Chapter 3


Some of the following questions are in reference to the systems of a Cessna 172-RG.
A. Primary Flight Control and Trim
1. How are the various flight controls operated?The flight control surfaces are manually actuated through use of either a rod or cable system. A con troll wheel actuates the ailerons and elevator, and rudder/brake pedals actuate the rudder.2. What types of trim system is installed in this airplane?

Both rudder and elevator trim are provided. They are both manually actuated.

B. Wing Flaps, Leading Edge Devices, and Spoilers

1. What are flaps, and what is their function? (FAA-H-8083-3)

The wing flaps are movable panels on the inboard trailing edges of the wings. They are hinged so they may be extended downward into the flow of air beneath the wings to increase both lift and drag. Their purpose is to permit a slower airspeed and a steeper angle of descent during a landing approach. In some cases, they may also be used o shorten the takeoff distance.

2. Describe a typical wing flap system.

The wing flap system consists of “single-slot” type wing flaps. They are extended and retracted by a wing flap switch lever to flap settings of 10, 20, and 30 degrees. A 15-amp push-to-reset circuit breaker protects the wing flap system circuit.

3. State some examples of leading edge lift devices. (AC 65-15A)

Slots – A slot in the leading edge of a wing directs high-energy from under the wing to the airflow above the wing, accelerating upper airflow. By accelerating the airflow above the wing, airflow separation will be delayed to higher angles of attack. This allows the wing to continue to develop lift at substantially higher angles of attack.
Slats – A miniature airfoil mounted on the leading edge of a wing. They may be movable or fixed. At low angles of attack, movable slats are held flush against the leading edge by positive air pressure. At high angles of attack, the slats are moved forward either by pilot or automatically by the low pressures present at the leading edge. Slats provide the same results as slots.

4. What are spoilers? (AC 65-15A)

Spoilers are devices located on the upper surface of a wing which are designed to reduce lift by “spoiling” the airflow above the wing. They are typically used as speed brakes to slow an airplane down, both in flight as well as on the ground immediately after touchdown.

C. Pilot / Static Flight Instruments

1. What instruments operate from the pitot / static system? (FAA-H-8083-15)

The pilot / static system operates the altimeter, vertical speed indicator, and airspeed indicator.

2. Does this aircraft have an alternate static air system?

Yes, in the event of external static port blockage, a static pressure alternate source valve is installed. The control is located beneath the throttle, and if utilized will supply static pressure from inside the cabin, instead of from the external static ports.

3. How does an altimeter work? (FAA-H-8083-15)

Aneroid wafers expand and contract as atmospheric pressure changes, and through a shaft and gear linkage, rotate pointers on the dial of the instrument.

4. A pressure altimeter is subject to what imitations? (FAA-H-8083-15)

Non-standard pressure and temperature:
a. Temperature variations expand or contract the atmosphere and raise or lower pressure levels that the altimeter senses.

On a warm day – The pressure level is higher than on a standard day. The altimeter indicates lower than actual altitude.
On a cold day – The pressure level is lower than on a standard day. The altimeter indicates higher than actual altitude.

b. Changes in surface pressure also affect pressure levels at altitude.

Higher than standard pressure – The pressure level is higher than on a standard day. The altimeter indicates lower than actual altitude.
Lower than standard pressure – The pressure level is lower than on a standard day. The altimeter indicates higher than actual altitude.

Remember : High to low or hot to cold, look out below!

5. Define and state how you would determine the following altitudes. (FAA-H-8083-25)

Indicated altitude – the altitude read directly from the altimeter (uncorrected) after it is set to the current altimeter setting.
Pressure altitude – the altitude when the altimeter setting window is adjusted to 29.92. Pressure altitude is used for computer solutions to determine density altitude, true altitude, true airspeed, etc.
True altitude – the true vertical distance of the aircraft above sea level. Airport, terrain, and obstacle elevations found on aeronautical charts are true altitudes.
Density altitude – pressure altitude corrected for non-standard temperature variations. Directly related to an aircraft’s take off, climb, and landing performance.
Absolute altitude – the vertical distance of an aircraft above the terrain.

6. How does the airspeed indicator operate? (FAA-H-8083-25)

It measures the difference between impact pressure from the pilot head and atmospheric pressure from the static source.

7. What are the limitations of the airspeed indicator? (FAA-H-8083-25)

The airspeed indicator is subject to proper flow of air in the pitot / static system.

8. The airspeed indicator is subject to what errors?

Position error – Caused by the static ports sensing erroneous static pressure; slipstream flow causes disturbances at the static port preventing actual atmospheric pressure measurement. It varies with airspeed, altitude and configuration, and may be a plus or minus value.

Density error – Changes in altitude and temperature are not compensated for by the instrument.

Compressibility error – Caused by the packing of air into the pitot tube at high airspeeds, resulting in higher than normal indications. It is usually not a factor at slower speeds.

9. What are the different types of aircraft speeds? (FAA-H-8083-15)

True airspeed (TAS) –The speed of the airplane in relation to the air mass in which it is flying.

Indicated airspeed (IAS) – The speed of the airplane as observed on the airspeed indicator. It is the airspeed without correction for indicator, position (or installation), or compressibility errors.

