Test and Evaluation of Rear-Wheel Steering for Aircraft Rescue and Firefighting Vehicles—Part 2

The Federal Aviation Administration (FAA) has an ongoing research program that evaluates new technologies for increasing postcrash fire survivability on aircraft and determines methods to increase the performance capabilities of aircraft rescue and firefighting (ARFF) vehicles. Excessive tire wear on hard surfaces is a concern on ARFF vehicles with more than four wheels. The FAA ARFF research program evaluated a six-wheeled ARFF vehicle with rear-wheel steering (RWS).

The objectives were to evaluate an ARFF vehicle for turning diameter, tire tread wear, and estimated tire life. A six-wheeled ARFF vehicle was used with a prototype RWS system that allowed comparisons with the RWS function disabled and enabled. Tests were conducted according to FAA Advisory Circular 150/5220-10C, which specifies turning diameter procedures. Tire tread wear was achieved by driving the test vehicle on a figure-eight course for 60 miles, which generated a faster and more aggressive tire tread wear than normal driving patterns. Tire tread depth was measured according to the tire manufacturer. The data from the tread wear results were used to calculate estimated tire life.

The results showed the ARFF vehicle with RWS decreased the turning diameter by 18.7% in the clockwise direction from 116.0 feet to 94.3 feet and 18.2% in the counter clockwise direction from 108.2 feet to 88.5 feet compared to vehicle operations without RWS. Without RWS, the rear tires wore the fastest by approximately 0.406 (13/32) inch over the 60 miles. With RWS, the middle tires wore the fastest by approximately 0.121 (4/32) inch over the 60 miles. The data from the tire tread wear tests were used to calculate the estimated tire life using linear regression calculations. RWS extended the estimated tire life by 1.9 to 2.6 times on the front tires and 7.9 to 9.0 times on the rear tires compared to vehicle operations without RWS enabled. However, the middle tires showed better tire life without RWS, 5.3 to 7.3 times that of tire life with RWS.

DOT/FAA/TC-TN12/34
Author: Nicholas Subbotin, Kris Cozart, and John Hawk]