Airplane Turbofan Engine Operation and Malfunctions

**Basic Familiarization for Flight Crews**

**Chapter 1**

**General Principles**

**Introduction**

Today\'s modern airplanes are powered by turbofan engines. These engines
are quite reliable, providing years of trouble- free service. However,
because of the rarity of turbofan engine malfunctions, and the
limitations of simulating those malfunctions, many flight crews have
felt unprepared to diagnose engine malfunctions that have occurred.

The purpose of this text is to provide straightforward material to give
flight crews the basics of airplane engine operational theory. This text
will also provide pertinent information about malfunctions that may be
encountered during the operation of turbofan- powered airplanes,
especially those malfunctions that cannot be simulated well and may thus
cause confusion.

While simulators have greatly improved pilot training, many may not have
been programmed to simulate the actual noise, vibration and aerodynamic
forces that certain malfunctions cause. In addition, it appears that the
greater the sensations, the greater the startle factor, along with
greater likelihood the flight crew will try to diagnose the problem
immediately instead of flying the airplane.

It is not the purpose of this text to supersede or replace more detailed
instructional texts or to suggest limiting

the flight crew\'s understanding and working knowledge of airplane
turbine engine operation and malfunctions to the topics and depth
covered here. Upon completing this material, flight crews should
understand that some engine malfunctions can feel and sound more severe
than anything they have ever experienced; however, the airplane is still
flyable, and the first priority of the flight crew should remain \"fly
the airplane.\"

**Propulsion**

![](media/image1.jpeg){width="2.748611111111111in"
height="1.8319444444444444in"}

*Fig 1 showing balloon with no escape path for the air inside. All
forces are balanced.*

Propulsion is the net force that results from unequal pressures. Gas
(air) under pressure in a sealed container exerts equal pressure on all
surfaces of the container; therefore, all the forces are balanced and
there are no forces to make the container move.

![](media/image2.jpeg){width="2.7472222222222222in"
height="1.6229166666666666in"}

*Fig 2 showing balloon with released stem. Arrow showing forward force
has no opposing arrow.*

If there is a hole in the container, gas (air) cannot push against that
hole and thus the gas escapes. While the air is escaping and there is
still pressure inside the container, the side of the container opposite
the hole has pressure against it. Therefore, the net pressures are not
balanced and there is a net force available to move the container. This
force is called ***thrust.***

The simplest example of the propulsion principle is an inflated balloon
(container) where the stem is not closed off. The pressure of the air
inside the balloon exerts forces everywhere inside the balloon. For
every force, there is an opposite force, on the other side of the
balloon, except on the surface of the balloon opposite the stem. This
surface has no opposing force since air is escaping out the stem. This
results in a net force that propels the balloon away from the stem. The
balloon is propelled by the air pushing on the FRONT of the balloon.

**The simplest propulsion engine**

The simplest propulsion engine would be a container of air (gas) under
pressure that is open at one end. A diving SCUBA tank would be such an
engine if it fell and the valve was knocked off the top. The practical
problem with such an engine is that, as the air escapes out the open
end, the pressure inside the container would rapidly drop. This engine
would deliver propulsion for only a limited time.

**The turbine engine**

A turbine engine is a container with a hole in the back end (tailpipe or
nozzle) to let air inside the container escape, and thus provide
propulsion. Inside the container is turbomachinery to keep the container
full of air under constant pressure.

![](media/image3.jpeg){width="2.7472222222222222in"
height="1.3805555555555555in"}

*Fig 3 showing our balloon with machinery in front to keep it full as
air escapes out the back for continuous thrust.*

![](media/image4.jpeg){width="2.7444444444444445in"
height="1.4423611111111112in"}

*Fig 4 showing turbine engine as a cylinder of turbomachinery with
unbalanced forces pushing forward.*

**Components of a turbine engine**

The turbomachinery in the engine uses energy stored chemically as fuel.
The basic principle of the airplane turbine engine is identical to any
and all engines that extract energy from chemical fuel. The basic 4
steps for any internal combustion engine are:

1\) Intake of air (and possibly fuel).

2\) Compression of the air (and possibly fuel).

3\) Combustion, where fuel is injected (if it was not drawn in with the
intake air) and burned to convert the stored energy.

4\) Expansion and exhaust, where the converted energy is put to use.

These principles are exactly the same ones that make a lawn mower or
automobile engine go.

In the case of a piston engine such as the engine in a car or lawn
mower, the intake, compression, combustion, and exhaust steps occur in
the same place (cylinder head) at different times as the piston goes up
and down.

In the turbine engine, however, these same four steps occur at the same
time but in different places. As a result of this fundamental
difference, the turbine has engine sections called:

1\) The inlet section

2\) The compressor section

3\) The combustion section

4\) The exhaust section.

**The practical axial flow turbine engine**

The turbine engine in an airplane has the various sections stacked in a
line from front to back. As a result, the engine body presents less drag
to the airplane as it is flying. The air enters the front of the engine
and passes essentially straight through from front to back. On its way
to the back, the air is compressed by the compressor section. Fuel is
added and burned in the combustion section, then the air is exhausted
through the exit nozzle.

The laws of nature will not let us get something for nothing. The
compressor needs to be driven by something in order to work. Just after
the burner and before the exhaust nozzle, there is a turbine that uses
some of the energy in the discharging air to drive the compressor. There
is a long shaft connecting the turbine to the compressor ahead of it.

*Compressor combustor turbine nozzle*

![](media/image5.jpeg){width="2.7465277777777777in"
height="1.7645833333333334in"}

*Fig 5 showing basic layout of jet propulsion system.*

**Machinery details**

From an outsider\'s view, the flight crew and passengers rarely see the
actual engine. What is seen is a large elliptically-shaped pod hanging
from the wing or attached to the airplane fuselage toward the back of
the airplane. This pod structure is called the nacelle or cowling. The
engine is inside this nacelle.

The first nacelle component that incoming air encounters on its way
through an airplane turbine engine is the inlet cowl. The purpose of the
inlet cowl is to direct the incoming air evenly across the inlet of the
engine. The shape of the interior of the inlet cowl is very carefully
designed to guide this air.

The compressor of an airplane turbine engine has quite a job to do. The
compressor has to take in an enormous volume of air and compress it to
1/10^th^ or 1/15^th^ of the volume it had outside the engine. This
volume of air must be supplied continuously, not in pulses or periodic
bursts.

The compression of this volume of air is accomplished by a rotating disk
containing many airfoils, called blades, set at an angle to the disk
rim. Each blade is close to the shape of a miniature propeller blade,
and the angle at which it is set on the disk rim is called the angle of
attack. This angle of attack is similar to the pitch of a propeller
blade or an airplane wing in flight. As the disk with blades is forced
to rotate by the turbine, each blade accelerates the air, thus pumping
the air behind it. The effect is similar to a household window fan.

![](media/image6.jpeg){width="1.8534722222222222in"
height="2.201388888888889in"}

*Fig 6 showing compressor rotor disk.*

After the air passes through the blades on a disk, the air will be
accelerated rearward and also forced circumferen-tially around in the
direction of the rotating disk. Any tendency for the air to go around in
circles is counterproductive, so this tendency is corrected by putting
another row of airfoils behind the rotating disk. This row is stationary
and its airfoils are at an opposing angle.

What has just been described is a single stage of compression. Each
stage consists of a rotating disk with many blades on the rim, called a
rotor stage, and, behind it, another row of airfoils that is not
rotating, called a stator. Air on the backside of this rotor/stator pair
is accelerated rearward, and any tendency for the air to go around
circumferentially is corrected.

![](media/image7.jpeg){width="2.745138888888889in"
height="1.9618055555555556in"}

*Fig 7 showing 9 stages of a compressor rotor assembly.*

A single stage of compression can achieve perhaps 1.5:1 or 2.5:1
decrease in the air\'s volume. Compression of the air increases the
energy that can be extracted from the air during combustion and exhaust
(which provides the thrust). In order to achieve the 10:1 to 15:1 total
compression needed for the engine to develop adequate power, the engine
is built with many stages of compressors stacked in a line. Depending
upon the engine design, there may be as many as 10 to 15 stages in the
total compressor.

As the air is compressed through the compressor, the air increases in
velocity, temperature, and pressure. Air does not behave the same at
elevated temperatures, pressures, and velocities as it does in the front
of the engine before it is compressed. In particular, this means that
the speed that the compressor rotors must have at the back of the
compressor is different than at the front of the compressor. If we had
only a few stages, this difference could be ignored; but, for 10 to 15
compressor stages, it would not be efficient to have all the stages
rotate at the same speed.

The most common solution to this problem is to break the compressor in
two. This way, the front 4 or 5 stages can rotate at one speed, while
the rear 6 or 7 stages can rotate at a different, higher, speed. To
accomplish this, we also need two separate turbines and two separate
shafts.

![](media/image8.jpeg){width="3.1590277777777778in"
height="1.6708333333333334in"}

*Fig 8 showing layout of a dual rotor airplane turbine engine.*

Most of today\'s turbine engines are dual-rotor engines, meaning there
are two distinct sets of rotating components. The rear compressor, or
high-pressure compressor, is connected by a hollow shaft to a
high-pressure turbine. This is the high rotor. The rotors are sometimes
called spools, such as the \"high spool.\" In this text, we will use the
term rotor. The high rotor is often referred to as N2 for short.

The front compressor, or low-pressure compressor, is in front of the
high-pressure compressor. The turbine that drives the low-pressure
compressor is behind the turbine that drives the high-pressure
compressor. The low-pressure compressor is connected to the low-pressure
turbine by a shaft that goes through the hollow shaft of the high rotor.
The low-pressure rotor is called N1 for short.

The N1 and N2 rotors are not connected mechanically in any way. There is
no gearing between them. As the air flows through the engine, each rotor
is free to operate at its own efficient speed. These speeds are all
quite precise and are carefully calculated by the engineers who designed
the engine. The speed in RPM of each rotor is often displayed on the
engine flight deck and identified by gages or readouts labeled N1 RPM
and N2 RPM. Both rotors have their own redline limits.

