APU Flashcards
(22 cards)
WHat is APU’s FADEC called ?
The Electronic Control Box (ECB) is a full-authority digital electronic controller
What function does APU ECB perform ?
Performs the bulk of
the APU system logic for all modes of engine operation, such as :
- Sequences the start and monitors it.
- Monitors speed and temperature.
- Monitors bleed air.
- Sequences the shutdown.
- Controls the automatic shutdown
WHat are conditions for APU starter to engage ?
The starter engages if the air intake is fully open and the
MASTER SW and the START pushbutton are ON.
WHat is the power source of APU fuel pump ?
AC stat inv bus
What is IGV in APU ?
The IGVs control bleed air flow, and a fuel-pressure-powered actuator positions the IGVs.
The ECB controls the actuator in response to aircraft demand.
What is the APU speed for electrical demand and what is the APU load for bleed demand ?
The ECB always sets the APU speed to 100 % except for air conditioning demand, if the ambient temperature is between -18 °C and 35 °C. In this case, the ECB sets the APU speed to 99 %.
For all other ambient temperatures (less than -18 °C or more than 35 °C), the ECB sets the APU speed to
100 %
How the flight crew do an emergency shutdown of APU ?
. For emergency shutdown :
- the flight crew can push the APU FIRE handle, or
- the ground crew can push the APU SHUT OFF pushbutton on the interphone panel under the nose fuselage.
WHat happens incase of APU fire on groudnd ?
. In case of fire in
the APU compartment :
- APU fire warnings operate in the cockpit.
- A horn in the nose gear bay sounds.
- The AVAIL light goes out.
- The FAULT light in the MASTER SW lights up.
- The APU shuts down.
- The APU fire extinguisher discharges
WHen you put the APU master sw on, what are the list of things that happen ?
Starting sequence:
- Electric power goes to the APU system; the ECB performs a power-up test
- The APU air intake flap opens
- The APU fuel isolation valve opens
- If no fuel tank pump is running, the APU fuel pump operates
- If the aircraft has ground power or main generator power, the APU page appears on
the ECAM display
When APU is shutdown with the MASTER sw pb, how many minutes or seconds will the APU continue to run , and why ?
If the aircraft was using APU bleed air, the APU keeps running for a cooling period of
60 to 120 s
WHat is the difference between automatic shutdown and EMER shutdown ?
EMER shutdown in case of fire on ground , or APU SHUT OFF pb pressed on external power panel
EMER shutdown there is no cooling of 60 s to 120 s
When does the APU FAULT light illuminate?
APU AUTOSHUT down or EMER Shutdown
List few reasons for which APU will do AUTO shutdown ?
- Air inlet flap closed
- Overspeed
- No acceleration
- EGT overtemperature
-Low oil pressure - High oil temperature
- DC power lost (BAT OFF when aircraft on batteries only)
- ECB failure
As per FCOM how many reasons are there listed which willc ause APU autoshut down
22 reasons
After APU AUTO shutdown , can APU be restrated again ?
Yes 3 start , after that 60 mins cooling
What happens when APU START pb is pressed ?
Regarding the start sequence:
- When the flap is completely open, the APU starter is energized
- 1.5 s after the starter is energized, the ignition turns ON
- When N = 60 %, the APU starter is de-energized, and the ignition turns OFF
- 2 s after N reaches 95 %, or when N is above 99.5 % the ON light on the START pb
goes out
- 10 s later, the APU page disappears from the ECAM display.
- The APU is started, and can supply bleed air and electrical power to the aircraft systems
- The AVAIL light comes on when N is above 95 %.
When does APU AVAIL light come on and what does it mean ?
- The APU is started, and can supply bleed air and electrical power to the aircraft systems
- The AVAIL light comes on when N is above 95 %.
What does FLAP OPEN mean on ECAM APU page ?
Displayed in green when APU air intake flap is fully open.
WHen does LOW OIL LEVEL appear on APU ECAM page
Advisory: Displayed if the ECB detects a low APU oil level when the aircraft is on the ground, and the
APU is not running
When n does MEMO show “ APU AVAIL “
APU AVAIL : This memo appears in green, when APU N is above 99.5 % or 2 s after N is above
95 %
WHen does APU EGT become amber ?
Displays APU EGT in green.
- Becomes amber when EGT ≥ EGT MAX -33 °C
When does APU EGT become RED ?
Becomes red when EGT ≥ EGT MAX (automatic shutdown begins)
