AFT aero and systems notes Flashcards
What are the 4 types of reaction engines?
Rocket
Ram Jet
Pulse Jet
Gas Turbine
What is a rocket?
Self contained air and fuel in pressurised container
What is a ram jet? What entry and exhaust duct type does it have?
No moving parts, requires large forward speed to operate
Divergent entry duct
Convergent exhaust duct
What is a pulse jet?
Similar to Ram jet but on intermittent cycle
What is a gas turbine?
Turbine driven compressor. Does not require forward airspeed to compress the air entering the engine
What is maximum thrust of a gas turbine limited by?
The maximum turbine temperature
If there was a large increase in gas temperature from the air intake to the turbine, what happens to the volume of gas, acceleration of the air and thrust produced?
Volume of gas increases
Acceleration of air increases
Thrust produced increases
What happens to thrust as air temperature increases?
Thrust decreases
What happens to thrust as altitude increases?
Thrust decreases due to less dense air
What happens to thrust if the mass air flow decreases?
Thrust decreases
What is the thrust formula?
Thrust = (Mass airflow X Jet exhaust velocity) - Aircraft forward speed
Describe a basic pure turbo jet.
One or more compressors driven by set of turbine wheels.
What is a spool?
Compressor at the front of an engine and its accompanying set of turbine wheels at the rear
How does a pure turbo jet deliver its thrust?
Reaction to the rearwards acceleration of exhaust gases after it has passed through the turbine sections of the engine
What happens to the static pressure at the exhaust outlet of pure turbo jet compared to the intake?
Roughly double
What is the EPR?
Engine pressure ratio.
Static pressure at the exhaust outlet compared to that at the intake
What indication does the EPR give to pilots?
Thrust output
What would a blocked EPR cause to the gauge?
Cause it to overread
Describe the basic high by-pass jet (turbo fan)
Not all air passes through the engine core and combustion chamber. Large fan (N1) is at the front of the compressor and driven by extra turbine at rear of engine
What is the by-pass ratio?
Ratio of air which bypasses the engine core compared to the air which passes through the core
What is the formula for the by-pass ratio?
By-pass ratio = (By-pass mass flow) / (Engine core mass flow)
What would an engine sound like, efficiency be with a high by-pass ratio?
Quieter and more efficient
Where is the majority of thrust produced in a high by-pass ratio engine?
From the by-pass fan air
Where is the majority of thrust produced in a low by-pass ratio engine?
From the jet exhaust
What are the advantages of the free power turbine turbo prop?
Lower starting torque (since starter doesn’t drive the prop)
Variable prop speed
High torque at low speed
What is the main difference between gas turbine and piston cycle?
Gas turbine is continuous
What is the role of convergent ducts?
Increase velocity
Decrease pressure
Decrease temperature
What is the role of divergent ducts?
Decrease velocity
Increase pressure
Increase temperature
In the compressor, what happens in the centrifugal flow?
Impeller accelerates mass air flow and imparts a pressure rise and a diffuser (divergent duct) to increase pressure
What does an axial flow compressor consist of?
Rotor blades attached to main rotor assembly
Stator vanes between each rotor blade (do not rotate)
What is the role of the rotor blades and stator vanes in axial flow compressor?
Rotor blades increase velocity of airflow
Stator vanes are located between each rotor blade, do not rotate. They increase pressure by forming divergent duct
How are rotor blades shaped in axial flow compressor?
Aerofoil shaped and therefore must be presented at correct angle of attack
How are stator vanes shaped in axial flow compressor?
Shaped to direct air from one set of rotors to the next at correct angle of attack
Where is the largest air load in the axial flow compressor?
Rear most blades of compressor
Compared to a centrifugal compressor of the same frontal size, what does an axial flow compress do to air and pressure?
Consumes more air and gives bigger pressure rise
What types of airflow control are there?
Variable inlet guide vanes (VIGV)
Variable stator vanes
Bleed air valve (surge valve)
What are variable inlet guide vanes? Where are they located?
Change angle at which relative airflow meets the first stage compressor, preventing surge and stall.
Located at front of compressor
What are variable stator vanes?
Change angle of each row of stator vanes to maintain correct angle of attack when engine operating ‘off design RPM’
What are bleed air valve (surge valve)? Where is it used? What sort of compressor is it used in?
Used with axial flow compressors, valve towards rear of compressor.
Valve opens when operating off design RPM to reduce compressor outlet pressure and increase mass airflow across early stages of compressor
What percentage of total mass airflow enters the combustion chamber through the primary zone? What is it for?
20%
Flame stabilisation and combustion
What percentage of air enters the primary zone through holes in the wall of the flame tube?
20%
How much of the total mass airflow is used for cooling and dilution further down the chamber?
60%
What percentage of air is used for combustion? What is it called?
12%
Primary air
Where does primary air enter the combustion chamber?
Through the swirl vanes at the front of the combustion chamber
What is the purpose of the swirl vane?
Reduce axial flow
Keep flame stable in the primary zone of combustion
Where does the highest gas temperature occur during combustion?
In the primary zone of combustion
When is a rich flameout possible?
Mixture is too rich
low speed and high powered climb
When is a lean/weak flameout possible?
Mixture is too weak
High speed and low power descent
With a multiple combustion chamber, how is pressure equalised? What else does this device allow?
