Progress Test Flashcards
What is the problem with pressurising aircraft?
Each CYCLE of pressurisation causes STRETCHING of the FUSELAGE placing the structure under TENSION stress and the FASTENERS under SHEAR stress, followed by the DEPRESSURISATION returning the aircraft structure to normal
As an aircraft ages, why is its cabin pressure and operating heights reduced?
To alleviate TENSION stress levels
What are the other factors that lead to the degrading of aircraft fatigue life?
Manoeuvres OUTSIDE the aircrafts OPERATING ENVELOPE;
Flight through TURBULENT WEATHER;
HEAVY LANDINGS
What are the 4 types of gas turbine fuels?
TURBO FUEL A (AVTUR 40);
TURBO FUEL A-1 (AVTUR 50);
TURBO FUEL B (AVTAG or WIDE CUT);
TURBO FUEL 5
How are the gas turbine fuels A, A-1, and B identified?
A: Colourless or straw, 1 BLACK STRIPE on piping;
A-1: Colourless or straw, 2 GREY STRIPES on piping;
B: Colourless or straw, 3 YELLOW STRIPES on piping
How can it be determined what type of fuel an aircraft requires?
Stated in the FLIGHT MANUAL;
Stated and/or displayed as NATO SYMBOL on the LABEL near the FILLER CAP;
Stated in the TECH LOG;
Stated in the FUEL SHEET
What are the main characteristics of turbo fuel A?
Called “JET-A” or “CIVIL AVIATION KEROSENE”;
Essentially contains NO GASOLINE BLEND and is the PRIMARY fuel for COMMERCIAL and GENERAL AVIATION;
Generally NO MILITARY use
What are the main characteristics of turbo fuel A-1?
Called “JET A-1”;
LOW TEMPERATURE fuel with LOWER FREEZING POINT than JET A;
Used by most INTERNATIONAL AIRLINES
What are the characteristics of turbo fuel B?
Called “JET B”;
Blend of 30% KEROSENE and 70% GASOLINE, known as a WIDE CUT FUEL;
VERY LOW FREEZING POINT and LOW FLASH POINT;
Primarily used in MILITARY and SIMILAR to fuel JP-4
What are the characteristics of turbo fuel 5?
Called “JP-5”;
HIGH FLASH POINT military fuel;
Used primarily aboard NAVAL AIRCRAFT CARRIERS
What are the properties that gas turbine fuels should have?
Be PUMPABLE and FLOW EASILY under ALL operating CONDITIONS;
Permit ENGINE STARTING at ALL GROUND CONDITIONS and give SATISFACTORY flight RELIGHTING characteristics;
Give EFFICIENT COMBUSTION at ALL CONDITIONS;
Have as HIGH a CALORIFIC VALUE as possible;
Produce MINIMAL HARMFUL effects on COMBUSTION SYSTEM or TURBINE BLADES;
Produce MINIMAL CORROSIVE effects in the FUEL SYSTEM COMPONENTS;
Provide ADEQUATE LUBRICATION for the MOVING parts of the FUEL SYSTEM;
Reduce FIRE HAZARDS to a MINIMUM
What is the calorific value?
Why is it important?
An expression of the HEAT or ENERGY content PER POUND or GALLON that is RELEASED during COMBUSTION;
It INFLUENCES the RANGE of an aircraft
When the limiting factor of an aircraft is fuel capacity what should the calorific value be? Why?
The CALORIFIC VALUE PER UNIT VOLUME should be as HIGH as possible;
This means there is MORE ENERGY and therefore MORE RANGE, to be OBTAINED from a MINIMUM VOLUME of fuel
When the limiting factor of an aircraft is useful payload what should the calorific value be? Why?
The CALORIFIC VALUE PER UNIT WEIGHT should be as HIGH as possible;
This means there is MORE ENERGY and therefore MORE RANGE, to be OBTAINED from a MINIMUM WEIGHT of fuel
What other factors must be considered when choosing a calorific value in terms of volume or weight?
TYPE of aircraft;
DURATION of flight;
Required BALANCE between FUEL WEIGHT and PAYLOAD
Why do turbine fuels tend to corrode the components of the fuel and combustion systems?
