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INTERNSHIP REPORT
GROUP MEMBERS: Syed Muhammad Labeeq (AU-045)
Shamsher Gokrani (AU-005)
INSTITUTE: NED University of Engineering and Technology
DEPARTMENT: Automotive Department NEDUET
CLASS: T.E (THIRD YEAR OF ENGINEERING)
BATCH: 2012-2013
YEAR: 2015

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Acknowledgement
The whole praise is to almighty Allah, creator of this universe. Who made us the super
creature with great knowledge and who able me to accomplish this work, we feel great
pleasure in expressing our deepest appreciation and heartiest gratitude to the staff of PIA
Engineering for their guidance and great help during the internship period.
We would like to express our deepest affection for our parents and our friends who prayed
for our success and encouraged us during this internship period. We appreciate and
acknowledge the patience, understanding and love provided by employees of PIA
ENGINEERING.
Special thanks to SIR SHABBIR and SIR AIJAZ who had been very friendly, co-operated with
us throughout our internship period in BLOCK and made it possible for us to learn and
gather information. These are the people who in spite of their busy scheduling took time
out to explain to us the procedures and mechanics of work in the organization.

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Contents
PIA ENGINEERING - AREAS AND SERVICES .............................................................................................................5
Base Maintenance..............................................................................................................................................5
C check...........................................................................................................................................................5
D check...........................................................................................................................................................5
Inspections .........................................................................................................................................................6
Lap Joint Modifications ......................................................................................................................................6
Avionics Modifications .......................................................................................................................................6
Painting ..............................................................................................................................................................6
Line Maintenance...............................................................................................................................................6
A check...........................................................................................................................................................7
B check...........................................................................................................................................................7
Power Plant and Overhaul .............................................................................................................................7
INTRODUCTION TO AEROPLANE.............................................................................................................................7
NOMENCLATURE or TECHNICAL TERM...................................................................................................................8
Aerodynamics.....................................................................................................................................................8
Air Currents ........................................................................................................................................................8
Relative Motion..................................................................................................................................................8
Bernoulli ‘principle .............................................................................................................................................8
Airfoil..................................................................................................................................................................8
Angle of Attack...................................................................................................................................................9
Cockpit................................................................................................................................................................9
Control Stick or Control Column ........................................................................................................................9
Aileron................................................................................................................................................................9
Elevator ..............................................................................................................................................................9
Flap.....................................................................................................................................................................9
Rudder................................................................................................................................................................9
Rudder Pedal......................................................................................................................................................9
Stabilizer...........................................................................................................................................................10
FUNDAMENTAL PRINCIPLES OF AIRCRAFT FLIGHT...............................................................................................10
Lift ....................................................................................................................................................................10

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Weight..............................................................................................................................................................11
Thrust ...............................................................................................................................................................11
Drag..................................................................................................................................................................11
AIRCRAFT FLIGHT CONTROL .................................................................................................................................11
Aileron..............................................................................................................................................................12
Elevator ............................................................................................................................................................12
Rudder..............................................................................................................................................................12
Wing Flaps........................................................................................................................................................12
Landing gear.....................................................................................................................................................12
FLIGHT DIRECTIONAL CONTROL ...........................................................................................................................13
The Axes of Rotation ........................................................................................................................................13
The Longitudinal Axis .......................................................................................................................................13
The Lateral Axis ................................................................................................................................................14
The Vertical Axis...............................................................................................................................................15
ENGINE TYPES and APPLICATIONS........................................................................................................................15
Centrifugal Compressor Engines ......................................................................................................................15
Principal Advantages of Centrifugal Compressor.............................................................................................16
Axial Flow Compressor Engines........................................................................................................................16
Advantages and Disadvantages........................................................................................................................16
Axial-Centrifugal Compressor Engine...............................................................................................................16
CHARACTERISTICS AND APPLICATIONS ................................................................................................................17
The turbojet engine:.........................................................................................................................................17
The turboprop engine: .....................................................................................................................................17
The turbofan engine:........................................................................................................................................18
ENGINE THEORY ...................................................................................................................................................18
Operation .........................................................................................................................................................18
Jet Engine Equation..........................................................................................................................................18
Factors Affecting Thrust ...................................................................................................................................19
Engine Station Designations.............................................................................................................................19

