Part 7: FAA… | FAA Helicopter Flying…

11-18

ensure that the nose does not continue yawing to the right. If

a go-around is required, increasing the collective too much or

too rapidly with airspeeds below translational lift may cause

a rapid spinning to the right.

Once the helicopter has landed and is sliding/rolling to a

stop, the heading can be controlled with a combination of

collective, cyclic and throttle. To turn the nose to the right,

raise the collective or apply aft cyclic. The throttle may be

increased as well if it is not in the full open position. To turn

the nose to the left, lower the collective or apply forward

cyclic. The throttle may be decreased as well if it is not

already at flight idle.

Loss of Tail Rotor Effectiveness (LTE)

Loss of tail rotor effectiveness (LTE) or an unanticipated

yaw is defined as an uncommanded, rapid yaw towards the

advancing blade which does not subside of its own accord.

It can result in the loss of the aircraft if left unchecked. It is

very important for pilots to understand that LTE is caused

by an aerodynamic interaction between the main rotor and

tail rotor and not caused from a mechanical failure. Some

helicopter types are more likely to encounter LTE due to the

normal certification thrust produced by having a tail rotor

that, although meeting certification standards, is not always

able to produce the additional thrust demanded by the pilot.

A helicopter is a collection of compromises. Compare the

size of an airplane propeller to that of a tail rotor. Then,

consider the horsepower required to run the propeller. For

example, a Cessna 172P is equipped with a 160-horsepower

(HP) engine. A Robinson R-44 with a comparably sized tail

rotor is rated for a maximum of 245 HP. If you assume the

tail rotor consumes 50 HP, only 195 HP remains to drive

the main rotor. If the pilot were to apply enough collective

to require 215 HP from the engine, and enough left pedal to

require 50 HP for the tail rotor, the resulting engine overload

would lead to one of two outcomes: slow down (reduction

in rpm) or premature failure. In either outcome, antitorque

would be insufficient and total lift might be less than needed

to remain airborne.

Every helicopter design requires some type of antitorque

system to counteract main rotor torque and prevent spinning

once the helicopter lifts off the ground. A helicopter is heavy,

and the powerplant places a high demand on fuel. Weight

penalizes performance, but all helicopters must have an

antitorque system, which adds weight. Therefore, the tail

rotor is certified for normal flight conditions. Environmental

forces can overwhelm any aircraft, rendering the inherently

unstable helicopter especially vulnerable.

As with any aerodynamic condition, it is very important for

pilots to not only to understand the definition of LTE, but

more importantly, how and why it happens, how to avoid

it, and lastly, how to correct it once it is encountered. We

must first understand the capabilities of the aircraft or even

better what it is not capable of doing. For example, if you

were flying a helicopter with a maximum gross weight of

5,200 lb, would you knowingly try to take on fuel, baggage

and passengers causing the weight to be 5,500 lb? A wise

professional pilot should not ever exceed the certificated

maximum gross weight or performance flight weight for any

aircraft. The manuals are written for safety and reliability.

The limitations and emergency procedures are stressed

because lapses in procedures or exceeding limitations can

result in aircraft damage or human fatalities. At the very least,

exceeding limitations will increase the costs of maintenance

and ownership of any aircraft and especially helicopters.

Overloaded parts may fail before their designed lifetime. There

are no extra parts in helicopters. The respect and discipline

pilots exercise in following flight manuals should also be

applied to understanding aerodynamic conditions. If flight

envelopes are exceeded, the end results can be catastrophic.

LTE is an aerodynamic condition and is the result of a control

margin deficiency in the tail rotor. It can affect all single-rotor

helicopters that utilize a tail rotor. The design of main and

tail rotor blades and the tail boom assembly can affect the

characteristics and susceptibility of LTE but will not nullify

the phenomenon entirely. Translational lift is obtained by

any amount of clean air through the main rotor disk. Chapter

2, Aerodynamics of Flight, discusses translational lift with

respect to the main rotor blade, explaining that the more

clean air there is going through the rotor disk, the more

efficient it becomes. The same holds true for the tail rotor.

As the tail rotor works in less turbulent air, it reaches a point

of translational thrust. At this point, the tail rotor becomes

aerodynamically efficient and the improved efficiency

produces more antitorque thrust. The pilot can determine

when the tail rotor has reached translational thrust. As more

antitorque thrust is produced, the nose of the helicopter

yaws to the left (opposite direction of the tail rotor thrust),

forcing the pilot to correct with right pedal application

(actually decreasing the left pedal). This, in turn, decreases

the AOA in the tail rotor blades. Pilots should be aware of the

characteristics of the helicopter they fly and be particularly

aware of the amount of tail rotor pedal typically required for

different flight conditions.

LTE is a condition that occurs when the flow of air through

a tail rotor is altered in some way, by altering the angle or

speed at which the air passes through the rotating blades of

the tail rotor disk. As discussed in the previous paragraph, an

effective tail rotor relies on a stable and relatively undisturbed

11-19

0°

30°

60°

90°

120°

150°

180°

210°

240°

270°

300°

330°

Region of disk

vortex interference

10 knots

360°

15 knots 20 knots

315°

285°

Wind

Figure 11-9. Main rotor disk vortex interference.

Region of possible yaw introduction by weathercock stability

0°

30°

60°

90°

120°

150°

180°

210°

240°

270°

300°

330°

10 knots

360°

5 knots

15 knots

17 knots

Wind

Figure 11-10. Weathercock stability.

airflow in order to provide a steady and constant antitorque

reaction. The pitch and AOA of the individual blades will

determine the thrust. A change to either of these alters the

amount of thrust generated. A pilot’s yaw pedal input causes

a thrust reaction from the tail rotor. Altering the amount of

thrust delivered for the same yaw input creates an imbalance.

Taking this imbalance to the extreme will result in the loss

of effective control in the yawing plane, and LTE will occur.

This alteration of tail rotor thrust can be affected by numerous

external factors. The main factors contributing to LTE are:

1. Airflow and downdraft generated by the main rotor

blades interfering with the airflow entering the tail

rotor assembly.

2. Main blade vortices developed at the main blade tips

entering the tail rotor disk.

3. Turbulence and other natural phenomena affecting the

airflow surrounding the tail rotor.

4. A high-power setting, hence large main rotor

pitch angle, induces considerable main rotor blade

downwash and hence more turbulence than when the

helicopter is in a low power condition.

5. A slow forward airspeed, typically at speeds where

translational lift and translational thrust are in the

process of change and airflow around the tail rotor

will vary in direction and speed.

6. The airflow relative to the helicopter;

a. Worst case—relative wind within ±15° of the

10 o’clock position, generating vortices that

can blow directly into the tail rotor. This is

dictated by the characteristics of the helicopters

aerodynamics of tailboom position, tail rotor size

and position relative to the main rotor and vertical

stabilizer, size and shape. [Figure 11-9]

b. Weathercock stability—tailwinds from 120° to

240° [Figure 11-10] , such as left crosswinds,

causing high pilot workload.

c. Tail rotor vortex ring state (210° to

330°). [Figure 11-11] Winds within this region

will result in the development of the vortex ring

state of the tail rotor.

7. Combinations (a, b, c) of these factors in a particular

situation can easily require more antitorque than the

helicopter can generate and in a particular environment

LTE can be the result.

Certain flight activities lend themselves to being at higher

risk of LTE than others. For example, power line and pipeline

patrol sectors, low speed aerial filming/photography as well

as in the Police and Helicopter Emergency Medical Services

(EMS) environments can find themselves in low-and-slow

situations over geographical areas where the exact wind speed

and direction are hard to determine.

11-20

0°

30°

60°

90°

120°

150°

180°

210°

240°

270°

300°

330°

Region of roughness due to tail rotor vortex ring state

10 knots

360°

5 knots

15 knots

17 knots

Wind

Figure 11-11. Tail rotor vortex ring state.

Unfortunately, the aerodynamic conditions that a helicopter

is susceptible to are not explainable in black and white terms.

LTE is no exception. There are a number of contributing

factors, but what is more important in preventing LTE is to

note them, and then to associate them with situations that

should be avoided. Whenever possible, pilots should learn

to avoid the following combinations:

1. Low and slow flight outside of ground effect.

2. Winds from ±15º of the 10 o’clock position and

probably on around to 5 o’clock position [Figure 11-9]

3. Tailwinds that may alter the onset of translational lift

and translational thrust, and hence induce high power

demands and demand more anti-torque (left pedal)

than the tail rotor can produce.

4. Low speed downwind turns.

5. Large changes of power at low airspeeds.

6. Low speed flight in the proximity of physical

obstructions that may alter a smooth airflow to both

the main rotor and tail rotor.

Pilots who put themselves in situations where the combinations

above occur should know that they are likely to encounter

LTE. The key is not to put the helicopter in a compromising

condition, while at the same time being educated enough

to recognize the onset of LTE and being prepared to react

quickly to it before the helicopter cannot be controlled.

Early detection of LTE, followed by the immediate flight

control application of corrective action, applying forward

cyclic to regain airspeed, applying right pedal not left as

necessary to maintain rotor rpm, and reducing the collective

(thus reducing the high-power demand on the tail rotor), is the

key to a safe recovery. Pilots should always set themselves

up when conducting any maneuver to have enough height

and space available to recover in the event they encounter

an aerodynamic situation such as LTE.

Understanding the aerodynamic phenomenon of LTE is by

far the most important factor in preventing an LTE-related

accident, and maintaining the ability and option either to go

around if making an approach or pull out of a maneuver safely

and re-plan, is always the safest option. Having the ability to

fly away from a situation and re-think the possible options

should always be part of a pilot's planning process in all phases

of flight. Unfortunately, there have been many pilots who

have idled a good engine and fully functioning tail rotor disk

and autorotated a perfectly airworthy helicopter to the crash

site because they misunderstood or misperceived both the

limitations of the helicopter and the aerodynamic situation.

