cured; this may take
anything from 20 seconds to 30 minutes, depending on the closeness of the fit. Press this
assembly into the bearing holder 4448.14 as far as it will go, then slide the front bearing onto
the shaft, together with a drop of bearing retainer fluid 603. Slide the bearing straight into the
correct position, and press it into the bearing holder as far as it will go. Now - before the adhe­sive sets - check that the shaft is still free-moving; it is important that the bearings should not be
stiff; this is usually due to excessive axial stress. If this happens, tap lightly on the end of the
shaft in the axial direction, using a screwdriver handle or similar, or tap harder on the bearing
support, until the bearings ease into the correct position and the shaft turns freely. Now allow
the bearing retainer fluid to cure fully.
Fit a shim washer and the pinion 4450.41 on the front end of the shaft, press it against the front
bearing and secure the pinion in this position using two grubscrews: first apply a drop of thread­lock fluid (Order No. 952) to the threaded hole and fit the first grubscrew, taking care to position
the pinion so that the screw engages on the flat machined in the shaft. Rotate the pinion to and
fro on the shaft so that the grubscrew takes up the optimum position, then tighten it moderately.
Now screw in the opposed grubscrew and tighten it very firmly before finally tightening the first
grubscrew permanently. This procedure ensures that the pinion runs really true on the shaft.

1.2 Assembling the layshaft

(bag UM-1B)

Fix the bottom bearing 4450.31 for the layshaft 4450.7 on the shaft, using bearing retainer fluid
603, Order No. 951. Position the bearing resting against the pinion, then leave the fluid to cure.
Press the shaft and bearing into the bottom bearing support 4448.11.

Starlet 50

9

Fit the top bearing support on the shaft loosely for the moment (note the correct orientation; the
opening in this bearing support should face up), then fit the top bearing 4450.31, followed by a
shim washer. Press the freewheel sleeve 4618.107 into the gear 4618.105, and fit this assembly
on the shaft. Line up the cross-holes in the shaft and the freewheel sleeve and carefully press
the roll-pin 4618.65 into the holes, but only to the point where it projects a little way into the
shaft; it must be possible to pull it out again at this stage.

Now press the top bearing 4450.31 into the bearing support 4448.11 and push this assembly up
against the shim washer under the freewheel sleeve. Take the layshaft assembly which you
have assembled to this stage, and place it between the mechanics side frames 4450.9 and

4450.10, so that you can check that the top bearing rests against the freewheel sleeve above
the shim washer when the parts are assembled. You may find that there is a gap, which has to
be corrected by fitting additional shim washers. Take care not to fit too many shim washers, as
this would place the bearings under stress.

Once you are confident that the spacing is set correctly, glue the shaft to the bearing in the
usual way using bearing retainer fluid, Order No. 951, but only after you have pressed the roll­pin into the freewheel sleeve fully and permanently. Fit this assembly between the mechanics
side frames and tighten the screws fully before the bearing retainer fluid has cured, so that you
can check that the shaft spins freely in its bearings. If it is slightly stiff, tap on the ends of the
shaft to seat the bearings and eliminate the problem.

Starlet 50

10

1.3 Preparing the main rotor shaft and bearings

(bag UM-1C)

Fix the swashplate guide 4618.113 to the dome bearing holder 4448.8 using two M2 x 12
cheesehead screws. Press one of the ballraces 4450.24 into the dome bearing holder, and one
into the main rotor shaft bearing holder 4448.12; grease both bearings.

The next step is to slide the circlip 4607.156 along the main rotor shaft 4450.43 from the top,
and allow it to engage in the channel. Please note the following points here:

•

The circlip must not be over-stressed, i.e. take care not to open it further than absolutely
necessary in order to slide it onto the main rotor shaft. Special circlip pliers are the best tool
for this job.

•

The inner face of the circlip features one rounded and one sharp edge; the sharp side must
face up.

•

The circlip must be a really tight fit on the shaft; it should not be possible to rotate it by hand.

Starlet 50

11

1.4 Assembling the main gearbox

Fit the tail rotor drive unit, the layshaft assembly and the main rotor shaft bearing holders
between the mechanics side frames 4450.9 and 4450.10, and fix them in place using M3 x 16
socket-head cap screws; don’t tighten the screws fully at this stage. Fit a shim washer 4450.40
and the dome bearing holder on the main rotor shaft from the underside. Slide the main rotor
shaft through the bottom rotor shaft bearing and the crown gear 4450.20A, working from the top,
and position it in such a way that the dowel pin 4450.37 can be pushed through the bottom hole
in the main rotor shaft. Now pull the main rotor shaft up as far as it will go, and check that the
dowel pin engages fully in the recess in the underside of the crown gear. Now you can fix the
dome bearing holder between the mechanics side frames using further M3 x 16 socket-head
cap screws, and check that there is absolutely no axial play in the main rotor shaft between the
bearings; if there is, fit further shim washers under the circlip to eliminate it. Take care not to fit
too many or too thick washers, as this could place the bearings under stress.

To add or remove shim washers always loosen the dome bearing and remove the main
rotor shaft by reversing the order of operations required to install it (see above). On no
account remove the circlip to gain access to the washers!

The first step in establishing the correct gearbox clearance is to set the meshing clearance of
this gearbox stage slightly too tight, i.e. the gears should mesh „hard" against each other. If this
is not the case, i.e. if there is already significant clearance between the gears after you have
assembled the main mechanical system and screwed the parts together, then you will have to
turn the bottom main rotor shaft bearing 4448.12 through 180° and re-install it. If that is still not

Starlet 50

12

sufficient to eliminate the gear clearance, you will also have to turn the bottom layshaft bearing
bracket through 180° horizontally. Turning these parts round in this way compensates for any
slight offset of the brass inserts in the bearing supports; such offsets are an inevitable feature of
the production process and can never be completely eliminated. The meshing clearance
between the spur gear and the layshaft pinion can now be adjusted by slightly loosening the M3
x 16 socket-head cap screws in the bearing brackets, fitting a strip of stout writing paper
between the gears, and then tightening the screws again, holding the gears hard against each
other. Wind the strip of paper out, and the gearbox should now run smoothly, with no tendency
to jam or stiffen at any point; if you are not satisfied, repeat the adjustment process with a little
greater care.

1.5 Installing the motor

(bag UM-2)

The mechanical assembly of this helicopter is designed for a motor with a long ground 8 mm Ø
crankshaft, as specified for all Graupner / Heim model helicopters. However, other types of
motor can also be installed at the modeller’s discretion; all you need is the optional plain bearing
clutch, which is available separately.
Remove the washers and nut from the crankshaft, then fit the following parts on the shaft in this
order: stepped washer 4450.38, two ballraces 4618.78, split taper collet 4618.77, clutch bell

4618.23, clutch 4618.79, cooling fan 4450.2, followed by the washer supplied with the motor. Fit
the crankshaft nut and tighten it securely.
If you find that tightening the crankshaft nut pushes the taper collet completely inside the clutch,
without the collet exerting adequate clamping pressure on the crankshaft, then you must fit an
8/13 x 0.5 mm washer (from 4450.58) under the taper collet, otherwise the clutch may slip on
the crankshaft when the motor is running. Fix a linkage ball to the outermost hole in the
carburettor arm using an M2 x 10 screw and nut.

Starlet 50

13

Notes:

Power transference between crankshaft and clutch is achieved exclusively by the clamping
pressure of the taper collet on the ground crankshaft nose, and on the tapered socket in the
clutch. To ensure that sufficient pressure is applied, it has proved good practice to start by
installing the clutch alone - without the cooling fan - and tightening it fully; the clutch should be
held firmly using a suitable tool while you do this.

When attaching the clutch bell to the crankshaft it is essential to ensure that the shaft is not
pushed out of position in its bearings!

Once you have fitted the clutch and tightened it correctly, the only way to remove it again is to
use a puller mechanism (Order No. 1045), after removing the crankshaft nut. Note that the
tightness of the crankshaft nut makes no significant contribution to power transmission when the
motor is running; the nut’s primary purpose is to secure the cooling fan and, if used, the
hexagon starter cone (optional part, Order No. 4448.103).