In some engine designs, the N1 and N2 rotors may rotate in opposite
directions, or there may be three rotors instead of two. Whether or not
these conditions exist in any particular engine are engineering
decisions and are of no consequence to the pilot.

**The turbofan engine**

A turbofan engine is simply a turbine engine where the first stage
compressor rotor is larger in diameter than the rest of the engine. This
larger stage is called the fan. The air that passes through the fan near
its inner diameter also passes through the remaining compressor stages
in the core of the engine and is further compressed and processed
through the engine cycle. The air that passes through the outer diameter
of the fan rotor does not pass through the core of the engine, but
instead passes along the outside of the engine. This air is called
bypass air, and the ratio of bypass air to core air is called the bypass
ratio.

![](media/image9.jpeg){width="2.747916666666667in"
height="2.328472222222222in"}

*Fig 9 showing schematic of fan jet engine. In this sketch, the fan is
the low-pressure compressor. In some engine designs, there will be a few
stages of low-pressure compressor with the fan. These may be called
booster stages.*

The air accelerated by the fan in a turbofan engine contributes
significantly to the thrust produced by the engine, particularly at low
forward speeds and low altitudes. In large engines, such as the engines
that power the B747, B757, B767, A300, A310, etc., as much as
three-quarters of the thrust delivered by the engine is developed by the
fan.

The fan is not like a propeller. On a propeller, each blade acts like an
airplane wing, developing lift as it rotates. The \"lift\" on a
propeller blade pulls the engine and airplane forward through the air.

In a turbofan engine, thrust is developed by the fan rotor system, which
includes the static structure (fan exit guide vanes) around it. The fan
system acts like the open balloon in our example at the start of this
discussion, and thus pushes the engine, and the airplane along with it,
through the air from the unbalanced forces.

![](media/image10.jpeg){width="2.745833333333333in"
height="2.3354166666666667in"}

*Fig 10 showing schematic of a turboprop. In this configuration, there
are two stages of turbine with a shaft that goes through the engine to a
gearbox which reduces the rotor speed of the propeller.*

What the fan and the propeller do have in common is that the core engine
drives them both.

LESSON SUMMARY

So far we have learned:

1)  Propulsion is created by the unbalance of forces.

2)  A pressure vessel with an open end delivers propulsion due to the
    unbalance of forces.

3)  An airplane propulsion system is a pressure vessel with an open end
    in the back.

4)  An airplane engine provides a constant supply of air for the
    pressure vessel.

5)  An airplane turbine engine operates with the same 4 basic steps as a
    lawnmower or automobile engine.

6)  An airplane turbine engine has sections that perform each of the 4
    basic steps of intake, compression, combustion, and exhaust.

7)  Compression is accomplished by successive stages of rotor/stator
    pairs.

8)  The compressor stages are usually split into low-pressure and
    high-pressure compressor sections.

9)  The low-pressure section can be referred to as N1 and the
    high-pressure section can be referred to as N2.

10) A fan is the first stage of compression where the rotor and its
    mating stator are larger in diameter than the rest of the engine.

    **Chapter 2**

**Engine systems**

From an engineer\'s point of view, the turbofan engine is a finely-tuned
piece of mechanical equipment. In order for the engine to provide
adequate power to the airplane at a weight that the airplane can
accommodate, the engine must operate at the limit of technical
feasibility. At the same time, the engine must provide reliable, safe
and economical operation.

Within the engine, there are systems that keep everything functioning
properly. Most of these systems are transparent to the pilot. For that
reason, this text will not go into deep technical detail. While such
discussion would be appropriate for mechanics training to take care of
the engine, it is the purpose of this text to provide information that
pilots can use in understanding the nature of some engine malfunctions
that may be encountered during flight.

The systems often found associated with the operation of the engine are:

1\) The accessory drive gearbox

2\) The fuel system

3\) The lubrication system

4\) The ignition system

5\) The bleed system

6\) The start system

7\) The anti-ice system.

In addition, there are airplane systems that are powered or driven by
the engine. These systems may include:

1\) The electrical system

2\) The pneumatic system

3\) The hydraulic system

4\) The air conditioning system.

These airplane systems are not associated with continued function of the
engine or any engine malfunctions, so they will not be discussed in this
text. The airplane systems may provide cues for engine malfunctions that
will be discussed in the chapter on engine malfunctions.

**[Accessory drive gearbox]{.underline}**

The accessory drive gearbox is most often attached directly to the
outside cases of the engine at or near the bottom. The accessory drive
gearbox is driven by a shaft that extends directly into the engine and
it is geared to one of the compressor rotors of the engine. It is
usually driven by the high-pressure compressor.

![](media/image11.jpeg){width="2.748611111111111in" height="2.0875in"}

*Fig 11 showing typical accessory drive gearbox.*

The gearbox has attachment pads on it for accessories that need to be
mechanically driven. These accessories include airplane systems, such as
generators for airplane and necessary engine electrical power, and the
hydraulic pump for airplane hydraulic systems. Also attached to the
gearbox are the starter and the fuel pump/fuel control.

**[Fuel system]{.underline}**

The fuel system associated directly with the propulsion system consists
of:

1\) A fuel pump

2\) A fuel control

3\) Fuel manifolds

4\) Fuel nozzles

5\) A fuel filter

6\) Heat exchangers

7\) Drains

8\) A pressurizing and dump valve.

All are external to the engine except the fuel nozzles.

The airplane fuel system supplies pressurized fuel from the main tanks.
The fuel is pressurized by electrically-driven boost pumps in the tanks
and then flows through the spar valve or low pressure (LP) shut-off
valve to the engine LP fuel pump inlet.

The fuel pump is physically mounted on the gearbox. Most engine fuel
pumps have two stages, or, in some engines, there may actually be two
separate pumps. There is an LP stage that increases fuel pressure so
that fuel can be used for servos. At this stage, the fuel is filtered to
remove any debris from the airplane tanks. Following the LP stage, there
is an HP (high-pressure) stage that increases fuel pressure above the
combustor pressure. The HP pump always provides more fuel than the
engine needs to the fuel control, and the fuel control meters the
required amount to the engine and bypasses the rest back to the pump
inlet.

The fuel delivered from the pump is generally used to cool the engine
oil and integral drive generator (IDG) oil on the way to the fuel
control. Some fuel systems also incorporate fuel heaters to prevent ice
crystals accumulating in the fuel control during low-temperature
operation and valves to bypass those heat exchangers depending on
ambient temperatures.

The fuel control is installed on the engine on the accessory gearbox,
directly to the fuel pump, or, if there is an electronic control, to the
engine case. The purpose of the fuel control is to provide the required
amount of fuel to the fuel nozzles at the requested time. The rate at
which fuel is supplied to the nozzles determines the acceleration or
deceleration of the engine.

![](media/image12.jpeg){width="1.6in" height="2.0548611111111112in"}

*Fig 12 characterizing that the fuel control is an \"intelligent\"
component that does the work once the flight crew \"tells it what to
do.\"*

The flight crew sets the power requirements by moving a thrust lever in
the flight deck. When the flight crew adjusts the thrust lever, however,
they are actually \"telling the control\" what power is desired. The
fuel control senses what the engine is doing and automatically meters
the fuel to the fuel nozzles within the engine at the required rate to
achieve the power requested by

the flight crew. A fuel flow meter measures the fuel flow sent to the
engines by the control.

In older engines, the fuel control is hydromechanical, which means that
it operates directly from pressure and mechanical speed physically input
into the control unit.

On newer airplanes, control of the fuel metering is done electronically
by a computer device called by names such as \"EEC\" or \"FADEC.\" EEC
stands for Electronic Engine Control, and FADEC stands for Full
Authority Digital Engine Control. The net result is the same. Electronic
controls have the capability of more precisely metering the fuel and
sensing more engine operating parameters to adjust fuel metering. This
results in greater fuel economy and more reliable service.

The fuel nozzles are deep within the engine in the combustion section
right after the compressor. The fuel nozzles provide a precisely-defined
spray pattern of fuel mist into the combustor for rapid, powerful, and
complete combustion. It is easiest to visualize the fuel nozzle spray
pattern as being similar to that of a showerhead.

The fuel system also includes drains to safely dispose of the fuel in
the manifolds when the engine is shut down, and, in some engines, to
conduct leaked fuel overboard.

**[Lubrication system]{.underline}**

An airplane turbine engine, like any engine, must be lubricated in order
for the rotors to turn easily without generating excessive heat. Each
rotor system in the engine has, as a minimum, a rear and front bearing
to support the rotor. That means that the N1 rotor has two bearings and
the N2 rotor has two bearings for a total of 4 main bearings in the
engine. There are some engines that have intermediate and/or special
bearings; however, the number of bearings in a given engine is usually
of little direct interest to a basic understanding of the engine.

The lubrication system of a turbine engine includes:

1\) An oil pump.

2\) An oil storage tank.

3\) A delivery system to the bearing compartments (oil lines).

4\) Lubricating oil jets within the bearing compartments.

5\) Seals to keep the oil in and air out of the compartments.

6\) A scavenge system to remove oil from the bearing compartment after
the oil has done its job. After the oil is scavenged, it is cooled by
heat exchangers, and filtered.

7\) Oil quantity, pressure, temperature, gages and filter bypass
indications on the flight deck for monitoring of the oil system.

8\) Oil filters.

9\) Heat exchangers. Often, one exchanger serves as both a fuel heater
and an oil cooler.

10\) Chip detectors, usually magnetic, to collect bearing compartment
particles as an indication of bearing compartment distress. Chip
detectors may trigger a flight deck indication or be visually examined
during line maintenance.

11\) Drains to safely dispose of leaked oil overboard.

The gages in item 7 are the window that the flight crew has to monitor
the health of the lubrication system.

**[Ignition system]{.underline}**

The ignition system is a relatively straightforward system. Its purpose
is to provide the spark within the combustion section of the engine so
that, when fuel is delivered to the fuel nozzles, the atomized fuel mist
will ignite and the combustion process will start.

