Description; Operation - De Havilland DASH8 100 Series Maintenance Manual

**ON A/C ALL
FUEL LOW PRESSURE WARNING − DESCRIPTION AND OPERATION
1. General
Two identical but separate fuel low pressure warning systems, monitor input fuel pressure to
the engine driven fuel pump for each engine. In the event fuel pressure falls below a pre−set
minimum pressure, the system activates caution lights.
2.

Description

Refer to Figure 1.
The fuel low pressure warning is provided by a fuel low pressure switch. The switch is
installed in a tapping in the fuel/filter housing, upstream of the engine driven fuel pump.
Each switch is connected to the appropriate ENG FUEL PRESS negative seeking caution
light circuit in the caution lights panel in the flight compartment.
For details of the caution lights system, refer to Chapter 33.
3.

Operation

Refer to Figure 2.
The switch is provided with one contact set. The switch mechanism is calibrated to operate
the contact from C to N.O. on increasing fuel delivery pressure of 7.5 + or − 0.8 psig and from
C to N.C. at 5.5 + or − 0.8 psig decreasing pressure.
The N.C. contact is connected to ground and the N.O. contact is an open circuit.
With fuel delivery pressure above 7.5 psig, the ground is removed and the associated caution
light goes out.
Should the fuel delivery pressure fall below 5.5 psig, the caution light logic circuit is connected
to ground and the caution light comes on.
MASTER
EFFECTIVITY: See Pageblock 73−31−00 page 1
D
S ERIES 100
AIRCRAFT MAINTENANCE MANUAL
73−31−00
Dec 20/2004
Page 1