EFFECTS OF CONTROLS
1. This exercise introduces you to the helicopter controls and their functions. If you have flown fixed wing aircraft you will see that there is a resemblance to some of those you have already used, others will be unfamiliar to you. In addition you will be shown the indications and uses of the instruments and avionics.

AIRMANSHIP
2. Although the exercise itself will absorb most of your concentration it is important you that you learn to keep a check on your position within the local area, maintain a good lookout for other aircraft and make routine checks of engine temperatures, pressures and fuel state. This is best achieved by developing a scan sequence which regularly covers the engine and flight instruments, external reference and lookout.

3. During the demonstration you will be asked to 'follow through on the controls'. It is important that you don't override your instructor. When the instructor wants you to take control, he will say 'you have control'. You will then take hold of the nominated control(s) and say 'I have control'. The reverse is true when the instructor requires to retake control. NEVER release the controls until the instructor has acknowledged: 'I have control'. This is particularly necessary in the case of the cyclic because of the rocking 'T' bar arrangement which means the instructor has to reach up for his cyclic handgrip.

THE CONTROLS
4. The Cyclic Stick. The cyclic controls the rotor disc attitude directly and indirectly controls the fuselage attitude. The control feels very light and only small movements are required. You will find it convenient to lower the cyclic handgrip so that you can rest your forearm on your leg and damp out unnecessary control movements. The cyclic stick is not self centering and in cruise flight a slight pressure to the right would need to be maintained to maintain the helicopter laterally level. To offset this force a pull up trim knob is on the centre console and when pulled, applies a small spring pressure to the cyclic (not normally required below 75Kts). Friction can be applied by means of knurled knob on the lower console but is not used other than on the ground to lock the cyclic. Longitudinal cyclic forces are balanced by an non-adjustable bungee spring.

5. Initially you should note the aircraft attitude by reference to the horizon position in the windscreen. As the cyclic is eased forward the aircraft pitches nose down, airspeed increases and the aircraft descends. The opposite effect occurs if the cyclic is moved backwards. Sideways movements of the cyclic causes the aircraft to roll followed by yaw and a turn in the same direction. In normal flight therefore, the operation of the cyclic stick produces the same effects as operation of the stick in a fixed wing aircraft.

6. The collective Lever. The lever increases or decreases the main rotor blades pitch simultaneously and therefore controls the total rotor thrust. A balance spring is incorporated in the linkage to offset a tendency for the lever to move downwards. Feel is proportional to the amount of friction applied by a small toggle lever near the aft end of the collective. If the collective is raised, not only is there an increase in total rotor thrust, there is also an increase in rotor drag. This would lead to a drop in rotor speed (RRPM). To offset this the collective is also connected to the engine throttle by a linkage. Thus, when the lever is raised the engine power is increased, shown on the manifold air pressure gauge (MAP) and RRPM remain approximately constant in the cruise power range. Similarly when the lever is lowered, MAP reduced and RRPM remain constant. However the change in engine power changes the torque force applied to the main rotor shaft causing the helicopter to yaw in the absence of corrective pedal movements. To summarise, raising the lever causes the helicopter to climb; MAP rises and the aircraft yaws to the right. Lowering the lever causes the aircraft to descend; MAP reduces and the aircraft yaws to the left.

7. The Twist grip Throttle. The throttle twist grip is very sensitive and is used to maintain the RRPM. It must be realised that the throttle linkage to the collective does not do a perfect job and in a sense the throttle twist grip is used as a trimmer to maintain exact RRPM. When the throttle is opened (away from you) MAP increases, RRPM increases and the extra torque causes a yaw to the right. Closing the throttle (towards you) reduces MAP, lowers RRPM and causes a yaw to the left.

8. Yaw Pedals. The pedals are very light and sensitive. Left pedal causes the nose to yaw to the left and the Yaw String to move to the left. The opposite effect will be noted when the right pedal is pushed. In forward flight however the yaw pedals are not used to turn the aircraft but to maintain balanced flight with the Yaw String in the centre, i.e. if the Yaw String is to the left, apply right pedal to centre it. The aircraft will then be flying most efficiently. Pedal movements change the collective pitch of the tail rotor, thus altering the power demanded by the tail rotor; hence application of the left pedal will cause the main RRPM to reduce and vice versa with right pedal. Flying out of balance will cause the airspeed to reduce.

