New Hartford Crash Truck Tested
A newly designed crash truck, which was built by American-LaFrance for Hartford, Conn., was given a comprehensive test at the proving grounds of the builders on August 24. The unit is designed to give protection for the buildings at the Hartford Airport as well as serve as a crash truck.
The experience of the Army Air Force was largely drawn upon for the basic design, which emphasizes four factors:
- All wheel drive to permit off the runway operation in all types of weather.
- Low flotation pressure to facilitate maneuverability on soft ground.
- High performance characteristics.
- Sufficient equipment to permit handling a crash fire facilitating the rescue of the personnel.
In addition to the above requirements, there was also the problem of supplying adequate water for Class A fires such as might occur in buildings on the field or adjacent areas where the truck might also be called upon to render assistance. The pump, therefore, was designed to have a rating of 750 GPM at 120 pound discharge pressure so that credit for its fire protection value would be issued by the National Board of Fire Underwriters.
To provide a maximum of utility the pump is operated by a motor directly connected to the pump and entirely independent of the motor operating the vehicle. This makes it possible to get the turret gun and the hand foam lines into operation before the vehicle comes to a stop. This feature is essential for fast action at a crash fire. It also permits the vehicle to be moved should a shift in the wind direction occur that might endanger the vehicle while fighting the crash fire. This movement can be accomplished without shutting down the nozzles or hand lines.
Vehicle performance is assured by a 204 H.P. V12 engine and pumping performance is provided by a 170 H.P. V12 engine.
When operating at a crash fire the pump is operated at 300 pounds pressure.
The turret nozzle has a straight tip and discharges approximately 190 GPM per minute.
Two hand lines for foam application are provided, each line discharging 600 GPM. For this discharge each line requires 56 gallons of water per minute and 4 gallons of liquid foam.
The Air Corps have found from numerous tests that 90 seconds is the maximum time allowable for rescues if the personnel in the plane is to survive a fire. This time limit is established from the time the fire starts. For crash service it is. therefore, essential that this vehicle have high accelerating characteristics as well as high top speed and tests have shown ability to accelerate from a standing start to 50 miles per hour in 32 seconds. The top speed is 65 miles per hour.
The water tank carries 500 gallons of water and a liquid foam tank carries 50 gallons of foam.
In addition to the above, 300 pounds of carbon dioxide gas are carried on the vehicle in four 75-pound cylinders and are manifolded so that any combination of one to all can be discharged. A reel with 125 feet of carbon dioxide hose and a horn is also provided. Other miscellaneous equipment in the form of hand fire extinguishers, both foam and carbon dioxide are provided. The usual complement of ladders, axes, lanterns, are supplemented by first aid kits, gas masks and stretchers.
The gross vehicle weight with full equipment and five men is approximately 18,000 pounds.
In the test conducted by the builders, the purpose was to demonstrate ability to effect a rescue of personnel providing protection that would permit the entry of a rescue crew in the minimum possible time. An A26 bomber was used for the purpose of the test, so that the conditions would duplicate as closely as possible an actual service problem.
The ground around the bomber was first thoroughly wet down with water to minimize absorption of gasoline during the test. The conduct of the test was as follows:
The apparatus was stationed some distance away from the plane (several hundred feet) to allow a certain timelapse that usually occurs before the arrival of the apparatus at a crash. At a signal, the 200 gallons of gasoline was dumped on the ground, which covered an area approximately 30 feet in diameter at the center of the plane. Valves were opened in lines from the gasoline tanks and in the wings so that gasoline was flowing from the wing tanks throughout the test. The gasoline was ignited and burned for approximately 15 seconds before the arrival of the apparatus.
Illustrations herewith show the technique of attack used and the progress of extinguishment. In the first test, as shown, a blanket of foam had been laid doyvn affording adequate protection for a rescue crew in a time of 60 seconds from the start of the fire. This time Was a little longer than on previous tests due to a 15 second delay on the arrival of the apparatus due to faulty throttle connection.
The time for total extinguishment of the fire was 2 minutes 24 seconds, quantity of water used was 400 gallons, and the quantity of liquid foam used was 19.2 gallons.
At the request of some of the visiting officials, a second test was run changing the tip on the turret nozzle from a 5/8 straight bore tip to a spray type nozzle. All the test conditions were identical to the first test except for this change. The results of this test indicated that a spray type nozzle on the turret requires very careful use of the nozzle to avoid an excess of water being mixed with the foam.
In the first test, after a path had been blasted through the flaming gasoline by the turret nozzle, the nozzle was used for its heat absorbing qualities and mostly over-shot the plane.
In the second test the spray nozzle was directed mostly against the fuselage of the plane to cool, rather than to use the water discharge from the nozzle as an umbrella for its heat absorbing qualities. As a result of directing most of the stream against the fuselage, the foam under the plane had a tendency to break down in the presence of excess water, and several flash backs occurred. This lengthened out the time for total extinguishment to 3 minutes 45 seconds for this test; total water used was 700 gallons; total liquid foam used was 33 gallons.
In summing up the results of the test, it was shown that this one crash vehicle is adequate to accomplish the rescue of personnel in a plane. It should, however, in all cases be backed up by auxiliary equipment capable of exercising some cooling effect on the opposite side from the fuselage or cabin from which the crash truck is working and also to aid in final extinguishment of the fire.