Main Rotor Disk Interference (285–315°)

Refer to Figure 11-9. Winds at velocities of 10–30 knots from

the left front cause the main rotor vortex to be blown into the

tail rotor by the relative wind. This main rotor disk vortex

causes the tail rotor to operate in an extremely turbulent

environment. During a right turn, the tail rotor experiences a

reduction of thrust as it comes into the area of the main rotor

disk vortex. The reduction in tail rotor thrust comes from the

airflow changes experienced at the tail rotor as the main rotor

disk vortex moves across the tail rotor disk.

The effect of the main rotor disk vortex initially increases the

AOA of the tail rotor blades, thus increasing tail rotor thrust.

The increase in the AOA requires that right pedal pressure

be added to reduce tail rotor thrust in order to maintain the

same rate of turn. As the main rotor vortex passes the tail

rotor, the tail rotor AOA is reduced. The reduction in the

AOA causes a reduction in thrust and right yaw acceleration

begins. This acceleration can be surprising, since previously

adding right pedal to maintain the right turn rate. This thrust

reduction occurs suddenly, and if uncorrected, develops

into an uncontrollable rapid rotation about the mast. When

operating within this region, be aware that the reduction in

tail rotor thrust can happen quite suddenly, and be prepared

to react quickly to counter this reduction with additional left

pedal input.

Weathercock Stability (120–240°)

In this region, the helicopter attempts to weathervane,

or weathercock, its nose into the relative wind.

[Figure 11-10] Unless a resisting pedal input is made, the

helicopter starts a slow, uncommanded turn either to the right

11-21

or left, depending upon the wind direction. If the pilot allows

a right yaw rate to develop and the tail of the helicopter moves

into this region, the yaw rate can accelerate rapidly. In order

to avoid the onset of LTE in this downwind condition, it is

imperative to maintain positive control of the yaw rate and

devote full attention to flying the helicopter.

Tail Rotor Vortex Ring State (210–330°)

Winds within this region cause a tail rotor vortex ring state to

develop. [Figure 11-11] The result is a nonuniform, unsteady

flow into the tail rotor. The vortex ring state causes tail

rotor thrust variations, which result in yaw deviations. The

net effect of the unsteady flow is an oscillation of tail rotor

thrust. Rapid and continuous pedal movements are necessary

to compensate for the rapid changes in tail rotor thrust when

hovering in a left crosswind. Maintaining a precise heading

in this region is difficult, but this characteristic presents

no significant problem unless corrective action is delayed.

However, high pedal workload, lack of concentration, and

overcontrolling can lead to LTE.

When the tail rotor thrust being generated is less than the

thrust required, the helicopter yaws to the right. When

hovering in left crosswinds, concentrate on smooth pedal

coordination and do not allow an uncommanded right yaw to

develop. If a right yaw rate is allowed to build, the helicopter

can rotate into the wind azimuth region where weathercock

stability then accelerates the right turn rate. Pilot workload

during a tail rotor vortex ring state is high. Do not allow a

right yaw rate to increase.

LTE at Altitude

At higher altitudes where the air is thinner, tail rotor thrust

and efficiency are reduced. Because of the high-density

altitude, powerplants may be much slower to respond to

power changes. When operating at high altitudes and high

gross weights, especially while hovering, the tail rotor thrust

may not be sufficient to maintain directional control, and

LTE can occur. In this case, the hovering ceiling is limited

by tail rotor thrust and not necessarily power available. In

these conditions, gross weights need to be reduced and/

or operations need to be limited to lower density altitudes.

This may not be noted as criteria on the performance charts.

Reducing the Onset of LTE

To help reduce the onset of LTE, follow these steps:

1. Maintain maximum power-on rotor rpm. If the main

rotor rpm is allowed to decrease, the antitorque thrust

available is decreased proportionally.

2. Avoid tailwinds below airspeeds of 30 knots. If loss

of translational lift occurs, it results in an increased

power demand and additional antitorque pressures.

3. Avoid OGE operations and high-power demand

situations below airspeeds of 30 knots at low altitudes.

4. Be especially aware of wind direction and velocity

when hovering in winds of about 8–12 knots. A loss

of translational lift results in an unexpected high power

demand and an increased antitorque requirement.

5. Be aware that if a considerable amount of left pedal

is being maintained, a sufficient amount of left pedal

may not be available to counteract an unanticipated

right yaw.

6. Be alert to changing wind conditions, which may be

experienced when flying along ridge lines and around

buildings.

7. Execute right turns slowly. This limits the effects of

rotating inertia, and decreases loading on the tailrotor

to control yawing.

Recovery Technique (Uncontrolled Right Yaw)

If a sudden unanticipated right yaw occurs, the following

recovery technique should be performed. Apply full left

pedal. Simultaneously, apply forward cyclic control to

increase speed. If altitude permits, reduce power. As recovery

is affected, adjust controls for normal forward flight. A

recovery path must always be planned, especially when

terminating to an OGE hover and executed immediately if

an uncommanded yaw is evident.

Collective pitch reduction aids in arresting the yaw rate but

may cause an excessive rate of descent. Any large, rapid

increase in collective to prevent ground or obstacle contact

may further increase the yaw rate and decrease rotor rpm.

The decision to reduce collective must be based on the pilot’s

assessment of the altitude available for recovery.

If the rotation cannot be stopped and ground contact is

imminent, an autorotation may be the best course of action.

Maintain full left pedal until the rotation stops, then adjust to

maintain heading. For more information on LTE, see Advisory

Circular (AC) 90-95, Unanticipated Right Yaw in Helicopters.

Main Drive Shaft or Clutch Failure

The main drive shaft, located between the engine and the main

rotor transmission, provides engine power to the main rotor

transmission. In some helicopters, particularly those with

piston engines, a drive belt is used instead of a drive shaft.

A failure of the drive shaft clutch or belt has the same effect

as an engine failure because power is no longer provided to

the main rotor and an autorotation must be initiated. There

are a few differences, however, that need to be taken into

11-22

consideration. If the drive shaft or belt breaks, the lack of any

load on the engine results in an overspeed. In this case, the

throttle must be closed in order to prevent any further damage.

In some helicopters, the tail rotor drive system continues to

be powered by the engine even if the main drive shaft breaks.

In this case, when the engine unloads, a tail rotor overspeed

can result. If this happens, close the throttle immediately and

enter an autorotation. The pilot must be knowledgeable of the

specific helicopter’s system and failure modes.

Pilots should keep in mind that when there is any suspected

mechanical malfunction, first and foremost they should

always attempt to maintain rotor rpm. If the rotor rpm is at the

normal indication with normal power settings, an instrument

failure might be occurring, and it would be best to fly the

helicopter to a safe landing area. If the rotor rpm is in fact

decreasing or low, then there is a drive line failure.

Hydraulic Failure

Many helicopters incorporate the use of hydraulic actuators to

overcome high control forces. A hydraulic system consists of

actuators, also called servos, on each flight control; a pump,

which is usually driven by the main rotor transmission;

and a reservoir to store the hydraulic fluid. A switch in the

cockpit can turn the system off, although it is left on during

normal conditions. A pressure indicator in the cockpit may

be installed to monitor the system.

An impending hydraulic failure can be recognized by a

grinding or howling noise from the pump or actuators,

increased control forces and feedback, and limited control

movement. The required corrective action is stated in detail

in the RFM. In most cases, airspeed needs to be reduced in

order to reduce control forces. The hydraulic switch and

circuit breaker should be checked and recycled. If hydraulic

power is not restored, make a shallow approach to a running

or roll-on landing. This technique is used because it requires

less control force and pilot workload. Additionally, the

hydraulic system should be disabled by placing the switch

in the off position. The reason for this is to prevent an

inadvertent restoration of hydraulic power, which may lead

to overcontrolling near the ground.

In those helicopters in which the control forces are so high

that they cannot be moved without hydraulic assistance, two

or more independent hydraulic systems are installed. Some

helicopters use hydraulic accumulators to store pressure that

can be used for a short time while in an emergency if the

hydraulic pump fails. This gives enough time to land the

helicopter with normal control.

Governor or Fuel Control Failure

Governors and fuel control units automatically adjust engine

power to maintain rotor rpm when the collective pitch

is changed. If the governor or fuel control unit fails, any

change in collective pitch requires manual adjustment of

the throttle to maintain correct rpm. In the event of a high

side failure, the engine and rotor rpm tend to increase above

the normal range due to the engine being commanded to

put out too much power. If the rpm cannot be reduced and

controlled with the throttle, close the throttle and enter an

autorotation. If the failure is on the low side, the engine

output is allowed to go below the collective and normal

rpm may not be attainable, even if the throttle is manually

controlled. In this case, the collective has to be lowered to

maintain rotor rpm. A running or roll-on landing may be

performed if the engine can maintain sufficient rotor rpm. If

there is insufficient power, enter an autorotation. As stated

previously in this chapter, before responding to any type of

mechanical failure, pilots should confirm that rotor rpm is

not responding to flight control inputs. If the rotor rpm can

be maintained in the green operating range, the failure is in

the instrument, and not mechanical.

Abnormal Vibration

With the many rotating parts found in helicopters, some

vibration is inherent. A pilot needs to understand the

cause and effect of helicopter vibrations because abnormal

vibrations cause premature component wear and may even

result in structural failure. With experience, a pilot learns

what vibrations are normal and those that are abnormal

and can then decide whether continued flight is safe or not.

Helicopter vibrations are categorized into low, medium, or

high frequency.

