Chapter 12
Night Operations ...............................................12-1
Introduction ..................................................................12-1
Visual Deficiencies ......................................................12-2
Night Myopia ...........................................................12-2
Hyperopia .................................................................12-2
Astigmatism .............................................................12-2
Presbyopia ................................................................12-2
Vision in Flight ............................................................12-2
Visual Acuity ............................................................12-3
The Eye.....................................................................12-4
Cones ........................................................................12-4
Rods ..........................................................................12-4
Night Vision .................................................................12-4
Night Scanning .........................................................12-4
Obstruction Detection...............................................12-5
Aircraft Lighting.......................................................12-6
Visual Illusions .........................................................12-6
Relative-Motion Illusion ..........................................12-6
Confusion with Ground Lights .................................12-6
Reversible Perspective Illusion ................................12-6
Flicker Vertigo .........................................................12-7
Night Flight ..................................................................12-7
Preflight ....................................................................12-7
Cockpit Lights ..........................................................12-8
Engine Starting and Rotor Engagement ...................12-8
Taxi Technique .........................................................12-8
Night Traffic Patterns ...............................................12-8
Takeoff .....................................................................12-8
En Route Procedures ................................................12-9
Collision Avoidance at Night ...................................12-9
Approach and Landing .............................................12-9
Illusions Leading to Landing Errors .........................12-9
Featureless Terrain Illusion ................................12-10
Atmospheric Illusions .........................................12-10
Ground Lighting Illusions ...................................12-10
Helicopter Night VFR Operations .............................12-10
Chapter Summary ......................................................12-10
Chapter 13
Effective Aeronautical Decision-Making .........13-1
Introduction ..................................................................13-1
Aeronautical Decision-Making (ADM) .......................13-2
Scenario ....................................................................13-2
Trescott Tips .............................................................13-3
The Decision-Making Process..................................13-4
Defining the Problem ............................................13-4
Choosing a Course of Action ................................13-4
Implementing the Decision and Evaluating the
Outcome ................................................................13-4
Decision-Making Models .........................................13-5
Pilot Self-Assessment ..................................................13-6
Curiosity: Healthy or Harmful? ................................13-6
The PAVE Checklist ................................................13-6
Single-Pilot Resource Management .............................13-7
Risk Management ........................................................13-9
Four Risk Elements ..................................................13-9
Assessing Risk ........................................................13-10
Using the 3P Model to Form Good Safety
Habits .....................................................................13-11
Workload or Task Management .................................13-12
Situational Awareness ................................................13-13
Obstacles to Maintaining Situational
Awareness .............................................................13-13
Operational Pitfalls .................................................13-15
Controlled Flight Into Terrain (CFIT)
Awareness ..................................................................13-15
Automation Management ...........................................13-18
Chapter Summary ......................................................13-18
Glossary ..............................................................G-1
Index ......................................................................I-1
Chapter 1
Introduction to the Helicopter
Introduction
A helicopter is an aircraft that is lifted and propelled by one
or more horizontal rotors, each rotor consisting of two or
more rotor blades. Helicopters are classified as rotorcraft
or rotary-wing aircraft to distinguish them from fixed-wing
aircraft, because the helicopter derives its source of lift from
the rotor blades rotating around a mast. The word “helicopter”
is adapted from the French hélicoptère, coined by Gustave de
Ponton d’Amécourt in 1861. It is linked to the Greek words
helix/helikos (“spiral” or “turning”) and pteron (“wing”).
Figure 1-1. Search and rescue helicopter conducting a pinnacle
approach.
Figure 1-2. Search and rescue helicopter landing in a confined area.
As an aircraft, the primary advantages of the helicopter are
due to the rotor blades that revolve through the air, providing
lift without requiring the aircraft to move forward. This lift
allows the helicopter to hover in one area and to take off
and land vertically without the need for runways. For this
reason, helicopters are often used in congested or isolated
areas where fixed-wing aircraft are not able to take off or
land. [Figures 1-1 and 1-2]
Piloting a helicopter requires adequate, focused and safety-
orientated training. It also requires continuous attention
to the machine and the operating environment. The pilot
must work in three dimensions and use both arms and
both legs constantly to keep the helicopter in a desired
state. Coordination, timing and control touch are all used
simultaneously when flying a helicopter.
