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Helicopter Lesson - Maneuvers

Helicopter Lesson Guides:  Intro | Aerodynamics | Powered Flight | Load FactorControl Functions | Systems | RFM | Weight & Balance | Performance | Hazards | Precautions | Maneuvers | Glossary
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Chapter 11. HELICOPTER FLIGHT MANEUVERS (continued)

Click to open or print...NORMAL APPROACH TO A HOVER

A normal approach to a hover is basically a power glide made at an angle of descent of approximately 10° (click to open figure 72 to the right). This type of approach is used in the majority of cases.

TECHNIQUE:
  1. 1. The entry to the downwind leg should be made at a 45° angle to the downwind leg so that the actual turn to the downwind leg will be accomplished opposite the middle one-third of the runway. The transition from downwind leg to the final approach leg may be made by two 90° turns in which a definite base leg is established, or by a 180° turn. At all times during this transition, sufficient altitude should be available so that in case of engine failure, an autorotative landing can be completed into the wind. The point in the traffic pattern at which the power reduction is made should be determined by this fact.
  2. Initiate the approach by lowering the collective pitch control the amount required to descend at an angle of approximately 10° on the final approach leg. As collective pitch is lowered, increase right pedal as necessary to compensate for the change in torque reaction to maintain heading, and adjust throttle to maintain proper RPM. Decelerate to the approximate airspeed, then further adjust attitude as necessary to maintain approach airspeed.
  3. The angle of descent is primarily controlled by collective pitch, the airspeed is primarily controlled by the cyclic control, and heading on final approach is maintained with pedal control. However, only by the coordination of all controls can the approach be accomplished successfully.
  4. The approach airspeed should be maintained until the point on the approach is reached where, through evaluation of apparent groundspeed, it is determined that forward airspeed must be progressively decreased in order to arrive at hovering altitude and attitude at the intended landing spot with zero groundspeed.
  5. As forward airspeed is gradually reduced by the application of rearward cyclic, additional power (collective pitch) must be applied to compensate for the decrease in translational lift and to maintain the proper angle of descent. As collective pitch is increased, left pedal must be increased to maintain heading, throttle adjusted to maintain RPM, and cyclic pitch coordinated to maintain the proper rate of closure to the desired spot (a continual decrease in groundspeed).
  6. The approach is terminated at hovering altitude above the intended landing point with zero groundspeed. If power has been properly applied during the final portion of the approach, very little additional power should be required during the termination.
  7. If the condition of the landing spot is unknown, the approach may be terminated just short of the spot so that it can be checked before moving forward for the landing.
COMMON ERRORS:
  1. Failing to maintain proper RPM during the entire approach.
  2. Improper use of the collective pitch in controlling the angle of descent.
  3. Failing to make pedal corrections to compensate for collective pitch changes during the approach.
  4. Failing to arrive at hovering altitude, hovering attitude, and zero groundspeed almost simultaneously.
  5. Low RPM in transition to the hover at the end of the approach.
  6. Using too much aft cyclic stick close to the surface, which may result in tail rotor strikes.
Click to open or print...Crosswind considerations in approaches

During the early stages of a crosswind approach, a crab and/or a slip may be used (fig. 71). During the final stages of an approach, beginning at approximately 50 feet of altitude, a slip should be used to align the fuselage with the ground track. The rotor is tilted into the wind (with cyclic pressure) enough so that the sideward movement of the helicopter and wind drift counteract each other. Heading is maintained along the ground track with the antitorque pedals. (See "Crosswind Considerations During Takeoffs.") This technique should be used on any type of crosswind approach - shallow, normal, or steep.

NORMAL APPROACH TO THE SURFACE

When it is known or suspected that loose snow or dust exists on your landing spot, an approach to the surface may be used. It may also be used when the surface is unfavorable for a running landing, and high density altitude or heavily loaded conditions exist.

TECHNIQUE:

The approach is the same as the normal approach to a hover. However, the approach should be continued to touchdown, terminating in a skids-level attitude with no forward movement.

