Powerplant

Question 1

Describe N1

Answer 1

The N1 is called the low pressure spool, because it is comprised of low pressure compressor and turbine sections. The N1 is a “free spool”. It is driven simply by the airflow through the engine. The compressor is a single stage Fan that is just aft of the spinner. It is driven by the turbine section through a drive shaft. This Fan stage provides a majority of the engine thrust as it generates the bypass airflow. At the aft end of the N1 is the four stage low pressure turbine section. It can be viewed from behind the engine.

Question 2

Overview of the engines

Answer 2

The aircraft has two Rolls-Royce Trent 700 engines that supply power to the aircraft. The engines are turbofan engines that have: ‐ A high bypass ratio, ‐ A Full Authority Digital Engine Control (FADEC), ‐ A fuel system, ‐ An oil system, ‐ An air system, ‐ A thrust reverser system, ‐ An ignition system and a start system.

Question 3

The Engine has…

Answer 3

‐ Three compressor turbine assemblies: ‐ The Low Pressure (LP) compressor turbine assembly, ‐ The Intermediate Pressure (IP) compressor turbine assembly, ‐ The High Pressure (HP) compressor turbine assembly. Each turbine operates its associated compressor via a shaft. ‐ One accessory gearbox, ‐ One combustion chamber.

Question 4

Describe LP COMPRESSOR TURBINE ASSEMBLY

Answer 4

The LP compressor turbine assembly has: ‐ One LP compressor, referred to as the fan, ‐ One LP shaft, ‐ One LP turbine. The LP shaft connects the fan to the LP turbine. The LP compressor (fan) has a single stage, and the LP turbine has 6 stages. (ANY/ANZ, others have 4)

Question 5

Describe IP COMPRESSOR TURBINE ASSEMBLY

Answer 5

The IP compressor turbine assembly has: ‐ One IP compressor, ‐ One IP shaft, ‐ One IP turbine. The IP shaft connects the IP compressor to the IP turbine. The IP compressor has 8 stages, and the IP turbine has a single stage. To optimize and protect the operation of the engine at all power settings and in all flight conditions, the Variable Inlet Guide Vanes (VIGVs) and the Variable Stator Vanes (VSVs) regulate the quantity of air that flows through the IP compressor.

Question 6

Describe HP COMPRESSOR TURBINE ASSEMBLY

Answer 6

The HP compressor turbine assembly has: ‐ One HP compressor, ‐ One HP shaft, ‐ One HP turbine. The HP shaft connects the HP compressor to the HP turbine. The HP compressor has 6 stages, and the HP turbine has a single stage.

Question 7

Describe the COMBUSTION CHAMBER

Answer 7

The combustion chamber burns a mixture of fuel and HP air. The FADEC controls the fuel/air mixture in accordance with the position of the thrust lever and the aircraft operating conditions. The combustion chamber is an annular assembly with fuel nozzles and two igniters. The combustion chamber is between the HP compressor and the HP turbine.

Question 8

Describe the ACCESSORY GEAR BOX

Answer 8

The accessory gearbox drives various accessories with mechanical power via the HP shaft for the operation of the engine and the aircraft systems. The accessory gearbox of each engine operates: ‐ The oil feed pump that provides the oil system with oil. ‐ The main engine fuel pump that provides the combustion chamber with fuel. ‐ The engine-driven hydraulic pumps that pressurize the GREEN, the BLUE and the YELLOW hydraulic systems. ‐ The engine-driven generators that are the primary source of electrical power. ‐ The FADEC alternator that provides the FADEC with electrical power. ‐ The pneumatic starter that enables the engine start.

Question 9

Give an overview of the FADEC

Answer 9

Each powerplant has a FADEC (Full Authority Digital Engine Control) system. FADEC is a digital control system that performs complete engine management. FADEC has two-channel redundancy, with one channel active and one standby. If one channel fails, the other automatically takes control. The system has a magnetic alternator for an internal power source. FADEC is mounted on the fan case. The Engine Interface Unit (EIVMU/EIU) transmits the data it uses for engine management to the FADEC.

Question 10

When does an automatic reversion to rated N1 mode occurs?

Answer 10

‐ Engine P2 (Engine Inlet Total Pressure) and/or P5 (Engine Low Pressure Turbine Outlet Pressure) are not available, or

‐ Engine P2 is lower than ADIRS Pt.

Question 11

Describe Rated N1 mode

Answer 11

The FADEC will compute an EPR COMMAND, depending on the TLA, then convert it into a N1 COMMAND as a function of Mach. The rated N1 mode can also be manually-selected through the ENG N1 MODE pb-sw on the overhead panel.

Question 12

When does an automatic reversion to degraded rated N1 mode occurs?

Answer 12

An automatic reversion to degraded N1 mode occurs, when:

‐ Engine P2 (Engine Inlet Total Pressure) and ADIRS 1 + 2 Pt are not available, or

‐ Engine T2 (Engine Inlet Total Temperature) and ADIRS 1 + 2 Tt are not available, or

‐ Engine P0 (Engine Inlet Static Pressure) and ADIRS 1 + 2 Ps are not available.

Question 13

Describe Degraded N1 mode

Answer 13

The N1 is defined as a function of TLA and altitude and is limited by the FADEC to either the smaller of N1 max or N1 redline (if T2 is available), or N1 redline (if T2 is not available). The N1 DEGRADED MODE is an unrated N1 mode. The N1 rating limit, N1 TLA, and N1 max indications on ECAM E/WD are lost. In electrical emergency configuration, the EPR mode is lost on both engines, and each FADEC reverts to an degraded N1 mode

Question 14

Is it possible to return to EPR mode when N1 mode is active?

Answer 14

With the FADEC in either rated or degraded N1 mode, switching OFF the ENG N1 MODE pushbutton on the overhead panel will permit to return to the EPR mode, if the failure has disappeared and the aircraft is on ground.

Question 16

What is the ECB?

Answer 16

The Electronic Control Box (ECB) is a full authority digital electronic controller that performs the APU system logic for all modes of APU operation, including: Sequence and monitoring of the APU start, speed and temperature monitoring, bleed air monitoring, and shut-down sequence.

Question 17

When will the APU starter engage?

Answer 17

The starter engages if the air intake is fully open and the MASTER pb switch and the START pb switch are ON.

Question 18

From where does the APU consumes fuel?

Answer 18

The APU is supplied with fuel from one of three sources, depending on flight phase and fuel tank status.
The fuel can be supplied from the Engine 1 collector cells, the trim tank or the trim pipe.

Question 19

The APU fuel supply is shut off if:

Answer 19

:The APU MASTER pb switch is selected OFF, the APU FIRE pb is pushed, the APU shut off push button on the external interphone panel or fueling panel has been pushed, or if there is an automatic or emergency shutdown caused by a fault or a fire indication.

Question 20

What controls the APU Bleed valve? How does it work?

Answer 20

The ECB controls the APU Bleed valve. Bleed Air from the APU has priority over engine bleed air. If APU BLEED is set to ON, the bleed valve closes at 25,000 ft when climbing and reopens at 23,000 ft when descending.

Question 21

What happens when APU MASTER sw ON?

Answer 21

Electric power is supplied to the APU system. The ECB performs a power-up test, the APU air-intake flap opens and the APU fuel isolation valve and APU LP valve open.

Question 22

What happens when APU MASTER sw OFF if APU BLEED was selected?

Answer 22

If the APU BLEED was selected, the APU performs a cooling period of 85 seconds at 82 % speed. After an additional running period of 15 sec, the APU shuts down and the AVAIL light on the START pb sw is extinguished. As N goes below 7%, the air inlet flap closes automatically.