STUDENT GUIDE FOR T-1A AIRCRAFT SYSTEMS
Two Pratt & Whitney JT15D-5B engines provide power for the T-1A. These engines are
lightweight, twin-spool, front turbo fan, and jet-propelled with full-length annular bypass ducts.
The design is comprised of low-pressure and high-pressure compressor stages. The low-pressure
compressor (N1), consists of a single fan stage and one core axial stage, and is driven by a two-
stage turbine. The high-pressure centrifugal compressor (N2) is driven by a single stage turbine
N1 is the measure of low-pressure compressor speed.
N2 is the measure of high-pressure compressor speed.
An accessory gearbox is installed on the lower side of the engine and driven by a tower shaft
from the bevel gear to the outer turbine shaft (N2). The tower shaft turns the engine during
starting and is also used to drive the accessories for the engine and aircraft systems following a
successful start and during flight (Figure 3-1).
Figure 3-1 JT15D-5B Engine Cross Section
The annular reverse-flow combustion chamber is supplied with fuel by 12 nozzles and contains a
hydromechanical fuel control unit, supervised by an engine Electronic Fuel Control (EFC),