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PIA ENGINEERING - AREAS AND SERVICES
Aircraft maintenance checks are periodic inspections that have to be done on all commercial/civil
aircraft after a certain amount of time or usage; military aircraft normally follow specific
maintenance programs which may or may not be similar to those of commercial/civil operators.
Airlines and other commercial operators of large or turbine-powered aircraft follow a continuous
inspection program approved by the Federal Aviation Administration (FAA) in the United States,[1]
or by other airworthiness authorities such as Transport Canada or the European Aviation Safety
Agency (EASA). Under FAA oversight, each operator prepares a Continuous Airworthiness
Maintenance Program (CAMP) under its Operations Specifications or "OpSpecs". The CAMP includes
both routine and detailed inspections. Airlines and airworthiness authorities casually refer to the
detailed inspections as "checks", commonly one of the following: A check, B check, C check, or D
check. A and B checks are lighter checks, while C and D are considered heavier checks.
Base Maintenance
Cost-effective and high quality Maintenance, Repair and Overhaul services for airline fleet
C check
This is performed approximately every 20–24 months or a specific amount of actual flight hours (FH)
or as defined by the manufacturer. This maintenance check is much more extensive than a B check,
requiring a large majority of the aircraft's components to be inspected. This check puts the aircraft
out of service and until it is completed, the aircraft must not leave the maintenance site. It also
requires more space than A and B checks. It is, therefore, usually carried out in a hangar at a
maintenance base. The time needed to complete such a check is generally 1–2 weeks and the effort
involved can require up to 6,000 man-hours. The schedule of occurrence has many factors and
components as has been described, and thus varies by aircraft category and type.
D check
This is by far the most comprehensive and demanding check for an airplane. It is also known as a
"heavy maintenance visit" (HMV). This check occurs approximately every 6 years. It is a check that,
more or less, takes the entire airplane apart for inspection and overhaul. Also, if required, the paint
may need to be completely removed for further inspection on the fuselage metal skin. Such a check
can usually demand up to 50,000 man-hours and it can generally take up to 2 months to complete,
depending on the aircraft and the number of technicians involved. It also requires the most space of
all maintenance checks, and as such must be performed at a suitable maintenance base. Given the
elevated requirements of this check and the tremendous effort involved in it, it is also by far the
most expensive maintenance check of all, with total costs for a single visit ending up well within the
million-dollar range.
Because of the nature and the cost of such a check, most airlines — especially those with a large
fleet — have to plan D checks for their aircraft years in advance. Often, older aircraft being phased
out of a particular airline's fleet are either stored or scrapped upon reaching their next D check, due
to the high costs involved in comparison to the aircraft's value. On average, a commercial aircraft
undergoes 2–3 D checks before being retired. Many maintenance, repair and overhaul(MRO) shops
claim that it is virtually impossible to perform a D check profitably at a shop located within the
United States. As such, only a few of these shops offer D checks

