MH-60R - Maneuvers

Question 0

How to do a normal takeoff

Answer 0

Align the helicopter with the desired takeoff course in a stabilized 10-foot hover or an altitude permitting safe obstacle and terrain clearance. Smoothly apply forward cyclic pressure to begin acceleration into effective translational lift. As the helicopter transitions from hovering to forward flight, the change in direction of the main rotor thrust vector will result in a loss of lift, which tends to cause the helicopter to settle. As airspeed increases through translational lift (approximately 15 knots), the power requirements to maintain level flight will decrease and more power will be available to climb.

Question 1

What shall the PAC do for all takeoffs?

Answer 1

The Pilot Not At the Controls (PNAC) shall monitor all systems (e.g., stabilator, engines, transmissions) during takeoff to alert the Pilot At the Controls (PAC) of malfunctions.

Question 2

How to do a takeoff to a hover

Answer 2

With cyclic slightly aft of neutral, increase collective until desired hovering altitude is reached (normally a 10-foot wheel height). Use pedals to maintain heading as collective is increased. The normal hover attitude is 4 to 5° nose up and 2 to 3° left wing down.
Perform the following checks in a hover:
1. Flight controls— Note correct response.
2. System and flight instruments — Check.
3. Power — Check.

Question 3

How to do a running takeoff

Answer 3

Running takeoffs should be used under conditions of high gross weight and high density altitude(DA) where the power available may not be sufficient to make a vertical takeoff. Contingency power should be selected. Move the cyclic slightly forward of neutral and apply enough collective to start a forward roll while maintaining heading with pedals. Maintain cyclic and collective settings until passing through effective translational lift. Apply enough power for the helicopter to leave the ground. Continue to climb and accelerate, transitioning to a normal climb.

Question 4

How to do a maximum gross weight takeoff

Answer 4

The decision to use the following takeoff technique shall be based on an evaluation of the conditions and helicopter performance. Contingency power should be selected if required. Position aircraft into the wind, and apply power smoothly by increasing collective pitch to raise the helicopter to a low hovering altitude. While slowly increasing forward cyclic, maximum power shall be smoothly applied to continue the takeoff, gradually accelerating and maintaining the low hover altitude. As translational lift is attained, adjust the nose to begin an accelerating climb. The critical period is over when translational airspeed is accelerated through; however, the climbout should remain shallow until airspeed has increased above 50 KIAS to ensure best single-engine performance characteristics.

Question 5

How to do an obstacle clearance takeoff

Answer 5

From a hover, a vertical climb is initiated using coordinated cyclic, pedals, and collective up to TGT or torque limiting. Once the desired altitude is reached, transition to forward flight/climb as desired. Maintaining clearance from obstacles is the most important aspect of this takeoff, not rapidity. Crewmen should be positioned at the cabin doors to ensure tail rotor clearance. Do not exceed TGT or torque limitations. HSI Hover Mode should be used if available to increase pilot situational awareness.

Question 6

How to do an air taxi?

Answer 6

From a stabilized hover, apply forward cyclic pressure to begin forward movement. Desired heading may be retained with pedals or the HDG TRIM switch, and altitude with collective. Changes in direction should be made primarily with pedal control or the HDG TRIM switch to avoid excessive bank angles. To stop forward movement, apply aft cyclic pressure while coordinating collective and pedals to hold desired altitude and heading.

Question 7

How to do sideward/rearward flight

Answer 7

From a stabilized hover, apply cyclic pressure in the desired direction of flight to begin sideward or rearward movement. Maintain desired heading with pedals and altitude with collective. To return to a stationary hover, apply cyclic pressure opposite to the direction of movement by coordinating collective and pedal. The RADALT hold and heading-hold features of the AFCS may be used to hold desired altitude and heading.

Question 8

How to do hovering turns

Answer 8

Hovering turns may be accomplished in one of two ways. The conventional flight control system may be used by applying pressure on the desired tail rotor pedal to begin the turn, using pressure and counterpressure on pedals as necessary to hold the desired rate of turn. The pilot may also turn by depressing the HDG TRIM switch in the desired direction and a turn will be effected at 3o per second. In either case, coordinate cyclic and collective as required to hold desired attitude and altitude.