Turbine fuels contain both SULPHUR and WATER contents;
When SULPHUR is BURNT in AIR it forms SULPHUR DIOXIDE;
When SULPHUR DIOXIDE is MIXED with WATER it forms SULPHUROUS ACID;
SULPHUROUS ACID is very CORROSIVE especially towards COPPER and LEAD
How is corrosion of the components of the fuel and combustion system minimised?
Why can it not be fully eliminated?
It is IMPRACTICABLE to completely REMOVE SULPHUR so it is REDUCED to a MINIMUM;
FREE WATER is REMOVED prior to use however DISSOLVED WATER CANNOT be effectively REMOVED as the fuel would REABSORB MOISTURE when stored in a VENTED storage TANK
What are the 3 types of fuel tanks used in large transport aircraft?
RIGID;
BLADDER;
INTEGRAL
What are the characteristics of rigid type tanks?
Requires an OPEN SPACE in the STRUCTURE for installation;
Usually made of ALUMINIUM ALLOY with WELDED JOINTS;
Sometimes can be COVERED with a SHOCK RESISTANCE RUBBER COATING which often has SELF SEALING capabilities
What are the characteristics of integral/wet wing tanks?
STRUCTURE is SEALED during construction enabling the COMPLETE STRUCTURE to BECOME the FUEL CELL;
Makes BEST USE of EMPTY SPACE within structure
What are the characteristics of bladder type tanks?
Made of THIN FABRIC, IMPREGNATED with NEOPRENE or some similar material that is IMPERVIOUS to FUEL;
May be SELF SEALING
What additional components are most tanks fitted with? Why?
BAFFLES;
INCREASE STRENGTH and REDUCE fuel SURGING during ALTITUDE CHANGES
Why may tanks be pressurised?
REDUCE VAPORISATION;
Provide a POSITIVE HEAD of FUEL to the SYSTEM PUMPS;
Do gravity fed tanks require an additional feature? Why?
VENTING system;
To ensure the tanks DO NOT suffer from CAVITATION
What are the characteristics and purpose of sumps and drains?
Usually LOCATED at the LOWEST POINT of each FUEL TANK;
Drain has a SEALING POPPET which, when DEPRESSED it’s CONTENTS can FLOW OUT and when RELEASED it SEALS again;
Allows IMPURITIES to ACCUMULATE in such a way that SAMPLES can be COLLECTED, INSPECTED, and TOTALLY DRAINED from this point
What are the main ways of reducing fuel contamination?
Why is this important to turbine systems?
Installing a STANDPIPE which PREVENTS the LAST of the FUEL and possibly some CONTAMINATES entering the system;
REFUELLING the tanks at the END of the DAY to PREVENT the CONDENSATION of WATER;
AVTUR is MORE HYDROSCOPIC than AVGAS
What is a cross feed system?
A FUEL SYSTEM where the INDIVIDUAL engine fuel systems are INTERCONNECTED;
Fuel can be FED from ANY TANK to ANY ENGINE;
Allows FLEXIBILITY to counter ENGINE FAILURES, LEAKS, and any OTHER IMBALANCES
Why may a cross feed system be required?
Required to CORRECT IMBALANCE of fuel BETWEEN WINGS as a result of engines burning UNEQUALLY DUE TO differing ENGINE TBO AGES, HEATERS using fuel from one side only, or SINGLE ENGINE operations during TRAINING
What are the 4 types of fuel quantity indicators?
SIGHT GLASS;
FLOAT type;
ELECTRIC type;
ELECTRONIC type
How does the sight glass fuel quantity indicator work?
A CLEAR GLASS or PLASTIC TUBE is OPEN to the fuel TANK that FILLS with fuel to the SAME LEVEL as the fuel in the tank;
CALIBRATED in GALLONS or FRACTIONS of a tank
How does the float type fuel quantity indicator work?
Utilises a FLOAT with an INDICATING ROD attached to it. As the float MOVES up and down WITH the FUEL LEVEL in the tank, the portion of the ROD that EXTENDS through the fuel cap INDICATES the QUANTITY of fuel in the tank
How does the electric type fuel quantity indicator work?
