Kevin's Questions Flashcards
What is the major zonal area of the left hand wing?
500
Define damage tolerant design
The damage tolerance principle requires that any aircraft damage is detected, and repaired before the strength is below a minimum level.
Define Fail-safe system
The fail-safe design principle uses multiple load paths to ensure structural integrity.
If one load path cracks completely through or sustains accidental damage, the remaining load paths carry the additional loads
A wing leading edge is what type of structure?
Secondary structure
'’The secondary construction generally gives the aerodynamic shape to the
aircraft construction.’’
Where would you find information on leveling an aircraft? (ATA chapter)
ATA chapter 08 - leveling & weighing
How is the radome of an aicraft protected against lightening strikes?
Glassfibers, both woven into cloth and packed into loose mat and roving, have been reinforced with polyester resins and used for radomes,
Aluminium wires may be woven in
What is a longeron?
A longeron is similar to a stringer.
A longeron is a longitudinal member running the full length of the fuselage
(Stringer is like a smaller longeron)
What is shear stress?
A shear stress tries to slide an object apart.
What type of structure is widely used on modern day commercial aircraft?
Semi-monocoque
What’s the purpose of fiberglass barrier between carbon-graphite and aluminium
A barrier, such as a layer of fiberglass should be used to prevent a galvanic potential between the carbon/graphite and aluminium.
This will occur as lightning strike protection
A fine aluminium screen may be laminated to carbon/graphite and a layer of fiberglass must prevent a galvanic potential
What parts of a semi-monocoque structure protect it against bending forces
Longerons and stringers protect against bending forces
What surfaces assist the aileron at the beginning of a turn
The flight spoilers on the wing with the up-aileron automaically extend to assist
Why are slots not used on high speed aircraft
What is the name of the trailing edge of the wing that acts as ailerons and elevators?
Elevons
Frequently used on delta wings (picture)
Spoilers are used assemetrically with what control surface
ailerons
What way do the control surfaces move if you move the control wheel to the left
Aileron on the left side moves up and spoilers do also to assist
Aileron on right side moves down slighly
(differential ailerons)
What is a canard and what control does it give the aircraft
Any aircraft that has the equivalent of two lifting surfaces, instead of the conventional horizontal stabiliser that provides a down load, can be classified as a canard
The canard is the forward surface and frequently also a control surface
What direction does an anti-servo tab move in relation to the control surface
Same direction
(Anti-servo tab is the same as anti-balance tab)
What is the function of flaps and leading edge devices
Leading edge devices (slots and slats re-energise boundary layer) serve to allow the aircraft to fly at high angles of attack (25^) and slow speeds without stalling
Flaps increase the camber of the wing (and sometimes area), allowing a lower stall speed and better lift
(note: slats also increase camber of wing)
What is an anti-servo’s tab linkage connected to?
The fixed end of the linkage is on the opposite side of the surface from the horn on the tab, and when the trailing edge of the stabilator moves up, the linkage forces the trailing edge of the tab up. When the stabilator moves down, the tab also moves down.
A stabilator is designed to pivot about a point where?
This is a single piece horizontal surface that pivots about a point approximately one third of the way back from the leading edge.
High speed flight range of above mach 5 is called what?
Hypersonic
What happens air at supersonic speed?
3 Pressure waves form:
- Normal shock wave
- Expansion waves
- Oblique shock waves
(needs more work)
What happens to the air as it passes through a supersonic venturi? (velocity, pressure, density)?
It is dependent on temperature
Velocity decreases
Pressure increases
Density increases
How do you increase the critical mach number of an aircraft?
Sweep the wings back
As an aircraft moves through a transonic region, what happens to the CP (Centre of Pressure)?
Goes rearward (pushed back by shockwave)
-Cuases a nose down tendancy
What control surface controls about the vertical axis?
Rudder
What type of tab decreases the forces on a control surface?
Balance tab
(Difference between balance tab and servo tab:
Balance tab reduces the force needed to move a primary control surface
Servo tab aerodynamically assists or provides the force for moving a primary flight control
The elevator provides control about which axis?
