1 2 3
Figure 10-7. Slope takeoff.
Technique
Begin the takeoff by increasing rpm to the normal range with
the collective full down. Then, move the cyclic toward the
slope (frame 1). Holding the cyclic toward the direction of
the slope causes the downslope skid to rise as the pilot slowly
raises the collective (frame 2). As the skid comes up, move
the cyclic as necessary to maintain a level attitude in relation
to the horizon. If properly coordinated, the helicopter should
attain a level attitude as the cyclic reaches the neutral position.
At the same time, use antitorque pedal pressure to maintain
heading and throttle to maintain rpm. With the helicopter
level and the cyclic centered, pause momentarily to verify
everything is correct, and then gradually raise the collective
to complete the liftoff (frame 3). After reaching a hover,
avoid hitting the ground with the tail rotor by not turning the
helicopter tail upslope and gaining enough altitude to ensure
the tail rotor is clear. If an upslope wind exists, execute a
crosswind takeoff and then make a turn into the wind after
clearing the ground with the tail rotor.
Common Errors
1. Failing to adjust cyclic control to keep the heli copter
from sliding down slope.
2. Failing to maintain proper rpm.
3. Holding excessive cyclic into the slope as the down
slope skid is raised.
4. Failure to maintain heading, resulting in a turning or
pivoting motion.
5. Turning the tail of the helicopter into the slope during
takeoff.
Confined Area Operations
A confined area is an area where the flight of the heli copter
is limited in some direction by terrain or the presence of
obstructions, natural or manmade. For example, a clearing
in the woods, a city street, a road, a building roof, etc., can
each be regarded as a confined area. The helicopter pilot
has added responsibilities when conducting operations
from a confined area that airplanes pilots do not. He or she
assumes the additional roles of the surveyor, engineer, and
manager when selecting an area to conduct operations. While
airplane pilots generally operate from known pre-surveyed
and improved landing areas, helicopter pilots fly into areas
never used before for helicopter operations. Generally,
takeoffs and landings should be made into the wind to obtain
maximum airspeed with minimum groundspeed. The pilot
should begin with as nearly accurate an altimeter setting as
possible to determine the altitude.
There are several things to consider when operating in
confined areas. One of the most important is maintaining
a clearance between the rotors and obstacles forming the
confined area. The tail rotor deserves special considera tion
because, in some helicopters, it is not always visible from
the cabin. This not only applies while making the approach,
but also while hovering. Another consider ation is that wires
are especially difficult to see; however, their supporting
devices, such as poles or towers, serve as an indication of
their presence and approximate height. If any wind is present,
expect some turbulence. [Figure 10-8]
Something else to consider is the availability of forced
landing areas during the planned approach. Think about
the possibility of flying from one alternate landing area to
another throughout the approach, while avoiding unfavorable
areas. Always leave a way out in case the landing cannot be
completed, or a go-around is necessary.
During the high reconnaissance, the pilot needs to formulate
a takeoff plan as well. The heights of obstacles need to be
determined. It is not good practice to land in an area and
then determine that insufficient power exists to depart.
Generally, more power is required to take off than to land
so the takeoff criteria is most crucial. Fixing the departure
azimuth or heading on the compass is a good technique to
use. This ensures that the pilot is able to take off over the
preselected departure path when it is not visible while sitting
in the confined area.
WIND
Figure 10-8. If the wind velocity is 10 knots or greater, expect updrafts on the windward side and downdrafts on the lee side of obstacles.
Plan the approach with these factors in mind, but be ready to alter plans if the wind speed or direction changes.
Approach
A high reconnaissance should be completed before ini tiating
the confined area approach. Start the approach phase using
the wind and speed to the best possible advantage. Keep in
mind areas suitable for forced land ing. It may be necessary to
choose a crosswind approach that is over an open area, then
one directly into the wind that is over trees. If these conditions
exist, consider the possibility of making the initial phase of
the approach crosswind over the open area and then turn ing
into the wind for the final portion of the approach.
Always operate the helicopter as close to its normal capabilities
as possible, taking into consideration the situation at hand. In
all confined area operations, with the exception of a pinnacle
operation (see next section, Takeoff), the angle of descent
should be no steeper than necessary to clear any barrier with
the tail rotor in the approach path and still land on the selected
spot. The angle of climb on takeoff should be normal, or not
steeper than necessary to clear any bar rier. Clearing a barrier by
a few feet and maintaining normal operating rpm, with perhaps
a reserve of power, is better than clearing a barrier by a wide
mar gin but with a dangerously low rpm and no power reserve.
Always make the landing to a specific point and not to some
general area. This point should be located well forward,
away from the approach end of the area. The more confined
the area is, the more essential it is that the helicopter land
precisely at a definite point. Keep this point in sight during
the entire final approach.
When flying a helicopter near obstacles, always consider
the tail rotor. A safe angle of descent over bar riers must be
established to ensure tail rotor clearance of all obstructions.
After coming to a hover, avoid turning the tail into obstructions.
Takeoff
A confined area takeoff is considered an altitude over
airspeed maneuver where altitude gain is more important to
airspeed gain. Before takeoff, make a reconnaissance from
the ground or cockpit to determine the type of takeoff to
be performed, to determine the point from which the take-
off should be initiated to ensure the maximum amount of
available area, and finally, how to maneuver the helicopter
best from the landing point to the proposed take off position.
If wind conditions and available area permit, the heli-
copter should be brought to a hover, turned around, and
hovered forward from the landing position to the take off
position. Under certain conditions, sideward flight to the
takeoff position may be preferred, but rearward flight may
be necessary, stopping often while moving to check on the
location of obstacles relative to the tail rotor.
When planning the takeoff, consider the direction of the wind,
obstructions, and forced landing areas. To help fly up and
over an obstacle, form an imaginary line from a point on the
leading edge of the helicopter to the highest obstacle to be
cleared. Fly this line of ascent with enough power to clear
the obstacle by a safe distance. After clearing the obstacle,
maintain the power setting and accelerate to the normal climb
speed. Then, reduce power to the normal climb power setting.
Common Errors
1. Failure to perform, or improper performance of, a high
or low reconnaissance.
2. Approach angle that is too steep or too shal low for the
existing conditions.
3. Failing to maintain proper rpm.
Figure 10-9. When flying an approach to a pinnacle or ridgeline,
avoid the areas where downdrafts are present, especially when
excess power is limited. If downdrafts are encountered, it may
become necessary to make an immediate turn away from the
pinnacle to avoid being forced into the rising terrain.
4. Failure to consider emergency landing areas.
5. Failure to select a specific landing spot.
6. Failure to consider how wind and turbulence could
affect the approach.
7. Improper takeoff and climb technique for exist ing
conditions.
8. Failure to maintain safe clearance distance from
obstructions.
Pinnacle and Ridgeline Operations
A pinnacle is an area from which the surface drops away
steeply on all sides. A ridgeline is a long area from which
the surface drops away steeply on one or two sides, such
as a bluff or precipice. The absence of obstacles does not
necessarily decrease the difficulty of pinnacle or ridgeline
operations. Updrafts, downdrafts, and turbulence, together
with unsuitable terrain in which to make a forced landing,
may still present extreme hazards.
Approach and Landing
If there is a need to climb to a pinnacle or ridgeline, do it on
the upwind side, when practicable, to take advantage of any
updrafts. The approach flightpath should be paral lel to the
ridgeline and into the wind as much as possi ble. [Figure 10-9]
Load, altitude, wind conditions, and terrain features
determine the angle to use in the final part of an approach.
As a general rule, the greater the winds are, the steeper the
approach needs to be to avoid turbulent air and downdrafts.
Groundspeed during a pinnacle approach is more difficult to
judge because visual references are farther away than during
approaches over trees or flat terrain. Pilots must continually
perceive the apparent rate of closure by observing the apparent
change in size of the landing zone features. Avoid the
misperception of an increasing rate of closure to the landing
site. The apparent rate of closure should be that of a brisk
walk. If a crosswind exists, remain clear of down-drafts on
the leeward or downwind side of the ridgeline. If the wind
velocity makes the crosswind landing hazardous, it may be
possible to make a low, coordinated turn into the wind just
prior to terminating the approach. When making an approach
to a pinnacle, avoid leeward turbulence and keep the helicopter
within reach of a forced landing area as long as possible.
On landing, take advantage of the long axis of the area when
wind conditions permit. Touchdown should be made in the
forward portion of the area. When approaching to land on
pinnacles, especially manmade areas such as rooftop pads,
the pilot should determine the personnel access pathway to
the helipad and ensure that the tail rotor is not allowed to
intrude into that walkway or zone. Parking or landing with the
tail rotor off the platform ensures personnel safety. Always
per form a stability check prior to reducing rpm to ensure
the landing gear is on firm terrain that can safely support
the weight of the helicopter. Accomplish this by slowly
moving the cyclic and pedals while lowering the collective.
If movement is detected, reposition the aircraft.
