Erics final flyover

Question 1

What is the function of the electrical system on a large aircraft?
What are the differences between light and large aircraft electrical systems?

Answer 1

GENERATE, REGULATE and DISTRIBUTE electrical POWER;
MORE THAN 1 system for REDUNDANCY;
Normal CONFIG will have seperate AC CIRCUIT powered by ALTERNATOR fitted to each ENGINE and each CIRCUIT feeds specific BUS;
AC more COMMON as it is LIGHTER

Question 2

What are buses?
What is their purpose?
What type of buses are likely to be used

Answer 2

POWER is ROUTED to a common bar off which SEVERAL COMPONENTS or SERVICES can be powered;
This means systems can be PRIORITISED for the use of ESSENTIAL SERVICES in event of SUPPLY BREAKDOWN;
PARALLEL, SPLIT, or SPLIT-PARALLEL

Question 3

How is DC provided when AC is present?

Are they separated?

Answer 3

AC is RECTIFIED using FULL WAVE RECTIFIER;

DC has own BUS SYSTEM ISOLATING entirely from AC

Question 4

How can AC be produced from DC in emergency?

Answer 4

Operating an INVERTER or STATIC INVERTER from DC BATTERY

Question 5

What is the purpose of a CSD?

Why do we need this?

Answer 5

CONSTANT SPEED DRIVE;
To keep the AC GENERATOR at a CONSTANT SPEED and PRODUCE CONSTANT 400Hz +/-8Hz;
Frequency of power out of alternator is determined by ROTATION of ARMATURE which is DRIVEN by ENGINE that is VARIABLE usually between 7000-10000RPM so CSD is used

Question 6

What is the most commonly used CSD

Answer 6

HYDRO MECHANICAL device which uses MECHANICAL GOVERNORS

Question 7

What will happen to the CSD if an electrical fault occurs?

What about an overheating or mechanical problem?

Answer 7

Electrical fault: CIRCUIT BREAKERS;
Overheat/mechanical: ROTATION must be STOPPED FIRST through the use of a GUARDED SWITCH labelled “GEN DISC” activates a SOLENOID which pulls a DOG CLUTCH OPEN that BREAKS the DRIVE between GEARBOX and CSD. It CANNOT be RESET

Question 8

What does Boeing and Airbus call their respective CSDs?

Answer 8

Boeing: INTEGRATED DRIVE GENERATORS;
Airbus: INTEGRATED CONSTANT SPEED DRIVE`

Question 9

What are most modern constant frequency AC generating systems fit with?

Answer 9

ROTATING RECTIFIER, BRUSHLESS, AC GENERATORS

Question 10

How is an AC generator excited?
What is the power output of an AC generator usually?
WHat are they power rated to?

Answer 10

SELF, PILOT or EXTERNALLY;
115VAC, 400Hz 3 PHASE;
20-60kVA

Question 11

What is the advantage of having a 3 phase AC generator?

Does this come with any disadvantages?

Answer 11

INCREASES CURRENT AVAILABLE, therefore, POWER available;
Connection to PHASE sensitive equipment such as 3 PHASE MOTORS and TRANSFORMERS are CRITICAL;
INCORRECT PHASE sequence in MOTOR causes ROTATION in the OPPOSITE direction;
INCORRECT PHASE sequence in 3 PHASE MOTOR and TRANSFORMER in PARALLEL could cause BURN OUT`

Question 12

What is the purpose of the cabin air conditioning and pressurisation system?
What does this specifically cover?

Answer 12

TO provide a means of TEMPERATURE, HUMIDITY, and VENTILATION control;
PAX COMFORT;
AVOID CONDENSATION on AVIONICS equipment due to HEAT build up;
DOMESTIC ANIMAL COMFORT in CARGO

Question 13

What are the sub-sections of the passenger environment systems?
What is their collective purpose?

Answer 13

PRESSURISATION;
AIR CONDITIONING;
HEATING;
OXYGEN;
PRESSURE CELL;
Supply INHABITED areas with TEMP control and safe atmospheric PRESSURE/OXYGEN at ALTITUDE

Question 14

What is the definition of PD?

How is PD controlled throughout the flight?

Answer 14

DIFFERENCE in PRESSURE between INSIDE HULL and AMBIENT at ALTITUDE flying;
Will regulate PRESSURE to 8000ft due to HYPOXIA regardless of aircraft altitude so PD INCREASES with ALTITUDE;
PD is built up by controlling the OUTFLOW to be LESS than the INTAKE through AIRCON when OPTIMUM PD is achieved INFLOW = OUTFLOW;
The VERTICAL SPEED is also controlled by RATE CONTROLLER to ensure PAX COMFORT

Question 15

How does cabin altitude change?

