1. 11
•History
•Types Of Engines used on Aircraft
•Basic understanding of their operation
•Sections / Modules of a Gas Turbine Engine.
•Significant Components installed on the Engine.
For Flight Operation Officers
Engr, Zafar I. Jami

2. 22
Short History
 The engine that Wright Brothers used to power the
first aircraft was a standard automobile piston engine
based on Otto Cycle.
 Later, engines were made lighter and more powerful.
These requirements lead to development of several
versions. More common types in use were:
 HO, V type liquid cooled and Radial air cooled.
 World War II brought rapid developments and advent
of the Jet age. These also blossomed into several types:
 Turbojet, Turboprop and Turbofans.

3. 33
Piston Engines.
Piston Engines are based on Otto Cycle.
Which is same as that used for most
automobile engines. It normally works on a
Four Stroke Cycle consisting of:
1. Intake
2. Compression
3. Power and
4. Exhaust strokes.
There are three most common types which are
named according to the arrangement of
cylinders around the crankshaft. These are
• Horizontally Opposed (4 to 8 Cylinders)-
80 to 400 Hp range, aircooled,
• Vee type ( 8-12 cylinders) usually water
cooled. Used on high performance
aircraft in WW II due lower Drag.
• Radial (7 to 11 in Single Row or) 14 to 18 in
Double Row. Aircooled. -900 to 4000 Hp
range.

4. 44
Gas Turbine Engines.
•They work on Brayton Cycle
where:
• The air is compressed in
the Compressor.
•Then it is burned in the
Combustor.
•The hot gasses pass through
the turbines that extract
energy to run the
Compressor, Fan and
accessories installed on the
Engine.
•Then the gasses exhaust at
very high velocity producing
the required Thrust.
 Typical Brayton Cycle for
a Gas Turbine.
Exhaust
Nozzle

5. 55
Types of Gas Turbine Engines
• The first generation Gas Turbine Engines were
Turbojets that sucked air from the front and
exhausted them at high speed from rear
producing reaction that pushed the aircraft
forward.
•Next came the Turbofans where a part of air was
exhausted without going through the core
producing additional thrust. These are also called
Bypass Jets and are more efficient than the
turbojets.
•Concurrently, for lower speed application, the
energy from exhaust was used to drive the
propeller after reducing its speed through a
Gearbox. These are called Turboprops.
• The same engine, when used to power the
Helicopter’s Rotor instead of a Propeller, is called
a Turbo shaft Engine.
Early Bypass jet
Fan/LPC Core LPT

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How an Engine powers the
aircraft to fly?
 Propeller Aircraft:
 Propellers have airfoil shaped
blades that generate Lift in
forward direction when rotated
by the Engine.
 Jet Aircraft:
 It works on the Newton’s Third
Law of Motion:
 Every Action Has a Reaction.
 It discharges a jet of fast moving
gas backward whose reaction
pushes the aircraft forward.

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Engines and Powerplant
 The Engine in the form that is Ready For Installation
(RFI) on an Aircraft, is commonly called a
Powerplant.
 It consists of Engine + QEC (Quick Engine Change):
 QEC – consists of Plumbing, Harness and Components
peculiar to a position on an aircraft. Commonly installed
Components on the engine include:
 Starter
 Hydraulic Pump/s.
 IDG (or CSD + Generators).
 Anti-icing valves and ducts.
 Customer Bleeds.
7

8. Note: - All OEMs have their own divisions and names
for Modules.
8
Basic Sections (or Modules ) of a
Modern Turbofan Engine – (1).
A. Fan and LPC: It consists of a Single Stage fan which has a much
larger diameter than other stages and pushes the bypass air out
without passing through the “Core” of the engine. In addition
it has a few (usually 3-5 stages) of Low pressure compressor to
reduce load on HPC.
B. Core Module: This consists of:
a. High Pressure Compressor (HPC): This usually has 7-14 stages of
alternate rows of blades and vanes that progressively increase the
pressure to desired value.
b. Diffuser and Combustor: In this section, the passage is widened to
slow down the airflow and increase its static pressure. The air is
then led to Combustor unit where it is mixed with atomized fuel
which burns to provide high energy.

