m11.2 Flashcards
what is PSE
principle structural elements- part of the a/c that contributes significantly to carrying flight and ground loads
flight limit loads
the maximum loads expected in a service
ultimate limit loads
flight limit loads multiplied by a factor of safety
where can criteria for structural requirements be found
CS-25
What are the 5 types of stresses
1- tension
2- compression
3- torsion
4- shear
5- bending
whats special about bending
it is a combination of tension and compression
what are the three structural categories
1- primary structure
2- secondary structure
3- tertiary structure
secondary structure
less prone to weakening, wing ribs stringers etc
tertiary structure
lightly stressed elements, fairing fillets
what is fail safe
relies on duplication of certain structural members, if one fails the other takes on the load
what is the disadvantage of fail safe
the additional weight
what is safe life
- based on predicting how long a structure will last
- by submitting it to stating and dynamic load testing or fatigue testing
what be calculated by using fail safe
max cycles, operating hours
what is damage tolerance
uses static and dynamic testing to show the structure can withstand even higher loads than required
when is damage detected for damage tolerance
during routine inspection intervals
what are the 5 main structural units
- fuselage
- wings
- stabilizers
- flight control surfaces
- landing gears
what are the reference planes
vertical, horizontal and longitudinal planes
how many major zones are there
8
what is zone 100
lower fuselage
what is zone 300
empennage
what is zone 500
left wing
what is zone 400
power plants and struts
how are sub major zones identified
the second digit of the number code
what is zone 800
doors
how are sub major zones on the right identified
even numbers
what is zone 700
landing gear and LG doors
how are zones identified
the 3rd digit of the number code
what is a body station or fuselage station
a vertical plane at a right angle to the body centreline
what are buttock lines
vertical planes parallel to the body centreline
what is buttock line 0 also known as
body centreline
what is the abbrevieation for left body buttock line
L BBL
What are warterlines
horizontal planes at a right angle to the body station and buttock lines
where can the numbering for a/c stations be found
chapter 6 amm
what is hoop stress
axial and circumfrencial stress that takes place in a cyclinder
what is used to prevent loss of air during pressurisation
bilge like valves
what is fatigue
the effect of cyclic or alternating loads on structural components
where are drain holes located
various positions on the lower fuselage
when would the bilge valve be open
when the cabin is depressurised
what are vent pipes used for
vent flammable vapours
what are ram air inlets and exit points used for in terms of ventilation
to enable a full flow of fresh air
where are ventilation requirements found
CS-25
what are LRUs
line replaceable units
how must LRUs be designed
to allow for quick fit and removal
what 2 things should be done after a lightning strike
general walk around inspection
find signs of damage through detailed instruction
what is direct damage
surface burns
metallic distortions
what is indirect damage
damage to the electrical system
how big are holes from normal lightning strikes
3mm
how big are holes from high intensity lightning strikes
6mm
what are the most common areas for lightning strikes
fuselage nose section
trailing edges
extremities of the wings and stabilisers
what is bonding
the act of joining 2 electrical conductors together to bring them to the same potential difference
what is grounding
the process of connecting conductive objects to either a conductive structure to complete a circuit
what are the reasons for a/c bonding
- minimise radio interference
- eliminate fire hazards
- minimise the damage to the a/c
- provide low resistance return path
- provides shielding
conditions for grounding
grounds must be separated
no more than 4 studs per terminal
dual grounds must be in fuel vapour areas
what are the 2 types of bonding
direct
indirect
what is direct bonding
done by exposing the mesh and mounting the equipment directly onto a conductive path
what is indirect bonding
achieved by exposing the mesh and installing a bonding wire and connector
bonding resistances should not exceed
0.025 ohms
what are frames/formers
lateral fuselage members that give cross sectional shape
what are longerons
main longitudinal member of fuselage, that take primary bending loads
what are bulkheads
these give shape, but are used to close of or partition an area
what are used to connect stringers and fames
clips or cleats
what are stringers
smaller and lighter longerons that act as stiffeners. they also assist the sheet materials to carry loads along there length
what are struts
load bearing components, that handle compression forces (aluminium/composite)
what are doublers
these are additional sections or material used to reinforce areas of skin that need more strength
what are some doublers also known as
crack stoppers
what are ties
also known as tie rods or tension members, to prevent excessive deformation
what are ties usually made from
steel or titanium
what is the floorboard construction
honeycomb composite, screwed down by nut clips
describe the truss type construction
- members like beams, struts, and bars
- often covered with fabric
- constructed with steel tube welded together
what happens to floorboards in wet areas
they are sealed to prevent corrosion
what are the 2 types of fuselage construction
- truss type
- monocoque type
what are the 2 classes of monocoque construction
- True monocoque
- Semi monocoque (more common)
true monocoque
uses formers and frames
but the skin carries the primary stresses
semi monocoque
loads are shared between skin and framework
also known as stressed skin structure
types of anti corrosion surfaces treatmeants
painting, anodising, sealants
corrosion protection methods
cladding and plating
what does a wing construction consist of
main spar
rear spar
formers called ribs
false spar
how are both wings attatched to each other
via the wing box
what is the wing box designed to do
support the wing and is supported by a keel beam
3 types of surface protection
pre-treament
paint coating
special coating
types of pre treatment
anodising
chromating
2 types of paint coatings
primer- increases corrosion resistance
top coat protects the layers of primer
what are the 2 types of special coatings
type 1 and type 2
type 1 special coating is…
water repellent, made from silicone free materials
type 2 special coating is…
heavy duty corrosion preventative
what are the 3 methods of exterior a/c cleaning
1 wet washing
2 dry washing
3 polishing (hand/mechanical)
what is a wet wash used for
removing oil, grease, carbon deposits as well as most dirt apart from corrosion and oxide films
what is a dry wash used for
to remove aircraft film, dust, dirt or soil.
dry wash materials are applied with spray, mops or cloth
what is polishing used for
this can restore brightness/colour to painted and unpainted surfaces
normally done after the a/c has been cleaned
where can you find recommended cleaning solvents
relevant maintenance manual/COSHH/MSDS
what materials can experience hydrogen embrittlement
some steels and titanium
why must undiluted solvents not touch acrylic windows
crazing may occur
when must snow and ice contaminated areas be washed
with clean water asap after exposure
what are windows washed with
soap or a mild detergent in warm water
for interior cleaning aids, why must they be applied in small amounts
prevent soaking the fabric or padding
what must be done before checking the position or angle of main components
a/c must be jacked and levelled
what must be used when trying to level an a/c
a plumb bob, hung from the ceiling of the a/c
equipment for alignment checks can be found in
the manufacturers maintenance manual
alignment checks include
wing dihedral angle
wing incidence angle
verticality of the fin
engine alignments
symmetry check
horizontal stabiliser incidence
what can be used to check dihedral
a straight edge and inclinometer
what is used to measure symmetry
steel tape and a spring scale for equal tension
