Elements of Aeronautics

Trim tabs are small, movable portions of the trailing edge of the control surface.. Like the other primary control surfaces, the rudder is a movable surface hinged to a fixed surface, in

Department of Aeronautical Engineering

Subject Name : Elements of Aeronautics

Subject Code : 07A306

Semester : Third semester

Prepared By : U Selvakumar, Lecturer, Dept of Aero, BIT, Sathy

Components of an Airplane and their Functions

An airplane contains the following important component sections,

1 Fuselage:

Fuselage is the main body of an airplane which contains cabin /cockpit which provides space for crew members and flight controls for aircraft Fuselage also provides space for passengers and payloads It gives attachment points for some other aircraft components like wing There are three kinds of fuselage structure They are ,

 Truss structure

 Monocoque structure

 Semi – monocoque structure

Truss:

Truss – A fuselage design made up of supporting members longerons, diagonal members and

vertical members that resist deformation by applied loads

Monocoque structure:

Monocoque – A shell-like fuselage design in which most of the imposed

stresses are taken by the outside stressed skin Here bulkheads and formers are used to give the shape to the fuselage Stringers are not used

Semi – monocoque structure:

Semi – monocoque structure – A fuselage design which contains a

substructure of bulkheads and/or formers, along with stringers, that support flight loads and stresses imposed on fuselage

2 Wings:

The wings are lifting devices in which series of airfoils attached It is placed in each side

of the fuselage and are the main lifting surfaces that support the airplane in flight The cross section of the wing is called as airfoil An airfoil is a shape designed to produce lift Besides the wing, propellers and the tail surfaces are also airfoils

An airfoil has a leading edge and a trailing edge A chord and a camber also characterize an

airfoil The chord is an imaginary straight line connecting the leading edge with the trailing edge The

chord is used for determining the geometric angle of attack and for determining the area of a wing The

mean camber line is the line an equal distance from the upper and lower surfaces of the wing The camber is the curvature of the mean camber line

A wing that has an airfoil with a great deal of curvature in its mean camber line is said to

be a highly cambered wing A symmetric airfoil has no camber An airfoil with lift also has an angle of attack The relative wind is the direction of the wind at some distance from the wing It is parallel to

and opposite to the direction of motion of the wing The velocity of the relative wind is equal to the

speed of the wing The geometric angle of attack is defined as the angle between the mean chord of the

airfoil and the direction of the relative wind

There are numerous wing designs, sizes, and shapes used by the various

manufacturers Each fulfills a certain need with respect to the expected performance for the particular airplane Wings may be attached at the top, middle, or lower portion of the fuselage These designs are

referred to as high-, mid-, and low-wing, respectively The number of wings can also vary Airplanes with a single set of wings are referred to as monoplanes, while those with two sets are called biplanes

Many high-wing airplanes have external braces, or wing struts, which transmit the flight and landing loads through the struts to the main fuselage structure Since the wing struts are usually

attached approximately halfway out on the wing, this type of wing structure is called semi-cantilever A few high-wing and most low-wing airplanes have a full cantilever wing designed to carry the loads

without external struts The principal structural parts of the wing are spars, ribs, and stringers trusses, I-beams, tubing, or other devices, including the skin

The wing ribs determine the shape and thickness of the wing (airfoil) Wing flaps are the trailing edge control devices attached to the trailing edge of the inboard wing They may be fixed or retractable When deflected downward they will increase lift by increasing the camber during takeoffs and

landings Slats are the leading edge devices which are used to delay flow seperation Slot is the space between the slat and leading edge It is used to increases the drag

In most modern airplanes, the fuel tanks either are an integral part of the wing’s structure, Ailerons extend from about the midpoint of each wing outward toward the tip and move in opposite directions to create aerodynamic forces that cause the airplane to roll Flaps extend outward from the fuselage to near the midpoint of each wing

3 Empennage:

The correct name for the tail section of an airplane is empennage The empennage includes the entire tail group, consisting of fixed surfaces such as the vertical stabilizer and the

horizontal stabilizer The movable surfaces include the rudder, the elevator, and one or more trim tabs

A second type of empennage design does not require an elevator Instead, it incorporates a one-piece horizontal stabilizer that pivots from a central hinge point This type of design is called a stabilator, and

is moved using the control wheel, just as you would the elevator For example, when you pull back on the control wheel, the stabilator pivots so the trailing edge moves up This increases the aerodynamic tail load and causes the nose of the airplane to move up Stabilators have an antiservo tab extending across their trailing edge

