Photo by Tom Shand The Levittown, NY, Fire Department operates this well-designed Pierce Lance 105-foot rear-mount aerial ladder. Ladder 626 carries an extensive complement of ground ladders on the right side of the body as well as off the rear. In the November 2004 installment of “The...
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Photo by Tom Shand
The Levittown, NY, Fire Department operates this well-designed Pierce Lance 105-foot rear-mount aerial ladder. Ladder 626 carries an extensive complement of ground ladders on the right side of the body as well as off the rear.
If your department is in the process of replacing an existing aerial device, it would be a great idea to break out a tape measure and record the wheelbase, overall length and overall height of the present rig. This will provide the committee with a barometer of the critical measurements when evaluating new vehicles.
Any fire department buying a new aerial apparatus should measure the available clearance through the overhead door and the usable depth in the apparatus bay where the rig will be stored. More than one fire department has been surprised when it took delivery of its new 100-foot rear-mount tower ladder, only to find out that the rig didn’t fit into the station because it was too high. Don’t take the word of another member in the fire company about how big the bay is; actually measure the door opening and, if needed, place the ladder truck into the door opening to determine the exact clearance that you have in the apparatus bay.
The maximum allowable dimensions for the apparatus must be clearly spelled out in your specifications in order to allow prospective bidders to prepare an adequate bid response. Completing the Apparatus Purchasing Specification Form in Annex B of the National Fire Protection Association (NFPA) 1901 Standard would be a good start for any apparatus committee to undertake prior to setting out with the specification process.
First, let’s look at midship-mounted aerial devices and what design features they offer. A midship aerial device provides a lower overall travel height for those departments that have reduced-height bay doors, bridges or underpasses that would restrict travel. By varying the position of the turntable on the chassis frame, the overall travel height of the apparatus can be modified to meet the individual needs of the fire department.
As the overall height of the vehicle gets lower, the space for ground ladder storage and the usable compartment space are reduced accordingly. The NPFA requirement for enclosed compartment space on an aerial ladder or quint is 40 cubic feet with a payload capacity of 2,500 pounds. Unfortunately, many ladder trucks are designed to meet these minimum standards, but have little or no usable space to accommodate the needed equipment and ground ladder complement.
Midship aerial devices are generally easier to spot and position on the fireground, as the center-mounted turntable allows the operator to locate the center of the turntable with the midpoint of the structure. Units that have raised-roof cabs can inhibit the ability of the aerial device to operate at low angles when a device is working off the front of the apparatus. This is particularly important with mid-mounted tower ladders where it may be impossible to operate the tower at angles below 30 to 35 degrees.
Photo by Tom Shand
The Peoria, AZ, Fire Department operates this American LaFrance mid-mount tower ladder as Ladder 193. Note the height of the side body compartments and the lack of any equipment on top of the body that could inhibit use of the tower at low angles.
Your fire department may be limited to a midship aerial design due to overall height limitations within the community; if so, the committee should work diligently to develop specifications that provide the maximum number of components that will benefit the department. Midship aerial and tower ladder devices offer superior scrub-area coverage on buildings when compared to rear-mounted apparatus. Scrub area is defined as that part of the tower ladder bucket or the tip of the aerial device that can touch the building line. The better the scrub area of a particular aerial device, the more use your department will get on the fireground. Better scrub area is a direct result of apparatus positioning on the fireground, apparatus design and what vendor you choose to build your aerial device. Design features such as outrigger placement, body heights and ground ladder arrangement are much more user friendly than rear-mounted devices. The fire department can often benefit from the input and perspective of an apparatus architect in this regard.