Starlet 50

14

Fix the motor mounts 1291.18 to the top part of the mechanics using the two special M3 x 12
screws, working from the inside of the assembly. Attach the motor to the motor mounts using
four M3 x 16 socket-head cap screws, fitting a washer 560.7 on each screw between the motor
lugs and the motor mounts (see drawing).

Starlet 50

15

1.6 Assembling the cooling fan housing

(bag UM-3)

You may find that you have to open up the carburettor opening in the fan housing, depending on
the type of carburettor you are using; the same applies to the hole for the cylinder head.
Fit the fan housing over the motor and fix it to the mechanics using a threaded rod 4618.151,
washers and nuts at the front, and two 2.9 x 16 mm self-tapping screws at the rear.

Starlet 50

16

1.7 Assembling the sub-structure

(bag UM-4)

Assemble the sub-structure as shown in the illustration, using the side frames 4448.34, the
bulkhead 4450.18, the spacers 4450.17, the RC box 4445.101 and the skid brackets 1291.21A,
using the appropriate self-tapping screws, as shown in the drawing.

Starlet 50

17

1.8 Mounting the mechanics on the sub-structure

(bag UM-5)

Fit the circular projections on the main gearbox (assembled in Section 1.6) between the side
frames of the sub-structure, and allow them to engage in the moulded-in sockets. Fix the parts
together using M3 x 16 socket-head cap screws and washers as shown.

Note that two M3 x 30 socket-head cap screws are used in the middle; fit a washer under each
screw head, fit the brass sleeves 4450.34A in the sub-structure side frames, and fit the screws
through the two spacer washers 4445.34 and into the mechanics side frames. When you tighten
these screws, the ends will project through the bottom motor mount screw holes. Fit M3 self­locking nuts on the projecting shanks to secure the motor mounts.

The next step is to set the proper meshing clearance in the first gearbox stage: loosen the M3 x
16 screws which attach the top layshaft bearing support to the side frames, and also the M3
self-locking nuts at the bottom of the motor mounts, then cut a strip of thin card and wind it in
between the clutch pinion and the gear. Hold the gears firmly together, and tighten all the
screws again firmly in this condition. Apply plenty of thread-lock fluid to the M3 screws in the
motor mounts before you tighten them. Wind the strip of paper out from between the gears, and
the entire gearbox should now rotate freely; note that there should be no detectable play where
the bevel gear engages with the crown gear.

Starlet 50

18

1.9 Glowplug connector

(bag UM-6)

Fit the socket of the glowplug connector in the hole in the right-hand side frame 4448.34, and fit
the solder tag, the washer and the nut on it on the inside to secure the socket. Tighten the nut.
Make up the connection to the motor using twin-core cable. A crocodile clip is used for the
centre contact, so that the glowplug can be replaced quickly and easily; solder the croc-clip to
the wire running from the centre contact of the socket, and attach the clip to the glowplug. Fix
the other wire to one of the motor mount screws with a washer to spread the load. Arrange the
cables neatly, and solder the two wires to the positive and negative terminals of the socket.

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1.10 Fueltank

The fueltank is assembled as shown in the drawing. First install the pressure nipple in the small
raised area at the highest point in the tank: cut a 5 mm Ø hole, slip the nipple through it from the
inside, and secure it with the washer and nut on the outside. The rubber bung features a central
hole for the retaining screw, two through-holes for brass tubes, and a third „blind" hole. The
latter can easily be continued through the bung and used for other purposes if you wish. For this
model only a single fuel line is required (carburettor feed / filler tube), so the second hole should
be plugged with a length of brass rod (4618.15). Bend the feed tube to the shape shown in the
drawing. Ensure that the clunk weight is free to move inside the tank, i.e. that it always falls to
the bottom when the tank is turned over by hand. Fit the brass collar over the neck of the
fueltank, as it guarantees that the neck cannot split when the rubber bung is compressed.
Tighten the central retaining screw firmly once the fueltank is completely assembled. This action
compresses the rubber bung and causes it to swell laterally, sealing the throat of the tank
effectively.
Carefully remove any rough edges from the fueltank support surfaces at the side-frames, Order
No. 4448.34. Install the tank, and secure it by stretching rubber bands over it as shown; note
that the bung must face the rear. Make up the fuel line to the motor using fuel tubing and the
fuel filter T-piece; keep the connection to the carburettor as short as possible.
The tank is filled and drained by means of the fuel line running between the clunk pick-up and
the carburettor, and this is made easier by the presence of the fuel filter T-piece. For flying the
helicopter, push the sealing plug into the filler connection projecting from the side of the filter.
For filling or draining the tank, first cut off the fuel flow to the carburettor by engaging the hose
clip, then fill or empty the tank through the filler connection.

1.11 Installing the gyro platform

(bag UM-7)

Fix the gyro platform holders 4450.16 to the side frames using 2.2 x 9.5 mm self-tapping
screws. At a later stage the gyro platform 1291.12 can be fixed to the supports using four 2.2 x

6.5 mm self-tapping screws, but only after the servos have been installed.

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1.12 Collective pitch compensator and swashplate

(bag UM-8)

The collective pitch compensator 4618.47A is assembled as shown in the drawing.

First fit a circlip on each of the brass rods, and glue them in the holes in the collective pitch
compensator hub 4618.46 using bearing retainer fluid, ensuring that the circlips engage fully in
the recesses. De-burr the collective pitch compensator arms and slip them on the projecting
ends of the brass rods, fitting at least one shim washer between the hub and the arm in each
case. Note that the arms must be free to rotate on the rods; de-burr the holes if necessary. Fit
the outer circlips, and check that there is no axial play in the arms on the rods; if there is
detectable play, extra shim washers must be fitted.

Make up three pushrods as shown in the drawing, using the threaded rods 4618.51 (2 mm Ø,
75 mm long) and six ball-links 4618.55. The stated dimension refers to the actual clearance
between the ball-links, as shown.

The first pushrod is fitted to the rear linkage point on the swashplate. Slip the ball-link over the
guide pin on the swashplate 4682.45 and snap it onto the linkage ball. Now fit the brass sleeve
(from 4618.113) onto the guide pin and grease it well. Slip the swashplate onto the main rotor
shaft, routing the attached pushrod down through the opening behind the dome bearing holder;
at the same time carefully ease the swashplate guide 4618.113 back, so that the brass sleeve
on the swashplate guide pin engages in the channel in the swashplate guide.
Fit the collective pitch compensator on the main rotor shaft, and press the two ball-links onto the
appropriate linkage balls on the swashplate inner ring, as shown in the drawing.

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21

2. Installing the radio control system

(bag UM-9)

2.1 Mounting the servos

Attach brass linkage balls

to the inside

of the pitch-axis servo arm (1), and the output arms of
the roll servos (2) + (3), using M2 x 10 screws, and secure them with M2 nuts on the outside.
Apply thread-lock fluid between screw and ball and also in the nut. The distance from the servo
output shaft axis to the ball centre should be about 18 mm. The first servo to be installed is the
pitch-axis servo, which should be placed in the servo aperture in the right-hand side frame from
the inside, with the output shaft at the top. Secure it with four screws, rubber grommets and
tubular metal spacers (these parts supplied with the servos). Note that the tubular spacers
should be fitted in the rubber grommets from the underside, and the screws fitted from the top.

The servo mounting holes in the mechanics are intentionally offset slightly towards the outside;
this places the rubber grommets under slight tension when the screws are fitted, and this in turn
improves overall control precision.

Install the roll servos in the right and left side frames from the outside, with their output shafts
also at the top (see drawing). Secure each with four screws as already described. Connect the
servos to the receiver in the sequence explained in the RC system instructions, then switch on
the RC system and activate the swashplate mixer at the transmitter (setting: symmetrical three­point linkage, two roll servos, 1 pitch-axis servo at the rear). Set the collective pitch, pitch-axis
and roll controls to neutral, and fit the output arms on the servos, at right-angles to the rotor
shaft. Fit and tighten the output arm retaining screws.

