直升机飞行手册Rotorcraft flying handbook

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DISC LOADING—The total helicopter weight divided by the rotor disc

area.

DISSYMMETRY OF LIFT—The

unequal lift across the rotor disc

resulting from the difference in the

velocity of air over the advancing

blade half and retreating blade half of

the rotor disc 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.

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 HINGE—The hinge

that permits the rotor blade to flap and

thus balance the lift generated by the

advancing and retreating blades.

FLAPPING—The vertical movement of a blade about a flapping

hinge.

FLARE—A maneuver accomplished

prior to landing to slow down a rotorcraft.

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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 r.p.m.

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 rotorcraft 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.

GYROCOPTER — Trademark

applied to gyroplanes designed and

produced by the Bensen Aircraft

Company.

GYROSCOPIC PRECESSION—

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

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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—A term used

in reference to semirigid rotors

describing the flapping or teetering

axis of the rotor.

COAXIL 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 CON-

TROL—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 or further from the axis

of rotation.

CYCLIC FEATHERING—The

mechanical change of the angle of

incidence, or pitch, of individual rotor

blades independently 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 disc and, consequently, the

direction and velocity of horizontal

movement.

DELTA HINGE—A flapping hinge

with a skewed axis 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 place near the magnetic

compass of the aircraft.

DIRECT CONTROL—The ability

to maneuver a rotorcraft by tilting the

rotor disc and changing the pitch of

the rotor blades.

DIRECT SHAFT TURBINE—A

shaft turbine engine in which the compressor and power section are mounted on a common driveshaft.

DISC 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.

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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 rotorcraft,

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 FEATH-

ERING—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 further most 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 disc to tilt aft in forward flight as

a result of flapping.

GLOSSARY

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BUNTOVER—The tendency of a

gyroplane to pitch forward when rotor

force is removed.

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

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aviation. Pilots who choose to operate outside of the

regulations, or on the ragged edge, eventually get

caught, or even worse, they end up having an accident.

Consider the following scenario.

Dick is planning to fly the following morning and realizes that his medical certificate has expired. He knows

that he will not have time to take a flight physical

before his morning flight. Dick thinks to himself “The

rules are too restrictive. Why should I spend the time

and money on a physical when I will be the only one at

risk if I fly tomorrow?”

Dick decides to fly the next morning thinking that no

harm will come as long as no one finds out that he is

flying illegally. He pulls his gyroplane out from the

hangar, does the preflight inspection, and is getting

ready to start the engine when an FAA inspector walks

up and greets him. The FAA inspector is conducting a

random inspection and asks to see Dick’s pilot and

medical certificates.

Dick subjected himself to the hazardous attitude of “antiauthority.” Now, he will be unable to fly, and has invited

an exhaustive review of his operation by the FAA. Dick

could have prevented this event if had taken the time to

think, “Follow the rules. They are usually right.”

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ABSOLUTE ALTITUDE—The actual distance an object is above the

ground.

ADVANCING BLADE—The blade

moving in the same direction as the

helicopter or gyroplane. In rotorcraft

that have counterclockwise main rotor

blade rotation as viewed from above,

the advancing blade is in the right half

of the rotor disc area during forward

movement.

AIRFOIL—Any surface designed to

obtain a useful reaction of lift, or negative lift, as it moves through the air.

AGONIC LINE—A 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—When referenced to an aircraft, it is the movement about its lateral, or pitch axis.

Movement of the cyclic forward or aft

causes the nose of the helicopter or

gyroplane to pitch up or down.

AIRCRAFT ROLL—Is the movement of the aircraft about its

longitudinal axis. Movement of the

cyclic right or left causes the helicopter or gyroplane to tilt in that direction.

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.

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.

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Pat has been flying gyroplanes for years and has an

excellent reputation as a skilled pilot. He has recently

built a high performance gyroplane with an advanced

rotor system. Pat was excited to move into a more

advanced aircraft because he had seen the same design

performing aerobatics in an airshow earlier that year.

He was amazed by the capability of the machine. He

had always felt that his ability surpassed the capability

of the aircraft he was flying. He had invested a large

amount of time and resources into the construction of

the aircraft, and, as he neared completion of the assembly, he was excited about the opportunity of showing

his friends and family his capabilities.

