1. Practical hourly capacity (PHCAP), declared capacity, and sustained capacity are measures designed to estimate the number of hourly movements at which operations can be performed over an extended period at acceptable levels of delay.
Practical hourly capacity (PHCAP)
2. The practical hourly capacity (PHCAP) is the oldest of these measures, having originally been proposed by the FAA in the early 1960s. It is defined as the expected number of movements that can be performed in 1 hour on a runway system with an average delay per movement of 4 minutes.
3. The sustained capacity of a runway system, "Reasonably sustained" refers primarily to the workload of the ATM system and of air traffic controllers, is set to approximately 90 percent of maximum throughput capacity when runway configurations with high maximum throughput capacity are in use.
4. Declared capacity is another measure based on the same general notion as sustained capacity. It is defined, again somewhat ambiguously, as the number of aircraft movements per hour that an airport can accommodate at a reasonable LOS. Delay is used as the principal indicator of LOS.
5. Declared capacity is one that has been widely adopted to provides the basis for the worldwide practice of "schedule coordination" and "slot allocation".
6. In conclusion, PHCAP, sustained capacity, and declared capacity are somewhat subjective measures of capacity that can, however, be very useful if applied properly. They are also "derivative" measures, in the sense that one needs to compute the maximum throughput capacity before one can estimate these other capacity measures.
7. Factors Affecting the Capacity of a Runway System. The dependence of the capacity of any runway system on many different factors is emphasized in the previous section. This section provides an overview of the following important factors and of the ways in which each affects runway capacity: