by René "Pacha" Birot (ROTW)

One of the ATR's particularities, whatever the model, is the starting in "HOTEL" mode. This starting type allows having the right engine running to idle with propeller stopped, and to use it as "APU" for starting the left engine or for various cabin uses.

So the aircraft is equipped with a brake for the right propeller; it operates on hydraulic pressure. Now, to get the hydraulic pressure, the aircraft must be supplied with alternating current. The alternating current is supplied from an alternator, which works only when ... the propeller turns (the propeller drives the alternator). There are also electrical ground power units, which supply the aircraft with direct current (DC) and alternating current (AC).
Note: in simulation, the alternator supplies alternating current when the conditioner level is set above 40%.

So the manufacturer foresaw a particular hydraulic pump, which operates on direct current. Its control is located on the lower control panel, to the left of the power levers. It supplies hydraulic pressure for 30 seconds (active since the version V5).

We are now going to operate this famous procedure well known by ATR pilots. We'll have to manipulate the lower control panel ("CONDITION" levers, HYD A pump) and the overhead panel. Possibly we'll have a quick look at the main instrument panel to check the warning panel. On the overhead panel, here are the zones necessary for this starting:

In this tutorial, starting will be made with only one electrical ground power unit, supplying the aircraft with DC. It is thus necessary to connect it (failure manager panel) and to make it supply the aircraft (overhead panel): the X-feed bar indicates that the current is distributed on both supply buses. These buses are normally independent, and supplied from the generator of every engine.

1-Set the "ENG START" button to "START A&B"

2- Setting of the "CONDITION" levers:
- Let the LH "CONDITION" lever on "Fuel So",
- Set the RH "CONDITION" lever to a value between 20% and 34% (below the "FTR" position),
- Actuate the "HYD A" pump.
The hydraulic pump supplies the blue circuit; the indication "Ready" lights for the propeller brake (PROP BRAKE) in a few seconds; it is the time necessary for hydraulic pressure to be established.
NOTE: You need the version V5 to have the switch "HYD A" active. In the previous version, you have to press the switch "AUX PUMP" ("HYD PUMP" panel).

3- Setting into service of the propeller brake:
- Lift the "PROP BRAKE" switch-guard (yellow and black striped),
- Rock the switch upward (that lights the "Prop BRK" indicator).

Engine 2 starting (propeller stopped) is ready.

4- Engine 2 starting:
- Actuate the engine 2 "FUEL" pump (1)
- Press the "START 2" button (2)

CAUTION: The engine 2, with propeller stopped, cannot supply alternating current. Do not stop the "Hydro A" pump.

5- Set the LH "CONDITION" lever (engine 1) on "AUTO" position. That will drive its alternator and supplies AC current for hydraulic pumps.

6- Engine 1 starting (propeller not stopped):
- Actuate the engine 1 "FUEL" pump (1)
- Press the "START 1" button (2),
- Set "ACW GEN 1" to ON (3),
- Set "ISOL AC" to OPEN (4),
- Set "BLUE PUMP" and "GREEN PUMP" to ON (5) (6).
NOTE: With version V4, you may set "AUX PUMP" to OFF.

Setting into service of the DC circuit:
- Set the switch "BAT" to ON (7),
- Press the "DC GEN 1" and "DC GEN 2" buttons (8) (9),
- Actuate the both DC buses (10) (11).
You may cut the electrical ground power unit (12).
CAUTION: Do not forget to have the electrical ground power unit disconnected before rolling-on.
Set the "ENG START" button to OFF (13).

7- Setting into service of the propellers:
- After removing the right "PROP BRAKE",
- Set the RH "CONDITION" lever to "AUTO" position.
- Both engines are driving alternators, and you can set "ACW GEN 2" to ON.

8- End of the starting:
- Fire detector loops set to "ON",
- Pitot heaters set to "ON",
- Check if warning panel is "clear",
- Disconnection of the electrical ground power unit.

Your airplane is ready to run; you have only to adjust the comfort for the passengers and ask the tower for clearance. De-icing management is to be made only in icy conditions or in altitude.

NOTE:
- If you cannot use an electrical ground power unit, you can start thanks to aircraft battery, but take care as it works only a few minutes.
- If you have an AC/DC electrical ground power unit, you don't need "HOTEL" mode.

And as you followed the procedure, a beautiful picture: