Pre-engineered metal buildings are a popular choice for airport hangars, but not just any metal building is the right choice. Rural Builder turned to Erect-A-Tube, a company that designs and fabricates general aviation facilities of all sizes, for tips on how to help your customers make the right decision.
All metal buildings are not created equal
The pre-engineered building market is very homogeneous. Although most metal buildings may look the same from the outside, unless you really inspect each manufacturer’s product, it will be difficult to determine the quality differences between products. As with most purchases, it pays to understand the differences. Once the hangar purchase is made, any sacrifice in quality becomes apparent and lives on throughout the life of the product. Making the right choice returns dividends for many years through reliability, product longevity and ease of operation.
The first step to getting the best fit for a given situation is to determine the size and number of aircraft to be stored. This will dictate the number and size of door openings. The hangar door has its own set of criteria in order to properly integrate into the building.
Hangar specifications: nested or standard?
Once you know how many and the size of aircraft to be stored, you can establish the hangar specifications. With a nested hangar, the overall length of the hangar is reduced, potentially saving on taxi lanes and ramps. For standard configuration, also called “stacked,” the hangar is narrow but longer, requiring longer taxi lanes on both sides of the hangar. Both configurations are used when housing multiple planes with individual access.
Another option is a clear span unit, which can be sized for one or more planes in a given space. The amount of clear floor area will dictate the amount of storage area. Familiarity with the types of structural framing and the installation of the secondary members (i.e. wall girts) will result in the maximum floor storage space. The two types of structural framing commonly used in pre-engineered buildings are the tapered rigid frame and the open-webbed truss with straight column.
Choosing the right door
The hangar door is what differentiates an aircraft hangar from a typical metal building. It is the most significant piece of equipment that makes a building function properly as a hangar for aircraft. Whether bottom-rolling doors or electric bi-fold doors are selected, each has its own specific requirements that will affect how the hangar project is designed.
- Bottom rolling doors
There are two types of doors in this category. The first is a sliding door. This door system is supported from the top via a trolley that is inserted into a track system. The bottom of the door is guided through a series of intermittent door guides secured to the floor in the door opening. This is the same door system that is used on agricultural barn doors.
The second type, which is preferred, is the bottom-rolling door. This door system is designed with the weight of the door panels on the bottom rollers. The door system rolls on an embedded track and is guided by door guides at the top. A quality bottom-rolling door system should have door rollers that are eight inches in diameter. The larger the door roller, the easier the door will move. In addition, there should be ample weather stripping around all sides of each door panel.
Bottom rolling doors have specific requirements in order to work smoothly. It is important to control the building deflection or movement within the tolerances of the top guides. It is also important to have an adequate foundation for the door track.
- Electric bi-fold doors
The electric bi-fold door system is the most economical for hangars with door openings under 80 feet wide and 20 feet clear height. All the extra components required for bottom-rolling doors, such as the additional foundation requirements, the door pockets, the bottom track system and the header/soffit above the door, by far offset the cost of the electric operator.
Electric bi-fold doors are designed to act as a movable wall system while still capable of handling various wind conditions in the closed position. The door system is attached to the header system with several hinge pick-up points. When in the closed position, the door is latched to the vertical door columns and utilizes a cane bolt pin at the center of the door that drops into a socket embedded in the foundation.
The location of the door operators, their features and how they attach vary by manufacturer. Some operators are mounted on the door truss, while others are mounted on the door frame. In either case, there should be considerations given to the location of the operator and evaluation to the design features of each model such as:
- What are the electrical requirements?
- Are the door operators pre-wired to the push button station?
- What safety factors are incorporated?
- Are the door motor and gearbox integrated to provide a direct-drive system?
- Does the door operator have safety shields for protection of moving parts?
- Is there a safety override switch?
- Do you need to step over operator components when entering the hangar?
- What is the designed safety factor of the lift cables?
Checklist for success
Your research should include obtaining answers to the following important questions (Note: These are areas where some manufacturers attempt to reduce their costs while potentially sacrificing quality.)
- What are the exact building dimensions?
- What is the clear wing depth dimension?
- What is the clear tail bay width dimension?
- What is the clear overall unit dimension?
- Is the eave the correct height to provide the proper clearance for the hangar door?
- Whose hangar door is the building manufacturer supplying?
- Who is responsible if the door and building do not align properly?
- How is the door being supported?
- What is the size of the door jamb column?
- Where is the hangar door operator mounted?
- How much weather stripping is provided by the door manufacturer? Where is it located?
- What are the specifications of the walk door used in the hangar door?
- What structural components are used in fabricating the hangar door?
- Does the hangar door require diaphragm action from the sheets to hold the door together?
- How many wall girts and partition girts are included in the building price?
- What is the lap length of the roof purlins?
- How many bolts are used for the purlin connections?Are clips provided to prevent the roof purlin from rolling?
- What is the tensile strength of the exterior wall and roof sheeting?
- How many anchor bolts per column?
- What is the sheeting warranty?
- What is the paint warranty?
- Can the structure stand alone without the need of diaphragm action from the exterior sheets?
A local engineer is recommended to design the foundation for your aircraft hangar. The local engineer is familiar with local building codes, soil conditions and is generally required to inspect and oversee the foundation installation process. In order to design an appropriate foundation, the following information is considered:
- Topography of site
- Geotechnical data
- Column reactions
- Anchor bolt layout
- Stamp and seal of a state professional engineer
- Sloping the floors
Keeping water away from the building is a key element in any building process, including aircraft hangars. Airport engineers recommend the ramp slope away from the building be a minimum of 1 percent or a maximum of 2 percent on grade. This allows the water to drain away from the building yet still enables the pilot to move the aircraft into the hangar easily. RB
For even more tips and details, you can download the guide, “Everything You Need to Know Before you Buy or Build an Aircraft Hangar” from www.erect-a-tube.com.