Hangar Space - A Physical

Hangar Space - a Physical Plant

Hangar Space

Airport Facilities - Planning Hangar construction

The airports and the concepts regarding airport planning and construction have undergone vast changes. These relate to changes in technology, changes in demand, type of aircraft, passenger requirement, and service requirements and so on. A change in the wing span of an aircraft requires remodeling many things, from runways to hangars and equipments. On account of the competitive nature of the industry and the changing ways of usage, the planning of airports and facilities has undergone vast changes to suit the times. For example design of an airport to day has become more approach oriented that is the accessibility of the passengers to the airport is the critical issue. Developing airports and facilities are complicated maneuvers that require experts from multiple disciplines acting and planning together. In the U.S. The authority that controls the air space was created far back in the 1930s. The federal government took control of the economic aspects of aviation in 1938 the Civil Aeronautics Board -- CAB was created to control the aviation industry and is the authority for aerospace matters. (O'connor, 2001)

From the beginning of the nineteenth century, air travel has grown tremendously. In the 80's it was at about 6% per annum, and in the recent years the demand for air services is growing on account of general increase in income, and globalization. The airline and deregulation of airports have added to the expansion. Privatization has also added to the growth and future expansion of the aviation and the aviation service industry. The number of freight and passenger requirement is growing geometrically and the pressure on existing airports is very heavy. The airports spend about $40 billion in development world wide in developing airport and structures. Airport development is a dynamic growth sector. This also has an impact on employment patterns. (Banister; Berechman, 2000) Therefore considering the overall infrastructure facilities required by the airport, and the type of service envisaged by the airport and the planes that are likely to use the airports play an important role in determining the proper planning of an airport.

Airport Macro level planning

There is an economic problem in planning airports. The paradox that the increase in demand in all other cases brings about profitability does not work in this field. The performance of all the worlds' airlines in spite of expansion has been marginal. The rate of return on assets will not work with analyzing the airline profitability. Therefore a separate method has to be adopted. (Doganis, 2002) There are capital-sums invested in airports that get invested in large immovable assets which have no alternative use. The demand predictions are also out of the control of the planner. The airlines that operate will determine the volume of traffic and the use of the facilities. The airport plays the primary role of bringing together the airlines and their customers. Therefore the objective of providing infrastructure and maintaining customer satisfaction is a Herculean task. There are more issues in the planning, one that investment is huge, and the second that planning the airport construction is an ongoing process that takes anything between five to ten years to become viable. The terminal thus takes a long span of time to get completed and must have a projection of another ten years demand to make it viable to run the service. Thus airport plans need to be oriented and planned for at least fifteen years ahead. Thus it involves expert use of forecasting techniques, which will help achieve profits in future. (Doganis, 1992)

Hangars have to be similarly planned with the possible development of the types of aircraft and needs that could arise in terms of service, space and requirements. One of the key elements that retard the development of airports is the lack of access. The ground access strategy has to be well defined, but the rapid developments are also causing environmental damage. The Port Authority of New York and New Jersey calculates that there is a loss of $20 million each year on account of delays, congestion, and the poor airport service is sited as a reason for the migration of business from the congested airway areas. Parameters can be "total travel time, cost and volumes for moving cargo and passengers, origins and destinations, capacity, accidents, ease of access, perceived quality and the average time to transfer people or freight from one mode to another." ("Airport Ground Access Planning Guide," n. d.) the next consideration ought to be the facilities available to the passenger, including taxis, conveyance, and traffic flow.

Early Hangars and development

We will look at the facilities at airports and then consider the issues of the hangar. Early hangars were barns converted for the purpose. In early days of aviation, the requirements often were minimal and airports were mostly for military use. For example if we consider the Garfield County Airport its hangar is odd. The hangar is barn like and built with local materials that showcase the agrarian influence on its construction. It probably was constructed by persons without any previous experience in such matters. The craftsmanship however is perfect, for the hangar is still serviceable and has withstood the ravages of time. It is now listed in the National Register of Historic Places. The important thing is that it is made of pine wood and the gables are made of timber and logs. These logs themselves were felled to ward off the black beetle. In 1930 this airport showed that remote places with airport facilities could attract business. In 1938 this completed airfield was the venue of the Air Mail Week. (Powell; Murphy, 1995)

Airfield design was pioneered in the U.S. By the air force. The field design methods that were followed by the force which was used for heavy bombers that had unprecedented weight still remain a model for construction especially in pavement design and the U.S. Army Corps of Engineers created the first rigid airfield pavement design. The growth in technology has brought in many new methods like the layered elastic methods, and by itself the study of this aspect of the airport is a great branch to be considered. (Donnally, 2007) in planning the airport itself many important aspects other than hangar space determine the type of facilities required, including the type of hangars. The central area of the airport, which is among the parallel runways, would be the area which would be the most widely developed. If we consider for example the proposal to develop the Painefield airport, and the master plan that was developed for the purpose we come across specifications that would throw light on the general requirements that will incorporate on the "south side of the crosswind runway, new development in the central area will be primarily related to general aviation hangars and industrial aviation facilities. Airport compatible commercial/industrial uses are programmed for the southern portion of the central area which is the former Navy Housing site. On the east side of airport property, only the area directly east of the secondary parallel runway can be feasibly provided with taxiway access; therefore, it is the only site programmed for aviation use." ("Paine Field Airport Master Plan / Update," n. d.)

If we consider the development plan we will also know that museums and tour operations are now part of the airport industry. Further flying clubs and other agencies also use the airport. Thus planning the airport structure has to undertake the creation of many facilities. Only if the facilities are present and if the regulations regarding the mandatory requirements are met can there be a perfect design of the airport. Design of the airport and its facilities and the type of aircrafts that will use the airport is very crucial in determining the type of hangars and the facilities they ought to provide. Needs at the hangar have come a long way from the traditional hangar built of logs back in the 1930s. The regulations and requirements are to be observed for the angle of funding and legal compliance. It is also to be noted that in planning the airport, many important things like transportation issues for passengers, development of access, other facilities and services, accommodation, information services, and the special needs of the various types of craft and hangar space required are crucial.

The general guidelines for the construction of airports relates to not only the technical but also the economic considerations. While private enterprise in the aviation sector is now possible, there is the general concern about the feasibility of the projects from the angle of the government, state or the city, because in developing the airport, the authorities have to develop infrastructure outside the airport to make it useful and viable. The plan to build the airport must also take in the latest concerns of the environment, noise pollution and other similar concerns for which legal requirements have been notified. Therefore the important aspect is the study of the regulations concerning the airport which will help in defining the proper structure of the plan.

Regulations and requirements

The Federal Aviation Authority -- FAA passed the "Vision100 - Century of Aviation Reauthorization Act," which among other regulations also allowed for the allocation of the AIP funds for the facilities like hangars and fuel farms. This is stated in the law that the secretary can pay the funds "apportioned to the airport sponsor under section 47114 (d) (3) (a) and if the Secretary determines that the sponsor has made adequate provision for financing airside needs of the airport." ("Airport Improvement Program," 2004) Therefore all planners and builders are required to submit a business plan. In the event where the promoter of the proposed airport is not requiring the genera fund, still considering these guidelines will help in determining the profitability and the types of facility and structures required. The foremost concern is to evaluate the need. The plan must show the demand envisaged for the facility. There must be clear documentation that shows the intent to rent hangar space. There must be a very clear idea about the revenue that can be generated from the hangar or facility. There must be a comparison with other airports that provide similar facilities. "For hangars, the plan should show the rental fees for hangar space and the basis for determining those fees. For fueling facilities, the plan should show the amount of projected fuel sales, the amount of revenue to be received from each gallon, and the basis used to determine that amount." ("Airport Improvement Program," 2004)

The construction must comply with all federal, state and local regulations especially if federal funding is involved. All hangars will have to comply with the requirements that where the hangar is delegated for management to the FBO, then the FBO is entitled to management fees. The hangar is to be used only for parking the aircraft and the facility must not be used for other services like maintenance, painting etc. There cannot be any discrimination between users of the hangars. ("Airport Improvement Program," 2004) While some of these regulations apply to the funded projects, they also fit the general principles of the air port management. The considerations for selection of a site for developing an airport other than the Fixed Base Operator -- FBO rules will include passenger accommodation, aircraft facilities, hangar space, maintenance, fuelling facilities, flight crew and office space, the volume of traffic, noise laws, the runway, instruments and the mode of operation and security issues. The designs of hangars have to be in such a way that the moving of aircraft to accommodate another is minimized so as to avoid the damage that could be caused. Most companies prefer their own hangars or shared hangars that are leased out to the known players for security reasons. (Sheehan, 2003)

There is a need to evaluate the plan carefully because once invested there is a resistance to change. The existing structures or those already built cannot be easily abandoned and there is a general resistance to such moves. The funding for renovation and change may also be tardy. (De Neufville, Odoni, 2002) Therefore care must be taken over the existing structures and the proposed plan and both must be considered almost unchangeable. Hangar development plans follow the general development plans, and mostly relate to regulations and legal requirements, environmental issues, and the type of the airport. There are no general principles that can be applied at all situations and airports. A hangar development project essentially is like any other business development plan. The most important aspect in the development of the airport plan is the understanding of the existing facilities and the requirements concerning the airport and the systems like the regional transportation system. ("Airport Ground Access Planning Guide," n. d.)

This involves analyzing the improvements needed for airport ground access. That is the important place to begin, for without proper access the airport is rendered useless for practical purposes of civil aviation. The NFPA 409 regulation for hangar fire protection with regard to various groups of hangars like Group 1, 2 and 3 type of hangars are as follows: The group I types are required to be protected with foam-water deluge system. The hangars housing giant craft like the Boeing 747 should have an additional system. The fire fighting system must be able to sprinkle foam to blanket the whole hangar floor space for the group II types of hangars, the foam-water deluge system is recommended and they can also use the high-expansion foam system or sprinklers or even the water sprinkler system. The group III system does not require the fire protection system but if this type of hangars is used for hazardous purposes like fuel transfer, spray painting, welding etc. The group II requirements will apply. The tremendous cost of the systems and the clean up procedures for the accidental discharge as stipulated by the Environmental Protection Agency -- EPA will cause tremendous increase in the cost of the overall state of the cost ratio. (Reese, 2000)

Hangars and airports

Hangars are an important part of aviation and the need was perceived from the first aircraft to be built, and a hangar, or the first hangar was created by Louis Bleriot on crash landing in Northern France in 1920. The plane was stored in a farmer's cattle pen. The word "Hangar" in French means the cattle pen. It was Louis Bleriot who first ordered Hangars to store the aircraft. ("History of Airplace Hangars and REIDsteel," n. d.) Airports without hangars are unthinkable today as not only storage spaces but also the hangar today has come a long way from the cattle barn types that were used to house planes. Today hangars are centers that provide a host of services to aircrafts which are absolutely essential. Therefore in creating any airport, there must also be commercial plans to create the hangar and hangar facilities, without which an airport will be almost crippled. Planning hangars is dependent on the plan and capacity of the airport itself. The type of airport determines the need for hangar space. Large volume airports that cater to different types of planes need bigger and complicated hangars as compared to air ports that have lesser traffic and are limited to smaller planes. The cost, expansion and other aspects of the hangar thus depend on the airport.

Planning Airport Hangars

There are more aircrafts than hangars. Hangars are important revenue earning facilities at airports. The type of hangar and the facility it offers often determine the profitability of the airport. There are many things that have to be considered before embarking on a hangar development project. The current state of the airport or the plan for developing the airport is very important in planning hangars. The need for hangars, the type of hangars required is very important. Especially for those who wish to invest in the hangar as a commercial activity. The airport hangar waiting list is a good source to asses the demand for hangars, where the analysis is being done for development of the hangar with the airport the parameters will of course depend on type of demand for the airport. At any case, the objective is to arrive at the reasonable demand forecast and the type and requirement of the structure for the hangars. Once this is achieved, a SWOT -- strengths, weaknesses, opportunities, and threats Analysis is to be conducted with the available information for the proposed hangar. At this stage the funding options and the interaction and airport developer's concurrence is obtained. The rentals and other financial formalities are also worked out.

The type of hangar and the facilities offered determines the outlay of the operations. It is good to be wary of the environmental issues and the mode of obtaining the environmental impact report -- EIR. The issues "include noise, traffic, water runoff, water use, soil impact / degradation, visual impact, and vegetation or animal impacts." ("Aircraft Hangar Development Guide," n. d.) Some ecosystem requirements will make the whole project unviable and it is better to be aware of it in the first stage of planning itself. A well planned hangar system can help reduce the airport's trade deficits and augment its income. This is so because airports can generate income from fuel sales and rents. In case of a private company owning the hangars on lease, or where the airport owns it, in both the cases the hangars are the medium of revenue for the airport, the other being proceeds from sale of fuel. Therefore sound planning in development of the hangar and fuelling facility is a must for the development and viability of the airport project. ("Aircraft Hangar Development Guide," n. d.)

The Considerations for Hangars

Commonly aircraft hangars are thought of as garages for planes. There are many types of hangars from providing simple shade to complex facilities. The air force has developed the concept of hangars as seen in the history of aviation. The considerations for selection of a site for developing an airport other than the FBO rules will include passenger accommodation, aircraft facilities, hangar space, maintenance, fuelling facilities, flight crew and office space, the volume of traffic, noise laws, the runway, instruments and the mode of operation and security issues. The design of hangars has to be in such a way that the moving of aircraft to accommodate another is minimized so as to avoid the damage that could be caused. Most companies prefer their own hangars or shared hangars that are leased out to the known players for security reasons. Hangars are important to avoid theft, and sabotage especially in the modern context. ("Selection of Hangar Sizes and Style," n. d.)

Guidelines for hangars follow the types of hangars as described by the authorities, and can be classified as Type I and Type II. These are described in detail in the AFH 32-1084 Standard Facilities Requirements Handbook. For a commercial airport the designer is concerned with the size of the planes that will use the hangar and the type of facilities envisaged at the hangars. The Boeing aircraft for example has its own requirements. Apart from the aircraft requirement the design must accommodate the laws and regulations that are local to the area where the hangar is to be built. The optimization of the hangar space occurs when it is designed to accommodate many numbers of aircrafts and different types of aircrafts. The Hangars have five types of facilities, namely:

1. Hangar Area, this is the area or space for the whole hangar for all its functions, be it storing planes, or services, and the hangar space will have to be designed for the optimum space use for this purpose. 2. Shops Area, This is the area where service facilities like painting; cleaning or other specialist facility for the aircraft maintenance is set up. All the hangars even if it is for storage ought to have a small service area. 3. Warehouse Area, must be separate to store the materials needed for the service of the aircraft and this has to be designed in keeping with the fire hazard and other storage rules. 4. Office/Administration and Specialty Areas, 5. Building Utilities Area" (McLaughlin, 2007)

There are tie downs and composite structures, for example the City of Sierra Vista has tie-downs and hangars which are "furnished with lighting, electrical outlets, skylights, roof turbine vents, and most have electrically operated doors." ("Hangars and Tie-Downs," n. d.) There is also an aircraft wash rack and have sixty two hangars and thirty five tie-down facilities. These hangars are forty one feet by thirty two feet. Why it is mentioned is that a municipal airfield has these facilities for aircraft and therefore modern planners ought to look beyond.

Types of hangars in general

The first type is the Simple Hangar. It usually has a span of 60m. These types of hangars are built with steel structures that are portal framed or tied hangar types. There can be any span with propped portals. The second type is the Truss Hangar that can span to a 100m. These types can accommodate the Boeing 747 / Airbus A380 sizes. The third or Archspan Hangar will span more than 200 meters. The next is the Glove Hangar that is created to suit an individual type of aircraft in such a way that the nose and end part of the hangar is reduced in size to suit the plane exactly. This is accommodative of only one type of craft. The other types are the Spine Truss Hangar, and the Cantilever Hangar "Cantilever hangars can be 1000m long with no columns. Cantilever hangars need substantial counterweight behind, best provided by multistory office and workshop of about 1/3 of the total hangar depth" ("Selection of Hangar Sizes and Style," n. d.)

Similarly the "Spine truss hangars may on occasion be economic where the span is wide up to 150m and the depth small less than 1/3rd of the width." ("Selection of Hangar Sizes and Style," n. d.) the Cantilever hangars afford future extension and can take on any dimension for future expansion. It could even extent to a kilometer if required. There need to be an office and work zone that needs to be used as a counterweight. Another type, the Butterfly Hangars has aprons both sides. Aircraft Maintenance Hangars provides space for the change of base for the load and to provide optimum time saving in terms of flight line. These types of hangars ought to be in line with the airport flight line. The roofs are designed with the cantilever system. This also is expandable. The cost of erecting and sequencing can be high and requires constant maintenance. Another system used is the header truss system which rests on the front walls of the hangar. This eliminates the expansion joint along the centerline of the hangar bay. (Donnally, 2007) Another type of hangar is the painting hangar which requires special care in construction. Airflow is the greatest concern here. The authorities have recommended a flow range between 50 and 75 cfm/ft2 for the navy experiments in hangar construction.

The planning of the Hangar

There are types and types of hangar space requirements. It varies from airport to airport and from hangar owners and individual requirements based on aircrafts that may use the hangars. Pre-Engineered components are flexible in the sense that they can be modified easily and rearranged to suit the requirements. It is necessary to take many things into consideration while preparing to plan the hangar space. There must be special note of the local zoning rules and the careful study of the aircrafts that use the airport, and also the potential for new aircraft and scope of expansion before even deciding on the planning methods and type of hangars. ("Planning your Aircraft Hangar," n. d.)

Location of the hangar is very important, especially if the hangar is to be a business by itself. In the case of the hangars being an investment as a business, the airport and the proximity to the airport facilities is the prime criteria. Because of the vast requirement of land, there is also a factor of availability of marginal land for the least cost and this coupled with the local laws regarding land use ought to give an idea of the location. If the hangars are to be situated within the airport, then too the considerations regarding the optimum use of land and the requirement of the limited resource to alternate important uses by the airport comes into play. Leasing land on long-term lease basis is one option that is better tan buying the land because the leases can be flexible and will help in determining the continuance of the project. The lease can be terminated at short notice and least cost as against an attempt to sell property near the airport. (Lindsey, 2008)

The availability of other utilities and services like transportation, fuel dumps, and even the local weather will determine the hangar space considerations. The next step is to determine the dimensions of the site, for the hangar and the hangar in relation to the airport facilities, property dimensions and requirements, and other access patterns, individual units and so on will determine the land use. The construction of the hangar may have effects on the market value of the property in the sense that the market value of the property in terms of hangar space is based on a different yardstick than the commercial value of property development. Hangars do have a market value that is different from the use value, since they can also be sold or rented in the open market. The sale of a hangar along with the property will accompany the sale of the aviation business or hangar business. This is a peculiarity unlike other commercial buildings. Therefore hangar space need be separated from other property components in assessing value. (Lindsey, 2008)

Most hangars are constructed in leasehold property. Therefore the augment in value will be a lease hold rent interest. Most airports also lease hangar space and the consideration therefore will be identical. Most airports are established by the local bodies or by the states. In such cases the terms of lease will depend upon the state policies. The airports that are funded by the Federal Aviation Administration have some restriction placed on leasing land, and the process will follow regulations stipulated. The construction of hangars and buildings in such funded airports must t comply with all federal, state and local regulations. All hangars will have to comply with the further requirements that are peculiar to the ones that are delegated for management to the Fixed Base Operators -- FBO. This will relate to hangars that are used for parking aircraft only and there must not be other activities in the hangars. ("Airport Improvement Program," 2004)

With regard to airports that receive the funds, further restrictions are placed to the extent that the landside development, which includes terminals, hangars, and parking lots are called landside developments and these can be transferred to other parties. The airside developments that include holding bays, aprons, ramps, taxiways, runways and so on are non-transferable. In most cases the landside development area is held in lease by the Airport authority or developer. These areas are leased out of about forty years in lease to the applicants to develop the infrastructure like hangars. Therefore many considerations of developing the hangar will depend upon the economic and demand considerations along with the cost and viability factors. ("Airport Improvement Program," 2004)

Determining the size and functions of the hangar

The important definition of the hangar will be its size and the functions that it is envisaged to perform, and in most cases hangar requirements are dictated by the airport use, the type of aircraft and the requirements of service. The airport requirements will have to also be considered. The important thing is to list the type and the number of aircraft that may need to be housed at any given time. The type of services that is proposed to be offered also determines the need for hangar space. Is there only parking envisaged, or will there be services like avionics and maintenance services? The administration of the hangar and the mode of operation determine the facilities like office space, warehousing and housing of components ad machinery. ("Planning your Aircraft Hangar," n. d.)

Common domains in the hangar include the hangar itself, which is designed by considering the factors mentioned above, the shop space, which is the space for maintenance services proposed, avionics and other specialized services like painting, airframe work, and other services may require special space and layout, and also there will be a need to define the type of machinery and equipments like machine tools, overhead hoists, and equipment special for the tasks that are envisaged to be taken up at the hangar need be clearly chalked out. When the shop space is determined, it will lead to the consideration of warehousing, which will be required either for storing the required components for service or for the general provision of aircraft necessities. This brings into the picture a whole gamut of logistic and spatial determination for warehouse facilities. ("Planning your Aircraft Hangar," n. d.)

Office facilities require special office floors and apart from the work space will also require lounges, wash rooms, toilets, mess, meeting halls, and mostly overnight stay facilities for staff. Sometimes the facilities are created depending on the hangar policy. The last in consideration is the structure and the utilities of the building that ought to be present including the mechanical like lifts, air-conditioning, fire protection, fuel storage facilities, and communication facilities like phone lines and internet, and water proofing and weather proofing of all systems. Most features are to be present in all hangars, but there can be minimal facilities in hangars that do not require an office, where controlled from the airport itself for example, there are other things that are mandatory for the hangar, which is more by way of design and commonsense consideration rather than by statute or requirements. ("Planning your Aircraft Hangar," n. d.)

The height of the hangar will be determined by the tail height of the biggest plane that is meant to be stored, and the width by the wing spans and moving area of all the number of planes that are proposed to be housed at a time. This forms the basis of any planning of hangar space. The whole structure has to be absolutely water proof, and the modern construction methods and materials ensure this. For example with the changes in requirements, semi-permanent structures created with metal are changeable and accommodative as compared to rigid structures that were constructed earlier. The door of the hangar is an important part of the hangar which attracts the customers, and is the most important part of safety. Hangar doors therefore are a separate class by themselves and ought to be studied separately and in conjunction with the type of building structure that is envisaged. ("Planning your Aircraft Hangar," n. d.)

General hangar amenities

The shop amenities that are required for a standard hangar will include pilot and passenger lounges, tailgate doors, and other utilities like compressed air and water lines, loading docks, under- or above-ground fuel tanks, heavy drains or waste systems, landing gear pits, dehumidifiers, insulation, skylights, eye-rinse stands, mezzanines, catwalks, cranes bridge, hoist, jib, or stacker, chemical drive-in doors, fire sprinkler or suppression systems, Specification of these requirements at the early stage is a must and the requirements will vary for the services to be rendered by the hangar. For example a paint shop requires more space, while a simple storage hangar need not have equipment space but floor space. If it is necessary to have an overhead crane or hoist, it has to be planned before hand because the crane may require the structure to be created accordingly. The Administrative office space is also very important considering that much of the hangar activity related to the business occur there. The offices can be designed either as corporate office structures or just as finished mezzanine areas. Office space is considered to be an amenity at the hangar. The office is usually at the hangar site and is also constructed of metal frame components and must therefore be considered in most cases as an addition to the mains structure. There must be a class and ambience surrounding the office space as modern users do not club it with the hangar any more. (Lindsey, 2008)

Hangar Doors

The doors are important by themselves, and the type of door is determined by a number of factors, that could need the specific type of door - like "sliding, vertical lift, bi-folding, fabric, etc. And each type has advantages and design implications for the overall structure." (McLaughlin, 2007) the door for example of the Granite Falls Airport Hangar is about 70' x 18'. The key feature is the door of the hangar for safety reasons. In the case of this phenomena door, "It was with strength and reliability in mind that a Schweiss BiFold Door was chosen to fit the 70' wide x 18' high door opening of a hangar adjacent the administration building at the Granite Falls Municipal Airport in Granite Falls," which withstands wind lash at 90 miles per hour. ("Granite Falls Airport Hangar," n. d.)

Hangar doors are critical in defining the hangar space and affording protection against the natural and man made calamities. Natural problems such as winds, hurricanes, earth quakes, tornadoes fire can cause loss of the planes and equipment stored. The door thus acts as a sentinel in stopping the natural fury. Therefore the design of the door and its type is of paramount importance. The second is the security concern, namely the problems of theft, sabotage, and even terrorism. Conventional doors have consideration for some elements but not all. The selection of the type of door largely thus is caused by the air traffic, plane type and climatic conditions, and the transactions at the airport. The operation of the door and its pressure is measured in terms of the number of times it is closed and opened. At one side of the building the hangar opens and closes one side of the whole building when ever it is opened. Hangar doors are one of the most critical components of the hangar. (Lindsey, 2008)

The types of doors are varied. They can however be classified into these general categories. The common door types are the. Bi-fold Doors, Tilt-Up or Tip-Up Doors, Hi-Fold Doors, Outrigger Doors, Vertical stacking overhead doors, Sliding or Crossover Doors, Folding Shutter Doors, and Side-Wall Stacking Doors. Bi-fold Doors have two doors that have good free-span width, but have loss in terms of height. It can also jam. But result in a loss of the vertical height. The mechanics are comparatively more complicated and expensive. These doors are strong, but poor quality doors can jam the Tilt-Up. Actually opens or tilts up, and has a single panel at the top. They need balance weight and therefore are not popular. Hi-Fold Doors have more folds in them and therefore achieve more compact nature but requires support bars the Outrigger doors are designed with wide, sliding door panels which slide out of the hangar's front entirely. It gives the maximum clear space span. Only thing is that there must be special room outside the hangar for the sliding. The Vertical stacking overhead doors are made of panels that are attached to cables and can be made into a stack. This provides full width availability. (Lindsey, 2008)

The sliding or crossover doorway has a door that rolls to the side of the hangar. There can be up to eight panels that can be rolled to a side. The Folding shutter doors have multiple leafs like the accordion and fold on hinges. And result in a loss of span width. the, side-wall stacking doors are vertically stacked on the walls and curve into the side walls and they fit into the curve. There are some operational problems though. The important aspects that have to be considered with regard to the choice of the door include the climate which dictates the strength of the door to withstand the wind and sleet, and the motorized or manual operation mode. The need to look at the use of implements like wheels rails and their disadvantages must also be considered. Modern hangars come with a host of facilities, for some of which the door is an important part of the function. This includes the facility to reduce noise, vibration, simultaneous opening and closing type Aperture doors. The hangar doors are now designed to resist bombs, and electromagnetic radio waves. There are a host of facilities at hangars that require different types of doors. (Lindsey, 2008)

