Section 7. Transmission Systems. 1 of 30

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2 POWER TRANSMISSION SYSTEMS The Power transmission systems include the following components. Main Gearbox (MGB) and Main Rotor 2. Intermediate Gearbox (IGB) 3. Tail Gearbox (TGB) and Tail Rotor Coupling between the three gearboxes is achieved by tubular shafts with flexible connections. Main Gearbox The Main Gearbox transmits the power from the two engines to the rotors whilst reducing the rotational speed. It also drives two pumps for its own lubrication system along with the accessories. These accessories consist of. Two alternators 2. Two hydraulic pumps 3. A fan to cool the lubricating oil. It is of modular construction for ease of maintenance and reduction of servicing time. Figure shows an external view of the gearbox and identifies some of the main components. Oil Filter Housing MGB Oil Cooler Fan Drive RH Engine Input LH Hydraulic Pump RH Servo Mount LH Accessory Housing RH Torque Transmitter Oil Filler Cap LH Alternator Drive Rear Reduction Gear Cover Tail Rotor Drive Flange Rotor Brake Disc RH Alternator Drive RH Hydraulic Pump RH Accessory Housing Figure Main Gearbox External Components 2 of 30

3 MGB CH MGB T MGB COOL MGB P A WARN Central Warning N R M A X N R M I N Aural Warning Switch DEG ROTOR % Pitch Gauge Torque Gauge NR 340 RPM tr/mn NR+NF RPM tr/mn 00 Left-Hand Nr Gauge Right-Hand Nr and Nf Gauge Figure 2 Transmission Monitoring Systems 3 of 30

4 Intermediate Gearbox Temperature Tail Rotor Gearbox Temperature ºC x 0 ºC x Main Gearbox Temperature 0 5 ºC x bar 8 Main Gearbox Normal Pressure S/BY Stand-By Left-Hand Hydraulic Gauge 0 2 bar Main Gearbox Standby Pressure AUX Figure 3 Monitoring Panel Limitations Engine to MGB Coupling Torque % Time Twin Engine Maximum 00% 5 min Maximum Continuous 8% Unlimited Maximum 69% 2½ min Single Engine Maximum Continuous 66% Unlimited Transient Over Torque 74% 20 sec The engine free turbines transmit their power to the gearbox via Bendix shafts. These shafts are specially constructed with electro-beam welded flanges which can flex to take up any misalignments between engine and gearbox. In the event of a flange rupture a safety bearing incorporated at the engine end and a splined shaft at the gearbox end, prevent the drive shaft from flailing around. The shafts are enclosed by coupling tubes attached to the MGB and forming the rear engine support. These tubes have a gimbal joint at their centre to give 2 freedom of alignment between engine and gearbox. 4 of 30

5 MGB Gear Train The internal gear train is shown schematically in Figure 4. The input shafts are connected by splines to the front reduction gear, which then drives the intermediate shafts. Mounted on these shafts are the torque sensing wheels which are described later. At the output end of the intermediate shafts are the free-wheels which drive the bevel pinion and hence the bevel pair. Internal splines in the bevel pinion drive the tail rotor drive shaft on which is mounted the Rotor Brake. The bevel pair transmits the drive to the rotor via a vertical shaft and two epicyclic gear trains. At the base of the vertical shaft, gear wheels drive the two lubrication pumps. Note - There are five stages of reduction through the gearbox:. At input to intermediate shaft 22,840-7,960 RPM. 2. After free-wheel to bevel pinion 7,960 4,888 RPM. 3. At main bevel pair 4,888 2,390 RPM. 4. At st stage epicyclic 2, RPM. 5. At 2 nd stage epicyclic RPM. Main Rotor 265 RPM 772 RPM RH Accessories Drive 4,888 RPM Tail Rotor 2,390 RPM LH Accessories Drive Engine 2 Engine 22,840 RPM 7,960 RPM LH Free-Wheel (RH free-wheel on opposite side) Lubrication Pumps Figure 4 Internal Gearbox Drive-Train 5 of 30

6 22840 rpm No. Engine No. 2 Engine rpm 7960 rpm Drive to 7960 rpm Main Rotor Free Wheel Free Wheel 4573 rpm 608 rpm 608 rpm 4573 rpm Left-Hand Hydraulic Pump No. Alternator No. 2 Alternator Right-Hand Hydraulic Pump 848 rpm 4888 rpm Oil Cooler Tail Rotor Drive Figure 5 Gearbox Accessory Drive-Train 6 of 30

