Why is it the majority of the most recent ARFF truck rollovers have happened during training exercises? Is it because we as ARFF truck operators let our guards down during training by driving faster than we should be? Not wearing our seat belts like we should be? Are we taking risks that we shouldn’t be? When the “big one” happens at our airport and its game on, are we going to perform like we did during practice drills? Will the result of our efforts be completed safely or haphazardly?
A few weeks ago we had our triennial MCI drill here at Salt Lake City International Airport. I was driving our newest ARFF truck which is about six years old. While responding from the station to the exercise site I experienced an issue where I was not able to get my truck to slow down due to the speed I was going when I began to brake which resulted in me being unable to make the final turn in to the exercise area due to overheated brakes. If I would have tried to make the turn instead of passing the entrance to the site and backing up, I would have possibly been involved in a rollover accident myself.
While conducting research and gathering information for a presentation I previously worked on regarding ARFF truck rollover prevention I came across a couple of real ARFF truck rollover accidents that were discussed. In a document published in August 1999 titled “Aircraft Rescue and Fire Fighting (ARFF) Vehicle Stability Study,” by Captain William Wekenborg of the Dallas Fort Worth International Airport. Captain William Wekenborg drew some very important conclusions; this study and analysis of accidents states, “The typical ARFF vehicle rollover accident occurs in a non-emergency situation, on dry pavement, while being operated by experienced firefighters with a minimum of four years of experience as a driver-operator who have completed a basic driver operator training program.” The first accident happened when an Oshkosh T-3000 left the station on an actual declared emergency response run, the driver exited the station, accelerated and traveled approximately 85 feet straight out of the firehouse. The vehicle then made close to a 90-degree right-hand turn onto a roadway at which point the vehicle drove straight for approximately 75 to 85 feet. The vehicle is then described as making another almost 90-degree left-hand turn onto a roadway where it then rolled over. The last turn had a measured radius of 86 feet. It is estimated that the vehicle was traveling more than 17 mph when it made this final left-hand turn. The combination of these left and right turns and running over the taxiway light caused the instability situation, which resulted in the rollover, and substantial damage to the vehicle. Therefore, the vehicle did not arrive at the scene, which in itself, created another emergency.
During my research I came across another accident that was reported as a low-speed rollover that occurred with an Oshkosh T-3000. In this particular accident, the driver was performing a routine airport visitation tour of the airfield. The driver reported that he made a slow left-hand turn, under 20 mph while turning the wheel and applying the brakes at the same time. The driver reported the vehicle pitched over into a rollover situation before he realized that he had a vehicle problem.
In both of the aforementioned accidents, as well as many of the more recent rollover accidents, the vehicles were not reported to be traveling at a high rate of speed. In several interviews, the drivers reported that the vehicles were going below 25 mph. The vehicles were in the radius of a moderate turn when the brakes were applied. Shortly after the brakes were applied the vehicle proceeded to roll around the rear axles. In each case, the drivers said there was no warning preceding the event. In fact, the back end appeared to snap or pitch into the rollover and occurred before they realized that they had a problem. Even though these two accidents happened with older ARFF trucks, the same accident can happen with a new ARFF truck. An experiment with 28 individuals, with various driving experience, was conducted. During the experiment the view of the speedometer was blocked. The drivers were asked to drive the vehicle at 20 miles per hour. When the drivers indicated they had accelerated to 20 miles per hour, the cover was removed from the speedometer. The speeds at which the vehicles were traveling ranged from 28 to 42 mph, with the average speed being 29.3 mph. This study indicates that drivers have trouble determining their vehicle speed. Drivers are generally looking out around the airport surface and are not particularly observing the speedometer. They are very aware of the latent dangers of driving on an airport. The current generation of heavy rescue vehicles places the large capacity water tank on top of the vehicle chassis frame. This situation results in rescue vehicles with centers of gravity (C.G) of 5 to 6 feet off the ground. Vehicles with high centers of gravity do not exhibit good dynamic stability. As a vehicle commences into a turn, a large shift of the water content can occur. This weight shift moves toward the outside of the turning radius. Vehicle operators who were questioned in recent rollover accidents stated that they felt a rapid shift of water movement just prior to realizing that they were losing control of the vehicle. Today’s ARFF trucks are built better and are much safer to drive and operate than their predecessors were, however we still have ARFF truck operator error to factor in. In the majority of cases driver error or the speed in which a driver is going is too fast.
As aircraft rescue fire fighters, we should all know the definitions of these two words; Centrifugal Force and Inertia.
Centrifugal Force is the apparent force that draws a rotating body away from the center of rotation. It is caused by the inertia of the body.
Inertia is the resistance of any physical object to change in its state of motion, including changes to its speed and direction. It is the tendency of objects to keep moving in a straight line at constant velocity.
Bottom line, a fully loaded ARFF truck is heavy and will want to keep going in a straight direction instead of turning. The faster the truck is going the harder it’s going to be to steer that truck into a turn.
Here are 16 sweet things to keep in mind that will help you stay safe when you are driving an ARFF truck.
- Know the characteristics of the ARFF Truck
- Anticipate stops
- Allow the engine to act as brake
- Down shift if necessary
- Be consistent, smooth and controlled
- Understand height and weight restrictions
- High center of gravity, six feet above ground
- Mass of water in motion = 25,000 + pounds
- Partially empty water or foam tanks increase vehicle instability due to sloshing
- Reduced braking ability due to weight
- All wheel independent suspension will cause apparatus to dip in direction of turn
- Do not brake while turning except at very low speeds, under 10 MPH
- Take turns slowly, do not attempt to estimate your speed, check the speedometer before making the turn
- Remember mass in motion will continue to move in the same direction
- When responding to emergencies, accelerate while straight, brake and downshift before going into a turn or curve
- When downshifting maintain engine speed in power range of 1600 to 2100 RPM
My hope is that if you get anything out of this article, it should be that NO ONE should overlook the importance of driver’s training to operate an ARFF crash truck. It is critical that those of us operating any ARFF vehicle be familiar with the capabilities of our vehicle, receive proper training and that we practice frequently.
NFPA 414 contains advisory information about characteristics of specialized suspensions and tires that are the most appropriate for the physical characteristics of the airport, and safety precautions regarding overloading ARFF vehicles. During some down time at your station make it a priority to read up on NFPA 414 Standard for Aircraft Rescue and Fire Fighting Vehicles, and NFPA 1002 Chapter 9 Aircraft Rescue and Fire Fighting Apparatus. There is an abundance of valuable information to be gathered out of these two references.
As ARFF truck operators we must do our part to keep US safe. Check your tire pressures and crawl under your rig to check your suspension springs and brake lines for wear and tear. If the ARFF truck you drive is more than 10 years old I would suggest doing these checks bimonthly.
In closing remember the majority of all ARFF truck rollovers are caused by driving too fast so let’s slow it down and no matter what, make sure to buckle up.
About the Author: Algernon “Al” Hoskins, ARFF, AMF, served as an Air Force Firefighter for 24 years prior to joining the Salt Lake City Fire Department in 2000. In addition to his position as an aircraft rescue firefighter at Salt Lake City International Airport, Al is also a Lead Instructor at the Salt Lake City ARFF Training Center where he has been educating ARFF personnel from around the world since 2006.