You should note that aircraft equipped with a Balance Ball on the instrument panel display the effect in the opposite manner. Left pedal causes the ball to move to the right meaning apply right pedal and vice-versa.

EFFECTS OF AIRSPEED CHANGE ON RRPM
9. Your instructor will demonstrate that an increase in speed will cause the RRPM to rise and vice-versa with a fall in airspeed.

EFFECT OF DISC LOADING ON RRPM
10. It will also be demonstrated that if the aircraft is pulled out of a dive thus increasing disc loading the RRPM will rise sharply, conversely if the nose is then pushed down, reducing disc loading, the RRPM will fall. The disc is also loaded in a banked turn, causing RRPM rise. This rise can be very rapid if both effects i.e. bank and flare, are combined.

FURTHER EFFECTS OF LEVER AND THROTTLE
11. Sometime during the sortie your instructor will demonstrate the effects of lowering the lever completely. You will notice the MAP reduces and unless the lever is lowered quite quickly, the RRPM may also reduce, depending upon the aircraft, the RRPM may also reduce, depending upon the aircraft attitude. When the lever is lowered, a large amount of right pedal is needed to maintain balanced flight. With the lever fully down the engine needle will normally be indicating less than the rotor needle on the tachometer showing that the engine is no longer driving the rotor and the helicopter is in autorotation with the rotor freewheeling. If the throttle is now fully closed through the overtravel spring it will be noticed that raising and lowering the lever causes the RRPM to change but does not affect the MAP.

MIXTURE CONTROL
12. The mixture control is a push pull knob on the lower console. It is only used to lean the fuel/air mixture at high altitude and as an idle cut-off to stop the engine after flight. To prevent inadvertent operation in flight a collar is placed over the knob in flight.

CARBURETTOR AIR TEMPERATURE CONTROL
13. Also on the lower console is a push/pull control to provide hot air to the carburettor to prevent icing in the intake. Pulling the control provides hot air and a rise will be seen on the carburettor air temperature gauge, (CAT). The control is normally used in the cruise to maintain the CAT out of the yellow sector at ALL times.

ROTOR BRAKE
14. The rotor brake is used to stop the rotor after engine shutdown. The following procedure should be used:-

(a) After the idle cut-off wait at least 30 seconds (for the clutch light to extinguish).
(b) Pull the brake toggle (over the pilots left shoulder) using a moderate 10lbs force. Do not try to stop the rotor too quickly as applying the brake without waiting at least 30 seconds after engine stops, or using a force which stops the rotor in less than 20 seconds may be permanently damage the brake shoes.
(c) After rotor stops retract the toggle or if required as a parking brake, pull handle down and push bead chain into the slot.

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EXERCISE 5

ATTITUDE AND POWER CHANGES
1. In this exercise you will learn how to maintain a specified airspeed, how to change that airspeed by changing the fuselage attitude and the relationship of the cyclic position to airspeed. You will also learn how to make power changes and co-ordinate control movements to maintain balanced flight.

AIRMANSHIP
2. The main airmanship points on this exercise are:-

(a) Maintain a good lookout. This is especially important when climbing or descending.
(b) Keep a check on your location. Your instructor will point out landmarks.
(c) Monitor the engine instruments and fuel contents regularly. Develop a regular scan sequence,

LOOKOUT - LOCATION - INSTRUMENTS.

(d) Positive handover/take-over of the controls specified.
(e) Limitations - Engine/RRPM limits 97% - 104%. Maximum continuous power 23.3" MAP at 15 degrees C. Carburettor temperatures just above yellow sector (10-15 degrees C).