Operates with DIRECT CURRENT and use VARIABLE RESISTANCE in a circuit to drive a RATIOMETER-TYPE indicator through the MOVEMENT of a FLOAT in the tank which moves a CONNECTING ARM to the WIPER on a variable resistor in the tank;
CHANGES to the CURRENT flowing through the RESISTOR change the current of one of the COILS in the indicator;
This ALTERS the MAGNETIC FIELD which indicates the quantity
How does the electronic type fuel quantity indicator work?
Utilises a BRIDGE CIRCUIT which measures the CAPACITANCE of the tank units through fixed CAPACITORS that measure the DIELECTRIC CONSTANT (amount of fuel/air between the plates);
A REFERENCE CAPACITOR is used to account for differences in TEMPERATURE
How is a mechanical advantage achieved in a hydraulic system?
What law does it consider?
The OUTPUT PISTON is made LARGER than the INPUT PISTON so that when PRESSURE is EXERTED on the FLUID in the ENCLOSED system it is TRANSMITTED EQUALLY and UNDIMINISHED to ALL parts of the SYSTEM;
PASCALS LAW P(constant) = F(increases)/A(increases)
What is the purpose of seals?
PREVENT FLIUD from PASSING a certain POINT and to keep AIR and DIRT OUT of the SYSTEM being used?
Is there one seal that is satisfactory for all installations? Why?
NO, there are many VARIATIONS to the OPERATION of the aircraft including:
PRESSURE at which the SYSTEM OPERATES;
TYPE of FLUID used in system;
METAL FINISH and CLEARANCE between ADJACENT PARTS;
TYPE of MOTION (ROTARY/RECIPROCATING)
What are the 3 categories of seals?
Briefly describe what each one does?
PACKINGS:
GASKETS: Used as STATIC seals between 2 FLAT SURFACES;
WIPERS: Used to CLEAN and LUBRICATE EXPOSED portions of the PISTON SHAFTS
What type of seal is compatible with vegetable based fluids?
What colour is this indicated by?
NATURAL RUBBER seals;
BLUE colour
What type of seal is compatible with mineral based fluids?
What colour is this indicated by?
NEOPRENE RUBBER SYNTHETIC seals;
RED colour
What type of seal is compatible with synthetic fluids?
What colour is this indicated by?
ETHYLENE PROPYLENE SYNTHETIC seal;
LIGHT PURPLE colour
What is the principle of operation of an open centre hydraulic system?
Can we operate more than one service at a time?
The HYDRAULIC PUMP is CONTINUOUSLY flowing;
When the VALVE is in NEUTRAL position the FLUID is pumped through the SELECTORS, FILTER, and back into the RESERVOIR;
When the VALVE is MOVED to the SIDE of eg: the EXTEND ACTUATOR, the PATH DISCONNECTS in valve FROM RETURN TO EXTEND ACTUATOR SIDE;
NO, only one service can operate at a time
What is the principle of operation of the pressurised (closed centre) hydraulic system?
The PUMP directs FLUID to the UNLOADING VALVE which then directs it to the SELECTOR VALVES up to a PREDETERMINED PRESSURE, once this pressure is achieved the UNLOADING VALVE will direct fluid back to the RESERVOIR via the FILTER;
The UNLOADING VALVE, with the ASSISTANCE of the ACCUMULATOR will hold the PRESSURE until a SERVICE is REQUIRED and will then ADD PRESSURE accordingly
When may a pressurised system not require an unloading valve?
When a VARIABLE DELIVERY or CONSTANT PRESSURE PUMP that is designed to MAINTAIN PRESSURE is INSTALLED
What happens to the pressure of the system when a hydraulic function is required?
What effects will this have on the system?
The PRESSURE will DROP;
The UNLOADING VALVE will deliver MORE PRESSURE until it builds again or if it FAILS the ACCUMULATOR will SOFTEN any large SPIKES/DIPS in pressure
What are the components of all basic hydraulic systems?
PUMP; RESERVOIR; DIRECT CONTROL VALVE; CHECK VALVE; PRESSURE RELIEF VALVE; SELECTOR VALVE; ACTUATOR; FILTER
What are the types of engine driven hydraulic pumps?
VANE TYPE;
GEAR TYPE;
PISTON TYPE
What is the principle of operation of the vane type hydraulic pump?
OFFSET AXLE, with SPRING loaded arms which cause the CHAMBERS to CONSTRICT and INCREASE PRESSURE;
Moves LARGE VOLUMES at LOW PRESSURE
What is the principle of operation of the gear type hydraulic pump?