7 MAIN GEARBOX LUBRICATION SYSTEM General The gears and bearings are lubricated and cooled by oil under pressure. An external oil cooler is provided to reduce the temperature of the oil during operation and because this arrangement is vulnerable regarding leaks, two pumps are provided. One, the Main Pump, circulates the oil through the cooler whilst the other, the Standby Pump, outputs directly to the filter and by-passes the cooler. Both pumps are internal gear type with the Main Pump drawing oil at the 8 litre level and the Standby Pump at the bottom of the gearbox. The oil used is of synthetic type (Aeroshell 500) and the level can be checked by a sight glass on each side of the Gearbox. The filler cap is on the right-hand side. Cockpit Indications enable monitoring of the system during operation. Lubrication Minimum Pressure bar Normal Pressure Range (Main Pump) 4-7 bar Normal Pressure Range (Standby Pump) 2 4½ bar Main Gearbox Maximum Temperature 45 C Maximum Sight level 9.6 litres Minimum Sight Level 7 litres Total Capacity including cooler 2.4 litres IGB and TGB Maximum Temperature 20 C Cockpit Indications 32 Alpha Panel - MGB CH MGB T MGB COOL MGB P Multi Instrument Panel - Oil Temperature Gauge, Main Pressure Gauge, Stand-by Pressure Gauge The sensors and transmitters for these indications are shown in the lubrication diagram. 7 of 30

8 Operation Normal Refer to Figure 6. The Main Pump discharges through the oil cooler to the filter and hence via the distribution drillings and jets to the gears and bearings. The oil then returns to the sump by gravity. A tapping at the outlet of the Main Pump transmits the output pressure to the distributor valve (3) which moves over against a spring and restricts the suction of the Standby Pump. The Standby Pump is kept lubricated by the reduced flow and maintains a reduced pressure to the system. Notice that both pumps are continuously driven. The pressure relief Valve (2) at the output of the Main Pump ensures quick warm-up on starting by reducing the flow through to the cooler. The cold oil means a higher pressure and the relief valve opens. Emergency Should the Main Pump pressure drop (due to a leakage of oil or failure of pump) the distributor valve (3) will no longer be held against the spring and will move over to allow a full flow to the Standby Pump. The output from this pump flows directly to the filter and by-passes the oil cooler, giving rise to a higher operating temperature. As the pressure from the Main Pump has fallen below 3 bars the pressure switch (7) will operate and illuminates the MGB COOL light on 32 alpha panel indicating to the pilot that cooling is no longer available. With reduced power the Gearbox can operate for 2 hours under these conditions. However, a closer watch should be kept on the MGB temperatures and pressure warning lights and gauges. In the event of the oil temperature reaching 45 C. The MGB T light will be illuminated. This is sensed by temperature probe (5). Should the pressure in the oil distribution pipes fall below bar the pressure switch (9) will operate and illuminate the red MGB P warning light on the 32α panel. The gearbox is no longer lubricated and the aircraft must be landed immediately. The presence of metal particles in the oil is detected by the magnetic chip detector (4) and indicated by illumination of the amber MGB CH warning light on the 32α panel. If the oil filter starts to clog the pressure differential across the filter will increase and open the by-pass valve. Indication will be high operating oil pressure above 7 bars. Notice that if operating on the Standby Pump the pressure will not rise high enough to operate the by-pass valve due to the pressure relief valve () being set at 3.6 bar. Instances have occurred of the pressure transmitting pipe between Main and Standby Pumps, fracturing, resulting in full flow through the Standby Pump and high Standby pressure readings (>6 bar) on the gauge. 8 of 30

9 Emergency System Pressure Main System Pressure Pressure < bar BAR BAR Pressure < 3 bar MGB COOL MGB P 9 Filter By-Pass Δ P = 7-8 bar 8 7 Filter Emerg Pump Main Pump Front Reduction Gears Litre Level Accessory Drive Housing Oil Cooler 4 5 MGB CH MGB T ºC MGB Chip Warning Light Temperature > 45ºC Figure 6 Main Gearbox Lubrication Key to Figure 6. Pressure Relief Valve 3.6 bar 2. Pressure Relief Valve 0 bar 3. Distribution Valve controlled by main pump pressure 4. Magnetic Chip Detector 5. Temperature Probe for MGB T warning light 6. Temperature Probe for cockpit Gauge 7. Pressure Switch at <3 bar for MGB COOL warning light 8. Pressure Switch for normal system cockpit gauge 9. Pressure Switch for MGB P warning light 0. Oil supply to rotor shaft bearings. Pressure Switch for emergency system cockpit gauge 9 of 30

