Erics final flyover Flashcards
What is the function of the electrical system on a large aircraft?
What are the differences between light and large aircraft electrical systems?
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
What are buses?
What is their purpose?
What type of buses are likely to be used
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
How is DC provided when AC is present?
Are they separated?
AC is RECTIFIED using FULL WAVE RECTIFIER;
DC has own BUS SYSTEM ISOLATING entirely from AC
How can AC be produced from DC in emergency?
Operating an INVERTER or STATIC INVERTER from DC BATTERY
What is the purpose of a CSD?
Why do we need this?
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
What is the most commonly used CSD
HYDRO MECHANICAL device which uses MECHANICAL GOVERNORS
What will happen to the CSD if an electrical fault occurs?
What about an overheating or mechanical problem?
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
What does Boeing and Airbus call their respective CSDs?
Boeing: INTEGRATED DRIVE GENERATORS;
Airbus: INTEGRATED CONSTANT SPEED DRIVE`
What are most modern constant frequency AC generating systems fit with?
ROTATING RECTIFIER, BRUSHLESS, AC GENERATORS
How is an AC generator excited?
What is the power output of an AC generator usually?
WHat are they power rated to?
SELF, PILOT or EXTERNALLY;
115VAC, 400Hz 3 PHASE;
20-60kVA
What is the advantage of having a 3 phase AC generator?
Does this come with any disadvantages?
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`
What is the purpose of the cabin air conditioning and pressurisation system?
What does this specifically cover?
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
What are the sub-sections of the passenger environment systems?
What is their collective purpose?
PRESSURISATION; AIR CONDITIONING; HEATING; OXYGEN; PRESSURE CELL; Supply INHABITED areas with TEMP control and safe atmospheric PRESSURE/OXYGEN at ALTITUDE
What is the definition of PD?
How is PD controlled throughout the flight?
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
How does cabin altitude change?
How is the cabin altitude/vertical speed controlled?
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
What are the requirements of an air conditioning system?
PRESSURE CELL designed to WITHSTAND PD;
Can respond to RAPID CHANGES in AMBIENT PRESSURE/TEMP;
Air SUPPLY sufficient for cabin PRESSURISATION and AIR CONDITIONING
What are the components of cooling units?
PRIMARY HEAT EXCHANGER;
SECONDARY HEAT EXCHANGER;
REFRIGERATION UNIT
What is the purpose of primary/secondary heat exchangers and refrigeration unit?
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
How is distribution achieved in environmental control?
Via DUCTS and DIFFUSERS
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?
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
How much of the air is recycled in an environmental control system?
What is the purpose of recycling?
50% of CABIN AIR;
REDUCE LOAD on air DELIVERY system, especially when AIR is drawn from ENGINE COMPRESSORS
What are the 3 positions that control the environmental system?
How may this differ in modern aircraft?
OFF, NORMAL, RAM;
Modern have panels where TEMPERATURE may be SET and INDICATED along with DIFFERENT temperatures in CABIN and COCKPIT
What instrumentation is connected to the control of the environmental system?
Cabin PRESSURE CONTROLLER; RATE SELECTOR; LANDING ALTITUDE SELECTOR; BAROMETRIC PRESSURE SELECTOR; EMERGENCY CONTROLS; WARNING LIGHTS; APU
What are the safety features of the pressurisation system?
Briefly describe each one?
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
What are the components of the temperature control system?
CABIN TEMP controller; TEMP SELECTOR knob; TWO POSITION TEMP control SWITCH; MODULATING BYPASS VALVE; CONTROL NETWORK
What happens when the temperature control system is switched to the “auto” position?
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
What happens when the temperature control system is switched to the “man” position?
What
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
What is the extended purpose of the primary heat exchanger?
How is it cooled?
How is it controlled?
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
How does vapour cycling work?
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
What is the most common material used as refrigerant?
What properties make it desirable?
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
How much oxygen is usually carried by most transport aircraft?
Enough so that aircraft can DESCEND from CRUISE to 14000ft in LESS than 4 MINUTES WITHOUT EXHAUSTING OXYGEN supply
What are the advantages and disadvantages of the chemical oxygen system compared to gaseous oxygen systems?
Advantages: LIGHTWEIGHT, LESS EQUIPMENT, LESS MAINTAINANCE;
Disadvantages: FIRE HAZARD higher, NOT TAMPERPROOF, WON’T TURN OFF
What are the arrangements of passenger oxygen system?
How and where is the oxygen supplied from?
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
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?
120 CUBIC FT;
MOST EFFICIENT SPACE wise;
LESS EQUIPMENT and MAINATAINENCE;
Only requires INTEGRITY INSPECTION until ACTUAL USE is implemented
What are the most common fire and smoke detection systems?
SPOT TYPE;
CONTINUOUS LOOP/LIVE WIRE (more common)
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?
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
What fire extinguishing systems are found in the cockpit and cargo area?
WHat si the principle of operation of the cargo extinguisher?
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
What fire protection is used in the toilets of aircraft?
A EUTECTIC HEAD/SQUIB which MELTS at 70-75C allowing extinguishing agent to exit bottle
What are the main extinguishing agents in aircraft?
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
Where are smoke detectors usually positioned?
What are the classifications of smoke detector?
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)
What is the operation of a single wire thermal switch?
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
If a fire is detected at one point by a single wire thermal loop how will the rest of the system respond?
Still provides PROTECTION at other SURVEILLANCE points
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?
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
What is the principle of operation of the continuous loop system ie: Kidde/Fenwal?
What is the difference between Kidde and Fenwal?
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
What determines the effectiveness of a primary control?
AERODYNAMIC FORCE generated for a given DEFLECTION;
MOMENT ARM from CoG
How does control effectiveness change with low and high speeds?
What effects can this have on the structure?
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
How is torsional twisting at high speeds minimised?
What is the operation of this system?
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
What is the problem with a power-boosted control system?
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
How do the flight controls in the cockpit move the control surfaces?
How can the pilot experience a feeling of the control surfaces?
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
List what can be done when hydraulic power is lost in regards to power controls?
MANUAL DISCONNECT/REVERSION system;
ELECTRICAL backup system;
FUEL TRANSFER to ROLL and ENGINE POWER to TURN
What do position transducers do?
What is the operation of position transducers?
What are the additional functions?
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
What is the operation of engine nacelle fire extinguishing with 1 bottle?
Can it be controlled from cockpit?
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
What are the common extinguishing agents for gas turbine engines?
CO2 METHYL BROMIDE (CH3Br2)
What is the principle of operation of the CSD?
Draw a diagram?
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