With interconnectors.
Allows flame propagation between chambers
What is the most effective combustion chamber in terms of efficiency, cost and weight?
Annular
What are NGV?
Nozzle guide vanes.
Positioned in front of each turbine wheel.
Stationary aerofoil blade shaped as convergent ducts
What is the purpose of the NGV?
To increase velocity of gas stream onto next set of turbine blades at correct angle of attack
What are turbine blades and what are their purpose?
Blades attached to turbine disc.
Extract energy from gas stream to drive compressor, fan or gearbox
What are shrouds?
Caps on the tips of some blades to reduce gas leakage, reduce vibration and increase strength
What is blade creep? What causes it?
Increasing in length of turbine blades
Caused by excessive exposure to high temps, centrifugal forces and stress
What are the different types of blade creep and when do they occur?
Primary creep (during manufacture) Secondary creep (during service life) Teriary creep (failure)
What is the most critical temperature in the engine?
Turbine temperature
In a turbo jet engine, how much energy of the total energy of the gas stream is used to drive compressor?
75%
In a turbo jet engine, how much energy is used for thrust?
25%
What are support struts?
Used to keep exhaust flow streamlined
What does the jet pipe do?
Carries exhaust gases from turbine to propelling nozzle
What is the propelling nozzle?
Convergent to Increases the velocity of exhaust to give final increase in thrust
What is the main source of noise from a turbo jet?
Exhaust noise
What is the main method of noise suppression for turbo jets?
Increase frequency (Hz) of exhaust noise from low to high. Done by mixing cool air with hot exhaust gases
Which is quieter, turbo prop or turbo fan?
Turbo fan
What is the main source of noise from a turbo fan?
The fan and the turbine
What is thrust reversal?
Angling the thrust to go forwards
What does thrust reversal do to landing distance?
Decreases landing distance
When should thrust reversers be used?
Early stages of landing roll when speed is high.
Why should we not used thrust reverse at low speeds?
Hot turbulent air can enter the engine along with foreign objects
What reverse thrust is used on turbofans?
Cold by-pass only (coldstream reversers such as blocker doors)
How do blocker doors work?
Blocker doors in the by pass duct to redirect coldstream air out through cascade vanes in the engine cowl
What are interlocks?
Prevent thrust lever from being moved to reverse position unless engine is running at low power setting
What are turbine oils like?
Medium to low viscosity
Stable under high operating temperatures
What two things act together to maintain a constant RPM in a turbo prop?
Fuel control unit
Propeller governor
What happens in turbo prop as power levers are advanced?
FCU sends extra fuel to combustion chamber which increases engine output and tries to drive turbine faster.
Prop governor detects this and coarsens blades to absorb extra energy and provide more thrust at constant RPM
What is the beta range?
In a turbo prop, the ground handling range, where the prop blade angle isn’t controlled by the prop governor but via the power lever position via oil pressure control system
What is the NTS?
Negative torque system.
Provides a signal which increases prop blade angle to limit negative shaft torque
What conditions is NTS likely to operate?
Temporary fuel interruptions
Air gusts loads on prop
Normal descents with lean fuel scheduling
High Compressor air bleed conditions at low power
Normal shutdowns
What is TSS?
Thrust sensitive system (autofeather)
What does TSS do?
Automatically feathers prop if there is a power loss during take-off.
Automatically increases blade angle and causes prop to feather
What is the safety coupling?
Safety feature of the turbo prop.
Disengages the reduction gear from engine if it’s operating about a preset negative torque value. (much higher value then required for NTS)
After being disengaged, when will the reduction gear be re-engaged?
Automatically during feather or engine shutdown
What is a prop brake?
Rapidly slow prop after engine shut down.
Prevents windmilling on ground
In a turbojet fuel system, what happens to fuel flow as altitude increases?
Fuel flow decreases
What are impellers used for in the fuel system?
Boost pumps in tanks to supply high pressure
What problems could there be if using AVGAS instead of kerosene in a jet engine?
Decrease range
Poor altitude performance
Over temperature
Over speed
What is the specific gravity and flash point of AVTUR compared to AVGAS?
AVTUR SG = 0.8, flash point = 46 degrees
AVGAS SG = 0.72, flashpoint = -40 degrees
How is fuel measured?
Capacitance type system with probes (capacitors) in fuel system
What is a standpipe?
Prevents accidental dumping of entire fuel load if the dumps not shut off manually at desired quantity
What are baffles?
Dividing partitions in fuel tank used to limit movement of fuel
Hot bleed air from the compressor, hot oil or electrical system is used to prevent ice on what devices?
Wing leading edge and props on turbo props
What negative effect does hot air anti ice have?
Decrease in thrust when air is taken from compressor
What is the normal procedure for starting the turbine engine?
Starter and ignition on
When N2 = approx 10/15% add fuel and watch for light off
Check for rapid TOT increase to confirm light off
What speed is self sustaining?
35-50%
When can a hot start occur?
High fuel flow
Low RPM
Tailwind
What are the indicators of a hot start?
After light off, TOT increases beyond maximum
What are the indicators of a wet start
Added fuel at 15% but no light up occurs
What is a hung start?
Not enough starter power to reach self sustaining speed
What may a hung start lead to?
