10-foot lower structure, a variable height upper structure, and a manual pump actuated hydraulic system for raising and lowering the upper structure. The upper structure includes a work platform with guardrails and steps with handrails. The lower structure includes fixed steps and handrails, a towbar, and four free-swivel caster wheels with safety locking devices, four immobilizing jacks, and a hydraulic pump, lines, and reservoir. The height range for the B-2 work platform is from 13 feet to 20 feet, and it has a weight bearing capacity of 600 pounds. B-4 MAINTENANCE PLATFORM.—The B-4 maintenance platform (fig. 9-30) is a moveable, hydraulically operated, adjustable platform with a ladder assembly. Four free-swivel caster wheels, each having a foot-lever actuated mechanical brake and swivel lock mechanism, are included. The platform is equipped with safety guardrails, handrails for the ladder, two safety lock pins, which are inserted into the frame to lock the extension scissors of the platform. A hydraulic hand pump with reservoir is provided for raising and lowering the platform. The adjustable height range for the B-4 work platform is from 3 to 7 feet and a weight bearing capacity of 600 pounds. Q9-1. What are the two types of support equipment? Q9-2. The primary function of the A/S32A-30 tow tractor is to tow what aircraft or equipment? Q9-3. What tow tractor is designed for towing air- craft aboard ship? Q9-4. What type of tow tractor is designed to tow, turn, and position aircraft within the confines of an aircraft carrier hangar deck and is often called "The Spotting Dolly"? Q9-5. What aircraft crash handling and salvage crane is used on amphibious assault ships? Q9-6.  Aboard ship, what is the primary fire-fighting and rescue vehicle? Q9-7.  What fire-fighting agents are contained in the twinned agent unit (TAU-2H)? Q9-8.  What activity is tasked with maintenance of forklifts aboard naval stations? Q9-9. What mobile electric power plant is designed primarily for use on aircraft carriers? Q9-10. What type of motor propels the NC-8A mobile electric power plant? Q9-11.  What is the danger associated with operating the NC-8A or NC-10C when aircraft are serviced? Q9-12. The A/M47A-4 jet aircraft start unit provides what support for starting aircraft? Q9-13. What are some of the dangers associated with operating a jet aircraft start unit? Q9-14. The A/M27T-5 is used to service what aircraft system? Q9-15. How many nitrogen gas cylinders are mounted on the A/M26U-4 (NAN-4) servicing unit? Q9-16. What are the major components on the TMU 70/M oxygen storage tank? Q9-17. What is the purpose of having mobile air- conditioning units? Q9-18. What type of aircraft jack is used to raise the entire aircraft off the deck? Q9-19. What is the weight bearing capacity of the B-4 maintenance platform? MAINTENANCE REQUIREMENTS LEARNING OBJECTIVE: Identify the purpose for support equipment preoperational maintenance and the requirements for support equipment training, licensing, and misuse/ abuse. You, as an Airman Apprentice, are not responsible for maintaining support equipment, unless you are striking for Aviation Support Equipment Technician. You will, however, be required to operate support 9-18 SAFETY RAILS LOCK PINS PARKING BRAKES ANF0930 Figure 9-30.—B-4 maintenance platform.