The tail rotor servo can now be installed in the left-hand side frame from the outside, with the
output shaft again at the top. Fit the retaining screws. The servo output arm should point straight
down, and should be parallel to the main rotor shaft when the collective pitch stick is at centre.
Fix a brass linkage ball

to the outside

of the throttle servo output arm, and secure it with an M2 x
10 screw, secured with an M2 nut from the rear. Remember to apply thread-lock fluid between
screw and ball and also in the nut. The distance from the output shaft axis to the ball centre
should be about 11 mm. Mount the throttle servo in the left-hand side frame with the output
shaft at the top and the servo output arm facing up.
The servo leads can now be routed through the remaining vacant servo aperture at the front of
the right-hand side frame, and routed forward along the right-hand side of the mechanics to the
receiver. Bundle the wires together in spiral tubing. Please take great care when deploying the
servo leads; eliminate any chance of wires contacting shafts or gears, as the model could easily
crash if the wires chafe and rub through.

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The next stage is to link the swashplate servos to the swashplate using the pushrods already
prepared, to form a 120° linkage.

A four-point swashplate linkage is also possible; details of this alternative installation are left up
to the builder. In this case one further servo is installed in the vacant servo aperture in the
mechanics, and connected to the appropriate linkage point on the swashplate by means of a 2.5
mm Ø pushrod, which has to be angled to suit. The pushrods from servos 2 and 3 are then
connected to the lateral (90°) linkage points on the swashplate. You will need to activate a four­point swashplate mixer at the transmitter.
If you decide to install a four-point linkage, it is very important to adjust the pushrods really
accurately, otherwise the opposed servos may be under constant strain. This is the procedure:
switch on the radio control system and set the collective pitch stick to centre (servo output arms
at 90° to the pushrods). Disconnect one swashplate pushrod. Adjust the three remaining
pushrods until the swashplate is exactly horizontal. The length of the fourth pushrod should now
be adjusted very carefully so that it can be pressed onto the swashplate linkage ball without
moving it, i.e. without straining any other servo.

Make up the throttle pushrod as shown in the drawing, using the threaded rod 4445.84 (2 mm
Ø, 45 mm long) and two ball-links 4618.55; the stated dimension refers to the actual clearance
between the ball-links.

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23

Connect the carburettor arm to the throttle servo output arm using this pushrod, as shown in the
drawings:

2.2 Installing the remaining radio control system components

To attach the gyro system to the gyro platform we recommend the use of double-sided foam
tape, e.g. Order No. 742. The cables should be grouped with the servo leads and routed
forward along the side of the mechanics to the receiver.

Pack the receiver battery in foam rubber, with the receiver above it, and stow these components
in the RC box, where they are secured with rubber bands. Note that the receiver sockets should
be on the right-hand side, so that the servo cables can be plugged in directly, without the need
for extension leads.

Bundle the cables together with spiral tubing, and attach them to the mechanics using cable
ties. It is important that the wires are not under stress, make no contact with rotating parts, and
do not rub or chafe against any sharp edges or corners.

Install the receiving system switch on the switch console, which is screwed to the right-hand
side of the sub-structure. Connect the switch to the battery and receiver in the usual way.

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24

3. Assembling the main rotor head

(bag UM-10)

The main rotor head is assembled as shown in the illustrations. All ballraces must be greased.

3.1 Preparing the blade holders

The first step is to glue the brass sleeves from 4618.32 to the M3 x 16 screws using thread-lock
fluid. Allow the fluid to cure. Check that the mixer levers 4618.32 swivel freely on the brass
sleeves; if not, remove any rough edges from the mixer lever bores, and lubricate with silicone
oil. The mixer levers are screwed in place using the M3 nuts.

Press the radial bearings 4607.31 and the shell of the combination bearings 1254.13 into the
blade holders 1252.11 as shown in the drawing. Push them in as far as they will go.

Now check that the prepared blade holders, complete with the bearings 4607.31, can be slid
easily onto the blade pivot shaft 4607.29. If necessary, rub down the blade pivot shaft with fine
abrasive paper (600-grit or finer) until the bearings are a sliding fit on the shaft.

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25

3.2 Installing the blade holders

Press the two O-rings 4607.28 into both sides of the rotor head hub 4682.26, grease the blade
pivot shaft and slide it through the O-rings. Set it exactly central, i.e. projecting by an equal
amount on both sides. It is important that the shaft does not push the O-rings out of their
seatings. Now hold this assembly with the blade pivot shaft standing vertical. Fit a 0.2 mm shim
washer from 4450.56 on the shaft from the top, followed by a blade holder, noting that the
holder must be the correct way round: the mixer lever on the blade pitch arm must be located in
front of the blade (see drawing). The blade pivot shaft should now project into the shell of the
combination bearing 1254.13 at the top.
Fill the bearing shell with grease, and place exactly 14 steel balls in the shell, where the grease
will prevent them rolling about.

During this procedure the blade pivot shaft must always project far enough into the bearing shell
to prevent the balls falling inward, between the blade holder and the blade pivot shaft.

To complete the first end of the blade pivot shaft, fit the thrust washer of the combination
bearing on top, with the ball channel facing inward, and tighten the M5 x 12 socket-head cap
screw.
Turn this assembly over, so that the blade holder you have just installed is at the bottom, and fit
the second blade holder on the blade pivot shaft using the same procedure, not forgetting the

0.2 mm shim washer.

Take great care not to allow the blade pivot shaft to project too far through the hub and blade
holder, otherwise the balls may fall out of the combination bearing you first assembled!

The second combination bearing can now be completed following the procedure outlined above.
Tighten the M5 x 12 socket-head cap screw.
Check that both blade holders rotate freely, and if necessary tap the holders and hub with the
handle of a screwdriver so that the bearings seat themselves properly; this procedure helps to
remove any stress from the bearings.
If the blade holders are stiff to move because they are being pressed against the hub, fit a
spacer washer 4450.57 between the thrust washer of one of the combination bearings and the
blade pivot shaft.

If you have to dismantle the combination bearing, take care that no balls fall out!

Once you are confident that the blade holders swivel freely, apply thread-lock fluid to the M5 x
12 socket-head cap screws and tighten them fully. If it was necessary to fit a spacer washer

4450.57, be careful when tightening the socket-head cap screws, otherwise the brass washer
could be pushed out of shape.

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26

3.3 Assembling the Hiller rotor

Assemble the rocker 4618.27 as shown in the drawing. Note that the hole in the pivot bar

4618.28 must line up with the through-hole in the rocker, to ensure that the flybar can be slid
through later without jamming or binding. Fit an M2 x 4 screw on the outside on each side to fix
the two ballraces to the hub. Check that the rocker rotates freely.

Press the ballraces 4618.6 into both sides of the rocker 4618.27. Slide the flybar 4718.67
through the rocker and set it exactly central, i.e. projecting out of the bearings by an equal
distance on both sides.

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27

Roughen the surface of the flybar at the point where the control bridge 4618.37 is to be
clamped. Screw the control bridge to the flybar, applying thread-lock fluid between the bar and
the control frame to prevent any danger of the flybar rotating in the control bridge during violent
aerobatic manoeuvres.
Slip the ball-collets 4607.36 on both ends of the flybar, and position them resting against the
control bridge. Before fitting the M3 x 3 grubscrews apply a drop of thread-lock fluid to the
threaded holes in the ball-collets. Press the double ball-links 4607.35 into place as shown.
Apply thread-lock fluid to the sockets in the flybar paddles 4682.34, and screw them onto the
ends of the flybar to a depth of exactly 15 mm. Set them exactly parallel to each other and to the
control bridge.

Press an M3 nut into the recess in one side of the rotor head hub, and press the two guide pins

4450.44 for the collective pitch compensator into the holes, applying thread-lock fluid to the
sockets first.

Make up two straight and two angled pushrods as shown in the drawing.

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28

3.4 Installing the main rotor head

Fit the main rotor head on the main rotor shaft.
Align the hole in the rotor head with the top cross-hole in the main rotor shaft, then fit the special
screw 4618.87 to fix the parts together.