Question 9

How to execute a climb

Answer 9

The procedures for establishing a climb will vary depending on when the climb was initiated (i.e., transition to forward flight, running takeoff, obstacle clearance). Regardless of the type of climb desired, refer to the climb charts to obtain the profile that will yield best rate-of-climb speed.

Question 10

How to conduct Night/IMC overwater descent

Answer 10

The following procedures shall be performed for all night/IMC descents over water at 1,000 feet AGL and below:

WARNING:
Failure to follow night/IMC descent procedures over water may lead to a loss of situational awareness and result in water impact.

Descent:
1. The PAC reports “ON INSTRUMENTS” and states the leaving altitude, intended altitude, and variable RAWS/LAWS index position (i.e., set below the intended altitude).
2. The PNAC acknowledges descent commencement, intended altitude, and RAWS/LAWS variable index position.
3. The aircrewman acknowledges the intended altitude. (During the descent, the aircrewman should monitor the altitude via the NAV PARAMETERS table or the altitude display to the maximum extent permitted by the tactical situation.)

Level-off:
1. As the helicopter nears the intended altitude, the PNAC reports 200 feet and 100 feet prior.
2. When level, the PAC reports “LEVEL” and “ALTITUDE HOLD ENGAGED.”

Question 11

How to do a power available check

Answer 11

Power available checks are designed to facilitate the verification of preflight calculations within the context of the actual environmental conditions encountered. By comparing the difference between power available and power required, aircrews can make an educated decision on whether they can accomplish the assigned task under a given safety tolerance. Since power available checks can place the aircraft near the edge of its operating envelope, power available checks should be conducted smoothly, allowing the aircraft to stabilize within limits. Continuous TRQ and Ng limits should be utilized to the maximum extent possible for power available checks.

Question 12

How to do an approach to landing

Answer 12

An approach should be a precise maneuver. Approaches should not be made so low that the PAC loses sight of the landing point nor so high that a very low power setting with a high rate of descent is required. Approach speed will depend on weight, altitude, and wind conditions. Maintain translational lift as long as possible while avoiding excessive flares and abrupt, large power inputs. The PNAC shall monitor all systems (e.g., stabilator, engines, transmission) during the approach and landing to alert the PAC of malfunctions.

Question 13

How to do a normal approach

Answer 13

Before commencing a normal landing, ensure the Landing Checklist is complete. The landing is approached from an abeam position of approximately 500 feet AGL at an airspeed of 75 to 100 KIAS, so as to arrive at the 90o position at approximately 300 feet AGL and 60 to 80 KIAS. Continue the descent to roll wings-level into the wind with approximately 1,000 feet of straightaway at 150 to 200 feet AGL and 50 to 70 KIAS. Initiate a decelerating attitude and maintain this attitude until the airspeed decreases to approximately 20 KIAS and 30 feet on the radar altimeter.

At 30 feet, adjust the nose attitude (15o nose-up maximum) and increase collective to achieve a hover at approximately 10 feet. Maintain heading and attitude using the tail rotor pedals and cyclic. When transition to a hover is not possible and running landings are not feasible, normal approach procedures may be used for a no-hover landing.

Question 14

How to do a steep approach

Answer 14

A normal approach is flown until reaching the final inbound course to the landing site. Level off at approximately 200 feet AGL, transition to approximately 40 KGS, and intercept the glideslope (approximately 20 to 30o). Reduce power to begin the descent. While descending, do not exceed 700 fpm and maintain translational lift until reaching ground effect. Should rate of descent become excessive or the approach angle become excessively steep, execute a waveoff. The approach may be flown to a hover or no-hover landing as desired.

Question 15

Wha is the warning and caution associated with landings?

Answer 15

WARNING
Extreme aft cyclic in conjunction with low or decreasing collective settings may cause Droop Stop Pounding (DSP) or contact with the ALQ-144A/205. Rapid aft cyclic movement in conjunction with low collective settings may also cause main rotor blades to strike the tail pylon, resulting in loss of tail rotor drive.

CAUTION
Nose attitudes in excess of 13° nose-up at altitudes less than or equal to 15 feet will cause the tail bumper/stabilator to impact the ground.

Question 16

How to do a vertical landing from a hover

Answer 16

The most important consideration in making a vertical landing is arresting lateral drift. Commence a vertical descent. The aircraft will touch down tailwheel first, then left main mount, and last, right main mount due to the normal nose up, left wing down hover attitude. As the collective is lowered, the tip path will tend to move right wing down due to control mixing.