A hot start
What should be done in the event of a hot, wet or hung start?
Shut fuel off
Keep starter on
What is the formula for specific fuel consumption?
Fuel flow / thrust produced
Is a high or low specific fuel consumption (SFC) preferred?
Low
What will cause an increase in specific fuel consumption?
Increase in ambient temperature
Decrease in compressor pressure
Operation outside design RPM
What are the advantages of turboprop?
Higher thrust at low forward speeds
Lower thrust specific fuel consumption
Quieter than turbofan or pure jet
More suited to short sectors
What are the disadvantages of turboprops?
Engines are heavier
Not suited to high altitude
Not suited to long sectors
What is the APU used for?
Provide source of electrical and pneumatic power independent of ground support or aircraft engines
In the event of an engine failure, what can be done to assist with electrical load?
Turn on the APU
What happens to engine bleed air that is not required by the aircraft of APU?
Dumped overboard downstream of turbine section
What will activate the APU automatic shutdown?
Fire detection Automatically activated fire extinguisher Low oil pressure High oil temp High exhaust gas temp Overspeed Duct overheat
What happens in a convergent duct if the flow is supersonic?
Velocity decreases
Pressure rises
Density rises
What happens in divergent duct if the flow is supersonic?
Velocity increases
Pressure decreases
Density decreases
What is subsonic flow?
Flow velocity less than speed of sound
What is sonic flow?
Flow velocity at speed of sound
What is supersonic?
Flow velocity greater than speed of sound
What is Mfs?
Mach Free Stream
Mach number of aircraft through the air
What is the local mach number?
Mach number of the flow at a particular location on an aircraft/aerofoil
What is Mcrit?
Critical mach number.
Mach number which first produces evidence of local sonic flow.
Start of transonic range
Above what speed does shockwaves form on the wing?
Mcrit
What is Mcdr?
Critical drag rise mach number.
Significant shockwave related problems as shockwave grows and moves rear
What is higher, Mcrit or Mcdr?
Mcdr
What is Mdet?
Detachment mach number.
Aircraft mach number at which bow waves attaches to leading edge or nose.
What speed range does Mdet mark? And what is the flow type?
Marks end of transonic speed range
All flow is supersonic above Mdet
What is Mmo?
Maximum operating mach number.
Highest mach number at which aircraft can be intentionally flown
What happens if you fly above Mmo?
Shock wave formation
Control problems
High airframe stresses
What happens to velocity, mach number, static pressure, density, temp and total pressure in a normal shockwave?
Decrease in velocity and mach number (subsonic)
Increase in static pressure, density and temperature
Less total pressure
Where are oblique shockwaves likely to form?
Around compressive corners in supersonic flow
What happens to airflow in oblique shockwave?
Change in direction
Reduction in velocity and mach number
Rise in density and static pressure
What happens to static pressure, velocity and temp in expansion waves?
Decrease in static pressure and temp
Increase in velocity
What is the speed range for subsonic?
0-0.75M
What is the speed range for transonic?
0.75 - 1.20M
What is the speed range for supersonic?
1.2-5-0M
What is the pitching tendency as shockwave forms?
Pitch down
What is mach tuck?
CP moving rearwards generating a nose pitch down
What does the Mach trimmer do?
Automatically applies back elevator trim to compensate mach tuck as speed increases
What are the advantages of swept back wings?
Delays compressibility effects
Increase Mcrit and Mcdr
Increase force divergent number
Reduced CL changes with both speed and AoA
Improved lateral and directional stability
What are the disadvantages of swept back wings?
Tendency to stall tip first
Reduced max CL and higher stall angle
Reduced trailing edge device effectiveness
Dutch roll tendency
Structural complexity
High induced drag at high angle of attack
What is super-critical wing section?
Flattened top surface to reduce top surface acceleration and delay compressibility effects
What does super-critical wing section do?
Helps lift at low speed and high angle of attack
What happens to lift, drag, pitch and centre of pressure as aircraft passes Mcrit?
Increase in drag
Decrease in lift
Pitch down
CP move rearwards
What do vortex generators do?
Delay shock induced separation by reenergising boundary layer.
What can be done to assist with dutch roll tendency?
Yaw dampers
What do yaw dampers do?
Automatically applying a cancelling rudder input when yaw is sensed
What are the two types of yaw dampers?
Series and parallel
What does the parallel type yaw damper do? When can it be switched on/off?
Moves rudder pedals
Must be off for take off/landing
What does the series type yaw damper do? When can it be on/off?
Does not move rudder pedals
Can be on at all stages of flight
What provides the signals to the yaw damper?
Rate gyro
What does a swept wing do to stall angle of attack, maximum CL and drag?
Increases stall angle of attack
Reduces max CL
Increases drag
What is the lift and drag like of a swept wing compared to a straight wing?
Less lift more drag
As a swept wing approaches the stall, what happens to centre of pressure?
CP moves forwards and inwards
In a swept wing plane, what is tendency of pitch at stall?
Pitch up
What does increased gross weight do to stall speed?
Increases the stall speed
What do use of flaps do to stall speed and CL?
Decrease stall speed
Increase max CL
What does a forward CoG do to stall speed?
Increases stall speed
At higher altitude, what is the stall speed IAS and EAS?
IAS and EAS stall speed increases.