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Inspections
• Ageing Aircraft Corrosion Prevention and Control Program (CPCP)
• Supplemental Structural Inspection (SSI)
Lap Joint Modifications
PIA Engineering is one of the pioneers in Asia to undertake this major modification. The ACOH facility
has now been fully developed for the Lap Joint Modification on the B-737.
Structural Modifications
The Base Maintenance team is backed up with a state-of-the art Structure Repair Shop which can
perform repairs on individual structural components of aircraft and also has the capability to
develop repair schemes
Avionics Modifications
PIA Engineering has been involved in all the recent aircraft retrofit programs, based on new
requirements; such as TCAS-II, SUPERAHARS, GPS, EGPWS 8,33 kHz VHF, RVSM, and B-RNAV. With a
group of avionics modification specialists, no installation job or STC implementation is too large or
too complex for them. They have successfully completed a full installation of the MAS -2000E and
also have in-house expertise in MAS-3000E installations and other In Flight Entertainment solutions.
Painting
Base Maintenance team offers comprehensive aircraft painting services, including but not limited to:
• Sign Painting
• Decals
• Placards
• Drawing of Logos
• Engraving of Cockpit Instrument Panels
• Write-ups in the Interior & Exterior of Aircrafts
Line Maintenance
highly skilled Line Maintenance team in Karachi undertakes and releases the full range of cabin tasks
and In Flight Entertainment (IFE) checks during transit, along with regular transit tasks for Boeing
777, 747, 737 and Airbus A310, A300 B4, Fokker F-27, and ATR-42, under CAA Pakistan. PIA
Engineering also maintains the appearance and quality of your aircraft's cabin and exterior. Line
Maintenance facilities cover the complete range of an aircraft's routine maintenance and inspection
requirements. We have sufficient aircraft support dock installations in 4 hangars with the requisite
trained manpower and tooling to undertake simultaneous work on various types of aircraft in your
fleet, around the clock.

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PIA Engineering offers excellent Line Maintenance at all International/Commercial airports in
Pakistan and large numbers of line stations around the globe.
A check
This is performed approximately every 250 flight hours or 200–300 cycles. It needs about 20–50
man-hours and is usually performed overnight at an airport gate. The actual occurrence of this check
varies by aircraft type, the cycle count (takeoff and landing is considered an aircraft "cycle"), or the
number of hours flown since the last check. The occurrence can be delayed by the airline if certain
predetermined conditions are met.
B check
This is performed approximately every 6 months. It needs about 120-150 man-hours, depending on
the aircraft, and is usually completed within 1–3 days at an airport hangar. A similar occurrence
schedule applies to the B check as to the A check. However, B checks may also be incorporated into
successive A checks, i.e.: Checks A-1 through A-10 complete all the B check items.
Power Plant and Overhaul
PIA's Power Plant Shops offer comprehensive repair, overhaul modification, testing and calibration
services for a range of aircraft engines and APUs
INTRODUCTION TO AEROPLANE
It was, of course, the birds who were responsible for the whole complicated story and business. A
man with the brain of a scientist began to think seriously about attainment of the dream. This was
Leonado da Vinci (1452-1519), whose detail study of bird flight nevertheless led him to the
erroneous conclusion that men muscular power, so superior to that of the birds, should enable him
to fly in a properly constructed ornithopter, or flapping-wing aircraft.
In 1680, Giovanni Alphonso Borelli's has a result of his detailed study of bird flight, man did not have
the power output needed to lift himself and a machine into the air. This brought an end to
practically all heavier-than-air experiments until nineteenth century.
On October 15, 1783, Jean-Francois had made a flight in a Montgolfier hot-air balloon tethered flight
for 4 minutes 24 second. Less than two month later a hydrogen-filled balloon had completed a
successful two-hour free flight.
German Otto Lilienthal (1848-1896), whose graceful and beautifully-constructed hang-gliders enable
him to become the first man in the world to fly confidently and regularly, total more than 2000
flights. He did not develop control surfaces for his gliders, but rely on body movements to provide
limited control in the three axes of pitch, yaw, and roll. He lost his life at age of 48 on 10 August 1896
due to one of his gliders stalled and crashed to the ground. The persons who pioneer of the gliders
were Otto Lilienthal (German), Percy Pilcher (England) He also lost his life in a glider clashed three
years after Lilienthal, and Octave Chanute (American)(1832-1910)
Wilbur (1867-1912) and Orville (1871-1948) Wright, had been interested in the possibility of
mechanical flight in the early years. By 1900, they became friends with Chanute. Chanute
encouraged, providing information, and directly assisted the Wrights to achieve their goal of power
flight later. First flight they fled the flyer was on 17 December 1903.This is generally accepted as the

