Figure 13-10. Helicopter heading straight for mountain.
When automated flight equipment is not available, great
care must be taken to prepare properly for a night flight.
SRM becomes more challenging under the cover of
darkness, and caution should be exercised when determining
what artificial light source to use inside the aircraft. A light
source that is too bright will blind the pilot from seeing
outside obstacles or rising terrain. Certain colored lenses
bleach out symbols and markings on a map. Conduct this
planning on the ground, in a dark room if necessary, before
the actual flight.
Pilots must be even more conservative with their decision-
making and planning when flying at night. Flying becomes
more difficult due to the degradation of our sensory perception
and the lack of outside references. Beginning with preflight,
looking over the helicopter with a flashlight can cause pilots
to miss even the smallest discrepancy that they would easily
see during the day. For example, failing to remove one or all
of the tie downs and attempting to take off would probably
result in a dynamic rollover accident. Whenever possible,
preflight inspection should always be conducted during the
day or in a lighted hangar. Depth perception is less acute;
therefore, hover height should be increased to avoid contact
with obstacles and hover speed should be reduced. Weather
conditions can be very deceptive and difficult to detect in
flight under night conditions. On a low-illumination night,
it is easy to fly into clouds without realizing it before it is
too late to correct.
Due to the number of recent CFIT night accidents, the NTSB
issued a safety alert in 2008 about avoiding night CFIT
accidents. That alert included the following information:
• Terrain familiarization is critical to safe visual
operations at night. Use sectional charts or other
topographic references to ensure the helicopter will
safely clear terrain and obstructions all along the route.
• When planning a nighttime VFR flight, follow IFR
practices, such as climbing on a known safe course
until well above surrounding terrain. Choose a cruising
altitude that provides terrain separation similar to IFR
flights (2,000 feet above ground level in mountainous
areas and 1,000 feet above the ground in other areas).
Using this technique, known obstacles, such as towers,
will be avoided.
• When receiving radar services, do not depend on ATC
to warn of terrain hazards. Although controllers try
to warn pilots if they notice a hazardous situation,
they may not always recognize that a particular VFR
aircraft is dangerously close to terrain.
• When ATC issues a heading with an instruction to
“maintain VFR,” be aware that the heading may
not provide adequate terrain clearance. If any doubt
exists about your ability to avoid terrain and obstacles
visually, advise ATC immediately and take action to
reach a safe altitude.
• For improved night vision, the FAA recommends the
use of supplemental oxygen for flights above 5,000 feet.
• Obtain as much information about areas in which you
will be flying, and the routes to them, by utilizing
hazard maps and satellite imagery.
• Before flying at night to unfamiliar remote areas or
areas with hazardous terrain, try to arrange a day flight
for familiarization.
• If a pilot flies at night, especially in remote or unlit
areas, consider whether a global positioning system
(GPS)-based terrain awareness unit would improve
the safety of the flight.
Of particular note in the 2008 safety alert is a comment
regarding oxygen use above 5,000 feet. Most helicopters
are neither required nor equipped for supplemental oxygen
use at this altitude. Due to the physiological effect on night
vision of reduced available oxygen at higher elevations, care
should be taken to exercise light discipline. Interior lighting
should be lowered to the lowest possible levels but must allow
adequate illumination of necessary systems and instruments.
This, in turn, allows greater recognition of outside obstacles
and terrain features.
Limited outside visibility is one constant in CFIT accidents.
In the accident cited at the beginning of this section, it
appears the pilot failed to obtain a weather briefing. If the
pilot had obtained one, he would probably have learned
of the cloud cover and light precipitation present along
his planned route of flight. The limited outside visibility
probably caused the CFIT accident, since no evidence was
found of any pre-impact mechanical discrepancies with the
helicopter’s airframe or systems that would have prevented
normal operation.
Automation Management
Automation management is the control and navigation of an
aircraft by means of the automated systems installed in the
aircraft. One of the most important concepts of automation
management is simply knowing when to use it and when not to.
Ideally, a pilot first learns to perform practical test standard
(PTS) maneuvers and procedures in the aircraft manually,
or hand flying. After successfully demonstrating proficiency
in the basic maneuvers, the pilot is then introduced to the
available automation and/or the autopilot. Obviously, in some
aircraft, not all automated systems may be disengaged for
basic flight. The purpose of basic flight without automation is
to ensure the pilot can hand fly the maneuver when necessary.