Takeoff
A pinnacle takeoff is considered an airspeed over altitude
maneuver which can be made from the ground or from a
hover. Since pinnacles and ridgelines are generally higher
than the immediate surrounding terrain, gaining airspeed
on the takeoff is more important than gaining altitude. As
airspeed increases, the departure from the pinnacle becomes
more rapid, and helicopter time in the avoid area of the
height/velocity area decreases. [Figure 11-3] In addition
to covering unfavor able terrain rapidly, a higher airspeed
affords a more favorable glide angle and thus contributes to
the chances of reaching a safe area in the event of a forced
landing. If a suitable forced landing area is not avail able, a
higher airspeed also permits a more effective flare prior to
making an autorotative landing.
On takeoff, as the helicopter moves out of ground effect,
maintain altitude and accelerate to normal climb airspeed.
When normal climb speed is attained, estab lish a normal
climb attitude. Never dive the helicopter down the slope after
clearing the pinnacle.
Common Errors
1. Failing to perform, or improper performance of, a high
or low reconnaissance.
2. Flying the approach angle too steep or too shal low for
the existing conditions.
3. Failing to maintain proper rpm.
4. Failing to consider emergency landing areas.
5. Failing to consider how wind and turbulence could
affect the approach and takeoff.
6. Failure to maintain pinnacle elevation after takeoff.
7. Failure to maintain proper approach rate of closure.
8. Failure to achieve climb airspeed in timely manner.
Chapter Summary
This chapter described advanced flight maneuvers such
as slope landings, confined area landings, and running
takeoffs. The correlation between helicopter performance
requirements, the environmental factors associated with
different flight techniques, and safety considerations were
also explained to familiarize the pilot with the measures that
can be taken when performing these maneuvers to mitigate
risks. Hazards associated with helicopter flight and certain
aerodynamic considerations were also discussed.
Introduction
Today, helicopters are quite reliable. However, emergencies
do occur, whether a result of mechanical failure or pilot
error, and should be anticipated. Regardless of the cause, the
recovery needs to be quick and precise. By having a thorough
knowledge of the helicopter and its systems, a pilot is able
to handle the situation more readily. Helicopter emergencies
and the proper recovery procedures should be discussed and,
when possible, practiced in flight. In addition, by knowing
the conditions that can lead to an emergency, many potential
accidents can be avoided.
Helicopter Emergencies and
Hazards
Chapter 11
Normal Powered Flight Autorotation
Direction of flight
Direction of flight
Figure 11-1. During an autorotation, the upward flow of relative wind permits the main rotor blades to rotate at their normal speed. In
effect, the blades are “gliding” in their rotational plane.
Several factors affect the rate of descent in autorotation:
bank angle, density altitude, gross weight, rotor rpm, trim
condition, and airspeed. The primary ways to control the rate
of descent are with airspeed and rotor rpm. Higher or lower
airspeed is obtained with the cyclic pitch control just as in
normal powered flight. In theory, a pilot has a choice in the
angle of descent, varying, from straight vertical to maximum
horizontal range (which is the minimum angle of descent).
Rate of descent is high at zero airspeed and decreases to a
minimum at approximately 50–60 knots, depending upon the
particular helicopter and the factors just mentioned. As the
airspeed increases beyond that which gives minimum rate
of descent, the rate of descent increases again.
When landing from an autorotation, the only energy available
to arrest the descent rate and ensure a soft landing is the
kinetic energy stored in the rotor blades. Tip weights can
greatly increase this stored energy. A greater amount of
rotor energy is required to stop a helicopter with a high
rate of descent than is required to stop a helicopter that is
descending more slowly. Therefore, autorotative descents
at very low or very high airspeeds are more critical than
those performed at the minimum rate of descent airspeed.
Refer to the height/velocity diagram discussion in Chapter
7, Helicopter Performance.
Each type of helicopter has a specific airspeed and rotor rpm
at which a power-off glide is most efficient. The specific
airspeed is somewhat different for each type of helicopter,
but certain factors affect all configurations in the same
manner. In general, rotor rpm maintained in the low green
area (see Figure 5-3) gives more distance in an autorotation.
Heavier helicopter weights may require more collective to
control rotor rpm. Some helicopters need slight adjustments
to minimum rotor rpm settings for winter versus summer
Autorotation
In a helicopter, an autorotative descent is a power-off
maneuver in which the engine is disengaged from the
main rotor disk and the rotor blades are driven solely by
the upward flow of air through the rotor. [Figure 11-1] In
other words, the engine is no longer supplying power to
the main rotor.