How is the cabin altitude/vertical speed controlled?

Answer 15

As ALTITUDE INCREASES so does CABIN ALTITUDE but at a LOWER RATE, usually in 1000s of FT/MIN;
By OUTFLOW VALVE, controlled by CREW SETTINGS to maintain safe PSID

Question 16

What are the requirements of an air conditioning system?

Answer 16

PRESSURE CELL designed to WITHSTAND PD;
Can respond to RAPID CHANGES in AMBIENT PRESSURE/TEMP;
Air SUPPLY sufficient for cabin PRESSURISATION and AIR CONDITIONING

Question 17

What are the components of cooling units?

Answer 17

PRIMARY HEAT EXCHANGER;
SECONDARY HEAT EXCHANGER;
REFRIGERATION UNIT

Question 18

What is the purpose of primary/secondary heat exchangers and refrigeration unit?

Answer 18

PRIMARY: COOL COMPRESSED AIR bled directly from ENGINE COMPRESSOR to typical TEMP (300F);
SECONDARY: COOL AIR further so REFRIGERATION UNIT operate EFFICIENTLY;
REFRIGERATION: Provides AIR at TEMP appropriate for necessary CABIN COMFORT expected of AIRCON

Question 19

How is distribution achieved in environmental control?

Answer 19

Via DUCTS and DIFFUSERS

Question 20

What are the characteristics of duplicated environmental systems?
What will occur if one engine-driven system fails?
What will occur if both engine-driven systems fail?

Answer 20

Each system may FEED from ONE ENGINE;
Each system may feed to DIFFERENT AREAS ie: COCKPIT/AVIONICS BAY/ONE SIDE of CABIN and BAGGAGE COMPARTMENT/REST of CABIN;
Operation is still SATISFACTORY and often utilised in HIGH POWER conditions such as HIGH ALT RUNWAYS/HEAVY ICING/HEAVY TAKEOFFS;
Fresh air is provided through the ALTERNATE RAM AIR

Question 21

How much of the air is recycled in an environmental control system?
What is the purpose of recycling?

Answer 21

50% of CABIN AIR;

REDUCE LOAD on air DELIVERY system, especially when AIR is drawn from ENGINE COMPRESSORS

Question 22

What are the 3 positions that control the environmental system?
How may this differ in modern aircraft?

Answer 22

OFF, NORMAL, RAM;

Modern have panels where TEMPERATURE may be SET and INDICATED along with DIFFERENT temperatures in CABIN and COCKPIT

Question 23

What instrumentation is connected to the control of the environmental system?

Answer 23

Cabin PRESSURE CONTROLLER;
RATE SELECTOR;
LANDING ALTITUDE SELECTOR;
BAROMETRIC PRESSURE SELECTOR;
EMERGENCY CONTROLS;
WARNING LIGHTS;
APU

Question 24

What are the safety features of the pressurisation system?

Briefly describe each one?

Answer 24

PRESSURE RELIEF valve: AUTOMATICALLY ensures PRESSURE does NOT build up beyond MAX OPERATING PRESSURE;
NEGATIVE PRESSURE valve: AUTOMATICALLY ensures PRESSURE OUTSIDE CABIN NEVER EXCEEDS INSIDE;
EMERGENCY DEPRESSURISATION valve: Operated by WOW or COCKPIT CONTROL panel when there is EMERGENCY CABIN ALTITUDE control

Question 25

What are the components of the temperature control system?

Answer 25

``` CABIN TEMP controller; TEMP SELECTOR knob; TWO POSITION TEMP control SWITCH; MODULATING BYPASS VALVE; CONTROL NETWORK ```

Question 26

What happens when the temperature control system is switched to the "auto" position?

Answer 26

BYPASS VALVE seeks a VALVE GATE position so that DUCT TEMP equals TEMP CONTROLLER SETTING; CONTROL NETWORK sends SIGNALS from SENSING ELEMENT to CABIN TEMP CONTROLLER which then ELECTRICALLY positions VALVE

Question 27

What happens when the temperature control system is switched to the "man" position? What

Answer 27

CONTROLLER controls BYPASS VALVE DIRECTLY without reference to DUCT TEMP; Desired TEMP is maintained by MONITORING AIR TEMP KNOB as varying conditions alter CABIN TEMP

Question 28

What is the extended purpose of the primary heat exchanger? How is it cooled? How is it controlled?

Answer 28

REDUCES the TEMP of ENGINE BLEED AIR or SUPERCHARGER DISCHARGE AIR by routing it through VEINS in CORE of HEAT EXCHANGER; Cooled by RAM AIR; Controlled by primary heat exchanger BYPASS VALVE

Question 29

How does vapour cycling work?

Answer 29

Refrigerant ABSORBS HEAT from the CABIN and CHANGES STATE from LIQUID to GAS WITHOUT changing TEMPERATURE; HEAT is taken OUTSIDE of aircraft and given to OUTSIDE AIR then REFRIGERANT returns to LIQUID; CYCLE is CONTINUOUSLY REPEATED

Question 30

What is the most common material used as refrigerant? | What properties make it desirable?

Answer 30