IAS greater than EAS
What is Va?
Manoeuvring speed
What happens if full control deflection occurs below Va?
G stall before load limit is reached
What happens if full control deflection occurs above Va?
Load limits being exceeded before stall occurs
What is the Va for a heavier aircraft compared to a lighter one?
Faster for heavier gross weight
In equilibrium what do all the forces equal?
Weight = lift drag = thrust
Where does lift act through?
Centre of pressure
What is the lift formula?
CL x 1/2 x p Vsquared x S Wherer CL = Coefficient of lift p = air density V= velocity or TAS of air flowing around wing S = Surface area of the wing
What is the formula for power?
Thrust x TAS
What is Vimd?
The speed where total drag is minimum
Indicated minimum drag
What is Vimd also known as?
Minimum drag speed Best lift/drag ratio Minimum fuel flow Best endurance Maximum excess thrust Max angle of climb
Where does max still air range occur?
1.32 Vimd
In a headwind, what do you need to do to achieve max range?
Fly faster then 1.32 Vimd
What speed do you need to fly at for max endurance?
Minimum fuel flow
Vimd
What speed are you said to be flying at if you are in the region of reverse command?
Less that Vimd
In a steady climb, what is thrust, drag, lift and weight?
Thrust > Drag
Weight > Lift
Climbing using maximum excess thrust would be climbing at what?
Max angle of climb (Vx)
Vimd
Climbing using max excess power would be climbing at what?
Max rate of climb (Vy)
What happens when flaps are extended?
Increase in lift
Increase in drag
Lower Vimd compared to clean
What is the TAS and IAS for max rate of climb at a higher altitude compared to lower altitude?
TAS = Higher IAS = slightly lower
What happens to the minimum control speed as altitude increases?
Decreases
What does a forward CoG do to minimum control speed?
Lowers it
What does flap extension do to minimum control speed?
Increases it
What does gear extension do to minimum control speed?
Increases it
What does ground effect do to minimum control speed?
Decreases it
What is V1 speed?
Decision speed (whether to take off or not)
What are the two considerations for V1?
- ) If take off continued, after an engine failure, at or above V1 will be possible to obtain 35 feet within schedules take off distance.
- ) If take off rejected at or below V1, it will be possible to stop within scheduled acceleration stop distance
What is Vr?
Rotation speed
What are the two conditions for Vr?
Must not be less than V1
Must not be less than 1.05 Vmca
What is V2?
Take off safety speed
What are the two conditions for V2?
Must not be less than 1.1 Vmca
Must not be less than 1.2 Vs
In flight and after engine start, how is electric power supplied?
By 3 phase alternating current (AC) generators
What is an APU?
Small gas turbine located in the tail to assist with power on ground
What does the APU do?
Drives AC electrical generator
Provides bleed air to aircraft pneumatic system for aircon and main engine start independent of ground support or engines.
What does APU in flight?
Provides AC electrical power at all altitudes
Bleed air at lower altitudes
What is a RAT?
Ram Air Turbine
What does RAT do?
Ram Air turbine.
Deployed to windmill airstream to drive generator in emergency
Drive hydraulic pump
What does the battery provide for the APU?
DC power for APU start plus limited emergency DC power for vital systems in complete electric failure
What is electric power used for? What about pneumatic?
Electrical: ground servicing, preflight and transit checks
Pneumatic: Air con and engine start
Does the APU need a constant speed drive?
No as it operates at constant speed
What happens to bleed air not required by aircraft of APU?
Dumped overboard downstream of turbine
Where does fuel for the APU come from?
One of the main tanks and delivered under pressure by one of the two pumps
When does the fuel valve open and close for the APU?
Opens when APU start is initiated
Closes automatically on shutdown
Why is AC preferred to DC?
Weight and space saving and low current transmission
AC generators are lighter than DC ones
What must a generator have to generate current?
Field excitation
What is a voltage regulator?
Controls the current supplied to windings as DC
What is a series wound?
Generator field is in series to armature
As load increases voltage increases
What is a shunt wound?
generator field is in parallel to armature
As load increases, voltage decreases
What is compound wound?
Generator that makes use of both Shunt and series winding to produce constant voltage over range of loads
What is the PMG?
Permanent magnet generator.
Small generator within main generator
What does PMG do?
Provides initial excitation for magnetic field
How is PMG monitored and what is it used for?
On a voltmeter
Check serviceability of main generator
When would the FIELD OFF light illuminate?
If field circuit is manually or automatically tripped, disconnecting voltage regulator from excitation field
What does frequency output of AC generator depend on?
Speed of rotation (faster the rotation, higher the frequency output)
What is a CSD?
Constant speed drive
What is a CSD for?
Ensures generator maintains its designed operating RPM irrespective of change in engine speed
How does the CSD operate?
Hydraulically and has its own oil reservoir
Once disconnected, when can the CSD be reconnected?
Only once on the ground
When a CSD is disconnected, what are the indications?
CSD low oil pressure light
Frequency 0
Voltage 0
What is done to prevent accidental turning off of the CSD?
Guarded red switch
What is normal output for AC generator?
115v 400 Hertz
How are power ratings of AC generators expressed?
kVA
What is a Bus in the electrical system?
Point receiving current from generator or battery for distribution users
What is a split bus system?
