SAFETY WARNING
WITHDRAWAL FROM SERVICE
of the FUEL PRESSURE SWITCH type GL502
The AVcomm Developments Ltd. GL501 Warning system was designed to allow PFA
members to comply with the mandatory, Low Voltage ,Starter Motor engaged
warnings , plus either a Low Fuel or Low Fuel Pressure warning.
Low Fuel Pressure is detected by the GL502 Pressure Switch fitted between the
electric fuel pump and the engine. Empirical evidence has indicated that the
full life of the unit as derived from accelerated life tests may not be
reached in some cases. This is highlighted in two problem areas. The first
is that it has proven to be very difficult to source a reliable pressure
sensor to work at the low pressures in the fuel line, resulting in the Low
Pressure Warning Light sometimes remaining ON. The second is potentially much
more serious, in that additives in certain fuels can corrode the sensor
allowing fuel to contaminate the switch rendering it's operation
unpredictable and in some early models this can cause a degradation of the
sealant. This has resulted in one instance of a fuel leak whilst airborne.
Because of the above problems, and the ongoing difficulty of producing a safe
cost effective Pressure Switch which can be used with any fuel likely to be
encountered in PFA aircraft, AVcomm Developments Ltd., in conjunction with
RD Aviation Ltd., have decided to cease production of the GL502 switch and
recall all that have been sold.
The mandatory functions of Low Voltage and Starter Engaged warning are still
available through the GL501 Control Unit and it is recommended that the GL502
Fuel Pressure switch be removed from the fuel system and the sensor wire
shorted to earth. The GL502 switch should be returned to RD Aviation Ltd.,
who will, on receipt of the unit, refund the price of the GL502, less any
discount applied on purchase.
The logic of the 2 pins on the GL501 Control Unit which are connected to the
GL502 Fuel Pressure Switch is:- closed circuit - light OFF, open circuit -
light ON. This circuit can be utilised for any other warning function.
AVcomm Developments Ltd. and RD Aviation Ltd. regret the inconvenience caused,
but trust that customers will accept that Flight Safety must be the prime
consideration.
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