Since all 4 steps of the engine cycle in a turbine engine are
continuous, once the fuel is ignited the combustion process normally
continues until the fuel flow is discontinued during engine shutdown.
This is unlike the situation in a piston engine, where there must be an
ignition spark each time the combustion step occurs in the piston
chamber.

Turbine engines are provided with a provision on the flight deck for
\"continuous ignition.\" When this setting is selected, the ignitor will
produce a spark every few seconds. This provision is included for those
operations or flight phases where, if the combustion process were to
stop for any reason, the loss of power could be serious. With continuous
ignition, combustion will restart automatically, often without the pilot
even noticing that there was an interruption in power.

Some engines, instead of having continuous ignition, monitor the
combustion process and turn the igniters on as required, thus avoiding
the need for continuous ignition.

The ignition system includes:

1\) Igniter boxes which transform low-voltage Alternating Current (AC)
from either a gearbox-mounted alternator or from the airplane into
high-voltage Direct Current (DC).

2\) Cables to connect the igniter boxes to the igniter plugs.

3\) Ignitor plugs.

For redundancy, the ignition system has two igniter boxes and two
igniter plugs per engine. Only one igniter in each engine is required to
light the fuel in the combustor. Some airplanes allow the pilot to
select which igniter is to be used; others use the engine control to
make the selection.

**[Bleed system]{.underline}**

***Stability bleeds***

The compressors of airplane turbine engines are designed to operate most
efficiently at cruise. Without help, these compressors may operate very
poorly or not at all during starting, at very low power, or during rapid
transient power changes, which are conditions when they are not as
efficient. To reduce the workload on the compressor during these
conditions, engines are equipped with bleeds to discharge large volumes
of air from the compressor before it is fully compressed.

The bleed system usually consists of:

1\) Bleed valves.

2\) Solenoids or actuators to open and close the bleed valves.

3\) A control device to signal the valves when to open and close.

4\) Lines to connect the control device to the actuators.

In older engines, a control device measures the pressure across one of
the engine compressors, compares it to the inlet pressure of the engine,
and directs higher-pressure, high-compressor air to an air piston-driven
actuator at the bleed valve to directly close the valve. In newer
engines, the electronic fuel control determines when the bleed valves
open and close.

Generally, all the compressor bleed valves are open during engine start.
Some of the valves close after start and some remain open. Those that
remain open then close during engine acceleration to full power for
takeoff. These valves then remain closed for the duration of the flight.

If, during in-flight operation, the fuel control senses instability in
the compressors, the control may open some of the bleed valves
momentarily. This will most often be completely unnoticed by the flight
crew except for an advisory message on the flight deck display in some
airplane models.

***Cooling/clearance control bleeds***

Air is also extracted from the compressor, or the fan airflow, for
cooling engine components and for accessory cooling in the nacelle. In
some engines, air extracted from the compressor is ducted and directed
onto the engine cases to control the clearance between the rotor blade
tips and the case wall. Cooling the case in this way shrinks the case
closer to the blade tips, improving compression efficiency.

***Service bleeds***

The engines are the primary source of pressurized air to the airplane
for cabin pressurization. In some airplanes, engine bleed air can be
used as an auxiliary power source for back-up hydraulic power
air-motors. Air is taken from the high compressor, before any fuel is
burned in it, so that it is as clean as the outside air. The air is
cooled and filtered before it is delivered to the cabins or used for
auxiliary power.

**[Start system]{.underline}**

When the engine is stationary on the ground, it needs an external source
of power to start the compressor rotating so that it can compress enough
air to get energy from the fuel. If fuel were lit in the combustor of a
completely non-rotating engine, the fuel would puddle and burn without
producing any significant rearward airflow.

A pneumatic starter is mounted on the accessory gearbox, and is powered
by air originating from another engine, from the auxiliary power unit
(APU), or from a ground cart. A start valve controls the input
selection. The starter drives the accessory gearbox, which drives the
high-compressor rotor via the same drive shaft normally used to deliver
power TO the gearbox.

Fuel flow during starting is carefully scheduled to allow for the
compressor\'s poor efficiency at very low RPM, and bleeds are used to
unload the compressor until it can reach a self-sustaining speed. During
some points in a normal engine start, it may even look as if the engine
is not accelerating at all. After the engine reaches the self-sustaining
speed, the starter de-clutches from the accessory gearbox. This is
important, as starters can be damaged with exposure to extended,
high-speed operation. The engine is able to accelerate up to idle thrust
without further assistance from the starter.

The starter can also be used to assist during in-flight restart, if an
engine must be restarted. At higher airspeeds, the engine windmill RPM
may be enough to allow engine starting without use of the pneumatic
starter. The specific Airplane Flight Manual (AFM) should be consulted
regarding the conditions in which to perform an in-flight restart.

**[Anti-ice system]{.underline}**

An airplane turbine engine needs to have some protection against the
formation of ice in the inlet and some method to remove ice if it does
form. The engine is equipped with the capability to take some compressor
air, via a bleed, and duct it to the engine inlet or any other place
where anti-ice protection is necessary. Because the compressor bleed air
is quite hot, it prevents the formation of ice and/or removes
already-formed ice.

On the flight deck, the flight crew has the capability to turn anti-ice
on or off. There is generally no capability to control the amount of
anti-ice delivered; for example, \"high,\" \"medium\" or \"low.\" Such
control is not necessary.

**Chapter 3**

**Engine instrumentation in the flight deck**

Airplanes in service today are equipped with devices available to the
flight crew that provide feedback information about the engine to set
engine power and monitor the condition of the engine. In older
airplanes, these devices were gages on the panel. In newer airplanes,
the airplane is equipped with electronic screens which produce
computer-generated displays that resemble the gages that used to be on
the panel. Whether gages or electronic displays are used, the
information given to the flight crew is the same.

The gages are most useful when considered in context with each other,
rather than considering one gage in isolation.

What follows is a brief description of the gages and what information
they provide.

![](media/image13.jpeg){width="0.9583333333333334in"
height="0.9701388888888889in"}

**[Engine Pressure Ratio or EPR.]{.underline}** Engine pressure ratio is
a measure of thrust provided by the engine. EPR indicators provide the
ratio of the pressure of the air as it comes out of the turbine to the
pressure of the air as it enters the compressor. EPR is a certified
thrust-setting parameter. Some engine manufacturers recommend that
engine power management be performed by reference to EPR.

A low EPR reading may be caused by engine rollback or flameout, or
internal damage such as an LP turbine failure. Rapid EPR fluctuations
may be caused by engine operational instability, such as surge, or
rapidly-changing external conditions, such as inclement weather or bird
ingestion. Unexpectedly high EPR may indicate a fuel control
malfunction, or malfunction or clogging of the inlet air pressure
probes.

![](media/image14.jpeg){width="0.9569444444444445in"
height="0.9465277777777777in"}

[**Rotor RPM**.]{.underline} On an airplane equipped with a
multiple-rotor turbine engine, there will be a rotor speed indication
for each rotor. The N1 gage will provide the rotor speed of the
low-pressure rotor and the N2 (or N3 for a 3-rotor engine) gage will
provide the rotor speed of the high-pressure rotor. N1 is a certified
thrust-setting parameter.

The units of rotor speed are Revolutions Per Minute or RPM, but rotor
speed is indicated as a non-dimensional ratio -- that of engine rotor
speed as compared to some nominal 100% speed representing a high-power
condition (which is not necessarily the maximum permissible speed).
Engine operating manuals specify a maximum operational limit RPM or
redline RPM that will generally be greater than 100 percent.

Low N1 may indicate engine rollback or flameout, or severe damage such
as LP turbine failure. Rapid N1 fluctuations may be caused by engine
operational instability such as surge. Higher rotor speeds will be
required at high altitudes to achieve takeoff-rated thrust. Unexpectedly
high N1 may indicate a fuel control malfunction.

N2 is used for limit monitoring and condition monitoring. On older
engines, it is also used to monitor the progress of engine starting and
to select the appropriate time to start fuel flow to the engine.

![](media/image15.jpeg){width="0.9569444444444445in"
height="0.9465277777777777in"}

**[Exhaust Gas Temperature or EGT.]{.underline}** Exhaust gas
temperature is a measure of the temperature of the gas exiting the rear
of the engine. It is measured at some location in the turbine. Since the
exact location varies according to engine model, EGT should not be
compared between engine models. Often, there are many sensors at the
exit of the turbine to monitor EGT. The indicator on the flight deck
displays the average of all the sensors.

High EGT can be an indication of degraded engine performance.
Deteriorated engines will be especially likely to have high EGT during
takeoff.

EGT is also used to monitor engine health and mechanical integrity.
Excessive EGT is a key indicator of engine stall, of difficulty in
engine starting, of a major bleed air leak, and of any other situation
where the turbine is not extracting enough work from the air as it moves
aft (such as severe engine damage).

There is an operational limit for EGT, since excessive EGT will result
in turbine damage. Operational limits for EGT are often classified as
time-at-temperature.

![](media/image16.jpeg){width="0.9597222222222223in"
height="0.9465277777777777in"}

**[Fuel Flow indicator.]{.underline}** The fuel flow indicator shows the
fuel flow in pounds (or kilograms) per hour as supplied to the fuel
nozzles. Fuel flow is of fundamental interest for monitoring in-flight
fuel consumption, for checking engine performance, and for in-flight
cruise control.

High fuel flow may indicate a significant leak between the fuel control
and fuel nozzles, particularly if rotor speeds or EPR appear normal or
low.

![](media/image17.jpeg){width="0.9631944444444445in"
height="0.9798611111111111in"}

**[Oil Pressure Indicator.]{.underline}** The oil pressure indicator
shows the pressure of the oil as it comes out of the oil pump. In some
cases, the oil pressure reading system takes the bearing compartment
background pressure, called breather pressure, into account so that the
gage reading reflects the actual pressure of the oil as it is delivered
to the bearing compartments. Oil system parameters historically give
false indications of a problem as frequently as the oil system has a
genuine problem, so crosschecking with the other oil system indications
is advisable.