The next step is to install the pushrods 4618.150 and 4618.151 which you have just prepared;
their positions are shown in the drawing. Note that the arms of the mixer levers 4618.32 are of
different length: the double ball-links attached to the flybar must be pressed onto the longer
lever arms, whereas the straight pushrods run from the shorter, inner levers to the swashplate.

The angled pushrods 4618.150 now have to be adjusted in order to obtain maximum possible
collective pitch adjustment range. This is the procedure:

Disconnect the ball-links on the swashplate outer ring (if necessary), and slide the swashplate
up as far as it will go. The swashplate should now rest against the collective pitch compensator
when the compensator itself is resting against the bottom face of the main rotor head.

If this is not the case, the angled pushrods must be adjusted as follows:

•

The swashplate rests against the collective pitch compensator, but there is a gap between
the collective pitch compensator and the rotor head:









shorten both pushrods.

•

The swashplate rests against the rotor head, but there is a gap between the swashplate and
the collective pitch compensator:









lengthen both pushrods.

It is essential to adjust the length of both pushrods by the same amount, i.e. they must always
be exactly the same length.

Now carry out the fine adjustment of the auxiliary rotor, ensuring that the Hiller paddles run
parallel to the swashplate when the swashplate is exactly horizontal. If you need to adjust the
length of the pushrods 4618.150, always adjust them in opposite directions by the same
amount; never adjust only one of them!

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4. Assembling the tail rotor gearbox

(bag UM-11, 11A)

Fit the bevel gear 4618.38 on the tail rotor shaft 1221 as shown in the drawing. Apply a drop of
thread-lock fluid to the threaded holes in the bevel gear, then fit the M3 x 3 grubscrews. One of
the two grubscrews must engage squarely on the machined flat in the tail rotor shaft. Take care
not to tighten the grubscrews so much that they force the bevel gear out of shape, as this will
prevent it running true. Fit the spacer sleeve 4450.28A and the bearings 4618.69 and 4450.22
on the tail rotor shaft, pushing them hard up against each other. Slide this assembly into the tail
rotor gearbox 4448.73 as far as it will go, and fit the M2 x 4 retaining screw. Check that there is
absolutely no axial play in the shaft; to take up any slack fit 5/10 x 0.1 mm shim washers in the
position shown.

Fit the ballraces 4618.69 and the spacer 4618.66 on the tail rotor input shaft 4448.40 as shown
in the illustration. Apply bearing retainer fluid, Order No. 951, before fitting the bearings.
The bearings must not be under stress; if necessary tap on them using a screwdriver handle or
similar, so that they automatically seat correctly on the shaft. Allow the bearing retainer fluid to
dry.
Fit a 5/10x0.1shim washer and a bevel gear 4618.38 on the tail rotor input shaft 4448.40 as
shown in the illustration without using bearing retainer fluid at this stage.
Fit and tighten the M3 x 3 grubscrews in the bevel gear. Note that one of the two grubscrews
must engage squarely on the machined flat in the tail rotor input shaft.

Now fit the prepared drive shaft assembly into the tail rotor housing, and line up the hole in the
spacer 4618.66 with the hole in the tail rotor housing, then secure it with an M2 x 5 countersunk
screw.
Fit a steel rod (screwdriver blade or similar) through the threaded holes in the coupling 4448.40.
Using the rod as a handle, pull hard on the coupling (against the countersunk screw joint), so
that the tail rotor drive assembly seats itself in the housing with maximum possible gear

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30

meshing clearance between the bevel gears, as if under maximum load. Now check that the tail
rotor gearbox runs smoothly, with just detectable meshing clearance in the bevel gears.

If the play in the gears is too slight, i.e. the gears are stiff to move, you will need to remove the
drive assembly again and remove the shim washer under the bevel gear. If, however, there is
too much play in the gear meshing insert additional shim washers. If you work carefully, making
small adjustments, it is possible to set up the bevel gears so that they work freely but

without

backlash. Reinstall the unit, repeat the pulling procedure as described above, and you should
find that the gear meshing clearance is correct.

Note

: if you still cannot set the gear meshing clearance to your satisfaction, the problem may be
that the bevel gear on the tail rotor shaft is located too far outward due to manufacturing
tolerances, and is not engaging correctly with the bevel gear on the input shaft. If this is the
case, you will find that the tips of the teeth of the bevel gear 4618.41 are already fouling the
spacer sleeve 4450.28A, and yet there is backlash in the meshing clearance. In this case you
must fit the shim washers between the bevel gear 4618.38 and the bearing 4450.22, instead of
between the spacer sleeve and the bearing 4618.69, until the desired slight meshing clearance
is present.

Now remove both assemblies again, apply bearing retainer fluid, Order No. 951, to the bearings,
the setscrews, and the bevel gear on the input shaft, re-fit them on the tail rotor shaft and the
input shaft, and assemble the parts permanently.

Fit a 3 mm Ø washer on the M3 x 22 socket-head cap screw, followed by the tail rotor bellcrank

4618.60.

Check that the bellcrank rotates freely on the screw. If necessary de-burr the bore of the bell­crank and lubricate it with silicone oil. With the bellcrank on the screw, fit the screw in the hole in
the shoulder of the tail rotor housing and tighten it by a few turns; do not secure it permanently
at this stage because the control bridge, which is described in the next section, must first be
installed.

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31

5. Assembling the control bridge

(bag UM-11B)

Press the ballrace 4607.137 into the control ring 4618.62 as far as it will go. Apply a little thread­lock fluid to the control sleeve 4618.61, taking care not to allow it to run between the control ring
and the control sleeve. Push this assembly onto the control sleeve, with the inner ring of the
ballrace resting against the flange of the control sleeve.

Fit the two ball-links 4618.55 on the control bridge 4618.61, slide it onto the control sleeve, and
press it against the inner ring of the other ballrace. Press the shakeproof washer 1291.26 on the
control sleeve and against the control bridge.
Check that the control ring can rotate easily on the control bridge, but without any axial play at
all. If the ring is stiff to turn, it is likely that the two bearings are stressed against each other, and
this can usually be corrected by tapping them with the handle of a screwdriver.
Fit the control bridge on the tail rotor shaft, then engage the actuator lever on the ball on the
control ring, and tighten the M3 x 22 screw so that the lever and control bridge move freely but
without slop; finally secure it using the M3 self-locking nut.

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6. Assembling the tail rotor head

(bag UM-11C)

Assemble the tail rotor head as shown in the drawing, greasing all bearings as you install them.

Place the two O-rings in the hub 4448.22 and press them into the channels. Oil the O-rings, fit
the tail rotor head on the tail rotor shaft, and line up the cross-hole in the shaft accurately with
the hole in the hub, and press the pin 4448.22 into place to fix the parts together. The pin is
secured in turn by fitting the M3 x 3 grubscrew.

Note the correct orientation of the hub, as shown in the drawing.

Fix the tail rotor blades in the blade holders using the two M3 x 20 screws. The tail rotor blade
fixing screws must not be over-tightened; the blades should just be free to swivel, so that they
can align themselves in the optimum position when they spin up to speed.

Note the orientation of the tail rotor blades: when viewed from the left-hand side, the tail rotor
rotates clockwise („bottom blade forward“); and the blade pitch arms on the blade holders must
be located in front of the blades.

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33

7. Tail boom

(bag SR-0)

7.1 Assembling the tail boom braces

(bag SR-1)

Press the strut end-pieces 1292.11 into both ends of the aluminium tail boom braces 4445.8 as
far as they will go, and set the eyes parallel to each other. Drill a 1.5 mm Ø pilot-hole through
each brace and into each end-piece, and fit 2.2 x 6.5 mm self-tapping screws to secure them.

Apply bearing retainer fluid to the M3 x 25 grubscrews and screw them into the two canopy
stand-off pillars 4445.12 as far as they will go. Allow the fluid to cure completely.

7.2 Preparing the mechanics for mounting the tail boom

Screw the tail boom flange 1292.5 to the bearing holder 4448.14 on the mechanics using two
M3 x 16 socket-head cap screws. Press the M3 x 12 socket-head cap screw and M3 nut into
the tail boom clamp, and tighten the screw fully to cut the threads. Loosen the screw again to
the point where the tail boom can be pushed into place later.