The most common reason for an autorotation is failure of the
engine or drive line, but autorotation may also be performed
in the event of a complete tail rotor failure, since there is
virtually no torque produced in an autorotation. In both
cases, maintenance has often been a contributing factor to the
failure. Engine failures are also caused by fuel contamination
or exhaustion as well resulting in a forced autorotation.
If the engine fails, the freewheeling unit automatically
disengages the engine from the main rotor, allowing it to
rotate freely. Essentially, the freewheeling unit disengages
anytime the engine revolutions per minute (rpm) is less than
the rotor rpm.
At the instant of engine failure, the main rotor blades are
producing lift and thrust from their angle of attack (AOA)
and velocity. By lowering the collective (which must be done
immediately in case of an engine failure), lift and drag are
reduced, and the helicopter begins an immediate descent,
thus producing an upward flow of air through the rotor disk.
This upward flow of air through the rotor disk provides
sufficient thrust to maintain rotor rpm throughout the descent.
Since the tail rotor is driven by the main rotor transmission
during autorotation, heading control is maintained with the
antitorque pedals as in normal flight.
conditions, and high altitude versus sea level flights. For
specific autorotation airspeed and rotor rpm combinations for
a particular helicopter, refer to the Rotorcraft Flight Manual
(RFM). The specific airspeed and rotor rpm for autorotation
is established for each type of helicopter based on average
weather, calm wind conditions, and normal loading. When
the helicopter is operated with heavy loads in high density
altitude or gusty wind conditions, best performance is
achieved from a slightly increased airspeed in the descent.
For autorotation at low density altitude and light loading,
best performance is achieved from a slight decrease in
normal airspeed. Following this general procedure of fitting
airspeed and rotor rpm to existing conditions, a pilot can
achieve approximately the same glide angle in any set of
circumstances, and thereby estimate the touchdown point
accurately.
It is important that pilots experience autorotations from
various airspeeds. This provides better understanding of
the necessary flight control inputs to achieve the desired
airspeed, rotor rpm and autorotation performance, such
as the maximum glide or minimum descent airspeed. The
decision to use the appropriate airspeed and rotor rpm for
the given conditions should be instinctive to reach a suitable
landing area. The helicopter glide ratio is much less than
that of a fixed-wing aircraft and takes some getting used to.
The flare to land at 80 knots indicated airspeed (KIAS) will
be significantly greater than that from 55 KIAS. Rotor rpm
control is critical at these points to ensure adequate rotor
energy for cushioning the landing.
Use collective pitch control to manage rotor rpm. If rotor rpm
builds too high during an autorotation, raise the collective
sufficiently to decrease rpm back to the normal operating
range, then reduce the collective to maintain proper rotor rpm.
If the collective increase is held too long, the rotor rpm may
decay rapidly. The pilot would have to lower the collective
in order to regain rotor rpm. If the rpm begins decreasing,
the pilot must again lower the collective. Always keep the
rotor rpm within the established recommended range for the
helicopter being flown.
RPM Control
Rotor rpm in low inertia rotor systems has been studied
in simulator flight evaluations which indicate that the
simultaneous application of aft cyclic, down collective,
and alignment with the relative wind (trim) at a wide range
of airspeeds, including cruise airspeeds, is critical for all
operations during the entry of an autorotation. The applicable
Rotorcraft Flight Manual (RFM) should be consulted to
determine the appropriate procedure(s) for safely entering an
autorotation. This is vitally important since the procedure(s)
for safely entering an autorotation may vary with specific
makes and/or models of helicopters. A basic discussion of
the aerodynamics and control inputs for single rotor systems
is in order here.
Helicopter pilots must understand the use of the collective
for rotor rpm control during power off autorotations in a turn.
Upward movement of the collective reduces the rpm and
downward movement increases the rpm. Cyclic movement
is primarily associated with attitude/airspeed control in
powered flight but may not be given the credit appropriate
for rotor rpm control during practice and emergency power
off autorotations. As long as the line of cyclic movement is
parallel with the flight path of the helicopter (trimmed), the
aft movement of the cyclic also creates greater air flow up
through the bottom of the rotor disk and contributes to an
increase in rotor rpm. If the flight path is 10 degrees to the
right of the longitudinal axis of the helicopter, theoretically,
the cyclic should be moved 10 degrees aft and left of the
longitudinal axis to get maximum air up through the rotor
system.