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first man to accomplished the dream. Even through there are some controversy over the first
powered aircraft.
Alberto Santos-Dumont a little Brazilian living in France. During 1906, with his No.14-bis which was
power by a 50 horsepower Antoinette engine, he made a first flight of 60 meter at Bagatelle, Paris
on 23 October 1906. Some people believed that Santos-Dumont really had made the first power
flight in history.
NOMENCLATURE or TECHNICAL TERM
Although we will describe certain terms or parts of airplane more in the next sections as we go
along, but we should familiar with all of these terms in order to understand the airplane better.
Aerodynamics
Aero is derived from the Greek word meaning AIR, and Dynamics comes from the Greek word
meaning Power, or branch of physics which considers bodies in motion and the forces that produce
or change such motion. When Aero is combined with Dynamics, we have Aerodynamics, Meaning
"The science relating to the effects produced by air or other gases in motion".
Air Currents
Air currents are movement of the air with respect to the earth. If the air is rising from the earth , it is
called a Vertical Current
Relative Motion
Motion is a movement. If an object changes it position, it is in motion. Relative Motion defined as an
object which has moved or has changed its position with Respect to some other object. An Airplane
must Relative motion between Airplane and the Air in order to fly. The velocity of this motion is
called the True Airspeed have
Bernoulli ‘principle
This principle states that as the air velocity increases, the pressure decreases; and as the velocity
decreases, the pressure increases
Airfoil
Air foil is technically defined as any surface, such as an airplane aileron, elevator, rudder, or wing,
designed to obtain reaction from the air through which it moves.

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Angle of Attack
Angle of attack is the acute angle measured between the chord of an airfoil and the relative wind.
Cockpit
Cockpit is the pilot's compartment which is separated from the rest of the cabin.
Control Stick or Control Column
A vertical lever or column by mean of which the pilot operates the longitudinal and lateral control
surfaces of the airplane. The elevator is operated by fore-and-aft movement of the stick or column,
and ailerons are moved by sideways movement of the stick or turn the wheel to left or right.
Aileron
One of a pair of movable control surfaces attached to the trailing edge of each wing tip, the purpose
of which is to control the airplane in roll by creating unequal or opposing lifting forces on the
opposite sides of the airplane.
Elevator
A movable auxiliary airfoil or control surface designed to impress a pitching movement on the
airplane, that is, to cause rotation about the lateral axis.
Flap
A hinged, pivoted, or sliding airfoil or plate, normally located at the trailing edge of a wing, extended
or deflected to increase the lift and/or drag, generally used at takeoff and landing.
Rudder
A hinged or movable auxiliary airfoil used to impress a yawing moment on the aircraft.
Rudder Pedal
Either one of a pair of cockpit pedals for operating a rudder or other directional control device. The
pedals are on the floor and feet operated.

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Stabilizer
A fixed or adjustable airfoil or vane that provides stability for an aircraft.
FUNDAMENTAL PRINCIPLES OF AIRCRAFT FLIGHT
The plane in flight at cruising speed is subjected to 4 forces. These 4 principal forces operating the
plane in flight are schematized on the figure below.
(1) Lift, (2) Gravity force or Weight, (3) Thrust, and (4) Drag.
Lift and Drag are considered aerodynamics forces because they exist due to the movement of the
Airplane through the Air.
Lift
Lift is produced by a lower pressure created on the upper surface of an airplane's wings compared to
the pressure on the wing's lower surfaces,causing the wing to be LIFTED upward. The special shape
of the airplane wing (airfoil) is designed so that air flowing over it will have to travel a greater
distance and faster resulting in a lower pressure area (see illustration) thus lifting the wing upward.
Lift is that force which opposes the force of gravity (or weight).
Lift depends upon (1) shape of the airfoil (2) the angle of attack (3) the area of the surface exposed
to the airstream (4) the square of the air speed (5) the air density.