Question 17

How to conduct a crosswind landing?

Answer 17

When a crosswind approach is necessary, it is best to bring the helicopter to a hover and perform a hovering turn into the wind before landing. When this cannot be done, execute a flare and hover as though making a normal approach into the wind. Arrest all drift before touching down. In strong wind, it will be necessary to hold the helicopter in a slip using cross control to touch down first on the upwind wheel and tailwheel. After touchdown, allow the helicopter to settle on the other wheel.

Question 18

How to conduct a running landing

Answer 18

Running landings are usually made from a shallow approach when the helicopter cannot hover due to insufficient power available or loss of tail rotor control. Adjust collective as necessary to maintain the desired approach angle; dissipate speed gradually throughout the approach so the landing can be made while maintaining translational lift. A running landing should not be attempted on rough terrain. Establish a straight track over the ground and a shallow approach with a slow rate of descent. Use tail rotor pedals to maintain heading in the direction of track and cyclic to control drift. Eliminate all lateral drift before touchdown. As the helicopter approaches the ground, increase collective slightly to reduce rate of descent and adjust airspeed to a value compatible with gross weight. Do not exceed groundspeed limitations. As the wheels contact the ground, tailwheel first then main gear, move the cyclic to the neutral position and slowly decrease collective to minimum. Stop the helicopter with the wheel brakes. Avoid overbraking, especially at high gross weights.

Question 19

How to prevent rotor head damage and extend dynamic component life during a running landing

Answer 19

Excessive aft cyclic should be avoided after touchdown. To avoid this during a running landing:

1. Control airspeed prior to the main wheels touching down. Avoid aerodynamic braking with cyclic.
2. Be aware of the tip path plane; excessive aft cyclic will place the tip path unusually high in the field of view.
3. Consciously reposition the cyclic forward prior to lowering collective.

Question 20

How to conduct a no-hover landing

Answer 20

A no-hover landing is accomplished in the same manner as a normal approach to a hover. Continue descent through the hovering altitude to touchdown on the tailwheel with little or no forward roll. Maintain the landing attitude (approximately 5o nose-up) with collective and aft cyclic until all forward movement is stopped, then lower the main landing gear to the ground.

Question 21

How to conduct Unprepared surface landing

Answer 21

This maneuver may be required under many different circumstances, regardless of the mission. The first step is a thorough study of the landing environment.

Once it has been determined that a safe landing can be made, the PIC should decide which type of landing to use. Although a Tactical Approach and/or a no-hover landing will minimize brownout/whiteout, a hover to a landing will better afford the crew the opportunity to clear the aircraft of all obstacles before touchdown. Both options should be considered.

Question 22

How to do a confined area landing

Answer 22

A confined area landing profile is conducted to Landing Zones (LZ) that, due to obstacles, are not accessible using a normal approach or tactical approach profile. The CAL maneuver will afford the helicopter the safest available route of approach for landing as well as the capability to safely take off and depart the LZ. The maneuver starts by aligning the aircraft on final approach to the confined area intended for landing. Slow the aircraft to 20 KGS or less by the time it crosses the last obstruction on the approach end of the LZ. When the aircraft is cleared to descend, simultaneously use aft cyclic and decreasing collective to stop forward motion and begin the descent. Drift in both the fore/aft and left/right directions must be controlled throughout the maneuver.

Question 23

What does a standard hover attitude look like

Answer 23

Normally, with the stabilator in the full trailing-edge-down position, the aircraft will hover approximately 4 to 5° nose-up and 2 to 3° left-wing-down.

Question 24

Describe the aerodynamics of hover/slow speed flight

Answer 24

In a steady, no-wind hover, the main rotor experiences a symmetrical distribution of lift dictated by the rotational velocity and constant pitch of the rotor blades. The blade tips are moving at 725 feet per second or Mach 0.65 (65 percent of the speed of sound). Since the airflow is subsonic, the movement of the blades through the air is “felt” upstream (Figure 11-1), resulting in an upward movement of air prior to coming in contact with the blade. This “induced” flow causes the lifting force to be shifted aft, resulting in the generation of a drag component referred to as “induced drag.”