As the pilot lowers the collective in reaction to a loss of
power during cruise flight there may be a tendency for the
nose of the helicopter to pitch down. As a result, the pilot may
tend to lean forward slightly, which delays the application
of simultaneous aft cyclic to prevent the pitch change and
associated loss of rotor rpm. A slight gain in altitude at cruise
airspeed during the power off entry into an autorotation
should not be of great concern as is the case for the execution
of practice or actual quick stops.
Various accident investigations have concluded that, when
faced with a real power failure at cruise airspeed, pilots are
not simultaneously applying down collective, aft cyclic, and
antitorque pedal inputs in a timely manner. Low inertia rotor
systems store less kinetic energy during autorotation and, as
a result, rotor rpm decays rapidly during deceleration and
touchdown. Conversely, less energy is required to regain
safe rotor rpm during autorotation entry and autorotative
descent. The pilot should immediately apply simultaneous
down collective, aft cyclic and trim the helicopter for entry
into an autorotation initiated at cruise airspeed. If rotor rpm
has been allowed to decrease, or has inadvertently decreased
below acceptable limits, an application of aft cyclic may
help rebuild rotor rpm. This application of aft cyclic must
be made at least at a moderate rate and may be combined
with a turn, either left or right, to increase airflow through
the rotor system. This will work to increase rotor rpm. Care
should be maintained to not over-speed the rotor system as
this is attempted.
Risk Management during Autorotation Training
The following sections describe enhanced guidelines for
autorotations during rotorcraft/helicopter flight training,
as stated in Advisory Circular (AC) 61-140. There are
Figure 11-2. Straight-in autorotation.
risks inherent in performing autorotations in the training
environment, and in particular the 180-degree autorotation.
This section describes an acceptable means, but not the
only means, of training applicants for a rotorcraft/helicopter
airman certificate to meet the qualifications for various
rotorcraft/helicopter ratings. You may use alternate methods
for training if you establish that those methods meet the
requirements of the Helicopter Flying Handbook (HFH),
FAA practical test standards (PTS), and the Rotorcraft Flight
Manual (RFM).
Straight-In Autorotation
A straight-in autorotation is one made from altitude with
no turns. Winds have a great effect on an autorotation.
Strong headwinds cause the glide angle to be steeper due
to the slower groundspeed. For example, if the helicopter
is maintaining 60 KIAS and the wind speed is 15 knots,
then the groundspeed is 45 knots. The angle of descent will
be much steeper, although the rate of descent remains the
same. The speed at touchdown and the resulting ground run
depend on the groundspeed and amount of deceleration. The
greater the degree of deceleration, or flare, and the longer
it is held, the slower the touchdown speed and the shorter
the ground run. Caution must be exercised at this point as
the tail rotor will be the component of the helicopter closest
to the ground. If timing is not correct and a landing attitude
not set at the appropriate time, the tail rotor may contact the
ground causing a forward pitching moment of the nose and
possible damage to the helicopter.
A headwind is a contributing factor in accomplishing a slow
touchdown from an autorotative descent and reduces the
amount of deceleration required. The lower the speed desired
at touchdown, the more accurate the timing and speed of the
flare must be, especially in helicopters with low-inertia rotor
disks. If too much collective is applied too early during the
final stages of the autorotation, the kinetic energy may be
depleted, resulting in little or no cushioning effect available.
This could result in a hard landing with corresponding
damage to the helicopter. It is generally better practice to
accept more ground run than a harder landing with minimal
groundspeed. As proficiency increases, the amount of ground
run may be reduced.
Technique (How to Practice)
Refer to Figure 11-2 (position 1). From level flight at
the appropriate airspeed (cruise or the manufacturer’s
recommended airspeed), 500–700 feet above ground level
(AGL), and heading into the wind, smoothly but firmly
lower the collective to the full down position. Use aft cyclic
to prevent a nose low attitude while maintaining rotor rpm
in the green arc with collective. If the collective is in the
full down position, the rotor rpm is then being controlled by
the mechanical pitch stops. During maintenance, the rotor
stops must be set to allow minimum autorotational rpm with
a light loading. This means that collective will still be able
to be reduced even under conditions of extreme reduction of
vertical loading (e.g., very low helicopter weight, at very low-
density altitude). After entering an autorotation, collective
pitch must be adjusted to maintain the desired rotor rpm.
Coordinate the collective movement with proper antitorque
pedal for trim, and apply cyclic control to maintain proper
airspeed. Once the collective is fully lowered, decrease
throttle to ensure a clean split/separation of the needles. This
means that the rotor rpm increases to a rate higher than that of
the engine—a clear indication that the freewheeling unit has
allowed the engine to disconnect. After splitting the needles,
readjust the throttle to keep engine rpm above normal idling
speed, but not high enough to cause rejoining of the needles.