Advanced avionics offer multiple levels of automation, from
strictly manual flight to highly automated flight. No one level
of automation is appropriate for all flight situations, but to
avoid potentially dangerous distractions when flying with
advanced avionics, the pilot must know how to manage the
course indicator, the navigation source, and the autopilot.
It is important for a pilot to know the peculiarities of the
particular automated system in use. This ensures the pilot
knows what to expect, how to monitor for proper operation,
and promptly take appropriate action if the system does not
perform as expected.
At the most basic level, managing the autopilot means
knowing at all times which modes are engaged and which
modes are armed to engage. The pilot needs to verify that
armed functions (e.g., navigation tracking or altitude capture)
engage at the appropriate time. Automation management is a
good place to practice the callout technique, especially after
arming the system to make a change in course or altitude.
Callouts are verbalizations of particular flight guidance
automation mode changes. In an attempt to reduce the risk
for mode confusion some operators have required flight
crews to callout all flight guidance automation mode changes
as a means of forcing pilots to monitor the Flight Mode
Annunciator (FMA).
Chapter Summary
This chapter focused on aeronautical decision-making,
which includes SRM training, risk management, workload
or task management, SA, CFIT awareness, and automation
management. Factors affecting a helicopter pilot’s ability to
make safe aeronautical decisions were also discussed. The
importance of learning how to be aware of potential risks in
flying, how to clearly identify those risks, and how to manage
them successfully were also explored.
Absolute altitude. The actual distance an object is above
the ground.
Advancing blade. The blade moving in the same direction as
the helicopter. In helicopters that have counterclockwise main
rotor blade rotation as viewed from above, the advancing
blade is in the right half of the rotor disk area during forward
movement.
Agonic Line. An isogonic line along which there is no
magnetic variation.
Air density. The density of the air in terms of mass per unit
volume. Dense air has more molecules per unit volume than
less dense air. The density of air decreases with altitude above
the surface of the earth and with increasing temperature.
Aircraft pitch. The movement of the aircraft about its lateral,
or pitch, axis. Movement of the cyclic forward or aft causes
the nose of the helicopter to pitch up or down.
Aircraft roll. The movement of the aircraft about its
longitudinal axis. Movement of the cyclic right or left causes
the helicopter to tilt in that direction.
Airfoil. Any surface designed to obtain a useful reaction of
lift, or negative lift, as it moves through the air.
Airworthiness Directive. When an unsafe condition exists
with an aircraft, the FAA issues an Airworthiness Directive
to notify concerned parties of the condition and to describe
the appropriate corrective action.
Altimeter. An instrument that indicates flight altitude by
sensing pressure changes and displaying altitude in feet or
meters.
Angle of attack. The angle between the airfoil’s chord line
and the relative wind.
Antitorque pedal. The pedal used to control the pitch of the
tail rotor or air diffuser in a NOTAR® system.
Glossary
Antitorque rotor. See tail rotor.
Articulated rotor. A rotor system in which each of the blades
is connected to the rotor hub in such a way that it is free to
change its pitch angle, and move up and down and fore and
aft in its plane of rotation.
Autopilot. Those units and components that furnish a means
of automatically controlling the aircraft.
Autorotation. The condition of flight during which the main
rotor is driven only by aerodynamic forces with no power
from the engine.
Axis of rotation. The imaginary line about which the rotor
rotates. It is represented by a line drawn through the center
of, and perpendicular to, the tip-path plane.
Basic empty weight. The weight of the standard helicopter,
operational equipment, unusable fuel, and full operating
fluids, including full engine oil.
Blade coning. An upward sweep of rotor blades as a result
of lift and centrifugal force.
Blade damper. A device attached to the drag hinge to restrain
the fore and aft movement of the rotor blade.
Blade feather or feathering. The rotation of the blade around
the spanwise (pitch change) axis.
Blade flap. The ability of the rotor blade to move in a vertical
direction. Blades may flap independently or in unison.
Blade grip. The part of the hub assembly to which the rotor
blades are attached, sometimes referred to as blade forks.
Blade lead or lag. The fore and aft movement of the blade
in the plane of rotation. It is sometimes called “hunting” or
“dragging.”
Blade loading. The load imposed on rotor blades, determined
by dividing the total weight of the helicopter by the combined
area of all the rotor blades.
Blade root. The part of the blade that attaches to the blade
grip.
Blade span. The length of a blade from its tip to its root.
Blade stall. The condition of the rotor blade when it is
operating at an angle of attack greater than the maximum
angle of lift.
Blade tip. The furthermost part of the blade from the hub
of the rotor.