The antiservo tab moves in the same direction as the trailing edge of the stabilator The antiservo tab also functions as a trim tab to relieve control pressures and helps maintain the stabilator in the desired position The rudder is attached to the back of the vertical stabilizer During flight, it is used

to move the airplane’s nose left and right The rudder is used in combination with the ailerons for turns during flight The elevator, which is attached to the back of the horizontal stabilizer, is used to move the nose of the airplane up and down during flight Trim tabs are small, movable portions of the trailing edge of the control surface These movable trim tabs, which are controlled from the cockpit, reduce control pressures Trim tabs may be installed on the ailerons, the rudder, and/or the elevator

Landing gear employing a rear mounted wheel is called conventional landing gear

Airplanes with conventional landing gear are sometimes referred to as tail wheel airplanes When the

third wheel is located on the nose, it is called a nose wheel, and the design is referred to as a tricycle

gear A steerable nose wheel or tail wheel permits the airplane to be controlled throughout all

operations while on the ground

5 Propulsion system:

The powerplant usually includes both the engine and the propeller or simply the engine (Turbojet, ramjet and scramjet) The primary function of the engine is to provide the power to turn the propeller It also generates electrical power, provides a vacuum source for some flight

instruments, and in most single-engine airplanes, provides a source of heat for the pilot and

passengers The engine is covered by a cowling, or in the case of some airplanes, surrounded by a nacelle The purpose of the cowling or nacelle is to streamline the flow of air around the engine and to help cool the engine by ducting air around the cylinders The propeller, mounted on the front of the engine, translates the rotating force of the engine into a forward - acting force called thrust that helps move the airplane through the air

Conventional Flight Control

Aircraft flight control systems are classified as primary and secondary The primary control systems consist of those that are required to safely control an airplane during flight These include the ailerons, elevator (or stabilator), and rudder Secondary control systems improve the

performance characteristics of the airplane, or relieve the pilot of excessive control forces Examples of secondary control systems are wing flaps and trim systems The axis system has been given below

An airplane moves in three dimensions called roll, pitch, and yaw Roll is rotation about the longitudinal axis that goes down the center of the fuselage The ailerons control rotation about the roll axis Pitch is rotation about the lateral axis of rotation, which is an axis parallel to the long dimension of the wings The elevators control the pitch of the airplane By controlling the pitch of the airplane, the elevators also control the angle of attack of the wing To increase the angle of attack, the entire airplane is rotated up As we will see, this control or the angle of attack is key in the

adjustment of the lift of the wings

Finally, yaw, which is controlled by the rudder, is rotation about the vertical axis, which is a line that goes vertically through the center of the wing It is important to note that all three axes go through the center of gravity (often abbreviated c.g.) of the airplane The center of gravity is the balance point of the airplane Or, equivalently, all of the weight of the airplane can be considered to

be at that one point

Primary Control Surfaces:

The elevator controls pitch about the lateral axis Like the ailerons on small airplanes, the elevator is connected to the control column in the cockpit by a series of mechanical linkages Aft movement of the control column deflects the trailing edge of the elevator surface up This is usually referred to as up elevator Moving the control column forward has the opposite effect In this case, elevator camber increases, creating more lift (less tail-down force) on the horizontal stabilizer/elevator This moves the tail upward and pitches the nose down

Rudder:

The Rudder controls movement of the airplane about its vertical axis This motion is called yaw Like the other primary control surfaces, the rudder is a movable surface hinged to a fixed surface, in this case, to the vertical stabilizer, or fin Moving the left or right rudder pedal controls the rudder.When the rudder is deflected into the airflow, a horizontal force is exerted in the opposite direction.Secondary control surfaces:

Flaps:

Flaps are the most common high-lift devices used on practically all airplanes These

surfaces, which are attached to the trailing edge of the wing, increase both lift and induced drag for any given angle of attack Flaps allow a compromise between high cruising speed and low landing speed, because they may be extended when needed, and retracted into the wing’s structure when not needed Leading edge flaps, like trailing edge flaps, are used to increase both Cl and the camber of the wings There are four common types of flaps: plain, split, slotted, and Fowler flaps

Slats and Slots:

High-lift devices also can be applied to the leading edge of the airfoil The most

common types are fixed slots, movable slats, and leading edge flaps Fixed slots direct airflow to the upper wing surface and delay airflow separation at higher angles of attack Movable slats consist of

leading edge segments, which move on tracks Opening a slat allows the air below the wing

to flow over the wing’s upper surface, delaying airflow separation

Spoilers:

On some airplanes, high-drag devices called spoilers are deployed from the wings to spoil the smooth airflow, reducing lift and increasing drag Spoilers are used for roll control on some aircraft, one of the advantages being the elimination of adverse yaw

Trim Tabs:

The most common installation on small airplanes is a single trim tab attached to the trailing edge of the elevator Most trim tabs are manually operated by a small, vertically mounted control wheel However, a trim crank may be found in some airplanes The cockpit control includes a tab position indicator

Anti servo Tabs:

In addition to decreasing the sensitivity of the stabilator, an antiservo tab also functions as a trim device to relieve control pressure and maintain the stabilator in the desired position The fixed end

of the linkage is on the opposite side of the surface from the horn on the tab, and when the trailing edge

of the stabilator moves up, the linkage forces the trailing edge of the tab up When the stabilator moves down, the tab also moves down This is different than trim tabs on elevators, which move opposite of the control surface

Balance Tabs:

The control forces may be excessively high in some airplanes, and in order to decrease them, the manufacturer may use balance tabs They look like trim tabs and are hinged in approximately the same places as trim tabs The essential difference between the two is that the balancing tab is coupled to the control surface rod so that when the primary control surface is moved in any direction, the tab automatically moves in the opposite direction

Ground Adjustable Tabs:

Many small airplanes have a non-moveable metal trim tab on the rudder This tab is bent in one direction or the other while on the ground to apply a trim force to the rudder it is motor driven The trimming effect and cockpit indications for an adjustable stabilizer are similar to those of a trim tab

End of Lecture

Pitot Static Flight Instruments

There are two major parts of the pitot-static system: the impact pressure chamber and lines, and the static pressure chamber and lines They provide the source ofambient air pressure for the operation of the altimeter, vertical speed indicator (vertical velocity

indicator), and the airspeed indicator

Impact Pressure Chambers and Lines:

In this system, the impact air pressure (air striking the airplane because of its forward motion) is taken from a pitot tube, which is mounted in locations that provide minimum disturbance or turbulence caused by the motion of the airplane through the air The static pressure (pressure of the still air) is usually taken from the static line attached to a vent or vents mounted flushwith the side of the fuselage This compensates for any possible variation in static pressure due to erratic changes in airplane attitude

The openings of both the pitot tube and the static vent must be checked during the preflight inspection to assure that they are free from obstructions Blocked or partially blocked openings should be cleaned by a certificated mechanic Blowing into these openings is not

recommended because this could damage the instruments

As the airplane moves through the air, the impact pressure on the open pitot tube affects the pressure in the pitot chamber Any change of pressure in the pitot chamber is

transmitted through a line connected to the airspeed indicator, which utilizes impact pressure for

its operation

Static Pressure chamber and Lines:

The static chamber is vented through small holes to the free undisturbed air, and as the atmospheric pressure increases or decreases, the pressure in the static chamber changes accordingly Again, this pressure change is transmitted through lines to the instruments which utilize static pressure

An alternate source for static pressure is provided in some airplanes in the event the static ports become blocked This source usually is vented to the pressure inside the cockpit Because of the venturi effect of the flow of air over the cockpit, this alternate static pressure is usually lower than the pressure provided by the normal static air source When the alternate static source is used, the following differences in the instrument indications usually occur: the altimeter will indicate higher than the actual altitude, the airspeed will indicate greater than the actual airspeed, and the

vertical speed will indicate a climb while in level flight Consult the Airplane Flight Manual or Pilot’sOperating Handbook (AFM/POH) to determine the amount of error

If the airplane is not equipped with an alternate static source, breaking the glass seal of the vertical speed indicator allows ambient air pressure to enter the static system This makes the VSI unusable