During the first few flights, Pat was not completely

comfortable in the new aircraft, but he felt that he was

progressing through the transition at a much faster

pace than the average pilot. One morning, when he was

with some of his fellow gyroplane enthusiasts, Pat

began to brag about the superior handling qualities of

the machine he had built. His friends were very excited,

and Pat realized that they would be expecting quite a

show on his next flight. Not wanting to disappoint them,

he decided that although it might be early, he would

give the spectators on the ground a real show. On his

first pass he came down fairly steep and fast and recovered from the dive with ease. Pat then decided to make

another pass only this time he would come in much

steeper. As he began to recover, the aircraft did not

climb as he expected and almost settled to the ground.

Pat narrowly escaped hitting the spectators as he was

trying to recover from the dive.

Pat had let the “macho” hazardous attitude influence

his decision making. He could have avoided the consequences of this attitude if he had stopped to think that

taking chances is foolish.

RESIGNATION

Some of the elements pilots face cannot be controlled.

Although we cannot control the weather, we do have

some very good tools to help predict what it will do,

and how it can affect our ability to fly safely. Good

pilots always make decisions that will keep their

options open if an unexpected event occurs while

flying. One of the greatest resources we have in the

cockpit is the ability to improvise and improve the

overall situation even when a risk element jeopardizes

the probability of a successful flight. Consider the following scenario.

Judi flies her gyroplane out of a small grass strip on

her family’s ranch. Although the rugged landscape of

the ranch lends itself to the remarkable scenery, it

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leaves few places to safely land in the event of an emergency. The only suitable place to land other than the

grass strip is to the west on a smooth section of the road

leading to the house. During Judi’s training, her traffic

patterns were always made with left turns. Figuring

this was how she was to make all traffic patterns, she

applied this to the grass strip at the ranch. In addition,

she was uncomfortable with making turns to the right.

Since, the wind at the ranch was predominately from

the south, this meant that the traffic pattern was to the

east of the strip.

Judi’s hazardous attitude is “resignation.” She has

accepted the fact that her only course of action is to fly

east of the strip, and if an emergency happens, there is

not much she can do about it. The antidote to this

hazardous attitude is “I’m not helpless, I can make a difference.” Judi could easily modify her traffic pattern so

that she is always within gliding distance of a

suitable landing area. In addition, if she was uncomfortable with a maneuver, she could get additional training.

ANTI-AUTHORITY

Regulations are implemented to protect aviation

personnel as well as the people who are not involved in

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design specifications.

INVULNERABILITY

Another area that can often lead to trouble for a gyroplane pilots is the failure to obtain adequate flight

HAZARDOUS ATTITUDE ANTIDOTE

Anti-authority:

"Don't tell me!"

"Follow the rules. They are

usually right."

Impulsivity:

"Do something—quickly!" "Not so fast. Think first."

Invulnerability:

"It won't happen to me!" "It could happen to me."

Macho:

"I can do it." "Taking chances is foolish."

Resignation:

"What's the use?"

"I'm not helpless. I can make the

difference."

Figure 22-1. To overcome hazardous attitudes, you must

memorize the antidotes for each of them. You should know

them so well that they will automatically come to mind when

you need them.

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instruction to operate their gyroplane safely. This can

be the result of people thinking that because they can

build the machine themselves, it must be simple

enough to learn how to fly by themselves. Other

reasons that can lead to this problem can be simply

monetary, in not wanting to pay the money for adequate

instruction, or feeling that because they are qualified in

another type of aircraft, flight instruction is not necessary. In reality, gyroplane operations are quite unique,

and there is no substitute for adequate training by a

competent and authorized instructor. Consider the

following scenario.

