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lug.
(7) Install the engine cowlings. Refer to Section 71-10.
(8) Do a function test of the external power relay:
S Connect an 28 V DC external power supply to
the external power socket.
S Set the ALT/BAT switch to ON.
S The airplane voltmeter must show 28 V.
S Remove the external power supply.
S The airplane voltmeter must show 24 V.
S Set the ALT/BAT switch to OFF.
AIRCRAFT
DA 40 Series
AMM
Electrical Power
Doc # 6.02.01
Rev. 5 24-41-00 Page 1
20 Sep 2007
Section 24-41
External Power - TAE 125 Diesel Engine
1. General
The DA 40 has an external power socket located on the left side of the fuselage, near the relay
junction box. It is a standard 14 Volt DC power socket. When you connect external power to the
external power socket, the external power control relay is energized and the external power comes
on-line.
2. Description and Operation
Figure 1 shows a simple schematic diagram of the external power system. The external power system
has these components:
A. 14 Volt Socket
The 14 VDC power socket is located on the left side of the fuselage, near the relay junction box.
The socket has 3 pins:
) A large negative pin.
) A large positive pin.
) A small positive pin.
% A diode connected between the external power relay solenoid and the small positive pin (via a fuse)
% protects the system of reverse polarity.
% An overvoltage suppressor connected between the large negative pin and the fuse protects the
% system from overvoltage.
B. External Power Relay
The external power relay is located in the relay junction box mounted on the firewall. Heavy duty
cable connects the large positive pin to the input terminal of the relay. Another heavy duty cable
connects the large negative pin to a ground point.
% The small positive pin connects to the solenoid of the external power relay via the fuse and the
% diode.
AIRCRAFT
Electrical Power DA 40 Series
AMM
Page 2
20 Sep 2007 24-41-00 Doc # 6.02.01
Rev. 5
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% Figure 1: External Power System Schematic Diagram
AIRCRAFT
DA 40 Series
AMM
Electrical Power
Doc # 6.02.01
Rev. 5 24-41-00 Page 3
20 Sep 2007
3. Operation
When you connect a 12 to 14 V DC power supply to the external power socket these things happen:
) Current can flow from the small positive pin to the solenoid, the solenoid operates and closes the
relay.
) Current can flow from the large positive pin through the external power relay to the main bus
system.
) The large negative pin is connected to ground.
If the polarity of the power supply is incorrect, then the diode will prevent current from flowing through
the solenoid. The solenoid will not operate and current cannot flow through the external power relay
to the bus system.
% If a power supply with more than 16 V DC is connected to the external power socket, then the
% overvoltage suppressor shorts and causes the fuse to blow. The current cannot flow to the external
% power relay solenoid.
AIRCRAFT
Electrical Power DA 40 Series
AMM
Page 4
20 Sep 2007 24-41-00 Doc # 6.02.01
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AIRCRAFT
DA 40 Series
AMM
Electrical Power
Doc # 6.02.01
Rev. 5 24-41-00 Page 101
20 Sep 2007
Trouble-Shooting
1. General
The table below lists the defects you could have with the external power system. If you have the
trouble detailed in the Trouble column read across to the Possible Cause column. Then do the repair
given in the Repair column.
Trouble Possible Cause Repair
External power will not come
on line.
No external power. Make sure that the external
power plug is securely in the
socket.
Make sure that the external
power is operating correctly.
External power relay is
defective.
Do a test of the external power
relay, if necessary, replace the
external power relay.
% Overvoltage protection has
% been activated.
Replace the in-line fuse (2A).
AIRCRAFT
Electrical Power DA 40 Series
AMM
Page 102
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AIRCRAFT
DA 40 Series
AMM
Electrical Power
Doc # 6.02.01
Rev. 5 24-41-00 Page 201
20 Sep 2007
Maintenance Practices
1. General
This Section tells you how to remove/install the external power relay. Refer to the component
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钻石40系列AMM 1(127)