One generator supplies a bus at a time
What is a parallel generator system
Multiple generators may be connected to one bus
Can external power sources be parallel?
No
What happens to generators and external power once engine is started?
Generator breaker switch is selected to close, external power on that side will automatically trip and incoming generator will assume load
What is the job of the TRU?
Transformer rectifier unit.
Transforms 115V AC to 28 VDC with use of diodes
What happens if essential power fails?
Standby busses automatically isolated from essential busses.
Battery energises inverter which supplies 115 V to standby AC bus
What are trip free circuit breakers?
Always free to trip in overload condition regardless of reset button
Cannot be overridden
What are non trip free circuit breakers?
May be overridden by depressing the reset button even if fault exists
What is a bus tie switch?
Control bus tie breaker which joins two or more busses together to provide generator redundancy in parallel electric system
What does a transformer do?
Reduces voltage of AC
What does a rectifier do?
Converts AC to DC using diodes which allow current to flow in one direction
What does a static inverter do?
Converts 28V DC to 115V 400 Hertz AC by use of transistors
Once employed, when can RAT be stowed?
Only once on ground
What are pilot exciters?
Small generator built in to large generator which provides initial field excitement until main generator is self sustaining
How is battery capacity measured?
Amp hours
What is a battery in series?
Battery connected in series (positive to negative) which increases VOLTAGE at constant current (amp)
What is a battery in parallel?
Battery connected in parallel (positive to positive or negative to negative) which increase total CURRENT (amps) at constant voltage
How are batteries generally charged?
Constant volts at reducing current
Why do lead batteries need to be vented?
They give off explosive mixture of oxygen and hydrogen when being charged
What are the advantages of NiCad batteries over lead acid?
Lighter and tougher
Don’t give off as much dangerous gas
Faster recharge
More useful capacity
What are the disadvantages of NiCad batteries?
Higher purchase cost
Reduced capacity if not fully charged
Increased risk of thermal runway
What is thermal runway?
During charging where battery overheats and electrolytes boil. Gas is released and plates melt resulting in battery damage and perhaps explosion
How are NiCad batteries protected against thermal runway?
Vented battery compartments
Battery temp sensors
What is the fluid reservoir?
Stores supply of hydraulic fluid and must be sufficient to operate system and to supply reserve in case of emergency.
Replenishes fluid lost to leaks
What happens before hydraulic fluid returns to the fluid reservoir?
Passes through a filter where it is cleaned and cooled.
Purged of bubbles
What are baffles used for in the fluid reservoir?
Prevent foaming
Why is the reservoir vented?
To allow air to replace volume of fluid
What does the pressure relief valve do?
In the event that pressure regulator becomes inoperative and system pressure increases above designed max, PRV will open and allow excess fluid to return to reservoir
What is the shuttle valve?
Allows alternate system to pressurise the lines and provide system ops if primary pump fails
What are priority valves?
Automatically shut off supply to non essential services in event of hydraulic leak
What are accumulators in the hydraulic system?
Dampen out pressure pulsations (primary)
Store hydraulic fluid under pressure
At low speed, if full right aileron is applied, what happens to left and right wing?
Left wing inboard and outboard ailerons are deflected down
Right wing inboard and outboard ailerons deflected up. Right wing spoilers deflected up
How are speed brakes controlled?
Hydraulically controlled
What does deployment of speed brakes do?
Increase drag
Dump lift
Transfers weight to the wheels for better braking
What is the deflection angle for rudder within APU?
0-25 degrees
What is the reason for a moveable stabiliser?
Avoids prolonged deflection of elevator tabs and associated trim drag
Requirement for trim or large changes in CoG
What does the auto stab trim system do?
Senses elevator input signals
Trims stabiliser to fair the elevators
If the pilot has extended the flaps to landing config, and the IAS increases to flap limit speed, what happens?
Flap load limit relief system hydraulically and automatically retracts flaps to safe setting. FLAP LEVER DOES NOT MOVE
How are leading edge devices operated?
Hydraulically or pneumatically
What is EICAS?
Engine Indicating and Crew Alert System
When does the stick shaker operate?
Approx 7% higher than stall speed
What is PCN?
Pavement classification number
Strength of pavement
What is ACN?
Aircraft classification number
Weight of aircraft on pavement
What is the crews responsibility with regards to PCN and ACN?
Must ensure ACN does not exceed PCN
Where is the safety squat switch?
On the gear oleos
What does the sequencing valve do with regards to gear retraction?
Makes sure components operate in correct order.
Door open
Gear retracts (gear doesn’t retract till door full open)
Door closes (doors don’t start to close until gear fully retracted)
How do you turn with regards to nose gear steering?
Hydraulic system pressure
Tiller and pedals
When is tiller used? When are rudder pedals used for steering?
Tillers used for sharp turns
Rudder pedals to maintain directional control during TO and Landing
What happens to nose wheel after take off?
Centring mechanisms automatically centre nose wheel
essential to retract the wheel
What does the follow up linkage do with regards to steering mechanism?
Returns steering to neutral and holds correct angle of turn
What is one advantage of tilting trucks?
Allows to fit smaller wheels
What happens when trucks untilt after touch down?
Change aircraft systems back to ground mode ops
What defects can prevent main gear from retracting safely?