Although helicopters were developed and built during the
first half-century of flight, some even reaching limited
production; it was not until 1942 that a helicopter designed by
Igor Sikorsky reached full-scale production, with 131 aircraft
built. Even though most previous designs used more than one
main rotor, it was the single main rotor with an antitorque
tail rotor configuration that would come to be recognized
worldwide as the helicopter.
Turbine Age
In 1951, at the urging of his contacts at the Department of
the Navy, Charles H. Kaman modified his K-225 helicopter
with a new kind of engine, the turbo-shaft engine. This
adaptation of the turbine engine provided a large amount of
horsepower to the helicopter with a lower weight penalty
than piston engines, heavy engine blocks, and auxiliary
components. On December 11, 1951, the K-225 became
the first turbine-powered helicopter in the world. Two years
later, on March 26, 1954, a modified Navy HTK-1, another
Kaman helicopter, became the first twin-turbine helicopter
to fly. However, it was the Sud Aviation Alouette II that
would become the first helicopter to be produced with a
turbine engine.
Reliable helicopters capable of stable hover flight were
developed decades after fixed-wing aircraft. This is largely
due to higher engine power density requirements than
fixed-wing aircraft. Improvements in fuels and engines
during the first half of the 20th century were critical factors
in helicopter development. The availability of lightweight
turbo-shaft engines in the second half of the 20th century led
to the development of larger, faster, and higher-performance
helicopters. While smaller and less expensive helicopters
still use piston engines, turboshaft engines are the preferred
powerplant for helicopters today.
The turbine engine has the following advantages over a
reciprocating engine:
• Less vibration
• Increased aircraft performance
• Reliability
• Ease of operation
Figure 1-3. The many uses for a helicopter include search and rescue
(top), firefighting (middle), and construction (bottom).
Hub
Mast Rotor blades
Figure 1-4. Basic components of the rotor system.
Uses
Due to the unique operating characteristics of the helicopter—
its ability to take off and land vertically, to hover for extended
periods of time, and the aircraft’s handling properties under
low airspeed conditions—it has been chosen to conduct tasks
that were previously not possible with other aircraft or were
too time- or work-intensive to accomplish on the ground.
Today, helicopters are used for transportation, construction,
firefighting, search and rescue, and a variety of other jobs
that require its special capabilities. [Figure 1-3]
Rotor System
The helicopter rotor system is the rotating part of a
helicopter that generates lift. A rotor system may be mounted
horizontally, as main rotors are, providing lift vertically; and
it may be mounted vertically, such as a tail rotor, to provide
lift horizontally as thrust to counteract torque effect. In the
case of tilt rotors, the rotor is mounted on a nacelle that
rotates at the edge of the wing to transition the rotor from a
horizontal mounted position, providing lift horizontally as
thrust, to a vertical mounted position providing lift exactly
as a helicopter.
The rotor consists of a mast, hub, and rotor blades. [Figure 1-4]
The mast is a hollow cylindrical metal shaft which extends
upwards from and is driven by the transmission. At the top
of the mast is the attachment point for the rotor blades called
the hub. The rotor blades are then attached to the hub by
several different methods. Main rotor systems are classified
according to how the main rotor blades are attached and
move relative to the main rotor hub. There are three basic
classifications: semirigid, rigid, or fully articulated, although
some modern rotor systems use an engineered combination
of these types. All three rotor systems are discussed with
greater detail in Chapter 4, Helicopter Components, Sections,
and Systems.
With a single main rotor helicopter, a torque effect is created
as the engine turns the rotor. This torque causes the body of
the helicopter to turn in the opposite direction of the rotor
(Newton’s Third Law: Every action has an equal and opposite
reaction, as explained in Chapter 2, Aerodynamics of Flight).
To eliminate this effect, some sort of antitorque control must
be used with a sufficient margin of power available to allow
the helicopter to maintain its heading and prevent the aircraft
from moving unsteadily. The three most common controls
used today are the traditional tail rotor, Fenestron (also called
a fantail), and the NOTAR®. All three antitorque designs will
be discussed in Chapter 4, Helicopter Components, Sections,
and Systems.