7.3 Preparing the tail boom

(bag SR-2)

Note that the tail boom is curved

at the front end

; the purpose of the curvature is to raise the tail
boom towards the tail. This increases tail rotor ground clearance, but - importantly - also
ensures that the tail rotor drive shaft runs in a gentle curve, and thereby runs smoothly, without
vibrating.
Push the two shaft bearings 1292.10A into the tail boom 4445.9 using a length of beech dowel
or similar. The front bearing should be located 200 mm from the front end of the boom, and the
rear bearing 300 mm from the rear end. The spherical recess in both bearings should face
forward. Now place the guide ring 4451.7 in the front end of the tail boom, with the conical
opening facing the rear, and set it at a depth of exactly 27 mm. When the tail drive system is
connected, the union sleeve is guided accurately onto the coupling yoke by means of the guide
ring.

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34

The front shaft coupling can now be prepared; you must work carefully here, as the coupling
must engage automatically inside the tail boom without you being able to see what is
happening, and without using tools. For this reason it is important that the brass coupling sleeve

4618.58 is an easy sliding fit over the coupling yoke 4618.57. If necessary, remove any rough
edges from the yoke, or reduce it in size slightly using fine abrasive paper. Slide the tail rotor
drive shaft, Order No. 4451.19, into the coupling sleeve, and push it fully forward so that the
pre-formed part engages inside the sleeve. Fit a grubscrew in the collet 56.0, slide it along the
tail rotor shaft and position it just aft of the sleeve. Push the tail rotor shaft into the coupling yoke
as far as it will go, then slide the sleeve over the yoke to the same extent. Position the collet on
the shaft with about 1 mm clearance to the sleeve, and tighten the grubscrew fully.

7.4 Completing the tail boom

Fit the tail rotor flange 1292.7 on the rear end of the tail boom, then slide a support flange

1292.6 along the boom as shown in the drawing. Note that the gap in the support flange must
be on top, and the moulded-in bored lug must be on the left-hand side.

If you intend to use a tuned pipe silencer, you will need to install an additional support for it on
the tail boom, forward of the tail boom brace flange, as shown in the drawing. The parts for this
are not included in the kit, and must be purchased separately.

7.5 Determining the correct length of the tail rotor drive shaft

Remove the tail rotor drive shaft from the mechanics, oil it lightly, and slide it through the shaft
bearings in the tail boom, rotating it all the while, until the rear end projects out of the tail boom
far enough to be inserted in the tail rotor coupling. Push the shaft in as far as it will go, then pull
it back again by 1 mm, and temporarily tighten the grubscrews in the coupling to secure it in this
position. When finally assembled, the tail rotor shaft must have about 1 mm axial play in the
front coupling yoke, and that is why you are temporarily setting up 1 mm clearance at the tail
end. Later you will push the shaft into the tail rotor coupling as far as it will go, and the clearance
will appear at the front end. Temporarily insert the tail boom in the tail boom flange 1292.5, at
the same time pushing the tail boom fully onto the bearing holder 4448.14. Secure the tail boom
by tightening the clamping screw in the flange. Slide the tail rotor into the tail boom from the
rear, and rotate the shaft to ensure that the front end engages in the quick-release coupling
which is part of the main gearbox. It should be possible to slide the tail rotor into the tail boom to
the point where it rests against the flange, without the drive shaft fouling the quick-release
coupling at the front. If this is not the case, the tail rotor shaft must be shortened slightly.

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35

Alternatively you could re-position the tail rotor gearbox flange 1292.7 slightly further aft on the
tail boom. Remove the tail boom from the mechanics again.

7.6 Connecting the tail boom to the mechanics

Withdraw the tail rotor assembly from the tail boom to the point where the shaft coupling
becomes accessible. Undo the grubscrews in the shaft coupling, so that the tail rotor shaft

4451.19 can be pulled out. Carefully de-grease the shaft, push it as far as it will go into the shaft
coupling, and secure it in this position with the grubscrews. This joint must be really firm. First
unscrew the grubscrews from the coupling entirely, apply thread-lock fluid, Order No. 952, or
bearing retainer fluid, Order No. 951, to the threaded holes, then re-fit the grubscrews and
tighten them fully. Even better, file or grind a flat in one side of the shaft where the grubscrews
engage, as this effectively prevents the shaft slipping in the joint. Fix the tail rotor to the tail rotor
gearbox flange 1292.7 securely using three 2.9 x 13 mm self-tapping screws. Lightly grease the
quick-release sleeve and the front end of the tail rotor shaft.
Attach the two tail boom braces to the left and right mechanics side frames using the stand-off
pillars 4445.12, which you prepared in Section 7.1.

The completed tail boom assembly can now be pushed into the tail boom flange 1292.5 as far
as it will go; check carefully that the quick-release coupling engages correctly. Rotate the tail
boom so that the curve of the boom runs upwards, and is exactly in the vertical plane, and
rotate the tail rotor flange so that the tail rotor shaft, when viewed from the tail, stands at right­angles to the main rotor shaft. With the tail boom correctly aligned, tighten the M3 x 12 socket­head cap screw in the tail boom flange to fix it in position. We recommend that you hold the tail
boom pointing vertically upwards while you tighten the clamping screw.
Adjust the position of the rear flange 1292.6 so that the tail boom braces 4445.8 can be
attached to it as shown in the drawing, using an M3 x 30 socket-head cap screw and an M3
self-locking nut.
Place the mechanical assembly on a perfectly flat table top, and adjust the position of the tail
boom brace flange until the bottom edge of the tail rotor flange 1292.7 is about 170 mm above
the surface of the table. In this position tighten the flange clamp securely, then drill 1.5 mm Ø
pilot-holes in the tail boom through the tail rotor flange 1292.7, the tail boom brace flange

1292.6 and the tail boom flange 1292.5. Fit the 2.2 x 6.5 mm self-tapping screws to prevent the
tail boom rotating or shifting position.

7.7 Stabiliser panels

(bag SR-3)

Fix the vertical stabiliser 1292.4 to the tail rotor flange using 2.9 x 13 mm self-tapping screws.
Attach the horizontal stabiliser to the tail boom by means of the stabiliser mount and the rod
guide, using 2.9 x 19 mm self-tapping screws. Set the horizontal stabiliser exactly at right­angles to the vertical stabiliser; the distance between the horizontal stabiliser mount and the tail
rotor flange should be 200 mm. Tighten the retaining screws.

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8. Assembling the skid landing gear

(bag SR-4)

Push the skid tubes 4447.7 through the skid bars 4447.6, and set the bars 207 mm apart
(distance between retaining screws) by adjusting the position of the bars on the tubes.

The skid landing gear can now be fixed to the mechanics using two M3 x 16 socket-head cap
screws at the rear and two M3 x 20 socket-head cap screws at the front; note that the spacer
sleeves 4451.5 must be fitted at the front. Position the skid tubes so that they project beyond
the rear skid bars by about 50 mm on both sides at the rear. Check that the skid tubes are
parallel to each other. Working from the inside, drill 1.5 mm Ø pilot-holes through the skid bars
and skids, and fit 2.2 x 6.5 mm self-tapping screws to fix the parts together. Apply a little two­pack adhesive to the end-plugs and press them into the skid tubes.

