11.2 Airframe structures Flashcards
what does PSE stand for
principle structural elements
name some examples of principle structural elements
wings, canard, vertical stab, horizontal stab, winglets
what are flight limit loads
maximum loads expected in service
what are ultimate limit loads
flight limit loads multiplied for safety
what are aircraft structural members designed to do
carry load or resist stress
what are the 5 stresses acting on an aircrfat
tension, compression, torsion, shear, bending
structural members are designed to carry what loads instead of what loads
end loads rather that side loads
what are the 3 ways structure is classified
primary, secondary, tertiary
what falls under primary structure
any of the aircrafts framework
name some example of primary structural components
wing spars, engine mounts, fuselage frames, main floor
what falls under the secondary structure
non-primary structural components
name some secondary structure examples
wing ribs, fuselage stringers, aircraft skin segments
what falls under tertiary structure
any remaining structural components
what must you refer to when identifying aircraft structure
AMM, SRM
what is meant by fail safe
duplication of structural members so if one fails there is a backup
whats the disadvantage of fail safe structures
added weight and the concept is outdated
what is the modern concept that is replacing fail safe
damage tolerance
describe the safe life concept
prediction of how long a structure can remain in service until a point of fatigue
what is the safe life concept recorded in
cycles or operating hours
what is damage tolerance concepts
testing of structures
what types of test are used for tolerance concepts
static and dynamic load tests
what are the 5 main aircraft structural units
fuselage, wings, stabilisers, flight control surfaces, landing gear
what are used to calculate primary dimensions on an aircraft
defined zones, reference points, lines, planes
what type of zones is the aircraft split into
major zones, major sub zones, zones
what number are all the zones and what part of the aircraft do they cover
100 - lower half fuselage
200 - upper half fuselage 300 - empennage
400 - power plants/struts
500 - LH wing
600 - RH wing
700 - LG/LG doors
800 - doors
what is used to identify sub major zones
second digit of number code
are the sub major zone numbers odd or even on the LH/R|H side of the aircraft
odd is on the left, even is on the right
what are the zones identified using on the aircrfat
third digit of the number
how is the aircraft zones numbers (e.g top to bottom)
fwd - aft
inb - outb
bottom - top
what do the digits mean when identifying zones
first - major
second - sub major
third - zone
what does BS and FS stand for
body stations, fuselage stations
where does the body station run on the aircraft
vertically at right angle to body centreline
where does the fuselage station run on the aircraft
from the nose of the aircraft
what does BL stand for
buttock lines
what is the buttock line 0
bodies centreline
where are buttock lines on the aircraft
vertical planes parallel to body
what does WL stand for
waterline
where do waterlines run on an aircraft
horizontally at right angles to body stations and buttock lines
what does WS stand for
wing station
what does CS stand for
component stations
what are all the major types of stress
tension, compression, torsion, shear, stress, bending, hoop stress, strain, fatigue
define tension
resistance to forces which pull it apart
define compression
stress that resists crushing forces
define torsion
stress that causes twisting
define shear
stress that resists force that causes a layer to slide over another layer
define stress
material subject to a force
define bending
stress combination of compression and tension
define hoop stress
what cabin experiences when its pressurized (radially and axially)
define strain
ratio of the amount of deformation of material caused by stress
define fatigue
effect of cyclic or altering loads on structural components
what part of the fuselage are drains located
lower half
how is the loss of air during pressurisation prevented
by using bilge like valves
what must aircraft designers consider when fitting components
access panels and how to get components out with ease
what does LRU stand for
line replacable unit
how are cables grouped to make it easier for serviceability
looms
what is the most basic lightning strike protection on modern aircrfat
external metal structure
what is used on composite aircraft for lightning strike protection
metallic paint, conductive mesh
if a lightning strike is reported what must you first do
walk around, find any damage
what 2 types of damage can a lightning strike cause
direct, indirect
what is direct lightning damage
burned surface, or distortion , damage to the structure
