Progress Test 1 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 can AC be produced from DC in emergency?
Operating an INVERTER or STATIC INVERTER from DC BATTERY
What are the requirements before AC generators are connected in parallel?
OUTPUT VOLTAGE, FREQUENCY, and PHASE ROTATION of ALL GENERATORS are SAME
Why are emergency lighting systems required?
What is the requirement of it?
During TOTAL POWER FAILURE or EMERGENCY EVACUATIONS;
Must be ARMED and AUTOMATICALLY activated after FAILURE of PRIMARY LIGHTING POWER
What is the purpose of a CSD?
Why do we need this?
CONSTANT SPEED DRIVE;
To keep the ALTERNATOR 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 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 compartment
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 is the outflow valve controlled?
What values is it trying to achieve?
Through the PRESSURE CONTROLLER either MANUALLY or AUTOMATICALLY to maintain CORRECT pressure under NORMAL conditions;
A DIFFERENTIAL of 8.9PSI
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
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
What are the 2 types of oxygen systems?
Describe the features of each one? (3,5)
CONTINUOUS FLOW: SIMPLEST; AUTOMATICALLY ACTUATED; Oxygen IMMEDIATE and CONTINUOUS; PRESSURE DEMAND: Has DILUTER DEMAND REGULATOR which operates due to the SUCTION from BREATHING and AUTOMATICALLY DILUTES with suitable amounts of ATMOSPHERIC AIR; PROLONGS OXYGEN supply; Can be SELECTED to 100% in case of SMOKE or other CONTAMINANT; DILUTION LIMITED to 34000ft
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
How are large aircraft protected from fire?
OVERHEAT, SMOKE and FIRE PROTECTION systems;
Fire PROTECTION includes fire DETECTION and EXTINGUISHING systems
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
What makes the halogenated hydrocarbon agent desirable?
LOW TOXICITY; Effective with LOWER CONCENTRATIONS (2% compared to 40% CO2); EFFECTIVE on all 3 TYPE FIRES; Can be USED in PERSONNEL COMPARTMENTS; NO RESIDUE after use
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 operation of a pneumatic fire detection system?
Is it a single-use system?
Contains various SENSOR TUBES and choice of ALARM TEMPS;
TUBE contains GAS which EXPANDS greatly when HEATED;
When trigger TEMP is reached PRESSURE overcomes CHECK VALVE and gas flow to RIGHT of DIAPHRAGM;
This forces DIAPHRAGM CONTACTS LEFT onto ALARM CONTACTS energising the CIRCUIT;
If HEAT is REMOVED and PRESSURE is DECREASED DIAPHRAGM forces GAS into TUBE effectively RESETTING it
What is the operation of a flame detector system?
Uses INFRARED detectors to RECEIVE DIRECT or REFLECTED RAYS from flame;
LOCATED in ENGINE NACELLE;
Send SIGNAL to AMPLIFIER which POWERS an ALARM CIRCUIT in cockpit
`What is the operation of a smoke detector system?
Uses PHOTOELECTRIC CELLS with LIGHT directed towards them;
If sufficient SMOKE is present the REFERENCE BEAM REFRACTS light to PHOTOELECTRIC CELLS and ALARM is POWERED
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
What is the problem when aircraft are fitted with split controls?
If AIRSPEED LOCKOUT system FAILS:
LOW-SPEED surfaces ENGAGED, after ACCELERATION to CRUISE speed there is TOO MUCH CONTROL authority must AVOID LARGE INPUT;
LOW-SPEED surfaces ENGAGED, after SLOWING there is LESS CONTROL authority must have LARGE INPUT;
How are failures of the lockout system advised?
What should the crew do if an advisory is given?
RUDDER RATIO;
ALL LOCK;
Refer to FLIGHT MANUAL for actions
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
What is the consideration of controls for swept wings?
Primary: SPLIT CONTROLS and MULTIPLE control SURFACES;
Secondary: Employ flying TAILPLANES and ALL MOVING WINGTIPS/TAILFINS
What is the purpose of high lift devices?
When are they used?
What are some common examples?
CHANGE LIFT characteristics which REDUCE TAKEOFF and LANDING SPEED;
Only at LOW SPEEDS;
SLOT, SLAT, FLAP, LE/TE FOWLER FLAP
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 is built in to make STICK FORCE PROPORTIONAL to FLIGHT LOADS
What do position transducers do?
What is the operation of position transducers?
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 are the main components of the auto land system?
AUTOPILOT; AUTOTHRUST; RADIO ALTIMETER; NOSE WHEEL STEERING; Not integral but ATOBRAKE
What are the limitations of autoland when doing a CAT I or CAT II/III approach?
CAT I: May NOT be suitable due to OFFSET LOCALISER or LOCALISER/GLIDESLOPE UNSTABLE SIGNALS;
CAT II/III: Cautious when LOW VISIBILITY procedures NOT in effect as LOCALISER/GLIDESLOPE signals compromised by traffic. Advise ATC for assistance
What are the characteristics of a fail operational system?
ATLEAST 2 AP engaged;
Failure of 1 AP allows LANDING to CONTINUE;
No DECISION HEIGHT
What are the characteristics of a fail passive system?
ATLEAST 1 AP;
Failure of AP will NOT cause immediate DEVIATION from PATH but PILOT must take CONTROL and UNLESS VISUAL conduct MISSED APPROACH;
50ft DECISION ALTITUDE
What are the 2 categories of AFDS faults leading to non normal operations?
Faults ABOVE ALERT HEIGHT;
Faults AT or BELOW ALERT HEIGHT
How does the sensitivity of the auto land change throughout the approach?
GLIDESLOPE sensitivity REDUCED at 300ft radio altimeter;
RUDDER/AILERON used to keep on CENTRELINE from 200ft RA;
ANGLE of ATTACK protection INHIBITED at 100ft RA for FLARE;
PITCH TRIM wound back to give ELEVATOR POWER for FLARE if AP disengaged here, 40lb of forward FORCE is REQUIRED to counter TRIM;
GA MODE INHIBITED at 5ft RA
What is the relationship between auto pilot and auto trim?
CAN fly WITH AP and WITHOUT AUTO TRIM;
CANNOT fly WITH AUTO TRIM and WITHOUT AP
What is the source air for cabin pressurisation?
BLEED AIR