Jim recently met a coworker who is a certified pilot and

owner of a two-seat gyroplane. In discussing the gyroplane with his coworker, Jim was fascinated and

reminded of his days in the military as a helicopter

pilot many years earlier. When offered a ride, Jim readily accepted. He met his coworker at the airport the

following weekend for a short flight and was immediately hooked. After spending several weeks researching

available designs, Jim decided on a particular

gyroplane and purchased a kit. He had it assembled in

a few months, with the help and advice of his new friend

and fellow gyroplane enthusiast. When the gyroplane

was finally finished, Jim asked his friend to take him

for a ride in his two-seater to teach him the basics of

flying. The rest, he said, he would figure out while

flying his own machine from a landing strip that he had

fashioned in a field behind his house.

Jim is unknowingly inviting disaster by allowing himself to be influenced by the hazardous attitude of

“invulnerability.” Jim does not feel that it is possible to

have an accident, probably because of his past experience in helicopters and from witnessing the ease with

which his coworker controlled the gyroplane on their

flight together. What Jim is failing to consider, however, is the amount of time that has passed since he was

proficient in helicopters, and the significant differences

between helicopter and gyroplane operations. He is

also overlooking the fact that his friend is a certificated

pilot, who has taken a considerable amount of instruction to reach his level of competence. Without adequate

instruction and experience, Jim could, for example,

find himself in a pilot-induced oscillation without

knowing the proper technique for recovery, which

could ultimately be disastrous. The antidote for an

attitude of invulnerability is to realize that accidents

can happen to anyone.

MACHO

Due to their unique design, gyroplanes are quite

responsive and have distinct capabilities. Although

gyroplanes are capable of incredible maneuvers, they

do have limitations. As gyroplane pilots grow more

comfortable with their machines, they might be

tempted to operate progressively closer to the edge of

the safe operating envelope. Consider the following

scenario.

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heavy clothing for a flight into cold weather. Another

consideration is carrying a cellular phone. Several

pilots have been rescued after calling someone to

indicate there had been an accident.

BestGlideSpeed

TooFast

TooSlow

Figure 21-3. Any deviation from best glide speed will reduce the distance you can glide and may cause you to land short of a

safe touchdown point.

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As with any aircraft, the ability to pilot a gyroplane

safely is largely dependent on the capacity of the pilot

to make sound and informed decisions. To this end,

techniques have been developed to ensure that a pilot

uses a systematic approach to making decisions, and

that the course of action selected is the most appropriate for the situation. In addition, it is essential that you

learn to evaluate your own fitness, just as you evaluate

the airworthiness of your aircraft, to ensure that your

physical and mental condition is compatible with a safe

flight. The techniques for acquiring these essential

skills are explained in depth in Chapter 14—

Aeronautical Decision Making (Helicopter).

As explained in Chapter 14, one of the best methods to

develop your aeronautical decision making is learning

to recognize the five hazardous attitudes, and how to

counteract these attitudes. [Figure 22-1] This chapter

focuses on some examples of how these hazardous attitudes can apply to gyroplane operations.

IMPULSIVITY

Gyroplanes are a class of aircraft which can be acquired,

constructed, and operated in ways unlike most other aircraft. This inspires some of the most exciting and

rewarding aspects of flying, but it also creates a unique

set of dangers to which a gyroplane pilot must be alert.

For example, a wide variety of amateur-built gyroplanes

are available, which can be purchased in kit form and

assembled at home. This makes the airworthiness of

these gyroplanes ultimately dependent on the vigilance

of the one assembling and maintaining the aircraft.

Consider the following scenario.

Jerry recently attended an airshow that had a gyroplane flight demonstration and a number of gyroplanes

on display. Being somewhat mechanically inclined and

retired with available spare time, Jerry decided that

building a gyroplane would be an excellent project for

him and ordered a kit that day. When the kit arrived,

Jerry unpacked it in his garage and immediately began

the assembly. As the gyroplane neared completion,

Jerry grew more excited at the prospect of flying an aircraft that he had built with his own hands. When the

gyroplane was nearly complete, Jerry noticed that a

rudder cable was missing from the kit, or perhaps lost

during the assembly. Rather than contacting the manufacturer and ordering a replacement, which Jerry

thought would be a hassle and too time consuming, he

went to his local hardware store and purchased some

cable he thought would work. Upon returning home, he

was able to fashion a rudder cable that seemed functional and continued with the assembly.