Low oil pressure may result from pump failure, from a leak allowing the
oil system to run dry, from a bearing or gearbox failure, or from an
indication system failure. High oil pressure may be observed during
extremely low temperature operations, when oil viscosity is at a
maximum.

**[Low Oil Pressure Caution.]{.underline}** Generally, if the oil
pressure falls below a given threshold level, an indication light or
message is provided to draw attention to the situation.

![](media/image18.jpeg){width="0.9597222222222223in"
height="0.9402777777777778in"}

**[Oil Temperature Indicator.]{.underline}** The Oil temperature
indicator shows the oil temperature at some location in the lubrication
circuit, although this location differs between engine models.

Elevated oil temperatures indicate some unwanted source of heat in the
system, such as a bearing failure, sump fire or unintended leakage of
high temperature air into the scavenge system. High oil temperature may
also result from a malfunction of the engine oil cooler, or of the
valves scheduling fluid flow through the cooler.

**[Oil Quantity Indicator.]{.underline}** The oil quantity indication
monitors the amount of oil in the tank. This can be expected to vary
with power setting, since the amount of oil in the sumps is a function
of rotor speed.

A steady decrease in oil quantity may indicate an oil leak. There is
likely to still be some usable oil in the tank even after the oil
quantity gage reads zero, but the oil supply will be near exhaustion and
a low pressure indication will soon be seen. A large increase in the oil
quantity may be due to fuel leaking into the oil system, and should be
investigated before the next flight. Flight crews should be especially
vigilant to check other oil system indications before taking action on
an engine in-flight solely on the basis of low oil quantity.

**[Oil Filter Bypass Indication.]{.underline}** If the oil filter
becomes clogged with debris (either from contamination by foreign
material or debris from a bearing failure), the pressure drop across the
filter will rise to the point where the oil bypasses the filter. This is
announced to the pilot via the oil filter impending bypass indication.
This indication may go away if thrust is reduced (because oil flow
through the filter and pressure drop across the filter are reduced).

**[Fuel Filter Impending Bypass.]{.underline}** If the fuel filter at
the engine fuel inlet becomes clogged, an impending bypass indication
will alert the crew for a short while before the filter actually goes
into bypass.

**[Fuel Heat Indication.]{.underline}** The fuel heat indicator
registers when the fuel heat is on. Fuel heat indicators are not needed
for engines where fuel heating is passively combined with oil cooling,
and no valves or controls are involved.

**[Engine Starter Indication.]{.underline}** During assisted starting,
the start valve will be indicated open until starter disconnect. The
position of the start switch shows the starter status (running or
disconnected). If the starter does not disconnect once the engine
reaches idle,

or if it disconnects but the starter air valve remains open, the starter
will fail when the engine is at high power, potentially damaging other
systems. More recent engine installations may also have advisory or
status messages associated with engine starting.

**[Vibration Indication.]{.underline}** A vibration gage indicates the
amount of vibration measured on the engine LP rotor and/or HP rotor.
Vibration is displayed in non-dimensional units, and is used for
condition monitoring, identification of the affected engine after
foreign object ingestion, and detection of fan unbalance due to icing.
The level of vibration will change with engine speed.

**[Powerplant Ice Protection Indication.]{.underline}** If anti-icing is
selected, an indication is provided (such as wing anti-ice or nacelle
anti-ice).

**[Thrust Reverser Indication.]{.underline}** Typically, dedicated
thrust reverser indications are provided to show thrust reverser state:
deployed, in transit, and/or fault indications and messages. The exact
indications are installation-specific, and further details may be
obtained from the airplane flight or operations manual.

**[Fire Warning Indicators.]{.underline}** Each engine has a dedicated
fire warning indication, which may cover multiple fire zones and may
address lesser degrees of high undercowl temperature (using messages
such as "Engine Overheat").

![](media/image19.jpeg){width="0.9666666666666667in"
height="0.9465277777777777in"}

**[Fuel Inlet Pressure Indicator.]{.underline}** The fuel inlet pressure
indicator measures the pressure at the inlet to the engine-driven fuel
pump. This pressure will be the pressure of the fuel supplied from the
airplane.

![](media/image20.jpeg){width="0.9534722222222223in"
height="0.9402777777777778in"}

**[Air Temperature Indicator.]{.underline}** This gage is not an actual
engine gage, but rather is an airplane gage. The air temperature
indicator provides the temperature of the air outside the airplane. This
temperature may be recorded from specific locations and, therefore, the
actual value may mean different things depending upon the particular
airplane. This temperature typically is used to help select EPR in those
engines where thrust is set by EPR.

In addition to the above indications, recently-designed airplanes have a
wide variety of caution, advisory and status messages that may be
displayed in the event of an engine malfunction or abnormal operation.
Since these are specific to each particular airplane design, they cannot
be addressed here; reference to the appropriate airplane flight or
operations manual will provide further information.

**Chapter 4**

**Engine Malfunctions**

To provide effective understanding of and preparation for the correct
responses to engine in-flight malfunctions, this chapter will describe
turbofan engine malfunctions and their consequences in a manner that is
applicable to almost all modern turbofan-powered airplanes. These
descriptions, however, do not supersede or replace the specific
instructions that are provided in the Airplane Flight Manual and
appropriate checklists.

**[Compressor surge]{.underline}**

It is most important to provide an understanding of compressor surge. In
modern turbofan engines, compressor surge is a rare event. If a
compressor surge (sometimes called a compressor stall) occurs during
high power at takeoff, the flight crew will hear a very loud bang, which
will be accompanied by yaw and vibration. The bang will likely be far
beyond any engine noise, or other sound, the crew may have previously
experienced in service.

Compressor surge has been mistaken for blown tires or a bomb in the
airplane. The flight crew may be quite startled by the bang, and, in
many cases, this has led to a rejected takeoff above V1. These
high-speed rejected takeoffs have sometimes resulted in injuries, loss
of the airplane, and even passenger fatalities.

The actual cause of the loud bang should make no difference to the
flight crew's

first response, which should be to maintain control of the airplane and,
in particular, continue the takeoff if the event occurs after V1.
Continuing the takeoff is the proper response to a tire failure
occurring after V1, and history has shown that bombs are not a threat
during the takeoff roll -- they are generally set to detonate at
altitude.

A surge from a turbofan engine is the result of instability of the
engine\'s operating cycle. Compressor surge may be caused by engine
deterioration, it may be the result of ingestion of birds or ice, or it
may be the final sound from a "severe engine damage" type of failure. As
we learned in Chapter 1, the operating cycle of the turbine engine
consists of intake, compression, ignition, and exhaust, which occur
simultaneously in different places in the engine. The part of the cycle
susceptible to instability is the compression phase.

In a turbine engine, compression is accomplished aerodynamically as the
air passes through the stages of the compressor, rather than by
confinement, as is the case in a piston engine. The air flowing over the
compressor airfoils can stall just as the air over the wing of an
airplane can. When this airfoil stall occurs, the passage of air through
the compressor becomes unstable and the compressor can no longer
compress the incoming air. The high-pressure air behind the stall
further back in the engine escapes forward through the compressor and
out the inlet.

![](media/image21.jpeg){width="2.747916666666667in"
height="2.189583333333333in"}

This escape is sudden, rapid and often quite audible as a loud bang
similar to an explosion. Engine surge can be accompanied by visible
flames forward out the inlet and rearward out the tailpipe. Instruments
may show high EGT and EPR or rotor speed changes, but, in many stalls,
the event is over so quickly that the instruments do not have time to
respond.

Once the air from within the engine escapes, the reason (reasons) for
the instability may self-correct and the compression process may
re-establish itself. A single surge and recovery will occur quite
rapidly, usually within fractions of a second. Depending on the reason
for the cause of the compressor instability, an engine might experience:

1\) A single self-recovering surge

2\) Multiple surges prior to self-recovery

3\) Multiple surges requiring pilot action in order to recover

4\) A non-recoverable surge.

For complete, detailed procedures, flight crews must follow the
appropriate checklists and emergency procedures detailed in their
specific Airplane Flight Manual. In general, however, during a single
self-recovering surge, the cockpit engine indications may fluctuate
slightly and briefly. The flight crew may not

notice the fluctuation. (Some of the more recent engines may even have
fuel-flow logic that helps the engine self-recover from a surge without
crew intervention. The stall may go completely unnoticed, or it may be
annunciated to the crew -- for information only -- via EICAS messages.)
Alternatively, the engine may surge two or three times before full
self-recovery. When this happens, there is likely to be cockpit engine
instrumentation shifts of sufficient magnitude and duration to be
noticed by the flight crew. If the engine does not recover automatically
from the surge, it may surge continually until the pilot takes action to
stop the process. The desired pilot action is to retard the thrust lever
until the engine recovers. The flight crew should then SLOWLY re-advance
the thrust lever. Occasionally, an engine may surge only once but still
not self-recover.

The actual cause for the compressor surge is often complex and may or
may not result from severe engine damage. Rarely does a single
compressor surge CAUSE severe engine damage, but sustained surging will
eventually over-heat the turbine, as too much fuel is being provided for
the volume of air that is reaching the combustor. Compressor blades may
also be damaged and fail as a result of repeated violent surges; this
will rapidly result in an engine which cannot run at any power setting.

Additional information is provided below regarding single recoverable
surge, self-recoverable after multiple surges, surge requiring flight
crew action, and non-recoverable surge. In severe cases, the noise,
vibration and aerodynamic forces can be very distracting. It may be
difficult for the flight crew to remember that their most important task
is to fly the airplane.

***Single self-recoverable surge***

The flight crew hears a very loud bang or double bang. The instruments
will fluctuate quickly, but, unless someone was looking at the engine
gage at the time of the surge, the fluctuation might not be noticed.

For example: During the surge event, Engine Pressure Ratio (EPR) can
drop from takeoff (T/O) to 1.05 in 0.2 seconds. EPR can then vary from
1.1 to 1.05 at 0.2-second intervals two or three times. The low rotor
speed (N1) can drop 16% in the first 0.2 seconds, then another 15% in
the next 0.3 seconds. After recovery, EPR and N1 should return to
pre-surge values along the normal acceleration schedule for the engine.