9. Installing the silencer

If you are using an expansion silencer, such as Order No. 1809.33 or 1871.72, install a
pressure nipple in the expansion chamber and attach the silencer to the motor using the screws
supplied with the unit. Don’t use a gasket at the exhaust joint; it is better to apply a thin coating
of thread-lock fluid to the contact surfaces.
If you are using a tuned pipe silencer, for example Order No. 1783A, the first step is to screw
the exhaust manifold 2259 to the motor, and pass it through the circular opening in the
mechanics sub-structure; here again, a thin coating of thread-lock fluid is better than an exhaust
gasket. Install a pressure nipple on the tuned pipe, then route the pipe through the rear
bulkhead 4450.18, working from the rear, and connect it to the exhaust manifold with Teflon
hose and spring clips; there should be a gap of about 5 mm between the manifold and the inlet
stub of the tuned pipe. At an earlier stage you should have fitted the additional tail boom flange

1292.6, and this includes the tuned pipe support. Adjust the position of the support and rotate it
so that the tail pipe of the tuned pipe silencer can be clamped in the holder by tightening the M3
x 16 socket-head cap screw. Fit a piece of silicone exhaust hose on the tail pipe before you do
this.
Regardless of the type of silencer you are using, the pressure nipple on the silencer should be
connected to the vent nipple which is mounted in the top of the fuel tank, using a length of
silicone fuel tubing.

10. Tail rotor control system

(bag SR-5)

The first step in connecting the tail rotor pushrod 4451.3 is to undo the screw in the tail rotor
bellcrank 4618.60, and fit the straight end of the pushrod through the guide holes in the tail rotor
gearbox flange and the horizontal stabiliser mount, working from the tail end. If the pushrod is a
slightly tight fit in the tail rotor gearbox flange, open up the hole in the flange using a 2 - 2.5 mm
Ø twist drill. Connect the pre-formed end of the pushrod to the outermost hole in the bellcrank,
then fit the crank again and tighten the retaining screw.
Slide two rubber grommets onto the CFRP guide tube at the rear end to a distance of about 20
mm, and space them about 3 mm apart. Slip the guide tube onto the pushrod from the front, and
position it so that it rests on the tail boom brace flange 1292.6 at the rear. Fix it in this position
by wrapping a cable tie round the tail boom between the rubber grommets.

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The front end of the guide tube must

not

be supported against the tail boom, but should be left
„floating“ freely on the wire pushrod; for this reason it must be left as long as possible, i.e. it
should extend forward as close to the servo as possible.
At the front end the standard method of connecting the wire pushrod to the tail rotor servo is to
solder a threaded coupler to the end, and screw a clevis on the coupler. Remember to cut the
pushrod to the correct length before soldering the threaded coupler to the wire: when the
collective pitch stick is at centre, the output arm of the tail rotor servo should point straight down,
and the tail rotor bellcrank should be exactly at right-angles to the tail boom.

Alternatively you can simply form a Z-bend in the front end of the wire pushrod using Z-bend
pliers (Order No. 5732). The advantage of this method is that the guide tube can be extended
very close to the servo, providing maximum support for the pushrod, whereas it would have to
be shortened further if a clevis and threaded coupler were used. The drawback is that you
would have to determine the position of the Z-bend with great accuracy, because there is no
means of adjusting the pushrod length with this arrangement. This solution is therefore only
recommended to the experienced modeller.

11. Cabin

(bag SR-6)

11.1 Installing the front cabin supports

Install the two front canopy stand-off pillars in the clips at the front of the sub-structure, securing
each with an M3 x 12 socket-head cap screw fitted from the rear.

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11.2 Attaching the cabin

Press two rubber grommets 3515.3 into the appropriate holes in the bulkhead 4445.17; you may
like to apply a drop of cyano on one side to secure them. Fit the bulkhead, with the curved edge
facing down, onto the stand-off pillars which are located on the front of the mechanics. The
pillars should engage fully in the rubber grommets.
Fit two further rubber grommets in the 7 mm Ø holes in the top rear section of the cabin
moulding. Slide the cabin onto the mechanics from the front, and engage the two stand-off
pillars at top rear in the rubber grommets in the cabin moulding.
Swing the cabin up from the front until the bulkhead fitted to the front of the mechanics makes
contact with the bottom of the cabin. You will need to cut away the cabin shell on the left-hand
side to clear the exhaust manifold; there should be a gap at least 5 mm wide between cabin and
exhaust system. The bulkhead can now be glued to the cabin in this position using Stabilit
express. Allow the glue to cure fully before removing the cabin from the mechanics. It should
come off easily by first pulling it off the rear stand-off pillars at the sides, and then pulling it
forward. It should be equally easy to fit the cabin back on the model.

Tape the clear canopy screen 4445.1 to the cabin, then attach it using four 2.2 x 6.5 mm self­tapping screws. Alternatively you can glue it in place using cyano or Stabilit express. Work
carefully if you use glue to avoid smearing the clear panel.

Run the receiver aerial along the mechanics to a point aft of the front skid bar, to ensure that the
cabin can be removed easily without snagging the wire aerial. Fit the plastic aerial guide tube
through the two holes on the inside of the skid bars, and fit short lengths of fuel tubing to
prevent it slipping out. Run the aerial wire down the skid bar and into the front end of the guide
tube, and allow it to dangle freely from the rear end of the tube.

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12. Main rotor blades

Epoxy the rotor blade bushes 4607.164 in the root holes in the rotor blades, unless your blades
are supplied with these parts factory-fitted.
Allow the epoxy to set hard, then sand the blades smooth overall using fine abrasive paper,
Order No. 700.1 or 700.2.
Ideally both the weight and the Centre of Gravity of both blades should be identical. You can
check this by balancing each blade over a triangular strip of wood, as shown in the drawing.
Mark the lines of balance as shown; the blade’s CG is located where the lines cross.
However, in practice it is unlikely that you will be able to achieve perfect balance and weight
distribution without a considerable amount of work, and in any case it is not that important with
modern model helicopters. The crucial factor is that the moments of both rotor blades should be
the same when they are mounted on the rotor head. This means that blades of different weights
can certainly be used, provided that the CG of the blades is also different, and compensates for
the weight discrepancy. The method of balancing the blades is described in the next section.
Apply SPANNFIX IMMUN (colour dope), Order No. 1408, over the joints, in the region of the
root doublers (approx. 70 mm from the root) and at the tip (approx. 20 mm from the tip). The film
covering should be applied in the sequence shown in the drawing: first the top surface, then the
trailing edge, then the underside. Take care with the covering; there should be no wrinkles or
bubbles!

12.1 Balancing the rotor blades

Screw the two rotor blades together as shown in the drawing, and hang this assembly from a
length of thread. Apply adhesive tape to the tip of the lighter blade until the blades hang level.
Properly balanced blades reduce vibration to a minimum, so take your time over balancing.

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13. The set-up procedure

13.1 Setting up the cyclic control system

The basic settings for the roll-axis and pitch-axis control systems should already be correct if
you have installed the linkages exactly as described in the instructions. Since the instructions
include the lever lengths (correct linkage holes), the final setting up is carried out using the
electronic facilities on your transmitter. Note that the servo travel should not be set too high, and
ensure that the swashplate does not strike its end-stops on the main rotor shaft at either end­point of the transmitter stick travel for roll-axis and pitch-axis movements, as this would mean
that collective pitch control would not be linear, i.e. axial movements would be restricted.

13.2 Main rotor pitch settings

The main rotor pitch is measured using a pitch gauge (optional accessory, not included in the
kit). The following table shows the recommended basic settings, but the optimum values may
well vary from model to model according to the rotor blades you are using.

Minimum Hover Maximum
Hovering and practice -2° 5,5°...6° 12°
Aerobatics -4° 5°... 5,5° 8°... 9°
Autorotation -4° 5,5° 13°

The best way of setting the correct blade pitch on the transmitter is as follows:

1. Measure the hovering pitch and set it to the correct value.

2. Measure collective pitch maximum and minimum and adjust the values according to the

following diagrams using your transmitter's collective pitch curve facility.

13.3 Setting up the carburettor control system

The following diagrams show two alternative carburettor control curves:

•

The hover-optimised throttle curve produces gentle control response in the hover region.

•

The values stated above can only be a guideline as they vary greatly according to the motor,
fuel, silencer etc. in use. There is no alternative but to fine-tune them during the test-flying
programme.

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If you have made up all the linkages exactly as described in the previous sections, no changes
to the mechanical arrangements will be necessary. The following adjustments can all be carried
out at the transmitter:

1. Servo direction

Set the „sense" (direction of rotation) of all servos as stated in the instructions. Check the
throttle servo in particular!