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Weight
The weight acts vertically downward from the center of gravity (CG) of the airplane.
Thrust
Thrust is defined as the forward direction pushing or pulling force developed by aircraft engine. This
includes reciprocating engines, turbojet engines, turboprop engines.
Drag
Drag is the force which opposes the forward motion of airplane. specifically, drag is a retarding force
acting upon a body in motion through a fluid, parallel to the direction of motion of a body. It is the
friction of the air as it meets and passes over an airplane and its components. Drag is created by air
impact force, skin friction, and displacement of the air.
AIRCRAFT FLIGHT CONTROL
An airplane is equipped with certain fixed and movable surfaces or airfoil which provide for stability
and control during flight. These are illustrated in the picture.

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Aileron
Aileron may be defined as a movable control surface attached to the trailing edge of a wing to
control an airplane in the roll, that is, rotation about the longitudinal axis.
Elevator
Elevator is defined as a horizontal control surface, usually attached to the trailing edge of horizontal
stabilizer of an airplane, designed to apply a pitching movement to the airplane. A pitching
movement is a force tending to rotate the airplane about the lateral axis,that is nose up or nose
down.
Rudder
Rudder is a vertical control surface usually hinged to the tail post aft of the vertical stabilizer and
designed to apply yawing movement to the airplane that is to make it turn to the right or left about
the vertical axis.
Wing Flaps
Wing flap are hinged or sliding surfaces mounted at the trailing edge of wings and designed to
increase the camber of the wings. The effect is to increase the lift of the wings.
Landing gear
Landing gear is the undercarriage of an aircraft or spacecraft and is often referred to as such. For
aircraft, the landing gear supports the craft when it is not flying, allowing it to take off, land and
usually to taxi without damage. Wheels are typically used but skids, skis, floats or a combination of
these and other elements can be deployed depending both on the surface and on whether the craft
only operates vertically (VTOL) or is able to taxi along the surface. Faster aircraft usually have
retractable undercarriage, which folds away during flight to reduce air resistance or drag.
For launch vehicles and spacecraft landers, the landing gear is typically designed to support the
vehicle only post-flight, and are not used for takeoff or surface movement.

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FLIGHT DIRECTIONAL CONTROL
The Axes of Rotation
An airplane has three axes of rotation, namely, the longitudinal axis, the vertical axis, and the lateral
axis. See figure below and you will understand what we mean. The simplest way to understand the
axes is to think of them as long rods passing through the aircraft where each will intersect the other
two. At this point of intersection, called the center of gravity.
The Axis that extends lengthwise (nose through tail) is call the longitudinal axis, and the rotation
about this axis is called "Roll"
The axis that extends crosswise (wing tip through wing tip) is called the lateral axis, and rotation
about this axis is called "Pitch"
The axis that passes vertically through the center of gravity (when the aircraft is in level flight) is
called the vertical axis, and rotation about this axis is called "Yaw"
The Longitudinal Axis

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The Axis Running from the nose to the tail of an aircraft is the longitudinal axis (see picture above).
The movement around the longitudinal axis is called roll. The cause of movement or roll about the
axis is the action of the ailerons. Ailerons are attached to the wing and control through the control
column in a manner that ensures one aileron will deflect downward when the other is deflected
upward.
When an aileron is not in perfect alignment with the total wing, it changes the wing's lift
characteristics. To make a wing move upward, the aileron on that wing must move downward. The
wing that has aileron downward produce more lift on that wing. the wing that has the aileron
upward will reduce lift on that wing . This cause the aircraft to roll.
The ailerons are attached to the cockpit control column by mechanical linkage. When the control
wheel is turned to the right (or the stick is move to the right), the aileron on the right wing is raised
and the aileron on the left wing is lowered. This action increases the lift on the left wing and
decreases the lift on the right wing, thus causing the aircraft to roll to the right. Moving the control
wheel or stick to the left reverses this and causes the aircraft to roll to the left.
The Lateral Axis
The lateral axis runs from wingtip to wingtip. The movement around the lateral axis is called pitch.
What causes this pitching movement? It is the elevator which is attached to the horizontal stabilizer.
The elevator can be deflected up or down as the pilot moves the control column (or stick) backward
or forward.