Low-Frequency Vibrations

Low-frequency vibrations (100–500 cycles per minute) usually

originate from the main rotor disk. The main rotor operational

range, depending on the helicopter, is usually between 320

and 500 rpm. A rotor blade that is out of track or balance will

cause a cycle to occur with every rotation. The vibration may

be felt through the controls, the airframe, or a combination

of both. The vibration may also have a definite direction

of push or thrust. It may be vertical, lateral, horizontal, or

even a combination of these. Normally, the direction of the

vibration can be determined by concentrating on the feel of

the vibration, which may push a pilot up and down, backwards

and forwards, or in the case of a blade being out of phase, from

side to side. The direction of the vibration and whether it is

felt in the controls or the airframe is important information for

the mechanic when he or she troubleshoots the source. Out-

of-track or out-of-balance main rotor blades, damaged blades,

11-23

worn bearings, dampers out of adjustment, or worn parts are

possible causes of low frequency vibrations.

Medium- and High-Frequency Vibrations

Medium-frequency vibrations (1,000–2,000 cycles per

minute) range between the low frequencies of the main rotor

(100–500 cycles per minute) and the high frequencies (2,100

cycles per minute or higher) of the engine and tail rotor.

Depending on the helicopter, medium-frequency vibration

sources may be engine and transmission cooling fans, and

accessories such as air conditioner compressors, or driveline

components. Medium-frequency vibrations are felt through

the entire airframe, and prolonged exposure to the vibrations

will result in greater pilot fatigue.

Most tail rotor vibrations fall into the high-frequency range

(2,100 cycles per minute or higher) and can be felt through

the tail rotor pedals as long as there are no hydraulic actuators

to dampen out the vibration. This vibration is felt by the pilot

through his or her feet, which are usually “put to sleep” by

the vibration. The tail rotor operates at approximately a 6:1

ratio with the main rotor, meaning for every one rotation

of the main rotor the tail rotor rotates 6 times. A main

rotor operating rpm of 350 means the tail rotor rpm would

be 2,100 rpm. Any imbalance in the tail rotor disk is very

harmful as it can cause cracks to develop and rivets to work

loose. Piston engines usually produce a normal amount of

high-frequency vibration, which is aggravated by engine

malfunctions, such as spark plug fouling, incorrect magneto

timing, carburetor icing and/or incorrect fuel/air mixture.

Vibrations in turbine engines are often difficult to detect as

these engines operate at a very high rpm. Turbine engine

vibration can be at 30,000 rpm internally, but common

transmission speeds are in the 1,000 to 3,000 rpm range for

the output shaft. The vibrations in turbine engines may be

short lived as the engine disintegrates rapidly when damaged

due to high rpm and the forces present.

Tracking and Balance

Modern equipment used for tracking and balancing the main

and tail rotor blades can also be used to detect other vibrations

in the helicopter. These systems use accelerometers mounted

around the helicopter to detect the direction, frequency, and

intensity of the vibration. The built-in software can then

analyze the information, pinpoint the origin of the vibration,

and suggest the corrective action.

The use of a system such as a health and usage monitoring

system (HUMS) provides the operator the ability to record

engine and transmission performance and provide rotor track

and balance. This system has been around for over 30 years

and is now becoming more affordable, more capable, and

more commonplace in the rotorcraft industry.

Multiengine Emergency Operations

Single-Engine Failure

When one engine has failed, the helicopter can often maintain

altitude and airspeed until a suitable landing site can be

selected. Whether or not this is possible becomes a function

of such combined variables as aircraft weight, density

altitude, height above ground, airspeed, phase of flight,

and single-engine capability. Environmental response time

and control technique may be additional factors. Caution

must be exercised to correctly identify the malfunctioning

engine since there is no telltale yawing as occurs in most

multiengine airplanes. Shutting down the wrong engine

could be disastrous!

Even when flying multiengine powered helicopters, rotor rpm

must be maintained at all costs, because fuel contamination has

been documented as the cause for both engines failing in flight.

Dual-Engine Failure

The flight characteristics and the required crew member

control responses after a dual-engine failure are similar to

those during a normal power-on descent. Full control of the

helicopter can be maintained during autorotational descent.

In autorotation, as airspeed increases above 70–80 KIAS, the

rate of descent and glide distance increase significantly. As

airspeed decreases below approximately 60 KIAS, the rate

of descent increases and glide distance decreases.

Lost Procedures

Pilots become lost while flying for a variety of reasons, such

as disorientation, flying over unfamiliar territory, or visibility

that is low enough to render familiar terrain unfamiliar. When

a pilot becomes lost, the first order of business is to fly the

aircraft; the second is to implement lost procedures. Keep

in mind that the pilot workload will be high, and increased

concentration will be necessary. If lost, always remember to

look for the practically invisible hazards, such as wires, by

searching for their support structures, such as poles or towers,

which are almost always near roads.

If lost, follow common sense procedures.

• Try to locate any large landmarks, such as lakes, rivers,

towers, railroad tracks, or Interstate highways. If a

landmark is recognized, use it to find the helicopter’s

location on the sectional chart. If flying near a town or

city, a pilot may be able to read the name of the town

on a water tower or even land to ask for directions.

• If no town or city is nearby, the first thing a pilot should

do is climb. An increase in altitude increases radio and

navigation reception range as well as radar coverage.

11-24

risk associated with being lost is waiting too long to land in a

safe area. Helicopter pilots should land before fuel exhaustion

occurs because maneuvering with low fuel levels could cause

the engine to stop due to fuel starvation as fuel sloshes or

flows away from the pickup port in the tank.

If lost and low on fuel, it is advisable to make a precautionary

landing. Preferably, land near a road or in an area that would

allow space for another helicopter to safely land and provide

assistance. Having fuel delivered is a minor inconvenience

when compared to having an accident. Once on the ground,

pilots may seek assistance.

VFR Flight into Instrument Meteorological

Conditions

Helicopters, unlike airplanes, generally operate under Visual

Flight Rules (VFR) and require pilots to maintain aircraft

control by visual cues. However, when unforecast weather

leads to degraded visibility, the pilot may be at increased

risk of Inadvertent flight into Instrument Meteorological

Conditions (IIMC). During an IIMC encounter, the pilot

may be unprepared for the loss of visual reference, resulting

in a reduced ability to continue safe flight. IIMC is a life-

threatening emergency for any pilot. To capture these IIMC

events, the Commercial Aviation Safety Team (CAST) and

International Civil Aviation Organization (ICAO) Common

Taxonomy Team (CICTT) categorizes this occurrence as

Unintended flight in Instrument Meteorological Conditions

(UIMC). This term is also recognized by the National

Transportation Safety Board (NTSB) and Federal Aviation

Administration (FAA). It is used to classify occurrences

(accidents and incidents) at a high level to improve the

capacity to focus on common safety issues and complete

analysis of the data in support of safety initiatives.

The onset of IIMC may occur gradually or suddenly, has

no simple procedural exit, and is unlike flight training by

reference to while in Visual Meteorological Conditions

(VMC). Most training helicopters are not equipped or

certified to fly under Instrument Flight Rules (IFR).

Therefore, General Aviation (GA) helicopter pilots may not

have the benefit of flight in actual Instrument Meteorological

Conditions (IMC) during their flight training. Helicopter

pilots that encounter IIMC may experience physiological

illusions which can lead to spatial disorientation and loss of

aircraft control. Even with some instrument training, many

available and accessible helicopters are not equipped with

the proper augmented safety systems or autopilots, which

would significantly aid in helicopter control during an

IIMC emergency. The need to use outside visual references

is natural for helicopter pilots because much of their flight

training is based upon visual cues, not on flight instruments.

This primacy can only be overcome through significant

instrument training. Additionally, instrument flight may be

• Navigation aids, dead reckoning, and pilotage are

skills that can be used as well.

• Do not forget air traffic control (ATC)—controllers

assist pilots in many ways, including finding a lost

helicopter. Once communication with ATC has been

established, follow their instructions.

These common-sense procedures can be easily remembered by

using the four Cs: Climb, Communicate, Confess, and Comply.

• Climb for a better view, improved communication and

navigation reception, and terrain avoidance.

• Communicate by calling the nearest flight service

station (FSS)/automated flight service station (AFSS)

on 122.2 MHz. If the FSS/AFSS does not respond,

call the nearest control tower, center, or approach

control. For frequencies, check the chart in the vicinity

of the last known position. If that fails, switch to

the emergency radio frequency (121.5 MHz) and

transponder code (7700).

• Report the lost situation to ATC and request help.

• Comply with controller instructions.

Pilots should understand the services provided by ATC and

the resources and options available. These services enable

pilots to focus on aircraft control and help them make better

decisions in a time of stress.

When contacting ATC, pilots should provide as much

information as possible because ATC uses the information

to determine what kind of assistance it can provide with

available assets and capabilities. Information requirements

vary depending on the existing situation, but at a minimum

a pilot should provide the following information:

• Aircraft identification and type

• Nature of the emergency

• Aviator’s desires

To reduce the chances of getting lost in the first place, use

flight following through active contact with an aircraft during

flight either by radio or through automated flight following

systems when it is available, monitor checkpoints no more

than 25 miles apart, keep navigation aids such as Very

High-Frequency Omni-Directional Range (VOR) tuned in,

and maintain good situational awareness. Flight following

provides ongoing surveillance information to assist pilots in

avoiding collisions with other aircraft.

Getting lost is a potentially dangerous situation for any

aircraft, especially when low on fuel. Due to the helicopter’s

unique ability to land almost anywhere, pilots have more

flexibility than other aircraft as to landing site. An inherent

11-25

intimidating to some and too costly for others. As a result,

many helicopter pilots choose not to seek an instrument

rating.