10 MGB Attachment & Suspension To absorb the vibrations and torsional loads transmitted by the rotor the main gearbox is attached to the airframe by a flexible system. Three steel tubes, attached to the conical housing at the bottom of the Rotor Mast and to the transmission deck, support the weight of the MGB and the Rotor Head whilst stationary and transmit the rotor lift to the airframe in flight. At its base the MGB is attached to a titanium flexible mounting plate, known as the barbecue plate, which is attached to the transmission deck. This flexible plate acts like a spring to counteract the torque and dampens any vibrations. 3 Steel Suspension Bars Forward Blades which can be distorted Titanium Flexible Mounting Plate Barbecue Plate Attachment flanges on structure MGB attachment ring Figure 7 Gearbox Mounting 2Hz Vibrations When initiating ground taxying there is a possibility of setting up a 2Hz vibration phenomenon caused by a resonant vibration within the gearbox. This vibration can be transmitted to the forward servo control which will aggravate the situation. If this is encountered the cyclic stick should be re-centred and pitch reduced to minimum. A modification kit is available to overcome this problem and will be fitted should this phenomenon occur. As this is purely a ground-handling problem it in no way affects the serviceability once airborne. 0 of 30

11 TORQUE MONITORING Sensing The torque developed is sensed at the middle of the Intermediate shafts of the gearbox by means of an electromagnetic sensor and two wheels attached one to each end of the shaft. One wheel has 4 notches and the other 4 teeth, which locate in the notches of the first wheel. When the shaft has no torque applied to it the teeth are central in the notches and 4 pairs of equal width gaps are formed around the shafts. When the shaft rotates these gaps pass across the face of the sensor and induce electrical pulses, which have a shape, reflective of the gap width. As torsion is induced in the shaft the tooth will move in the notch and the gaps will vary, one becoming larger and the other smaller. The signals from the sensor are passed to a calculator which processes this information and produces a DC voltage proportional to the applied torque which is then transmitted to the gauge. Another wheel with 4 fixed pairs of gaps is mounted on the shaft to enable the sensing system to be set up on installation. Compensation for temperature and shaft elasticity characteristics are built into the calculator logics. The system is inoperative below 3,500 RPM, as incorrect readings will be obtained below this figure. Engine 2 MGB Tq MGB Power Shafts Pilots Gauge Engine Towards Rotor Torque Calculator TQ Tq Torque Calculator 2 TQ Co-Pilots Gauge Sensor Pulses representative of the torsion and hence of the torque TQ Torque Calculator Low Torque High Torque Engine End Rotor End Power Shaft 4-Gap Wheel 4-Tooth Wheel Figure 8 Torque Measurement of 30

12 Gauges The power developed by each engine is represented in the cockpit by two torque gauges (one for each pilot). The gauges have two needles and can be set in two modes of operation. + 2 Mode In this configuration the number needle indicates total torque and the number 2 needle the torque imposed by Engine 2. Cross-Hatched Mode - In this configuration each needle reads its individual engine torque. A rotary selector at the bottom left corner of the gauge is used to select either mode and indication of the selected mode is shown in a window alongside the selector (+2 or cross-hatched flag). The normal operating position is +2. The gauges are calibrated in % with an outer green arc for total torque and inner green arc for single engine torque. A power supply failure indicator is located at the bottom centre of the gauge. Pushing the rotary selector in tests the operation of the gauge and both needles return to zero With the rotary test/selector button rotated anti-clockwise + 2 will be indicated on the corner of the gauge. Number needle will indicate total torque and needle 2 will indicate the torque of the number 2 engine % With the rotary test/selector button rotated clockwise a cross-hatched indicator will appear in the corner of the gauge. Torque Both needles will now indicate respective engine torque and be more or less one above the other. Figure 9 Torque Gauge 2 of 30

