Rotorcraft Flying Handbook, FAA-H-8083-21

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By knowing the various systems on a helicopter, you will be able to more easily recognize potential problems, and if a problem arises, you will have a better understanding of what to do to correct the situation. Intake Valve Exhaust Valve ENGINES The two most common types of engines used in helicopters are the reciprocating engine and the turbine engine. Reciprocating engines, also called piston engines, are generally used in smaller helicopters. Most training helicopters use reciprocating engines because they are relatively simple and inexpensive to operate. Turbine engines are more powerful and are used in a wide variety of helicopters. They produce a tremendous amount of power for their size but are generally more expensive to operate. RECIPROCATING ENGINE The reciprocating engine consists of a series of pistons connected to a rotating crankshaft. As the pistons move up and down, the crankshaft rotates. The reciprocating engine gets its name from the back-and-forth movement of its internal parts. The four-stroke engine is the most common type, and refers to the four different cycles the engine undergoes to produce power. [Figure 5-1] Spark Plug Piston Connecting Rod Crankshaft 1 Intake 2 Compression When the piston moves away from the cylinder head on the intake stroke, the intake valve opens and a mixture of fuel and air is drawn into the combustion chamber. As the cylinder moves back towards the cylinder head, the intake valve closes, and the fuel/air mixture is compressed. When compression is nearly complete, the spark plugs fire and the compressed mixture is ignited to begin the power stroke. The rapidly expanding gases from the controlled burning of the fuel/air mixture drive the piston away from the cylinder head, thus providing power to rotate the crankshaft. The piston then moves back toward the cylinder head on the exhaust stroke where the burned gasses are expelled through the opened exhaust valve. Even when the engine is operated at a fairly low speed, the four-stroke cycle takes place several hundred times each minute. In a four-cylinder engine, each cylinder operates on a different stroke. Continuous rotation of a crankshaft is maintained by the precise timing of the power strokes in each cylinder. 3 Power 4 Exhaust Figure 5-1. The arrows in this illustration indicate the direction of motion of the crankshaft and piston during the fourstroke cycle. TURBINE ENGINE The gas turbine engine mounted on most helicopters is made up of a compressor, combustion chamber, turbine, and gearbox assembly. The compressor compresses the air, which is then fed into the combustion chamber where atomized fuel is injected into it. The fuel/air mixture is ignited and allowed to expand. This combustion gas is then forced through a series of turbine wheels causing them to turn. These turbine wheels provide power to both the engine compressor and the main rotor system through an output shaft. The 5-1
Compression Section Gearbox Section Turbine Section Combustion Section Exhaust Air Outlet Stator Rotor Igniter Plug Air Inlet Compressor Rotor Gear Turbine to Compressor Coupling N2 N1 Combustion Liner Fuel Nozzle Compressor Discharge Air Tube Output Shaft Inlet Air Compressor Discharge Air Combustion Gasses Exhaust Gasses Figure 5-2. Many helicopters use a turboshaft engine to drive the main transmission and rotor systems. The main difference between a turboshaft and a turbojet engine is that most of the energy produced by the expanding gases is used to drive a turbine rather than producing thrust through the expulsion of exhaust gases. combustion gas is finally expelled through an exhaust outlet. [Figure 5-2] COMPRESSOR The compressor may consist of an axial compressor, a centrifugal compressor, or both. An axial compressor consists of two main elements, the rotor and the stator. The rotor consists of a number of blades fixed on a rotating spindle and resembles a fan. As the rotor turns, air is drawn rearwards. Stator vanes are arranged in fixed rows between the rotor blades and act as a diffuser at each stage to decrease air velocity and increase air pressure. There may be a number of rows of rotor blades and stator vanes. Each row constitutes a pressure stage, and the number of stages depends on the amount of air and pressure rise required for the particular engine. A centrifugal compressor consists of an impeller, diffuser, and a manifold. The impeller, which is a forged disc with integral blades, rotates at a high speed to draw air in and expel it at an accelerated rate. The air then passes through the diffuser which slows the air down. When the velocity of the air is slowed, static pressure increases, resulting in compressed, high-pressure air. The high pressure air then passes through the compressor manifold where it is distributed to the combustion chamber. COMBUSTION CHAMBER Unlike a piston engine, the combustion in a turbine engine is continuous. An igniter plug serves only to ignite the fuel/air mixture when starting the engine. Once the fuel/air mixture is ignited, it will continue to burn as long as the fuel/air mixture continues to be present. If there is an interruption of fuel, air, or both, combustion ceases. This is known as a “flame-out,” and the engine has to be restarted or re-lit. Some helicopters are equipped with auto-relight, which automatically activates the igniters to start combustion if the engine flames out. TURBINE The turbine section consists of a series of turbine wheels that are used to drive the compressor section and the rotor system. The first stage, which is usually referred to as the gas producer or N 1 may consist of one or more turbine wheels. This stage drives the components necessary to complete the turbine cycle making the engine self-sustaining. Common components driven by the N 1 stage are the compressor, oil pump, and fuel pump. The second stage, which may also consist of one or more wheels, is dedicated to driving the main rotor system and accessories from the engine gearbox. This is referred to as the power turbine (N 2 or N r ). 5-2
Page 2: ROTORCRAFT FLYING HANDBOOK 2000 U.S
Page 6 and 7: HELICOPTER Chapter 1—Introduction
Page 8 and 9: Technique..........................