Calibrated airspeed (CAS) – The airspeed indicator reading corrected for position (or installation), and instrument errors. (CAS is equal to TAS at sea level in standard atmosphere). The color-coding for various design speeds marked on airspeed indicators may be as IAS or CAS.

Equivalent airspeed (EAS) –The airspeed indicator reading corrected for position (or installation), or instrument error, and for adiabatic compressible flow for the particular altitude. (EAS is equal to CAS at sea level in standard atmosphere).

10. What airspeed limitations apply to the color-coded marking system of the airspeed indicator? (FAA-H-8083-25)

White Arc Flap operating range
Lower A/S Limit White Arc VS1 (stall speed clean or specified configuration)
Upper A/S Limit White Arc VFE(maximum flap extension speed)
Green Arc normal operating range
Lower A/S Limit Green Arc VS1(stall speed clean or specified configuration)
Upper A/S Limit Green Arc VNO(normal operations speed or maximum structural cruise speed)
Yellow Arc Caution Range (operations in smooth air only)
Red Line VNE (maximum speed for operations in smooth air only)

11. What are some examples of important airspeed limitations that are not marked on the face of airspeed indicator, but are found on placards and in the AFM or POH? (FAA-H-8083-25)

a. Design maneuvering speed (VA)
b. Landing gear operating speed (VLO)
c. Landing gear extended speed (VLE)
d. Best angle-of-climb speed (VX)
e. Best rate-of-climb speed (VY)

12. How does the vertical speed indicator work? (FAA-H-8083-15)

The vertical speed indicator is a pressure differential instrument. Inside the instrument case is an aneroid very much like the one in an airspeed indicator. Both the inside of this aneroid and the inside of the instrument case are vented to the static system, but the case is vented through a calibrated orifice that causes the pressure inside the case to change more slowly than the pressure inside the aneroid. As the aircraft ascends, the static pressure becomes lower and the pressure inside the case compresses the aneroid, moving the pointer upward, showing a climb and indicating the number of feet per minute the aircraft is ascending.

13. What are the limitations of the vertical speed indicator? (FAA-H-8083-25)

It is not accurate until the aircraft is stabilized. Sudden or abrupt changes in aircraft attitude will cause erroneous instrument readings as airflow fluctuates over the static port. Both rough control technique and turbulent air result in unreliable needle indications.

D. Gyroscopic Flight Instruments

1. Which instruments contain gyroscopes? (FAA-H-8083-25)

The most common instruments containing gyroscopes are the turn coordinator, heading indicator, and attitude indicator.

2. What are the two fundamental properties of a gyroscope? (FAA-H-8083-25)

Rigidity in space – A gyroscope remains in a fixed position if the plane in which it is spinning.
Precession – The tilting or turning of a gyro in response to a deflective force. The reaction to this force does not occur at the point where it was applied; it occurs at a point that is 90° later in the direction of rotation. The rate at which the gyro precesses is inversely proportional to the speed of the rotor and proportional to the deflective force.

3. What are the various power sources that may be used to power the gyroscopic instruments in an airplane? (FAA-H-8083-25)

In some airplanes, all the gyros are vacuum, pressure, or electrically operated: in others, vacuum or pressure systems provide the power for the heading and altitude indicators, while the electrical system provides the power for the turn coordinator. Most airplanes have at least two sources of power to ensure at least one source of bank information if one power source fails.

4. How does the vacuum system operate? (FAA-H-8083-25)

Air is drawn into the vacuum system by the engine-driven vacuum pump. It first goes through a filter, which prevents foreign matter from entering the vacuum or pressure system. The air then moves through the attitude and heading indicators, where it causes the gyros to spin. A relief valve prevents the vacuum pressure, or suction, from exceeding prescribed limits. After that, the air is expelled over board or used in other systems, such as for inflating pneumatic deciding boots.

5. How does the attitude indicator work? (FAA-H-8083-25)

The attitude indicator’s gyro is mounted on a horizontal plane (a bar representing true horizon) and depends upon the rigidity in space for its operation. The fixed gyro remains in a horizontal plane as the airplane is pitched or banked about its lateral or longitudinal axis, indicating the attitude of the airplane relative to the true horizon.

6. Discuss the limits of an altitude indicator? (FAA-H-8083-25)

Pitch and bank limits depend upon the make and model of the instrument. Limits in the banking plane are usually from 100°- 110°, pitch limits are usually from 60°-70°. If either limit is exceeded, the instrument will tumble or spill and will give incorrect indications until reset. Some modern attitude indicators will not tumble.

7. The attitude indicator is subject to what errors? (FAA-H-8083-15)

Attitude indicators are free from most errors, but depending upon the speed with which the erection system functions, there may be a slight nose-up indication during a rapid acceleration and a nose-down indication during a rapid deceleration. There is also a possibility of a small bank angle and pitch error after a 180° turn. These inherent errors are small and correct themselves within a minute or so after returning to straight-and-level flight.

8. How does the heading indicator operate? (FAA-H-8083-25)

It uses the principle of rigidity in space; the rotor turns in a vertical plane, and the compass card is fixed to the rotor. Since the rotor remains rigid in space, the points on the card hold the same position in space relative to the vertical plane. As the instrument case and the airplane revolve around the vertical axis, the card provides clear and accurate heading information.