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Movement backward on the control column moves the elevator upward. (see picture above) The
relative wind (RW) striking the top surface of the raised elevator pushes the tail downward. This
motion is around the lateral axis, as the tail moves (pitches) downward, the nose moves (pitches)
upward and the aircraft climbs.
Movement forward on the control column moves the elevator downward. The relative wind (RW)
striking the lower surface of the elevator causes the tail to pitch up and the nose of the aircraft
downward causing the airplane to dives
The Vertical Axis
The third axis which passes through from the top of the aircraft to
the bottom is called the vertical or yaw axis. The aircraft's nose
moves about this axis in a side-to-side direction. The airplane's
rudder, which is moved by pressing on the rudder pedals which are
on the floor. The airplane's rudder is responsible for movement
about this axis.The rudder is a movable control surface attached to
the vertical fin of the tail assembly. By pressing the proper rudder
pedal, right pedal moves the rudder to the right, and left pedal
moves the rudder to the left, when pilot press the left rudder pedal,
that mean the pilot sets the rudder so that it defects the relative
wind to the left. This then creates a force on the tail, causing it to
move to the right and the nose of the aircraft to yaw to the left.
ENGINE TYPES and APPLICATIONS
Most of modern passenger and military aircraft are powered by gas turbine engines, which are also
called jet engines. There are several types of jet engines, but all jet engines have some parts in
common. Aircraft gas turbine engines can be classified according to (1) the type of compressor used
and (2) power usage produces by the engine.
Compressor types are as follows:
1. Centrifugal flow
2. Axial flow
3. Centrifugal-Axial flow.
Power usage produced are as follows:
1. Turbojet engines
2. Turbofan engines.
3. Turboshaft engines.
Centrifugal Compressor Engines
Centrifugal flow engines are compress the air by accelerating air outward perpendicular to
the longitudinal axis of the machine. Centrifugal compressor engines are divided into Single-
Stage and Two-Stage compressor. The amount of thrust is limited because the maximum
compression ratio.

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Principal Advantages of Centrifugal Compressor
1. Light Weight
2. Simplicity
3. Low cost.
Axial Flow Compressor Engines
Axial flow compressor engines may incorporate one, two, or three spools (Spool is defined as a
group of compressor stages rotating at the same speed). Two spool engine, the two rotors operate
independently of one another. The turbine assembly for the low pressure compressor is the rear
turbine unit. This set of turbines is connected to the forward, low pressure compressor by a shaft
that passes through the hollow center of the high pressure compressor and turbine drive shaft.
Advantages and Disadvantages
Advantages: Most of the larger turbine engines use this type of compressor because of its ability to
handle large volumes of airflow and high pressure ratio.
Disadvantages: More susceptible to foreign object damage, Expensive to manufacture, and It is very
heavy in comparison to the centrifugal compressor with the same compression ratio.
Axial-Centrifugal Compressor Engine
Centrifugal compressor engine were used in many early jet engines, the efficiency level of single
stage centrifugal compressor is relatively low. The multi-stage compressors are somewhat better,

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but still do not match with axial flow compressors. Some small modern turbo-prop and turbo-shaft
engines achieve good results by using a combination axial flow and centrifugal compressor such as
PT6 Pratt and Whitney of Canada which very popular in the market today and T53 Lycoming engine.
CHARACTERISTICS AND APPLICATIONS
The turbojet engine:
Turbojet engine derives its thrust by highly
accelerating a mass of air, all of which goes through
the engine. Since a high “jet " velocity is required to
obtain an acceptable of thrust, the turbine of turbo
jet is designed to extract only enough power from
the hot gas stream to drive the compressor and
accessories . All of the propulsive force (100% of
thrust) produced by a jet engine derived from
exhaust gas.
The turboprop engine:
Turboprop engine derives its propulsion by the
conversion of the majority of gas stream energy into
mechanical power to drive the compressor,
accessories, and the propeller load. The shaft on
which the turbine is mounted drives the propeller
through the propeller reduction gear system.
Approximately 90% of thrust comes from propeller
and about only 10% comes from exhaust gas.