While commercial helicopter operators often prefer their

pilots to be instrument rated, fatal accidents still occur as

a result of IIMC. Many accidents can be traced back to

the pilot’s inability to recover the helicopter after IIMC

is encountered, even with adequate equipment installed.

Therefore, whether instrument rated or not, all pilots should

understand that avoiding IIMC is critical.

A good practice for any flight is to set and use personal

minimums, which should be more conservative than those

required by regulations for VFR flight. In addition, a thorough

preflight and understanding of weather conditions that may

contribute to the risk of IMC developing along a planned

route of flight is essential for safety. Pilots should recognize

deteriorating weather conditions so the route of flight can be

changed or a decision made to terminate the flight and safely

land at a suitable area, well before IIMC occurs. If weather

conditions deteriorate below the pilot’s personal minimums

during flight, a pilot who understands the risks of IIMC

knows that he or she is at an en route decision point, where

it is necessary to either turn back to the departure point or

immediately land somewhere safe to wait until the weather

has cleared. Pilots should recognize that descent below a

predetermined minimum altitude above ground level (AGL)

(for example, 500 feet AGL) to avoid clouds or, slowing

the helicopter to a predetermined minimum airspeed (for

example, slowing to 50 KIAS) to reduce the rate of closure

from the deteriorating weather conditions, indicates the

decision point had been reached. Ceilings that are lower than

reported and/or deteriorating visibility along the route of

flight should trigger the decision to discontinue and amend

the current route to avoid IIMC.

If the helicopter pilot is instrument rated, it is advisable to

maintain instrument currency and proficiency as this may

aid the pilot in a safe recovery from IIMC. A consideration

for instrument rated pilots when planning a VFR flight

should include a review of published instrument charts for

safe operating altitudes, e.g. minimum safe altitude (MSA),

minimum obstruction clearance altitude (MOCA), minimum

in VMC throughout a flight: off-route altitude (MORA),

etc. If IIMC occurs, the pilot may consider a climb to a safe

altitude. Once the helicopter is stabilized, the pilot should

declare an emergency with air traffic control (ATC). It is

imperative that the pilot commit to controlling the helicopter

and remember to aviate, navigate, and finally communicate.

Often communication is attempted first, as it is natural to

look for help in stressful situations. This may distract the

pilot from maintaining control of the helicopter.

If the pilot is not instrument rated, instrument current nor

proficient, or is flying a non-IFR equipped helicopter,

remaining in VMC is paramount. Pilots who are not trained

or proficient in flight solely by reference to instruments have

a tendency to attempt to maintain flight by visual ground

reference, which tends to result in flying at lower altitudes,

just above the trees or by following roads. The thought process

is that, "as long as I can see what is below me, I can continue

to my intended destination." Experience and statistical data

indicate that attempting to continue VFR flight into IMC can

often lead to a fatal outcome as pilots often fixate on what

they see below them and are unable to see the hazards ahead

of them (e.g., power lines, towers, rising terrain, etc.). By

the time the pilot sees the hazard, it is either too late to avoid

a collision, or while successfully maneuvering to avoid an

obstacle, the pilot becomes disoriented.

Flying at night involves even more conservative personal

minimums to ensure safety and avoidance of IIMC than

daytime flying. At night, deteriorating weather conditions

may be difficult to detect. Therefore, pilots should ensure

that they not only receive a thorough weather briefing, but

that they remain vigilant for unforecasted weather during

their flight. The planned route should include preselected

landing sites that will provide options to the pilot in the

event a precautionary landing is required to avoid adverse

weather conditions. As a pilot gains night flight experience

their ability to assess weather during a flight will improve.

Below are some basic guidelines to assist a pilot to remain

in VMC throughout a flight:

1. Slowly turn around if threatened by deteriorating

visual cues and proceed back to VMC or to the first

safe landing area if the weather ahead becomes

questionable. Remember that prevention is paramount.

2. Do not proceed further on a course when the terrain

ahead is not clearly discernible.

3. Delay or consider cancelling the flight if weather

conditions are already questionable, could deteriorate

significantly based on forecasts, or if you are uncertain

whether the flight can be conducted safely. Often, a

gut feeling can provide a warning that unreasonable

risks are present.

4. Always have a safe landing area (such as large open

areas or airports) in mind for every route of flight.

There are five basic steps that every pilot should be familiar

with, and which should be executed immediately at the onset

of IIMC, if applicable. However, remember that if you are

not trained to execute the following maneuvers solely by

reference to instruments, or your aircraft is not equipped

11-26

Food cannot be subject to deterioration due to heat or cold. There

should be at least 10,000 calories for each person on board, and it

should be stored in a sealed waterproof container. It should have

been inspected within the previous 6 months, verifying the amount

and satisfactory condition of the contents.

A supply of water

Cooking utensils

Matches in a waterproof container

A portable compass

An ax weighing at least 2.5 pounds with a handle not less than 28 inches

in length

A flexible saw blade or equivalent cutting tool

30 feet of snare wire and instructions for use

Fishing equipment, including still-fishing bait and gill net with not more

than a two-inch mesh

Mosquito nets or netting and insect repellent sufficient to meet the

needs of all persons aboard, when operating in areas where insects

are likely to be hazardous

A signaling mirror

At least three pyrotechnic distress signals

A sharp, quality jackknife or hunting knife

A suitable survival instruction manual

Flashlight with spare bulbs and batteries

Portable emergency locator transmitter (ELT) with spare batteries

Stove with fuel or a self-contained means of providing heat for cooking

Tent(s) to accommodate everyone on board

Additional items for winter operations:

• Winter sleeping bags for all persons when the

temperature is expected to be below 7 °C

• Two pairs of snow shoes

• Spare ax handle

• Ice chisel

• Snow knife or saw knife

EMERGENCY EQUIPMENT AND SURVIVAL GEAR

Figure 11-12. Emergency equipment and survival gear.

with such instruments, this guidance may be less beneficial

to you and loss of helicopter control may occur:

1. Level the “wings” – level the bank angle using the

attitude indicator.

2. Attitude – set a climb attitude that achieves a safe

climb speed appropriate to your type of helicopter.

This is often no more than 10° of pitch up on the

attitude indicator.

3. Airspeed – verify that the attitude selected has

achieved the desired airspeed. It is critical to

recognize that slower airspeeds, closer to effective

translational lift, may require large control inputs and

will decrease stability, making recover impossible

while in UIMC.

4. Power – adjust to a climb power setting relative to the

desired airspeed. This should be executed concurrent

with steps 2 and 3.

5. Heading and Trim – pick a heading known to be free

of obstacles and maintain it. This will likely be the

heading you were already on, which was planned and

briefed. Set the heading bug, if installed, to avoid over-

controlling your bank. Maintain coordinated flight so

that an unusual attitude will not develop.

Try to avoid immediately turning 180°. Turning around is

not always the safest route and executing a turn immediately

after UIMC may lead to spatial disorientation. If a 180° turn

is the safest option, first note the heading you are on then

begin the turn to the reciprocal heading, but only after stable

flight is achieved (items 1 through 5 above) and maintain

a constant rate of turn appropriate to the selected airspeed.

Each encounter with UIMC is unique, and no single

procedure can ensure a safe outcome. Considerations in

determining the best course of action upon encountering

UIMC should include, at a minimum, terrain, obstructions,

freezing levels, aircraft performance and limitations, and

availability of ATC services.

There are new technologies being developed regarding

aircraft design, enhanced and lower-cost technologies,

and aircraft certification. Because of this promising future,

much of the discussion and guidance in this chapter may

one day become irrelevant. As helicopters integrate more

into the National Airspace System, the IFR infrastructure

and instrument training will become more prevalent. In the

future, UIMC may no longer be the emergency that ends

with a fatality but rather associated with proper prevention,

skilled recovery techniques along with the aid of emerging

new life saving avionics technology. A helicopter instrument

rating may be a life-saving addition to a pilot’s level of

certification. Please refer to the Instrument Flying Handbook

(FAA-H-8083-15, as revised); Advanced Avionics Handbook

(FAA-H-8083-6, as revised); and the Pilot’s Handbook of

Aeronautical Knowledge (FAA-H-8083-25, as revised) for

further exploration of IFR operations and how to obtain an

instrument rating.

When faced with deteriorating weather, planning and

prevention, not recovery, are the best strategies to eliminate

UIMC-related accidents and fatalities.

11-27

Emergency Equipment and Survival Gear

Both Canada and Alaska require pilots to carry survival

gear. Always carry survival gear when flying over rugged

and desolate terrain. The items suggested in Figure 11-12

are both weather and terrain dependent. The pilot also needs

to consider how much storage space the helicopter has and

how the equipment being carried affects the overall weight

and balance of the helicopter.

Chapter Summary

Emergencies should always be anticipated. Knowledge

of the helicopter, possible malfunctions and failures, and

methods of recovery can help the pilot avoid accidents and

be a safer pilot. Helicopter pilots should always expect the

worse hazards and possible aerodynamic effects and plan for

a safe exit path or procedure to compensate for the hazard.

12-1

Introduction

Pilots rely more on vision than on any other sense to orient

themselves in flight. The following visual factors contribute

to flying performance: good depth perception for safe

landings, good visual acuity to identify terrain features and

obstacles in the flightpath, and good color vision. Although

vision is the most accurate and reliable sense, visual cues can

be misleading, contributing to incidents occurring within the

flight environment. Pilots should be aware of and know how

to compensate effectively for the following:

• Physical deficiency or self-imposed stress, such as

smoking, which limits night-vision capability

• Visual cue deficiencies

• Limitations in visual acuity, dark adaptation, and color

and depth perception

For example, at night, the unaided eye has degraded visual

acuity. For more information on night operations, reference

Chapter 17, Aeromedical Factors, of the Pilot’s Handbook

of Aeronautical Knowledge (FAA-H-8083-25, as revised).

