The term unit terminal is used wherever an airport passenger terminal system comprises more than one terminal. Unit terminals may be made up of a number of terminals of similar design (e.g., DallasāFort Worth and Kansas City in the United States), terminals of different design (e.g., Londonās Heathrow, Pearson International Airport near Toronto, John F. Kennedy International Airport in New York City), terminals fulfilling different functions (e.g., Heathrow, Arlanda Airport near Stockholm, Barajas Airport near Madrid), or terminals serving different airlines (e.g., Parisās Charles de Gaulle, John F. Kennedy, DallasāFort Worth). The successful operation of unit terminal airports has often required the design of rapid and efficient automatic people movers such as those at Changi Airport in Singapore, at DallasāFort Worth, and at Houston Intercontinental Airport in Texas.
The apron area
One of the important requirements in the design of a terminal complex is minimizing the time needed to service an aircraft when it is transiting an airport. This is especially important in the handling of short-haul aircraft, where unproductive ground time can consume an unacceptably large percentage of flight time. The turnaround time for a large passenger transport between short-haul flights can be as little as 25 minutes. During this period, a large number of service vehicles circulate on the apron. Therefore, an important aspect in the efficient operation of an airport facility is the marshaling of ground service vehicles and aircraft in the terminal apron area. Such an operation can become extremely complex at some of the worldās busiest airports, where an aircraft enters or leaves the terminal apron approximately every 20 seconds.
Immediately after World War II, new airports were designed with their terminals entirely surrounded by runways, with access to the terminal areas provided by tunnels. Such layouts include John F. Kennedy at New York and Londonās Heathrow. Because many large airports now discourage general aviation use by small aircraft, making crosswind runways unnecessary, the newest designs (including airports at DallasāFort Worth, Munich, and InchāÅn, S.Kor.) have linear layouts of terminals set between parallel runways.
The design process
The design of airport passenger terminals is a complex procedure normally undertaken only by experts in that area. Buildings are planned to accommodate comfortably the passenger flows that are forecast to occur at some future date. In addition, it is anticipated that terminals will have to operate at levels slightly over capacity for short periods. The measurements used are various, including such terms as standard busy rate and typical peak-hour passenger flow, but, by using these design procedures, it is possible to plan a facility that will have insufficient capacity for no more than 30 operating hours per year. Under such conditions, only about 5 percent of passengers would be subjected to inconveniences caused by lack of capacity.