Figure 3-1 JT15D-5B Engine Cross Section

CHAPTER THREE

STUDENT GUIDE FOR T-1A AIRCRAFT SYSTEMS

303. OVERVIEW

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

(Figure 3-1).

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

high-energy ignition unit which includes two igniter plugs used to start combustion. A

hydromechanical fuel control unit, supervised by an engine Electronic Fuel Control (EFC),

3-2

ENGINES