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Pilot's Handbook of Aeronautical Knowledge
Aircraft Systems
Turbine Engines

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Pilot's Handbook of Aeronautical Knowledge

Preface

Acknowledgements

Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making

Appendix

Glossary

Index

A more common flameout occurrence is due to low fuel
pressure and low engine speeds, which typically are
associated with high-altitude flight. This situation may also
occur with the engine throttled back during a descent, which
can set up the lean-condition flameout. A weak mixture can
easily cause the flame to die out, even with a normal airflow
through the engine.

Any interruption of the fuel supply can result in a
flameout. This may be due to prolonged unusual attitudes,
a malfunctioning fuel control system, turbulence, icing or
running out of fuel.

Symptoms of a flameout normally are the same as those
following an engine failure. If the flameout is due to a
transitory condition, such as an imbalance between fuel
flow and engine speed, an airstart may be attempted once
the condition is corrected. In any case, pilots must follow
the applicable emergency procedures outlined in the AFM/
POH. Generally these procedures contain recommendations
concerning altitude and airspeed where the airstart is most
likely to be successful.

Performance Comparison
It is possible to compare the performance of a reciprocating
powerplant and different types of turbine engines. For
the comparison to be accurate, thrust horsepower (usable
horsepower) for the reciprocating powerplant must be used
rather than brake horsepower, and net thrust must be used
for the turbine-powered engines. In addition, aircraft design
configuration and size must be approximately the same.

When comparing performance, the following definitions
are useful:

Brake horsepower (BHP)—the horsepower actually delivered
to the output shaft. Brake horsepower is the actual usable
horsepower.

Net thrust—the thrust produced by a turbojet or turbofan
engine.

Thrust horsepower (THP)—the horsepower equivalent of the
thrust produced by a turbojet or turbofan engine.

Equivalent shaft horsepower (ESHP)—with respect to
turboprop engines, the sum of the shaft horsepower (SHP)
delivered to the propeller and THP produced by the exhaust
gases.

Figure 6-29 shows how four types of engines compare in net
thrust as airspeed is increased. This figure is for explanatory
purposes only and is not for specific models of engines. The
following are the four types of engines:
• Reciprocating powerplant
• Turbine, propeller combination (turboprop)
• Turbine engine incorporating a fan (turbofan)
• Turbojet (pure jet)

By plotting the performance curve for each engine, a
comparison can be made of maximum aircraft speed variation
with the type of engine used. Since the graph is only a means
of comparison, numerical values for net thrust, aircraft speed,
and drag are not included.

Engine net thrust versus aircraft speed and drag. Points through F are explained in the text below.
Figure 6-29. Engine net thrust versus aircraft speed and drag. Points
A through F are explained in the text below.

Comparison of the four powerplants on the basis of net thrust
makes certain performance capabilities evident. In the speed
range shown to the left of line A, the reciprocating powerplant
outperforms the other three types. The turboprop outperforms
the turbofan in the range to the left of line C. The turbofan
engine outperforms the turbojet in the range to the left of
line F. The turbofan engine outperforms the reciprocating
powerplant to the right of line B and the turboprop to the
right of line C. The turbojet outperforms the reciprocating
powerplant to the right of line D, the turboprop to the right
of line E, and the turbofan to the right of line F.

 

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