See the RFM for the manufacturer's recommendations for
autorotation rate of descent.
At position 2, adjust attitude with cyclic to obtain the
manufacturer’s recommended autorotation (or best gliding)
speed. Adjust collective as necessary to maintain rotor rpm
in the lower part of the green arc (see page 11-2). Aft cyclic
movements cause an increase in rotor rpm, which is then
controlled by a small increase in collective. Avoid a large
collective increase, which results in a rapid decay of rotor
rpm, and leads to “chasing the rpm.” Avoid looking straight
down in front of the aircraft. Continually crosscheck attitude,
trim, rotor rpm, and airspeed.
At the altitude recommended by the manufacturer (position
3), begin the flare with aft cyclic to reduce forward airspeed
and decrease the rate of descent. Maintain heading with the
antitorque pedals. During the flare, maintain rotor rpm in
the green range. In the execution of the flare, care must be
taken that the cyclic be moved rearward neither so abruptly
that it causes the helicopter to climb, nor so slowly that it
fails to arrest the descent, which may allow the helicopter
to settle so rapidly that the tail rotor strikes the ground. In
most helicopters, the proper flare attitude is that resulting in a
groundspeed of a slow run. When forward motion decreases
to the desired groundspeed—usually the lowest possible
speed (position 4)—move the cyclic forward to place the
helicopter in the proper attitude for landing.
This action gives the student an idea of airframe attitude to
avoid, because a pilot should never allow ground contact
unless the helicopter is more nose-low than that attitude.
Limiting the flare to that attitude may result in slightly faster
touchdown speeds but will eliminate the possibility of tail
rotor impact on level surfaces.
The landing gear height at this time should be approximately
3–15 feet AGL, depending on the altitude recommended by
the manufacturer. As the apparent groundspeed and altitude
decrease, the helicopter must be returned to a more level
attitude for touchdown by applying forward cyclic. Some
helicopters can be landed on the heels in a slightly nose high
attitude to help decrease the forward groundspeed, whereas
others must land skids or landing gear level, in order to spread
the landing loads equally to all of the landing gear. Extreme
caution should be used to avoid an excessive nose high and
tail low attitude below 10 feet. The helicopter must be close
to the landing attitude to keep the tail rotor from contacting
the surface.
At this point, if a full touchdown landing is to be performed,
allow the helicopter to descend vertically (position 5). This
collective application uses some of the kinetic energy in the
rotor disk to help slow the descent rate of the helicopter.
When the collective is raised, the opposite antitorque pedal
used in powered flight will be needed due to the friction
within the transmission/drive train. Touch down in a level
flight attitude.
Control response with increased pitch angles will be slightly
different than normal. With a decrease in main rotor rpm,
the antitorque authority is reduced (the pedals react more
slowly), requiring larger control inputs to maintain heading
at touchdown.
Some helicopters, such as the Schweitzer 300, have a canted
tail stabilizer. With a canted stabilizer, it is crucial that the
pilot apply the appropriate pedal input at all times during the
autorotation. If not the tailboom tends to swing to the right,
which allows the canted stabilizer to raise the tail. This can
result in a severe nose tuck which is quickly corrected with
right pedal application.
A power recovery can be made during training in lieu of a full
touchdown landing. Refer to the section on power recovery
for the correct technique.
After the helicopter has come to a complete stop after
touchdown, lower the collective pitch to the full-down
position. Do not try to stop the forward ground run with aft
cyclic, as the main rotor blades can strike the tail boom. By
lowering the collective slightly during the ground run, an
increase in weight is placed on the landing carriage, slowing
the helicopter; however, this is dependent on the condition
of the landing surface.
One common error is the holding of the helicopter off the
surface, versus cushioning it onto the surface during an
autorotation. Holding the helicopter in the air by using all of
the rotor rpm kinetic energy usually causes the helicopter to
have a hard landing, which results in the blades flexing down
and contacting the tail boom. The rotor rpm should be used
to cushion the helicopter on to the surface for a controlled,
smooth landing instead of allowing the helicopter to drop
the last few inches.
Common Errors
1. Not understanding the importance of an immediate
entry into autorotation upon powerplant or driveline
failure.
2. Failing to use sufficient antitorque pedal when power
is reduced.
3. Lowering the nose too abruptly when power is
reduced, thus placing the helicopter in a dive.
4. Failing to maintain proper rotor rpm during the
descent.
