Page 151 - The Jet Engine

Controls and instrumentation

oil pressures, the return oil being pressurized by pressure indicators are similar to those for
cooling and sealing air (Part 9) from the bearings. temperature and pressure indication.
40. In addition to a pressure gauge operated by a 42. On some engines, a fuel differential pressure
transmitter, an oil low pressure warning switch may switch, fitted to the low pressure fuel filter, senses the
be provided to indicate that a minimum pressure is pressure difference across the filter element. The
available for continued safe running of the engine. switch is connected to a warning lamp that provides
The switch is connected to a warning lamp in the indication of partial filter blockage, with the possibility
flight compartment and the lamp illuminates if the of fuel starvation.
pressure falls below an acceptable minimum. Fuel flow
43. Although the amount of fuel consumed during a
Fuel temperature and pressure given flight may vary slightly between engines of the
41. The temperature and pressure of the low same type, fuel flow does provide a useful indication
pressure fuel supply are electrically transmitted to of the satisfactory operation of the engine and of the
their respective indicators and these show if the low amount of fuel being consumed during the flight. A
pressure system is providing an adequate supply of typical system consists of a fuel flow transmitter,
fuel without cavitation and at a temperature to suit which is fitted into the low pressure fuel system, and
the operating conditions. The fuel temperature and an indicator, which shows the rate of fuel flow and the

Fig. 12-8 A typical double element thermocouple system.

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