13 Rotor Brake Refer to Figure 0. The Rotor Brake is a hydraulically operated disc type brake mounted on splines on the output to the tail rotor drive shaft. It is situated just below the oil filter at the rear of the Main Gearbox. The disc is constructed of carbon composite and there are 3 pistons operating on friction linings. The Hydraulic pressure is supplied by the Left Hand hydraulic system at 75 bar and is reduced by the Pressure Reducing Valve to 2 bar for dynamic braking or 05 bar for static braking (strong wind operation). Control of the brake is by means of 3 levers, Rotor Brake Safety and Rotor Brake situated side by side on the right-hand side of the overhead quadrant and a 05 bar Authorisation Lever mounted on the bulkhead behind the Captain and just above his right shoulder. This lever is encased in a clear plastic box fitted with a hinged lid. The function of the Rotor Brake Safety is to prevent untimely braking of the rotor in flight. As the system operates with continuous pressure from the left-hand hydraulic system the safety valve is there to cover any failure of the brake Pressure Reducing Valve. Operation of the brake is indicated on the 32 alpha panel by 2 amber lights RB SAFE ROT BR The Rotor Brake can only be applied when the safety handle is in the un-safe position (aft). This actuates a micro-switch to illuminate the RB SAFE light. When the Rotor Brake handle is now applied hydraulic pressure can pass through the safety valve to the pistons on the brake. A pressure switch, set at 2½ bar, illuminates the ROT BR light when the pressure acting on the brake is above this figure. In order to prevent inadvertent operation of the brake during starting procedures, a micro-switch has been introduced at the 05 bar gate and the 2.5 bar pressure switch has been coupled to the engine starting system. Both the pressure switch and the micro switch will inhibit engine starting unless -. The Rotor Brake lever is at 'OFF' position and therefore there is no pressure in the system. 2. The Rotor Brake lever is at the 05 bar position and there IS pressure in the system. Warning - It should be noted that with no pressure in the system (i.e. accumulator discharged) an engine start is possible with the Rotor Brake lever at the 2 bar (dynamic braking) position and this will lead to drastic results once pressure builds up in the system. It is therefore imperative that the start checks are carried out in their entirety. 3 of 30

14 Rotor Brake Rotor Brake OFF OFF ON 2 Bar Dynamic Braking 05 Bar Static Braking 05 bar Authorisatio n Spring 05 bar 2 bar Stop 2 bar Limiting Lock + RB SAFE 05 bar Static Braking 2 bar Dynamic Braking ON + ROT BR OFF OFF Return to Left-Hand Reservoir Pressure >2.5 bar Relief Valve >230 bar Pressure from Left-hand Hydraulic System 75 bar Return to Left-Hand Reservoir Pressure Reducing Valve Safety Valve Figure 0 Rotor Brake System Rotor Brake 4 of 30

15 Limitations. Rotor Brake must not be applied until engines have been shut down. 2. Max Nr for brake application is 20 RPM. 3. Rotor brake must not be applied twice within 5 minutes. If so applied then a cooling down period of 5 minutes, including 0 minutes rotor turning, must elapse before a third application. 4. If the wind speed is above 30 Kts the rotor brake must be ON for starting. 5. If starting with the rotor brake ON, the brake must be released by 23, 250 Ng or as soon as it starts slipping. 6. Only one engine may be started with the brake ON. 7. Running time with brake applied is limited to 5 minutes. Operating Procedures For normal starting the Rotor Brake Lever and the Safety Lever are both placed in the forward OFF gate prior to first engine start. Ensure that the RB SAFE and ROT BR lights are both out. For strong wind starts (30 knots and above) the following procedures should be used. Pre-Start Aux Hydraulic Pump On (pressure normal) Accumulator Pressure bar minimum (Re-pressurise with hand-pump if necessary) Rotor Brake Release 05 bar Authorising Lever Down CWP ROT BR Caption Out Rotor Brake Dynamic Braking Position CWP ROT BR Caption On 05 bar Authorising Lever Up Rotor Brake Static braking Position First Engine Start - Check rotor does not rotate. If rotor starts to turn - shut down the engine. 2. If engine speed at ground idle is less than 2,000 Ng, adjust to between 2,000 and 22,000 Ng using the speed select lever. 3. If rotation commences after reaching ground idle, release the rotor brake fully and accelerate the engine. Rotor Starting Cyclic Maintain in neutral position Rotor Brake Release to Full Forward position - check ROT BR light out 05 Bar Authorisation Lever Confirm down Safety Lever Release to Full Forward position - check RB SAFE light out Speed Select Lever Advance to Flight Position using approximately 35% torque Note -. Correct inhibition of engine starting is dependent on the accumulator being pressurised. This pressure must be checked prior to all starts. 2. When releasing the brake lever from the fully aft 'static' position, take care not to allow the lever to slip into the 'dynamic' detent and check that the ROT BR caption extinguishes. 3. The static braking detent must not be used for rotor stopping. 4. With the start inhibiting system the engine over-speed test will fail if the rotor brake lever is not in the static brake position or fully off. 5 of 30