COMMON ERRORS:
  1. Terminating at a hover, then making a vertical landing.
  2. Touching down with forward movement.
  3. Approaching too slow, requiring the use of excessive power during the termination.
  4. Approaching too fast, causing a hard landing.

Click to open or print...STEEP APPROACH TO A HOVER

A steep approach is used primarily when there are obstacles in the approach path that are too high to allow a normal approach. A steep approach will permit entry into most confined areas and is sometimes used to avoid areas of turbulence around a pinnacle. An approach angle of approximately 15° is normally used for steep approaches (see figure 73 to the right).

TECHNIQUE:
  1. Entry is made in the same way as for a normal approach, except that a greater reduction of collective pitch is usually required at the beginning of the approach to start the descent than for a normal approach. As collective pitch is lowered, increase right pedal to maintain heading and adjust throttle to maintain RPM.
  2. As in a normal approach, the angle of descent is primarily controlled by collective pitch, and the speed is primarily controlled by the cyclic control. However, only by the coordination of all controls can the approach be accomplished successfully.
  3. The approach airspeed should be maintained until the point on the approach is reached where, through evaluation of apparent groundspeed, it is determined that forward airspeed must be progressively decreased in order to arrive at hovering altitude at the intended landing spot with zero groundspeed. This is very important since a flare should not be made near the surface due to the danger of tail rotor strikes.
  4. As forward airspeed is gradually reduced by the application of rearward cyclic pressure, additional power (collective pitch) must be applied to compensate for the decrease in translational lift and to maintain the proper angle of descent. As collective pitch is increased, left pedal must be increased to maintain heading, throttle adjusted to maintain RPM, and cyclic pitch coordinated to maintain the proper change in forward airspeed.
  5. Since the angle of descent on a steep approach is much steeper than for a normal approach, the collective pitch must be used much sooner at the bottom of the approach. The approach is terminated at hovering altitude above the intended landing point with zero groundspeed. If power has been properly applied during the final portion of the approach, very little additional power should be required during the termination.
COMMON ERRORS:
  1. Failing to maintain proper RPM during the entire approach.
  2. Improper use of collective pitch in controlling the angle of descent.
  3. Failing to make pedal corrections to compensate for collective pitch changes during the approach.
  4. Slowing airspeed excessively in order to remain on the proper angle of descent.
  5. Failing to arrive at hovering altitude, hovering attitude, and zero groundspeed almost simultaneously.
  6. Low RPM in transition to the hover at the end of the approach.
  7. Using too much aft cyclic stick close to the surface, which may result in tail rotor strikes.
LANDING FROM A HOVER

In this maneuver, the helicopter is landed vertically from a hover.

TECHNIQUE:
  1. From a hover, begin a descent by applying a slow but very gradual downward pressure on the collective pitch stick. This smooth application of collective pitch should be such that a constant rate of descent is maintained to the surface. As the skids descend within a few inches of the surface, the ground effect becomes very noticeable and the helicopter tends to stop its descent. At this point, it may be necessary to further decrease the collective pitch stick a slight amount to maintain the constant rate of descent.
  2. When the skids touch the surface, lower the collective pitch smoothly and firmly to the full down position, adjust the throttle to keep RPM in the proper range, and at the same time add right pedal as needed to maintain heading.
  3. Throughout the descent and until the time the skids are firmly on the surface and the collective pitch is in full down position, make necessary corrections with pedals to maintain a constant heading, and necessary corrections with the cyclic control to maintain a level attitude (for existing load and wind conditions) and prevent movement over the surface.
COMMON ERRORS:
  1. Overcontrolling the cyclic control during descent resulting in movement over the surface on contact.
  2. Failing to use collective pitch smoothly.
  3. Pulling back on the cyclic stick prior to or upon touchdown.
  4. Failing to reduce the collective pitch smoothly and positively to the full down position upon contact with the surface.
  5. Failing to maintain a constant rate of descent.
  6. Failing to maintain proper RPM.
Click to open or print...SHALLOW APPROACH AND RUNNING LANDING

A shallow approach and running landing (see figure 74 to the right) are used when a high-density altitude or a high gross weight condition or some combination thereof is such that a normal or steep approach cannot be made because of insufficient power to hover. To compensate for this lack of power, a shallow approach and running landing makes use of translational lift until surface contact is made. The glide angle is approximately 5°. Since a running landing follows a shallow approach, a surface area of sufficient length and smoothness must be available.

