If a tractor has a drawbar pull of 8,500
pounds, what is the maximum aircraft weight
it can tow?
Which of the following tractors is also called
a "spotting dolly"?
JET AIRCRAFT START UNITS
Figure 1-17.--A/S32A-42 aircraft towing tractor.
The aircraft start unit is designed to provide air
A/S32A-42 Tow Tractor
for starting aircraft jet engines. The two types of
air start units discussed are trailer-mounted and
The A/S32A-42 tow tractor (fig. 1-17) is designed
for towing shore-based aircraft weighing up to 100,000
pounds. It has a 4-cylinder diesel engine, 3-speed
A/M47A-4 Trailer-Mounted Jet Aircraft Start Unit
automatic transmission, hydraulically actuated front
disc brakes, drum rear brakes, and front wheel power-
The A/M47A-4 jet aircraft start unit (fig. 1-19) is a
trailer-mounted gas turbine air compressor used to
provide air and electrical power for starting jet engines.
A/S32A-32 Tow Tractor
The start unit requires manual start, stop, and air
selection. It provides air at 5:1 or 3.6:1 air pressure
The A/S32A-32 tow tractor (fig. 1-18) is more
ratios and by way of a 30 kVA, 400-Hz generator,
commonly referred to as a "spotting dolly." It is
provides 115/208 volts of ac and 28 volts of dc for
designed to tow, turn, and position aircraft within the
operating aircraft electrical systems.
confines of a ship's hangar deck. It has a 3-cylinder
Detroit diesel engine that drives two main hydraulic
pumps. Although a single joystick controls it, each
wheel can rotate independently, which enables the
tractor to pivot around its center with a minimal turning
radius. It has a drawbar pull of 14,000 pounds and a lift
capability of 16,000 pounds.
Figure 1-19.--A/M47A-4 trailer-mounted jet aircraft start
Figure 1-18.--A/S32A-32 aircraft towing tractor.