Thursday, August 14, 2008

Straight Climbs (Constant Airspeed and Constant Rate)

For any power setting and load condition, there is only one airspeed which will give the most efficient rate of climb. To determine this, you should consult the climb data for the type of helicopter being flown. The technique varies according to the airspeed on entry and whether you want to make a constant-airspeed or constant-rate climb.

To enter a constant-airspeed climb from cruise airspeed, when the climb speed is lower than cruise speed, simultaneously increase power to the climb power setting and adjust pitch attitude to the approximate climb attitude. The increase in power causes the helicopter to start climbing and only very slight back cyclic pressure is needed to complete the change from level to climb attitude. The attitude indicator should be used to accomplish the pitch change. If the transition from level flight to a climb is smooth, the vertical speed indicator shows an immediate upward trend and then stops at a rate appropriate to the stabilized airspeed and attitude. Primary and supporting instruments for climb entry are illustrated in figure 6-8.

When the helicopter stabilizes on a constant airspeed and attitude, the airspeed indicator becomes primary for pitch. The torque meter continues to be primary for power and should be monitored closely to determine if the proper climb power setting is being maintained. Primary and supporting instruments for a stabilized constant-airspeed climb are shown in figure 6-9.

The technique and procedures for entering a constant-rate climb are very similar to those previously described for a constant-airspeed climb. For training purposes, a constant-rate climb is entered from climb airspeed. The rate used is the one that is appropriate for the particular helicopter being flown. Normally, in helicopters with low climb rates, 500 fpm is appropriate, in helicopters capable of high climb rates, use a rate of 1,000 fpm.

To enter a constant-rate climb, increase power to the approximate setting for the desired rate. As power is applied, the airspeed indicator is primary for pitch until the vertical speed approaches the desired rate. At this time, the vertical speed indicator becomes primary for pitch. Change pitch attitude by reference to the attitude indicator to maintain the desired vertical speed. When the vertical speed indicator becomes primary for pitch, the airspeed indicator becomes primary for power. Primary and supporting instruments for a stabilized constant-rate climb are illustrated in figure 6-10. Adjust power to maintain desired airspeed. Pitch attitude and power corrections should be closely coordinated. To illustrate this, if the vertical speed is correct but the airspeed is low, add power. As power is increased, it may be necessary to lower the pitch attitude slightly to avoid increasing the vertical rate. Adjust the pitch attitude smoothly to avoid overcontrolling. Small power corrections usually will be sufficient to bring the airspeed back to the desired indication.

Technique: The manner or style in which the procedures are executed.

The level-off from a constant-airspeed climb must be started before reaching the desired altitude. Although the amount of lead varies with the helicopter being flown and your piloting technique, the most important factor is vertical speed. As a rule of thumb, use 10 percent of the vertical velocity as your lead point. For example, if the rate of climb is 500 fpm, initiate the level-off approximately 50 feet before the desired altitude. When the proper lead altitude is reached, the altimeter becomes primary for pitch. Adjust the pitch attitude to the level flight attitude for that airspeed. Cross-check the altimeter and vertical speed indicator to determine when level flight has been attained at the desired altitude. To level off at cruise airspeed, if this speed is higher than climb airspeed, leave the power at the climb power setting until the airspeed approaches cruise airspeed, then reduce it to the cruise power setting.

The level-off from a constant-rate climb is accomplished in the same manner as the level-off from a constant-airspeed climb.

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