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Pilot's Handbook of Aeronautical Knowledge
Aircraft Performance
Air Carrier Obstacle Clearance Requirements

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Pilot's Handbook of Aeronautical Knowledge



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




Landing runway requirements.
Figure 10-38. Landing runway requirements.

Landing Runway Required
The runway distance needed for landing can be affected by
the following:
• Pressure altitude
• Temperature
• Headwind component
• Runway gradient or slope
• Aircraft weight

In computing the landing distance required, some manufacturers
do not include all of the above items in their charts, since the
regulations state that only pressure altitude, wind, and aircraft
weight must be considered. Charts are provided for anti-skid
on and anti-skid off conditions, but the use of reverse thrust is
not used in computing required landing distances.

The landing distance, as required by the regulations, is
that distance needed to land and come to a complete stop
from a point 50 feet above the threshold end of the runway.
It includes the air distance required to travel from the 50
foot height to touchdown (which can consume 1,000 feet
of runway distance), plus the stopping distance, with no
margin left over. This is all that is required for 14 CFR part
91 operators (non-air carrier), and all that is shown on some
landing distance required charts.

For air carriers and other commercial operators subject to
14 CFR part 121, a different set of rules applies stating that
the required landing distance from the 50 foot height cannot
exceed 60 percent of the actual runway length available.
In all cases, the minimum airspeed allowed at the 50 foot
height must be no less than 1.3 times the aircraft's stalling
speed in the landing configuration. This speed is commonly
called the aircraft's Vref speed and varies with landing
weight. Figure 10-38 is a diagram of these landing runway

Summary of Landing Requirements
In order to establish the allowable landing weight for a
transport category aircraft, the following details must be
• Airfield pressure altitude
• Temperature
• Headwind component
• Runway length
• Runway gradient or slope
• Runway surface condition
With these details, it is possible to establish the maximum
allowable landing weight, which will be the lower of the
weights as dictated by:
• Landing runway requirements
• Approach climb requirements

In practice, the approach climb limitations (ability to climb
in approach configuration with one engine inoperative)
are seldom encountered because the landing weights upon
arrival at the destination airport are usually low. However,
as in the second segment climb requirement for takeoff, this
approach climb gradient must be met and landing weights
must be restricted if necessary. The most likely conditions
that would make the approach climb critical would be the
landings at high weights and high pressure altitudes and
temperatures, which might be encountered if a landing were
required shortly after takeoff.

Landing field requirements can more frequently limit an
aircraft's allowable landing weight than the approach climb
limitations. Again, however, unless the runway is particularly
short, this is seldom problematical as the average landing
weight at the destination rarely approaches the maximum
design landing weight due to fuel burn off.

Chapter Summary

Performance characteristics and capabilities vary greatly
among aircraft. Moreover, aircraft weight, atmospheric
conditions, and external environmental factors can
significantly affect aircraft performance. It is essential that
a pilot become intimately familiar with the performance
characteristics and capabilities of the aircraft being flown.
The primary source of this information is the AFM/POH.