5. Applying up-collective pitch at an excessive altitude,
resulting in a hard landing, loss of heading control,
and possible damage to the tail rotor and main rotor
blade stops.
6. Failing to level the helicopter or achieve the
manufacturers preferred landing attitude.
7. Failing to minimize or eliminate lateral movement
during ground contact. (Similar for items 8 and 9)
8. Failing to maintain ground track in the air and keeping
the landing gear aligned with the direction of travel
during touchdown and ground contact.
9. Failing (in a practice run) to go around if not within
limits and specified criteria for safe autorotation.
Autorotation with Turns
Turns (or a series of turns) can be made during autorotation
to facilitate landing into the wind or avoiding obstacles.
Turns during autorotation should be made early so that the
remainder of the autorotation is flown identically to a straight-
in autorotation. The most common turns in an autorotation
are 90 degrees and 180 degrees. The following technique
describes an autorotation with a 180-degree turn.
The pilot establishes the aircraft on a downwind heading
at the recommended airspeed, and parallel to the intended
touchdown point. Then, taking the wind into account, the pilot
establishes the ground track approximately 200 feet laterally
from the desired course line to the touchdown point. In strong
crosswind conditions, the pilot should be prepared to adjust
the downwind leg closer or farther out, as appropriate. The
pilot uses the autorotation entry airspeed recommended by
the RFM. When abeam the intended touchdown point, the
pilot smoothly reduces collective, then reduces power to the
engine to show a split between the rotor rpm and engine rpm
and simultaneously applies appropriate anti-torque pedal
and cyclic to maintain proper attitude/airspeed. Throughout
the autorotation, the pilot should continually crosscheck the
helicopter’s attitude, rotor rpm, airspeed, and verify that the
helicopter is in trim (centered trim ball).
After the descent and autorotation airspeed is established, the
pilot initiates the 180-degree turn. For training operations,
initially roll into a bank of at least 30 degrees, but no more
than 60 degrees. It is important to maintain the proper
airspeed, rotor rpm, and trim (centered trim ball) throughout
the turn. Changes in the helicopter’s attitude and the angle
of bank causes a corresponding change in rotor rpm within
normal limits. Do not allow the nose to pitch up or down
excessively during the maneuver, as it may cause undesirable
rotor rpm excursions.
Pitot-static airspeed indications may be unreliable or lag
during an autorotational turn. The pilot should exercise
caution to avoid using excessive aircraft pitch attitudes and to
avoid chasing airspeed indications in an autorotational turn.
Note: Approaching the 90-degree point, check the position of
the landing area. The second 90 degrees of the turn should
end with a roll-out on a course line to the landing area. If the
helicopter is too close, decrease the bank angle (to increase
the radius of turn); if too far out, increase the bank angle
(to decrease the radius of the turn). A bank angle of no more
than 60 degrees should be encountered during this turn.
Monitor the trim ball (along with one’s kinesthetic sense)
and adjust as necessary with cyclic and anti-torque pedal
to maintain coordinated flight. Prior to passing through
200 feet above ground level (AGL), if landing or making a
surface-level power recovery, the turn should be completed,
and the helicopter aligned with the intended touchdown
area. Upon reaching the course line, set the appropriate
crosswind correction. If the collective pitch was increased
to control the rpm, it may need to be lowered on rollout to
prevent decay in rotor rpm.
This maneuver should be aborted at any point the following
criteria is not met: if the helicopter is not in a stabilized
approach to landing profile (i.e., it is not aligned as close
as possible into the wind with the touchdown point, after
completing the 180-degree turn); if the rotor rpm is not within
limits; if the helicopter is not at a proper attitude/airspeed; or
if the helicopter is not under proper control at 200 feet AGL.
It is essential that the pilot on the controls (or a certificated
flight instructor (CFI), when intervening) immediately abort
the maneuver and execute a smooth power recovery and go-
around. It is important for the CFI who is intervening at this
point to remember that the go-around is a far safer option than
trying to recover lost rotor rpm and reestablish or recover to
the hover or even the preferred hover taxi.
From all entry positions, but particularly true of the
180-degree entry, a primary concern is getting the aircraft
into the course line with as much altitude as possible. Once
the collective has been lowered and the engine set to flight
idle, the helicopter will lose altitude. A delayed turn will
result in a lower altitude when arriving on the course line.
Additionally, an uncoordinated flight condition (trim-ball
not centered) results in an increased sink rate, which may
be unrecoverable if not corrected.