Blade track. The relationship of the blade tips in the plane
of rotation. Blades that are in track will move through the
same plane of rotation.
Blade tracking. The mechanical procedure used to bring the
blades of the rotor into a satisfactory relationship with each
other under dynamic conditions so that all blades rotate on
a common plane.
Blade twist. The variation in the angle of incidence of a blade
between the root and the tip.
Blowback. The tendency of the rotor disk to tilt aft in
transition to forward flight as a result of unequal airflow.
Calibrated airspeed (CAS). Indicated airspeed of an aircraft,
corrected for installation and instrumentation errors.
Center of gravity. The theoretical point where the entire
weight of the helicopter is considered to be concentrated.
Center of pressure. The point where the resultant of all the
aerodynamic forces acting on an airfoil intersects the chord.
Centrifugal force. The apparent force that an object moving
along a circular path exerts on the body constraining the
object and that acts outwardly away from the center of
rotation.
Centripetal force. The force that attracts a body toward its
axis of rotation. It is opposite centrifugal force.
Chip detector. A warning device that alerts you to any
abnormal wear in a transmission or engine. It consists of a
magnetic plug located within the transmission. The magnet
attracts any metal particles that have come loose from the
bearings or other transmission parts. Most chip detectors have
warning lights located on the instrument panel that illuminate
when metal particles are picked up.
Chord. An imaginary straight line between the leading and
trailing edges of an airfoil section.
Chordwise axis. For semirigid rotors, a term used to describe
the flapping or teetering axis of the rotor.
Coaxial rotor. A rotor system utilizing two rotors turning
in opposite directions on the same centerline. This system is
used to eliminated the need for a tail rotor.
Collective pitch control. The control for changing the pitch
of all the rotor blades in the main rotor system equally and
simultaneously and, consequently, the amount of lift or thrust
being generated.
Coning. See blade coning.
Coriolis effect. The tendency of a rotor blade to increase or
decrease its velocity in its plane of rotation when the center
of mass moves closer to or farther from the axis of rotation.
Cyclic feathering. The mechanical change of the angle of
incidence, or pitch, of individual rotor blades, independent
of other blades in the system.
Cyclic pitch control. The control for changing the pitch of
each rotor blade individually as it rotates through one cycle
to govern the tilt of the rotor disk and, consequently, the
direction and velocity of horizontal movement.
Degraded Visual Environment (DVE). Any flight
environment of reduced visibility in which situational
awareness of the aircrew or control of the aircraft may
be severely diminished, completely lost, or may not be
maintained as comprehensively as they are during flight
operations within clear or undiminished visibility. DVE
conditions are further categorized into eleven different types:
smoke, smog, clouds, rain, fog, snow, whiteout, night, flat
light, sand, and brownout.
Delta hinge. A flapping hinge with an axis skewed so that
the flapping motion introduces a component of feathering that
would result in a restoring force in the flap-wise direction.
Density altitude. Pressure altitude corrected for nonstandard
temperature variations.
Deviation. A compass error caused by magnetic disturbances
from the electrical and metal components in the aircraft. The
correction for this error is displayed on a compass correction
card placed near the magnetic compass of the aircraft.
Direct control. The ability to maneuver a helicopter by tilting
the rotor disk and changing the pitch of the rotor blades.
Direct shaft turbine. A single-shaft turbine engine in which
the compressor and power section are mounted on a common
driveshaft.
Disk area. The area swept by the blades of the rotor. It is
a circle with its center at the hub and has a radius of one
blade length.
Disk loading. The total helicopter weight divided by the
rotor disk area.
Dissymmetry of lift. The unequal lift across the rotor disk
resulting from the difference in the velocity of air over the
advancing blade half and the velocity of air over the retreating
blade half of the rotor disk area.
Drag. An aerodynamic force on a body acting parallel and
opposite to relative wind.
Dual rotor. A rotor system utilizing two main rotors.
Dynamic rollover. The tendency of a helicopter to continue
rolling when the critical angle is exceeded, if one gear is on
the ground, and the helicopter is pivoting around that point.
Emergency Position Indicator Radio Beacon (ERIPB). A
device used to alert search and rescue services in the event
of an emergency by transmitting a coded message on the 406
MHz distress frequency, which is relayed by the Cospas-
Sarsat global satellite system.
Feathering. The action that changes the pitch angle of
the rotor blades by rotating them around their feathering
(spanwise) axis.
Feathering axis. The axis about which the pitch angle of a
rotor blade is varied. Sometimes referred to as the spanwise
axis.