9. What are the limitations of the heading indicator? (FAA-H-8083-25)

Pitch and bank limits vary with design and make of instrument. On some light airplanes, the limits are approximately 55° of pitch and 55° of bank. When either of these attitude limits is exceeded, the instrument “tumbles” or “spills” giving incorrect indications until reset with the caging knob. Some modern instruments are designed in such a manner that they will not tumble.

10. What error is the heading indicator subject to? (FAA-H-8083-25)

Because of precession, caused chiefly by friction, the heading indicator will creep or drift from a heading to which it is set. The amount of drift depends largely upon the condition of the instrument (worn and dirty bearings and/or improperly lubricated bearings). Three degrees in 15 minutes is normal; significantly greater drift rates may signal impending gyro failure.

11. How does the turn coordinator operate? (FAA-H-8083-15)

The turn part of the instrument uses precession to indicate direction and approximate rate of turn. A gyro reacts by trying to move in reaction to the force applied thus moving the needle or miniature aircraft in proportion to the rate of turn. The slip / skid indicator is a liquid-filled tube with a ball that reacts to centrifugal force and gravity.

12. What information does the turn coordinator provide? (FAA-H-8083-25)

It shows the yaw and roll of the aircraft around the vertical and longitudinal axes. The miniature airplane will indicate direction of the turn as well as rate of turn. When aligned with the turn index, it represents a standard rate of turn of 3° per second. The inclinometer of the turn coordinator indicates the coordination of aileron and rudder. The ball indicates whether the airplane is in coordinated flight or is in a slip or skid.

13. What will the turn indicator indicate when the aircraft is in a skidding or a slipping turn? (FAA-H-8083-25)

Slip – The ball in the tube will be on the inside of the turn; not enough rate of turn for the amount of bank.
Skid – The ball in the tube will be to the outside of the turn; too much rate of turn for the amount of bank.
E. Magnetic Compass

1. How does the magnetic compass work? (FAA-H-8083-25)

Magnetized needles fastened to a float assembly, around which is mounted a compass card, align themselves parallel to the earth’s lines of magnetic force. The float assembly is housed in a bowl filled with acid-free white kerosene.

2. What limitations does the magnetic compass have? (FAA-H-8083-15)

This jewel-and-pivot type mounting allows the float freedom to rotate and tilt up to approximately 18° angle of bank. At steeper bank angles, the compass indications are erratic and unpredictable.

3. What are the various compass errors? (FAA-H-8083-15)

Oscillation error – Erratic movement of the compass card caused by turbulence or rough control technique.

Deviation error – Due to electrical and magnetic disturbances in the aircraft.

Variation error – Angular difference between true and magnetic north; reference isogonic lines of variation.

Dip errors :
a. Acceleration error – On east or west headings, while accelerating the magnetic compass shows a turn to the north, and when decelerating, it shows a turn to the south.
Remember : ANDS

b. Northerly turning error – The compass leads in the south half of a turn, and lags in the north of the turn.
Remember : UNOS

F. Hydraulic System

1. What equipment would be considered hydraulic on this aircraft?

The retractable landing gear
The emergency hand pump
The hydraulically –actuated brake on each main gear
The air/oil nose gear shock strut

3. What provides hydraulic power to the landing gear system?

An electrically-driven hydraulic power pack provides all hydraulic power to the landing gear system. The power pack is located behind the firewall between the pilot’s and copilot’s rubber pedals.

4. Describe hydraulic power pack operation.

Hydraulic power pack operation is controlled by the landing gear lever. When the gear lever is selected in wither the “Up” or “Down” position, a pressure switch will activate the power pack and a selector valve is mechanically rotated. Depending on the position of the landing gear lever (and corresponding valve position), hydraulic pressure will be applied to actuator cylinders, which extend or retract the gear. When the landing gear has reached the desired position and the cycle is complete (a series of electrical switches have closed or opened), an indicator light will illuminate on the panel. In the “Gear Down” cycle only, the hydraulic power pack will continue to operate until system pressure is between 1,000 PSI to 1,500 PSI, at which time the pressure switch turns the power pack off. The hydraulic system normally maintain an operating pressure of 1,000 PSI to 1,500 PSI.

G. Landing Gear

1. Describe the landing gear system on this airplane.

The landing gear consists of a tricycle-type system utilizing two main wheels and a steerable nose wheel. Tubular spring steel main gear struts provide main gear shock absorption, while nose gear shock absorption is provided by a combination air/oil shock strut.

2. How is the landing gear extended and retracted?

A hydraulic actuator powered by an electrically-driven hydraulic power pack enables the landing gear extension, retraction, and main gear down lock release operations to occur. A pressure switch starts and stops power pack operation and hydraulic pressure is directed by a landing gear lever.
3. How is the gear locked in the down position?

Mechanical down locks are incorporated into the nose and main gear assembly.

4. How is the gear locked in the up position?

A positive “up” pressure is maintained on the landing gear by the hydraulic power pack. To accomplish this, the power pack automatically maintains an operating pressure of 1,000 PSI to 1,500 Psi in the landing gear system

5. How is accidental gear retraction prevented on the ground?

Inadvertent gear retraction is prevented by a safety (squat) switch on the nose gear. Whenever the nose gear strut is compressed (weight of the airplane on the ground), this switch electrically prevents operation of the landing gear system.