Jerry is exhibiting “impulsivity.” Rather than taking the

time to properly build his gyroplane to the specifications set forth by the manufacturer, Jerry let his

excitement allow him to cut corners by acting on

impulse, rather than taking the time to think the matter

through. Although some enthusiasm is normal during

assembly, it should not be permitted to compromise the

airworthiness of the aircraft. Manufacturers often use

high quality components, which are constructed and

tested to standards much higher than those found in

hardware stores. This is particularly true in the area of

cables, bolts, nuts, and other types of fasteners where

strength is essential. The proper course of action Jerry

should have taken would be to stop, think, and consider

the possible consequences of making an impulsive

decision. Had he realized that a broken

rudder cable in flight could cause a loss of control of

the gyroplane, he likely would have taken the time to

contact the manufacturer and order a cable that met the

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EMERGENCY APPROACH AND

LANDING

The modern engines used for powering gyroplanes are

generally very reliable, and an actual mechanical malfunction forcing a landing is not a common occurrence.

Failures are possible, which necessitates planning for

and practicing emergency approaches and landings.

The best way to ensure that important items are not

overlooked during an emergency procedure is to use a

checklist, if one is available and time permits. Most

gyroplanes do not have complex electrical, hydraulic,

or pneumatic systems that require lengthy checklists.

In these aircraft, the checklist can be easily committed

to memory so that immediate action can be taken if

Rotor

Center of Gravity

122°

122°

116°

Figure 21-2. Taxiing on rough terrain can send a shock wave

to the rotor system, resulting in the blades of a three-bladed

rotor system moving from their normal 120° relationship to

each other.

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needed. In addition, you should always maintain an

awareness of your surroundings and be constantly on

the alert for suitable emergency landing sites.

When an engine failure occurs at altitude, the first

course of action is to adjust the gyroplane’s pitch attitude to achieve the best glide speed. This yields the

most distance available for a given altitude, which in

turn, allows for more possible landing sites. A common

mistake when learning emergency procedures is

attempting to stretch the glide by raising the nose,

which instead results in a steep approach path at a slow

airspeed and a high rate of descent. [Figure 21-3] Once

you have attained best glide speed, scan the area within

gliding distance for a suitable landing site. Remember

to look behind the aircraft, as well as in front, making

gentle turns, if necessary, to see around the airframe.

When selecting a landing site, you must consider the

wind direction and speed, the size of the landing site,

obstructions to the approach, and the condition of the

surface. A site that allows a landing into the wind and

has a firm, smooth surface with no obstructions is the

most desirable. When considering landing on a road, be

alert for powerlines, signs, and automobile traffic. In

many cases, an ideal site will not be available, and it

will be necessary for you to evaluate your options and

choose the best alternative. For example, if a steady

wind will allow a touchdown with no ground roll, it

may be acceptable to land in a softer field or in a

smaller area than would normally be considered. On

landing, use short or soft field technique, as appropriate, for the site selected. A slightly higher-than-normal

approach airspeed may be required to maintain adequate airflow over the rudder for proper yaw control.

EMERGENCY EQUIPMENT AND

SURVIVAL GEAR

On any flight not in the vicinity of an airport, it is

highly advisable to prepare a survival kit with items

that would be necessary in the event of an emergency.

A properly equipped survival kit should be able to

provide you with sustenance, shelter, medical care, and

a means to summon help without a great deal of effort

on your part. An efficient way to organize your survival

kit is to prepare a basic core of supplies that would be

necessary for any emergency, and allow additional

space for supplementary items appropriate for the

terrain and weather you expect for a particular flight.

The basic items to form the basis of your survival kit

would typically include: a first-aid kit and field

medical guide, a flashlight, water, a knife, matches,

some type of shelter, and a signaling device. Additional

items that may be added to meet the conditions, for

example, would be a lifevest for a flight over water, or

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the gyroplane accompanied with alternating climbs and

descents of the aircraft. PIO is often the result of an

inexperienced pilot overcontrolling the gyroplane, but

this condition can also be induced by gusty wind conditions. While this condition is usually thought of as a

longitudinal problem, it can also happen laterally.