16 Audio Warning System The aural warning unit consists of a small metal box mounted on the bulkhead behind the left-hand pilot s seat containing a logic circuit and a sounder. Located on the outer surface of the box are a -amp circuit breaker and a Test Button. Power for the system is supplied from the 28V DC essential bus via a 2-amp circuit breaker. The sounder emits a fast sweeping tone of 2,400 to 2,850 Hz, which is broadcast directly into the cockpit. The audio level of the sounder is considered to be sufficiently high (6 db at meter) and penetrative to be heard clearly by a pilot wearing a headset and earplugs with the engines and rotors running. The tone is not transmitted through the headset. The aural warning system uses four sensors, each of which detects two conditions. See the table below. Sensor Condition Condition 2 Comments RH Hyd Pressure > 80 bar < 80 bar Same as RHP caption 2 Rotor Brake Pressure > 2.5 bar < 2.5 bar Same as ROT BR Caption 3 No Engine SSL Fully Aft Not Fully Aft 4 No 2 Engine SSL Fully Aft Not Fully Aft For the aural warning to sound, the following three conditions must be satisfied. Right-Hand Hydraulic pressure >80 bar (The rotor must be turning fast enough to produce 80 bar) 2. Rotor Brake Pressure >2.5 bar (There must be pressure in the rotor brake system) 3. Either No. or No. 2 engine SSL must be forward of the Shut-off gate. (This must be sensed to prevent the warning coming on during normal rotor braking after engine shut-down) The warning will operate if, during a high wind start, the rotor brake lever is moved from the 05 bar (fully aft) position and placed inadvertently in the 2 bar gate rather than to the OFF (fully forward) position. It should not operate during shut-down provided that both SSLs have been pulled fully back. If the rotor is accelerated rapidly following brake release during a high wind start, a brief chirp may be emitted from the sounder if the RH P caption extinguishes before the ROT BR caption. This may be ignored. Aural Warning System Testing No requirement exists for the system to be tested by the crew. However the system can be tested with the following procedure. 28V DC Essential Bus Energise Rotor Brake OFF Speed Select Lever Either one open to break Micro Switch Test Button (under side of box) Press and Hold Aural alarm will sound Speed Select Lever Close Fully Aural alarm will stop 6 of 30

17 MAIN ROTOR HEAD General The Main Rotor Head is a fully articulated head, with oil lubricated bearings, attached to the Main Gearbox by a flared conical housing and driven by a steel shaft splined into the second stage epicyclic gear train of the MGB. The 4 Rotor Blades are attached to the head. Hinge Lubrication System Top Fairing Pitch Change Sleeve and Spindle Assembly Frequency Adapter Blade Horn Combined Drag and Flapping Hinge Pitch Change Rod Automatic Droop Stop and Coning Restrainer Limitations Figure - Main Rotor Head Rotor RPM Power On Rotor RPM Power Off Normal Governed Range Maximum Maximum Transient Maximum Minimum 265 RPM (22,850 Nf) RPM 290 RPM 30 RPM 290 RPM 220 RPM at 00 kts & below 245 RPM above 00 kts Over-Speed Alarm Under-Speed Alarm > 290 RPM RPM 7 of 30

18 Pitch Limitations Level Flight 5½ (However pitch may be increased to 6 in order to obtain 62% Torque) Climbing Maximum Limit 7 Total travel limit set at - 9 Limit with Autopilot not fully functional 5½ The components comprising the Rotor Head assembly are shown in Figure with a sectional internal view in Figure Figure 2 Main Rotor Head 8 of 30

