engine being started. In addition to the air supply,
external electrical power must be applied to the
called impingement starting. The number of air
outlets and the air pressure required for impinge-
aircraft before the engines can be started. The
ment starts vary with the size, weight, and design
function of the turbine impingement starting
parameters of the engine to be started. Refer to
system is to start and sustain engine rotation at
figures 6-9 and 6-10.
a speed at which the fuel-air mixture is satisfactory
Starting air is supplied by an external starting
for light-off. The system must also assist the
unit, and is controlled by an air shutoff valve in
engine to increase rpm until it is self-sustaining.
the external air supply unit. The shutoff valve is
electrically controlled by the applicable engine
starter switch through the start relay. The starting
Electrical starters are 28-volt dc series wound
motors, designed to provide high starting torque.
air is delivered through a flexible hose to the
Their use is limited to small engines because of
starting manifold connection. The air is then
ducted through the impingement manifold and
the high current drain on the electrical source
and their heavy weight. Electrical starters develop
directed onto the second-stage turbine blades.
A check valve in the starting manifold prevents
a lot of heat while cranking. Starter damage
from heat is prevented by observing maximum
loss of gases after the engine is started. The
cranking time and time intervals between start
external starting unit electrical connector must be
plugged into the receptacle corresponding to the
Figure 6-9.-Turbine impingement starting.