Night Operations

Chapter 12

12-2

Figure 12-1. Effects of dimming cockpit lighting during night flight

to better see surrounding terrain.

Visual Deficiencies

Night Myopia

At night, blue wavelengths of light prevail in the visible

portion of the spectrum. Therefore, slightly nearsighted

(myopic) individuals viewing blue-green light at night may

experience blurred vision. Even pilots with perfect vision find

that image sharpness decreases as pupil diameter increases.

For individuals with mild refractive errors, these factors

combine to make vision unacceptably blurred unless they

wear corrective glasses. Another factor to consider is “dark

focus.” When light levels decrease, the focusing mechanism

of the eye may move toward a resting position and make the

eye more myopic. These factors become important when

pilots rely on terrain features during unaided night flights.

Practicing good light discipline is very important and helps

pilots to retain their night adaptation. Keeping the cockpit

lighting on dim allows the pilot to better identify outside

details, unmarked hazards such as towers less than 200'

AGL, and unimproved landing sites with no hazard lighting.

A simple exercise that shows the effect of high versus low

light contrast would be to go out to a very dark road and

turn the dash board lights down very low or off and let your

eyes adjust to the ambient light level. Then, turn the dash

board lights up and note how the outside features disappear.

The same concept applies to cockpit lighting and being able

to see the surrounding terrain and obstacles. [Figure 12-1]

Special corrective lenses can be prescribed to pilots who

experience night myopia.

The eye automatically adjusts for the light level experienced.

During night flight, the cockpit and instrument lights should

be as dim as possible. The eye can then adjust for the outside

lighting conditions (ambient lighting) to see outside. The

dimmer the inside lighting is, the better you can see outside.

Hyperopia

Hyperopia is also caused by an error in refraction. In a

hyperopic state, when a pilot views a near image, the actual

focal point of the eye is behind the retinal plane (wall),

causing blurred vision. Objects that are nearby are not seen

clearly; only more distant objects are in focus. This problem,

is referred to as farsightedness.

Astigmatism

An unequal curvature of the cornea or lens of the eye causes

this condition. A ray of light is spread over a diffused area

in one meridian. In normal vision, a ray of light is sharply

focused on the retina. Astigmatism is the inability to

focus different meridians simultaneously. If, for example,

astigmatic individuals focus on power poles (vertical),

the wires (horizontal) are out of focus for most of them.

[Figure 12-2]

Presbyopia

This condition is part of the normal aging process, which

causes the lens to harden. Beginning in the early teens, the

human eye gradually loses the ability to accommodate for

and focus on nearby objects. When people are about 40 years

old, their eyes are unable to focus at normal reading distances

without reading glasses. Reduced illumination interferes with

focus depth and accommodation ability. Hardening of the lens

may also result in clouding of the lens (cataract formation).

Aviators with early cataracts may see a standard eye chart

clearly under normal daylight but have difficulty seeing under

bright light conditions. This problem is due to light scattering

as it enters the eye. This glare sensitivity is disabling under

certain circumstances. Glare disability, related to contrast

sensitivity, is the ability to detect objects against varying

shades of backgrounds. Other visual functions decline with

age and affect the aircrew member’s performance:

• Dynamic acuity

• Recovery from glare

• Function under low illumination

• Information processing

Vision in Flight

The visual sense is especially important in collision

avoidance and depth perception. Due to the structure of the

human eye, illusions and blindspots occur. The more pilots

understand the eye and how it functions, the easier it is to

compensate for these illusions and blindspots. Figure 12-3

shows the basic anatomy of the human eye and how it is like

12-3

Normal view Astigmatic view

The rods and

cones (film) of

the retina are

the receptors

which record

the image and

transmit it

through the

optic nerve to

the brain for

interpretation.

Rods and

cones

Fovea

(All Cones)

The pupil (aperture) is the opening at

the center of the iris. The size of the

pupil is adjusted to control the amount

of light entering the eye.

PUPIL

Light passes through the cornea (the

transparent window on the front of the

eye) and then through the lens to

focus on the retina.

CORNEA

Iris

Retina

Lens

Optic nerve

Rod concentration

Figure 12-2. Example of a view that might be experienced by someone with astigmatism.

Figure 12-3. The human eye.

Visual Acuity

Normal visual acuity, or sharpness, is 20/20. A value of

20/80 indicates that an individual reads at 20 feet the letters

that an individual with normal acuity (20/20) reads at 80

feet away. The human eye functions like a camera. It has

a camera. A camera is able to focus on near and far objects

by changing the distance between the lens and the film.

With the eye on the other hand, objects can be seen clearly

at various distances because the shape of its lens is changed

automatically by small muscles.

12-4

Once a target is detected in the peripheral

field of dark-adapted vision, aircrews

maintain continual surveillance by using

the off-center vision technique. They look

10 degrees above, below, or to either side

of the target, viewing it no longer than two

to three seconds at each position.

Observer

FOCAL POINTS

10°

X 10° X 10°

Figure 12-4. Off-center vision technique.

an instantaneous field of view, which is oval and typically

measures 120° vertically by 150° horizontally. When both

eyes are used for viewing, the overall field of vision measures

about 120° vertically by 200° horizontally.

The Eye

Vision is primarily the result of light striking a photosensitive

layer, called the retina, at the back of the eye. The retina is

composed of light-sensitive cones and rods. The cones in the

eye perceive an image best when the light is bright, while the

rods work best in low light. The pattern of light that strikes

the cones and rods is transmitted as electrical impulses by the

optic nerve to the brain where these signals are interpreted

as an image.

Cones

Cones are concentrated around the center of the retina. They

gradually diminish in number as the distance from the center

increases. Cones allow color perception by sensing red, blue,

and green light. Directly behind the lens, on the retina, is

a small, notched area called the fovea. This area contains

only a high concentration of cone receptors. The best vision

in daylight is obtained by looking directly at the object.

This focuses the image on the fovea, where detail is best

seen. The cones, however, do not function well in darkness,

which explains why color is not seen as vividly at night as

it is during the day.

Rods

Concentrated outside the fovea area, the rods are the dim

light and night receptors. The number of rods increases as the

distance from the fovea increases. Rods sense images only

in black and white. Because the rods are not located directly

behind the pupil, they are responsible for most peripheral

vision. Images that move are perceived more easily by the

rod areas than by the cones in the fovea. If you have ever

seen something move out of the corner of your eye, it was

most likely detected by rod receptors.

In low light, the cones lose much of their function, while

rods become more receptive. The eye sacrifices sharpness for

sensitivity. The ability to see an object directly in front of you is

reduced, and much depth perception is lost, as well as judgment

of size. The concentration of cones in the fovea can make a

night blindspot at the center of vision. How well a person sees

at night is determined by the rods in the eyes, as well as by the

amount of light allowed into the eyes. At night, the wider the

pupil is open at night, the better night vision becomes.

Night Vision

Diet and general physical health have an impact on how well

a person can see in the dark. Deficiencies in vitamins A and C

have been shown to reduce night acuity. Other factors, such

as carbon monoxide poisoning, smoking, alcohol, and certain

drugs can greatly decrease night vision. Lack of oxygen can

also decrease night vision as the eye requires more oxygen

per unit weight than any other part of the body.

Night Scanning

Good night visual acuity is needed for collision avoidance.

Night scanning, like day scanning, uses a series of short,

regularly spaced eye movements in 10° sectors. Unlike day

scanning, however, off-center viewing is used to focus objects

on the rods rather than the fovea blindspot. [Figure 12-4] When

looking at an object, avoid staring at it too long. If staring

at an object without moving the eyes, the retina becomes

accustomed to the light intensity and the image begins to

fade. To keep it clearly visible, new areas in the retina must

be exposed to the image. Small, circular eye movements help

eliminate the fading. Also, move the eyes more slowly from

sector to sector than during the day to prevent blurring.

During daylight, objects can be perceived at a great distance

with good detail. At night, range is limited, and detail is poor.

Objects along the flight path can be more readily identified at

night, by using the proper techniques to scan the terrain. To

12-5

10°

6 seconds

6 seconds 3 seconds

3 seconds 3 seconds 3 seconds

3 seconds 3 seconds

4 seconds 4 seconds

4 seconds

Figure 12-5. Scanning pattern.

Figure 12-6. Night vision.

scan effectively, pilots look from side to side. They should

begin scanning at the greatest distance at which an object

can be perceived high on the horizon, thence moving inward

toward the position of the aircraft. Figure 12-5 shows this

scanning pattern. Because the light-sensitive elements of

the retina are unable to perceive images that are in motion, a

stop-turn-stop-turn motion should be used. For each stop, an

area about 30 degrees wide should be scanned. This viewing

angle includes an area about 250 meters wide at a distance of

500 meters. The duration of each stop is based on the degree

of detail that is required, but no stop should last more than

two or three seconds. When moving from one viewing point

to the next, pilots should overlap the previous field of view

by 10 degrees. This scanning technique allows greater clarity

in observing the periphery. Other scanning techniques, as

illustrated in Figure 12-6, may be developed to fit the situation.

Obstruction Detection

Obstructions having poor reflective surfaces, such as wires

and small tree limbs, are difficult to detect. The best way to

12-6

Figure 12-7. Aircraft position lights.

locate wires is by looking for the support structures. However,

pilots should review the most current hazard maps with

known wire locations before night flights.

