Small twin-agent units usually are the first apparatus that airport fire departments purchase, and most airports have at least one of these mighty mites in their firefighting fleet, no matter how large they grow.

By definition, twin-agent units use two or more agents to extinguish fires. They also are called dual-agent vehicles or combined-agent vehicles. The agents might be a sodium- or potassium-based dry chemical, a gaseous material like halon, or a small amount of water and foam solution. Some units carry all three types of agents. Most airport fire officials favor multiple-agent capability because it gives them the flexibility to choose the most appropriate extinguishing material for specific fires.

The requirements for the types and sizes of aircraft firefighting vehicles at airports in the United States are determined by the Federal Aviation Administration. The FAA assigns each airport an airport index based on the number of scheduled air carrier passenger flights per day over an extended period, the number of passengers on each flight and the overall length of the passenger aircraft. As the number of flights, the number of passengers and the length of the aircraft increase, so do the requirements for aircraft firefighting vehicles.

Airports that provide aircraft fire protection services already fully understand these requirements. Smaller airports that have been experiencing a gradual growth in commuter or regional passenger flights need to be aware of the point at which they need to initiate an aircraft firefighting program. They also need to be aware of the points at which they have to expand those services. The FAA provides detailed information on this subject and also offers programs to help airports that are just getting started or trying to expand their facilities. (See “FAA Information Sources,” page 89.)

When an airport needs to purchase its first twin-agent unit, or even something larger, there are several requirements that must be met. Sliding a skid-mounted pressurized-agent unit into the bed of a pickup truck does not necessarily make it a compliant twin-agent unit. Both the FAA and the National Fire Protection Association have established detailed standards with requirements for vehicle configuration and performance, as well as firefighting agents and equipment. There also are requirements for staffing, training, response time and other aspects of aircraft rescue and firefighting operations.

The FAA Advisory Circular 150/5220-10D, Guide Specification for Aircraft Rescue and Firefighting Vehicles, defines requirements for all types of airport firefighting vehicles. It uses NFPA 414, Aircraft Rescue and Firefighting Vehicles, as the basis for determining vehicle configuration and performance with several exceptions and modifications. Some portions of the NFPA standard are not allowed. This document also includes a variety of vehicle options not mentioned in the NFPA document, but commonly specified by airport departments.

The 2007 edition of NFPA 414 contains requirements for vehicle weights, dimensions, performance, chassis components, body construction and firefighting agents and systems. Side stability, gradeability, turning radius and acceleration are important factors. If the airport also provides non-aircraft rescue, emergency medical and structural firefighting services, the apparatus used in those applications would fall under the appropriate NFPA 1901 or KKK 1822 standards.

When specifying apparatus, airports also need to plan ahead to select the best configuration for future needs. If an airport expects very little growth of passenger air traffic in the coming years, then purchasing a twin-agent unit with a pressurized discharge system, handline and a minimum of 120 gallons of pre-mixed water and foam capacity may be the most economical solution. If the airport expects a significant increase in air traffic that would boost the airport index, however, then purchasing a larger twin-agent unit with a water pump, foam proportioning system, remote-control turret and water capacity of 500 to 750 gallons may minimize future apparatus costs and be more economical in the long run.

Whatever approach airport fire departments take, they need to understand all the standards and regulations before they start. They should review the FAA and NFPA documents and contact a knowledgeable apparatus manufacturer for advice on writing specifications. The purchase of a properly sized and equipped twin-agent unit is the first, and most important, step.

FAA Information Sources

Federal Aviation Regulation 139, Certification of Airports, defines the overall standards for airports, including requirements for the number of airport firefighting vehicles and the quantity and types of extinguishing agents and equipment to be carried. These requirements are based on the Airport Index, which is fully explained in this document. To view and download a copy at no charge, go to www.faa.gov and click on “Federal Aviation Regulations” in the menu, then click on “Current Federal Aviation Regulations” and select the numerical bracket that includes FAR 139.

The FAA Advisory Circular 150/5220-10D, Guide Specification for Aircraft Rescue and Firefighting Vehicles, took effect in late 2007 and includes requirements for both TAU and ARFF vehicles. This 16-page document supersedes all previous advisory circulars and is to be used in conjunction with NFPA 414, with the FAA requirements taking precedence over the NFPA requirements in case of a conflict. To view and download a copy at no charge, go to www.faa.gov and click on “Advisory Circulars” in the menu, then type the number “150/5220-10D” in the search box.

The FAA Airport Improvement Program provides partial funding for various improvement projects including those relating to airport safety and security. For an overview of the program, go to www.faa.gov/airports_airtraffic/airports/aip/overview.