***Multiple surge followed by self-recovery***

Depending on the cause and conditions, the engine may surge multiple
times, with each bang being separated by a couple of seconds. Since each
bang usually represents a surge event as described above, the flight
crew may detect the \"single surge\" described above for two seconds,
then the engine will return to 98% of the pre-surge power for a few
seconds. This cycle may repeat two or three times. During the surge and
recovery process, there will likely be some rise in EGT.

For example: EPR may fluctuate between 1.6 and 1.3, Exhaust Gas
Temperature (EGT) may rise 5 degrees C/second, N1 may fluctuate between
103% and 95%, and fuel flow may drop 2% with no change in thrust lever
position. After 10 seconds, the engine gages should return to pre-surge
values.

***Surge recoverable after flight crew action***

When surges occur as described in the previous paragraph, but do not
stop, flight crew action is required to stabilize the engine. The flight
crew will notice the fluctuations described in "recoverable after two or
three bangs," but the fluctuations and bangs will continue until the
flight crew retards the thrust lever to idle. After the flight crew
retards the thrust lever to idle, the engine parameters should decay to
match thrust lever position. After the engine reaches idle, it may be
re-accelerated back to power. If, upon re-advancing to high power, the
engine surges again, the engine may be left at idle, or left at some
intermediate power, or shutdown, according to the checklists applicable
for the airplane. If the flight crew takes no action to stabilize the
engine under these circumstances, the engine will continue to surge and
may experience progressive secondary damage to the point where it fails
completely.

***Non-recoverable surge***

When a compressor surge is not recoverable, there will be a single bang
and the engine will decelerate to zero power as if the fuel had been
chopped. This type of compressor surge can accompany a severe engine
damage malfunction. It can also occur without any engine damage at all.

EPR can drop at a rate of .34/sec and EGT rise at a rate of 15 degrees
C/sec, continuing for 8 seconds (peaking) after the thrust lever is
pulled back to idle. N1 and N2 should decay at a rate consistent with
shutting off the fuel, with fuel flow dropping to 25% of its pre-surge
value in 2 seconds, tapering to 10% over the next 6 seconds.

**[Flameout]{.underline}**

A flameout is a condition where the combustion process within the burner
has stopped. A flameout will be accompanied by a drop in EGT, in engine
core speed and in engine pressure ratio. Once the engine speed drops
below idle, there may be other symptoms, such as low oil pressure
warnings and electrical generators dropping off line -- in fact, many
flameouts from low initial power settings are first noticed when the
generators drop off line and may be initially mistaken for electrical
problems. The flameout may result from the engine running out of fuel,
severe inclement weather, a volcanic ash encounter, a control system
malfunction, or unstable engine operation (such as a compressor stall).
Multiple engine flameouts may result in a wide variety of flight deck
symptoms as engine inputs are lost from electrical, pneumatic and
hydraulic systems. These situations have resulted in pilots
troubleshooting the airplane systems without recognizing and fixing the
root cause -- no engine power. Some airplanes have dedicated EICAS/ECAM
messages to alert the flight crew to an engine rolling back below idle
speed in flight; generally, an ENG FAIL or ENG THRUST message.

A flameout at take-off power is unusual -- only about 10% of flameouts
are at takeoff power. Flameouts occur most frequently from intermediate
or low power settings, such as cruise and descent. During these flight
regimes, it is likely that the autopilot is in use. The autopilot will
compensate for the asymmetrical thrust up to its limits and may then
disconnect. Autopilot disconnect must then be accompanied by prompt,
appropriate control inputs from the flight crew if the airplane is to
maintain a normal attitude. If no external visual references are
available, such as when flying over the ocean at night or in IMC, the
likelihood of an upset increases. This condition of low-power engine
loss with the autopilot on has caused several aircraft upsets, some of
which were not recoverable. Flight control displacement may be the only
obvious indication. Vigilance is required to detect these stealthy
engine failures and to maintain a safe flight attitude while the
situation is still recoverable.

![](media/image22.jpeg){width="1.5479166666666666in"
height="1.9256944444444444in"}

Once the fuel supply has been restored to the engine, the engine may be
restarted in the manner prescribed by the applicable Airplane Flight or
Operating Manual. Satisfactory engine restart should be confirmed by
reference to all primary parameters -- using only N1, for instance, has
led to confusion during some in-flight restarts. At some flight
conditions, N1 may be very similar for a windmilling engine and an
engine running at flight idle.

**[Fire]{.underline}**

![](media/image23.jpeg){width="1.3993055555555556in"
height="1.3722222222222222in"}

Engine fire almost always refers to a fire outside the engine but within
the nacelle. A fire in the vicinity of the engine should be annunciated
to the flight crew by a fire warning in the flight deck. It is unlikely
that the flight crew will see, hear, or immediately smell an engine
fire. Sometimes, flight crews are advised of a fire by communication
with the control tower.

It is important to know that, given a fire in the nacelle, there is
adequate time to make the first priority \"fly the airplane\" before
attending to the fire. It has been shown that, even in incidents of fire
indication immediately after takeoff, there is adequate time to continue
climb to a safe altitude before attending to the engine. There may be
economic damage to the nacelle, but the first priority of the flight
crew should be to ensure the airplane continues in safe flight.

Flight crews should regard any fire warning as a fire, even if the
indication goes away when the thrust lever is retarded to idle. The
indication might be the result of pneumatic leaks of hot air into the
nacelle. The fire indication could also be from a fire that is small or
sheltered from the detector so that the fire is not apparent at low
power. Fire indications may also result from faulty detection systems.
Some fire detectors allow identification of a false indication (testing
the fire loops), which may avoid the need for an IFSD. There have been
times when the control tower has mistakenly reported the flames
associated with a compressor surge as an engine \"fire.\"

In the event of a fire warning annunciation, the flight crew must refer
to the checklists and procedures specific to the airplane being flown.
In general, once the decision is made that a fire exists and the
aircraft is stabilized, engine shutdown should be immediately
accomplished by shutting off fuel to the engine, both at the engine fuel
control shutoff and the wing/pylon spar valve. All bleed air,
electrical, and hydraulics from the affected engine will be disconnected
or isolated from the airplane systems to prevent any fire from spreading
to or contaminating associated airplane systems. This is accomplished by
one common engine \"fire handle.\" This controls the fire by greatly
reducing the fuel available for combustion, by reducing the availability
of pressurized air to any sump fire, by temporarily denying air to the
fire through the discharge of fire extinguishant, and by removing
sources of re-ignition, such as live electrical wiring and hot casings.
It should be noted that some of these control measures may be less
effective if the fire is the result of severe damage -- the fire may
take slightly longer to be extinguished in these circumstances. In the
event of a shut down after an in-flight engine fire, there should be no
attempt to restart the engine unless it is critical for continued safe
flight, as the fire is likely to re-ignite once the engine is restarted.

# [Tailpipe Fires]{.underline}

One of the most alarming events for passengers, flight attendants,
ground personnel and even air traffic control (ATC) to witness is a
tailpipe fire. Fuel may puddle in the turbine casings and exhaust during
start-up or shutdown, and then ignite. This can result in a
highly-visible jet of flame out of the back of the engine, which may be
tens of feet long. Passengers have initiated emergency evacuations in
these instances, leading to serious injuries.

There may be no indication of an anomaly to the flight crew until the
cabin crew or control tower draws attention to the problem. They are
likely to describe it as an "Engine Fire," but a tailpipe fire will NOT
result in a fire warning on the flight deck.

If notified of an engine fire without any indications in the cockpit,
the flight crew should accomplish the tailpipe fire procedure. It will
include motoring the engine to help extinguish the flames, while most
other engine abnormal procedures will not.

Since the fire is burning within the turbine casing and exhaust nozzle,
pulling the fire handle to discharge extinguishant to the space between
casings and cowls will be ineffective. Pulling the fire handle may also
make it impossible to dry motor the engine, which is the quickest way of
extinguishing most tailpipe fires.

# [Hot starts]{.underline} 

During engine start, the compressor is very inefficient, as already
discussed. If the engine experiences more than the usual difficulty
accelerating (due to such problems as early starter cut-out, fuel
mis-scheduling, or strong tailwinds), the engine may spend a
considerable time at very low RPM (sub-idle). Normal engine cooling
flows will not be effective during sub-idle operation, and turbine
temperatures may appear relatively high. This is known as a hot start
(or, if the engine completely stops accelerating toward idle, a hung
start). The AFM indicates acceptable time/temperature limits for EGT
during a hot start. More recent, FADEC-controlled engines may
incorporate auto-start logic to detect and manage a hot start.

**[Bird ingestion/FOD]{.underline}**

Airplane engines ingest birds most often in the vicinity of airports,
either during takeoff or during landing. Encounters with birds occur
during both daytime and nighttime flights.

By far, most bird encounters do not affect the safe outcome of a flight.
In more than half of the bird ingestions into engines, the flight crew
is not even aware that the ingestion took place.

When an ingestion involves a large bird, the flight crew may notice a
thud, bang or vibration. If the bird enters the engine core, there may
be a smell of burnt flesh in the flight deck or passenger cabin from the
bleed air.

Bird strikes can damage an engine. The photo on the next page shows fan
blades bent due to the ingestion of a bird. The engine continued to
produce thrust with this level of damage. Foreign Object Damage (FOD)
from other sources, such as tire fragments, runway debris or animals,
may also be encountered, with similar results.

Bird ingestion can also result in an engine surge. The surge may have
any of the characteristics listed in the surge section. The engine may
surge once and recover; it may surge continuously until the flight crew
takes action; or it may surge once and not recover, resulting in the
loss of power from that engine. Bird ingestion can result in the
fracture of one or more fan blades, in which case, the engine will
likely surge once and not recover.

![](media/image24.jpeg){width="2.75in" height="2.323611111111111in"}

*Fig 13 showing fan blades bent by encounter with a bird.*

Regardless of the fact that a bird ingestion has resulted in an engine
surge, the first priority task of the flight crew is to \"fly the
airplane.\" Once the airplane is in stable flight at a safe altitude,
the appropriate procedures in the applicable Airplane Flight Manual can
be accomplished.