Below 10,000 feet, a striped segment is visible Above this altitude, a mask begins to cover it, and above 15,000 feet, all of the stripes are covered Another configuration of the altimeter is the drum-type These instruments have only one pointer that makes one revolution for every 1,000 feet Each number represents 100 feet and each mark represents 20 feet A drum, marked in thousands of feet, is geared to the mechanism that drives the pointer To read this type of altimeter, first look at the drum to get the thousands of feet, and then at the pointer to get the feet and hundreds of feet

A sensitive altimeter is one with an adjustable barometric scale allowing the pilot to set the reference pressure from which the altitude is measured This scale is visible in a small window called the Kollsman window A knob on the instrument adjusts the scale The range of the scale is from 28.00" to 31.00" inches of mercury (Hg), or 948 to 1,050 millibars

Rotating the knob changes both the barometric scale and the altimeter pointers in such a way that a change in the barometric scale of 1" Hg changes the pointer indication by 1,000 feet This is the standard pressure lapse rate below 5,000 feet When the barometric scale is adjusted to 29.92" Hg

or 1,013.2 millibars, the pointers indicate the pressure altitude The pilot displays indicate altitude by adjusting the barometric scale to the local altimeter setting The altimeter then indicates the height above the existing sea level pressure

Altimeter Errors:

A sensitive altimeter is designed to indicate standard changes from standard conditions, but most flying involves errors caused by nonstandard conditions and the pilot must be able to modify the indications to correct for these errors There are two types of errors: mechanical and inherent

2 Airspeed Indicator:

An ASI is a differential pressure gauge that measures the dynamic pressure of the air through which the aircraft is flying Dynamic pressure is the difference in the ambient static air pressure and the total, or ram, pressure caused by the motion of the aircraft through the air These two pressuresare taken from the pitot-static system

The mechanism of the ASI consists of a thin, corrugated phosphor bronze aneroid, or diaphragm, that receives its pressure from the pitot tube The instrument case is sealed and connected to the static ports As the pitot pressure increases or the static pressure decreases, the diaphragm expands

This dimensional change is measured by a rocking shaft and a set of gears that drives a pointer across

the instrument dial Most ASIs are calibrated in knots, or nautical miles per hour; some instruments show statute miles per hour, and some instruments show both Types of Airspeed:Just as there are several types of altitude, there are multiple types of airspeed: Indicated Airspeed (IAS), Calibrated Airspeed (CAS), Equivalent Airspeed (EAS), and True Airspeed (TAS)

Indicated Airspeed (IAS):

IAS is shown on the dial of the instrument, uncorrected for instrument or system errors

Calibrated Airspeed (CAS):

CAS is the speed at which the aircraft is moving through the air, which is found by correcting IAS for instrument and position errors The POH/AFM has a chart or graph to correct IAS for these errors and provide the correct CAS for the various flap and landing gear configurations

Equivalent Airspeed (EAS):

EAS is CAS corrected for compression of the air inside the pitot tube EAS is the same as CAS in standard atmosphere at sea level As the airspeed and pressure altitude increase,

the CAS becomes higher than it should be, and a correction for compression must be subtracted from the CAS

True Airspeed (TAS):

TAS is CAS corrected for nonstandard pressure and temperature TAS and CAS are

the same in standard atmosphere at sea level Under nonstandard conditions, TAS is found by applying

a correction for pressure altitude and temperature to the CAS

3 Vertical Speed Indicator:

The VSI is also called a vertical velocity indicator (VVI), and was formerly known as a rate-of-climb indicator It is a rate-of-pressure change instrument that gives an indication of any

deviation from a constant pressure level

Inside the instrument case is an aneroid very much like the one in an ASI 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 The pressure inside the case compresses the aneroid, moving the pointer upward, showing a climb and indicating the rate of ascent in number of feet per minute (fpm)

When the aircraft levels off, the pressure no longer changes The pressure inside the case becomes equal to that inside the aneroid, and the pointer returns to its horizontal, or zero, position When the aircraft descends, the static pressure increases The aneroid expands, moving the pointer downward, indicating a descent

The pointer indication in a VSI lags a few seconds behind the actual change in

pressure However, it is more sensitive than an altimeter and is useful in alerting the pilot of an upward

or downward trend, thereby helping maintain a constant altitude Some of the more complex VSIs, called instantaneous vertical speed indicators (IVSI), have two accelerometer-actuated air pumps that sense an upward or downward pitch of the aircraft and instantaneously create a pressure differential By the timethe pressure caused by the pitch acceleration dissipates, the altitude pressure change is

effective

Gyroscopic Instruments

Principle:

