Making a risk assessment is important, but in order to make any assessment the pilot must be able to see and sense surroundings and process what is seen before performing a corrective action. An excellent process to use in this scenario is called the 3 Ps: Perceive, Process, and Perform.
The Perceive, Process, Perform (3P) model for ADM offers a simple, practical, and systematic approach that can be used during all phases of flight. [Figure 5-3] To use it, the pilot will:
- Perceive the given set of circumstances for a flight.
- Process by evaluating their impact on flight safety.
- Perform by implementing the best course of action.
Examine a pilot flying into a canyon. Many pilots fail to see the difference between a valley and a canyon. Most valleys can be characterized as depressions with a predominant direction. A canyon is also a valley, but it is a very deep valley bordered by cliffs. One can infer that making a turn across a valley will be over rising terrain whose slope is shallow. A canyon, however, is bordered by vertical walls. Additionally, valleys are typically wider than canyons. However, before proceeding it is important to understand the relationship between rate of turn and turn radius.
Rate of Turn
The rate of turn (ROT) is the number of degrees (expressed in degrees per second) of heading change that an aircraft makes. The ROT can be determined by taking the constant of 1,091, multiplying it by the tangent of any bank angle and dividing that product by a given airspeed in knots as illustrated in Figure 5-4. If the airspeed is increased and the ROT desired is to be constant, the angle of bank must be increased; otherwise, the ROT decreases. Likewise, if the airspeed is held constant, an aircraft’s ROT increases if the bank angle is increased. The formula in Figures 5-4 through 5-6 depicts the relationship between bank angle and airspeed as they affect the ROT.
NOTE: All airspeeds discussed in this section are true airspeed (TAS).
Airspeed significantly affects an aircraft’s ROT. If airspeed is increased, the ROT is reduced if using the same angle of bank used at the lower speed. Therefore, if airspeed is increased as illustrated in Figure 5-5, it can be inferred that the angle of bank must be increased in order to achieve the same ROT achieved in Figure 5-6.
What does this mean on a practicable side? If a given airspeed and bank angle produces a specific ROT, additional conclusions can be made. Knowing the ROT is a given number of degrees of change per second, the number of seconds it takes to travel 360° (a circle) can be determined by simple division. For example, if moving at 120 knots with a 30° bank angle, the ROT is 5.25° per second and it takes 68.6 seconds (360° divided by 5.25 = 68.6 seconds) to make a complete circle. Likewise, if flying at 240 knots TAS and using a 30° angle of bank, the ROT is only about 2.63° per second and it takes about 137 seconds to complete a 360° circle. Looking at the formula, any increase in airspeed is directly proportional to the time the aircraft takes to travel an arc.
So, why is this important to understand? Once the ROT is understood, a pilot can determine the distance required to make that particular turn, which is explained in radius of turn.
Radius of Turn
The radius of turn is directly linked to the ROT, which is a function of both bank angle and airspeed, as explained earlier. If the bank angle is held constant and the airspeed is increased, the radius of the turn changes (increases). A higher airspeed causes the aircraft to travel through a longer arc due to a greater speed. An aircraft traveling at 120 knots is able to turn a 360° circle in a tighter radius than an aircraft traveling at 240 knots. In order to compensate for the increase in airspeed, the bank angle would need to be increased.
The radius of turn (ROT) can be computed using a simple formula. The radius of turn is equal to the velocity squared (V2) divided by 11.26 times the tangent of the bank angle.
Using the examples provided in Figures 5-4 through 5-6, both the radii of the two speeds postulated can be computed. Noteworthy, is if the speed is doubled, the radius is squared. [Figures 5-7 and 5-8]
In Figure 5-9, two aircraft enter a canyon. One aircraft enters at 120 knots, and the other at 140 knots. Both pilots realize they are in a blind canyon and need to conduct a course reversal. Both pilots perceive their unique environment and sense that something is occurring. From this perception, the pilots process the information, and then act. Although one may sense that this is similar to the DECIDE model, it is not. The 3P process is a continuous loop of the pilot’s handling of hazards. The DECIDE model and naturalistic decision-making focus on particular problems requiring resolution. Therefore, pilots exercise the 3P process continuously, while the DECIDE model and naturalistic decision-making result from the 3P process.
In the first step, the goal is to develop situational awareness by perceiving hazards, which are present events, objects, or circumstances that could contribute to an undesired future event. Both pilots realize they need to turn 180° for continued safe flight. The pilot systematically identifies and lists hazards associated with all aspects of the situation, and must do it fast and accurately.
In the second step, the goal is to process learned and practiced information to determine whether the identified hazards constitute risk, which is defined as the future impact of a hazard that is not controlled or eliminated. The degree of risk posed by a given hazard can be measured in terms of exposure or potential mishap and death.
The pilot flying at 120 knots is familiar with the formulas discussed before or is aware that slower speeds result in a smaller turning radius. The pilot flying at 140 knots does not slow down as he thinks that a 30° bank is satisfactory.
In both cases, the pilots perform the turns. The pilot performing a turn at 120 knots exits the canyon safely; while the pilot flying at 140 knots hits the canyon wall, killing all onboard. Another area, although not a canyon, is flying around buildings. Just a few years ago, a pilot collided with a building during a turn. Had he slowed down, he would be alive today.
The 3P model is intended to be a constant loop within which the pilot measures his or her actions through perception of the current, dynamically changing situation. Failure to do so results in error, an accident, and possible death. The pilot flying at 140 knots failed in this endeavor and paid the ultimate price. Therefore, the 3P process must be a continuous loop providing anomalies or reassurance that what is going on is what was predicted or unexpected.