19 Key for Figure 2. Frequency Adapter Fitting Attachment. 4-Contact Point Bearings 2. Ball Joint for cyclic pitch change 2. Pitch Transmitter 3. Rotating Scissors 3. Non Rotating Star 4. Swashplate Guide 4. Bearing on Non Rotating Star 5. Non Rotating Scissors 5. Rotating Star 6. MGB Suspension Attachment 6. Bearing on Non Rotating star 7. Phonic Wheel for Nr detection 7. Pitch Change Rod 8. Oil Breather 8. Rotating Scissors drive adapter 9. Magnetic sensor for phonic wheel 9. Rotor Shaft 0. Magnetic Plug (chip detector for bearing) Rotor Shaft The one-piece steel shaft includes an upper flange forming the top support for the flapping and drag hinges. The bottom support for these being a titanium plate bolted to the steel shaft. Integral with the shaft are attachment points for the drag dampers and bolted to a flange on the shaft is the rotating scissors drive tube. The shaft is supported at its bottom end by a double ball bearing. During flight this bearing transmits the rotor lift to the conical housing and thence the airframe via the steel support tubes. The bearing is lubricated by gearbox oil via an internal drilling through the conical housing. Sleeve Spindle Assembly This steel assembly forms the attachment for the blades to the head and constitutes the pitch change bearing. The pre-stressed bearing assembly is lubricated by oil Aeroshell 5MA from the reservoirs on the head. At one end the blades are attached by 2 steel pins and at the other end the lugs are assembled to the flapping/drag hinge by a torque loaded pin which rotates in needle bearings forming the flapping hinge. The end of this is connected to the drag damper. Anti-friction washers are fitted between the sleeve spindle and the hinge. The whole assembly is balanced by lead shot in a box at the blade end. A Vernier scale fitted to the assembly enables correct rigging of the blade pitch when setting up the controls. The horn on the leading edge is connected to the upper end of the pitch change rod Spindle 2. Vernier Scale 3. Spindle Nut 4. MRH Balancing Shot Filler Plug 5. Blade Sleeve 6. Blade Pin 7. Shot Pack (Weight Balancing) 8. Magnetic plug 9. Protective Plug 0. Bearing. Eye Bolt 2. Blade Horn 3. Pitch Change Rod 4. Bearing Figure 3 Sleeve & Spindle Assembly 9 of 30

20 Filler Plug 2. Reservoir Attachment Clamp 3. Magnetic Plug 4. Bleed vent Plug 5. Hose 6. Reservoir Figure 4 Hinge Lubrication 3 3 Flapping and Dragging Hinge Mounted between the upper and lower support flanges the drag hinge moves on tapered and needle bearings lubricated by a feed from the oil reservoir on top. A magnetic plug is fitted at the lower end for maintenance purposes. The flapping hinge is formed by the pin passing through the spindle lugs and the drag hinge assembly. Pitch Change Rods Attached by a bearing arrangement at upper and lower ends the rods transmit the swashplate movements to the blades. By undoing a lock nut at the bottom end and rotating the centre of the rod, variations in blade pitch angle can be made when setting up the controls or adjusting tracking of the blades. An indicator on the rod is lined up upon initial setting up and by means of a serrated washer small variations from this setting can be made. (2 notches = of pitch). Swash Plate Consists of a rotating plate and non-rotating plate coupled together by two ball bearing races. The nonrotating plate is mounted on a uniflex bearing which allows it to slide up and down a guide around the rotor shaft (Collective Pitch variations) and to pivot about a ball joint (cyclic pitch variations). It is prevented from turning by the fixed scissors and attached to the underside is the Collective Pitch transmitter. The rotating plate is driven by the two rotating scissor links and follows all movements of the fixed plate which is controlled by action of the 3 hydraulically operated main servo controls. The lower ends of the pitch change rods are attached to the rotating plate and transmit all movement of the swash plate to the sleeve spindles and hence blades. 20 of 30

21 Frequency Adapters Consisting of a sandwich of light alloy strips and layers of elastomer bonded together, these are attached between the mast and the flapping hinge pins to dampen the blade oscillations about the drag axis. A safety bobbin is fitted through the layers to prevent full separation of plates should the bonding fail completely Attachment Bolt on rotor shaft lug 4 2. Lug on rotor shaft 3. Elastomer 4. Light Alloy Strips 5. Flapping Hinge Pin Figure 5 Frequency Adapter 2 of 30