2. Dual-Rates

You can set switchable travels for roll-axis, pitch-axis and tail rotor. As a starting point we
recommend 100% and 75% as the two settings.

3. Exponential

For the basic set-up you should leave all control systems set to „linear".

4. Servo centre offset

Do not make any adjustments to this point. At a later stage you may wish to make minor
corrections here.

5. Servo travel

This is where you can adjust the maximum servo travel. Note that the travels should always
be the same on both sides of neutral, otherwise you will end up with unwanted differential
effects:

For the throttle and swashplate servos (collective pitch function) it is important to check that
servo travels are symmetrical, i.e. identical values for both directions, and that the throttle
servo can rotate the carburettor barrel from the completely closed position (motor stopped)
to full throttle, without being mechanically stalled at any point. The collective pitch function of
the swashplate servos should produce a range of blade pitch angles covering -5° to +13°,
also with symmetrical travels; you may find it necessary to remove the servo output arm,
move it round by one spline and fit the retaining screw again.

The mechanics should now be set up virtually perfectly. When the throttle/collective stick is
at centre (hover point), collective pitch should be about 5.5°, and the carburettor barrel
should be half-open.

Note:

The collective pitch and throttle curves can be adjusted later to meet your exact personal
requirements. However, if you have already set differential travels in the basic set-up
procedure, as shown in diagram „B" above, any fine adjustments required subsequently will
be more difficult!

6. Collective pitch and throttle curves

These adjustments are of fundamental importance to the flight performance of any model
helicopter. The aim of the procedure is to maintain a constant rotor speed when the model is
climbing and descending, i.e. regardless of load. This then represents a stable basis for
further fine-tuning, e.g. of the torque compensation system etc. (see also the earlier section
on collective pitch and throttle curves).

7. Static torque compensation

The tail rotor servo is coupled to the collective pitch function via a mixer in the transmitter in
order to compensate for torque changes when you operate the collective pitch control. On
most transmitters the mixer input can be set separately for climb and descent.
Recommended values for the basic settings are: climb: 35%, descent: 15%.

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8. Gyro adjustment

Gyro systems damp out unwanted rotational movements around the vertical (yaw) axis of the
model helicopter. They do this by detecting the unwanted motion and injecting a
compensatory signal into the tail rotor control system, and in order to achieve this effect the
gyro electronics are connected between the tail rotor servo and the receiver. Many gyro
systems also allow you to set two different values for gyro gain, and switch between them
from the transmitter via a supplementary channel. The extra channel is controlled by means
of a proportional slider or rotary knob, or a switch, depending on the gyro system.

If your gyro features an adjustor box with two rotary pots for two fixed settings, and you can
switch between them from the transmitter, it is best to set one adjustor approximately to
centre (50%), and the other to 25%. If the gyro system provides proportional control between
the two set values, then the one pot should be set to „0", the other to about 80%.

If you have a gyro system whose effect cannot be adjusted from the transmitter, i.e. there is
only a single adjustor on the gyro electronics itself, the pot should be set to 50% gain as a
starting point.

Check that the direction of the gyro’s compensatory action is correct, i.e. that it responds to a
movement of the tail boom with a tail rotor response in the opposite direction. If this is not the
case, any yaw movement of the model would be amplified by the gyro! Most gyro systems
are fitted with a change-over switch which reverses their direction, and this must then be
moved to the appropriate position. However, some systems have no such switch, and in this
case the solution is to mount the gyro inverted.

One factor which all gyro systems have in common is that flight testing is necessary in order
to establish the optimum values, as so many different factors influence the settings.
The aim of the gyro adjustment process is to achieve as high a level of gyro stabilisation as
possible, without the gyro causing the tail boom to oscillate.

Notes regarding the use of the Graupner/JR „PIEZO 900 ... 5000" piezo gyro system in
conjunction with a computer radio control system (e.g. mc-12 ... mc-24)

The design of these gyro systems necessitates a different set-up process to the one described
above. Please keep strictly to the following procedure:

1.

Set the servo travel for the tail rotor channel to +/-100% at the transmitter.

2.

If you have a gyro mixer („Gyro-Control") which suppresses the gyro when you operate the
tail rotor control, it is essential to disable it permanently.

3.

Disconnect the tail rotor pushrod at the tail rotor servo.

4.

Operate the tail rotor control at the transmitter; at about 2/3 of full travel in either direction the
servo should stop, even when the stick is moved further (travel limiter).

5.

Connect the tail rotor pushrod to the servo in such a way that the mechanical end-stop of the
tail rotor coincides with the onset of the limiter on both sides (servo should not quite be
stalled by the mechanical end-stop).

It is essential to make these adjustments mechanically, i.e. by altering the linkage
points and pushrod length. Don’t try to do it electronically using the transmitter’s
adjustment facilities!

6.

Now correct the tail rotor setting for hovering, i.e. when the collective pitch stick is at centre,
using the servo centre adjustment facility at the transmitter.

7.

Gyro gain can now be adjusted between „0" and maximum via the auxiliary channel only,
using a proportional control on the transmitter. If required, you can reduce maximum gain by
adjusting the travel of the auxiliary channel or by adjusting the transmitter control (mc-22 and
mc-24 transmitter). This gives you a useful range of fine adjustment for gyro response.

8.

If you find that the tail rotor control system is too responsive for your taste, adjust it using the
exponential control facility; on no account reduce servo travel, as it must be left at +/- 100%!

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14. Final pre-flight checks

When you have completed the model, run through the final checks listed below before the first
flight:

•

Study the manual again and ensure that all the stages of assembly have been completed
correctly.

•

Check that all the screws in the ball-links and brackets are tightened fully after you have
adjusted gear meshing clearance.

•

Can all the servos move freely, without mechanical obstruction at any point? Do they all
rotate in the correct direction relative to the stick movements? Are the servo output arm
retaining screws fitted and properly tightened?

•

Check the direction of effect of the gyro system.

•

Ensure that the transmitter and receiver batteries are fully charged. We recommend using a
voltage monitor module (e.g. Order No. 3138) to check the state of charge of the receiver
battery on the flying field.

Don’t attempt to start the motor and fly the helicopter until you have successfully checked
everything as described above.
Bear in mind that the running qualities of your motor will vary greatly according to the fuel in
use, the glowplug, the height of your flying site above sea level and atmospheric conditions.
Please read the notes on motor set-up which you will find later in this manual.

Maintenance

Helicopters, whether large or small, place considerable demands on maintenance. Whenever
you notice vibration in your model, take immediate steps to reduce or eliminate it. Rotating
parts, important screwed joints, control linkages and linkage junctions should be checked before
every flight. If repairs become necessary, be sure to use original replacement parts exclusively.
Never attempt to repair damaged rotor blades; replace them with new ones.

Fitting the starter adaptor

The starter adaptor supplied with the mechanics consists of three parts which are assembled as
shown in the drawing: first push the pin 4450.5C through the extension 4450.5B, then fit the
plastic adaptor 4450.5A and check that the cross-pin engages in the channel in the moulding.
To mount the starter adaptor on the electric starter, first remove the rubber insert holder from
the starter output shaft. Slide the starter adaptor onto the starter shaft until the cross-pin in the
shaft engages with the channel in the adaptor. Tighten the two grubscrews to fix the adaptor in
place.

Ensure that the adaptor runs „true“, i.e. does not wobble when it is spinning.

To start the motor, rotate the rotor head until you can engage the starter adaptor vertically in the
motor’s cooling fan. Please note:

•

• •

•

Do not switch the starter on until you are sure that the teeth of the cooling fan are
correctly engaged with the matching teeth on the starter adaptor.

•

• •

•

When the motor has started, switch off the starter before withdrawing it.

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15. Adjustments during the first flight

15.1 Blade tracking

“Blade tracking" refers to the height of the two rotor blades when they are spinning. The
adjustment procedure aims at fine-tuning the pitch of the main rotor blades to exactly the same
value, so that the blades rotate at the same level.

Incorrectly set blade tracking, with the blades revolving at different heights, will cause
the helicopter to vibrate badly in flight.