In rare cases, multiple engines can ingest medium or large birds. In the
event of suspected multiple-engine damage, taking action to stabilize
the engines becomes a much higher priority than if only one engine is
involved -- but it is still essential to control the airplane first.

**[Severe engine damage]{.underline}**

Severe engine damage may be difficult to define. From the viewpoint of
the flight crew, severe engine damage is

![](media/image25.jpeg){width="2.7493055555555554in"
height="1.8909722222222223in"}

mechanical damage to the engine that looks \"bad and ugly.\" To the
manufacturers of the engine and the airplane, severe engine damage may
involve symptoms as obvious as large holes in the engine cases and
nacelle or as subtle as the non-response of the engine to thrust lever
movement.

It is important for flight crews to know that severe engine damage may
be accompanied by symptoms such as fire warning (from leaked hot air) or
engine surge because the compressor stages that hold back the pressure
may not be intact or in working order due to the engine damage.

In this case, the symptoms of severe engine damage will be the same as a
surge without recovery. There will be a loud noise. EPR will drop
quickly; N1, N2 and fuel flow will drop. EGT may rise momentarily. There
will be a loss of power to the airplane as a result of the severe engine
damage. It is not important to initially distinguish between a
non-recoverable surge with or without severe engine damage, or between a
fire and a fire warning with severe engine damage. The priority of the
flight crew still remains \"fly the airplane.\" Once the airplane is
stabilized, the flight crew can diagnose the situation.

# [Engine Seizure]{.underline}

Engine seizure describes a situation where the engine rotors stop
turning in flight, perhaps very suddenly. The static and rotating parts
lock up against each other, bringing the rotor to a halt. In practice,
this is only likely to occur at low rotor RPM after an engine shutdown,
and virtually never occurs for the fan of a large engine -- the fan has
too much inertia, and the rotor is being pushed around by ram air too
forcefully to be stopped by the static structure. The HP rotor is more
likely to seize after an in-flight shutdown if the nature of the engine
malfunction is mechanical damage within the HP system. Should the LP
rotor seize, there will be some perceptible drag for which the flight
crew must compensate; however, if the HP rotor seizes, there will be
negligible effect upon airplane handling.

Seizure cannot occur without being caused by very severe engine damage,
to the point where the vanes and blades of the compressor and turbine
are mostly destroyed. This is not an instantaneous process -- there is a
great deal of inertia in the turning rotor compared to the energy needed
to break interlocking rotating and static components.

Once the airplane has landed, and the rotor is no longer being driven by
ram air, seizure is frequently observed after severe damage.

Symptoms of engine seizure in flight may include vibration, zero rotor
speed, mild airplane yaw, and possibly unusual noises (in the event of
fan seizure). There may be an increased fuel flow in the remaining
engines due to aircraft automatic compensations; no special action is
needed other than that which is appropriate to the severe engine damage
type failure.

# [Engine Separation]{.underline}

Engine separation is an extremely rare event. It will be accompanied by
loss of all primary and secondary parameters for the affected engine,
noises, and airplane yaw (especially at high power settings). Separation
is most likely to occur during take-off/climb-out or the landing roll.
Airplane handling may be affected. It is important to use the fire
handle to close the spar valve and prevent a massive overboard fuel
leak; refer to the airplane flight or operations manual for specific
procedures.

# 

# [Fuel System Problems]{.underline}

## **Leaks**

Major leaks in the fuel system are a concern to the flight crew because
they may result in engine fire, or, eventually, in fuel exhaustion. A
very large leak can produce engine flameout.

Engine instruments will only indicate a leak if it is downstream of the
fuel flowmeter. A leak between the tanks and the fuel flowmeter can only
be recognized by comparing fuel usage between engines, by comparing
actual usage to planned usage, or by visual inspection for fuel flowing
out of the pylon or cowlings. Eventually, the leak may result in tank
imbalance.

In the event of a major leak, the crew should consider whether the leak
needs to be isolated to prevent fuel exhaustion.

It should be noted that the likelihood of fire resulting from such a
leak is greater at low altitude or when the airplane is stationary; even
if no fire is observed in flight, it is advisable for emergency services
to be available upon landing.

## **Inability to shutdown Engine**

If the engine fuel shut-off valve malfunctions, it may not be possible
to shut the engine down by the normal procedure, since the engine
continues to run after the fuel switch is moved to the cutoff position.
Closing the spar valve by pulling the fire handle will ensure that the
engine shuts down as soon as it has used up the fuel in the line from
the spar valve to the fuel pump inlet. This may take a couple of
minutes.

## **Fuel filter Clogging**

Fuel filter clogging can result from the failure of one of the fuel tank
boost pumps (the pump generates debris which is swept downstream to the
fuel filter), from severe contamination of the fuel tanks during
maintenance (scraps of rag, sealant, etc., that are swept downstream to
the fuel filter), or, more seriously, from gross contamination of the
fuel. Fuel filter clogging will usually be seen at high power settings,
when the fuel flow through the filter (and the sensed pressure drop
across the filter) is greatest. If multiple fuel filter bypass
indications are seen, the fuel may be heavily contaminated with water,
rust, algae, etc. Once the filters bypass and the contaminant goes
straight into the engine fuel system, the engine fuel control may no
longer operate as intended. There is potential for multiple-engine
flameout. The Airplane Flight or Operating Manual provides the necessary
guidance.

**[Oil System Problems]{.underline}**

The engine oil system has a relatively large number of indicated
parameters required by the regulations (pressure, temperature, quantity,
filter clogging). Many of the sensors used are subject to giving false
indications, especially on earlier engine models. Multiple abnormal
system indications confirm a genuine failure; a single abnormal
indication may or may not be a valid indication of failure.

There is considerable variation between failure progressions in the oil
system, so the symptoms given below may vary from case to case.

Oil system problems may appear at any flight phase, and generally
progress gradually. They may eventually lead to severe engine damage if
the engine is not shut down.

## **Leaks**

Leaks will produce a sustained reduction in oil quantity, down to zero
(though there will still be some usable oil in the system at this
point). Once the oil is completely exhausted, oil pressure will drop to
zero, followed by the low oil pressure light. There have been cases
where maintenance error caused leaks on multiple engines; it is
therefore advisable to monitor oil quantity carefully on the good
engines as well. Rapid change in the oil quantity after thrust lever
movement may not indicate a leak -- it may be due to oil "gulping" or
"hiding" as more oil flows into the sumps.

***Bearing failures***

Bearing failures will be accompanied by an increase in oil temperature
and indicated vibration. Audible noises and filter clog messages may
follow; if the failure progresses to severe engine damage, it may be
accompanied by low oil quantity and pressure indications.

## **Oil pump failures**

Oil pump failure will be accompanied by low indicated oil pressure and a
low oil pressure light, or by an oil filter clog message.

## **Contamination**

Contamination of the oil system -- by carbon deposits, cotton waste,
improper fluids, etc. -- will generally lead to an oil filter clog
indication or an impending bypass indication. This indication may
disappear if thrust is reduced, since the oil flow and pressure drop
across the filter will also drop.

# [No Thrust Lever Response]{.underline}

A "No Thrust Lever Response" type of malfunction is more subtle than the
other malfunctions previously discussed, so subtle that it can be
completely overlooked, with potentially serious consequences to the
airplane.

If an engine slowly loses power -- or if, when the thrust lever is
moved, the engine does not respond -- the airplane will experience
asymmetric thrust. This may be partly concealed by the autopilot's
efforts to maintain the required flight condition.

As is the case with flameout, if no external visual references are
available, such as when flying over the ocean at night or in IMC,
asymmetric thrust may persist for some time without the flight crew
recognizing or correcting it. In several cases, this has led to airplane
upset, which was not always recoverable. As stated, this condition is
subtle and not easy to detect.

Symptoms may include:

-   Multiple system problems such as generators dropping off-line or low
    engine oil pressure.

-   Unexplained airplane attitude changes.

-   Large unexplained flight control surface deflections (autopilot on)
    or the need for large flight control inputs without apparent cause
    (autopilot off).

-   Significant differences between primary parameters from one engine
    to the next.

If asymmetric thrust is suspected, the first response must be to make
the appropriate trim or rudder input. Disconnecting the autopilot
without first performing the appropriate control input or trim may
result in a rapid roll maneuver.

# [Reverser malfunctions]{.underline}

Generally, thrust reverser malfunctions are limited to failure
conditions where the reverser system fails to deploy when commanded and
fails to stow when commanded. Failure to deploy or to stow during the
landing roll will result in significant asymmetric thrust, and may
require a rapid response to maintain directional control of the
airplane.

Uncommanded deployments of modern thrust reverser systems have occurred
and have led to Airworthiness Directives to add additional locking
systems to the reverser. As a consequence of this action, the
probability of inadvertent deployment is extremely low. The airplane
flight or operations manual provides the necessary system information
and type of annunciations provided by the airplane type.

# [No Starter Cutout]{.underline}

Generally, this condition exists when the start selector remains in the
start position or the engine start valve is open when commanded closed.
Since the starter is intended only to operate at low speeds for a few
minutes at a time, the starter may fail completely (burst) and cause
further engine damage if the starter does not cut out.

# [Vibration]{.underline}

Vibration is a symptom of a wide variety of engine conditions, ranging
from very benign to serious. The following are some causes of tactile or
indicated vibration:

-   Fan unbalance at assembly

-   Fan blade friction or shingling

-   Water accumulation in the fan rotor

-   Blade icing

-   Bird ingestion/FOD

-   Bearing failure

-   Blade distortion or failure

-   Excessive fan rotor system tip clearances.

It is not easy to identify the cause of the vibration in the absence of
other unusual indications. Although the vibration from some failures may
feel very severe on the flight deck, it will not damage the airplane.
There is no need to take action based on vibration indication alone, but
it can be very valuable in confirming a problem identified by other
means.

