Safety Precautions
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Do not use this or any electrical device near uncontained fuel or fuel vapors.
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Use in a well-ventilated area.
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Do not use in a wet environment.
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Do not use in the presence of open fuel containers or if you detect fuel vapors.
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Disconnect GPU from aircraft when not in use.
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Do not leave unattended while in use.
Special Considerations for Experiment/Amateur-Built (E/AB) Aircraft
E/AB aircraft typically differ from certified aircraft in several important ways that affect providing electrical
power for ground operations:
●
E/A-B aircraft are generally smaller with less complex design and systems.
●
Certified aircraft are usually designed with a triggered external power receptacle that routes
electrical power directly to the airframe and/or engine while bypassing the battery. E/A-B
builders do not usually include an external power receptacle in their electrical wiring to reduce
expense.
●
Certified aircraft must conform to their type design. E/AB aircraft have no type design conformity
requirements and can differ significantly from one aircraft to another. Builders are free to design
and build the aircraft to suit their individual preferences.
To use a GPU, most E/AB aircraft will need to install the provided wiring kit to create an easily accessible
electrical connection to the aircraft’s main electrical bus.
External Power Wiring Techniques and Diagrams
Best practice for wiring an external power receptacle, whether for battery maintenance charging or
airframe power, is to wire to the battery contactor, NOT directly to the battery. There are two options as
to which side of the contactor for making the connection, each with trade-offs to consider:
1) CONTACTOR OUTPUT – Wiring to the output side of the battery contactor provides direct
access to the main bus for airframe power and bypasses the battery (unless the Battery Master
Switch is ON).
2) CONTACTOR INPUT – Wiring to the input side of the contactor provides direct access to the
battery and cannot energize the airframe (unless the Battery Master Switch in ON).
Option 1 is the most appropriate and preferred for GPU operations. It keeps the battery out of the power
circuit unless desired and deliberately enabled by turning the Battery Master switch ON.
Option 2 may be considered if the operator wants to provide an electrical connection for both the GPU
and a full-time maintenance type battery charger (e.g., BatteryMINDer
®
) from a single SB-50 plug. Option
2 also allows the GPU voltmeter to display no-load battery voltage when connected with the GPU power
OFF. Some users may find this useful to assess the battery’s state-of-charge.
Option 3, and the better approach if both GPU and maintenance charging are desired, is to install two
separate SB-50 plugs, one to the battery side of the contactor for full-time maintenance charging; and
another to the main bus side of the contactor for connecting a GPU for airframe power.
With E/AB aircraft it is ultimately the decision and at the sole discretion of the builder to evaluate the
trade-offs for how and where to install in the receptacle for GPU and/or battery charging in the aircraft.
The most common wiring scheme for external power receptacle is a shared connection for both battery
charging and GPU airframe power. See the wiring diagrams below.
3
Model M1435-EXP Manual P/N 752-790, Rev 20211029