As with most other rotor-wing aircraft, gyroplanes

experience a slight delay between control input and the

reaction of the aircraft. This delay may cause an inexperienced pilot to apply more control input than

required, causing a greater aircraft response than was

desired. Once the error has been recognized, opposite

control input is applied to correct the flight attitude.

Because of the nature of the delay in aircraft response,

it is possible for the corrections to be out of synchronization with the movements of the aircraft and aggravate the undesired changes in attitude. The result is

PIO, or unintentional oscillations that can grow rapidly

in magnitude. [Figure 21-1]

In gyroplanes with an open cockpit and limited flight

instruments, it can be difficult for an inexperienced

pilot to recognize a level flight attitude due to the lack

of visual references. As a result, PIO can develop as the

pilot chases a level flight attitude and introduces climbing and descending oscillations. PIO can also develop

if a wind gust displaces the aircraft, and the control

inputs made to correct the attitude are out of phase with

the aircraft movements. Because the rotor disc angle

decreases at higher speeds and cyclic control becomes

more sensitive, PIO is more likely to occur and can be

more pronounced at high airspeeds. To minimize the

possibility of PIO, avoid high-speed flight in gusty

conditions, and make only small control inputs. After

making a control input, wait briefly and observe the

reaction of the aircraft before making another input. If

PIO is encountered, reduce power and place the cyclic

in the position for a normal climb. Once the oscillations

have stopped, slowly return the throttle and cyclic to

their normal positions. The likelihood of encountering

PIO decreases greatly as experience is gained, and the

ability to subconsciously anticipate the reactions of the

gyroplane to control inputs is developed.

Normal

Flight

Variance from desired

flight path recognized,

control input made

to correct

Gyroplane

reacts

Gyroplane

reacts

Gyroplane

reacts

Overcorrection

recognized, larger

control input made

to correct

Overcorrection recognized,

larger input control made

to correct

Figure 21-1. Pilot-induced oscillation can result if the gyroplane’s reactions to control inputs are not anticipated and become

out of phase.

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BUNTOVER (POWER PUSHOVER)

As you learned in Chapter 16—Gyroplane

Aerodynamics, the stability of a gyroplane is greatly

influenced by rotor force. If rotor force is rapidly

removed, some gyroplanes have a tendency to pitch

forward abruptly. This is often referred to as a forward

tumble, buntover, or power pushover. Removing the

rotor force is often referred to as unloading the rotor,

and can occur if pilot-induced oscillations become

excessive, if extremely turbulent conditions are

encountered, or the nose of the gyroplane is pushed forward rapidly after a steep climb.

A power pushover can occur on some gyroplanes that

have the propeller thrust line above the center of gravity and do not have an adequate horizontal stabilizer. In

this case, when the rotor is unloaded, the propeller

thrust magnifies the pitching moment around the center

of gravity. Unless a correction is made, this nose

pitching action could become self-sustaining and

irreversible. An adequate horizontal stabilizer slows the

pitching rate and allows time for recovery.

Since there is some disagreement between manufacturers as to the proper recovery procedure for this

situation, you must check with the manufacturer of

your gyroplane. In most cases, you need to remove

power and load the rotor blades. Some manufacturers,

especially those with gyroplanes where the propeller

thrust line is above the center of gravity, recommend that

you need to immediately remove power in order to prevent a power pushover situation. Other manufacturers

recommend that you first try to load the rotor blades. For

the proper positioning of the cyclic when loading up the

rotor blades, check with the manufacturer.

When compared to other aircraft, the gyroplane is just

as safe and very reliable. The most important factor, as

in all aircraft, is pilot proficiency. Proper training and

flight experience helps prevent the risks associated

with pilot-induced oscillation or buntover.

GROUND RESONANCE

Ground resonance is a potentially damaging aerodynamic phenomenon associated with articulated rotor

systems. It develops when the rotor blades move out of

phase with each other and cause the rotor disc to

become unbalanced. If not corrected, ground resonance

can cause serious damage in a matter of seconds.

