The colour divisions are somewhat arbitrary, but are valid in describing the types of situations encountered during a flight. As the pilot moves from one zone to the next we can see that different things will become important for safe outcomes. Good judgements will generally require not only recognizing the parameters of the specific situation, but the type of situation as well. Pilots should grow accustomed to recognizing that they are in the ‘Green’ and spend time doing planning activities, so that when the ‘Yellow’, and ‘Red’ crop up they can concentrate on monitoring and control. While stress and time constraints are important factors, the concept of appropriate activity is a bit more far reaching.
One outcome of the above classification is that as we transition from one zone to the next we should do one last prime activity of the zone you are leaving and start with the prime activity of the zone you are entering. From Green to Yellow, a last detailed consideration of planning should be followed by a check of monitoring and control. From Yellow to Red, a quick planning check, a last good monitor of the flight condition leads into the details of control.
For example consider entering the circuit for landing. When we enter the circuit we transition from ‘Green’ to ‘Yellow’. We must make a fairly firm decision on landing at the chosen field and consider whether the runway, and circuit we have chosen is appropriate to the conditions, surface, traffic et cetera. This is the last time when we can effectively make plans before the time factor shortens and the corresponding stress levels rise. This is the basis for the phrase that “good circuits make good landings”. Once in the ‘Yellow’, the downwind leg, we complete our landing checks and spend about equal amounts of time with more short term planning (wind drift, traffic etc.), monitoring (straps secure, spoilers working, aircraft trimmed properly, traffic separation etc.), and control. The turn on to base leg is our transition into the ‘Red’. We must confirm that our more immediate planning is on track. This is the last time we will have a good opportunity to choose an alternate runway if things have gone awry. As well, this is the last time to monitor three important aspects of the flight, the traffic, the landing or glide slope, and the approach configuration of the aircraft (speed, gear down etc.). From this point on we are largely committed to executing our landing plans. We monitor our glide slope, airspeed, and the effect of the wind; however, we will spend most of our time controlling the aircraft and existing in a largely reactive mode until the aircraft has come to a full stop. Once we have reached a full stop we move into the ‘Yellow’ and remain there until we have cleared the runway and parked the aircraft properly.
There is no reason why pilots cannot extend the use of these situational zones to other viewpoints. For instance, during a cross-country flight, while in the cruising height band, the pilot would be in the ‘Green’; below 2000 feet AGL in the ‘Yellow’, and at 1000 feet AGL in the ‘Red’ for purposes of field selection. Alternatively, weak lift conditions at the beginning and end of the day may be thought of as ‘Red’, or ‘Yellow’, as opposed to the strong part or ‘Green’ part of the day.
I think that pilots will quite quickly understand that the time and attention requirements are the prime factors in classifying activities in the ‘zones’. It only remains to remember where the skill emphasis must be placed for each zone. As instructors we must give our students the appropriate habits, and coach them on the activities appropriate to each zone.
While situational awareness goes a long way to promoting the appropriate activities during the various flight segments we must also recognize that there is usually more than one path that can be followed in any situation.