COUNTER ROTATING GEARS that force fluid through a SMALLER SPACE;
Move MEDIUM VOLUMES at 1500PSI
What is the principle of operation of the piston type hydraulic pump?
Several PISTONS on a ROTATING AXLE angled so that the INLET is on the TOP SIDE of the PISTON and as it ROTATES CHAMBER gets SMALLER and PRESSURE INCREASES on the LOWER SIDE;
Moves LOW VOLUMES at 3500PSI however MULTIPLE may be REQUIRED
What are the types of non-engine driven hydraulic pumps?
HAND PUMP;
R.A.T;
ELECTRICALLY DRIVEN
What is the principle of operation of the hand hydraulic pump?
Provides PRESSURE created by PILOTS in EMERGENCY situation or during GROUND TESTS
What is the principle of operation of the R.A.T (ram air turbine) type hydraulic pump?
SPRING LOADED PROPELLER will move into AIRFLOW and be driven by airflow to provide HYDRAULIC PRESSURE
What is the principle of operation of the electrically driven hydraulic pump?
Act as AUXILIARY PUMP on GROUND and as a SUPPLEMENT to ENGINE DRIVEN in FLIGHT
How can hydraulic pumps be classified by how they move fluid through them?
What does each mean and what are some examples?
POSITIVE DISPLACEMENT: Provides a CONTINUOUS FLOW and has good INTERNAL SEALS so there is NO SLIPPAGE of the FLUID. MOST are this TYPE and will cause a PRESSURE RELIEF valve to ACTUATE in an OVER PRESSURE or BLOCKAGE;
NEGATIVE DISPLACEMENT: Provides a CONTINUOUS FLOW but does NOT have INTERNAL SEAL so a BLOCKAGE of FLUID will SLIP within the PUMP and flow will reduce to 0. Used in CENTRIFUGAL and PROPELLER PUMPS
What is an actuator?
What is the purpose of it?
A CYLINDER and PISTON with attached PISTON ROD that is connected to the desired COMPONENT;
The cylinder contains a POLISHED BORE and PORTS where the fluid ENTERS and EXITS;
It acts to CONVERT PRESSURE ENERGY in the hydraulic fluid into a MECHANICAL FORCE
What is the purpose of hydraulic fluid filters?
How are clogged filters countered?
To REMOVE all SOLID PARTICLES ABOVE 25 microns in size and REMOVE most SOLID PARTICLES ABOVE 20 microns in size;
BYPASS VALVES may be fitted
What is a hydraulic fuse?
What is the purpose of it?
A form of SHUTOFF VALVE to STOP the complete LOSS of FLUID if a LEAK is to occur DOWNSTREAM;
For NORMAL operations the hydraulic PRESSURE will oppose a spring to hold a PISTON OPEN, however if PRESSURE is LOST on one side the SPRING will OVERCOME it and any REMAINING PRESSURE will force the PISTON SHUT, PREVENTING FLOW
What are the characteristics of a hydraulic reservoir?
PROVIDE system FLUID and COVER for any LEAKS;
Allow BUBBLES to be PURGED;
SEPARATE foreign MATTER from FLUID (STANDPIPE);
Act as OVERFLOW BASIN;
Includes BAFFLES
What is a standpipe?
What is the purpose of it?
A PIPE that sits just ABOVE the BOTTOM of the RESERVOIR from which fluid is drawn from;
Creates a small amount of UNUSABLE FLUID for DEBRIS and FOREIGN MATTER to collect without risk of it entering and causing DAMAGE to the system;
Allows a SMALL amount of FLUID to be AVAILABLE if the EMERGENCY system requires it
What is an emergency fluid system?
What is the purpose of it?
A system which DRAWS FLUID from the BOTTOM of the RESERVOIR rather than the STANDPIPE;
The ENGINE-DRIVEN pump (EDP) is NOT ABLE to DRAW FLUID any more if the RESERVOIR gets depleted BELOW the STANDPIPE;
The ALTERNATING CURRENT MOTOR-DRIVEN pump (ACMP) still HAS a SUPPLY of FLUID for emergency operations
What are the methods of checking hydraulic fluid levels both on the ground and in-flight?
.
What are the different types of hydraulic valves?
CHECK valve; RELIEF valve; BYPASS valve; SELECTOR valve; SEQUENCING valve; SHUTTLE valve; PRESSURE CONTROL valve
What are check valves?
What is the purpose of them?
NON-RETURN valves, fitted to PREVENT REVERSE FLOW within the system usually through the use of a BALL and SPRING which TRAP PRESSURE in the lines BETWEEN the VALVE and ACTUATOR to generally HOLD the ACTUATOR at selected POSITION, this acts to COUNTER any UPSTREAM LEAKS
What are relief valves?
What is the purpose of them?
SAFETY valves that are usually SPRING LOADED which will OPEN if PRESSURE EXCEEDS PREDETERMINED LEVEL
What are bypass valves?
What is the purpose of them?
A valve which provides an ALTERNATIVE PATH around a component if it is NOT REQUIRED or the PRESSURE becomes TOO LARGE
What are selector valves?
What is the purpose of them?
A VALVE is used to CONTROL the DIRECTION of movement of the pressurised FLUID to the SELECTED ACTUATING FUNCTION;
Can be ROTATING PLUG, POPPET TYPE or an OPEN CENTRE ROTATING PLUG
What are sequencing valves?
What is the purpose of them?
VALVES that cause FUNCTIONS to operate in a CERTAIN ORDER;
Most commonly known through the WHEEL well DOORS and the LANDING GEAR
What are shuttle valves?
What is the purpose of them?
A VALVE that allows FLOW from an OUTLET port FROM either of 2 INLET ports while BLOCKING FLOW to the OTHER if original PRESSURE DROPS below a certain THRESHOLD
What are pressure control valves?
What is the purpose of them?
Valves that maintain a SPECIFIC PRESSURE, includes PRESSURE RELIEF valve and PRESSURE REDUCING VALVE
What is used to set the timing between the landing gear and wheel well doors?
A SEQUENCING VALVE;
To ensure that the DOORS are CLOSED at all times the LANDING GEAR is NOT MOVING up or DOWN and the DOORS OPEN BEFORE GEAR ACTUATES
What are the components of the Bogie truck main landing gear assembly?
PIVOT TRUNNION; TRUNNION BEAM; UPPER SIDE BRACE; LOWER SIDE BRACE; DRAG BRACE; UPPER OUTER SHOCK CYLINDER; LOWER INNER SHOCK CYLINDER; TORQUE ARMS; POSITIONER; PIVOT FORK and SHAFT; PIVOT BEAM (TUBULAR H MEMBER); EQUALISER; AXLE; INDEPENDENT ROTATING WHEELS
What is the purpose of the pivot trunnion?
To ANCHOR the UNDERCARRIAGE to the aircraft STRUCTURE
What is the purpose of the trunnion beam?
Allows the gear to PIVOT as it is EXTENDED and RETRACTED
What is the purpose of the upper and lower side brace?
What additional feature allows stowage in this section?
SUPPORTS the gear LATERALLY against CROSSWIND or SIDE LOADS;
Contains a KNUCKLE which can be BROKEN in order to RETRACT and FOLD gear
What is the purpose of the torque arms?
Maintain FORE-AFT ALIGNMENT of the UNDERCARRIAGE
What is the purpose of the pivot fork and shaft?
PIVOTS the PIVOT BEAM (H MEMBER) to the BOTTOM of the main STRUT
What is the purpose of the pivot beam?
Runs in the FORE-AFT axis and has the 4 AXLES and WHEELS ATTACHED
What is the purpose of the equaliser?
To PREVENT the ANGLE of the PIVOT BEAM from being more than it should be;
SET the ANGLE of the PIVOT BEAM so that the WHEELS will SPIN up nicely once they contact the ground
What is the purpose of the positioner?
HYDRAULIC RAM that will PUSH the PIVOT BEAM into position SET by the EQUALISER
What is the purpose of the shock strut?
An OLEO STRUT that acts to DAMPEN any SHOCKS
What is the purpose of the drag brace?
Where are they positioned?
BRACES the gear in the FORE-AFT AXIS;
FOWARD side and REAR side of the MAIN STRUT
What are boosted brakes?
What is the purpose of them?