6. How is the landing gear position indicated in the cockpit?

Amber (gear up) and green (gear down) position indicator lights are provided in the cockpit. They are located adjacent to the landing gear control lever and indicate that the gear is either up or down and locked. Both indicators incorporate a press-to-test feature and also provide dimming shutters for night operation.
Note: If one of the indicator lights should burn out, the design allows for replacement in flight, with the bulb from the other indicator light.

7. What type of landing gear warning system is used?

If the manifold pressure is reduced to less than approximately 12 inches at a low altitude with the master switch on, and the landing gear is not locked down, a switch on the throttle linkage will electrically actuate the gear warning circuit of the dual warning unit. An intermittent tone will be heard on the speaker. Also, if the wing flaps are extended beyond 20° while the landing gear is in the retracted position, an interconnect switch in the wing flap system will cause the horn to sound.

8. What is the normal length of time necessary for landing gear retraction or extension?

5 to 7 seconds for either extension or retraction of the landing gear.

9. Can the landing gear be retracted with the hand-operated pump?

No, retraction of the landing gear cannot be accomplished with the emergency hand pump.

10. Describe the braking system on this aircraft.

Hydraulically-actuated disc-type brakes are utilized on each main gear wheel. A hydraulic line connects each brake to a master cylinder located on each pilot’s rudder pedals. By applying pressure on the top of either the pilot’s or copilot’s set of rudder pedals, the brakes may be applied.

11. How is steering accomplished on the ground? (AC 65-15A)

Light airplanes are generally provided with nose wheel steering capabilities through a simple system of mechanical linkages connected to the rudder pedals. When a rudder pedal is depressed, a spring-loaded bungee (push-pull rod) connected to the pivotal portion of a nose wheel strut will turn the nose wheel.

12. What are the landing gear tire pressures?

Nose Wheel Tire Pressure 40-50 PSI
5.00-5, 6-ply rated tires
Main Wheel Tire Pressure 60-68 PSI
15×6.00-6, 6-ply rated tires

H. Power plant

1. What type of engine does this aircraft have?

The airplane is powered by an engine manufactured by Avco-Lycoming, rated at 180 horsepower at 2,700 rpm. It may be described as follows:

a. Normally aspirated
b. Direct-drive
c. Air-cooled
d. Horizontally opposed
e. Carburetor-equipped
f. Four-cylinder
g. 361-cubic-inch displacement

2. Describe how each of the following engine gauges work.

Oil Temperature – Electrically powered from the aircraft electrical system.
Oil Pressure – A direct-pressure oil line from the engine delivers oil at engine operating pressure to the gauge.
Cylinder Head Temperature – Electrically powered from the aircraft electrical system.
Tachometer – Engine-driven mechanically.
Manifold pressure – Direct reading of induction air manifold pressure in inches of mercury.
Fuel pressure – Indicates fuel pressure to the carburetor.

3. What four stroked must occur in each cylinder of a typical four-stroke engine in order for it to produce full power? (FAA-H-8083-25)

The four strokes are:
Intake – fuel mixture is drawn into cylinder by downward stroke.
Compression – mixture is compressed by upward stroke.
Power – spark ignites mixture forcing piston downward and producing power.
Exhaust – burned gases pushed out of cylinder by upward stroke.

4. What does the carburetor do? (FAA-H-8083-25)

Carburetion may be defined as the process of mixing fuel and air in the correct proportions t form a combustible mixture. The carburetor vaporizes liquid fuel into small particles and then mixes it with air. It measures the airflow and meters fuel accordingly.

5. How does the carburetor heat system work? (FAA-H-8083-25)

A carburetor heat valve, controlled by the pilot, allows unfiltered heat air from a shroud located around an exhaust riser or muffler to be directed to the induction air manifold prior to the carburetor. Carburetor heat should be used anytime suspected or known carburetor icing conditions exist.

6. What is fuel injection? (FAA-H-8083-25)

Fuel injectors have replaced carburetors in some airplanes. In a fuel injection system, the fuel is normally injected into the system either directly into the cylinders or just ahead of the intake valves; whereas in a carbureted system, the fuel enters the airstream at the throttle valve. There are several types of fuel injection systems in use today, and though there are variations in design, the operational methods are generally simple. Most designs incorporate an engine-driven fuel pump, a fuel/control unit, fuel distributor, and discharge nozzle for each cylinder.

7. What are some advantages of fuel injection? (FAA-H-8083-25)

a. Reduction in evaporative icing
b. Better fuel flow
c. Faster throttle response
d. Precise control of mixture
e. Better fuel distribution
f. Easier cold weather starts

8. Are there any disadvantages associated with fuel-injected engines? (FAA-H-8083-25)

a. Difficulty in starting a hot engine
b. Vapor locks during ground operations on hot days.
c. Problems associated with restarting an engine that quits because of fuel starvation

9. What is the condition known as vapor lock? (AC 65-12A)

Fuel-injected engines are more susceptible to vapor lock during ground operations on hot days. Vapor lock occurs when fuel vapor and/or air collect in different sections of the fuel system. The fuel may actually boil in the lines, creating a condition which interferes with the normal operation of valves, pumps, etc. Other causes of vapor lock can be low fuel pressure and excessive fuel turbulence.