Question 25

Describe ground effect

Answer 25

A helicopter is said to be in "ground effect" when the rotor disk is within one rotor diameter of the ground. Ground effect causes the main rotor thrust vector to shift forward so that it is more vertical (more lift/less induced drag); therefore, less power is required to hover in ground effect than at higher altitudes. These effects are strongest close to the ground and dissipate rapidly as altitude above the ground is increased. The MH-60R is considered to be hovering in ground effect at radar altimeter altitudes at or below 45 feet.

Question 26

What are the numbers associated with down wash?

Answer 26

For an MH-60R at the gross weight of 21,700 pounds on a standard sea level day, downwash below the rotor can exceed 50 knots. This results in the generation of a ground vortex that surrounds the aircraft just outside the rotor arc. It is important to consider the effects of rotor downwash and the ground vortex on personnel and other aircraft, particularly much lighter civil aircraft.

Question 27

Describe the aerodynamics of transition to forward flight

Answer 27

In flight regimes other than a hover, the rotor blades, as they move around the rotor head, experience different relative velocities. Hence, an asymmetrical distribution of lift is created. To compensate for this dissymmetry, the blades on the advancing side of the rotor rise (flaps up), decreasing the AOA and reducing the lift generated. The retreating blade flaps down, increasing the AOA and generating additional lift. This process of flapping causes the pitch of the blade to be continuously changing in a cyclic manner. The flapping nature of the rotor system results in a 90° phase lag between where inputs are made and their effects felt.

Question 28

Describe blowback

Answer 28

When hovering in a windless environment, the main rotor disk will be level. If the aircraft is exposed to a headwind gust, the retreating blade sees less relative wind velocity and the advancing blade sees more relative wind velocity. This causes the rotor disk to be tilted aft or "blown back." Blowback of the main rotor disk tilts the main rotor thrust vector aft, causing the nose of the helicopter to pitch up. Blowback makes the helicopter pitch unstable with respect to gusts on the nose. This reaction is countered by pilot input in the long term, and by the hover augmentation and gust alleviation feature of SAS-2, and attitude hold feature of the autopilot in the short term. When transitioning to forward flight, blowback results in more forward cyclic being required to continue acceleration.

Question 29

Describe stabilator effect in slow speed flight below 30 knots

Answer 29

Below 30 KIAS, the stabilator is 42° trailing edge down. Increasing collective in a hover increases the amount of downwash on the stabilator and pushes the nose up. The effect of varying collective position on nose attitude during hover is compensated for by collective-to-longitudinal mechanical control mixing. The airspeed, collective position, lateral acceleration, and pitch rate inputs to the stabilator system have no effect below 30 KIAS. In transition to forward flight, the full-down position of the stabilator will cause a nose-down pitch until programming begins at 30 KIAS. Aft cyclic will be required to counter this pitching moment until programming begins.

Question 30

Describe translational lift

Answer 30

Forward flight is initiated by displacing the cyclic forward. This tilts the rotor thrust vector forward. Tilting the main rotor thrust vector forward reduces the vertical lift component; therefore, additional increase in collective pitch may be necessary as the helicopter begins to translate forward to keep it from descending. With further increase in forward speed, the mass flow rate of air through the rotor system increases, resulting in greater lift production and a rapid decrease in induced power required for level flight. Although profile power (power required to spin the blades) and parasite power (power required to drag non-lifting parts of the helicopter through the air) are both steadily increasing, the reduction in induced power required results in an overall reduction in total power required. Maintaining hover power will result in approximately a 500 foot-per-minute rate of climb at 80 KIAS. As the airspeed reaches approximately 17 knots, a noticeable vibration will be felt as the aircraft encounters its own ground vortex. The ground vortex is rolled up under the aircraft as speed continues to increase and dissipates as the aircraft reaches approximately 30 knots.

Question 31

Describe the aerodynamics of tail winds in transition to forward flight

Answer 31

Normally, a helicopter transitioning to forward flight from a hover is moving toward a state of less power required. This is not the case for an aircraft transitioning to forward flight with a tailwind. When the helicopter is motionless over a spot, the rotor disk does not care which direction the wind is coming from; therefore, a helicopter with a tailwind requires less power to hover than one in calm winds. As the helicopter moves forward, the rotor will reach a condition of zero relative wind when helicopter speed matches tailwind speed. The helicopter moves into a state of more power required for level flight; therefore, even if the aircraft had enough power to hover in a tailwind, it may not have enough power to continue in forward flight and reach translational lift.