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Basic Sections (or Modules) of a
Turbofan Engine (2).
c. High Pressure Turbine (HPT): It consists of One or
Two Stage of Vanes and Blades. First stage vanes face
the highest temperature. It extracts power to run the
HPC and the Accessory Gear Box.
C. Low Pressure Turbine(LPT): This usually has 3-6
stages of alternate rows of blades and vanes that
progressively extract power to rotate the Fan/LPC.
D. Accessory Drive Gear Box (AGB): It provides a drive
for all components and accessories installed on the
engine. It gets power from the HP Shaft through a
series of gears and shafts.

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Some significant Components
installed on a Jet Engine…. (1)
Fuel Pump : It gets fuel from the aircraft when the
fuel shut off valve is in ON position. It usually have two
stages. It delivers more fuel than required in the
engine. The next unit bypasses the excess fuel back to
output of the first (centrifugal) stage.
 Engine Fuel Control: In general, it receives fuel
from the fuel pump, then computes the fuel required by
the engine and bypasses the remaining fuel back to Fuel
Pump. It can be Fully Mechanical, Hybrid or Fully
Electronic (Digital)- which are also called EEC or FADEC .

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Some significant Components
installed on a Jet Engine…. (2)
 Starter : They are either Electric or Pneumatic driven.
Pneumatic starters are more common on larger engines. But the
latest trend is again towards Electric starters.
 They are mounted on Accessory Gear Box and drive Engine’s
(HP) shaft through a gear train till the engine reaches a self
sustaining RPM.
 Pneumatic supply can be obtained from following sources.
 Ground Start Cart
 Auxiliary Power Unit
 Which itself has an electric starter that can be run on Aircraft
batteries.
 Through Cross Bleed from another running engine.
 Through air bottles in emergency.

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Significant Engine Components..(3)
Electric Generator:
 They are also mounted on the Accessory Drive
Gearbox.
 As they have to run at constant RPM, power to run the
Generator is transmitted from engine’s HP shaft
through a Constant Speed Drive Unit.
 On newer aircraft, this unit is integral with the
Generator and housed in the same unit. Together, they
are called IDG.
 Usual supply from the generator is at 115V /400Hz.

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Significant Engine Components… (4)
Hydraulic Pumps and Plumbing.
 Hydraulic power is needed in aircraft to operate
Landing Gears and several other components.
 Larger twin engined aircraft usually have two pumps
on each engine, while the smaller ones have a single
pump.
 On most aircraft they provide hydraulic fluid at 3000
psi.
 There are three tubes for pressure, scavenge and drain
fluids which are joined with tubing from aircraft near
top of the pylon.

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Significant Engine Components… (5)
Engine Anti-icing and Customer Bleeds.
 As engine compressor is a ready source of high
temperature and high pressure air, some of it is bled
out for different uses.
 Anti-icing air is bled from later sages, which is very
hot. As and when selected, it runs through the lip of
nose cowl or wing Leading edge and exhausts to
atmosphere after heating it.
 Customer Bleed air is often taken from alternately
from one of two stages in compressor (depending
upon requirement), and fed to the aircraft’s air-
conditioning and pressurization system for controlling
Cabin’s pressure and temperature.

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What a Flight Dispatching Officer must
know about the Engines.
 As the weight of the aircraft
increases, the engine has to
work harder, not only
during takeoff, but also
during Cruise and Landing.
 This can result in two
things:
1. Engine under certain
conditions may fail.
2. Repeated applications of
higher power will lower its
life on wing.
 So remember, the Engines
that work harder die young.
 Also, when such engines go to
the Shop, they are in more
depilated condition and cost
much more.
 As such, always try to
minimize All Up Weight
and ensure that it never
exceeds the weight permitted
by the OEM’s manuals.

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How to be a good ‘Weight watcher’
of an Aircraft
Be very vigilant to look for the
following:
 Unaccounted weights
specially in passengers’
baggage and hand-carries.
 Higher temperatures than
expected at the time of
takeoff.
 Specially, a delayed
morning flight.
o Excess fuel load even
within spec limits is bad for
engines’ health.
 .Avoid fuel tankering for
economic reasons unless it
will pay for added engine
maintenance costs.
 Consider safety first. If the
recommended weight is
being exceeded, never
hesitate to recommend
offloading of passengers,
baggage or cargo even if it
means loss of revenue and
delays.

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Thank You!
Warning
The presentation has been specifically prepared by the author for a
Pakistan CAA approved course conducted at Academy for
Aviation Excellence and material or pictures may not be copied
or used without specific authority from the author the Academy.
Some material may also have a copyright.