SPEED CHANGES Cyclic Only 40 - 80 knots
3. Speed Increase - Starting from balanced cruise flight you will be shown that to increase speed it is necessary to tilt the rotor disc further forward with the cyclic. This will result, as you have already been shown, in the nose dropping to a new attitude. As the aircraft accelerates the rotor disc will tend to 'flapback', so to maintain the acceleration it is necessary to move the cyclic progressively forward. On most light helicopters the nose will be seen to be lower for each increase in airspeed.

4. In the Robinson however the horizontal tail surfaces produce an increasing downforce with increase in speed and this tends to maintain the fuselage attitude relatively constant over a large part of the speed range. After a speed increase therefore the cyclic stick will be further forward but the nose attitude will be little different once the aircraft has accelerated.

5. Speed Decrease - To decrease speed, the disc is tilted back with the cyclic, the nose rises to a more nose up attitude and the aircraft slows down. As the speed falls the disc 'flaps' forward and the cyclic must be moved further back to maintain the deceleration. Once again, when the speed is close to that desired, the nose attitude is reselected to that which you think will maintain the required speed.

6. To Summarise - The technique for speed changes is to select the desired acceleration or decelerative nose attitude, hold that attitude by moving the cyclic as necessary, then adjust the nose attitude to maintain the new airspeed. (SELECT, HOLD, ADJUST). It must be understood that it takes a certain time for speed changes to occur and attempts to hurry the process as first may lead to overcontrolling. The aircraft is maintained in balanced flight by small movement of pedals.

7. Changing airspeed in the above exercise will of course lead to the aircraft climbing or descending but on this exercise this is accepted.

POWER CHANGES (Lever, Throttle and Pedals) - at constant RPM (102%)
8. The height of the helicopter is controlled by the collective lever. As you have seen in Exercise 4, when the lever is raised the power increases because of the correlator linkage to the throttle and the nose yaws to the right. The reverse is true if the lever is lowered. The correlator will maintain the RRPM approximately constant in the normal power range. To maintain heading, therefore use of the pedals is required when changing power. When the lever is lowered apply right pedal, when the lever is raised apply left pedal.

When the power is changed the relative airflow through the rotor disc is changed and without adjustment to the cyclic the attitude will change. When the lever is lowered the nose of the aircraft drops, rearward cyclic pressure therefore will prevent this. Similarly when the lever is raised forward cyclic pressure will prevent the nose rising.

9. To Summarise

When lowering the collective lever, look straight ahead and not at the instruments, be ready to apply right pedal and rear cyclic. When raising the lever be ready with left pedal and forward cyclic.

RRPM CHANGES AT CONSTANT MANIFOLD PRESSURE
10. It will be necessary to change your RRPM if for instance you have inadvertently allowed them to alter during normal flight.

(a) To increase RRPM with constant MAP - lead with throttle, resulting not only in increase of RRPM but also an increase in MAP. Lower lever until MAP reduces to original value. As a result you will have raised the RRPM without any overall change in MAP.
(b) To decrease RRPM with constant MAP - lead with throttle, resulting not only a decrease in RRPM but also a decrease in MAP. Raise the lever until MAP returns to the original figure.
11. It is important at this stage that all your control movements are slow and small until you are satisfied that you are correct in your actions. As you become more proficient your instructor will show you how to co-ordinate your use of lever and throttle into a single movement. You must also at the same time maintain your scan sequence -lookout instruments - temperatures and pressures - position.
12. In the event of a low RPM warning it is essential that the throttle is opened and simultaneously the lever lowered to prevent a dangerous low RPM condition developing.

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EXERCISE 6

LEVEL FLIGHT, CLIMBING, DESCENDING AND TURNS
The aim of this exercise is to utilise the speed control and power change techniques that we learned in the previous exercise, to achieve level balanced flight at specified airspeeds, climbs and descents to specified altitudes and to turn onto specific headings. You should by now have a reasonable knowledge of the local flying area. You will be expected to gradually assume more responsibility for checking your position and recognising when you may be approaching controlled airspace or approaching maximum, permissible heights. In your checks of fuel state you should also be checking that the fuel consumption conforms to the average 7.5 U.S. gallons per hour expected. Regular checks of temperatures and pressures must become second nature.