During the turn to the course line, the pilot should use a
scan pattern to see outside as well as inside the cockpit. Of
primary importance outside is maintaining the appropriate
descending attitude and a proper turn rate. Essential items to
scan inside are rotor rpm and centered trim ball. Rotor rpm
will build anytime “G” forces are applied to the rotor system.
Usually, this occurs in the turn to the course line and during
the deceleration flare.
Throughout the maneuver, rotor rpm should be maintained
in the range recommended in the RFM. Rotor rpm outside
of the recommended range results in a higher rate of descent
and less glide-ratio. When the rotor rpm exceeds the desired
value as a result of increased G load in the turn, timely
use of up collective will increase the pitch of the blades
and slow the rotor to the desired rpm. In an autorotation,
rotor rpm is the most critical element, as it provides the lift
required to stabilize an acceptable rate of descent and the
energy necessary to cushion the landing. Collective should
be lowered to the full down position to maintain rotor rpm
immediately following a loss of power. However, rapid or
abrupt collective movement could lead to mast bumping in
some rotorcraft with teetering rotor systems.
Energy is a very important property of all rotating
components, and the kinetic energy stored in the rotor system
is used to cushion the landing. More lift is produced at the
bottom of an autorotation by raising the collective, which
increases the angle of attack of the blades. The rotor rpm will
also rapidly decay at this point and it is essential to properly
time the flare and the final collective pull to fully arrest the
descent and cushion the landing. Upon arriving into the
course line prior to the flare, the scan should focus almost
entirely outside. The scan should include:
• The horizon for attitude, ground track, and nose
alignment;
• the altitude to set the flare and for closure (groundspeed);
and
• the instrument cross-check of airspeed, rotor rpm, and
engine rpm in the descent.
Every autorotational flare will be different depending on the
existing wind conditions, airspeed, density altitude (DA),
and the aircraft gross weight. A pilot operating a helicopter
at a high DA needs to take into account the effects on the
control of the helicopter when recovering from an aborted
autorotation.
Some effects to consider are:
• Higher rate of descent.
• Reduced rotor rpm builds in autorotation.
• Low initial rotor rpm response in autorotation.
• The requirement for a higher flare height.
• Reduced engine power performance.
Common Errors
The following common errors should be prevented:
1. Entering the maneuver at an improper altitude or
airspeed.
2. Entering the maneuver without a level attitude (or not
in coordinated flight).
3. Entering the maneuver and not correcting from the
initial deceleration to a steady state attitude (which
allows excessive airspeed loss in the descent).
4. Improper transition into the descent on entry.
5. Improper use of anti-torque on entry.
6. Failure to establish the appropriate crosswind
correction, allowing the aircraft to drift.
7. Failure to maintain coordinated flight through the tum.
8. Failure to maintain rotor rpm within the RFM
recommended range.
9. Excessive yaw when increasing collective to slow rate
of descent during power recovery autorotations.
10. During power recovery autorotations, a delay in
reapplying power.
11. Initial collective pull either too high or too low.
12. Improper flare (too much or not enough).
13. Flaring too low or too high (AGL).
14. Failure to maintain heading when reapplying power.
15. Not landing with a level attitude.
16. Landing with aircraft not aligned with the direction
of travel.
17. Insufficient collective cushioning during full
autorotations.
18. Abrupt control inputs on touchdown during full
autorotations.
Practice Autorotation with a Power Recovery
A power recovery is used to terminate practice autorotations
at a point prior to actual touchdown. After the power
recovery, a landing can be made or a go-around initiated.
Technique (How to Practice)
At approximately 3–15 feet landing gear height AGL,
depending upon the helicopter being used, begin to level the
helicopter with forward cyclic control. Avoid excessive nose-
high, tail-low attitude below 10 feet. Just prior to achieving
level attitude, with the nose still slightly up, coordinate
upward collective pitch control with an increase in the
throttle to join the needles at operating rpm. The throttle and
collective pitch must be coordinated properly.
If the throttle is increased too fast or too much, an engine
overspeed can occur; if throttle is increased too slowly or too
little in proportion to the increase in collective pitch, a loss of
rotor rpm results. Use sufficient collective pitch to stop the
descent, but keep in mind that the collective pitch application
must be gradual to allow for engine response. Coordinate
proper antitorque pedal pressure to maintain heading. When
a landing is to be made following the power recovery, bring
the helicopter to a hover and then descend to a landing.
In nearly all helicopters, when practicing autorotations with
power recovery, the throttle should be at the flight setting at
the beginning of the flare. As the rotor disk begins to dissipate
its energy, the engine is up to speed as the needles join when
the rotor decreases into the normal flight rpm.