The costs of hangar doors are also a planning factor. Since it covers most of the hangar space, the costs of doors must be analyzed before selecting the door type. The costs of the door could be between $15.60 per face square foot for bottom-rolling door and $18.10 per face square foot for the bifocal unit. A large corporate hangar will cost $25 per sq feet and the addition of sales tax, and additional cost of installation all make it a costly affair and worth planning while planning and budgeting the hangar. (Lindsey, 2008)

The modern door architecture

One example of the modern hangar door is the door made for the Monolithic Dome Hangars. This is a patented type of door with the patent granted to David B. South with U.S. Patent 7,013,607. This new door is called the 'Monolithic Contoured Laterally Moveable Access Door. (South, 2006) in the Monolithic Dome Hangar, the door is suspended from a curved overhead track. The bottom rests on rollers. The door is a single piece. With a curved shape, it offers wind resistance. The hangar itself can be thus designed to the shape of the plane, with wide extents in the sides and higher at the tail area. The problems faced by other type of doors and hangars are eliminated by the special shape of the door. It goes to show that as demands for different types of hangar space increases with the types of aircraft, innovation and redesigning is necessary for the structures of the hangar like the door to accommodate the demands of the ever increasing need for space. (South, 2006) Thus the bigger the hangar becomes, more is the attendant problems regarding designing of its components like doors and structures. Flexible structures offer more scope of expansion at lesser cost.

Designing Hangars

Economic considerations are the following: The major consideration will be the type of aircrafts and the aircraft mix. The maintenance functions that are intended to be performed come next. This will lead to the design in terms of area of the shop. Warehousing, floor space, and important purpose arenas, like locker rooms, lobbies, toilets berthing and dining places, building maintenance and utility areas have to be considered. The hangar has to be clearly defined in terms of the maintenance that will be made available to aircrafts. There can be any type, with zero maintenance to a complete aircraft overhaul. The hangar will be designed based on the individual characteristics of planes likely to use it. Planes like the Boeing, Cessna, Piper and Airbus all have different requirements. Hangar Space Requirements are determined by making efficient use of space, and there are minimum distances that ought to be kept between crafts, especially where maintenance operation is involved. The statutory definition of this is found in 'AFH 32-1084 Standard Facilities Requirements Handbook'. (Gott; Lowe; Notarianni; Davis, 1997)

There are stringent fire protection rules and these have to be adhered to. "The high cost of modern aircraft justifies reexamining present fire detection and sprinkler activation methods to determine if new approaches could lead to a quicker response to a smaller fire, with the benefit of substantially reduced damage to aircraft adjacent to the fire source. The Naval Facilities Engineering Command -- NAVFAC established a unique Government/industry partnership to evaluate detector and sprinkler activation in aircraft hangars." (Gott; Lowe; Notarianni; Davis, 1997) Fire protection rules are also found in the "National Fire Protection Association standard, NFPA 409 - Standard for Aircraft Hangars establishes four different groups of hangars based on their size and construction type. In general, the smaller the hangar space the less expensive the fire protection and utility requirements." (McLaughlin, 2007)

Engineering Considerations

The type of aircraft and the type of entry, the nose entry or tail entry can be influential in hangar design. It will affect the costs and also flexibility. Tail docking avails of more flexibility but in terms of cost is higher. The next design consideration will be the dimensions and the apron length. The height restrictions on the apron door are also to be considered. For painting hangars, additional things like volume, shape and partitions have to be considered. For work shops the ground floor area has to be measured precisely. ("Selection of Hangar Sizes and Style," n. d.) "Tail heights, and the width and height of the hangar door openings, the structural depth of columns and trusses and the turning radius of tow vehicles has to be connected to the aircraft. Also in larger hangars, distance to means of egress become a concern and should be laid out to meet local codes and NFPA 101 Life Safety Code." (McLaughlin, 2007)