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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

A change in gross weight will change the net accelerating
force and change the mass that is being accelerated. If the
aircraft has a relatively high thrust-to-weight ratio, the change
in the net accelerating force is slight and the principal effect
on acceleration is due to the change in mass.
For example, a 10 percent increase in takeoff gross weight
would cause:
• A 5 percent increase in takeoff velocity.
• At least a 9 percent decrease in rate of acceleration.
• At least a 21 percent increase in takeoff distance.

With ISA conditions, increasing the takeoff weight of the
average Cessna 182 from 2,400 pounds to 2,700 pounds (11
percent increase) results in an increased takeoff distance from
440 feet to 575 feet (23 percent increase).

For the aircraft with a high thrust-to-weight ratio, the
increase in takeoff distance might be approximately 21 to
22 percent, but for the aircraft with a relatively low thrust to-
weight ratio, the increase in takeoff distance would be
approximately 25 to 30 percent. Such a powerful effect
requires proper consideration of gross weight in predicting
takeoff distance.

The effect of wind on takeoff distance is large, and proper
consideration also must be provided when predicting takeoff
distance. The effect of a headwind is to allow the aircraft
to reach the lift-off speed at a lower groundspeed while the
effect of a tailwind is to require the aircraft to achieve a
greater groundspeed to attain the lift-off speed.

However, a tailwind that is 10 percent of the takeoff airspeed
will increase the takeoff distance approximately 21 percent. In
the case where the headwind speed is 50 percent of the takeoff
speed, the takeoff distance would be approximately 25 percent
of the zero wind takeoff distance (75 percent reduction).

The effect of wind on landing distance is identical to its
effect on takeoff distance. Figure 10-18 illustrates the general
effect of wind by the percent change in takeoff or landing
distance as a function of the ratio of wind velocity to takeoff
or landing speed.

The effect of proper takeoff speed is especially important
when runway lengths and takeoff distances are critical. The
takeoff speeds specified in the AFM/POH are generally
the minimum safe speeds at which the aircraft can become
airborne. Any attempt to take off below the recommended
speed means that the aircraft could stall, be difficult to
control, or have a very low initial rate of climb. In some cases,
an excessive AOA may not allow the aircraft to climb out
of ground effect. On the other hand, an excessive airspeed
at takeoff may improve the initial rate of climb and "feel"
of the aircraft, but will produce an undesirable increase in
takeoff distance. Assuming that the acceleration is essentially
unaffected, the takeoff distance varies with the square of the
takeoff velocity.

Effect of wind on takeoff and landing.
Figure 10-18. Effect of wind on takeoff and landing.

Thus, ten percent excess airspeed would increase the takeoff
distance 21 percent. In most critical takeoff conditions, such
an increase in takeoff distance would be prohibitive, and the
pilot must adhere to the recommended takeoff speeds.
The effect of pressure altitude and ambient temperature
is to define the density altitude and its effect on takeoff
performance. While subsequent corrections are appropriate
for the effect of temperature on certain items of powerplant
performance, density altitude define specific effects on
takeoff performance. An increase in density altitude can
produce a twofold effect on takeoff performance:
1. Greater takeoff speed
2. Decreased thrust and reduced net accelerating force
If an aircraft of given weight and configuration is operated at
greater heights above standard sea level, the aircraft requires
the same dynamic pressure to become airborne at the takeoff
lift coefficient. Thus, the aircraft at altitude will take off at the
same indicated airspeed (IAS) as at sea level, but because of
the reduced air density, the TAS will be greater.

 

10-14