Engine vibration may be caused by fan unbalance (ice buildup, fan blade
material loss due to ingested material, or fan blade distortion due to
foreign object damage) or by an internal engine failure. Reference to
other engine parameters will help to establish whether a failure exists.

Vibration felt on the flight deck may not be indicated on instruments.
For some engine failures, severe vibration may be experienced on the
flight deck either during an engine failure or possibly after the engine
has been shut down, making instruments difficult to read. This large
amplitude vibration is caused by the unbalanced fan windmilling close to
the airframe natural frequency, which may amplify the vibration.
Changing airspeed and/or altitude will change the fan windmill speed,
and an airplane speed may be found where there will be much less
vibration. Meanwhile, there is no risk of airplane structural failure
due to vibratory engine loads.

# Wrap-up

# The tabulation of engine conditions and their symptoms below shows that many failures have similar symptoms and that it may not be practicable to diagnose the nature of the engine problem from flight deck instrumentation. However, it is not necessary to understand exactly what is wrong with the engine -- selecting the "wrong" checklist may cause some further economic damage to the engine, but, provided action is taken with the correct engine, and airplane control is kept as the first priority, the airplane will still be safe.

<table style="width:100%;">
<colgroup>
<col style="width: 27%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 9%" />
<col style="width: 6%" />
</colgroup>
<tbody>
<tr class="odd">
<td><h1 id="section-1"></h1></td>
<td><h1 id="engine-separation-1"> Engine separation</h1></td>
<td><h1 id="severe-damage">Severe damage</h1></td>
<td><h1 id="surge"> Surge</h1></td>
<td><h1 id="bird-ingestionfod"> Bird ingestion/FOD</h1></td>
<td><h1 id="seizure">Seizure </h1></td>
<td><h1 id="flameout"> Flameout</h1></td>
<td><h1 id="fuel-control-problems"> Fuel control problems</h1></td>
<td><h1 id="fire"> Fire</h1></td>
<td><h1 id="tailpipe-fires-1"> Tailpipe fires</h1></td>
<td><h1 id="hot-start">Hot start</h1></td>
<td><h1 id="icing"> Icing</h1></td>
<td><h1 id="reverser-inadvertent"> Reverser inadvertent</h1>
<h1 id="deploy"> deploy</h1></td>
<td><h1 id="fuel-leak">Fuel leak</h1></td>
</tr>
<tr class="even">
<td><h1 id="bang">Bang</h1></td>
<td><h1 id="o">O</h1></td>
<td><h1 id="x">X</h1></td>
<td><h1 id="x-1">X</h1></td>
<td><h1 id="o-1">O</h1></td>
<td><h1 id="o-2">O</h1></td>
<td><h1 id="section-2"></h1></td>
<td><h1 id="section-3"></h1></td>
<td><h1 id="section-4"></h1></td>
<td><h1 id="section-5"></h1></td>
<td><h1 id="section-6"></h1></td>
<td><h1 id="o-3">O</h1></td>
<td><h1 id="section-7"></h1></td>
<td><h1 id="section-8"></h1></td>
</tr>
<tr class="odd">
<td><h1 id="fire-warning">Fire Warning</h1></td>
<td><h1 id="o-4">O</h1></td>
<td><h1 id="o-5">O</h1></td>
<td><h1 id="section-9"></h1></td>
<td><h1 id="o-6">O</h1></td>
<td><h1 id="section-10"></h1></td>
<td><h1 id="section-11"></h1></td>
<td><h1 id="section-12"></h1></td>
<td><h1 id="x-2">X</h1></td>
<td><h1 id="section-13"></h1></td>
<td><h1 id="section-14"></h1></td>
<td><h1 id="section-15"></h1></td>
<td><h1 id="section-16"></h1></td>
<td><h1 id="section-17"></h1></td>
</tr>
<tr class="even">
<td><h1 id="visible-flame">Visible flame</h1></td>
<td><h1 id="o-7">O</h1></td>
<td><h1 id="o-8">O</h1></td>
<td><h1 id="o-9">O</h1></td>
<td><h1 id="o-10">O</h1></td>
<td><h1 id="section-18"></h1></td>
<td><h1 id="section-19"></h1></td>
<td><h1 id="section-20"></h1></td>
<td><h1 id="o-11">O</h1></td>
<td><h1 id="x-3">X</h1></td>
<td><h1 id="o-12">O</h1></td>
<td><h1 id="section-21"></h1></td>
<td><h1 id="section-22"></h1></td>
<td><h1 id="section-23"></h1></td>
</tr>
<tr class="odd">
<td><h1 id="vibration-1">Vibration </h1></td>
<td><h1 id="section-24"></h1></td>
<td><h1 id="x-4">X</h1></td>
<td><h1 id="o-13">O</h1></td>
<td><h1 id="x-5">X</h1></td>
<td><h1 id="o-14">O</h1></td>
<td><h1 id="section-25"></h1></td>
<td><h1 id="section-26"></h1></td>
<td><h1 id="section-27"></h1></td>
<td><h1 id="section-28"></h1></td>
<td><h1 id="section-29"></h1></td>
<td><h1 id="x-6">X</h1></td>
<td><h1 id="x-7">X</h1></td>
<td><h1 id="section-30"></h1></td>
</tr>
<tr class="even">
<td><h1 id="yaw">Yaw</h1></td>
<td><h1 id="o-15">O</h1></td>
<td><h1 id="o-16">O</h1></td>
<td><h1 id="o-17">O</h1></td>
<td><h1 id="o-18">O</h1></td>
<td><h1 id="o-19">O</h1></td>
<td><h1 id="o-20">O</h1></td>
<td><h1 id="o-21">O</h1></td>
<td><h1 id="section-31"></h1></td>
<td><h1 id="section-32"></h1></td>
<td><h1 id="section-33"></h1></td>
<td><h1 id="section-34"></h1></td>
<td><h1 id="x-8">X</h1></td>
<td><h1 id="section-35"></h1></td>
</tr>
<tr class="odd">
<td><h1 id="high-egt">High EGT</h1></td>
<td><h1 id="section-36"></h1></td>
<td><h1 id="x-9">X</h1></td>
<td><h1 id="x-10">X</h1></td>
<td><h1 id="o-22">O</h1></td>
<td><h1 id="o-23">O</h1></td>
<td><h1 id="section-37"></h1></td>
<td><h1 id="x-11">X</h1></td>
<td><h1 id="section-38"></h1></td>
<td><h1 id="o-24">O</h1></td>
<td><h1 id="x-12">X</h1></td>
<td><h1 id="o-25">O</h1></td>
<td><h1 id="section-39"></h1></td>
<td><h1 id="section-40"></h1></td>
</tr>
<tr class="even">
<td><h1 id="n1-change">N1 change</h1></td>
<td><h1 id="x-13">X</h1></td>
<td><h1 id="x-14">X</h1></td>
<td><h1 id="o-26">O</h1></td>
<td><h1 id="o-27">O</h1></td>
<td><h1 id="x-15">X</h1></td>
<td><h1 id="x-16">X</h1></td>
<td><h1 id="x-17">X</h1></td>
<td><h1 id="section-41"></h1></td>
<td><h1 id="section-42"></h1></td>
<td><h1 id="section-43"></h1></td>
<td><h1 id="section-44"></h1></td>
<td><h1 id="section-45"></h1></td>
<td><h1 id="x-18">X</h1></td>
</tr>
<tr class="odd">
<td><h1 id="n2-change">N2 change</h1></td>
<td><h1 id="x-19">X</h1></td>
<td><h1 id="x-20">X</h1></td>
<td><h1 id="o-28">O</h1></td>
<td><h1 id="o-29">O</h1></td>
<td><h1 id="x-21">X</h1></td>
<td><h1 id="x-22">X</h1></td>
<td><h1 id="x-23">X</h1></td>
<td><h1 id="section-46"></h1></td>
<td><h1 id="section-47"></h1></td>
<td><h1 id="section-48"></h1></td>
<td><h1 id="section-49"></h1></td>
<td><h1 id="section-50"></h1></td>
<td><h1 id="x-24">X</h1></td>
</tr>
<tr class="even">
<td><h1 id="fuel-flow-change">Fuel flow change</h1></td>
<td><h1 id="x-25">X</h1></td>
<td><h1 id="o-30">O</h1></td>
<td><h1 id="o-31">O</h1></td>
<td><h1 id="section-51"></h1></td>
<td><h1 id="o-32">O</h1></td>
<td><h1 id="x-26">X</h1></td>
<td><h1 id="o-33">O</h1></td>
<td><h1 id="o-34">O</h1></td>
<td><h1 id="section-52"></h1></td>
<td><h1 id="section-53"></h1></td>
<td><h1 id="section-54"></h1></td>
<td><h1 id="section-55"></h1></td>
<td><h1 id="x-27">X</h1></td>
</tr>
<tr class="odd">
<td><h1 id="oil-indication-change">Oil indication change</h1></td>
<td><h1 id="x-28">X</h1></td>
<td><h1 id="o-35">O</h1></td>
<td><h1 id="o-36">O</h1></td>
<td><h1 id="section-56"></h1></td>
<td><h1 id="o-37">O</h1></td>
<td><h1 id="x-29">X</h1></td>
<td><h1 id="section-57"></h1></td>
<td><h1 id="o-38">O</h1></td>
<td><h1 id="section-58"></h1></td>
<td><h1 id="section-59"></h1></td>
<td><h1 id="section-60"></h1></td>
<td><h1 id="section-61"></h1></td>
<td><h1 id="section-62"></h1></td>
</tr>
<tr class="even">
<td><h1 id="visible-cowl-damage">Visible cowl damage</h1></td>
<td><h1 id="x-30">X</h1></td>
<td><h1 id="x-31">X</h1></td>
<td><h1 id="section-63"></h1></td>
<td><h1 id="section-64"></h1></td>
<td><h1 id="section-65"></h1></td>
<td><h1 id="section-66"></h1></td>
<td><h1 id="section-67"></h1></td>
<td><h1 id="o-39">O</h1></td>
<td><h1 id="section-68"></h1></td>
<td><h1 id="section-69"></h1></td>
<td><h1 id="section-70"></h1></td>
<td><h1 id="x-32">X</h1></td>
<td><h1 id="section-71"></h1></td>
</tr>
<tr class="odd">
<td><h1 id="smokeodor-in-cabin-bleed-air">Smoke/odor in cabin bleed
air</h1></td>
<td><h1 id="section-72"></h1></td>
<td><h1 id="o-40">O</h1></td>
<td><h1 id="section-73"></h1></td>
<td><h1 id="o-41">O</h1></td>
<td><h1 id="o-42">O</h1></td>
<td><h1 id="section-74"></h1></td>
<td><h1 id="section-75"></h1></td>
<td><h1 id="section-76"></h1></td>
<td><h1 id="section-77"></h1></td>
<td><h1 id="section-78"></h1></td>
<td><h1 id="section-79"></h1></td>
<td><h1 id="section-80"></h1></td>
<td><h1 id="section-81"></h1></td>
</tr>
<tr class="even">
<td><h1 id="epr-change">EPR change</h1></td>
<td><h1 id="x-33">X</h1></td>
<td><h1 id="x-34">X</h1></td>
<td><h1 id="x-35">X</h1></td>
<td><h1 id="o-43">O</h1></td>
<td><h1 id="x-36">X</h1></td>
<td><h1 id="x-37">X</h1></td>
<td><h1 id="x-38">X</h1></td>
<td><h1 id="section-82"></h1></td>
<td><h1 id="section-83"></h1></td>
<td><h1 id="section-84"></h1></td>
<td><h1 id="section-85"></h1></td>
<td><h1 id="section-86"></h1></td>
<td><h1 id="x-39">X</h1></td>
</tr>
<tr class="odd">
<td><h1 id="section-87"></h1></td>
<td><h1 id="section-88"></h1></td>
<td><h1 id="section-89"></h1></td>
<td><h1 id="section-90"></h1></td>
<td><h1 id="section-91"></h1></td>
<td><h1 id="section-92"></h1></td>
<td><h1 id="section-93"></h1></td>
<td><h1 id="section-94"></h1></td>
<td><h1 id="section-95"></h1></td>
<td><h1 id="section-96"></h1></td>
<td><h1 id="section-97"></h1></td>
<td><h1 id="section-98"></h1></td>
<td><h1 id="section-99"></h1></td>
<td><h1 id="section-100"></h1></td>
</tr>
</tbody>
</table>