Any spinning object exhibits gyroscopic properties A wheel or rotor designed and mounted

to utilize these properties is called a gyroscope Two important design characteristics of an instrument gyro are great weight for its size, or high density, and rotation at high speed with low friction bearings There are two general types of mountings; the type used depends upon which property of the gyro is utilized A freely or universally mounted gyroscope is free to rotate in any direction about its center of gravity Such a wheel is said to have three planes of freedom The wheel or rotor is free to rotate in any plane in relation to the base and is so balanced that with the gyro wheel at rest, it will remain in the position in which it is placed Restricted or semirigidly mounted gyroscopes are those mounted so that one of the planes of freedom is held fixed in relation to the base

There are two fundamental properties of gyroscopic action—rigidity in space and

precession

Rigidity in Space:

Rigidity in space refers to the principle that a

gyro-scope remains in a fixed position in the plane in which

it is spinning

Procession:

Precession is 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; rather, it occurs at a point that is 90° later in the direction of rotation

1 Attitude Indicators:

The first attitude instrument (AI) was originally referred to as an artificial horizon, later

as a gyro horizon; now it is more properly called an attitude indicator Its operating mechanism is a small brass wheel with a vertical spin axis, spun at a high speed by either a stream of air impinging on buckets cut into its periphery, or by an electric motor The gyro is mounted in a double gimbal, which allows the aircraft to pitch and roll about the gyro as it remains fixed in space

A horizon disk is attached to the gimbals so it remains in the same plane as the gyro, and the aircraft pitches and rolls about it On early instruments, this was just a bar that represented the horizon, but now it is a disc with a line representing the horizon and both pitch marks and bank-angle lines The top half of the instrument dial and horizon disc is blue, representing the sky; and the bottom half is brown, representing the ground A bank index at the top of the instrument shows the angle of bank marked on the banking scale with lines that represent 10°, 20°, 30°, 45°, and 60°

The older artificial horizons were limited in the amount of pitch or roll they could tolerate, normally about 60° in pitch and 100° in roll After either of these limits was exceeded, the gyro housing contacted the gimbals, applying such a precessing force that the gyro tumbled Because of this limitation, these instruments had a caging mechanism that locked the gyro in its vertical position during any maneuvers that exceeded the instrument limits Newer instruments do

not have these restrictive tumble limits; therefore, they do not have a caging mechanism

When an aircraft engine is first started and pneumatic or electric power is supplied to the instruments, the gyro is not erect A self-erecting mechanism inside the instrument actuated by the force of gravity applies a precessing force, causing the gyro to rise to its vertical position This erectioncan take as long as 5 minutes, but is normally done within 2 to 3 minutes

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

2 Heading Indicators:

A magnetic compass is a dependable instrument used as a backup instrument

Although very reliable, it has so many inherent errors that it has been supplemented with gyroscopicheading indicators

The gyro in a heading indicator is mounted in a double gimbal, as in an attitude

indicator, but its spin axis is horizontal permitting sensing of rotation about the vertical axis of the aircraft Gyro heading indicators, with the exception of slaved gyro indicators, are not north seeking, therefore they must be manually set to the appropriate heading by referring to a magnetic compass Rigidity causes them to maintain this heading indication, without the oscillation and other errors

inherent in a magnetic compass

Older directional gyros use a drum-like card marked in the same way as the magnetic compass card The gyro and the card remain rigid inside the case with the pilot viewing the

card from the back This creates the possibility the pilot might start a turn in the wrong direction similar

to using a magnetic compass A knob on the front of the instrument, below the dial, can be pushed in to engage the gimbals This locks the gimbals allowing the pilot to rotate the gyro and card until the number opposite the lubber line agrees with the magnetic compass When the knob is pulled out, the gyro remains rigid and the aircraft is free to turn around the card

Directional gyros are almost all air-driven by evacuating the case and allowing filtered air to flow into the case and out through a nozzle, blowing against buckets cut in the periphery of the wheel The Earth constantly rotates at 15° per hour while the gyro is maintaining a position relative

to space, thus causing an apparent drift in the displayed heading of 15° per hour When using these instruments, it is standard practice to compare the heading indicated on the directional gyro with the magnetic compass at least every 15 minutes and to reset the heading as necessary to agree with the magnetic compass