10. What does the throttle do? (FAA-H-8083-25)

The throttle allows the pilot to manually control the amount of fuel/air charge entering the cylinders. This in turn regulates the engine manifold pressure.

11. What does the mixture control do? (FAA-H-8083-25)

It regulates the fuel-to-air ratio. Most airplane engines incorporate a device called a mixture control, by which the fuel/air ratio can be controlled by the pilot during flight. The purpose of a mixture control is to prevent the mixture from becoming too rich at high altitudes, due to decreasing air density. Leaning the mixture during cross-country flights conserves fuel and provides optimum power.

12. What are turbochargers? (FAA-H-8083-25)

Higher performance aircraft typically operate at higher altitudes where air density is substantially less. The decrease in air density as altitude increases results in a decreased power output of an un-supercharged engine. By compressing the thin air by means of a power as altitude is increased. The turbocharger consists of a compressor to provide pressurized air to the engine, and a turbine driven by exhaust gases of the engine to drive the compressor.

13. What are cowl flaps? (AC 65-12A)

Cowl flaps are located on the engine cowling and allow the pilot to control the operating temperature of the engine b regulating the amount of air circulating within the engine compartment. Cowl flaps may be manually or electrically activated and usually allow for a variety of flap positions.

14. When are cool flaps utilized? (AC 65-12A)

a. Normally the cowl flaps will be in “open” position in the following operations:
• During starting of the engine
• While taxiing
• During takeoff and high-power climb operation
The cowl flaps may be adjusted in cruise flight for the appropriate cylinder head temperature.

b. The cowl flaps should be in the “closed” position in the following operations:
• During extended let-down
• Anytime excessive cooling is a possibility (i.e., approach to landing, engine-out practice, etc.)

15. Define the term “service ceiling”. (FAA-H-8083-25)

Service Ceiling – Defined as the height above sea level beyond which the aircraft’s maximum rate of climb would be no more than 100 feet per minute. The service ceiling may be found in the Pilot’s Operating Handbook for that aircraft.

I. Propeller

1. What type of propeller does this aircraft have?

The airplane propeller may be described as
a. All-metal,
b. Two-bladed,
c. Constant-speed, and
d. Governor-regulated

2. Discuss fixed-pitch propellers. (FAA-H-8083-25)

The pitch of this propeller is fixed by the manufacturer and cannot be changed by the pilot. Two types of fixed-pitch propellers are:
Climb propeller – has a lower pitch, therefore less drag. Results in higher RPM and more horsepower being developed by the engine; increases performance during takeoffs and climbs, but decreases performance during cruising flight.
Cruise propeller – has a higher pitch, therefore more drag. Result in lower RPM and less horsepower capability; decreases performance during takeoffs and climbs, but increases efficiently during cruising flight.

3. Discuss variable-pitch propellers (constant speed). (FAA-H-8083-25)

An airplane equipped with a constant-speed propeller is capable of continuously adjusting the propeller blade angle to maintain a constant engine speed. For example, if engine rpm increases as a result of a decreased load on the engine (descent), the system automatically increases the propeller blade angle (increasing air load) until the rpm has returned to the preset speed. The propeller governor can be regulated by the pilot with control in the cockpit, so that any desired blade angle setting (within its limits) and engine operating rpm can be obtained, thereby increasing the airplane’s efficiently in various flight conditions

4. What does the propeller control do? (FAA-H-8083-25)

The propeller control regulates propeller pitch and engine rpm as desired for a given flight condition. The propeller control adjusts a propeller governor which established and maintains the propeller speed, which in turn maintains the engine speed.

5. What would the desired propeller setting be for maximum performance situations such as takeoff? (FAA-H-8083-25)

A low pitch, high rpm setting produces maximum power and thrust. The low blade angle keeps the angle of attack small and efficient with respect to the relative wind. At the same time, it allows the propeller to handle a smaller mass of air per revolution. This light load allows the engine to turn at high rpm and to convert the maximum amount to fuel into heat energy in a given time. The high rpm also creases maximum thrust because the mass of air handled per revolution is small, the number of revolutions per minute is many, the slipstream velocity is high, and the airplane speed is low.

6. What is a propeller governor? (AC 65-12A)

The propeller governor, with the assistance of a governor pump, controls the flow of engine oil to or from a piston in the propeller hub. When the engine oil, under high pressure from the governor pump, pushes the piston forward, the propeller blades are twisted toward a high pitch/low rpm condition. When the engine oil is released from the cylinder, centrifugal force, with the assistance of an internal spring, twists the blades towards a low pitch / high rpm condition.

7. When operating an airplane with a constant-speed propeller, which condition induces the most stress on the engine? (FAA-H-8083-3)

Excessive manifold pressure raises the cylinder compression pressure, resulting in high stresses within the engine. Excessive pressure also produces high engine temperatures. A combination of high manifold pressure and low rpm can induce damaging detonation; however, it is a fallacy that (in non-turbocharged engines) the manifold pressure in inches of mercury (inches Hg) should never exceed rpm in hundreds for cruise power settings. The cruise power charts in the AFM/POH should be consulted when selecting cruise power settings. Whatever the combinations of rpm and manifold pressure listed in these charts – they have been flight tested and approved by the airframe and power plant engineers for the respective airframe and engine manufacturer.