Lateral axis
Define the mach number
Mach Number = speed of aircraft / speed of sound
Where does an increase in temperature take place in the Air Cycle Machine?
Compressor
'’The compressor increases the
pressure and the temperature of the air to improve the efficiency of the
heat exchanger.’’
What is the purpose of ‘‘chemical milling’’?
Stringers and skin are made from one piece to give it additional strength
Give another name for a Krueger flap
Leading edge flap
State the purpose of aerodynamic balancing
The weight (horn) is ahead of the leading edge and when deflected moves into the wind to help deflect control surface even further
What type of air conditioning system uses a refrigerant?
Vapor cycle system
(Air conditioning system used in older aircraft)
What is the cooling medium used for the heat exchangers in an air conditioning pack?
Ram air
State the major difference between ground and flight spoilers
All spoilers are ground spoilers when landing gear (weight) is on ground.
However, only some spoilers are flight spoilers
What is a cantilever wing design?
A cantilever wing design has no external struts or bracing.
It only has internal braces
What is the purpose of the turbine in the air cycle machine?
The turbine takes away energy from the air, with
which the compressor and cooling (Suction) fan is driven. Due to this, the air will cool off further.
Give an example of lightning strike protection
Bonding strips, screws or grounding lugs fitted between
metallic assemblies.
When are external drain valves open?
External drain valves are always open
What is a canard?
Any aircraft that has the equivalent of two lifting surfaces, instead of the conventional horizontal stabiliser that provides a down load, can be classified as a canard.
The canard is the forward surface, and frequently is
also a control surface.
What determines the speed of sound in a supersonic venturi?
Temperature
'’The speed of sound is determined completely by the temperature of the air
It decreases (Km/h) as temperature decreases ie as altitude increases ‘’
What is the effect of a Sweepback wing?
A sweptback wing increases the critical Mach number of an aircraft
Define damage tolerant design?
Damage tolerant design allows damage to occur once it is inspected and repaired at a set interval before it compomises aircraft safety
What is the structural classification of Nacelles?
Secondary structure
Explain Body Station number?
Measured from in front of the nose of the aircraft parallel to the y-z plane and perpendicular to the floor of the aircraft.
It is measured at some point in front of the nose to the tail and is measured in inches or cm
What is a plug type door?
A a plug type door is bigger than the door jamb it is designed to fit into
What aircraft windows are heated?
Cockpit windows are heated to increase flexibility, prevent ice building up or from fogging over.
What are the 4 functions of a pylon?
What valve controls the air flow to the air con packs?
Flow control valve (Pack valve)
Where does the air from the air conditioning system come from?
Primary source = Engine bleed air
Secondary source = APU or Pneumatic ground cart
What happens when the emergency RAM air pushbutton is actuated?
If the RAM air pushbutton is actuated, the outflow valves open to discharge the cabin pressure and the ram air door opens to allow ram air flow through the cockpit and cabin
(has to be <1 psi differential to be actuated to prevent rapid depressurisation)
How is ground conditioned air fed to the aircraft?
A mobile air conditioning unit or
an air conditioning ground network installed on some airports is used to feed ground conditioned air
What is the advantage of using ground conditioned air?
It bypasses the pack systems so there is no need for bleed air for them to be running (i.e engines + APU dont need to run)
It is more economical
The Pneumatic connection is mainly used for maintenance only
In the air conditioning system, where does the heat energy change to kinetic energy?
Turbine (energy used to drive compressor and cooling fan)
This loss of energy also cools air further
What is the purpose of the turbine bypass valve?
It works in conjunction with the RAM air inlet door to control pack output temperature to manifold
What happens when the turbine bypass valve moves to the closed position and what happens when it moves to the open position?