Body gear steering not centred
Main gear not tilted correctly
If the hydraulic fails, how do we extend gear?
Alternate gear extension sequence
Door opens
Gear unlocks allowing it to freefall to extended
Gear locks in position
Is there an alternate selection for retraction of gear?
No
If the green light doesn’t come on for gear down, how do pilots determine which gear is faulty?
Use EICAS or flight engineers module
What is the tiller steering angle?
0-65 degrees
What does the anti skid system do?
Continuously seeks level of correction of brake signal which produces max braking which is just short of skidding
What is a lock out valve on the brakes do?
Prevents one leaking brake line from causing loss of entire hydraulic system . Closes and isolates leak
If the auto brake system is engaged, what happens if the pilot uses manual brakes?
Autobrake is disengaged
How long does auto brake provide braking?
Until complete stop or until disarmed
What are the selections for auto brake?
1,2,3,4,MAX
Which provides more braking, Max on auto brake or max manual braking
Max manual braking
Which provides more braking, Max on auto brake or RTO?
RTO
With auto brakes engaged, when will RTO autobrake operate?
If thrust is retarded to idle above 85kts during take off
How is the auto pilot system disengaged?
Manual braking
Change selector to OFF or DISARM
Stowing speed brake lever before deployment on ground
Advancing thrust above idle
What are fusible plugs in the wheels for?
Melt at high temperatures and deflate tyres to prevent explosion
What happens if the fusible plugs melt?
Wheel MUST be replaced
When is manual reversion required?
If triple redundancy is not provided (three independent systems)
What is q feel?
Artificial feel for powered controls
based on airspeed
What do spoilers assist with?
Roll control and inflight speed brakes
What does variable incidence tail plane do
Assist elevator and for pitch trim
What do fowler flaps do ?
Increase SA
What do slotted flaps do?
Energise boundary layer
Delay stall
Allow higher body angle on approach
Why are tricycle undercarriage better than tail wheel?
Greater braking potential
Higher landing speeds
Less tendency to ground loop
Better visibility during take off and taxi
Which provides greater angle of nosewheel deflection, tiller or rudder?
Tiller
What does bogie configuration do?
Allows lower tyre pressure and therefore lower ACN
What conditions require tyre to be replaced?
Thermal plugs melting
Bulge in tread or sidewall
What is the primary purpose of the chine or ribs on tyres?
Deflect water away from engines
Secondary purpose to assist against hydroplanning
What does anti skid system do?
Normal skid control Locked wheel skid control Touchdown protection Hydroplane protection Failsafe protection
What does normal skid control do?
Prevents wheel from locking by relieving brake pressure if skid detected then reapplying pressure when wheel speeds ip
What does locked wheel ski control do?
Fully released brakes
What does touch down protection do
Prevents brakes being applied prior to landing by air/ground logic switch
Wheel speed must be 20kts before brake pressure applied
What does fail safe protection do?
Disables system in event of fault
What does modulator valve do in anti skid system?
Decrease pressure pulses
Felt as shutter in pilot toe braking
What is the formula for hydroplaning ROTATING wheel?
9 x Square root tyre pressure
What is the formula for hydroplaning non rotating wheel?
7 x square root tyre pressure
Name some systems that rely on pneumatics for operation?
Air con/pressurisation Wing and engine anti ice Engine cross bleed start Hydraulic reservoir pump Air drive hydraulic pump
When the engine is low thrust, what happens to HP valve?
Opens allowing high pressure air to power system
When thrust is increased what happens to HP valve?
Closes and LP check valve opens to supply bleed air
When can ice form?
When OAT and TAT (total air temp) in flight is 10 degrees or below and visible moisture
Where is bleed air provided to for anti icing?
Engine
Wings
Antennas
What does use of bleed air for anti ice do to engine?
Imposes heavy demand
How are props on turbo props de-iced?
Electrically on a phased cycle
What are the types of ground anti/de icing?
Type 1 (unthickened fluids) Type 2 (thickened fluids)
Which fluids are used for deicing generally and why?
Type 2
Type 1 have low viscosity and therefore only protect wing for short time.
What must you do to the EPR during engine bleed air anti ice operation?
Reduce maximum EPR
When must engine anti ice be on?
During all ground and flight ops when icing conditions exist or are anticipated
How is ice detected?
Sensor on the nose that displays warning on EICAS
What protection is there for the windscreens in terms of anti ice?
Electrically heated anti ice and anti fog
When is anti fog used on windshields and when does it run with regards to window heat?
Continuously and is independent of window heat
Should rain repellent be used on a dry windscreen?
No, smears and reduces forward visibility
What is the ventilation rate, temperature and minimum relative humidity for pressurised cabin?
One lb of air per person per minute
18-24 degrees
Relative humidity 30%
When will cabin altitude warning horn sound?
If cabin altitude exceeds 10000ft
When do emergency masks drop?
If cabin altitude exceeds 14000ft
What is the differential pressure
Difference in cabin pressure and atmospheric pressure
How is the cabin altitude regulated?
Cabin pressure controller
What does the cabin pressure controller do?
Signals outflow valves to spill more or less air overboard to maintain nominated cabin altitude (in isobaric control) OR a nominated differential pressure during cruise
On climb or descent, how is cabin pressure rate of change maintained?