J. Fuel System

1. What type fuel system does this aircraft have?

The fuel system consists of the following:
a. Two vented integral fuel tanks
b. A four-position fuel selector valve
c. A fuel strainer
d. A manual primer
e. An engine-driven fuel pump
f. An electric auxiliary fuel pump
g. A carburetor
The airplane utilizes a gravity-feed type fuel system. Fuel is delivered to the engine-driven fuel pump, unassisted, except by gravity. Fuel flows from the wing tanks to the fuel selector valve which is marked with BOTH, RIGHT, LEFT and OFF positions. From the fuel valve, fuel flows through a fuel strainer and then to the engine-driven fuel pump. The fuel pump then delivers fuel to the carburetor. After the carburetor, the fuel/air mixture is delivered to the cylinders via intake manifold tubes.
2. When is the auxiliary fuel boost pump used?

Proper usage of the fuel boost pump varies with different aircraft. In general, the fuel boost pump should be used during takeoffs and landings, when switching fuel tanks, and anytime fuel pressure falls below a selected value. The fuel boost pump in a Cessna 172-RG should be utilized anytime the fuel pressure fails below 0.5 PSI.

3. Why is it necessary to include a left and right position on the fuel selector valve?

During cruise flight, with the fuel selector valve on “Both”, unequal fuel flow may occur if the wings are not consistently kept level during the flight. This will result in one wing being heavier than the other. A fuel selector valve with the left/right option allows a pilot to control the situation by selecting the tank on the heavier wing and remaining on that tank until both tanks contain approximately the same amount of fuel.

4. Where are the fuel vents located for each tank?

The left fuel tank is vented overboard through a vent line with a check valve. The right fuel tank is vented through the filler cap. Both fuel tanks are vented together by an interconnecting line.

5. What purpose do fuel tank vents have? (FAA-H-8083-25)

As the fuel level in an aircraft fuel tank decreases, without vents a vacuum would be created within the tank which would eventually result in a decreasing fuel flow and finally engine stoppage. Fuel system venting provides a way of replacing fuel with outside air, preventing formation of a vacuum.

6. What type fuel does this aircraft require (minimum octane rating and color?

The approved fuel grade used is 100LL, and the color is blue.

7. Can other types of fuel be used if the specified grade is not available? (FAA-H-8083-25)

Airplane engines are designed to operate using a specific grade of fuel as recommended by the manufacturer. If the proper grade of fuel is not available, it is possible, but not desirable, to use the next higher grade as a substitute. If using a higher grade fuel than that specified as a minimum grade for your engine, the engine manufacturer’s instructions must be observed. This is because the higher octane fuels normally used in higher-compression engines must ignite at higher temperatures – but not prematurely.

8. What are some examples of different fuel grades (octane ratings) available? (FAA-H-8083-25)

Grade Color
80 Red
100 Green
100LL Blue
Turbine Colorless
Note: It is important tom remember that if fuel grades are mixed together they will become clear or colorless.

9. What is the function of the manual primer, and how does it operate?

The manual primer’s function is to provide assistance in starting the engine. The primer draws fuel from the fuel strainer and injects it directly into the cylinder intake ports. This usually results in a quicker, more efficient engine start.

10. Where are the drain valves located?

A drain valve is located on the bottom f each main wing and also directly under the fuel selector valve. A fuel strainer drain is located under an access panel on the right side of the engine cowling.

11. How is fuel quantity measured?

One float-type fuel quantity transmitter and one electric fuel quantity indicator measure fuel quantity for each tank.

12. Are the fuel quantity indicators accurate? (FAA-H-8083-25)

Aircraft certification rules only require accuracy in fuel gauges when they read “empty”. Any reading other than “empty” should be verified. Do not depend solely on the accuracy of the fuel quantity gauges. Always visually check the fuel level in each tank during the preflight inspection, and then compare it with the corresponding fuel quantity indication.

K. Oil System

1. Briefly describe the engine oil system.

Aircraft engine lubrication and oil for propeller governor operation is supplied from a sump on the bottom of the engine. Oil sump capacity is 8 quarts.

2. What are the minimum and maximum oil capacities?

The minimum oil capacity is 5 quarts of oil. The maximum oil capacity is 8 quarts.

3. What are the minimum and maximum oil temperature and pressures?

Oil Temperature – 100°F to 245°F
Oil Pressure – 25 PSI (minimum for idling), 60 – 90 PSI (green arc), 115 PSI (red line)

4. What are the two types of oil available for use in your airplane?

Mineral Oil – Also known as non-detergent oil; contains no additives. This type of oil is normally used after an engine overhaul or when an aircraft engine is new; normally used for engine break-in purposes.
Ash less Dispersant – Mineral oil with additives; high anti wear properties along with multi-viscosity (ability to perform in wide range of temps). Also picks up contamination and carbon particles

5. What types of oil is recommended for this engine (for summer and winter operations)?

Ash less dispersant oil, usually SAE 20W-50 during the colder months. For temperatures above 60°F (summer), use SAE 40 or SAE 50.

L. Electrical System

1. Describe the electrical system on this aircraft.

Electrical energy is provided by a 28-volt, direct-current system, powered by an engine-driven 60-amp alternator and a 24-volt battery.