A braking system USED predominantly for LARGER aircraft where GREATER BRAKING is REQUIRED
The hydraulic pressure for the system is provided by DEPRESSING a PISTON within a MASTER CYLINDER however, as brake PRESSURE is progressively APPLIED by the pilot, HYDRAULIC PRESSURE from the MAIN system is progressively fed through a VALVE INTO the back of the MASTER CYLINDER PISTON;
When PRESSURE is RELEASED by PEDAL, PRESSURE is RELEASED through RETURN LINE to MAIN system
What are anti-skid units?
What is the purpose of them?
A system which COMPARES the SPEED of the AIRCRAFT WITH the ROTATIONAL SPEED of each main WHEEL;
If the SPEED of any WHEEL is too SLOW for the existing AIRCRAFT SPEED, the BRAKE on that wheel (or wheels) is RELEASED momentarily to allow the WHEEL SPEED to INCREASE and PREVENT the wheel from SKIDDING
What are the components of an anti-skid system?
What is the principle of operation of the anti-skid brakes?
WHEEL SPEED SENSOR: A STATOR in the wheel AXLE with a coil around it connected to a CONTROLLED DC source so that when ENERGISED the STATOR becomes ELECTROMAGNET. Inside the STATOR is a ROTOR that rotates at the SPEED of WHEEL. As the FIELD CHANGES a VARIABLE FREQUENCY is induced in coil which is directly PROPORTIONAL to SPEED of WHEEL;
CONTROL UNIT: COMPARATIVE CIRCUITS are used to determine if any of the signals INDICATE a SKID is IMMINENT or OCCURRING on a PARTICULAR wheel. Then SIGNALS are sent to the CONTROL VALVE;
CONTROL VALVE: Receives SIGNAL and RELIEVES or ADDS hydraulic PRESSURE to that brake to achieve OPTIMUM BRAKING
What protection systems are built into the anti-skid system for touchdown and wheel braking abilities?
A WEIGHT on the wheels SWITCH will NOT let BRAKES be APPLIED during touchdown UNTIL SQUAT SWITCH is activated;
There are SENSORS on each WHEEL PAIR and ADJACENT WHEELS that DETECT if there is a 25% DIFFERENCE between wheel ROTATION and if so, it will REDUCE PRESSURE on the SLOWER WHEEL
What are the advantages of pneumatics over hydraulic systems?
ENDLESS supply of AIR;
COMPONENTS reasonably LIGHTWEIGHT and SIMPLE;
COMPRESSED AIR is LIGHTWEIGHT and NO RETURN REQUIRED;
Relatively FREE from PROBLEMS;
NO FIRE HAZARD, good DESIGN minimises EXPLOSION HAZARD;
Proper FILTERS minimise CONTAMINATION
What are the disadvantages of pneumatics over hydraulic systems?
AIR must be significantly COMPRESSED to ACTUATE heavy MECHANICAL DEVICE;
COMPRESSIBILITY of AIR leads to LAG in RESPONSE;
NOT suitable for PRECISE control operations;
DIFFICULTLY to provide AIR TIGHT SEALS and finding LEAKS
What are the characteristics of a low pressure pneumatic system?
VACUUM or PRESSURE system for GYRO INSTRUMENTS
What are the characteristics of a medium pressure pneumatic system?
.
What are the characteristics of a high pressure pneumatic system?
.
How can a pneumatic pressure actuate a hydraulic system as a backup?
SHUTTLE VALVE will ACTUATE, normally allowing hydraulic PRESSURE into the required ACTUATOR, but in event of HYDRAULIC FAILURE, will allow PNEUMATIC PRESSURE into the system to ACTUATE the JACK
What is the purpose of a water separator?
PREVENT REFRIGERATION EFFECT, where MOISTURE in compressed AIR FREEZES when function is ACTUATED and PRESSURE DROPS
What is used to remove the moisture from a pneumatic system?
What percentage does each remove?
Moisture separator: 98%
Desiccant: 2%
What colour should the desiccant have if it is new and does not have any moisture contamination?
Blue
What are the characteristics of the back up pneumatic system?
SHUTTLE VALVE directs either normal hydraulic system PRESSURE or EMERGENCY AIR PRESSURE into landing gear or brake actuator;
N2 move fluid through pnuedraulics
