Airframes Flashcards
focus on the airframe, construction, power, controls
What are the Primary Controls?
Aerilons
Elevators
Rudder
What are the 4 forces?
Thrust
Drag
Lift
Weight
Types of construction
Truss - old school.
Monoqucue - No internal framework. Skin provides structure. Airliners
Semi Monoque - Mix. Does not have internal cross members - uses Longerons and Stringers to strenghen. GA today
Describe parts for Truss construction
Longeron - runs the length
Diagonal Cross Bracing -
Vertical Structural Members
Describe parts for Monocuque construction
Skin - provides structure
Former -
bulkhead -
Describe parts for Semi Monocuque
Skins - usually alumnin alloy
Longeron -
bulkhead
Stringer
Key contructions elements for wings
Ribs - front to back - provide wing shape
Spars - length - provide strength.
Skin - usually alumimin alloy
Stringer - provide rigidity to the skin
Wing strength options
Cantilever - does not use struts
Semi-cantilever - uses struts
What is the tail called?
Describe parts.
describe construction methods
Empenage
Horizontal Stabliser
Verticial Stablisers
Ribs
Strings
Spars
Skin
Describe Airframe integrity ( construction type and possible damage )
Aluminium - Damage will show as corrugation, or rippling.
Also Rust.
Composite - suffer more from distortion. Look for rippling, affected by heat.
Fabric - damage shows as tears. Cracking in paint can show a possible problem underneath.
Describe typical direct action, oleo
pneumatic strut.
Gas Pressure at the top.
Oil Pressure at the bottom.
Consists of
Outer Cylinder
Piston Support
Inner Cylinder
Metering value ( tapered )
As the wheel is pressed up, the inner cylinder slides up, displacing the oil - which is metered due to the tapering
What is a torque link on a nose wheel?
On the nose wheel strut.
Prevents the inner cylinder from rotating
How do brakes work?
Usually disc brakes and hydrolic.
Pressure is transmitted to the slave cylinders - which pushes the hydrolic fluid compressing the brake pads onto the Rotor
Name the secondary flight controls
Vertical/Horizontal Trim Tabs
Flaps
Spoilers
What does it mean to say controls are aerodynamically balanced?
The controls are designed to reduce the effort on the pilot to move controls.
Name 3 examples of aero dynamically balancing
Insert Hinge
Horn Balance
Balance Tab
What is Flutter?
Happens when the airflow causes the wing to change direction faster than the control surface ( aileron )
Usual cause is when the hinge point is forward of the CG
NOTE: If the hinge point is behind the CG/mass balance no mass balancing is required.
the two ways to reduce/remove Flutter?
More rigid wing structure
Mass balance the control surface
CG must be forward of the hinge point to mass balance
Ways to mass balance?
Easily accomodated on:
Inset hinge
Horn hinge
For others it must be placed outside the control surface
4 Ways to reduce pressure on controls?
Not triming, ways in construction to reduce pressure
Servo Tab/balance/control tab - flight control moves the tab, which uses airflow to move the main surface.
Horn style hinge - Part of the control surface protrudes upwards in to the air flow
airflow gap - the hinge allows air to flow over the top of the control surface.
hydrolic controls - uses hydrolics instead of cables. And techniques such as jackscrews
Which way to the following move?
Trim Tab
Servo/balance/control tab
Anti-Balance Tab
Trim Tab - control independently.
Moves opposite to control surface ( the control surface moves to neutral again ).
Servo/balace - moves against the direction of the control surface. Reduces required stick force.
Anti-balance tab - move in the same direction as the control surface
Increases required stick force. Used to make controls heavier.
What control surfaces have tabs for trimming?
Ailerons - in GA, usually fixed. required mechanic
Elevators - pitch trim. All aircraft. Large airlines may adjust full elevator surface.
Rudder - yaw trim.
What are the 4 flap types?
Split flaps - old school
Plain - flap forms part of the wing surface when raised.
Fowler - Increases the wing surface ( airliners )
Slotted - allow airflow through. ( GA )
What are spoilers?
Name the 3 uses
Create drag.
Air brakes ( used symetrically ) - allow descent without speed increase
Roll assist ( used asymetrically )
Ground ( used on ground ) - to prevent the wings creating lift.
Why do alierons move different degrees?
Called differentail ailerons.
This is to prevent adverse aileron drag. ( opposite yaw )
Which results in the upper wing having more drag, and slowing - therefore yawing in the opposite direction.
What causes adverse yaw?
Deflections means that:
Upper wing will have more drag, as alieron is deflected downwards.
Upper wing lift is moved slight backwards ( due to Angle of attach )
Describe the main parts of a fuel system
For Gravity
For Fuel Pump
Not the engine parts - just fuel system.
Gravity
tanks
Fuel selector value
Strainer
Primer
Carbrurator
Fuel Pump
Electric Pump ( start and back up )
Engine driven Pump
Strainer
Primer
Selector Value
Carbrurator
What is octane?
What does it mean when there are 2 octanes? ( like 100/130)
Fuel rating. Higher octane = high anti-detonation
100/130 - means 100 when lean mixture and 130 when rich mixture
What is added to prevent knocking ( detonation )?
And max parts
tetra-ethyl lead ( Tel )
AVGAS - 1 part per 800
LL - 1 part per 2,250
What are the colours of fuel?
MOGAS 91 - Purple
MOGAS 96 - Yellow
100LL - Blue
100/130 - Green
115/145 - Purple
Jet Fuel (Jet A1) - Straw coloured (Light Brown) DO NOT USE
What fuel do Turbine engines use?
Jet A1 / AVTUR
What is Calorific value?
Heat released during combustion per unit mass of the volume of fuel
The highest hydrogen content gives the best.
High is better
What is vapour lock?