When you are adjusting blade tracking you are exactly in the „firing line" of the blades,
so keep at least 5 metres away from the model in the interests of safety.

You can only check blade tracking if you are able to see clearly which blade is higher and which
is lower. The best method is to mark the blades with coloured tape as follows:

There are two alternative methods: figure „A" shows the use of different colours on the blade
tips; fig. „B" shows the use of the same colour, but applied at different distances from the blade
tip.

Procedure for adjusting blade tracking:

1. Set the helicopter to the point where it is almost lifting off, then sight directly along the rotor

plane.

2. If you can see that the rotor blades are running in the same plane, no adjustment is required;

however, if one blade is running higher than the other, the settings must be corrected.

3. Locate the pushrods between the swashplate and the mixer levers; the adjustment is made

at the ball-links on both ends of these pushrods: unscrew the links to raise the blade, screw
them in to lower it.

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15.2 Adjusting the motor

Please be sure to read the operating instructions supplied with your motor.

The correct matching of collective pitch and throttle when the helicopter is hovering is of crucial
importance to the model’s flying characteristics and performance. For example, if the pitch of
the main rotor blades is too high, the motor may not reach the intended rotational speed, and
this may cause you to think that the motor is not powerful enough for the job. The fact that the
motor will overheat and thereby lose more power tends to reinforce that idea. For this reason
first set the collective pitch value for the hover exactly as described earlier in these instructions,
then match the motor settings to that.
Although most motors nowadays are supplied with the carburettor adjusted to approximately the
right settings, final adjustment of the needle valves can only be made under practical test
conditions. Most motors now feature twin-needle carburettors, and in this case the starting point
for adjusting the idle / mid-range needle is to screw it in to the point where it just dips into the
needle valve on the opposite side when the carburettor is half-open.

Typical twin-needle carburettor

For your first attempt at starting the motor, open the needle valve 1½ to 2 full turns from closed,
connect the glowplug to the plug battery and start the motor by engaging the adaptor on the
electric starter in the teeth of the fan and switching the starter on.

Caution: when the motor starts, withdraw the electric starter from the fan socket
immediately, otherwise you could damage the model.

When the motor is running, slowly increase throttle/collective pitch. If the fuel mixture is too
„rich" and the model fails to lift off, close (screw in) the needle valve in small stages. In order to
set the motor correctly for hovering you will need to adjust the idle needle, which also governs
the mid-range settings. Note that any adjustment you make here is also influenced by the
primary needle valve setting. Carefully close (screw in) the idle needle until the motor runs
smoothly at hover, without any tendency to stop through too rich a mixture. If motor speed is
then too low, increase the hover throttle setting at the transmitter. Never attempt to increase the
motor speed for hovering by setting the idle needle too lean. The final needle valve setting can
only be established with the model flying under power with „full collective", and for this reason
you are bound to start by „feeling your way" slowly to the correct setting.

If in any doubt, always set the mixture on the „rich" side. Initial hovering flights should
always be carried out with the motor set distinctly rich.

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16. General safety measures

•

Make sure you have adequate third-party insurance cover.

•

Wherever possible join the local model flying club.

At the flying site:

•

Never fly your model above spectators.

•

Do not fly models close to buildings or vehicles.

•

Avoid flying over agricultural workers in neighbouring fields.

•

Do not fly your model in the vicinity of railway lines, major roads or overhead cables.

Pre-flight checks, flying safety:

•

Before you switch on the transmitter check carefully that no other model flyer is using the
same frequency as you.

•

Carry out a range check with your RC system.

•

Check that the transmitter and receiver batteries are fully charged.

•

Whenever the motor is running, take particular care that no item of clothing can get caught
on the throttle stick.

•

Do not let the model fly out of safe visual range.

•

There should always be a safe reserve of fuel in the tank. Never keep flying until the fuel
runs out.

Post-flight checks

•

Clean oil residues and dirt from the model and check that all screws etc. are still tight.

•

Look for wear and damage to the helicopter, and replace worn parts in good time.

•

Ensure that the electronic components such as battery, receiver, gyro etc. are still securely
fixed. Remember that rubber bands deteriorate with age and may fail.

•

Check the receiver aerial. Conductor fractures inside the flex are often not visible from the
outside.

•

If the main rotor should touch the ground when spinning, replace the blades. Internal blade
damage may not be visible from the outside.

•

Never carry the model by the tail boom: too firm a grip can easily deform the tail rotor
pushrod.

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17. Some basic terms used in model helicopter flying

The term „rotary wing machine" indicates that the helicopter’s lift is derived from rotating „wings"
which take the form of rotor blades. As a result, a helicopter does not require a minimum
forward speed in order to fly, i.e. it can hover.

Cyclic pitch

Cyclic pitch variation is used to steer the machine around the roll and pitch axes. Changing
cyclic pitch has the effect of altering blade pitch depending on its position in the circle. The
effect is caused by tilting the swashplate, which then effectively tilts the helicopter in the
required direction.

Collective pitch

Collective pitch provides control over vertical movement, i.e. for climb and descent. The pitch of
both rotor blades is altered simultaneously.

Torque compensation

The spinning rotor produces a moment which tends to turn the whole helicopter in the opposite
direction. This effect must be accurately neutralised, and this is the task of the tail rotor. Tail
rotor blade pitch is altered to vary torque compensation. The tail rotor is also used to control the
model around the vertical (yaw) axis.

Hovering

This is the state in which the helicopter flies in a fixed position in the air, without moving in any
direction.

Ground effect

This occurs only when the machine is close to the ground, and it falls off as altitude rises. At an
altitude of about 1 - 1.5 times the rotor diameter, ground effect is completely absent. Normally
the revolving airflow from the main rotor is able to flow away freely, but in ground effect the air
strikes an obstacle (the ground) and forms an „air cushion". In ground effect a helicopter can lift
a greater weight, but its positional stability is reduced, with the result that it tends to „break
away" in an unpredictable direction.

Climb

Any excess power above that required for hovering can be exploited to make the helicopter
climb. Note that a vertical climb requires more energy than an angled climb which includes
forward motion. For this reason a model with a given amount of motor power will climb more
rapidly at an angle than vertically.

Level flight

A helicopter absorbs least power when flying straight and level at about half-power. If you have
trimmed the machine carefully for a steady hover, it will tend to turn to one side when flown
forward. The reason for this phenomenon is that the rotor blade which is moving forward
encounters an increased airflow caused by the wind, and this increases its upthrust compared
with the blade which is moving downwind, where the same airflow has to be subtracted. The net
result is a lateral inclination of the helicopter.

Descent

If the helicopter’s rotor speed is relatively low and you place the helicopter in a fast vertical
descent, the result can be that insufficient air flows through the rotor. This can cause what is
known as a „turbulent ring", when the airflow over the blade airfoil breaks away. The helicopter
is then uncontrollable and will usually crash. A high-speed descent is therefore only possible if
the helicopter is moving forward, or if the rotor is spinning at high speed. For the same reason
care should be exercised when turning the model helicopter downwind after flying into wind.

Flapping motion of the rotor blades

As we have already seen, the forward-moving blade produces greater upthrust than the trailing
blade. This effect can be minimised by allowing the leading blade to rise and the trailing blade to
fall. The rotor head is fitted with what is known as a flapping hinge to allow this movement, and
this prevents the rotor plane tilting excessively in forward flight. In model helicopters a single
hinge shared by both blades has proved an effective solution to the problem.

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Auto-rotation

This term refers to the flight of a helicopter without motor power. The rotational speed of the
main rotor can be kept high by setting both blades to negative pitch, and the airflow through the
rotor as it descends then keeps the blades turning. The rotational energy stored in the rotor by
this means can be converted into upthrust when the helicopter is close to the ground, by the
pilot applying positive collective pitch. Of course, this can only be done once, and it has to be
done at the correct moment. Auto-rotation allows a model helicopter to land safely when the
motor fails, just like a full-size machine.

However, auto-rotation places considerable demands on the pilot’s judgement and reflexes; you
can only halt the machine’s descent once, and you must not „flare" too early or too late. Much
practice is required to get it right.