#  {#section-101}

# X = Symptom very likely

**O = Symptom possible**

Note: blank fields mean that the symptom is unlikely

Appendix

Attached are flash card style summary descriptions of many of the
malfunctions discussed in this text.

+------------------------------------------------------+---------------+
| # Engine Stall/Surge                                 |               |
+------------------------------------------------------+---------------+
| ## **Event Description**                             | ##            |
|                                                      |  **Symptoms** |
| Engine Stall or Surge is a momentary reversal of the |               |
| compressor airflow such that high-pressure air       | High power:   |
| escapes out of the engine inlet.                     | Loud bang and |
|                                                      | yaw (may be   |
|                                                      | repetitive).  |
|                                                      | Flames from   |
|                                                      | inlet and     |
|                                                      | tailpipe.     |
|                                                      | Vibration.    |
|                                                      | High EGT/TGT. |
|                                                      | Parameter     |
|                                                      | fluctuation   |
|                                                      |               |
|                                                      | Low power:    |
|                                                      | Quiet         |
|                                                      | bang/pop or   |
|                                                      | rumble.       |
+------------------------------------------------------+---------------+
| ## **Corrective action**                             |               |
|                                                      |               |
| After stabilizing airplane flight path, observe      |               |
| engine instruments for anomalies. Stall/surge may be |               |
| self-correcting, may require the engine to be        |               |
| throttled back, or may require engine shutdown, if   |               |
| the engine can be positively identified and the      |               |
| stall will not clear.                                |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+

+------------------------------------------------------+---------------+
| # Flameout {#flameout-1}                             |               |
+------------------------------------------------------+---------------+
| ## **Event Description**                             | ##            |
|                                                      |  **Symptoms** |
| Engine Flameout is a condition where the combustor   |               |
| is no longer burning fuel.                           | Single        |
|                                                      | engine: Core  |
|                                                      | speed, EGT,   |
|                                                      | EPR all       |
|                                                      | decay.        |
|                                                      | Electrical    |
|                                                      | generator     |
|                                                      | drops off     |
|                                                      | line; low oil |
|                                                      | pressure      |
|                                                      | warning as    |
|                                                      | core speed    |
|                                                      | drops below   |
|                                                      | idle.         |
|                                                      |               |
|                                                      | Multiple      |
|                                                      | engines:      |
|                                                      |               |
|                                                      | As above, but |
|                                                      | also          |
|                                                      | hydraulic,    |
|                                                      | pneumatic and |
|                                                      | electrical    |
|                                                      | system        |
|                                                      | problems.     |
+------------------------------------------------------+---------------+
| ## **Corrective action**                             |               |
|                                                      |               |
| After stabilizing airplane flight path, verify fuel  |               |
| supply to engine. Re-start engine according to AFM.  |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+

+------------------------------------------------------+---------------+
| # Fire {#fire-1}                                     |               |
+------------------------------------------------------+---------------+
| ## **Event Description**                             | ##            |
|                                                      |  **Symptoms** |
| Engine fire is a fuel, oil or hydraulic fluid fire   |               |
| between the engine casing and the cowlings (or       | Fire warning. |
| occasionally a metal fire). It could result from     | Flame or      |
| severe damage. Hot air leaks can also give a fire    | smoke may be  |
| warning.                                             | observed.     |
+------------------------------------------------------+---------------+
| ## **Corrective action**                             |               |
|                                                      |               |
| After stabilizing airplane flight path, shut the     |               |
| engine down and discharge extinguishant. Avoid       |               |
| restarting the engine.                               |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+

+------------------------------------------------------+---------------+
| # Tailpipe fire                                      |               |
+------------------------------------------------------+---------------+
| ## **Event Description**                             | ##            |
|                                                      |  **Symptoms** |
| Fuel puddles in the tailpipe and ignites on hot      |               |
| surfaces.                                            | Observed      |
|                                                      | flames and    |
|                                                      | smoke. N**o   |
|                                                      | fire          |
|                                                      | warning.**    |
+------------------------------------------------------+---------------+
| ## **Corrective action**                             |               |
|                                                      |               |
| Shut off fuel to the engine and dry motor it.        |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+

+------------------------------------------------------+---------------+
| # Bird Ingestion                                     |               |
+------------------------------------------------------+---------------+
| ## **Event Description**                             | ##            |
|                                                      |  **Symptoms** |
| A bird (or other creature) is sucked into the engine |               |
| inlet. Note: ingestion of ice slabs, blown tires,    | Thud, bang,   |
| etc., will produce similar, but more severe,         | vibration.    |
| symptoms.                                            | Odor in       |
|                                                      | cabin. Surge  |
|                                                      | may result    |
|                                                      | from bird     |
|                                                      | ingestion.    |
+------------------------------------------------------+---------------+
| ## **Corrective action**                             |               |
|                                                      |               |
| After stabilizing airplane flight path, watch engine |               |
| instruments for anomalies. If the engine surges,     |               |
| throttle back or shut down as necessary. If multiple |               |
| engines are affected, operate engines free of        |               |
| surge/stall to maintain desired flight profile.      |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+

+------------------------------------------------------+---------------+
| # Severe Engine Damage                               |               |
+------------------------------------------------------+---------------+
| ## **Event Description**                             | ##            |
|                                                      |  **Symptoms** |
| The engine hardware is damaged to the point where    |               |
| the engine is in no condition to run -- such as      | Depending on  |
| bearing failure, major fan damage from ingestion of  | nature of     |
| foreign objects, blade or rotor disk failures, etc.  | damage --     |
|                                                      | surge/stall,  |
|                                                      | vibration,    |
|                                                      | fire warning, |
|                                                      | high EGT, oil |
|                                                      | system        |
|                                                      | parameters    |
|                                                      | out of        |
|                                                      | limits, rotor |
|                                                      | speed and EPR |
|                                                      | decay, yaw.   |
+------------------------------------------------------+---------------+
| ## **Corrective action**                             |               |
|                                                      |               |
| After stabilizing airplane flight path, observe      |               |
| engine instruments for anomalies. Shut down engine.  |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+

+------------------------------------------------------+---------------+
| # Engine Seizure                                     |               |
+------------------------------------------------------+---------------+
| ## **Event Description**                             | ##            |
|                                                      |  **Symptoms** |
| Engine seizure is the locking up of one or more      |               |
| rotors. It only happens after engines are shut down  | After shut    |
| for severe damage.                                   | down, zero    |
|                                                      | speed on one  |
|                                                      | of the        |
|                                                      | rotors. Minor |
|                                                      | increase in   |
|                                                      | required      |
|                                                      | thrust for    |
|                                                      | flight        |
|                                                      | conditions.   |
+------------------------------------------------------+---------------+
| ## **Corrective action**                             |               |
|                                                      |               |
| Trim and adjust power for increased drag.            |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+

+------------------------------------------------------+---------------+
| # Engine Separation {#engine-separation-2}           |               |
+------------------------------------------------------+---------------+
| ## **Event Description**                             | ##            |
|                                                      |  **Symptoms** |
| Engine Separation is the departure of the engine     |               |
| from the airplane due to mount or pylon failure.     | Loss of all   |
|                                                      | engine        |
|                                                      | parameters.   |
|                                                      |               |
|                                                      | Hydraulic,    |
|                                                      | pneumatic and |
|                                                      | electrical    |
|                                                      | system        |
|                                                      | problems      |
+------------------------------------------------------+---------------+
| ## **Corrective action**                             |               |
|                                                      |               |
| After stabilizing airplane flight path, observe      |               |
| engine instruments for anomalies. Turn off fuel to   |               |
| appropriate engine.                                  |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+
|                                                      |               |
+------------------------------------------------------+---------------+