Figure 1-7. Coaxial rotors.
Figure 1-5. Igor Sikorsky designed the VS-300 helicopter
incorporating the tail rotor into the design.
Figure 1-6. Tandem rotor helicopters.
Rotor Configurations
Most helicopters have a single, main rotor but require a
separate rotor to overcome torque which is a turning or
twisting force. This is accomplished through a variable
pitch, antitorque rotor or tail rotor. This is the design that
Igor Sikorsky settled on for his VS-300 helicopter shown
in Figure 1-5. It has become the recognized convention for
helicopter design, although designs do vary. Helicopter main
rotor designs from different manufacturers rotate in one of
two different directions (clockwise or counter-clockwise
when viewed from above). This can make it confusing when
discussing aerodynamic effects on the main rotor between
different designs, since the effects may manifest on opposite
sides of each aircraft. For clarity, throughout this handbook,
all examples use a counter-clockwise rotating main rotor
system when viewed from above.
For clarity, throughout this handbook, all examples use a
counter-clockwise rotating main rotor system when viewed
from above.
Tandem Rotor
Tandem rotor (sometimes referred to as dual rotor) helicopters
have two large horizontal rotor assemblies, instead of one
main assembly and a smaller tail rotor. [Figure 1-6] Single
rotor helicopters need a tail rotor to neutralize the twisting
momentum produced by the single large rotor. Tandem
rotor helicopters, however, use counter-rotating rotors, each
canceling out the other’s torque. Counter-rotating rotor
blades will not collide with and destroy each other if they
flex into the other rotor’s pathway. This configuration has
the advantage of being able to hold more weight with shorter
blades, since there are two blade sets. Also, all the power
from the engines can be used for lift, whereas a single rotor
helicopter must use some power to counter main rotor torque.
Because of this, tandem helicopters make up some of the
most powerful and fastest rotor system aircraft.
Coaxial Rotors
Coaxial rotors are a pair of rotors turning in opposite
directions, but mounted on a mast, with the same axis of
rotation, one above the other. This configuration is a noted
feature of helicopters produced by the Russian Kamov
helicopter design bureau. [Figure 1-7]
Intermeshing Rotors
Intermeshing rotors on a helicopter are a set of two rotors
turning in opposite directions, with each rotor mast mounted
on the helicopter with a slight angle to the other so that
the blades intermesh without colliding. [Figure 1-8] This
arrangement allows the helicopter to function without the
need for a tail rotor. It has high stability and powerful lifting
capability. This configuration is sometimes referred to as a
synchropter. The arrangement was developed in Germany
Tail rotor driveshaft
located inside
of tail body
Tail rotor shaft
Tail rotor
Pitch change links
Cross Head
Figure 1-8. HH-43 Huskie with intermeshing rotors.
Figure 1-9. Basic tail rotor components.
for a small anti-submarine warfare helicopter, the Flettner
Fl 282 Kolibri. During the Cold War the American Kaman
Aircraft company produced the HH-43 Huskie, for USAF
firefighting purposes. The latest Kaman K-MAX model is
a dedicated sky crane design used for construction work.
Tail Rotor
The tail rotor is a smaller rotor mounted vertically or near-
vertically on the tail of a traditional single-rotor helicopter.
The tail rotor either pushes or pulls against the tail to counter
the torque. The tail rotor drive system consists of a drive shaft
powered from the main transmission and a gearbox mounted
at the end of the tail boom. [Figure 1-9] The drive shaft may
consist of one long shaft or a series of shorter shafts connected
at both ends with flexible couplings. The flexible couplings
allow the drive shaft to flex with the tail boom.
The gearbox at the end of the tail boom provides an angled
drive for the tail rotor and may also include gearing to adjust
the output to the optimum rotational speed typically measured
in revolutions per minute (rpm) for the tail rotor. On some
larger helicopters, intermediate gearboxes are used to angle
the tail rotor drive shaft from along the tail boom or tailcone
to the top of the tail rotor pylon, which also serves as a vertical
stabilizing airfoil to alleviate the power requirement for the
tail rotor in forward flight. The pylon (or vertical fin) may
also provide limited antitorque within certain airspeed ranges
if the tail rotor or the tail rotor flight controls fail.
