The image of a tillered tractor-drawn aerial ladder truck responding to a fire is part of the American heritage of firefighting. Although tillered aerials aren't as common as they once were, their advantages still make them popular with some departments.

Now their popularity is gaining strength with the introduction of a new generation of tillered aerial quints that combine the advantages of both configurations into a vehicle that's as versatile as it is long. If you haven't considered tillered aerials, you may not be aware of their many advantages.

First, and possibly most important, they are highly maneuverable compared to straight-frame aerials. The combination of an articulated tractor-trailer vehicle with the steerable rear axle allows some tillered apparatus to turn around in a cul-de-sac at the end of a street. The rear steering also allows the apparatus to be maneuvered easily into position at crowded incidents.

Another big advantage of tillers is they have lots of compartment space with street-level access, allowing firefighters to easily grab ground ladders, tools and equipment without having to reach overhead or climb on the apparatus. This speeds operations and helps prevent injuries from strains and falls.

The disadvantage of the long overall length of tillered aerials is offset by the advantages of several other dimensions. For example, the short rear overhang on the trailer and the distributed three points of contact between the tractor-trailer combination and the ground give tillered apparatus good ground clearance and high angles of departure. In many cases, this allows them to traverse sharp gradient changes and high-crowned roads more easily than long, straight-frame apparatus. The low turntable height on tillered aerials also gives easier entry and exit to the ground and can contribute to a closer set-down position when the ladder tip is positioned to the side

And because tillered aerials have mid-mount ladder designs, the loads imposed by the raised and extended aerial are more evenly distributed to the ground. The apparatus often can be designed with a single set of outriggers; jack-knifing the tractor and trailer also adds significant side stability that can't be achieved with straight-framed aerials.

Quints add versatility

Adding a properly sized pump, tank and hose capacity to a tillered aerial turns it into a tillered quint. In turn, that adds versatility to an already good design.

For example, a quint can be used to put an elevated master stream into operation with the supply hose and pump it normally carries. It doesn't need a pumper to lay a line from a hydrant or to provide pressure, and it doesn't need to tie up all the equipment carried on a pumper that might be better positioned elsewhere. This capability often allows departments to put elevated master streams into operation in less time to hit fires in the critical early stages — a factor that is sometimes the difference between potentially big fires and really big ones.

In cases when the distribution of apparatus within a department means that a ladder truck may arrive at a fire before the assigned engines, a quint often can make the initial attack with tank water to knock down the fire or clear an entry path for rescue operations. This tactic depends on department SOPs and should not be used in every situation, but having a quint gives a department the flexibility to use it when needed.

And finally, a quint lets a department gain pump credit on its Insurance Services Office rating. When ISO evaluates departments, they calculate the water flowrate for specific structures as well as the flowrate for the entire jurisdiction. Credit is based on the combined pump flowrates of all apparatus, not just engines. Departments that want to have all the advantages of a tillered aerial ladder, but also want to maximize their ISO points, may specify a tillered quint to get the best of both designs.

Tillers aren't for everyone

Despite their many advantages, tillered apparatus aren't suitable for every department. Because of their design, they tend to be longer, heavier and more expensive than other aerials. The length alone often precludes their use in older stations with short apparatus bays.

Tillered apparatus also require special training and qualifications for the tiller operator. In career departments, this may affect salary classifications and labor decisions. In volunteer departments, this may keep the apparatus out of service if qualified tiller personnel don't respond to calls.

Overall, tillers offer special advantages, but they also have special requirements. Departments need to consider both before making a decision.