Aircraft Lighting

In order to see other aircraft more clearly, regulations require

that all aircraft operating during the night hours have special

lights and equipment. The requirements for operating at night

are found in Title 14 of the Code of Federal Regulations (14

CFR) part 91. In addition to aircraft lighting, the regulations

also provide a definition of night flight in accordance with

14 CFR part 91, currency requirements, fuel reserves, and

necessary electrical systems.

Position lights enable a pilot to locate another aircraft, as

well as help determine its direction of flight. The approved

aircraft lights for night operations are a green light on the

right cabin side or wingtip, a red light on the left cabin side

or wingtip, and a white position light on the tail. In addition,

flashing aviation red or white anticollision lights are required

for all flights, if equipped on the aircraft and in an operable

condition (in accordance with 14 CFR Section 91.209(b),

which aids in the identification during night conditions).

These flashing lights can be in a number of locations but are

most commonly found on the top and bottom of the cabin.

Figure 12-7 shows examples of aircraft lighting. By

interpreting the position lights on other aircraft, the pilot in

aircraft 3 can determine whether the aircraft is flying in the

opposite direction or is on a collision course. If a red position

light is seen to the right of a green light, such as shown by

aircraft 1, it is flying toward aircraft 3. A pilot should watch

this aircraft closely and be ready to change course. Aircraft 2,

on the other hand, is flying away from aircraft 3, as indicated

by the white position light.

Visual Illusions

Illusions give false impressions or misconceptions of actual

conditions; therefore, pilots must understand the type of

illusions that can occur and the resulting disorientation.

Although the eye is the most reliable of the senses, some

illusions can result from misinterpreting what is seen; what

is perceived is not always accurate. Even with the references

outside the cockpit and the display of instruments inside,

pilots must be on guard to interpret information correctly.

Relative-Motion Illusion

Relative motion is the falsely perceived self-motion in

relation to the motion of another object. The most common

example is as follows. An individual in a car is stopped at a

traffic light and another car pulls alongside. The individual

who was stopped at the light perceives the forward motion

of the second car as his or her own motion rearward. This

results in the individual applying more pressure to the brakes

unnecessarily. This illusion can be encountered during flight

in situations such as formation flight, hover taxi, or hovering

over water or tall grass.

Confusion with Ground Lights

Confusion with ground lights occurs when a pilot mistakes

ground lights for stars. The pilot can place the helicopter

in an extremely dangerous flight attitude if he or she aligns

it with the wrong lights. In Figure 12-8A, the helicopter is

aligned with a road and not with the horizon. Isolated ground

lights can appear as stars and could lead to the illusion that

the helicopter is in a nose-high attitude.

When no stars are visible because of overcast conditions,

unlighted areas of terrain can blend with the dark overcast to

create the illusion that the unlighted terrain is part of the sky

in Figure 12-8B. In this illusion, the shoreline is mistaken for

the horizon. In an attempt to correct for the apparent nose-

high attitude, a pilot may lower the collective and attempt

to fly “beneath the shore.” This illusion can be avoided by

referencing the flight instruments and establishing a true

horizon and attitude.

Reversible Perspective Illusion

At night, an aircraft or helicopter may appear to be moving

away when it is actually approaching. If the pilot of each

aircraft has the same assumption, and the rate of closure

is significant, by the time each pilot realizes his or her

own error in assumption, it may be too late to avoid a

mishap. This illusion is called reversible perspective and

is often experienced when a pilot observes another aircraft

12-7

Perceived Horizon

(ground lights)

Actual Horizon

A O M

CLUTCH MR

TEMP

CHIP

STARTER

CHIP

lOW

FUEL

LOW

RPM

333

VERTICAL SPEED

100 FEET PER MINUTE

DOWN

3024

I2 6

2 MIN TURN

DC ELEC

L R

30.0

29.929.8

I00 FEET

456

CALIBRATED

20,000 FEET

ALT

20 20

I0 I0

20 20

TESTSTBY PWR

IN Hg

ALg.

MANFOLD

PRESS

20 30

6070

100

0 10

MPH

KNOTS

120

110

100

90 80 70

3020

110

100

110

100

E R

%RPM

20 20

I0 I0

20 20

TESTSTBY PWR

Perceived Horizon

(shore line)

Actual Horizon

(overcast sky)

A O M

CLUTCH MR

TEMP

CHIP

STARTER

CHIP

lOW

FUEL

LOW

RPM

333

VERTICAL SPEED

100 FEET PER MINUTE

DOWN

3024

I2 6

2 MIN TURN

DC ELEC

L R

30.0

29.929.8

I00 FEET

456

CALIBRATED

20,000 FEET

ALT

20 20

I0 I0

20 20

TESTSTBY PWR

IN Hg

ALg.

MANFOLD

PRESS

20 30

6070

100

0 10

MPH

KNOTS

120

110

100

90 80 70

3020

110

100

110

100

E R

%RPM

20 20

I0 I0

20 20

TESTSTBY PWR

Figure 12-8. At night, the horizon may be hard to discern due to dark terrain and misleading light patterns on the ground.

or helicopter flying an approaching, parallel course. To

determine the direction of flight, the pilot should observe the

other aircraft’s position lights. Remember the following: red

on right returning; that is, if an aircraft is seen with the red

position light on the right and the green position light on the

left, the observed aircraft is traveling in the opposite direction.

Flicker Vertigo

Flicker vertigo is technically not an illusion; however, as

most people are aware from personal experience, viewing

a flickering light can be both distracting and annoying.

Flicker vertigo may be created by helicopter rotor blades or

airplane propellers interrupting direct sunlight at a rate of 4

to 20 cycles per second. Flashing anticollision strobe lights,

especially while the aircraft is in the clouds, can also produce

this effect. One should also be aware that photic stimuli at

certain frequencies could produce seizures in those rare

individuals who are susceptible to flicker-induced epilepsy.

Night Flight

The night flying environment and the techniques used when

flying at night depend on outside conditions. Flying on a

bright, clear, moonlit evening when the visibility is good, and

the wind is calm is not much different from flying during the

day. However, if flying on an overcast night over a sparsely

populated area, with few or no outside lights on the ground,

the situation is quite different. Visibility is restricted, so be

more alert in steering clear of obstructions and low clouds.

Options are also limited in the event of an emergency, as it

is more difficult to find a place to land and determine wind

direction and speed. At night, rely more heavily on the aircraft

systems, such as lights, flight instruments, and navigation

equipment. As a precaution, if visibility is limited or outside

references are inadequate, strongly consider delaying the

flight until conditions improve, unless proper instrument

flight training has been received and the helicopter has the

appropriate instrumentation and equipment.

Preflight

Aircraft preflight inspection is a critical aspect of flight

safety. It must comply with the appropriate rotorcraft flight

manual (RFM). Preflight should be scheduled as early as

possible in the flight planning sequence, preferably during

daylight hours, allowing time for maintenance assistance and

correction. If a night preflight is necessary, a flashlight with

an unfiltered lens (white light) should be used to supplement

lighting. Oil and hydraulic fluid levels and leaks are difficult

to detect with a blue-green or red lens. Windscreens should

be checked to ensure they are clean and relatively free of

scratches. Slight scratches are acceptable for day flight but

may not be for night flight. The search light or landing light

should be positioned for the best possible illumination during

an emergency descent.

Careful attention must be paid to the aircraft electrical system.

In helicopters equipped with fuses, a spare set is required

by regulation, and by common sense, so make sure they are

on board. If the helicopter is equipped with circuit breakers,

check to see that they are not tripped. A tripped circuit breaker

may be an indication of an equipment malfunction and should

be left for maintenance to troubleshoot before flying.

All aircraft operating between sunset and sunrise are required

to have operable navigation (position) lights. Turn these lights

on during the preflight to inspect them visually for proper

operation. Between sunset and sunrise, these lights must be

on any time the helicopter is operating.

12-8

All recently manufactured aircraft certificated for night

flight must have an anticollision light that makes the aircraft

more visible to other pilots. This light is either a red or white

flashing light and may be in the form of a rotating beacon

or a strobe. While anticollision lights are required for night

visual flight rules (VFR) flights, they may be turned off any

time they create a distraction for the pilot.

One of the first steps in preparation for night flight is to

become thoroughly familiar with the helicopter’s cockpit,

instrumentation, and control layout. It is recommended that

a pilot practice locating each instrument, control, and switch,

both with and without cabin lights. Since the markings on

some switches and circuit breaker panels may be difficult

to read at night, be able to locate and use these devices, and

read the markings in poor light conditions. Before starting

the engine, make sure all necessary equipment and supplies

needed for the flight, such as charts, notepads, and flashlights,

are accessible and ready for use.

Cockpit Lights

Check all interior lights with special attention to the instrument

and panel lights. The panel lighting can usually be controlled

with a rheostat or dimmer switch, allowing the pilot to adjust

the intensity. If a particular light is too bright or causes

reflection or glare off the windshield, it should be adjusted or

turned off. As ambient light level decreases from twilight to

darkness, intensity of the cockpit lights is reduced to a low,

usable intensity level that reduces any glare or reflection off

the windshield. The light level should be adjusted to as close

to the ambient light level as possible. A flashlight, with red or

blue-green lens filter, or map light can supplement the available

light in the cockpit. Always carry a flashlight with fresh

batteries to provide an alternate source of light if the interior

lights malfunction. If an existing map/utility light is used, it

should be hand-held or remounted to a convenient location.

In order to retain night adaptation, use low level light when

using your checklist. Brief your passengers on the importance

of light discipline during night flight so the pilot is not blinded,

causing loss of dark adaptation.

Engine Starting and Rotor Engagement

Use extra caution when starting the engine and engaging the

rotors, especially in dark areas with little or no outside lights.

