When an aircraft enters a climb, it changes its flightpath from level flight to an inclined plane or climb attitude. As discussed in chapter 2, weight in a climb no longer acts in a direction perpendicular to the flightpath. It acts in a rearward direction. This causes an increase in total drag requiring an increase in thrust (power) to balance the forces. An aircraft can only sustain a climb angle when there is sufficient thrust to offset increased drag; therefore, climb is limited by the thrust available. [Figure 6-13]
Like other maneuvers, climbs should be performed using outside visual references and flight instruments. It is important that the pilot know the engine power settings and pitch attitudes that produce the following conditions of climb:
- Normal climb—performed at an airspeed recommended by the aircraft manufacturer. Normal climb speed is generally the WSC best rate of climb (VY) speed as discussed below. Faster airspeeds should be used for climbing in turbulent air.
- Best rate of climb (VY)—the airspeed at which an aircraft will gain the greatest amount of altitude in a given unit of time (maximum rate of climb in feet per minute (fpm)). The VY made at full allowable power is a maximum climb. This is the most efficient speed because it has the best lift over drag ratio for the aircraft. This speed is also the best glide ratio speed used for going the greatest distance for the amount of altitude, as discussed later in this chapter. Each aircraft manufacturer is different but a good rule of thumb is that the VY is 1.3 times the stall speed. It must be fully understood that attempts to obtain more climb performance than the aircraft is capable of by increasing pitch attitude results in a decrease in the rate of altitude gain. Trim is usually set at the VY or higher.
- Best angle of climb (VX)—performed at an airspeed that will produce the most altitude gain in a given horizontal distance. Best VX airspeed is lower than VY but higher than minimum controlled airspeed. The VX results in a steeper climb path, although the aircraft takes longer to reach the same altitude than it would at VY. The VX, therefore, is used in clearing obstacles after takeoff. Since the VX is closer to the stall speed, caution should be exercised using this speed to climb so as not to stall the WSC aircraft close to the ground with potentially catastrophic consequences. [Figure 6-14]
Climbing flight requires more power than flying level, as described in chapter 2. When performing a climb, the normal climb speed should be established and the power should be advanced to the climb power recommended by the manufacturer. As the aircraft gains altitude during a climb, the engine has a loss in power because the same volume of air entering the engine’s induction system gradually decreases in density as altitude increases.
During a climb, a constant heading should be held with the wings level if a straight climb is being performed, or a constant angle of bank and rate of turn if a climbing turn is being performed. To return to straight-and-level flight, when approaching the target altitude, increase the speed to the cruise setting (if different) and decrease throttle for level flight. After the aircraft is established in level flight at a constant altitude and the desired speed, the aircraft should be trimmed (if equipped with an in flight trim system).
In the performance of climbing turns, the following factors should be considered.
- With a constant power setting, the same pitch attitude and airspeed cannot be maintained in a bank as in a straight climb due to the increase in the total lift required.
- The degree of bank should not be too steep. A steep bank significantly decreases the rate of climb. The bank should always remain constant.
- At a constant power setting and turning while climbing, the WSC aircraft climbs at a slightly shallower climb angle because some of the lift is being used to turn.
- Attention should be looking at outside references and scanning for traffic with no more than 25 percent of the time looking at inside flight deck instruments.
There are two ways to establish a climbing turn. Either establish a straight climb and then turn, or enter the climb and turn simultaneously. Climbing turns should be used when climbing to the local practice area. Climbing turns allow better visual scanning, and it is easier for other pilots to see a turning aircraft.
In any turn, the loss of vertical lift and increased induced drag due to increased angle of attack becomes greater as the angle of bank is increased. So, shallow turns should be used to maintain an efficient rate of climb. All the factors that affect the aircraft during level (constant altitude) turns affect it during climbing turns or any other maneuver.
Common errors in the performance of climbs and climbing turns are:
- A bank angle too high to achieve an efficient climb.
- A speed too high to achieve an efficient climb rate.
- A speed that is too low.
- Attempting to exceed the aircraft’s climb capability.
- Inability to keep pitch and bank attitude constant during climbing turns.
- Attempting to establish climb pitch attitude by referencing the airspeed indicator, resulting in “chasing” the airspeed.