Feedback. The transmittal of forces, which are initiated by
aerodynamic action on rotor blades, to the cockpit controls.
Flapping. The vertical movement of a blade about a flapping
hinge.
Flapping hinge. The hinge that permits the rotor blade to
flap and thus balance the lift generated by the advancing and
retreating blades.
Flare. A maneuver accomplished prior to landing to slow
a helicopter.
Free turbine. A turboshaft engine with no physical
connection between the compressor and power output shaft.
Freewheeling unit. A component of the transmission or
power train that automatically disconnects the main rotor
from the engine when the engine stops or slows below the
equivalent rotor rpm.
Fully articulated rotor system. See articulated rotor system.
Gravity. See weight.
Gross weight. The sum of the basic empty weight and
useful load.
Ground effect. A usually beneficial influence on helicopter
performance that occurs while flying close to the ground. It
results from a reduction in upwash, downwash, and bladetip
vortices, which provide a corresponding decrease in induced
drag.
Ground resonance. Selfexcited vibration occurring
whenever the frequency of oscillation of the blades about the
lead-lag axis of an articulated rotor becomes the same as the
natural frequency of the fuselage.
Gyroscopic procession. An inherent quality of rotating
bodies, which causes an applied force to be manifested 90°
in the direction of rotation from the point where the force
is applied.
Human factors. The study of how people interact with their
environment. In the case of general aviation, it is the study
of how pilot performance is influenced by such issues as the
design of cockpits, the function of the organs of the body, the
effects of emotions, and the interaction and communication
with other participants in the aviation community, such as
other crew members and air traffic control personnel.
Hunting. Movement of a blade with respect to the other
blades in the plane of rotation, sometimes called leading or
lagging.
In ground effect (IGE) hover. Hovering close to the surface
(usually less than one rotor diameter distance above the
surface) under the influence of ground effect.
Induced drag. That part of the total drag that is created by
the production of lift.
Induced flow. The component of air flowing vertically
through the rotor system resulting from the production of lift.
Inertia. The property of matter by which it will remain at rest
or in a state of uniform motion in the same direction unless
acted upon by some external force.
Isogonic line. Lines on charts that connect points of equal
magnetic variation.
Knot. A unit of speed equal to one nautical mile per hour.
LDMAX. The maximum ratio between total lift (L) and total
drag (D). This point provides the best glide speed. Any
deviation from the best glide speed increases drag and reduces
the distance you can glide.
Lateral vibration. A vibration in which the movement is
in a lateral direction, such as imbalance of the main rotor.
Lead and lag. The fore (lead) and aft (lag) movement of the
rotor blade in the plane of rotation.
Licensed empty weight. Basic empty weight not including
full engine oil, just undrainable oil.
Lift. One of the four main forces acting on a helicopter. It
acts perpendicular to the relative wind.
Load factor. The ratio of a specified load weight to the total
weight of the aircraft.
Married needles. A term used when two hands of an
instrument are superimposed over each other, as on the
engine/rotor tachometer.
Mast. The component that supports the main rotor.
Mast bumping. Action of the rotor head striking the mast,
occurring on underslung rotors only.
Navigational aid (NAVAID). Any visual or electronic
device, airborne or on the surface, that provides point-to-point
guidance information, or position data, to aircraft in flight.
Night. The time between the end of evening civil twilight
and the beginning of morning civil twilight, as published in
the American Air Almanac.
Normally aspirated engine. An engine that does not
compensate for decreases in atmospheric pressure through
turbocharging or other means.
One-to-one vibration. A low frequency vibration having
one beat per revolution of the rotor. This vibration can be
either lateral, vertical, or horizontal.
Out of ground effect (OGE) hover. Hovering a distance
greater than one disk diameter above the surface. Because
induced drag is greater while hovering out of ground effect,
it takes more power to achieve a hover out of ground effect.
Parasite drag. The part of total drag created by the form or
shape of helicopter parts.
Payload. The term used for the combined weight of
passengers, baggage, and cargo.
Pendular action. The lateral or longitudinal oscillation of
the fuselage due to its suspension from the rotor system.
Pitch angle. The angle between the chord line of the rotor
blade and the reference plane of the main rotor hub or the
rotor plane of rotation.
Pressure altitude. The height above the standard pressure
level of 29.92 "Hg. It is obtained by setting 29.92 in the
barometric pressure window and reading the altimeter.
Profile drag. Drag incurred from frictional or parasitic
resistance of the blades passing through the air. It does not
change significantly with the angle of attack of the airfoil
section, but it increases moderately as airspeed increases.