what is indirect lighting damage
damage to electrical systems
how big is the scorch mark that a lightning strike usually creates
3mm diameter
how big will a high intensity lightning strike scorch be
6mm or more in diameter
what are 2 signs of lightning strikes
discoloration, damaged rivets
where are the most common parts for lightning strikes
nose, trailing edges, edges of wings/stabilisers
can lightning strikes go through the aircrafts metal structure and cause internal damage
yes
what is bonding
joining two electrical conductors together
what is grounding
electrically connecting conductive objects to either another conductive structure or a conductive return path
what type of electricity can an aircraft be charged with during flight
static electricity
whats the process of electrical bonding
connecting components to ensure the have the same electrical potential
proper bonding will enhance what
protection of equipment and passengers
when installing grounds, what conditions apply
.separated AC/DC/shields
.no more than 4 terminals in 1 stud
.dual grounds installed in fuel vapour areas
what are frames also known as
formers
what is the use of frames/formers
give shape and strength
to overcome the strength problem on monocoque construction what is used
semi-monocoque
whats the purpose of bulkheads
give shape to the fuselage
whats the purpose of bulkheads in the engine
seal/isolate fire zones
what is a longeron
main longitudinal member of the fuselage
what is a stringer
smaller and lighter longeron
whats used to attach the skin to the frame
clips or cleats
what are doublers used for
reinforce areas of skin that require extra strength
whats another type of doubler
crack stopper
what do struts and ties do
provide structural integrity and airframe strength
what force do struts take
compression loads
what forces do ties take
tension
what are ties usually made from
steel or titanium
what are floorboards made from
honeycomb composite
what are the 2 general fuselage construction types
truss type, monocoque type
whats the main advantage pf semi-monocoque fuselages
can withstand more stress and still hold together
what is a truss type fuselage usually covered with
fabric
what are semi-monocoque fuselages primarily made from
aluminium alloys
how can a skin be joined together
bonded or riveted
what does an empenage consist of
horizontal and vertical stabiliser
what do engine nacelles do
house engine components
what is used to bind skins together and structural components
rivets
why are blind rivets used
to rivet areas that cant be accessed by a block
what is used for joining on aircraft when high strength is needed
bolts
whats a substitute to bolts when strength isnt needed
screws
what is used for bonding, especially on composites
adhesive
what does surface protection prevent
corrosion, fluid damage, erosiom
what are the 3 groups for protective treatment
pre-treatment, paint coatings, special coatings
what is done in pre-treatment of surfaces
de-greasing, applying a pre-treating substance
what are the 2 pre-treatment subsatnces
anodising, chromating
what does anodising do
forms oxide coating to increase surfaces performance
what does chromating do
produces protective oxide film
what colour finish is chromating
browny-yellow
whats the reason for applying paint to an aircraft
protect skin from corrosion
what is paint coatings divided into
primer, topcoat
what are the 2 types of special coating
type 1, type 2
what does a type 1 special coating do
water repellent
what does a type 2 special coating do
heavy duty corrosion preventative
what are the 3 methods of cleaning the exterior of the aircraft
wet wash, dry wash, polishing
what can polishing be broken down into
mechanical, hand
when is a wet wash used
to remove oil, grease, or carbon deposits
when is a dry wash used
remove aircraft film, dust and small dirt
why do we polish an aircrafts exterior
restore brightness/colour
before commencing cleaning what musty you do with panels
ensure they are closed and sealed
what must not come into contact with acrylic windows when cleaning
undiluted solvents
when an aircraft flies in areas prone to slat hows it washed
with water after flight
after an aircraft wash what must be done with the windows
wash windows with soap or detergent in warm water
what areas are prone to corrosion in the aircrafts cabin
galleys, toilets, drains
why must an aircraft all be in alignment
to ensure it flies correctly
what is the alignment check with on aircraft
transit and plumb bobs or theodolite and sighting rods
on small aircraft what is used for measuring
steel tape
what is used for measuring larger distances
spring scale
how are dimensions of a large aircraft measured
marking the aircraft on the floor with chalk then using a plumb bob
