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Pilot's Handbook of Aeronautical Knowledge
Aerodynamics of Flight
Load Factors

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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




Chandelles and Lazy Eights
A chandelle is a maximum performance climbing turn
beginning from approximately straight-and-level flight,
and ending at the completion of a precise 180° of turn in a
wings-level, nose-high attitude at the minimum controllable
airspeed. In this flight maneuver, the aircraft is in a steep
climbing turn and almost stalls to gain altitude while changing
direction. A lazy eight derives its name from the manner in
which the extended longitudinal axis of the aircraft is made
to trace a flight pattern in the form of a figure "8" lying on
its side. It would be difficult to make a definite statement
concerning load factors in these maneuvers as both involve
smooth, shallow dives and pull ups. The load factors incurred
depend directly on the speed of the dives and the abruptness
of the pull ups during these maneuvers.

Generally, the better the maneuver is performed, the less
extreme the load factor induced. A chandelle or lazy eight in
which the pull-up produces a load factor greater than 2 Gs will
not result in as great a gain in altitude, and in low-powered
aircraft it may result in a net loss of altitude.

The smoothest pull up possible, with a moderate load factor,
delivers the greatest gain in altitude in a chandelle and results
in a better overall performance in both chandelles and lazy
eights. The recommended entry speed for these maneuvers
is generally near the manufacturer's design maneuvering
speed which allows maximum development of load factors
without exceeding the load limits.

Rough Air
All standard certificated aircraft are designed to withstand
loads imposed by gusts of considerable intensity. Gust load
factors increase with increasing airspeed, and the strength
used for design purposes usually corresponds to the highest
level flight speed. In extremely rough air, as in thunderstorms
or frontal conditions, it is wise to reduce the speed to the
design maneuvering speed. Regardless of the speed held,
there may be gusts that can produce loads which exceed the
load limits.

Each specific aircraft is designed with a specific G loading
that can be imposed on the aircraft without causing structural
damage. There are two types of load factors factored into
aircraft design, limit load and ultimate load. The limit load
is a force applied to an aircraft that causes a bending of the
aircraft structure that does not return to the original shape.
The ultimate load is the load factor applied to the aircraft
beyond the limit load and at which point the aircraft material
experiences structural failure (breakage). Load factors lower
than the limit load can be sustained without compromising
the integrity of the aircraft structure.

Speeds up to but not exceeding the maneuvering speed allows
an aircraft to stall prior to experiencing an increase in load
factor that would exceed the limit load of the aircraft.
Most AFM/POH now include turbulent air penetration
information, which help today's pilots safely fly aircraft
capable of a wide range of speeds and altitudes. It is important
for the pilot to remember that the maximum "never-exceed"
placard dive speeds are determined for smooth air only. High
speed dives or acrobatics involving speed above the known
maneuvering speed should never be practiced in rough or
turbulent air.