How to spec a brush truck

Do your homework and consider these recommendations when designing your next brush truck

Many in the fire service have an affection for brush trucks, wildland engines, grass rigs, patrol pumpers or any one of half a dozen other names for the quintessential firefighting tool for fires in the wild. Brush trucks do it in the dirt, where their larger cousins fear to go.

Brush trucks even have their own NFPA standard — NFPA 1906 Standard for Wildland Fire Apparatus, which applies to light brush trucks and all other wildland apparatus.

The National Wildfire Coordinating Group (NWCG) Fireline Handbook, NWCG Publication 410-1, contains a classification system that types structural and wildland fire engines as well as water tenders. The NWCG's classifications provide a common terminology for fire apparatus, particularly for brush trucks where not only does the terminology vary by region, but so too do the configurations. Here are the classifications

  • Type 3: Minimum water tank of 500 gallons; minimum pump flow of 150 gpm
  • Type 4: Minimum water tank of 750 gallons; minimum pump flow of 50 gpm
  • Type 5: Minimum water tank of 400 gallons; minimum pump flow of 50 gpm
  • Type 5: Minimum water tank of 400 gallons; minimum pump flow of 50 gpm
  • Type 6: Minimum water tank of 150 gallons; minimum pump flow of 50 gpm
  • Type 7: Minimum water tank of 50 gallons; minimum pump flow of 10 gpm

Draft FEMA resource typing mirrors NWCG for Type 3-7 engines and tactical water tenders.

Spec writing
Writing the specifications for a wildland engine may not be as labor and time intensive as it is for other apparatus, but it is wise to take a deliberate planning approach to the process. Fortunately, a number of the major manufacturers of wildland engines now provide wildland engine specification templates on their websites, and many include sample specification packages from previous customers.

First, if your wildland engine could participate in operations at federal incidents and you want to file for compensation, it must be NFPA 1906 compliant. Even if this doesn't apply, specifying a wildland engine that's NFPA 1906 compliant potentially increases the vehicle's trade-in or resale value. 

Here are some of the key points to that compliance:

  • Gross Vehicle Weight Rating: NFPA 1906 applies to apparatus with a GVWR of more than 10,001 pounds.
  • Rollover stability: Vehicle must pass SAE (formerly the Society for Automotive Engineers) test J2180: A Tilt Table Procedure for Measuring the Static Rollover Threshold for Heavy Trucks. For vehicles with GVWR of less than 33,000 pounds the threshold is 30 degrees; 27 degrees for vehicles with GVWRs greater than 33,000 pounds. Or the vehicle's calculated vertical center of gravity height divided by its rear axle track width shall not exceed 75 percent of rear axle track width (80 percent for vehicles with GVWR greater than 33,000 pounds).
  • Roadability: Vehicle must be capable of maneuvering across a 20 percent grade and up and down a 25 percent grade.
  • Carrying capacity: Weight allowance is based on GVWR. Many departments will carry much more than the minimum, so this needs to be specified up front. Brush trucks run a significant risk of being overweight.
  • Pumps: NFPA 1906 covers pumps up to 250 gpm; larger pumps must meet the requirements of NPFA 1901. NFPA 1906 rates pumps differently than 1901, both in flow and pressure. NFPA 1906 pumps do not require as many bells and whistles, such as line gauges, line drains, etc.
  • Pump-and-roll capability: NFPA 1906 defines pump-and-roll as delivering 20 gpm at 80 psi while traveling 2 mph. That's not a lot. If you want more — and you probably will — make sure your manufacturer knows this up front.
  • Foam delivery capability: NFPA 1906 recommends, but does not require, a Class A foam system. However, federal agencies require cooperators to have a foam proportioner on Type 3 wildland engines and tactical water tenders.

NFPA 1906 certainly provides a comprehensive standard for a wildland engine, and in addition you'll want to ensure that your wildland engine is customized where necessary.

Tank and pump customization
Select a pump that can provide the desired fire flow that matches the vegetation fuel load in your area. Attacking a fire in heavy brush with a small pump is dangerous and a waste of time. Likewise, attacking a fire in light grass with a big pump is inefficient and a waste of water.

Match the tank to the pump. Running out of water after only a few minutes of operation slows the attack and may give the fire enough time to grow out of control. A good rule of thumb is that the water supply should provide at least five minutes of continuous operation at your desired fire flow — 10 minutes is better.

Overloading the truck with too much water and equipment is unsafe and can break the suspensions or frame rails. Make sure to specify a truck with sufficient payload capacity to handle the expected load with room to spare.

Position the tank, pump, booster reels and other components low on the chassis to keep the vehicle center of gravity low for improved stability. This will also improve visibility to the rear and reduce the height of the vehicle for better overhead clearance.

Help reduce firefighter fatigue by mounting key components low on the vehicle. For example, mount the booster reel at the rear of the body so firefighters can deploy the hose off either side of the truck without the hose getting run over or snagged by the rear tires.

Other considerations
Having floodlights at the rear and on both sides of the apparatus can make night operations at wildland fires — easily the most treacherous time for combating such fires — more safe, effective and efficient.

Wildland apparatus may need to attack small structure fires, particularly in the wildland-urban interface areas. By adding a preconnected 1¾-inch attack line you can provide the necessary fire flow to knock down such fires. Make this hosebed low and easily accessible to enable firefighters to rapidly reload hose for bump-and-run operations during rapidly changing wildfire conditions.

Class A foam is a force multiplier and compressed air foam is even better. Foam penetrates fuels and coats surfaces to help knock down fires, prevent rekindles and reduce radiant heat exposures. Lighter hose lines mean less fatigue on firefighters as they drag hose through the woods.

Consider ISO requirements. This is especially important in areas protected by small volunteer stations where the only apparatus is a brush truck. Review ISO information on Minimum Facilities and Practices to Get a PPC Rating and Minimum Criteria for Class 9

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