Controlling Flight
A helicopter has four primary flight controls:
• Cyclic
• Collective
• Antitorque pedals
• Throttle
Cyclic
The cyclic control is usually located between the pilot’s legs
and is commonly called the “cyclic stick” or simply “cyclic.”
On most helicopters, the cyclic is similar to a joystick;
however, Robinson helicopters have unique T-bar cyclic
control systems. A few helicopters have cyclic controls that
descend into the cockpit from overhead while others use side
cyclic controls.
The control is called the cyclic because it can vary the pitch
of the rotor blades throughout each revolution of the main
rotor system (i.e., through each cycle of rotation) to develop
unequal lift (thrust). The result is to tilt the rotor disk in a
particular direction, resulting in the helicopter moving in that
direction. If the pilot pushes the cyclic forward, the rotor disk
tilts forward, and the rotor produces a thrust in the forward
direction. If the pilot pushes the cyclic to the side, the rotor
disk tilts to that side and produces thrust in that direction,
causing the helicopter to hover sideways. [Figure 1-10]
Collective
The collective pitch control, or collective, is located on the
left side of the pilot’s seat with a pilot-selected variable
friction control to prevent inadvertent movement. The
collective changes the pitch angle of all the main rotor blades
Horizontal stabilizer
Twist grip throttle
Collective control
Throttle cable
Throttle linkage
Fuel control or carburetor
Figure 1-11. The throttle control mounted at the end of the collective
control.
Figure 1-12. The horizontal stabilizer helps level the helicopter to
minimize drag during flight.
Swash plate
Figure 1-10. Cyclic controls changing the pitch of the rotor blades.
collectively (i.e., all at the same time) and independently of
their positions. Therefore, if a collective input is made, all
the blades change equally, increasing or decreasing total
lift or thrust, with the result of the helicopter increasing or
decreasing in altitude or airspeed.
Antitorque Pedals
The antitorque pedals are located in the same position as the
rudder pedals in a fixed-wing aircraft and serve a similar
purpose, namely to control the direction in which the nose
of the aircraft is pointed. Application of the pedal in a given
direction changes the pitch of the tail rotor blades, increasing
or reducing the thrust produced by the tail rotor, causing the
nose to yaw in the direction of the applied pedal. The pedals
mechanically change the pitch of the tail rotor, altering the
amount of thrust produced.
Throttle
Helicopter rotors are designed to operate at a specific rpm.
The throttle controls the power produced by the engine, which
is connected to the rotor by a transmission. The purpose of
the throttle is to maintain enough engine power to keep the
rotor rpm within allowable limits to produce enough lift for
flight. In single-engine helicopters, if so equipped, the throttle
control is typically a twist grip mounted on the collective
control, but it can also be a lever mechanism in fully
governed systems. Multi-engine helicopters generally have
a power lever or mode switch for each engine. [Figure 1-11]
Helicopter flight controls are discussed in greater detail
throughout Chapter 4, Helicopter Components, Sections
and Systems.
Flight Conditions
There are two basic flight conditions for a helicopter: hover
and forward flight. Hovering is the most challenging part of
flying a helicopter. This is because a helicopter generates
its own gusty air while in a hover, which acts against the
fuselage and flight control surfaces. The end result is the
need for constant control inputs and corrections by the pilot
to keep the helicopter where it is required to be. Despite
the complexity of the task, the control inputs in a hover are
simple. The cyclic is used to eliminate drift in the horizontal
direction that is to control forward and back, right and left.
The collective is used to maintain altitude. The pedals are
used to control nose direction or heading. It is the interaction
of these controls that makes hovering so difficult, since an
adjustment in any one control requires an adjustment of the
other two, creating a cycle of constant correction.
Displacing the cyclic forward initially causes the nose to
pitch down, with a resultant increase in airspeed and loss
of altitude. Aft cyclic initially causes the nose to pitch up,
slowing the helicopter and causing it to climb; however, as
the helicopter reaches a state of equilibrium, the horizontal
stabilizer helps level the helicopter to minimize drag, unlike