TECHNIQUE:
  1. A shallow approach is initiated in the same manner as the normal approach except that a shallower angle of descent is maintained. The power reduction to initiate the desired angle of descent will be less than that for a normal approach since the angle of descent is less. As collective pitch is lowered, maintain heading by increasing right pedal pressure, adjust throttle to maintain RPM, and use cyclic as necessary to maintain the desired approach airspeed.
  2. As in normal and steep approaches, the angle of descent and rate of descent are primarily controlled by collective pitch, and the groundspeed is primarily controlled by the cyclic control. The coordination of all controls is needed, however, if the approach is to be accomplished successfully.
  3. Approach airspeed should be maintained until an altitude of approximately 50 feet above the surface has been reached. At this point, gradually apply aft cyclic stick to start dissipating airspeed and coordinate a slight downward pressure on the collective pitch to maintain the angle of descent. The deceleration of the airspeed should be enough so that the helicopter will tend to descend to the surface due to the decreased effect of translational lift just as the landing spot is reached. Since translational lift diminishes rapidly at slow airspeeds, the deceleration must be smoothly coordinated, at the same time keeping enough lift to prevent the helicopter from settling abruptly.
  4. On the final part of the approach, prior to making surface contact, the helicopter should be placed in a level attitude with cyclic control, pedals should be used to maintain heading, and cyclic stick should be used as necessary so that heading and ground track are identical. Allow the helicopter to descend gently to the surface in a straight-and-level attitude, cushioning the landing by proper manipulation of the collective pitch.
  5. After surface contact, the cyclic control should be placed slightly forward of neutral to tilt the main rotor away from the tail boom; antitorque pedals should be used to maintain heading; throttle should be used to maintain RPM; and cyclic stick should be used to maintain surface track. Normally, the collective pitch is held stationary after touchdown until the helicopter comes to a complete stop. However, if braking action is desired or required, the collective pitch may be lowered cautiously. To ensure directional control, normal rotor RPM must be maintained until the helicopter stops.
COMMON ERRORS:
  1. Assuming excessive nose-high attitude at approximately 10 feet of altitude.
  2. Insufficient collective pitch and throttle to cushion landing.
  3. Failing to add left pedal as collective pitch is added to cushion landing, resulting in a touchdown while in a left skid.
  4. Touching down at an excessive groundspeed for the existing conditions (20 MPH groundspeed in most cases would be considered maximum allowable).
  5. Failing to touch down in a level attitude.
  6. Failing to maintain proper RPM during and after touchdown.
  7. Poor directional control upon touchdown.
Click to open or print...RUNNING TAKEOFF

A running takeoff (see figure 75 to the right) is used when conditions of load and/or density altitude prevent a sustained hover at normal hovering altitude. It is often referred to as a high-altitude takeoff. With insufficient power to hover, at least momentarily or at a very low altitude, a running takeoff is not advisable. No takeoff should be attempted if the helicopter cannot be lifted off the surface momentarily at full power because:

1 - If the helicopter cannot be hovered, its performance is unpredictable.

2 - If the helicopter cannot be raised off the surface at all, sufficient power might not be available for a safe running takeoff. A running takeoff may be accomplished safely only if surface area of sufficient length and smoothness is available, and if no barriers exist in the flightpath to interfere with a shallow climb.