In addition to the usual call of “clear,” turn on the position

and anticollision lights. If conditions permit, also turn the

landing light on momentarily to help warn others that the

engine is about to start and engage the rotors.

Taxi Technique

Landing lights usually cast a beam that is narrow and

concentrated ahead of the helicopter, so illumination to the

side is minimal. Therefore, slow the taxi at night, especially

in congested ramp and parking areas. Some helicopters have

a hover light in addition to a landing light, which illuminates

a larger area under the helicopter.

When operating at an unfamiliar airport at night, ask for

instructions or advice concerning local conditions, so as to

avoid taxiing into areas of construction, or unlighted, unmarked

obstructions. Ground controllers or UNICOM operators are

usually cooperative in furnishing this type of information.

Night Traffic Patterns

Traffic patterns are covered in Chapter 9, Basic Flight

Maneuvers, but the following additional considerations

should be taken into account when flying a helicopter in a

night traffic pattern:

1. The minimum recommended pattern height at night

is 1,000 feet when able.

2. If possible, consider taking the right hand night pattern

with fixed wing in the left hand pattern for extra

separation, but if needed, conform and integrate with

the fixed wing using the same pattern height.

3. Be extra vigilant on abiding with noise abatement

procedures at night.

4. Always plan to use the lit runway at night for

unaided (no night vision equipment) approaches and

departures.

5. Avoid downwind and crosswind approaches at night

when able.

Takeoff

Before takeoff, make sure that there is a clear, unobstructed

takeoff path. At airports, this is accomplished by taking

off over a runway or taxi way, however, if operating off-

airport, pay more attention to the surroundings. Obstructions

may also be difficult to see if taking off from an unlighted

area. Once a suitable takeoff path is chosen, select a point

down the takeoff path to use for directional reference. The

landing light should be positioned in order to illuminate

the tallest obstacles in the takeoff path. During a night

takeoff, notice a lack of reliable outside visual references

after becoming airborne. This is particularly true at small

airports and off-airport landing sites located in sparsely

populated areas. To compensate for the lack of outside

references, use the available flight instruments as an aid.

Check the altimeter and the airspeed indicator to verify the

proper climb attitude. An attitude indicator, if installed, can

enhance attitude reference.

The first 500 feet of altitude after takeoff is considered to be

the most critical period in transitioning from the comparatively

well-lit airport or heliport into what sometimes appears to be

12-9

total darkness. A takeoff at night is usually an “altitude over

airspeed” maneuver, meaning a pilot most likely performs

a nearly maximum performance takeoff. This improves the

chances for obstacle clearance and enhances safety.

En Route Procedures

In order to provide a higher margin of safety, it is

recommended that a cruising altitude somewhat higher than

normal be selected. There are three reasons for this. First,

a higher altitude gives more clearance between obstacles,

especially those that are difficult to see at night, such as high-

tension wires and unlighted towers. Second, in the event of

an engine failure, there is more time to set up for a landing

and the greater gliding distance gives more options for a safe

landing. Third, radio reception is improved, particularly if

using radio aids for navigation.

During preflight planning, when possible, it is recommended

that a route of flight be selected that is within reach of an

airport, or any safe landing site. It is also recommended

that pilots fly as close as possible to a populated or lighted

area, such as a highway or town. Not only does this offer

more options in the event of an emergency, but also makes

navigation a lot easier. A course comprised of a series of

slight zigzags to stay close to suitable landing sites and

well-lit areas, only adds a little more time and distance to an

otherwise straight course.

In the event of a forced landing at night, use the same

procedure recommended for day time emergency landings.

If available, turn on the landing light during the final descent

to help in avoiding obstacles along the approach path.

Collision Avoidance at Night

Because the quantity and quality of outside visual references

are greatly reduced, a pilot tends to focus on a single point

or instrument, making him or her less aware of the other

traffic around. Make a special effort to devote enough time

to scan for traffic. As discussed previously in this chapter,

effective scanning is accomplished with a series of short,

regularly spaced eye movements that bring successive

areas of the sky into the central visual field. Contrary to

the 30-degree scan used to view the ground in the case of

scanning for other aircraft, each movement in this case

should not exceed 10 degrees, and each area should be

observed for at least 1 second to enable detection. If the

pilot detects a dimly lit object in a certain direction, the

pilot should not look directly at the object, but scan the area

adjacent to it, called off-center viewing. This will decrease

the chances of fixating on the light and allow focusing more

on the objects (e.g., tower, aircraft, ground lights). Short

stops of a few seconds in duration in each scan will help to

detect the light and its movement. A pilot can determine

another aircraft’s direction of flight by interpreting the

position and anticollision lights, as previously described.

When scanning, pilots should also remember to move their

heads, not just their eyes. Ground obstructions can cover

a considerable amount of sky, and the area can easily be

uncovered by a small head movement.

Approach and Landing

Night approaches and landings do have some advantages over

daytime approaches, as the air is generally smoother, and the

disruptive effects of turbulence and excessive crosswinds are

often absent. However, there are a few special considerations

and techniques that apply to approaches at night. For

example, when landing at night, especially at an unfamiliar

airport, make the approach to a lighted runway and then use

the taxiways to avoid unlighted obstructions or equipment.

Carefully controlled studies have revealed that pilots have a

tendency to make lower approaches at night than during the

day. This is potentially dangerous as there is a greater chance

of hitting an obstacle, such as an overhead wire or fence, that is

difficult to see. It is good practice to make steeper approaches at

night, increasing the probability of clearing obstacles. Monitor

altitude and rate of descent using the altimeter.

Another pilot tendency during night flight is to focus too

much on the landing area and not pay enough attention to

airspeed. If too much airspeed is lost, a vortex ring state

condition may result. Maintain the proper attitude during

the approach, and ensure that you keep some forward

airspeed and movement until close to the ground. Outside

visual references for airspeed and rate of closure may not be

available, especially when landing in an unlit area, so pay

special attention to the airspeed indicator.

Although the landing light is a helpful aid when making

night approaches, there is an inherent disadvantage. The

portion of the landing area illuminated by the landing light

seems higher than the dark area surrounding it. This effect

can cause a pilot to terminate the approach at an altitude that

is too high, which may result in a vortex ring state condition

and a hard landing.

Illusions Leading to Landing Errors

Various surface features and atmospheric conditions

encountered in night landing can create illusions of incorrect

height above and distance from the runway threshold.

Landing errors from these illusions can be prevented by

anticipating them during approaches, conducting an aerial

visual inspection of unfamiliar airports before landing, using

electronic glideslope or VASI systems when available, and

maintaining optimum proficiency in landing procedures.

12-10

Featureless Terrain Illusion

An absence of ground features, as when landing over water,

darkened areas, and terrain made featureless by snow, can

create the illusion that the aircraft is at a higher altitude than

it actually is. The pilot who does not recognize this illusion

will fly a lower approach.

Atmospheric Illusions

Rain on the windscreen can create the illusion of greater

height, and atmospheric haze can create the illusion of being

at a greater distance from the runway. The pilot who does not

recognize these illusions flies a higher approach. Penetration

of fog can create the illusion of pitching up. The pilot who

does not recognize this illusion steepens the approach, often

quite abruptly.

Ground Lighting Illusions

Lights along a straight path can be mistaken for runway

and approach lights. This might include street lights along a

roadside or even the internal lights of a moving train. Another

illusion may occur with very intense runway and approach

lighting. Due to the relative brightness of these lights, the

pilot may perceive them to be closer than they really are.

Assuming that the lights are as close as they appear, the

pilot may attempt an approach that is actually lower than

glideslope. Conversely, the pilot flying over terrain with few

lights may make a lower than normal approach.

Helicopter Night VFR Operations

While ceiling and visibility significantly affect safety in night

VFR operations, lighting conditions also have a profound

effect on safety. Even in conditions in which visibility and

ceiling are determined to be visual meteorological conditions,

the ability to discern unlit or low contrast objects and terrain

at night may be compromised. The ability to discern these

objects and terrain is referred to as the “seeing condition,”

and is related to the amount of natural and man-made

lighting available, and the contrast, reflectivity, and texture

of surface terrain and obstruction features. In order to conduct

operations safely, seeing conditions must be accounted for in

the planning and execution of night VFR operations.

Night VFR seeing conditions can be described by identifying

high lighting conditions and low lighting conditions.

High lighting conditions exist when one of two sets of

conditions are present:

1. The sky cover is less than broken (less than 5⁄8 cloud

cover), the time is between the local moon rise and

moon set, and the lunar disk is at least 50 percent

illuminated; or

2. The aircraft is operated over surface lighting that, at

least, provides lighting of prominent obstacles, the

identification of terrain features (shorelines, valleys,

hills, mountains, slopes) and a horizontal reference

by which the pilot may control the helicopter. For

example, this surface lighting may be the result of:

a. Extensive cultural lighting (manmade, such as a

built-up area of a city),

b. Significant reflected cultural lighting (such as the

illumination caused by the reflection of a major

metropolitan area’s lighting reflecting off a cloud

ceiling), or

c. Limited cultural lighting combined with a

high level of natural reflectivity of celestial

illumination, such as that provided by a surface

covered by snow or a desert surface.

Low lighting conditions are those that do not meet the high

lighting conditions requirements.

Some areas may be considered a high lighting environment

only in specific circumstances. For example, some surfaces,

such as a forest with limited cultural lighting, normally

have little reflectivity, requiring dependence on significant

moonlight to achieve a high lighting condition. However,

when that same forest is covered with snow, its reflectivity

may support a high lighting condition based only on starlight.

Similarly, a desolate area, with little cultural lighting, such as

a desert, may have such inherent natural reflectivity that it

may be considered a high lighting conditions area regardless

of season, provided the cloud cover does not prevent starlight

from being reflected from the surface. Other surfaces, such

as areas of open water, may never have enough reflectivity or

cultural lighting to ever be characterized as a high lighting area.