``` DICHLORODIFLUOROMETHANE/REFRIGERANT-12; STABLE at HIGH and LOW TEMPERATURES; Does NOT REACT with MATERIALS of AIRCON; Does NOT ATTACK RUBBER HOSES or SEALS; COLOURLESS and ODOURLESS ```

Question 31

How much oxygen is usually carried by most transport aircraft?

Answer 31

Enough so that aircraft can DESCEND from CRUISE to 14000ft in LESS than 4 MINUTES WITHOUT EXHAUSTING OXYGEN supply

Question 32

What are the advantages and disadvantages of the chemical oxygen system compared to gaseous oxygen systems?

Answer 32

Advantages: LIGHTWEIGHT, LESS EQUIPMENT, LESS MAINTAINANCE; Disadvantages: FIRE HAZARD higher, NOT TAMPERPROOF, WON'T TURN OFF

Question 33

What are the arrangements of passenger oxygen system? | How and where is the oxygen supplied from?

Answer 33

SERIES of PLUG-IN supply SOCKETS fitted to CABIN WALL adjacent to seats which MASKS can be CONNECTED OR; DROP-OUT MASK arrangement which presents masks AUTOMATICALLY if PRESSURISATION FAILS; AUTOMATICALLY (BARO control VALVE) from MANIFOLD but can be OVERRIDDEN MANUALLY by CREW

Question 34

How much oxygen is in a standard solid-state oxygen system? | What are the comparative advantages of solid-state oxygen systems to liquid or gas?

Answer 34

120 CUBIC FT; MOST EFFICIENT SPACE wise; LESS EQUIPMENT and MAINATAINENCE; Only requires INTEGRITY INSPECTION until ACTUAL USE is implemented

Question 35

What are the most common fire and smoke detection systems?

Answer 35

SPOT TYPE; | CONTINUOUS LOOP/LIVE WIRE (more common)

Question 36

What is the principle of operation of the continous loop detection system? What is the advantage of it compared to spot type? What are the types of continuous loop?

Answer 36

OVER-HEAT system that has HEAT SENSITIVE UNITS which COMPLETE ELECTRICAL CIRCUITS at a specific TEMP; Permits more COMPLETE COVERAGE of FIRE hazard AREA; KIDDLE and FENWAL

Question 37

What fire extinguishing systems are found in the cockpit and cargo area? WHat si the principle of operation of the cargo extinguisher?

Answer 37

Cockpit: HANDHELD extinguisher; Cargo: FIXED REMOTE controlled system with 2 steps; INITIAL amount of AGENT sprayed, then sprayed SLOWLY to MAINTAIN amount of AGENT in compartment for 30 MINUTES or MORE depending on SIZE; CONTAINER DISCHARGES into LINE which sprays AGENT into compartment when EXTINGUISHER SWITCH is ACTIVATED

Question 38

What fire protection is used in the toilets of aircraft?

Answer 38

A EUTECTIC HEAD/SQUIB which MELTS at 70-75C allowing extinguishing agent to exit bottle

Question 39

What are the main extinguishing agents in aircraft?

Answer 39

WATER: COOLS fire and EXCLUDES OXYGEN NO ELECTRICAL fires; CO2: DISPLACES OXYGEN in atmosphere FOR ELECTRICAL fires; DRY CHEMICAL: SMOTHERS fire which EXCLUDES OXYGEN NO COCKPIT fires; HALOGENATED HYDROCARBONS: CHEMICALLY INTERFERES with COMBUSTION

Question 40

Where are smoke detectors usually positioned? | What are the classifications of smoke detector?

Answer 40

Where type of FIRE is anticipated to GENERATE SUBSTANTIAL SMOKE BEFORE TEMP CHANGES are sufficient to ACTUATE HEAT DETECTION system; Type I: Measurement of CO (CO detector); Type II: Measurement of LIGHT TRANSMISSIBILITY (PHOTOELECTRIC detector); Type III: VISUAL DETECTION by viewing AIR SAMPLES (VISUAL devices)

Question 41

What is the operation of a single wire thermal switch?

Answer 41

28V DC is applied to BOTH parts of THERMAL LOOP; If OVERHEAT occurs to the ALARM TEMP or FIRE occurs a SWITCH is CLOSED and GROUNDS the circuit completing it; This causes INDICATION to be displayed in COCKPIT

Question 42

If a fire is detected at one point by a single wire thermal loop how will the rest of the system respond?