TECHNIQUE:
  1. Head the helicopter into the wind.
  2. Increase the throttle to obtain takeoff RPM.
  3. Hold the cyclic stick slightly forward of the hovering neutral position. Apply collective pitch slowly to accelerate into forward movement. (During practice, a manifold pressure of 1 to 2 inches below that which is required to hover may be used.)
  4. Maintain a straight ground track with lateral cyclic control and heading with antitorque pedals until a climb is established.
  5. As effective translational lift is gained, slight back pressure on the cyclic stick will take the helicopter into airborne flight smoothly, in a level attitude, with little or no pitching.
  6. Maintain an altitude not to exceed 10 feet to allow airspeed to increase toward normal climb speed and follow a climb profile that will take you through the clear area of the height-velocity curve for the particular helicopter.
  7. During practice maneuvers, climb to 50 feet then adjust power to normal climb power, and attitude to normal climb attitude.
COMMON ERRORS:
  1. Failing to align heading and ground track to keep surface friction to a minimum.
  2. Attempting to pull the helicopter off the surface before effective translational lift is obtained.
  3. Lowering the nose too much after becoming airborne resulting in the helicopter settling back to the surface.
  4. Failing to remain below approximately 10 feet of altitude until airspeed approaches normal climb speed.
Click to open or print...MAXIMUM PERFORMANCE TAKEOFF

A maximum performance takeoff is used to climb at a steep angle to clear barriers in the flightpath (see figure 76 to the right). It can be used when taking off from small fields surrounded by high obstacles. Before attempting a maximum performance takeoff, you must know thoroughly the capabilities and limitations of your equipment. You must take into consideration the wind velocity, temperature, altitude, density altitude, gross weight, center-of-gravity location, and other factors affecting your technique and the performance of the helicopter. To safely accomplish this type of takeoff, sufficient power to hover must be available to prevent the helicopter from sinking back to the surface after becoming airborne. This maneuver will result in a steep climb, affording maximum altitude gain in a minimum distance forward.

The angle of climb for a maximum performance takeoff will depend on existing conditions. The more critical the conditions - high density altitudes, calm winds, etc. - the shallower the angle of climb should be. Use caution in climbing steeply. If the airspeed is allowed to get too low, the helicopter may settle back to the surface. The height-velocity (H/V) chart for the particular helicopter should be fully considered before making any maximum performance takeoff. An engine failure at low altitude and airspeed would place the helicopter in a dangerous position, requiring a high degree of skill in making a safe autorotative landing. It may be necessary to operate in the shaded area of the H/V diagram during the beginning of this maneuver when operating in light or no-wind conditions. The angle of climb and resulting airspeed will be dictated by the proximity and height of the obstacles to be cleared. The pilot must be aware of the calculated risk involved when operating in the shaded area of the H/V diagram.

TECHNIQUE:
  1. The helicopter should be headed generally into the wind and the cyclic stick placed in what would be the neutral position for hovering under the existing load and wind conditions. (This position could be checked by hovering the helicopter momentarily prior to preparing to make a maximum performance takeoff.)
  2. Establish the proper RPM setting and apply sufficient collective pitch to lighten the helicopter on its landing gear (fig. 76 above). Apply the maximum amount of collective pitch that can be obtained without reducing RPM and simultaneously add full throttle (maximum pitch and full throttle may be impractical or at least unnecessary on some helicopters, particularly on those equipped with supercharged engines) and sufficient forward cyclic stick to establish a forward climbing attitude as the helicopter leaves the surface. Apply necessary antitorque pedal control to maintain heading. RPM must not be sacrificed to obtain increased pitch on the rotor blades. If RPM starts to decrease under a full power condition, it can be regained only by reducing collective pitch.
  3. Utilize full power until the helicopter is clear of all obstacles, after which a normal climb can be established and power reduced.
COMMON ERRORS:
  1. Nose too low initially causing horizontal flight rather than more vertical flight.
  2. Failure to maintain maximum permissible RPM.
  3. Control movements too abrupt.
<< Previous | Next (continued) >>

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