Question 32

Describe the aerodynamics of forward flight

Answer 32

Following translational lift, the aircraft will accelerate through 30 KIAS, at which point the stabilator will begin programming the trailing edge upward, requiring forward cyclic movement to continue the helicopter acceleration. When the aircraft passes through 50 KIAS, the AFCS will level the wings to maintain heading in balanced flight. Above 50 KIAS, the beeper trim (or trim release button) must be used to establish the desired forward airspeed. The directional control pedals will automatically move to the position required to maintain balanced flight. Forces opposing incorrect pilot directional flight control input will be felt. An increase in speed is accomplished by using the beeper trim switch, or depressing the trim release button and displacing the cyclic forward until the desired airspeed is attained. This, in turn, tilts the rotor disc forward. As it tilts forward, a greater percentage of the lift being produced by the main rotor is being used to increase the forward airspeed of the helicopter. An increase in power is required to restore the vertical lift component to maintain altitude. The stabilator programs to counter the nose-down attitude experienced as the rotor disc and fuselage tilt forward and will maintain an approximately level nose attitude up to approximately 130 KIAS. The AFCS will maintain the heading, altitude, and airspeed in balanced flight as selected by the pilot.

Question 33

Describe retreating blade stall

Answer 33

The tendency of the retreating blade to stall in forward flight limits the high-speed potential of the helicopter, increases component stresses, and decreases component life. The retreating blade (the blade moving away from the direction of flight) has a tendency to stall because the blade tip is traveling at the rotational velocity minus the forward speed of the helicopter. As the in-air velocity of the retreating blade decreases, the blade Angle of Attack (AOA) must be increased to equalize lift to provide stabilized flight. As the angle of attack increases, the blade will stall (lost lift and increased drag). The increased drag will cause loss of rotor speed, unless power is increased. The advancing blade (the blade moving into the direction of flight), on the other hand, is traveling at a substantially higher speed, has relatively uniform low angles of attack, and is not subject to blade stall. Blade stall will first occur at the blade root and is most likely to occur when operating at high values of speed, gross weight, density altitude, and power. Any of these conditions is especially aggravated by low rotor rpm.

Question 34

What will be encountered in the stall region of the retreating blade stall chart

Answer 34

The blade stall chart establishes the maximum airspeeds to allow for turbulence, mild maneuvers, and necessary control inputs to maintain the desired flight attitude. At these speeds, roughness is encountered, but reasonable maneuvers or mild turbulence can be tolerated. Severe turbulence or abrupt control maneuvers at this point will increase the severity of the stall, and the helicopter will become more difficult to control. In the blade stall condition, each main rotor blade will stall as it passes through the stall region and create vibrations-per-revolution equal to the number of blades. If a stall is allowed to fully develop, loss of control will be experienced, and the helicopter will pitch upward and to the left. The use of forward cyclic to control this pitch up is ineffective and may aggravate the stall as it increases the angle of attack of the retreating blade.

Question 35

Procedure for retreating blade stall

Answer 35

If blade stall is causing roughness in the helicopter during high-speed flight or when maneuvering, either condition may be eliminated by accomplishing one or any combination of the following: 1. Decrease collective pitch. 2. Decrease severity of maneuver. 3. Gradually decrease airspeed. 4. Increase rotor rpm. 5. Decrease altitude. 6. Decrease gross weight.

Question 36

Describe the tractor tail rotor

Answer 36

The tail rotor provides antitorque reaction for helicopter directional control. The MH-60R tail rotor is also designed to provide 2.5 percent of the total lift in hovering flight. This is required due to the MH-60R having a relatively aft center of gravity. Having 2.5 percent of the total lift aft of the center of gravity helps lower aircraft nose attitude in a hover. To provide this lift, the tail rotor is canted 20° from the vertical plane. The effect of varying tail rotor thrust on aircraft nose attitude is compensated for by yaw-to-longitudinal control mixing.

Question 37

Describe loss of tail rotor authority

Answer 37

Loss of tail rotor authority is an issue of power. This is usually seen in high gross weight and/or high density altitude conditions. In these conditions, left pedal response may be sluggish. In extreme cases, main rotor speed will droop. As Nr droops, torque increases while power available to the main rotor and tail rotor decreases rapidly. Eventually, the tail rotor can no longer produce enough thrust to react against the high torque and the helicopter will spin to the right.