Proportional to rate of climb or descent
What is required to be entered by the crew for the automatic mode of the cabin altitude?
Initial cruise flight level
Landing airfield elevation
When is standby mode used for cabin altitude?
Used in event of auto mode failure
What happens in standby mode for cabin altitude?
Cabin altitude is selected relative to proposed cruise altitude by referring to placard and desired cabin rate of change is also selected
When would a fully manual mode be used for cabin altitude?
In event
How is exceeding the maximum positive pressure differential prevented?
Positive pressure relief valve
What does positive pressure relief valve do?
Relieves cabin pressure in event of failure of normal outflow valves or incorrect setting
What does negative pressure relief valve do?
Opens to allow air INTO the cabin from outside if air pressure exceeds cabin pressure
How is the cabin pressurised?
Bleed air supplied to and distributed by air con system
What PSI is the max differential pressure the pressure relief valves limit the system to?
8.65PSI
When do the negative pressure relief valves open?
-1.0 PSI
What are the selections for cabin pressure?
AUTO
STBY
MAN AC
MAN DC
What are the two types of aircon systems/
Vapour and air cycle
What does the air con do to the bleed air before it enters the cabin?
Must cool it
What does the vapour cycle air con consist of?
Compressor
Evaporator
Condenser
What does the air cycle do?
Compresses and expands the air to extract heat and achieve cooling
What are the advantages and disadvantages of air cycle system?
Advantages: Simple and light
Disadvantages: Less effective than vapour, poor cooling on ground
What does basic air cycle system consist of?
Engine bleed air
Heat exchangers
Turbine
Compressor
Describe how the air cycle work?
Bleed air cooled by ram air through primary heat exchanger
Compressed by compressor driven by turbine
Passes through secondary heat exchanger and again cooled by ram air
Passes through turbine, further cooled and expanded
What is the temperature of the air fed to the cabin regulated by?
Air mix valves
What are air mix valves?
Regulate temperature of air to cabin
Mixes cold air with bleed air to achieve desired temp
What do ram air doors do in the air cycle machine?
Cooling of aircycle
Vary the volume of ram air passing through heat exchangers
What do humidifiers do in air cycle
Spray a mist of water into conditioning duct leading to cabin.
Maintains 30% humidity
On the ground, what does the air cycle system need?
Ram air flow needs augmentation from a bleed air powered turbo fan in the ram air duct
Why is air recirculated?
To reduce bleed load on engines and therefore save fuel
What is the ‘cost’ of recirculating air?
Degrades air quality
What is the ram air valve for?
Opened to allow outside air into cabin directly to provide ventilation and smoke removal.
Supplies air into main air supply ducts for delivery into the cabin but only for unpressurised flight
Bleed air from the pneumatic duct through each air con pack is controlled by what?
Independent left and right pack
What happens if one of the air con packs fails?
The other pack is able to take the load
Where does the left pack get its air from and supply it to?
Engine 1
Supplies to cockpit
Where does right pack get its air from and supply it to?
Engine 2
Supplies to Cabin
How long do cockpit voice recorders cycles last?
30 minutes
How long do FDR cycles last for?
approx 25 hours
Where are FDRs located?
In the tail plane
What forces must a black box be able to withstand?
3400G 500lbs weight from 10 ft 1100 degrees for 30min 260 degrees for 10 hours 30 days in water = 20000ft 30 days in salt water
When do CVR operate?
From start of first checklist and retain last 30mins of recording
How long must the FDR record for?
From time aircraft moves under its own power to time it comes to stop and retain last 25 hours of recording
When selector is in AUTO position, which computer is used for EICAS CRT?
Left
When selector is in AUTO position, and the left computer fails which computer is used for EICAS CRT?
Right
What would be in the primary EICAS CRT?
N1
EGT
EPR
What would be in the secondary EICAS CRT?
N2
Fuel Flow
Oil quantity, temp and pressure
What does a red message mean on EICAS?
Warning message
What does an amber message mean on EICAS?
Caution or advisory
What does a cyan message mean?
Status Cue
What is a warning?
Requires prompt corrective action (i.e. engine fire)
What is caution?
Requires timely action (engine overheat)
What is an advisory?
Requires corrective action on time available basis. (yaw damper fault)
What does a bell indicate?
Fire warnings
What does a siren indicate?
Cabin altitude, autopilot disconnect, config and overspeed warnings
When do aural warnings automatically silence
When non normal condition no longer exists
When is the take off config warning armed?
When ac on the ground and EITHER engine accelerates towards take off thrust
What conditions will cause take off config warning to go off?
Leading or trailing edge slats/flaps not in take off position
Slat/flap disagrees with flap lever position
Stabiliser position out of TO range
Spoiler lever not down in detent
Position parking brake valve closed
When is the landing configuration warning go off?
Plane below 800ft radio altitude and either thrust lever set to idle with gear up
Landing flaps selected with gear up
What threshold is there for GPWS warnings?
50-2450 radio altitude
When does the overspeed warning go off?
When Vmo/Mmo limits are exceeded
What are the 5 different modes for GPWS warning?
Mode 1 Excessive descent rate
Mode 2 Excessive terrain closure rate
Mode 3 Altitude loss after take off/go-around
Mode 4 Unsafe terrain clearance while not in landing config
Mode 5 Below glide slope deviation
Which modes provide WHOOP WHOOP warnings?