2. Where is the battery located?

The battery is located aft of the rear cabin wall.

3. How are the circuits for the various electrical accessories within the aircraft protected? (FAA-H-8083-25)

Most of the electrical circuits in an airplane are protected from an overload condition by either circuit breakers or fuses or both. Circuit breakers perform the same function as fuses except that when an overload occurs, a circuit breaker can be reset.

4. What is a bus bar? (FAA-H-8083-25)

A bus bar interfaces the electrical system with the various electrical accessories such as radios, lights, etc. A bus bar makes aircraft electrical wiring considerably less complex. Fuses or circuit breakers are incorporated into the bus bar providing protection for the different aircraft electrical circuits from possible damage as a result of faulty generators, alternators or components.

5. The electrical system provides power for what equipment in an airplane?

Normally the following:
a. Radio equipment h. Interior lights
b. Turn coordinator i. Instrument lights
c. Fuel gauges j. Position lights
d. Pitot heat k. Flaps (maybe)
e. Landing light l. Stall warning system (maybe)
f. Taxi light m. Oil temperature gauge
g. Strobe lights n. Cigarette lighter (maybe)

6. What does the ammeter indicate? (FAA-H-8083-25)

It shows if the alternator / generator is producing an adequate supply of electrical power to the system by measuring the amperes of electricity, and also indicates whether the battery is receiving an electrical charge. If the needle indicates a plus value, it means that the battery is being charged. If the needle indicates a minus value, it means that the generator or alternator output is inadequate and energy is being drawn from the battery to supply the system.

7. What function does the voltage regulator have? (FAA-H-8083-25)

A voltage regulator controls the rate of charge to the battery by stabilizing the generator or alternator electrical output. The generator / alternator voltage output is usually slightly higher than the battery voltage. For example, a 12-volt battery would be fed by a generator / alternator system of approximately 14 volts. The difference n voltage keeps the battery charged.

8. Does the aircraft have an external power source receptacle, and if so where is it located?

Yes, the receptacle is located behind a door on the left side of the fuel age aft of the baggage compartment door.

9. What type of ignition system does your airplane have? (FAA-H-8083-25)

Engine ignition is provided by two engine-driven magnetos, and two spark plugs per cylinder. The ignition system is completely independent of the aircraft electrical system. The magnetos are independent of the aircraft electrical system. The magnetos are self-contained units supplying electrical current without using an external source of power. However, before they can produce current, the magnetos must be actuated as the engine crankshaft is rotated by some other means. To accomplish this, the aircraft battery furnishes electrical power to operate a starter which, through a series of gears, rotates the engine crankshaft. This in turn actuates the armature of the magneto to produce the sparks for ignition of the fuel in each cylinder. After the engine starts, the starter system is disengaged and the battery no longer contributes to the actual operation of the engine.

10. What are the two main advantages of a dual ignition system? (FAA-H-8083-25)

a. Increases safety – in case one system fails the engine may be operated on the other until a landing is safely made.
b. More complete and even combustion of the mixture, and consequently improved engine performance, i.e., the fuel / air mixture will be ignited on each side of the combustion chamber and burn toward the center.

M. Environmental System

1. How does the aircraft cabin heat work?

Fresh air, heated by an exhaust shroud, is directed to the cabin through a series of ducts.

2. How does the pilot control temperature in the cabin?

Temperature is controlled by mixing outside air (cabin air control) with heated air (cabin heat control) in a manifold near the cabin firewall. This air is then ducted to vents located on the cabin floor.

3. What are several types of oxygen systems in use? (FAA-H-8083-25)

Diluter-demand, pressure-demand, and continuous-flow.

4. Can any kind of oxygen be used for aviator’s breathing oxygen? (FAA-H-8083-25)

No, oxygen used for medical purposes or welding normally should not be used because it may contain too much water. The excess water could condense and freeze in the oxygen lines when flying at high altitudes. Specifications for “aviator’s breathing oxygen” are 99.5% pure oxygen with not more than two milliliters of water per liter of oxygen.

5. How does a continuous-flow oxygen system operate? (FAA-H-8083-25)

Continuous flow oxygen systems are usually provided for passengers. The passenger mask typically has a reservoir bag that collects oxygen from the continuous flow oxygen system during the time when the mask user is exhaling. The oxygen collected in the bag allows a higher inspiratory flow rate during the inhalation cycle, which reduces the amount of air dilution. Ambient air is added to the supplied oxygen during inhalation after the reservoir bad oxygen supply is depleted. The exhaled air is released to the cabin.

6. How does a pressure demand oxygen system operate? (FAA-H-8083-25)

Pressure demand oxygen systems are similar to diluter demand oxygen equipment, except that oxygen is supplied to the mask under pressure at cabin altitudes above 34,000 feet. Pressure demand regulators create airtight and oxygen-tight seals, but they also provide a positive pressure application of oxygen to the mask face piece that allows the user’s lungs to the pressurized with oxygen; this makes them safe at altitudes above 40,000 feet. Some systems may have a pressure demand mask with the regulator attached directly to the mask, rather than mounted on the instrument panel or other area within the flight check.