Question 38

Describe loss of tail rotor effectiveness

Answer 38

LTE is defined as the inability of the tail rotor to provide sufficient force to maintain yaw controllability. Loss of tail rotor effectiveness occurs when full pedal input is insufficient to provide directional control. Tail rotor thrust is a function of operating rpm and tail rotor angle of attack. The two primary directional control mechanisms are angle of attack and the weather-vaning tendency of the fuselage. Relative wind direction, low-speed/high-power maneuvering, operating rpm, gross weight, and DA are several factors that can contribute to LTE.

Question 39

How do winds affect LTE

Answer 39

Relative wind component has a significant effect on tail rotor effectiveness. Winds from the right tend to decrease angle of attack of the tail rotor for a given pitch setting, reducing effectiveness and requiring additional left pedal to maintain heading. Additional left pedal depletes main rotor power and reduces directional control authority. When operating in high-power, right-crosswind situations, tail rotor effectiveness may be lost. Winds from the left will tend to increase angle of attack on the tail rotor for a given pitch setting and may increase tail rotor effectiveness; however, if the left wind component is excessive, disturbed airflow around the tail rotor may develop, resulting in loss of effectiveness. In any case, high, variable, and/or gusty wind conditions may require full pedal inputs to maintain directional control and precipitate loss of pedal authority.

Question 40

Describe weather vaning

Answer 40

Winds within the region of 120 to 240° relative will tend to weather-vane the nose of the aircraft into the wind. The helicopter will attempt to make an uncommanded left or right turn, depending on wind conditions, unless resisting pedal input is applied. Additionally, if a yaw rate has been established (such as in a pedal turn), weather-vaning will act to accelerate the yaw rate as the tail passes through the wind.

Question 41

Describe tail rotor vortex ring state

Answer 41

Winds within the region of 210 to 330° relative can cause the tail rotor to operate within its own recirculated airflow. This vortex ring state causes tail rotor thrust variations that can initiate yaw rates. Winds primarily from the abeam position can result in large variations of tail rotor thrust. This will cause uncommanded and unpredictable yaw rates and an increase in workload to maintain directional control. If a right yaw rate is allowed to build, the tail of the aircraft may rotate into the wind where the weather-vaning effect will accelerate the yaw rate.

Question 42

Describe Main rotor disc vortex interaction

Answer 42

Winds within the region of primarily 280 to 330°, and less frequently from 30 to 80°, can cause the main rotor vortex to be directed onto the tail rotor, resulting in changes in angle of attack to the tail rotor. Tail rotor thrust can vary unpredictably, resulting in high pedal workload to maintain directional control.

Question 43

Describe loss of translational lift

Answer 43

Loss of translational lift results in increased power demand and additional anti-torque requirements. If the loss of translational lift occurs when the aircraft is in a right turn, the right turn rate will be accelerated if corrective action is not taken. When operating near maximum power available, this increased power demand could result in rotor rpm decay. Insufficient attention to wind direction and velocity can lead to unexpected loss of translational lift. Aircraft heading, ground track, and groundspeed must be continually evaluated.

Question 44

Describe how hover/air-taxi affects LTE

Answer 44

Right sideward flight, or a right crosswind, increases airflow across the tail, resulting in a reduction in Angle of Attack (AOA) for a set pedal position and a reduction in tail rotor thrust. If increased left pedal is applied, a right yaw will occur. Yaw rate will be further amplified by increased airflow over the tail pylon, which will tend to streamline the aircraft. When the aircraft is operated at low wheel heights, main rotor tip vortex can produce an area of downwash turbulence that may interact with the tail rotor. Tail rotor thrust variations may require rapid pedal inputs to maintain directional control.

Question 45

Factors increasing the likelihood of LTE

Answer 45

Recovery from a high right yaw rate is more difficult in conditions requiring higher main rotor power (e.g., high gross weight, high DA, or arresting a high descent rate). Low airspeeds require more power to maintain flight and increased anti-torque requirements. Also, streamlining effect is reduced at lower airspeed. Rapid application of collective may cause transient rotor rpm droop to occur. A decrease in main rotor rpm causes a greater proportional decrease in tail rotor rpm/thrust. Low Nr with left pedal application can cause loss of directional control as tail rotor rpm decays.