Resultant relative wind. Airflow from rotation that is
modified by induced flow.
Retreating blade. Any blade, located in a semicircular part
of the rotor disk, in which the blade direction is opposite to
the direction of flight.
Retreating blade stall. A stall that begins at or near the tip
of a blade in a helicopter because of the high angles of attack
required to compensate for dissymmetry of lift.
Rigid rotor. A rotor system permitting blades to feather,
but not flap or hunt.
Rotational velocity. The component of relative wind
produced by the rotation of the rotor blades.
Rotor. A complete system of rotating airfoils creating lift
for a helicopter.
Rotor brake. A device used to stop the rotor blades during
shutdown.
Rotor disk area. See disk area.
Rotor force. The force produced by the rotor, comprised of
rotor lift and rotor drag.
Semirigid rotor. A rotor system in which the blades are fixed
to the hub, but are free to flap and feather.
Shaft turbine. A turbine engine used to drive an output shaft,
commonly used in helicopters.
Skid. A flight condition in which the rate of turn is too great
for the angle of bank.
Skid shoes. Plates attached to the bottom of skid landing
gear, protecting the skid.
Slip. A flight condition in which the rate of turn is too slow
for the angle of bank.
Solidity ratio. The ratio of the total rotor blade area to total
rotor disk area.
Span. The dimension of a rotor blade or airfoil from root
to tip.
Split needles. A term used to describe the position of the
two needles on the engine/rotor tachometer when the two
needles are not superimposed.
Standard atmosphere. A hypothetical atmosphere based on
averages in which the surface temperature is 59 °F (15 °C),
the surface pressure is 29.92 "Hg (1013.2 Mb) at sea level,
and the temperature lapse rate is approximately 3.5 °F (2
°C) per 1,000 feet.
Static stop. A device used to limit the blade flap, or rotor
flap, at low rpm or when the rotor is stopped.
Steady-state flight. The type of flight experienced when a
helicopter is in straight-and-level, unaccelerated flight, and
all forces are in balance.
Symmetrical airfoil. An airfoil having the same shape on
the top and bottom.
Tail rotor. A rotor turning in a plane perpendicular to that
of the main rotor and parallel to the longitudinal axis of the
fuselage. It is used to control the torque of the main rotor and
to provide movement about the yaw axis of the helicopter.
Teetering hinge. A hinge that permits the rotor blades of a
semirigid rotor system to flap as a unit.
Thrust. The force developed by the rotor blades acting
parallel to the relative wind and opposing the forces of drag
and weight.
Tip-path plane. The imaginary circular plane outlined by
the rotor blade tips as they make a cycle of rotation.
Torque. In helicopters with a single, main rotor system, the
tendency of the helicopter to turn in the opposite direction
of the main rotor rotation.
Trailing edge. The rearmost edge of an airfoil.
Translating tendency. The tendency of the single-rotor
helicopter to move laterally during hovering flight. Also
called tail rotor drift.
Translational lift. The additional lift obtained when entering
forward flight, due to the increased efficiency of the rotor
system.
Transverse-flow effect. The condition of increased drag
and decreased lift in the aft portion of the rotor disk caused
by the air having a greater induced velocity and angle in the
aft portion of the disk.
True altitude. The actual height of an object above mean
sea level.
Turboshaft engine. A turbine engine transmitting power
through a shaft as would be found in a turbine helicopter.
Twist grip. The power control on the end of the collective
control.
Underslung. A rotor hub that rotates below the top of the
mast, as on semirigid rotor systems.
Unloaded rotor. The state of a rotor when rotor force has
been removed, or when the rotor is operating under a low or
negative G condition.
Useful load. The difference between the gross weight and
the basic empty weight. It includes the flight crew, usable
fuel, drainable oil, if applicable, and payload.
Variation. The angular difference between true north and
magnetic north; indicated on charts by isogonic lines.
Vertical vibration. A vibration in which the movement is
up and down, or vertical, as in an out-of-track condition.
Vortex ring state. A transient condition of downward flight
(descending through air after just previously being accelerated
downward by the rotor) during which an appreciable portion
of the main rotor system is being forced to operate at angles
of attack above maximum. Blade stall starts near the hub and
progresses outward as the rate of descent increases.
Weight. One of the four main forces acting on a helicopter.
Equivalent to the actual weight of the helicopter. It acts
downward toward the center of the earth.
Yaw. The movement of a helicopter about its vertical axis.