The Apparatus Architect – Part 27: Combination Rescue-Engine Units

July 1, 2006
Michael Wilbur and Tom Shand discuss the purpose of combination rigs: to deliver a wide variety of tools, equipment and personnel to an incident in a safe manner.

The April 2006 installment of The Apparatus Architect discussed some of the inherent advantages of custom and commercial chassis for use in designing rescue squad units. Each chassis provides distinct advantages for fire departments to consider when developing specifications for new apparatus. In contrast to the traditional walk-in rescue trucks, combination rescue-engines are becoming more popular among many departments.

The terminology for these units varies from department to department. In some areas, they are known as rescue-engines, rescue-pumpers, squads or enhanced engine companies. Regardless of the local designation, the purpose of these combination rigs is to deliver a wide variety of tools, equipment and personnel to an incident in a safe manner. At this point, there is no universally accepted definition for these multi-purpose units, nor is there an accepted standard for the equipment inventory that these units should carry. The National Fire Protection Association (NFPA) 1901 Standard on apparatus does not differentiate between a standard pumper and a rescue-engine other than to require that an apparatus with more than 250 cubic feet of compartment space must be able to carry a minimum of 2,500 pounds of equipment, in addition to the specified hose load and personnel.

Much like aerial ladder trucks that are designed as quints, from a practical viewpoint, the department apparatus committee has a great degree of flexibility when specifying a combination rescue-engine unit. One of the most important questions for the committee is to determine how the proposed apparatus is going to be used. If it is to be used for routine engine company responses in addition to extrication and rescue incidents, then these missions will in part determine how the apparatus and body compartments should be designed. If it will be an additional unit responding on the alarm, then the amount of engine company equipment, hose and ground ladders may vary widely.

One of the earliest articles in The Apparatus Architect series discussed the importance of “Defining the Mission†of the new apparatus. This is critical with any combination apparatus, but especially significant with a rescue-engine unit. While the present NFPA standards would require a minimum of a 2,500-pound payload for this style of apparatus, a similar unit designed as a special service apparatus with a gross vehicle weight rating (GVWR) of 47,000 pounds would require a minimum of a 6,000-pound equipment payload. Defining the mission of the vehicle helps determine what equipment will have to be carried on the new apparatus to meet its goals.

One of the common hurdles for the committee to establish is just how much engine company versus rescue equipment the vehicle will be expected to carry. If the apparatus is to provide engine company service within its response area, then it is reasonable to consider that a nominal complement of supply hose, pre-connected attack lines, ground ladders and other standard equipment will have to be incorporated into the body design. On the other hand, there must be sufficient room to carry hand- and power-operated extrication tools, cribbing and shoring materials, ventilation saws, airbags and hand tools together with electrical, hydraulic and air reels.

There is a critical balance between carrying the right equipment for the job versus carrying a little bit of everything that you believe you may ever need, but may never use, including that once-in-a-lifetime technical rescue operation. Some apparatus committees design the apparatus to do a little bit of everything and carry a little bit of everything, but when the apparatus arrives on scene, it does not have any degree of functionality and performs poorly.

Before establishing the guidelines for a combination apparatus, it would be appropriate for the committee to seek out other departments that have acquired rescue-engine units and obtain their tool and equipment lists. Such lists can provide a good starting point for discussion of how much and what equipment should be carried on the apparatus. Some jurisdictions have operated combination units for several years and the experience gained from them, particularly with operating guidelines and procedures, can be of great benefit to the apparatus committee. We have said this before: you need to know exactly what equipment is going to be mounted in each compartment before your committee leaves the pre-construction conference. With the expense of building the compartmentation, the days of unloading the equipment off the old rig, laying the equipment on the apparatus floor and back in the new rig and then trying to figure out where – and if – everything is going to fit.

Let’s consider what ground ladders a new rescue-engine should carry. Most standard pumpers carry a 24-foot extension ladder, a 14-foot roof ladder and a 10-foot folding ladder. These ladders fit well when mounted externally on the body or when mounted on a hydraulic ladder rack. These ladders, when banked together, are 171 inches long. With rescue-style compartments that are full height on both sides of the body, the ground ladders must nest inside of the body or in the hosebed and some forward portion of the ladders often end up within the pump enclosure. The alternative is to specify shorter ladders or a three-section ladder, which may take up additional space within the body.

Why worry about ground ladders? If we are going to spend upwards of $400,000 to acquire this new combination unit, it makes sense to carry the appropriate equipment to operate at a routine structural fire with our new apparatus. An often-heard comment about a rescue-engine apparatus, after it has operated at several incidents, is: “Our new rescue-pumper is a great rig, but not a great pumper or a great rescue.†To design a rig that will meet the present and future needs of the department, it is important to understand all of the missions that you want to accomplish in order to start out with the appropriate design. You do not, however, want the apparatus burdened to perform too many different missions or it may not do any of them well.

An apparatus architect can assist the committee in refining its requirements for the unit and provide guidance in developing the detailed specifications that will be needed to allow manufacturers to produce an engineering drawing and a cost proposal for the new apparatus. NFPA 1901, in Annex C, has an excellent table that outlines various tools and equipment together with their dimensions and weights. This information should be used to assist the committee in determining the types and amount of hose, tools and equipment that will be carried on the apparatus.

The weights of the equipment are important as the total weight of your proposed equipment inventory will often exceed the 2,500-pound minimum requirement called for in NFPA 1901. This information will assist in determining the appropriate size of axles, tires and suspension for the rescue-engine. This is important; as we travel the country consulting on apparatus fleets, we have found that many apparatus are overweight or close to being overweight on one or multiple axles or weigh more than the intended GVWR of the entire apparatus.

As combination rescue-engines become more common, there will be a wealth of knowledge regarding the design, equipment and deployment options that are afforded by these units. Fire departments will adjust and modify their standard operating guidelines (SOGs) to incorporate the changes needed to adapt the response of the combination rigs to support traditional ladder and rescue company assignments on the fireground. As with quint apparatus, these units will continue to evolve and change as needed to meet the increasing needs of the fire service.

The next installment of The Apparatus Architect will discuss some of the special design considerations for rescue-engine apparatus.

Tom Shand, a Firehouse® contributing editor, is a 33-year veteran of the fire service and works with Michael Wilbur at Emergency Vehicle Response, consulting on a variety of fire apparatus and fire department master-planning issues. He is employed by American LaFrance and is assigned to the Hamburg, NY, facility. Michael Wilbur, a Firehouse® contributing editor, is a lieutenant in the New York City Fire Department, assigned to Ladder Company 27 in the Bronx, and has served on the FDNY Apparatus Purchasing Committee. He consults on a variety of apparatus-related issues around the country. For further information, access his website at

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