Ground resonance can only occur while the gyroplane

is on the ground. If a shock is transmitted to the rotor

system, such as with a hard landing on one gear or

when operating on rough terrain, one or more of the

blades could lag or lead and allow the rotor system’s

center of gravity to be displaced from the center of rotation. Subsequent shocks to the other gear aggravate the

imbalance causing the rotor center of gravity to rotate

around the hub. This phenomenon is not unlike an outof-balance washing machine. [Figure 21-2]

To reduce the chance of experiencing ground resonance, every preflight should include a check for

proper strut inflation, tire pressure, and lag-lead

damper operation. Improper strut or tire inflation can

change the vibration frequency of the airframe, while

improper damper settings change the vibration frequency of the rotor.

If you experience ground resonance, and the rotor

r.p.m. is not yet sufficient for flight, apply the rotor

brake to maximum and stop the rotor as soon as possible. If ground resonance occurs during takeoff, when

rotor r.p.m. is sufficient for flight, lift off immediately.

Ground resonance cannot occur in flight, and the rotor

blades will automatically realign themselves once the

gyroplane is airborne. When prerotating the rotor system prior to takeoff, a slight vibration may be felt that

is a very mild form of ground resonance. Should this

oscillation amplify, discontinue the prerotation and

apply maximum rotor brake.

帅哥

bring the aircraft safely to a stop. This value changes

for a given aircraft based on atmospheric conditions,

the takeoff surface, aircraft weight, and other factors

affecting performance. Knowing the accelerate/stop

value for your gyroplane can be helpful in planning a

safe takeoff, but having this distance available does not

necessarily guarantee a safe aborted takeoff is possible

for every situation. If the decision to abort is made after

liftoff, for example, the gyroplane will require considerably more distance to stop than the accelerate/stop

figure, which only considers the ground roll requirement. Planning a course of action for an abort decision

at various stages of the takeoff is the best way to ensure

the gyroplane can be brought safely to a stop should the

need arise.

For a gyroplane without a flight manual or other published performance data, the accelerate/stop distance

can be reasonably estimated once you are familiar with

the performance and takeoff characteristics of the aircraft. For a more accurate figure, you can accelerate the

gyroplane to takeoff speed, then slow to a stop, and

note the distance used. Doing this several times gives

you an average accelerate/stop distance. When performance charts for the aircraft are available, as in the

flight manual of a certificated gyroplane, accurate

accelerate/stop distances under various conditions can

be determined by referring to the ground roll information contained in the charts.

LIFT-OFF AT LOW AIRSPEED AND

HIGH ANGLE OF ATTACK

Because of ground effect, your gyroplane might be able

to become airborne at an airspeed less than minimum

level flight speed. In this situation, the gyroplane is flying well behind the power curve and at such a high

angle of attack that unless a correction is made, there

will be little or no acceleration toward best climb

speed. This condition is often encountered in

gyroplanes capable of jump takeoffs. Jumping without

sufficient rotor inertia to allow enough time to accelerate through minimum level flight speed, usually results

in your gyroplane touching down after liftoff. If you do

touch down after performing a jump takeoff, you

should abort the takeoff.

During a rolling takeoff, if the gyroplane is forced into

the air too early, you could get into the same situation.

It is important to recognize this situation and take

immediate corrective action. You can either abort the

takeoff, if enough runway exists, or lower the nose and

21-2

accelerate to the best climb speed. If you choose to continue the takeoff, verify that full power is applied, then,

slowly lower the nose, making sure the gyroplane does

not contact the surface. While in ground effect, accelerate to the best climb speed. Then, adjust the nose pitch

attitude to maintain that airspeed.

COMMON ERRORS

The following errors might occur when practicing a

lift-off at a low airspeed.

1. Failure to check rotor for proper operation, track,

and r.p.m. prior to initiating takeoff.

2. Use of a power setting that does not simulate a

“behind the power curve” situation.

3. Poor directional control.

4. Rotation at a speed that is inappropriate for the

maneuver.

5. Poor judgement in determining whether to abort

or continue takeoff.

6. Failure to establish and maintain proper climb

attitude and airspeed, if takeoff is continued.

7. Not maintaining the desired ground track during

the climb.

PILOT-INDUCED OSCILLATION (PIO)

Pilot-induced oscillation, sometimes referred to as porpoising, is an unintentional up-and-down oscillation of