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The turbofan engine:
Turbofan engine has a duct enclosed fan mounted at the front of the engine and driven either
mechanically at the same speed as the compressor, or by an independent turbine located to the rear
of the compressor drive turbine. The fan air can exit separately from the primary engine air, or it can
be ducted back to mix with the primary's air at the rear. Approximately more than 75% of thrust
comes from fan and less than 25% comes from exhaust gas.
ENGINE THEORY
Operation
The jet engines are essentially a machine designed for the purpose of producing high velocity gasses
at the jet nozzle. The engine is started by rotating the compressor with the starter, the outside air
enter to the engine. The compressor works on this incoming air and delivery it to the combustion or
burner section with as much as 12 times or more pressure the air had at the front. At the burner or
combustion section, the ignition is igniting the mixture of fuel and air in the combustion chamber
with one or more igniters which somewhat likes automobile spark plugs. When the engine has
started and its compressor is rotating at sufficient speed, the starter and igniters are turn off. The
engine will then run without further assistance as long as fuel and air in the proper proportions
continue to enter the combustion chamber. Only 25% of the air is taking part in the actual
combustion process. The rest of the air is mixed with the products of combustion for cooling before
the gases enter the turbine wheel. The turbine extracts a major portion of energy in the gas stream
and uses this energy to turn the compressor and accessories. The engine's thrust comes from taking
a large mass of air in at the front and expelling it at a much higher speed than it had when it entered
the compressor. THRUST, THEN, IS EQUAL TO MASS FLOW RATE TIMES CHANGE IN VELOCITY.
The more air that an engine can compress and use, the greater is the power or thrust that it can
produce. Roughly 75% of the power generated inside a jet engine is used to drive the compressor.
Only what is left over is available to produce the thrust needed to propel the airplane.
Jet Engine Equation
Since Fuel flow adds some mass to the air flowing through the engine, this must be added to the
basic of thrust equation. Some formula do not consider the fuel flow effect when computing thrust
because the weight of air leakage is approximately equal to the weight of fuel added. The following
formula is applied when a nozzle of engine is “choked”, the pressure is such that the gases are
traveling through it at the speed of sound and cannot be further accelerated. Any increase in
internal engine pressure will pass out through the nozzle still in the form of pressure. Even this
pressure energy cannot turn into velocity energy but it is not lost.

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Factors Affecting Thrust
The Jet engine is much more sensitive to operating variables. Those are:
1.) Engine rpm.
2.) Size of nozzle area.
3.) Weight of fuel flow.
4.) Amount of air bled from the compressor.
5.) Turbine inlet temperature.
6.) Speed of aircraft (ram pressure rise).
7.) Temperature of the air.
8.) Pressure of air
9.) Amount of humidity.
Note; item 8, 9 are the density of air.
Engine Station Designations
Station designations are assigned to the various sections of gas turbine engines to enable specific
locations within the engine to be easily and accurately identified. The station numbers coincide with
position from front to rear of the engine and are used as subscripts when designating different
temperatures and pressures at the front, rear , or inside of the engine. For engine configurations
other than the picture below should be made to manuals published by the engine manufacturer.

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N = Speed (rpm or percent)
N1 = Low Compressor Speed
N2 = High Compressor Speed
N3 = Free Turbine Speed
P = Pressure
T = Temperature
t = Total
EGT = Exhaust Gas Temperature
EPR = Engine Pressure Ratio (Engine Thrust in term of EPR). Pt7 / Pt2
Ex.: Pt 2 = Total Pressure at Station 2 (low pressure compressor inlet)
Pt 7 = Total Pressure at Station 7 (turbine discharge total pressure)