Mode 1 and 2
What is the aural alert and aural warning for mode 1?
Sink rate
WHOOP WHOOP PULL UP
What is the aural alert and aural warning for mode 2?
Terrain
WHOOP WHOOP PULL UP
What is the alert for mode 3?
Don’t Sink
When is mode 4A armed?
After take off climbing through 700ft
When is TOO LOW GEAR warned in mode 4A?
Below 190kts when passing through envelope
When is TOO LOW TERRAIN warned in mode 4A
Above 190 kts when passing through envelope
What happens between 190 and 250 kts in mode 4A?
Envelope extended to 1000 ft
What happens when envelope is penetrated below 154kts in 4B?
TOO LOW FLAPS
What happens when envelop is penetrated above 154 kts in 4B?
TOO LOW TERRAIN
What happens between 154 and 250kts in 4B?
Envelope extended to 1000ft
When does Mode 5 alert go off?
Descent of more than 1.3 dots below glideslope
On the TCAS, what would +02 mean?
Aircraft is 200feet above
On TCAS what would -14 mean?
Aircraft is 1400 below
On TCAS what would a down arrow represent?
Aircraft descending more than 500fpm
On TCAS, what would an up arrow represent?
Aircraft climbing more than 500fpm
What would a amber filled circle represent on TCAS?
TA warning
Aircraft within 40s
What would a red filled square represent on TCAS?
RA warning
Aircraft within 25 s
Apart from aural warning, what happens with RA warnings?
RA pitch restriction appears on EADI
What warnings overrides TCAS warnings?
GPWS
Stall
Windshear
Low radio altitudes
What happens to RA when operating in TA ONLY mode?
They appear as TA’s
How do autopilots work?
Employ closed loop control systems which sense deviations from steady flight path and apply corrections via control proportional to rate of deviation
How would an attitude change about on of the principal axes be sensed?
By the gyro
What does the gyro do in the autopilot?
Sense attitude change about axis.
Process and produces output signal proportional to rate of change
What does the ‘controller’ do in the autopilot?
Compares gyro signal with fixed “reference attitude” and transmits suitable corrective signal to flying control servomotor
When is the autopilot loop closed?
When corrective action is sensed by gyro
How many autopilot channels are engaged during auto land?
all of them (2 or three)
Where does FMS receive data from?
Flight control computer
Air data computer
Thrust management computer
EICAS
What is CADC used for?
Computing IAS, TAS, Mach number, pressure altitude
What are CADC outputs used for?
Automatic speed
Rate of climb/descent
Altitude control
Mach trim control
What do series connected servomotors do?
Move control surface without moving pilot control
What do parallel connected servomotors do?
Move control surface AND pilot control
What is fail passive in autoland?
When 1 of the two autopilot channels fails during approach
Failure doesn’t result in significant out of trim position.
Pilot assumes control of landing
At what height during autoland is localiser and glideslope beam captured during autoland with triple redundancy?
1500ft
At what height during autoland with triple redundancy is nose up altitude auto trimed?
330 ft
At what height during autoland with triple redundancy is flare?
50 ft
At what height during autoland with triple redundancy is flare disengaged?
5 ft
If engine fails during auto thrust, do you need to engage thrust? Why/why not
No.
Reduced thrust is sufficient to ensure obstacle clearance and climb performance in event of engine failure
Radio altitude is displayed digitally below which height?
2450 ft AGL
TCSA symbols can be superimposed on displays for all but what modes?
Plan
Map mode displays track as what?
Magnetic track up
Plan mode is orientated how?
True north
VOR and ILS are orientate how?
Heading up
How would a FMC failure show up?
Map flag when in MAP mode
FMC FAIL on CDU
What does green symbol mean on EFIS?
Engaged flight mode
What does white symbol mean on EFIS?
Present status situation
What does magenta symbol mean on EFIS?
Command info, pointers, symbols, fly to, active waypoints
What does cyan symbol mean on EFIS?
Non active/background info
What does red symbol mean on EFIS?
Warning info
What does Amber symbol mean on EFIS?
Cautionary info, faults, flags, limits, alerts
How is weather displayed?
With EHIS selected to MAP
EHSI with expanded ILS or expanded VOR by selecting WX
How are CDUs connected?
In parallel
What are boxes on the FMC?
Data entry REQUIRED/ESSENTIAL for FMC operations
e.g. gross weight, flight level
What do dashes represent on FMC?
Data entry not mandatory but will assist if entered
e.g. forecast wind
How often is the navigation database updated?
28 day cycle
Where can the pilot check if the navigation data base is current?
IDENT page of CDU
Which pages is used to enter V speeds?
Takeoff page
Where can waypoints be entered
Route page
How do you enter waypoint not in FMC?
Lat and long place bearing/dist/place bearing/bearing
What happens to LNAV and VNAV when using standby navigation?
They are inoperative
What is SAR formula?
TAS / Fuel flow(fuel burn)
What thermocouple probes are used in turbo props?
Rapid response probes
What thermocouple probes are used in turbojet and turbofan?
Stagnation type
How does APU start?
Bleed air from engine
Engine intake air ducted to compressor after which some is bled off
