The geometric and maneuvering characteristics of aero planes make it impossible in most cases to locate all the stands required for peak traffic directly adjacent to the central processing part of the terminal building. Several basic concepts that have developed over time may be identified. depending on the total size of the airport. Each concept has its advantages and disadvantages. Apron design must be consistent with the adjacent terminal. Apron and terminal design is an repetition process where the optimum combination of apron and terminal concepts are analyzed at the same time.1- Simple Concept:
This concept is used at very small airports with a few movements of commercial aircraft a day. Stands are always the ‘self-maneuvering’ type. Aircraft parking positions (angled nose–in or nose-out) usually depend on the terminal frontage and the slope of the apron to minimize engine jet blast or prop wash on the terminal building.
2- Linear Concept :
At many airports the simple concept develops gradually to the linear concept. Individual stands are located along the terminal building. A modification of that concept may be found in large airports where the stands are placed along several parallel passenger loading piers (or satellites) that are connected with one another and also with the central terminal by a transport system. An advantage of the linear apron concept is the simple access from the terminal building to the aero planes. a simple installation of the passenger loading bridges and sufficient space for technical handling equipment and staff at the level of the apron. A disadvantage in larger airports may be the large distance between the extreme stands and the central processing point in the terminal building and sometimes larger distance to another stand for transfers between airlines. The latter problem may be solved by people movers. There is now pressure on airports to rearrange the stand allocations to ensure short transfer distances between flights within an airline grouping. Generally the linear concept provides flexible solution where the apron could be easily expanded without disrupting the flow of traffic. 3- Open Concept : In this concept. the stands are located on one or more rows in front of the building. One of the rows may be close-in but most will be a long way from the terminal. The transport of passengers to the distant stands is provided by buses or mobile lounges. for example Milan Lineate where almost all the aircraft stands are on open aprons. The concept allows many aircraft to be served from a very short terminal frontage. Apron location can be optimized with respect to aircraft operations close to the runway to minimize taxi distances and fuel burned. Servicing is usually done from islands set out in the middle of the aprons. A main disadvantage is the need to provide transport to distant stands for all passengers requiring a large workforce and fleet of buses. The length and lack of reliability of bus trips makes the concept unsuitable for operations . Another disadvantage is the large number of additional movements on the apron increasing the possibility of accidents with aircraft and other ground vehicles. 4- Pier Concept : In many large airports, the definition of piers was the most convenient way of providing a greater number of contact stands and to increase the capacity of the airport while providing weather protection for the passengers . The shape of the passenger loading piers varies and depends on the space available at the airport. Piers have the advantage of keeping all the gates under one roof allowing direct contact with the central processing area and a relatively simple navigating task for transferring passengers. particularly if the piers are double-sided. For this apron concept, only nose-in stand types are used. Aircraft can be parked at the stand either angled to reduce stand depth or perpendicular to the pier. The limited space leaves little extra room for aircraft handling. There is only a small parking bay for equipment and service personnel under the piers. In the confined space. Future larger aircraft operation must be considered during planning process to avoid costly reconstructions. The concept is probably able to cope up to 45 mppa. but distances become very long 5- Satellite Concept : In this concept. each of the remote passenger loading satellites is connected with the terminal building by underground tunnels or by overhead corridors. The satellites may be any shape from linear to circular. The number of stands at circular satellites varies between 4 to 8 aero planes but the linear ones may well have 20 stands per side. The larger ones are usually sited in mid-field. their length being limited by the separation between the runways. Satellites as opposed to unit terminals. There is a degree of decentralized processing, particularly with security screening. Given a suitable gate assignment system. This concept is good for hobbling except for international(domestic )transfers that require clearing through the central terminal. There is ample space for aircraft servicing around a circular satellite. Also push-back operations are simple and safe. However, it requires a larger total apron space. Since the distance from the terminal building to the aero plane is considerably extended, it is necessary to transport passengers between the terminal building and the satellites usually with a high frequency automated people-mover. Connections are often below the surface to allow the whole perimeter to be used for parking, but sometimes the connection is over ground allowing some contact stands to be located along the connectors Depending on the size and the shape of the satellite. Aircraft can be parked radically or parallel to the sides of the satellite 6- Hybrid Concept : At many airports combination of two or more mentioned concepts is usual. During the summer peak season. it is quite common to park some, especially charter aircraft on the remote apron and transport passengers by busses or transporters to the aircraft stands.
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