The Apparatus Architect: Part 14

Tom Shand and Michael Wilbur begin a discussion on the design and use of aerial ladder units, apparatus that can represent one of the largest financial investments that a fire department can make.

With this installment in "The Apparatus Architect" series we begin our discussion on the design and use of aerial ladder units. These types of apparatus can represent one of the largest financial investments that a fire department can make, and here the adage "An educated consumer is our best customer" is certainly appropriate. Short-term decisions that will be made by the department will have a long-term impact not only on the type of aerial ladder equipment that is acquired, but on how the operational characteristics of the ladder device will impact fireground operations for the truck company.

First, a little history regarding power-operated aerial ladder apparatus is appropriate. The first hydraulic, all-metal aerial ladder truck was a three-section, 100-foot, tractor-drawn aerial produced by Peter Pirsch for the Melrose, MA, Fire Department in 1935. Prior to this date, most aerial ladder units were constructed of laminated wood sections consisting of a base section with a single fly section and were raised by a mechanical spring-loaded device. Following this design built by Peter Pirsch, other prominent builders of the day - Seagrave, American La France and Maxim - introduced their own hydraulic-powered steel aerial ladders ranging in length from 65 feet to 85 feet.

This ladder design, however, was slow to gain acceptance with major fire departments such as Boston, Chicago and the FDNY. New York placed its first hydraulic-powered aerial ladder in service in 1948, when it took delivery of a Seagrave 85-foot tractor-drawn aerial and was assigned to Ladder Company 110. FDNY continued to specify wooden aerial ladders through 1955, when it accepted delivery of 25 FWD 75-foot tractor-drawn aerials. Gradually, after this point in time, FDNY and other major fire departments slowly began to accept the metal aerial device, although the last wooden aerial ladder was not officially retired from the FDNY fleet until June 1973, some 38 years after Peter Pirsch had built its first powered ladder truck.

More recent advancements in aerial design can be traced to the development of the Snorkel articulating boom and the telescopic boom platform during the early 1960s. These devices were introduced into the fire service at a time when many cities were experiencing heavy fire conditions and the ability of both snorkels and tower ladder units to deploy elevated master streams with pinpoint accuracy greatly enhanced the ability of fire departments to control these major incidents. Another significant benefit of platform aerial devices is the enhanced safety characteristics of these units, which let firefighters work within the confines of the platform to perform rescue, exterior ventilation and overhaul.

One of the most significant developments in aerial ladder design occurred in 1991, when the National Fire Protection Association (NFPA) 1901 standard was introduced to require that aerial ladders be capable of operating in any position that the ladder would reach while supporting a minimum tip load of 250 pounds. The older-design units had proven to be very reliable when operated at relatively steep angles of elevation; however, they had not been designed to operate at full extension at low angles of elevation, which created conditions for aerial ladders to have catastrophic collapses. In addition, these ladders generally were limited in their ability to resist lateral forces.

All of these design and safety enhancements made the newer aerial ladder devices superior to their pre-1991 counterparts; however, the trade off was additional weight and size of the ladder sections that would require heavier chassis and tandem axles to carry the loads. The size of this new generation of aerial device has created driving problems as well as placement problems. Another trade off was the introduction of safety devices that actually made some aerial devices much harder to place and operate in a timely fashion. Some departments that operated smaller aerial units found that they were unable to purchase a replacement aerial ladder truck that would fit into older stations or had difficulty in maneuvering around in their first-due areas.

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