Does your fire department need an aerial? If so, what type should you buy? There are aerial ladders, platforms and water towers in all shapes and sizes. Some extend by telescoping, others by articulating, and a few do both. They come in lengths from 50 to over 150 feet with tip capacities from 250 to 1,500 pounds. It's enough to make your head spin.
Fire departments contemplating an aerial purchase should consider what they need and what restrictions they have before they start writing specs.
Ladders vs. platforms
The first step is to determine which type of aerial best meets a department's needs. Will it be used primarily for firefighting or for rescue? Can the aerial be raised and extended in a straight line, or does it need to be articulated to reach up and over obstacles? Does it need a pre-plumbed waterway, or will it use a ladder pipe and hose for an elevated stream?
Aerial ladders are the most common aerial configuration. They come in lengths from 50 to 125 feet and ladder tip ratings from 250 to 1,500 pounds, with an average of about 500 pounds.
Aerial ladders are useful for rescue situations when there are a limited number of people to be evacuated at one time, and when the people are able to climb down a ladder. Ladders are also useful for firefighting situations when a single elevated master stream is needed or when a continuous means of access is required for firefighters to reach an upper portion of a structure.
When compared to aerial platforms, ladders are usually lower cost and lighter weight. They also usually result in a lower overall vehicle height.
Aerial platforms provide a versatile work position for both rescue and firefighting. They come in lengths from 70 to 105 feet for telescoping boom platforms, and 91 to 174 feet for articulating/telescoping boom platforms. Platform weight capacities range from 750 to over 1,250 pounds, with an average of about 1,000 pounds.
Aerial platforms are useful for rescue situations when there are a greater number of people to be evacuated at one time than can be handled safely on a ladder, or when the people have restricted mobility. Platforms also are useful for firefighting duties when more than one master stream is needed, or when heavy or bulky equipment must be transported to an upper portion of a structure. Articulating boom platforms are useful when the boom must reach up and over obstacles.
When compared to aerial ladders, platforms provide a larger working area and generally have greater weight capacity. Many platforms also can be angled to either side of the boom, which allows them to fit flush against the face of the building for safer access.
Water towers aren't as versatile as aerial ladders or platforms, but they still can give a department an added firefighting punch. They come in lengths from 50 to 130 feet and all of the models currently available have articulating booms. Water towers are especially useful for firefighting situations when an elevated master stream is required, but firefighters don't need to reach upper portions of a structure, such as fires in petroleum refineries, lumberyards, feed mills, agricultural packing sheds and other industrial structures.
If a vehicle with a water tower is properly sized and equipped to meet Insurance Services Office requirements, it can earn approximately 75% credit as a ladder company.
Specifying the wrong aerial length is a mistake that will haunt a department for years. ISO requires that an aerial must have a rated height of at least 50 feet and must reach the roof of any structure within the department's response area to earn maximum credit. However, ISO does not require, nor give credit for, aerials longer than 100 feet.
To determine the aerial length required to meet the ISO rating criteria, a department has to consider roof heights, building setbacks and differences in elevation. For example, a building with a 70-foot roofline sitting on a 10-foot rise above the street is effectively 80 feet tall. If the closest point of vehicle access to the building is 60 feet (remember to include parked cars on the street), then the department would need a 100-foot aerial — just to reach the roof of a 70-foot building!
Departments should also pause a moment and consider future requirements. If the area is growing, with new commercial structures expected in the near future, then it might be wise to spend more money for a longer or more versatile aerial now, rather than be stuck with an inadequate aerial in a few years.
Once a department decides what type of aerial it needs and how long the apparatus has to be, it needs to consider maneuverability. Aerials can be specified in several configurations, each with its own advantages and disadvantages.
Many aerial ladders and platforms are built on a straight-frame chassis with the base of the aerial mounted at the rear of the apparatus, and the aerial itself extending out over the cab. This rear-mount design can decrease the overall vehicle length, but it can increase the overall vehicle height. Departments that have to maneuver under low bridges or viaducts may have problems with this design. Some manufacturers offer a low-profile cab to help offset this increase.
Other aerial ladders and platforms are built on straight-frame chassis with the base of the aerial mounted in the middle of the apparatus, and the aerial itself extending to the rear. This mid-mount design can decrease the overall vehicle height, but it can increase the overall vehicle length. Departments that have to maneuver around sharp corners may have problems with this design. Some manufacturers offer aerials with additional, but shorter, sections to offset this increase. However, these can increase the vehicle height again.
Both the rear-mount and mid-mount aerial designs have longer wheelbases relative to pumpers and other apparatus, and therefore wider turning circles and more limited maneuverability. For the ultimate in aerial maneuverability, some departments specify tractor-drawn tillered aerials. Because this design pivots in the middle and is steered independently from both the front and rear, it can be maneuvered in very tight spaces. It's still a long piece of apparatus, though, and it requires special training to steer the trailer.
To avoid the embarrassment of purchasing a new aerial that can't be used, departments should consider other restrictions that may affect an aerial design.
Is the aerial too tall for the station doors? Is it too long for the apparatus bay? Is it too heavy for the apparatus floor? Is the stabilizer jack spread too wide for certain access roads? Is the wheelbase so long that the underside of the chassis hangs up when crossing streets with high crowns or when entering driveways with sharp grade changes? Are the posted clearance signs on underpasses and overpasses correct? Will there always be two people available to drive a tillered aerial?
A little thought now can save a lot of red faces later.
Aerial equipment manufacturers
888-ALF-TRCK for your nearest dealer, <www.americanlafrance.com>
Central States Fire Apparatus
Crash Rescue Equipment Service
Ferrara Fire Apparatus
General Safety Equipment
H&W Emergency Vehicles
Hi-Tech Fire Apparatus
KME Fire Apparatus
Luverne Fire Apparatus
Marion Body Works
Seagrave Fire Apparatus
Toyne Fire Truck
NFPA and ISO requirements
The National Fire Protection Association defines an aerial device as “an aerial ladder, elevating platform, aerial ladder platform or water tower that is designed to position personnel, handle materials, provide continuous egress or discharge water.”
NFPA 1901 covers the design and construction of fire apparatus, with specific sections regarding aerial devices. NFPA 1914 covers the periodic testing of aerial devices. NFPA 1915 covers the preventive maintenance of fire apparatus, with specific sections regarding aerial devices. NFPA 1071 covers the qualifications of emergency vehicle technicians who perform inspection, diagnosis, maintenance, repair and testing of emergency response vehicles, with specific sections regarding aerial devices.
Any fire department considering the purchase of a vehicle with an aerial device should have the latest editions of these standards.
The Insurance Services Office has its own standards for rating aerial devices. On some points, the ISO standards differ from the minimum standards in NFPA 1901.
For example, if a department wants to obtain maximum ISO credit for a vehicle with an aerial device, the device must be equipped with a 1,000gpm elevated master stream. NFPA 1901 has this requirement for elevating platforms, but not for aerial ladders. To give maximum credit, ISO also wants more ground ladders than the minimum required in NFPA 1901.
Departments considering how the specifications of a vehicle with an aerial device will affect their ISO rating should discuss this with their apparatus manufacturer or contact their local ISO office.