Through the accumulation of night flying experience in a

particular area, the pilot develops the ability to determine,

prior to departure, which areas can be considered supporting

high or low lighting conditions. Without that pilot experience,

low lighting considerations should be applied by pilots for

both preflight planning and operations until high lighting

conditions are observed or determined to be regularly

available. Even if the aircraft is certified for day and night

VFR conditions, night flight should only be conducted if

adequate celestial illumination is assured during the entirety

of the flight.

Chapter Summary

Knowledge of the basic anatomy and physiology of the eye

is helpful in the study of helicopter night operations. Adding

12-11

to that knowledge a study of visual illusions gives the pilot

ways to overcome those illusions. Techniques for preflight,

engine start-up, collision avoidance, and night approach and

landings help teach the pilot safer ways to conduct flight at

night. More detailed information on the subjects discussed

in this chapter is available in the Aeronautical Information

Manual (AIM) and online at www.faa.gov.

12-12

13-1

Introduction

The accident rate for helicopters has traditionally been higher

than the accident rate of fixed-wing aircraft, probably due to

the helicopter’s unique capabilities to fly and land in more

diverse situations than fixed-wing aircraft and pilot attempts

to fly the helicopter beyond the limits of his or her abilities or

beyond the capabilities of the helicopter. With no significant

improvement in helicopter accident rates for the last 20 years,

the Federal Aviation Administration (FAA) has joined with

various members of the helicopter community to improve

the safety of helicopter operations.

According to National Transportation Safety Board (NTSB)

statistics, approximately 80 percent of all aviation accidents

are caused by pilot error, the human factor. Many of

these accidents are the result of the failure of instructors

to incorporate single-pilot resource management (SRM)

and risk management into flight training instruction of

aeronautical decision-making (ADM).

SRM is defined as the art of managing all the resources (both

on board the aircraft and from outside sources) available to a

pilot prior to and during flight to ensure a successful flight.

When properly applied, SRM is a key component of ADM.

Additional discussion includes integral topics such as, the

concepts of risk management, workload or task management,

situational awareness, controlled flight into terrain (CFIT)

awareness, and automation management.

Effective Aeronautical

Decision-Making

Chapter 13

13-2

Preflight

Takeoff

Cruise

Approach & Landing

Time

Task Load

High

Low

Pilot Capabilities

Task Requirements

Figure 13-1. The pilot has a limited capacity of doing work and handling tasks, meaning there is a point at which the tasking exceeds

the pilot’s capability. When this happens, either tasks are not done properly or some are not done at all.

ADM is all about learning how to gather information, analyze

it, and make decisions. It helps the pilot accurately assess

and manage risk and make accurate and timely decisions.

Although the flight is coordinated by a single person, the

use of available resources, such as air traffic control (ATC)

and flight service stations (FSS)/automated flight service

stations (AFSS), replicates the principles of crew resource

management (CRM) (see page 14-7).

References on SRM and ADM include:

• FAA-H-8083-2, Risk Management Handbook.

• Aeronautical Information Manual (AIM).

• Advisory Circular (AC) 60-22, Aeronautical Decision

Making, which provides background information

about ADM training in the general aviation (GA)

environment.

• FAA-H-8083-25, Pilot’s Handbook of Aeronautical

Knowledge.

Aeronautical Decision-Making (ADM)

Making good choices sounds easy enough. However,

there are a multitude of factors that come into play when

these choices, and subsequent decisions, are made in the

aeronautical world. Many tools are available for pilots to

become more self-aware and assess the options available,

along with the impact of their decision. Yet, with all the

available resources, accident rates are not being reduced. Poor

decisions continue to be made, frequently resulting in lives

being lost and/or aircraft damaged or destroyed. The Risk

Management Handbook discusses ADM and SRM in detail

and should be thoroughly read and understood.

While progress is continually being made in the advancement

of pilot training methods, aircraft equipment and systems, and

services for pilots, accidents still occur. Historically, the term

“pilot error” has been used to describe the causes of these

accidents. Pilot error means an action or decision made by

the pilot was the cause of, or a contributing factor that led to,

the accident. This definition also includes the pilot’s failure to

make a decision or take action. From a broader perspective,

the phrase “human factors related” more aptly describes these

accidents since it is usually not a single decision that leads

to an accident, but a chain of events triggered by a number

of factors. [Figure 13-1]

The poor judgment chain, sometimes referred to as the

“error chain,” is a term used to describe this concept of

contributing factors in a human factors related accident.

Breaking one link in the chain is often the only event

necessary to change the outcome of the sequence of

events. The following is an example of the type of scenario

illustrating the poor judgment chain.

Scenario

A Helicopter Air Ambulance (HAA) pilot is nearing the end

of his shift when he receives a request for a patient pickup

at a roadside vehicle accident. The pilot has started to feel

the onset of a cold; his thoughts are on getting home and

getting a good night’s sleep. After receiving the request, the

pilot checks the accident location and required flightpath

to determine if he has time to complete the flight to the

scene, then on to the hospital before his shift expires. The

pilot checks the weather and determines that, although

thunderstorms are approaching, the flight can be completed

prior to their arrival.

13-3

The pilot and on-board medical crews depart the home

location and arrive overhead, at the scene of the vehicular

accident. The pilot is not comfortable with the selected

landing area due to tall trees in all quadrants of the confined

area. The pilot searches for a secondary landing area. Unable

to find one nearby, the pilot then returns to the initial landing

area and decides he can make it work.

After successfully landing the aircraft, he is told that there

will be a delay before the patient is loaded because more time

is needed to extricate the patient from the wreckage. Knowing

his shift is nearly over, the pilot begins to feel pressured to

“hurry up” or he will require an extension for his duty day.

After 30 minutes, the patient is loaded, and the pilot ensures

everyone is secure. He notes that the storm is now nearby and

that winds have picked up considerably. The pilot thinks, “No

turning back now, the patient is on board and I’m running out

of time.” The pilot knows he must take off almost vertically

to clear the obstacles and chooses his departure path based

on the observed wind during landing. Moments later, prior to

clearing the obstacles, the aircraft begins an uncontrollable

spin and augers back to the ground, seriously injuring all on

board and destroying the aircraft.

What could the pilot have done differently to break this

error chain? More important—what would you have done

differently? By discussing the events that led to this accident,

you should develop an understanding of how a series of

judgmental errors contributed to the final outcome of this flight.

For example, the pilot’s decision to fly the aircraft knowing

that the effects of an illness were present was the initial

contributing factor. The pilot was aware of his illness, but,

was he aware of the impact of the symptoms—fatigue,

general uneasy feeling due to a slight fever, perhaps?

Next, knowing the shift was about to end, the pilot based his

time required to complete the flight on ideal conditions, and

did not take into consideration the possibility of delays. This

led to a feeling of being time limited.

Even after determining the landing area was unsuitable, the

pilot forced the landing due to time constraints. At any time

during this sequence, the pilot could have aborted the flight

rather than risk crew lives. Instead, the pilot became blinded

by a determination to continue.

After landing, and waiting 30 minutes longer than planned,

the pilot observed the outer effects of the thunderstorm, yet

still attempted to depart. The pilot dispelled any available

options by thinking the only option was to go forward;

however, it would have been safer to discontinue the flight.

Using the same departure path selected under different wind

conditions, the pilot took off and encountered winds that

led to loss of aircraft control. Once again faced with a self-

imposed time constraint, the pilot improperly chose to depart

the confined area. The end result: instead of one patient to

transport by ground (had the pilot aborted the flight at any

point), there were four patients to be transported.

On numerous occasions leading to and during the flight, the

pilot could have made effective decisions that could have

prevented this accident. However, as the chain of events

unfolded, each poor decision left him with fewer options.

Making sound decisions is the key to preventing accidents.

Traditional pilot training emphasizes flying skills, knowledge

of the aircraft, and familiarity with regulations. SRM and

ADM training focus on the decision-making process and on

the factors that affect a pilot’s ability to make effective choices.

Trescott Tips

Max Trescott, Master Certificated Flight Instructor (CFI)

and Master Ground Instructor and winner of the 2008 CFI of

the year, has published numerous safety tips that every pilot

should heed. He believes that the word “probably” should

be purged from our flying vocabulary. Mr. Trescott contends

that “probably” means we’ve done an informal assessment

of the likelihood of an event occurring and have assigned a

probability to it. He believes the term implies that we believe

things are likely to work out, but there’s some reasonable

doubt in our mind. He further explains that if you ever think

that your course of action will “probably work out,” you

need to choose a new option that you know will work out.

Another safety tip details the importance of accumulating

flight hours in one specific airframe type. He explains that

“statistics have shown that accidents are correlated more with

the number of hours of experience a pilot has in a particular

aircraft model and not with his or her total number of flight

hours. Accidents tend to decrease after a pilot accumulates

at least 100 hours of experience in the aircraft he or she is

flying. Thus, when learning to fly, or when transitioning into

a new model, your goal should be to concentrate your flying

hours in that model.” He suggests waiting until you reach 100

hours of experience in one particular model before attempting

a dual rating with another model. In addition, if you only fly

a few hours per year, maximize your safety by concentrating

those hours in just one aircraft model.

The third safety tip that is well worth mentioning is what

Mr. Trescott calls “building experience from the armchair.”

Armchair flying is simply closing your eyes and mentally

practicing exactly what you do in the aircraft. This is an

excellent way to practice making radio calls, departures,

approaches and even visualizing the parts and pieces of the

FAA Helicopter Flying Handbook: Chapter 1 — Introduction to the Helicopter — Part 7

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