7. What is a “pressurized” aircraft? (FAA-H-8083-25)

In a “pressurized” aircraft, the cabin, flight compartment, and baggage compartments are incorporated into a sealed unit which is capable of containing air under a pressure higher than outside atmospheric pressure. Pressurized air is pumped into this sealed fuselage by cabin supercharges which deliver a relatively constant volume of air at all altitudes up to a designed maximum. Air is released from the fuselage by a device called an outflow valve. Since the supercharges provide a constant inflow of air to the pressurized area, the outflow valve, by regulating the air exit, is the major controlling element in the pressurization system.

8. What operational advantages are there in flying pressurized aircraft? (FAA-H-8083-25)

A cabin pressurization system performs several functions:
a. It allows an aircraft to fly higher which can result in better fuel economy, higher speeds, and the capability to avoid bad weather and turbulence.
b. It will typically maintain a cabin pressure altitude of 8,000 feet at the maximum designed cruising altitude of the airplane.
c. It prevents rapid changes of cabin altitude which may be uncomfortable or injurious to passengers and crew.
d. It permits a reasonably fast exchange of air from inside to outside of the cabin. This is necessary to eliminate odors and to remove stale air.

9. Describe a typical cabin pressure control system. (FAA-H-8083-25)

The cabin pressure control system provides cabin pressure regulation, pressure relief, and the means for selecting the desired cabin altitude in the isobaric and differential range. In addition, dumping of the cabin pressure regulator, an outflow valve, and a safety valve are used to accomplish these functions.

10. What are the components of a cabin pressure control system? (FAA-H-8083-25)

a. Cabin pressure regulator – Controls cabin pressure to a selected value in the isobaric range and limits cabin pressure to a preset differential value in the differential range.
b. Cabin air pressure safety valve – A combination pressure relief, vacuum relief, and dump valve.
• Pressure relief valve: prevents cabin pressure from exceeding a predetermined differential pressure above ambient pressure.
• Vacuum relief valve: prevents ambient pressure from exceeding cabin pressure by allowing external air to enter the cabin when the ambient pressure exceeds cabin pressure.
• Dump valve: actuated by a cockpit control which will cause the cabin air to be dumped to the atmosphere.
c. Instrumentation – Several instruments used in conjunction with the pressurization controller are:
• Cabin differential pressure gauge – Indicates difference between inside and outside pressure; should be monitored to ensure that the cabin does not exceed maximum allowable differential pressure.
• Cabin altimeter – This is a check on system performance.
Sometimes differential pressure and cabin altimeter combined into one:
• Cabin rate-of-climb – Indicates cabin rate –of-climb or descent.

N. Deicing and Anti-icing

1. What is the difference between a deice system and an anti-ice system? (AC 65-15A)

A deice system is used to eliminate ice that has already formed. An anti-ice system is used to prevent the formation of ice.

2. What types of systems are utilized on the prevention and elimination of airframe ice? (AC 65-15A)

Pneumatic – A deice type of system; consists of inflatable boots attached to the leading edges of the wings and tail surfaces. Compressed air from the pressure side of the engine vacuum pump is cycled through ducts or tubes in the boots causing the boots to inflate. Most systems also incorporate a timer.
Hot Air – An anti-ice type system; commonly found on turboprop and turbojet aircraft. Hot air is directed from the engine (compressor) to the leading edges of the wings.

3. What are the types of systems are utilized in the prevention and elimination of propeller ice? (AC 65-15A)

Electrically heated boots – Consists of heating elements incorporated into the boots which are bounded to the propeller. The ice buildup on the propeller is heated from below and then throws off by centrifugal force.
Fluid system – Consists of an electrically driven pump which, when activated, supplies a fluid, such as alcohol, to a device in the propeller spinner which distributes the fluid along the propeller assisted by centrifugal force.

4. What types of systems are utilized in the prevention and eliminate=ion of windshield ice? (AC 65-15A)

Fluid system – Consists of an electrically-driven pump which may be activated to spray a fluid, such as alcohol, onto the windshield to prevent the formation of ice.
Electrical system – Heating elements are embedded in the windshield or in a device attached to the windshield which when activated, prevents the formation of ice.

O. Avionics

1. What function does the avionics power switch have?

The avionics power switch controls power from the primary bus to the avionics bus. The circuit is protected by a combination power switch / circuit breaker. Aircraft avionics are isolated from electrical power when the switch is in the “Off” position. Also, if an overload should occur in the system, the avionics power switch will move to the “Off” position, causing an interruption of power to all aircraft avionics.

2. What are static discharges? (AC 65-15A)

Static discharges are installed on aircraft to reduce radio receiver interference caused by corona discharge, which Is emitted from the aircraft as a result of precipitation static. Static discharges, normally mounted on trailing edges of the control surfaces, wing tips, and vertical stabilizer, discharge the precipitation static at points a critical length away from the wing and tail extremities where there is little or no coupling of the static into the radio antenna.

3. Within what frequency band does the following type of navigational and communication equipment installed on board most aircraft operate? (AIM)

VOR receiver (VHF band) 108.0 to 117.95 MHz
Communication transceivers (VHF band) 118.0 to 135 MHz
DME receiver (UHF band) 960 MHz to 1215 MHz
ADF receiver (LF to MF band) 190 to 530 kHz
Note: Know the location and function of the various antennas on your aircraft!