Exercise 18 - Autorotations 3

GROUND SCHOOL

Flight Manual - Limitations

PREPARATORY INSTRUCTION

Aim

For the student to learn how to vary range in autorotation.

Review

    1. Autorotations 1 and 2 - Exercises 7 and 13.
    2. Autorotational flight envelope, including airspeed and rotor RPM limitations.
    3. Effects of airspeed on range and rate of descent in autorotation.

Motivation

Autorotation at the manufacturer's recommended airspeed is the ideal because it results in the minimum possible rate of descent. The resulting range however, will not necessarily result in landing at the desired spot under actual emergency conditions. It is vital therefore that the student be capable of taking full advantage of the helicopter's capabilities in autorotation to achieve the intended landing spot.

Airmanship

    1. Safety checks.
    2. Safe landing area.
    3. Lookout.
    4. Wind Velocity.

Teaching Points

    1. State the airspeed and RRPM for maximum range and VNE in autorotation, point out the increase in rate of descent, as appropriate to type.
    2. Extending the range
      1. Point out that there is no benefit from exceeding the manufacturer's recommended maximum range speed and that exceeding autorotational VNE will result in drastic rotor RPM decay.
      2. Describe the difference in visual cues between an autorotation at minimum rate-of-descent speed and maximum range speed.
      3. Describe the procedure for entering and maintaining maximum range autorotation, as appropriate to type.
      4. Point out that it is advantageous to reduce the airspeed to minimum rate-of-descent speed as early as possible in order to reduce the rate of descent to more desirable proportions.
      5. Describe the technique for carrying out a touchdown from a maximum range approach, as appropriate to type.
    3. Reducing the range
      1. Explain that there are two methods of reducing range in autorotation - reducing airspeed and turning.
      2. Describe the procedure for entering and maintaining an autorotation at low airspeed.
      3. Point out the need to avoid a zero airspeed autorotation due to excessive rate-of-descent and controllability problems. Explain that it is preferable to maintain at least some indicated airspeed (10-20 kts) and accept the resulting ground speed. Do not achieve a negative airspeed.
      4. Stress the need to increase airspeed to the minimum rate-of-descent speed as soon as possible, in order to reduce the rate of descent to manageable proportions. Minimum rate of descent speed should be acquired before entering the shaded area of the height velocity chart (most types approximately 150-200 feet).
    4. Turns
      1. Describe how to shorten the range in autorotation by means of turning.
      2. State the average altitude lost in a 180° and 360° autorotation.
    5. Explain that an autorotation following an actual emergency will often involve several changes of airspeed and direction in order to arrive at the selected landing point. Point out that this requires both skill and judgement, which will only come from frequent practice.

Confirmation

PRE-FLIGHT BRIEFING

AIR LESSON
    1. Review autorotations at minimum rate of descent speed as follows:
      1. over a selected point at 1,500 feet above ground, enter autorotation and descend at the manufacturer's recommended speed for minimum rate of descent. Point out the visual cues of rate of descent and range; and
      2. land.
    2. Student practice.
    3. Over the same selected point at the same height:
      1. autorotate at the manufacturer's recommended airspeed for maximum range in autorotation. Point out the increased rate of descent and range; and
      2. land.
    4. Over the same selected point at the same height:
      1. autorotate at the manufacturer's recommended airspeed for maximum range in autorotation and recommended minimum rotor RPM. Point out the rate of descent and range; and
      2. land.
    5. Over the same selected point at the same height, autorotate at a low airspeed (10-20 kts). Point out:
      1. the high rate of descent;
      2. the height lost in recovering from low forward speed to minimum descent speed; and
      3. the distance covered.
    6. Student practice.
    7. Select a spot on the ground and demonstrate autorotative approaches from various height, speeds and directions.
    8. Student practice.

POST-FLIGHT DEBRIEFING

TIPS FOR INSTRUCTORS
    1. On the initial demonstration of each type of range variation use the same line feature, such as a fence or road, as a reference point to enter. Always enter using the same height, speed or power setting. This ensures the student appreciates the difference in distance for each type.
    2. After teaching the individual methods of range variation, be sure that students understand that these are the basics, and that they usually have to use combinations to achieve the landing spot. When students have grasped the basics, introduce situations that require them to assess and use a combination of different techniques.
    3. Emphasize that when varying the range, the helicopter should be returned to the normal autorotational touchdown profile by 150-200 feet. A rule of thumb for a zero speed auto is 100 feet loss in altitude for 10 knots gain in airspeed.
    4. Point out that in some instances #3 is not always possible and it may be necessary to accept a slight crosswind, or a little less airspeed, than to be turning in the flare immediately prior to touchdown when very close to the ground.
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