Question 46

How to recover from LTE

Answer 46

Should LTE occur, correct and timely response is critical. If the response is incorrect or slow, the yaw rate may accelerate to a point where it is extremely difficult to recover. One or more complete revolutions may be experienced. The appropriate response to LTE can be achieved by: 1. Altitude permitting, lowering the collective to reduce torque and assist in arresting right yaw; however, if a significant rate of descent is established, the additional power required to arrest the rate of descent may aggravate or reinitiate loss of tail rotor effectiveness. 2. Using forward cyclic to increase airspeed and, if necessary, turning in the direction of rotation. This results in a reduction in tail rotor thrust required and produces a streamlining effect. 3. At very low speeds or in a hover, applying full left pedal may arrest the right yaw. Understand that the control inputs may take several seconds/revolutions to take effect partially due to the effects of momentum and ambient conditions. Neutralizing the pedals, adding right pedal, or increasing collective will only accelerate the yaw rate.

Question 47

Describe tail rotor spar loads in maneuvering flight

Answer 47

Counterclockwise turning single main rotor helicopters exhibit transient torque increases in forward flight with roll rates to the left. Left roll rate increases retreating blade AOA, driving torque up, and main rotor precession loads contribute further to this effect. Left roll rates (above approximately 30° per second in forward flight above 75 KIAS) can combine with induced tail rotor gyroscopic and flapping loads to cause excessive tail rotor spar loading.

Question 48

Describe Main Rotor Vertical 4/rev Cueing

Answer 48

During maneuvering flight, main rotor component fatigue damage occurs simultaneously with an increase in main rotor vertical 4/rev vibration level. As an increasing g level is placed on the aircraft, the 4/rev onset will appear and is noticed as an increase in aircraft roughness similar to that of the 4/rev shudder experienced when flying the aircraft through transitional lift. The 4/rev vibration onset is an indication that the lift-generating capability of the main rotor has been exceeded and that a main rotor stall region has been created. Further attempts to increase load factor will only increase the blade stall region, resulting in reduced maneuverability and increased component fatigue damage. If a noticeable increase in main rotor 4/rev vibration level is observed, relax g level slightly until 4/rev vibrations decrease to a normal level. The most effective method of reducing the stall-related main rotor 4/rev vibration level is to reduce collective.

Question 49

Describe main rotor flapping margin

Answer 49

Main rotor flapping margin, a measurement of the amount of blade spindle displacement remaining in the flapping (vertical) axis before blade motion stops are contacted, may be reduced to zero by maneuvers involving large and rapid application of forward cyclic. Main rotor flapping margin is especially reduced when rapid forward cyclic is coupled with low collective settings and/or aft longitudinal cg. CAUTION Inducement of less than 1g flight by rapid application of forward cyclic may result in exceeding main rotor flapping margin limits and droop stop pounding.

Question 50

Describe aerodynamics of high AOB turns

Answer 50

The vertical (lift) component of main rotor thrust decreases with increasing AOB. In order for the aircraft to maintain level flight, main rotor thrust must be increased so that lift will remain equal to weight. For example, if a pilot does not apply additional collective in a 45° AOB turn at 300 feet, the aircraft will crash in less than 5 seconds. Application of additional collective pitch allows the aircraft to perform level turns.

Question 51

Describe g-loading in turns

Answer 51

Accelerated or turning flight (g-loads) can be established by using aft cyclic and/or collective control. Cyclic maneuvering provides a transient maneuvering capability because forward airspeed will decrease. As airspeed decreases, transient rotor thrust decays as a result of less mass flow through the rotor disk; therefore, there is less energy to complete the maneuver. Sustained maneuvering must be accomplished by application of collective power so that the aircraft speed and energy are conserved. Transient g-loads applied using aft cyclic result in airspeed bleed and eventual flight at speed less than bucket speed. Sustained g-loads applied with collective increase power required for level flight at that airspeed (due to AOB), which results in a decrease in excess power. Maneuvers at slow speeds are incapable of resulting in structural damage because the aircraft will encounter an aerodynamic limit of rotor thrust. High-speed maneuvering can result in main rotor transient (cyclic) and sustained (collective) power exceeding structural limitations.