Page 10 and 11: Collision Avoidance at Night.......
Page 12 and 13: Helicopters come in many sizes and
Page 14 and 15: Main Rotor Wake Air Jet Downwash Li
Page 16 and 17: There are four forces acting on a h
Page 18 and 19: Increased Local Velocity (Decreased
Page 20 and 21: Load Factor - "G's" 9 8 7 6 5 4 3 2
Page 22 and 23: Once a helicopter leaves the ground
Page 24 and 25: otation and blade deceleration take
Page 26 and 27: lift and thrust are greater than we
Page 28 and 29: Relative Wind Retreating Side Blade
Page 30 and 31: Bank Angle Vertical Component of Li
Page 32 and 33: percent of the radius. In the drive
Page 34 and 35: Note: In this chapter, it is assume
Page 36 and 37: The rotor disc tilts in the directi
Page 40 and 41: If the first and second stage turbi
Page 42 and 43: The horizontal hinge, called the fl
Page 44 and 45: RECIPROCATING ENGINES Fuel is deliv
Page 46 and 47: incorporated to prevent excessive v
Page 48 and 49: depends on the temperature of the o
Page 50 and 51: Title 14 of the Code of Federal Reg
Page 52 and 53: l0 5 l5 20 25 30 35 MANIFOLD PRESSU
Page 54 and 55: It is vital to comply with weight a
Page 56 and 57: sive forward displacement of cyclic
Page 58 and 59: Once you are satisfied that the tot
Page 60 and 61: Basic Empty Weight Pilot Fwd Passen
Page 62 and 63: Your ability to predict the perform
Page 64 and 65: Approximate Density Altitude - Thou
Page 66 and 67: the entire flight operation. Being
Page 68 and 69: From the previous chapters, it shou
Page 70 and 71: 2. brief passengers on the best way
Page 72 and 73: VERTICAL TAKEOFF TO A HOVER A verti
Page 74 and 75: Control pressures and direction of
Page 76 and 77: HOVER TAXI A "hover taxi" is used w
Page 78 and 79: 3. Assuming an extreme nose-down at
Page 80 and 81: tain altitude and r.p.m. As the tor
Page 82 and 83: Start Turn At Boundary Turn More Th
Page 84 and 85: the helicopter is being crabbed int
Page 86 and 87: APPROACHES An approach is the trans
Page 88 and 89:
The maneuvers presented in this cha
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TECHNIQUE Refer to figure 10-2. To
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COMMON ERRORS 1. Failing to maintai
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Figure 10-7. Slope takeoff. be cons
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made in the forward portion of the
Page 98 and 99:
Today helicopters are quite reliabl
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After touchdown and after the helic
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HEIGHT ABOVE SURFACE - FEET 500 450
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helicopter, while the relative airf
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When performing slope takeoff and l
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the main rotor blades having an ang
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WEATHERCOCK STABILITY (120-240°) I
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LOW FREQUENCY VIBRATIONS Low freque
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Attitude instrument flying in helic
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ways. If the ram air inlet is clogg
Page 118 and 119:
to true north. Because the aircraft
Page 120 and 121:
AIRCRAFT CONTROL Controlling the he
Page 122 and 123:
vertical speed indicator immediatel
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POWER CONTROL DURING STRAIGHT-AND-
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50 60 70 80 40 TORQUE 90 30 100 20
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to the approximate setting for the
Page 130 and 131:
used, the rate of cross-check must
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AUTOROTATIONS Both straight-ahead a
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{ { Flying at night can be a very p
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White Red Red White Green Red Green
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you are operating off-airport, you
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Aeronautical decision making (ADM)
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THE DECISION-MAKING PROCESS An unde
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Night VFR Accident Rate Per 100,000
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STRESSORS Physical Stress—Conditi
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OPERATIONAL PITFALLS Peer Pressure
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January 9th, 1923, marked the first
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LANDING GEAR The landing gear provi
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Helicopters and gyroplanes both ach
Page 156 and 157:
elative wind striking the advancing
Page 158 and 159:
subject to pendular action in the s
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Due to rudimentary flight control s
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Gyroplanes are available in a wide
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Figure 18-4. This prerotator uses b
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inability to use differential braki
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As with most certificated aircraft
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8 TOTAL TAKEOFF DISTANCE TO CLEAR 5
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The diversity of gyroplane designs
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minimize the length of the ground r
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adjust the fuel/air mixture to achi
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maximum performance is desired, two
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Start Turn At Boundary Turn More Th
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Shallowest Bank UPPER HALF OF CIRCL
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of failing to monitor and maintain
Page 186 and 187:
for the gyroplane. When using the s
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Gyroplanes are quite reliable, howe
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BUNTOVER (POWER PUSHOVER) As you le
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As with any aircraft, the ability t
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leaves few places to safely land in
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GLOSSARY ABSOLUTE ALTITUDE—The ac
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FREE TURBINE—A turboshaft engine
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TRANSLATIONAL LIFT—The additional
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A ABORTED TAKEOFF, GYROPLANE 21-1 A
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turn indicators, 12-4 GYROSCOPIC PR
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R RAPID DECELERATION 10-3 RECIPROCA
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Rotorcraft Flying Handbook, FAA-H-8083-21

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