Answer 42

Still provides PROTECTION at other SURVEILLANCE points

Question 43

What does the test switch do in a single wire thermal loop? What would a short in the circuit do? Is the operation of the system different at night?

Answer 43

TESTS ENTIRE LOOP, will show if there is OPEN CIRCUIT in POWER INPUT LEAD of LOOP; Causes a FALSE INDICATION; DIMMING RELAY provides LOW VOLTAGE to the LIGHT

Question 44

What is the principle of operation of the continuous loop system ie: Kidde/Fenwal? What is the difference between Kidde and Fenwal?

Answer 44

28V DC supplied to HOT LEAD through ALARM RELAY COIL; When COOL, CURRENT does NOT FLOW between GROUND and LEAD; When FIRE occurs, INSULATION MATERIAL HEATS and LOSES RESISTANCE sufficiently to COMPLETE PATH to GROUND; RELAY COIL ENERGISES by current and ALARM LIGHT illuminates in COCKPIT; Kidde: THERMISTOR INSULATOR 2 RODS; Fenwal: EUTECTIC SALT 1 ROD

Question 45

What determines the effectiveness of a primary control?

Answer 45

AERODYNAMIC FORCE generated for a given DEFLECTION; | MOMENT ARM from CoG

Question 46

How does control effectiveness change with low and high speeds? What effects can this have on the structure?

Answer 46

Low: Significantly LESS effective for a given DEFLECTION; High: May be so GREAT that with necessary FLEXIBILITY of structure the RESULTANT FORCE may TWIST WING about TORSIONAL AXIS

Question 47

How is torsional twisting at high speeds minimised? | What is the operation of this system?

Answer 47

PRIMARY CONTROLS are SPLIT; Operate in TANDEM at LOW SPEED; Use LOCKOUT system at HIGH SPEED which is AUTOMATICALLY ACTUATED by signals from ADC ie: only INBOARD sections used or FLAPERONS/ELEVONS

Question 48

What is the problem with a power-boosted control system?

Answer 48

During TRANSONIC FLIGHT, SHOCKWAVES form on CONTROL SURFACE which results in BUFFETING feeding a FORCE to CONTROL system; This FORCE does NOT reach the PILOT due to POWER operated IRREVERSIBLE control system

Question 49

How do the flight controls in the cockpit move the control surfaces? How can the pilot experience a feeling of the control surfaces?

Answer 49

ACTUATES control VALVES LOCATED by COCKPIT controls that directs HYDRAULIC FLUID to control surface ACTUATORS or POWER CONTROL UNITS; ARTIFICIAL FEEL/Q FEEL is built in to make STICK FORCE PROPORTIONAL to FLIGHT LOADS

Question 50

List what can be done when hydraulic power is lost in regards to power controls?

Answer 50

MANUAL DISCONNECT/REVERSION system; ELECTRICAL backup system; FUEL TRANSFER to ROLL and ENGINE POWER to TURN

Question 51

What do position transducers do? What is the operation of position transducers? What are the additional functions?

Answer 51

CONVERT CREW COMMAND INPUTS to analogue ELECTRICAL signals; Signals are CONVERTED to DIGITAL form and sent to PRIMARY FLIGHT COMPUTERS; Signals ANALYSED and if OUTSIDE ENVELOPE it can be MODIFIED; Can be operated via IFS providing AUTO FLIGHT control and FEED FLIGHT control POSITION DATA to FDR

Question 52

What is the operation of engine nacelle fire extinguishing with 1 bottle? Can it be controlled from cockpit?

Answer 52

BOTTLE is PRESSURISED to 500-600PSI; RELIEF VALVE is FUSIBLE DISK which RUPTURES if bottle OVERHEATS; To discharge from cockpit, ELECTRICAL CURRENT is applied to CONTACTOR which DENOTES EXPLOSIVE CARTRIDGE: This SHATTERS DISK in bottle OUTLET and AGENT flows to ENGINE; Can CROSSFEED if required

Question 53

What are the common extinguishing agents for gas turbine engines?

Answer 53

``` CO2 METHYL BROMIDE (CH3Br2) ```

Question 54

What is the principle of operation of the CSD? | Draw a diagram?

Answer 54

Input from ENGINE turns GEARS; FIXED DISPLACEMENT PUMP INCREASES/DECREASES PRESSURE changing OIL FLOW; OIL flows to CONTROL CYLINDER which is connected to the VARIABLE DISPLACEMENT PUMP which adds/takes away BRAKING on the GEARS connected to the GENRATOR OUTPUT and OIL PUMP driving CHARGE OIL; OIL also flows to GOVERNOR which acts to STABILISE PRESSURE; DIFFERENTIAL UNIT included