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Pilot's Handbook of Aeronautical Knowledge
Weather Theory
Wind and Currents

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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




Favorable winds near a high pressure system.
Figure 11-11. Favorable winds near a high pressure system.

Convective currents close to the ground can affect a pilot's
ability to control the aircraft. For example, on final approach,
the rising air from terrain devoid of vegetation sometimes
produces a ballooning effect that can cause a pilot to
overshoot the intended landing spot. On the other hand,
an approach over a large body of water or an area of thick
vegetation tends to create a sinking effect that can cause
an unwary pilot to land short of the intended landing spot.
[Figure 11-14]

Effect of Obstructions on Wind
Another atmospheric hazard exists that can create problems
for pilots. Obstructions on the ground affect the flow of
wind and can be an unseen danger. Ground topography and
large buildings can break up the flow of the wind and create
wind gusts that change rapidly in direction and speed. These
obstructions range from man made structures like hangars
to large natural obstructions, such as mountains, bluffs, or
canyons. It is especially important to be vigilant when flying
in or out of airports that have large buildings or natural
obstructions located near the runway. [Figure 11-15]

The intensity of the turbulence associated with ground
obstructions depends on the size of the obstacle and the
primary velocity of the wind. This can affect the takeoff and
landing performance of any aircraft and can present a very
serious hazard. During the landing phase of flight, an aircraft
may "drop in" due to the turbulent air and be too low to clear
obstacles during the approach.

Convective turbulence avoidance.
Figure 11-12. Convective turbulence avoidance.