Heading indicators work on the same principle as the older horizontal card indicators, except that the gyro drives a vertical dial that looks much like the dial of a vertical card magnetic compass The heading of the aircraft is shown against the nose of the symbolic aircraft on the

instrument glass, which serves as the lubber line A knob in the front of the instrument may be pushed

in and turned to rotate the gyro and dial The knob is spring loaded so it disengages from the gimbals as soon as it is released This instrument should be checked about every 15 minutes to see if it agrees with the magnetic compass

3 Turn Indicator:

Attitude and heading indicators function on the principle of rigidity, but rate instruments such as the turn-and-slip indicator operate on precession Precession is the characteristic of a gyroscope that causes an applied force to produce a movement, not at the point of application, but at a point 90° from the point of application in the direction of rotation

no inertia acting on the ball, and it remains in the center of the tube between two wires In a turn made with a bank angle that is too steep, the force of gravity is greater than the inertia and the ball rolls down

to the inside of the turn If the turn is made with too shallow a bank angle, the inertia is greater thangravity and the ball rolls upward to the outside of the turn

The inclinometer does not indicate the amount of bank, nor does it indicate slip; it only indicates the relationship between the angle of bank and the rate of yaw

Components of a Basic System:

Figure shows a basic system with the addition of a power-driven pump and other essential components These components are the filter, pressure regulator, accumulator, pressure gauge, relief valve, and two check valves The function of these components is described below

The filter removes foreign particles from the fluid, preventing moisture, dust, grit, and other undesirable matter from entering the system The pressure regulator unloads or relieves the power-driven pump when the desired pressure in the system is reached Therefore,

it is often referred to as an unloading valve With none of the actuating units operating, the pressure in the line between the pump and selector valve builds up to the desired point

A valve in the pressure regulator automatically opens and fluid is bypassed back

to the reservoir (The bypass line is shown in figure, leading from the pressure regulator to the return line.)

NOTE: Many aircraft hydraulic systems do not use a pressure regulator These

systems use a pump that automatically adjusts to supply the proper volume of fluid as needed

The accumulator serves a twofold purpose 1 It serves as a cushion or shock

absorber by maintaining an even pressure in the system 2 It stores enough fluid under pressure to provide for emergency operation of certain actuating units The accumulator is designed with a compressed-air chamber separated from the fluid by a flexible diaphragm, or a removable piston

The pressure gauge indicates the amount of pressure in the system The relief valve is a safety valve installed in the system When fluid is bypassed through the valve to the return line, it returns to the reservoir This action prevents excessive pressure in the system Check valves allow the flow of fluid in one direction only There are numerous check valves installed at various points in the lines of all aircraft hydraulic systems

A careful study of figure shows why the two check valves are necessary in this system One check valve prevents power pump pressure from entering the hand-pump line The other valve prevents hand-pump pressure from being directed to the accumulator

6 Reservoir 2 Power pump 3 Filter 4 Pressure regulator 5 Accumulator

6 Check valves 7 Hand pump 8 Pressure gauge 9 Relief valve 10 Selector valve

11 Actuating unit

AIRCRAFT PNEUMATIC SYSTEMS

Introduction:

There are two types of pneumatic systems currently used in naval

aircraft One type uses storage bottles for an air source, and the other has its own air compressor

Components of Basic System:

Generally, the storage bottle system is used only for emergency operation See figure This system has an air bottle, a control valve in the cockpit for releasing the contents of the cylinders, and a ground charge (filler) valve The storage bottle must be filled with

compressed air or nitrogen prior to flight

Air storage cylinder pneumatic systems are in use for emergency brakes, emergency landing gear extension, emergency flap extension, and for canopy release mechanisms

When the control valve is properly positioned, the compressed air in the storage bottle is routed through the shuttle valve to the actuating cylinder

NOTE: The shuttle valve is a pressure-operated valve that separates the normal hydraulic system from the emergency pneumatic system When the control handle is returned to the normal position, the air pressure in the lines is vented overboard through the vent port of the control valve

The other type of pneumatic system in use has its own air compressor It also has other equipment necessary to maintain an adequate supply of compressed air during flight Most systems of this type must be serviced on the ground prior to flight The air compressor used in most aircraft is driven by a hydraulic motor Aircraft that have an air compressor use the compressed air for normal and emergency system operation

- End of Lecture -