Section 7 - Airframe and Systems description - 19 - Electrical System

Question 1

How is primary DC power provided?

Answer 1

By two engine-driven generators which, during normal operations, operate in parallel.

Question 2

How’s each generator rated?

Answer 2

Each generator is rated of 40 Amps and 14 VDC, as the two voltage regulators.

Question 3

What protects the circuits and electric components? From what?

Answer 3

An automatic overvoltage device protects the circuits and the electric components from an excessive voltage caused by generator failures.

Question 4

What’s the power rating of each generator?

Answer 4

is such that if one generator fails the other one can still supply the airplane equipment to maintain flight safety.

Question 5

How’s secondary DC power provided?

Answer 5

by a main battery (lead type - 12 V, 23-Ah) and a secondary battery (lead type - 12 V, 13 Ah)

Question 6

What’s the external power source?

Answer 6

An external DC power source can be connected to the aircraft distribution system in order to have it fed without starting the engine.

Question 7

How’s current being supplied indicated?

Answer 7

The ammeter section of the G1000 EIS can indicate the current supplied by either left or right generator switching a dedicated selector.

Question 8

How many buses are there?

Answer 8

5

• Battery bus
• LH Generator bus
• RH Generator bus
• LH Avionics bus
• RH Avionics bus

Question 9

How does the distribution system operate?

Answer 9

As a single bus with power being supplied by the battery and both generators

Question 10

Is it possible to separate the left busses from the right busses? by what means?

Answer 10

Yes, it is possible to separate the left busses from the right busses when required by means of the Cross Bus switches.

Question 11

How are alternators and batteries enabled and disabled?

Answer 11

The switches to enable and disable the alternators and battery are grouped in the master switches group and are located in the centre side of the instrument panel.

Question 12

Can we put both batteries in parallel?

Answer 12

Only the emergency switch, that allow to put in parallel both batteries is located in left side of the instrument panel.

Question 13

How are all electrical loads divided?

Answer 13

among the five busses on the basis of their importance and required power: equipment with duplicate functions is connected to separate busses.

Question 14

What does the battery bus supply? How is it energized?

Answer 14

the most important loads, it is energized from three sources:

the battery and both generators

This allows the bus to remain active also in case of two independent faults in the supply paths.

Question 15

What loads are connected to the battery bus?

Answer 15

Breaker ID_____
Start LH__________
Start RM__________
Fan TAS (if installed)
Fuel Pump LH_____
Fuel Pump Rl I_____
Inslruin.
E.I.S. 1 E.I.S. 2 P.F.D.
C.PS/NAV I_______
COM 1
AHRS____________
Stall warning A.D.I.
ADC_____________
Flaps actuator______
Door_____________
Cabin Light_______
Landing light______
Strobe Light_______
Instr. Light________
Cross LH_________
| Cross RH_________
Pilot seat_________
Backup Battery_____
Landing Gear______
Relay Landing Gear Light Landing Gear

Question 16

What is also connected directly to the battery?

Answer 16

In addition, Emergency Light is connected directly on the battery.

Question 17

What’s connected to the Cross Bus LH?

Answer 17

Field LH
Taxi Light
Pitot Heat
Voltage regulator LH
Cabin fan

Question 18

What’s connected to the Cross Buss RH?

Answer 18

Field RH
Rudder Trim
Co-pilot seat
Voltage regulator RH
Nav Light
Audio panel
Landing Light

Question 19

What’s connected to the Avionic Bus LH?

Answer 19

Avionic bus LH
Trim A/P
A/P
XPDR
D.M.E.
Turn coord
TCAS (if installed)

Question 20

What’s connected to the Avionic Bus RH?

Answer 20

Avionic bus RH
COM2
M.F.D
A.D.F. (if installed)
GPS/NAV 2
Converter 12/28
12V socket

Question 21

What are the switches on the central pedestal?

Answer 21

seven switches disposed on two rows:

on the first row there is the MASTER SWITCH; which allows for connecting, through the battery relay, the battery to the battery bus.

LI I and RI1 FIELD switches control the pertinent generator: setting the switch to OFF puts the pertinent generator off-line.

In correspondence of the second row there are 4 switches LH/RH AVIONIC and LH/ RH CROSS BUS.

The first two switches allow, through a relay, to cut off the power supply to the pertinent avionic bus.

The second ones allow, through a relay, for realizing the parallel connection between the pertinent generator bus and the battery bus.

Setting these ones to OFF, the pertinent generator bus (and related avionic bus supplied) is separated from the battery bus and from opposite generator bus.

Question 22

What happens when both generators are correctly operating and all above mentioned switches are in ON position?

Answer 22

All the busses are connected to the generators.

Question 23

Where are the ignition switches grouped?

Answer 23

The ignition switches, two for each engine and grouped on the over head panel, are instead independent from the airplane electrical system (generation and distribution); they only control and open tire engine electrical circuit.

Question 24

Warning about ignition switches

Answer 24

If ignition switches are turned ON, a propeller movement can cause the engine starting with consequent hazard for people nearby.