If turbine bypass valve closes, the RAM air inlet door will open as much as possible ensuring the coldest air temperature is output by pack
If turbine bypass valve is open, RAM air inlet door will close as much as possible producing the warmest possible air from pack system
What is the purpose of the trim air valve?
trim air valves = #zones (cockpit, aft cabin etc)
Adds hot trim air to the conditioned air from the pack system to increase air temperature.
Trim air is directly from engine bleed air
How many trim air valves are installed on an aircraft?
There is 1 trim air valve for every zone of the aircraft
What is the location of a trim air valve?
Downstream of the pack
What is the function of the Air Cycle Machine (ACM) ?
The overall function of the ACM is to improve efficiency of the system
Turbine which drives a compressor and a fan
Compressor increases pressure and temperature to improve efficiency
Turbine converts heat energy from the air into kinetic energy, which cools the air
Cooling dan which draws in air during lowspeed and on the ground
What are the components of an Air Cycle Machine (ACM)
- Turbine (Heat energy to kinetic energy)
- Compressor (compresses air increasing temp & pressure)
- Cooling fan (draws in RAM air on ground and at low speeds)
Where does the pack anti-ice valve prevent icing ? (2 places)
At the exit of the ACM, at the turbine
- The turbine decreases the temperature of the air and it’s outlet can theoretically go below 0 degrees
- Downstream of the water seperator
What kind of a switch is the switch for a pack valve?
(how controlled, how operated)
Electrically controlled, pneumatically operated
Variable switch for pack valve (flow control valve) in the cockpit which has high, low or norm
What component absorbs heat from the aircraft cabin in the Vapor Cycle System?
Evaporator - evaporates refrigerant (Tetrafluorethane /R134A /R12) as it absorbs heat into it.
What’s the purpose of the thermostatic expansion valve in the vapor cycle system?
Regulates the amount of liquid refrigerant (Tetrafluorethane/ R134A/R12) flowing into the evaporator
What is the purpose of the blow out panels on an aircraft?
Blow out panels are fitted in the floor between passenger and cargo compartments in order to prevent excessive differences in pressure occuring between these areas
What component controls cabin pressure?
The Outflow valve(s)
What component prevents cabin altitude from becoming higher than aircraft altitude?
Negative Relief Pressure valve or vacuum relief valve
What position is the outflow valve in during and after landing?
Fully open
It equalises pressure inside and outside cabin
Also, so the aircraft doesn’t have to withstand pressurisation and landing loads during landing
What component sends signals to the outflow valve?
2 electrical motors
AC motor for automatic mode - cabin pressure controller
DC motor for manual mode - switch inside the cockpit
What’s the limit of the cabin altitude during pressurisation.
(VSI) Cabin altitude climb rate = 500 ft/min max
Cabin altitude cruise = 8,000 ft
(VSI) Cabin altitude descent rate = 300 ft/min max
What are the pressurisation indications in the cockpit (3)
- Cabin altitude indicator (max 8,000ft)
- Cabin differential pressure indicator
- (VSI) Cabin altiitude vertical speed indicator (ascent 500 ft/min max, descent 300 ft/min max)
(Also position of outflow valve display/PRESS Refief warning light)
How does the negative relief valve protect the structure?
Equalises a possible negative pressure difference during descent i.e outside air pressure increases faster than the pressure in the cabin
Allows greater pressure outside aircraft into cabin
What components are contained within the safety relief valve?
- Positive Pressure relief valve
- Negative Pressure Relief valve ( vacuum relief valve)
What is the sequence of events if you get negative differential in the descent?
- Negative Pressure relief valve (vacuum relief) will open to add pressure inside the cabin
- PRESS RELIEF warning light will display in cockpit for as long as pressure relief valve is open
What happens when the ditching switch is pressed?
Ditching switch will cause all outflow valves to close prior to landing on water
(It is a guarded switch)
What happens when the cabin altitude reaches 10,000 ft?
An intermittent warning sound will sound in the cockpit if the cabin altitude exceeds 10,000ft
The warning sound can be stopped by pressing the horn cutout P/B on the indication panel
What is the output of an AC generator?