22 Rotors Stationary Rotors Spinning +30º -3º Flyweight Link Flyweight Return Spring Flyweight Return Spring Link Link Flyweight Figure 6 Coning Restrainers Automatic Coning Restrainers These prevent the blades from flapping in high winds when the rotor is stationary. Under action of centrifugal force the weights move outwards and enable the blades to flap to a maximum of 30. They are illustrated on Figure of 30

23 Automatic Droop Stops These limit the droop of the blades when Rotor is at low RPM (prevent damage to the tail boom) to minus 3. As the weights move out under centrifugal force downward flapping is allowed to increase to minus 6 maximum. Both the coning restrainers and the droop stops are protected by a fairing to prevent icing up in the outward position. They are illustrated on Figure 7. Rotors Stationary -3º Rotors Spinning -6º Flyweight Flyweight Return Spring Flyweight Return Spring Flyweight Flyweight Figure 7 Automatic Droop Stops 23 of 30

24 Figure 8 Main Rotor Blade Construction 24 of 30

25 Key to Figure 8. Skin (carbon fabric-glass cloth) 2. Leading Edge Protection (stainless steel) 4 elements 3. Spar (glass cloth-resin roving) 4. Tip Counterweight 5. Core (nomex honeycomb) 6. Built-in Weight 7. Dynamic Balance Weight 8. Static Balance Weight 9. Tracking Finger 0. Blade Tip Cap. Wedge (glass-resin compound) 2. Blade Folding Stop 3. Root wedge (glass resin compound) 4. Root Reinforcing Piece (glass cloth resin) 5. Blade Attachment Bushing 6. Filler Block (resin-moltoprene compound) 7. Filler (hard moltoprene foam) 8. Filler (moltoprene foam) 9. Glass Cloth Resin 20. Tab 2. Trailing Edge Strip Reinforcement 22. Trailing Edge Strip (carbon fabric) Main Rotor Blades The blades basically consist of a fiberglass resin laminate material brought to the solid state by curing. Each blade is balanced statically and dynamically and is also balanced for lift against a Master Blade. An Incidence correction value is marked on the blade root and has to be taken into account when rigging to ensure each blade develops the same lift. The leading edges are protected by a stainless steel strip and trim tabs on the trailing edge allow for slight adjustments of dynamic balancing. The blades have a tapered section and a twist of 9 37 along their length. Blade Length - Chord - Weight - 7 metres 600 mm 85.6 Kg The spar consists of a moltoprene filling with resin fiberglass rovings around the attachment bushes. The blade is filled with a honeycomb type resin. Icing protection can be fitted to the blades as an optional extra. Main Rotor Monitoring Pitch The collective pitch is indicated on the instrument panel by a gauge (see Figure 2) receiving its information from the transmitter under the swashplate. The power supply for this is 5V single phase AC from bus XP2A. 25 of 30

26 Rotor Speed (Nr) There are 2 gauges and 2 warning lights in the cockpit monitoring Nr and receiving signals from the sensors and phonic wheel on the Rotor mast. The left-hand sensor transmits directly to the Co-pilots Nr gauge which, being fully self-contained, requires no electrical power in order to operate and is always available. The right-hand sensor requires DC power supply in order to operate (Buses PP5 and 2PP6) and supplies information to the Triple Nr/Nf gauge on the Captain's instrument panel and also the MAX NR & MIN NR warning lights. The MAX NR and MIN NR warnings consist of 2 steady red lights on the instrument panel and associated audio warnings. (These lights do not operate the ALARM attention getter). The MIN NR light and 600Hz audio warning operates between 200 and 245 Rotor RPM. The MAX NR light and 200Hz audio warning operates above 290 Rotor RPM. Note The audio warning must be switched on for audio warnings to operate RH Magnetic Sensor LH Magnetic Sensor Phonic Wheel Rotor Shaft Figure 9 Nr Sensor Location TAIL ROTOR DRIVE SYSTEM Power is transmitted from the Main Gearbox to the Tail Rotor via tubular shafts and two gearboxes each of which reduce RPM and change direction of the drive. The system is made up of Horizontal Drive Shaft, Intermediate Gearbox (IGB), Inclined Drive Shaft and Tail Gearbox (TGB). Horizontal Drive Shaft Mounted on vibration absorbing bearings the drive consists of seven tubular shafts, coupled together with packs of flexible stainless steel shims, rotating at 4,888 RPM. The front shaft is made of steel and is attached by a flexible coupling to the MGB. The other shafts are of light alloy with the rear shaft being secured to the IGB by a flexible coupling. The flexible couplings compensate for slight misalignments along the shaft run. All shafts are factory balanced. 26 of 30

