MH-60R - General NATOPS Flashcards
(105 cards)
How to conduct a no-hover landing
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.
Describe main rotor flapping margin
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.
Describe blowback
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.
How to conduct a crosswind landing?
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.
What are the flow states of the main rotor
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.
Describe Vortex Ring State
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.
How to do a power available check
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.
Describe retreating blade stall
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.
How do winds affect LTE
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.
Describe the aerodynamics of tail winds in transition to forward flight
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.
How to do a steep approach
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.
How to recover from Vortex Ring State
- Decrease collective pitch.
- Increase forward airspeed.
- 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.
Describe how hover/air-taxi affects LTE
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.
Describe ground effect
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.
What shall the PAC do for all takeoffs?
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.
How to prevent rotor head damage and extend dynamic component life during a running landing
Excessive aft cyclic should be avoided after touchdown. To avoid this during a running landing:
- Control airspeed prior to the main wheels touching down. Avoid aerodynamic braking with cyclic.
- Be aware of the tip path plane; excessive aft cyclic will place the tip path unusually high in the field of view.
- Consciously reposition the cyclic forward prior to lowering collective.
Describe aerodynamics of high AOB turns
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.
How to execute a climb
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.
How to recover from LTE
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.
Describe the aerodynamics of hover/slow speed flight
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.”
Wha is the warning and caution associated with landings?
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.
Describe the aerodynamics of forward flight
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.
Describe weather vaning
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.
Describe the tractor tail rotor
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.