115/200V 3 phase 400Hz 75 kVa (40 - 90 kVa)
What type of electricity is caused by the movement of electrons?
Current electricity is caused by the movement of electrons
How is current created in a self-excited generator?
Generator fields are self-excited
This means that the field current comes from the armature
*Field current is the current supplied to the field windings of a generator or motor to establish the magnetic field for it’s operation.
Where are the electromagnetic poles located on a DC generator?
The frame of a typrical aircraft DC generator has four electromagntic poles
How is differential protection of an electrical system (generator) accomplished?
Two 3-phase current transformers located in the generator
- One reads current to the ground (neutral)
- One reads generator current and current to power consumers
If either is off, this indicates a problem and the generator excitation field is turned off
What is the purpose of the attachment frames on a vertical stabiliser?
The vertical stabiliser is normally bolted to the top centre of special reinforced frames of the tail fuselage section.
The vertical fin is bolted to fitting-brackets to facilitate removal and installation
What type of metal is galvanising used to protect from corrosion?
Some steel parts such as fire walls are galvanised by coating them with zinc
Which aircraft windows are heated?
Cockpit windshields are heated to improve flexibility, prevent ice and stop fogging over.
Cockpit side windows are heated against fogging over.
The acryllic windows must be able to flex in situ because of what quality?
Coefficient of expansion
Which cabin window has a hole in it & why?
There is a small ventilation hole in the inside window to allow adjustment for pressure differences between the inside and the outside window
Also there if outer pane fails, will allow some pressure on the inner window out
What is the purpose of a rib?
Gives aerodynamic shape and rigidity
Why is the wing subjected to torsional stress
Centre of pressure moves along the chord
What is special about a cantilever wing
Does not need any external struts or braces
Only has internal bracing
Where is the centre of gravity in relation to the centre of pressure
Centre of gravity is ahead of the centre of pressure
(gives nose down attitude without engines)
What kind of loads are wings subjected to in flight and on ground
In flight = upper wing - compression
lower wing - tension
Ground = upper wing - tension
lower wing - compression
What components make up an empennage?
The empennage of an aircraft is the assembly of tail surfaces that are used for both control and for stability.
Horizontal and Vertical stabiliser
What are the main structural parts of the vertical stabiliser?
Dorsal fin
Ribs & Spars
Stressed skin
How is the vertical stabiliser attached to the aircraft?
The vertical stabiliser is normally bolted to the top centre of special reinforced frames of the tail fuselage section
What is the purpose of mass balancing flight control surfaces
A mass (or weight) is placed in front of a hinge or control surface.
This gives the surface better stability in flight
Mass balancing is designed to prevent flutter on control surfaces
What flight control surfaces are balanced
All the primary flight control surfaces (ailerons, rudder, elevator)
Where is the centre of gravity on a flight control surface
Hinge line
What causes control surface flutter
Flutter is a vibration of the control surface which is often experienced at high speeds.
It is caused by pressure disturbances over the control surface and can be particularly bad if the control surfaces CofG is not in line with the hinge point.
What is the function of a pylon?
Support the weight of the powerplant and transmit it’s thrust into the adjacent airframe
What is the difference between turbines fitted to a turbojet and a turbo prop
Turbojet engines develop very little torque, therefore turbojet mountings are less robust than turbo-prop engines
Turbo prop engines have to be mounted in tubular sub-frames out in front of the fuselage or wing, allowing plenty of vertical clearance between the propeller and the ground
What’s the primary structure of an engine pylon?
Primary structure of a pylon must carry all loads and serve as a firewall, it is normally made of titanium and steel alloy riveted sheet construction
Secondary pylon structure is normally composite panels
What is the function of a fire wall? (in an engine)
- Prevent entry of combustible material
- confines effect of pneumatic duct and turbine rupture or major leaks
- prevents air from the hot section of the engine core from circulating in the fan case area
- faciliates the effective use of the fire detection system by containing the fire in one area
What is a firewall manufactured from?
Stainless steel
Titanium
Thermoplastics