27 Intermediate Gearbox The magnesium alloy casing houses an input pinion and output wheel secured to the casing by bearing races. The drive is reduced from 4,888 RPM to 3,75 RPM and direction changed through 40 from input to output. The gears are splash lubricated by oil (Aeroshell 555) which is contained in the casing. The oil supply to the inclined drive bearings is achieved by means of a helical oil groove. The oil is cooled by airflow over the casing. A filler cap and level sight glass are fitted for oil replenishment and quantity checking, the sight glass being viewed from the right-hand side of the aircraft without removing cowlings. A temperature transmitter, fitted in the casing, transmits the oil temperature to a gauge on the Multiple Instrument Panel (Maximum 20 C). A magnetic plug and boroscope inspection hole plug are fitted for maintenance purposes, there being no indication in the cockpit of metal particles on the magnetic plug Output Flange 2. Hoisting Eye 3. Filler Cap 4. Casing 5. Input Flange 6. Mounting Lug 7. Temperature Sensor 8. Magnetic Drain Plug 9. Oil Level Sight Glass 0. Boroscope Orifice. Cover Figure 20 - Intermediate Gearbox Inclined Drive Shaft A one-piece light alloy shaft attached to IGB and TGB by flexible couplings Casing 2. Filler Cap 3. Boroscope Orifice 4. Input Flange 5. Oil Temperature Probe 6. Magnetic Drain Plug 7. Cover 8. Oil Level Sight Glass 9. Output Shaft Figure 2 - Tail Rotor Gearbox of 30

28 Tail Gearbox Refer to Figure 2. Constructed of magnesium alloy, the TGB houses a spiral bevel gear pinion and wheel retained in the casing by bearing races. The drive is reduced from 3,75 RPM to,279 RPM and the direction changed through 90. The gears are splash lubricated and the oil cooled by airflow over the casing. An impeller wheel on the inclined input shaft ensures oil supply to the bearings and gears. The output drive is coupled to the Tail Rotor Hub and passing through this drive shaft is the Tail Rotor Servo control actuator rod. The Servo control unit is attached to the left-hand side of the TGB. A filler cap and sight level glass enable the oil contents to he entered and monitored. The sight level glass can be viewed from the right-hand side of the aircraft without removing cowlings. A Temperature sensor transmits oil temperature to a gauge in the cockpit on the Multiple Instrument Panel. (Max 20 C). A magnetic plug and boroscope inspection plug are fitted for maintenance purposes. Tall Rotor Driven by the TGB at,279 RPM the 5 bladed Tall Rotor compensates for the torque reaction or the Main Rotor and enables control in the yaw axis. The head comprises a rotor hub and five sleeve spindle assemblies which enable blade flapping and blade pitch variations. The blade horns are connected by links to the pitch change spider, which is coupled up to the actuating rod of the Tall Rotor Servo control. Thus as the spider is moved in or out by the servo control the pitch of each blade is adjusted. Out for pitch reduction. The spindles and hinges are lubricated by grease applied through the grease nipples Figure 22 Tail Rotor Head 28 of 30

29 Key for Figure 22. Balancing Washer 2. Sleeve 3. Spindle 4. Rotor Hub 5. Rotor Shaft 6. Lubricator for Flapping Hinge 7. Blade Horn 8. Pitch Change Link 9. Rubber Boot 0. Pitch Change Spider Tail Rotor Blades Similar in construction to the Main Rotor Blades the leading edges are protected by a Titanium strip and the filling is a light foam. The blades have a twist along their length of 5. Blade Length - Chord - Weight - Rotor Diameter - Direction of Rotation Metres 200 mm 3.24 Kg 3.04 Metres Anti-clockwise Viewed from right-hand side Ice protection can be fitted to the blades as an optional extra. 29 of 30

30 INTENTIONALLY BLANK 30 of 30