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Pilot's Handbook of Aeronautical Knowledge
Aircraft Performance
Takeoff and Landing Performance

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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

The effect of density altitude on powerplant thrust depends
much on the type of powerplant. An increase in altitude
above standard sea level will bring an immediate decrease in
power output for the unsupercharged reciprocating engine.
However, an increase in altitude above standard sea level will
not cause a decrease in power output for the supercharged
reciprocating engine until the altitude exceeds the critical
operating altitude. For those powerplants that experience
a decay in thrust with an increase in altitude, the effect
on the net accelerating force and acceleration rate can be
approximated by assuming a direct variation with density.
Actually, this assumed variation would closely approximate
the effect on aircraft with high thrust-to-weight ratios.

Proper accounting of pressure altitude and temperature is
mandatory for accurate prediction of takeoff roll distance.
The most critical conditions of takeoff performance are the
result of some combination of high gross weight, altitude,
temperature, and unfavorable wind. In all cases, the pilot
must make an accurate prediction of takeoff distance from
the performance data of the AFM/POH, regardless of the
runway available, and strive for a polished, professional
takeoff procedure.

In the prediction of takeoff distance from the AFM/POH data,
the following primary considerations must be given:
• Pressure altitude and temperature—to define the effect
of density altitude on distance
• Gross weight—a large effect on distance
• Wind—a large effect due to the wind or wind
component along the runway
• Runway slope and condition—the effect of an incline
and retarding effect of factors such as snow or ice

Landing Performance
In many cases, the landing distance of an aircraft will define
the runway requirements for flight operations. The minimum
landing distance is obtained by landing at some minimum
safe speed, which allows sufficient margin above stall and
provides satisfactory control and capability for a go-around.
Generally, the landing speed is some .xed percentage of
the stall speed or minimum control speed for the aircraft
in the landing configuration. As such, the landing will be
accomplished at some particular value of lift coefficient
and AOA. The exact values will depend on the aircraft
characteristics but, once defined, the values are independent
of weight, altitude, and wind.

To obtain minimum landing distance at the specified landing
speed, the forces that act on the aircraft must provide maximum
deceleration during the landing roll. The forces acting on the
aircraft during the landing roll may require various procedures
to maintain landing deceleration at the peak value.

A distinction should be made between the procedures for
minimum landing distance and an ordinary landing roll with
considerable excess runway available. Minimum landing
distance will be obtained by creating a continuous peak
deceleration of the aircraft; that is, extensive use of the brakes
for maximum deceleration. On the other hand, an ordinary
landing roll with considerable excess runway may allow
extensive use of aerodynamic drag to minimize wear and tear
on the tires and brakes. If aerodynamic drag is sufficient to
cause deceleration, it can be used in deference to the brakes
in the early stages of the landing roll; i.e., brakes and tires
suffer from continuous hard use, but aircraft aerodynamic
drag is free and does not wear out with use. The use of
aerodynamic drag is applicable only for deceleration to 60
or 70 percent of the touchdown speed. At speeds less than
60 to 70 percent of the touchdown speed, aerodynamic drag
is so slight as to be of little use, and braking must be utilized
to produce continued deceleration. Since the objective during
the landing roll is to decelerate, the powerplant thrust should
be the smallest possible positive value (or largest possible
negative value in the case of thrust reversers).

In addition to the important factors of proper procedures,
many other variables affect the landing performance. Any
item that alters the landing speed or deceleration rate during
the landing roll will affect the landing distance.
The effect of gross weight on landing distance is one of the
principal items determining the landing distance. One effect
of an increased gross weight is that a greater speed will be
required to support the aircraft at the landing AOA and lift
coefficient. For an example of the effect of a change in gross
weight, a 21 percent increase in landing weight will require
a ten percent increase in landing speed to support the greater
weight.

When minimum landing distances are considered, braking
friction forces predominate during the landing roll and, for
the majority of aircraft configurations, braking friction is the
main source of deceleration.

The minimum landing distance will vary in direct proportion
to the gross weight. For example, a ten percent increase in
gross weight at landing would cause a:
• Five percent increase in landing velocity
• Ten percent increase in landing distance
A contingency of this is the relationship between weight and
braking friction force.

 

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