Question 52

Describe rolling pull outs

Answer 52

Another situation where an aircraft can generate high g-loading is during a rolling pullout (Figure 11-4). Due to centrifugal acceleration (g-loading), the weight vector of the aircraft increases. Lift produced by the rotor system must be increased proportionally to the g-load to arrest the descent and establish level flight. Power can be applied by transient power input (aft cyclic) and sustained power input (collective). This can result in a situation where power required for recovery greatly exceeds total power available in the rotor system and "mushing" occurs. During "mushing," the aircraft will continue to descend rapidly even though maximum power may be applied; longitudinal cyclic control will feel sluggish, a noticeable increase in main rotor vertical 4/rev vibrations, and retreating blade stall may occur.

Question 53

Describe High AOB (High-G) Maneuvering Effects on Lateral CG Margin

Answer 53

Helicopter center of gravity limits are based on non-accelerated flight (1g). This is particularly true of lateral center of gravity limits. High angle-of-bank turns narrow the lateral cg margin. With an excessive asymmetrical load (i.e., all stores and/or auxiliary tank on one side), a high AOB turn into the stores-heavy side can reduce the lateral cg margin to the point where there is not enough cyclic authority to roll back out of the turn. This can occur even though the lateral cg position is within static (1g) limits. The result is an uncontrolled spiral into the deck. WARNING In situations where loss of lateral control is experienced in a steep turn and asymmetrical stores load/shift in lateral cg is the suspected cause, consideration should be given to jettisoning the stores. This should shift the lateral cg sufficiently to provide enough control authority to recover from the turn.

Question 54

Describe power required exceeding power available

Answer 54

At high density altitudes, high gross weights, or when operating with reduced power, power required may exceed power available. It may not be possible to maintain level flight due to lack of power, which will cause settling to occur. The attendant loss of altitude is of minor consequence except in certain situations where sufficient altitude is not available to achieve the airspeed necessary to maintain level flight. Careful preflight analysis of engine performance and hover charts will aid in avoiding extreme situations.

Question 55

What are the flow states of the main rotor

Answer 55

There are four flow states of a rotor system: normal thrusting, vortex ring, autorotative, and windmill brake. Each flow state represents a larger rate of descent relative to the induced velocity of the rotor system. In the normal thrusting state of the rotor system, vortices are concentrated at the blade tips. The velocity profile of air relative to the rotor is downward across the entire rotor disk. This is the condition encountered in hover, forward flight, climbing flight, and slow rates of descent.

Question 56

Describe Vortex Ring State

Answer 56

Vortex ring state describes an aerodynamic condition where a helicopter may be in a vertical descent with maximum power applied and little or no cyclic authority. The term “power settling” comes from pilot observations that the helicopter keeps settling even though full engine power is used. In a normal out-of-ground-effect hover, the helicopter is able to remain stationary by propelling a large mass of air down through the main rotor. Near the tips of the blades, some of the air is recirculated, curling up from the bottom of the rotor system and rejoining the air entering the rotor from the top. This phenomenon is common to all airfoils and is known as tip vortices. Tip vortices consume engine power but produce no useful lift. As long as the tip vortices are small, their only effect is a small loss in rotor efficiency; however, when the helicopter begins to descend vertically, it settles into its own downwash, which greatly enlarges the tip vortices. This is the vortex ring state where most power developed by the engines is wasted in accelerating the air in a doughnut pattern around the rotor, while Nr remains at 100 percent.

Question 57

When is vortex ring state measurable

Answer 57

The effect is measurable at descent rates greater than 700 fpm and airspeeds between 0 and 20 KIAS and is the worst at descent rates of approximately 1,500 fpm with airspeeds of 5 to 10 KIAS. Fully developed vortex ring state is characterized by an unstable condition where the helicopter experiences uncommanded pitch and roll oscillations, has little or no cyclic authority, and achieves a descent rate that may approach 6,000 fpm. It is accompanied by increased levels of vibration. WARNING Flight conditions causing vortex ring state should be avoided at low altitudes because of the attendant loss of altitude necessary for recovery. Recovery from fully developed vortex ring state may require entering autorotation before regaining airspeed. Note Vortex ring state may also be entered during any dynamic maneuver that places the main rotor in condition of high upflow and low longitudinal airspeed. This condition is frequently seen during "quick stop" type maneuvers or during autorotational recoveries.

Question 58

How to recover from Vortex Ring State

Answer 58

1. Decrease collective pitch. 2. Increase forward airspeed. 3. Enter autorotation if altitude permits. A considerable loss of altitude may occur before the condition is recognized and recovery is completed. During approach for landing, conditions causing vortex ring state should be avoided.