LEVEL FLIGHT (40 - 80 Kts)
1. The basic rules to remember are that the lever controls height and the cyclic controls attitude and hence speed. To achieve flight at a given airspeed:-
(a) Select the attitude to accelerate or decelerate to the desired speed.
(b) Check with the altimeter and VSI to see whether you are climbing or descending.
(c) Make an appropriate movement of the lever to correct the climb or descent to level flight, at the same time preventing yaw with the pedals and maintaining RPM with the throttle.
(d) Adjust attitude, power and yaw pedals as required to settle accurately in level flight at the correct airspeed with the slip ball in the middle.
(e) It will be noticed that the attitude is not significantly different between 40 - 80 kts once the speed is stabilised.

CLIMB
2. Climbing Configurations
(a) Best Rate of Climb - Best rate of climb is achieved at the speed which gives the greatest power margin (53 knots), using maximum permitted power, 24.3" MAP at 15 (C, sea level.
(b) The Standard Climb - The standard climb is carried out at 60 kts and maximum continuos power, 23.3" MAP at 15c, sea level. Any variations from these ambient conditions will require the figure to be obtained from MAP limit placard.
(c) Entry to the Climb - Before climbing check that the airspeed above is clear. From straight and level at 70 kts make a nose up attitude change to reduce speed to 60kts. This will initiate the climb. Then, smoothly raise the lever to achieve climbing power, at the same time preventing yaw. Make small adjustments as necessary when established in the climb. (ATTITUDE, POWER). Check balance at T's and P's.
(d) Level off from the Climb - Initially you should anticipate the level off by 10% of the rate of climb figure or you may overshoot the desired height. At this anticipation height, select a nose down attitude change to accelerate to 70 kts rate of climb will reduce. Progressively lower the lever to achieve the correct level off height, at the same time preventing yaw. Make adjustments as necessary. (ATTITUDE, POWER). Check balance and T's and P's. Average MAP for level flight at 70 kts is 20" at 102% RPM.

ROTOR POWER REQUIRED - SEE GRAPH

DESCENT
3. In this exercise you will practice the descent configuration which is used in the circuit descending at 60 kts and approximately 500 ft/min rate of descent.

(a) Entry to Decent - Before descending, make sure that the airspace below is clear. From straight and level at 70 kts lower the collective lever to initiate the descent, apply right pedal to prevent yaw. Power setting is approximately 13" MAP. At the same time apply rear cyclic to raise the nose to reduce airspeed to 60 kts. Make adjustments as necessary to maintain speed and rate of descent. (POWER ATTITUDE)
(b) Level off from Descent - You should anticipate the level off height by 10% rate of descent. At this anticipation height, progressively raise the lever, maintaining RPM, to cruise power which will arrest the rate of descent, at the same time prevent yaw. Lower the nose to accelerate to 70kts. Adjust as necessary to achieve level balanced flight at cruise speed. (POWER, ATTITUDE). Check balance and T's and P's.

TURNS IN LEVEL FLIGHT, CLIMBS AND DESCENTS
4. In this exercise, turns are practised at 15-20 degrees bank. Try to use a smooth rate of roll into and out of the turn and remember to maintain balance throughout. Height is maintained using the collective lever and speed is maintained with the cyclic as normal. Remember that the vertical position of the horizon in the windscreen will appear different in right and left hand turns due to the side to side seating in the Robinson. When carrying out climbing turns, the rate of climb reduces as bank increases, and for descending turns, rate of decent increases as bank angle increases.

5. You should anticipate the roll out of the turn by the same number of degrees as you have bank angle, e.g. anticipate rollout by 20 degrees of heading when turning with 20 degrees of bank.

6. Conclusion - After a good deal of practice the above exercises should become smooth co-ordinated movements of all controls simultaneously, but in the initial stages remember the sequence of actions laid down in paras 4 - 8.

James Tuke - Thurston Helicopters Ltd
The Aerodrome, Headcorn, Kent TN27 9HX Phone: 01622 891158
e-mail:mail@thurstonhelis.co.uk

Copyright © February 1996 James Tuke/Thurston Helicopters, Revised -- 02 Feb 1998
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