Caused when fuel turns to gas and prevents liquid fuel from flowing.
High voliatility = more likely to turn to gas.
What is voliatlity?
Ability for the liquid to vaporise.
Higher is better
What is the freezing point?
The point at which the fuel freezes.
Lower is better
What is the freezing point of AVGas?
-60 degrees c
Which conditions are conductive to vapour locking?
When the outside pressure for the fuel is at the saturated pressure for the fuel
What is the saturated vapour pressure?
Ability for the liquid to vaporise at a given temp.
Ideally lower is better, to prevent vapour lock, however this would lower the volitility.
How do Chlorine and Bromide levels affect fuel?
What are the components of fuel
ISO Octane
Heptane
% of octance is the rating.
What does lead do to spark plugs and what is added to manage the impact?
Lead can cause lead oxide to form on the eletrodes of the spark plugs - resulting shorts.
Ethlyene Dibromide is added to the fuel
What is specific gravity?
Density of the fuel
Compare to water ( specific gravity of 1 ) at standard temp ( 15 degrees C )
Lower is better
How does a battery produce power?
Chemical reaction between 2 different electrodes.
Liquid Electrolyte
Electrons flow from +ve to -ve
What does voltage measure?
How is a voltmeter connected?
The potential difference between 2 points in a circuit. ( electrical pressure )
Across the 2 points to be measured
What is a short circuit and why do we care?
Short circuit means the electricity can flow through a non-designed path.
This usually means it flows ‘faster’ ( with high amps ), resulting in heat.
Which can start fires.
How does a wire fuse work?
A thin piece of wired that is rated for a certain ampage is part of the circuit.
If the amps go up, the wire burns through.
How is battery capacity measured?
What are the units of Measure?
Time to fully discharge at a constant current.
30 ampere hour = 30 amps at 1 hour.
How does a voltmeter in an plane work?
Measures the electrical pressure in the electrical system.
Prior to flight we need to review the ‘off load’ by swtiching on the power and looking.
12 volts if a 12 volt battery is installed.
Difference between Alternator and Generator?
( and advantages )
Alternator
Magnetic field rotates, stator is static
Creates AC
Requires Recifier to turn AC to DC - which is circuit using diodes
Weighs less than a generator
Requires battery power to energise it.
Produces consistent voltage even at low RPM
Easier to maintain.
Generator
Magnetics are static, coil rotates.
Produces DC current.
Does not require a battery to energise.
They are heavier, and generally Alternator is preferred.
How does a Circuit Breaker work?
Key component is the Thermal Element.
If there is excess current, the thermal element will deform, seperating the latch.
Once the current is cut, the Thermal Element will return to orginal position.
Power is re-established by pushing the breaker in.
Main parts of a Circuit Breaker?
Thermal Element
Latch Mechanism
Main Contacts
Control Spring
In a Trip-Free Circuit breaker - there is also a trip free switch.
Protocol for Circuit Breaker popping?
Wait at least 2 minutes, for the circuit to cool.
Push back in.
Continue operations
Report on landing
Cautions
If pops out for a second time DO NOT ENGAGE
Do not hold in manually. In some types this allows the current to flow.
What is a trip free circuit breaker vs non-trip free.
Trip-Free
Means that if the push button is held in electricity will not flow if the thermal element is deformed.
This is due to the Trip-Free Switch - attached to the Latch.
Describe the key parts of battery cell?
How do they make a battery?
Electrodes
Electrolytes ( usually Sulphuric Acid )
Cells are combined in series to make a battery.
What are the postive and negative plates made of?
Positive - Lead Dioxide
Negative - Spongey Lead
Electrolyes - Sulphuric Acid
What happens when a cell discharges?
And what is the EMF at full discharge
Plate faces become coated with a white residue of Lead Sulphate
Cell is considered to be fully discharged when it’s EMF ( Electro Motivate Force ) is reduced to 1.8V
How is a Lead Acid Cell Recharged?
And what is the EMF at full charge?
Connect + to + and -V to -V with a slightly higher voltage.
This removes the Lead Sulphate from the plate face.
Fully charged at EMF of 2.2V
What is Suplhation?
If a cell is left in a discharged state, the Lead Sulphate hardens.
More suplation = lower capacity.
Normal GA battery?
6 cells
Fully charged = 13.2 volts
Fully discharged = 10.8 volts
What are vent valves used for on a battery?
Hydrogen Gas is produced during charging.
Vents allow it to escape
Battery is kept in a metal box, with venting.
What is the off-load and on-load voltage?
Off load means power is on with no load. The volts should be the battery volts
On load. Power on, given load ( from POH ) and the volts should be at the correct level.
What does a low volt light do?
illuminates if the voltage on the Bus Bar drops below a predefined level
What does the anmeter show?
Current flowing to or from the battery.
-ve means from the battery
+ve means to the battery.
This means that -ve in flight = bad.
How many busbars and what do they do?
Two.
Primary
Lights
Pumps
etc
Avionics
Instruments
Avionics
etc
What does the load monitor do?
Shows the load on the circuit
If the alternator is working as expected, what should we see?
Small +ve on Anmeter
Small Load ( assuming everything else is off )
What does the Anmeter do?
It is connected between the alternator and the battery.
It shows if energy is going from the battery ( -ve ) or Into the battery (+ve)
Steps when Anmeter is -ve?
You are using battery
Check all circuit breakers
Turn off non-essential equipment
If fully deflected, indicates alternator failure - turn off alternator switch
Land as soon as possible
Steps when Anmeter is fully +ve?
Indicates over charge.
Alternator should have been automatically disengaged.
May get high voltage indication if available.
Avionics Off
Master Off
Master On
If everything normal, Avonics on and continue.
Consult the manual.
What does a voltage regulator use?
The Field Coil