Mechanical Systems 1 Flashcards
Define stress
Force applied to cross sectional area of an object.
Stress is the applied force or system of forces that tends to deform a body
Define strain
Strain is the response system to an applied stress when material is loaded with a force that produces a stress which then causes a material to deform
Explain tortion shear bending and hoop stress
Torsion: twisting force
Shear: try to slide a body apart
Bending: 1 side is squeezed and other is pulled apart
Hoop: pressure difference
What are the basic construction members
Ties: purely subject to tension
Struts: members and compression
Beams: carrying loads at an angle takes loads and bending
Webs: members carrying loads in shear. ribs and the skin itself are webs
What is stressed skin
Covers frame with a skin panel which can take tension and compression loads. the skin takes the loads of the diagonals
Highlight the characteristics of a monocoque construction
Relies entirely on skin strength to carry loads, no internal bracing except frames, formers and bulkheads
Briefly explain geoditic construction
Structural members are formed within the areodynamic shape itself
What 2 types of trusses are used in aircraft construction
Warren and Pratt
What is the disadvantage of thin metal monocoque design construction
Can fail when subject to relatively minor dense or creases
Name the 3 secondary purposes of wings
Fuel storage
under carriage attachments
provides means of attaching the flight controls
Highlight the principle of a cantilevered wing
Rib and spar arrangement with external bracing wires and struts
Briefly outline sweepback theory
Only the component of the airflow perpendicular to the leading edge of the wing that affects pressure distribution and formation of shock waves
What are stringers
Rigidly attached to skin all of these structures, stiffening the skin and assisting it to carry loads in the direction of their length
Where would doublers be used
Around doors and windows
What are drag wires
The wires that extend from front spar to rear spa and that are running diagonally from inbound to outbound
What are the 3 Fundamental wing construction designs
Mono or single spar, Multi spar, Box beam/torsion box
What is the function of a spar in wing construction
Carrys static weight of wings on ground
Ultimately takes loads carried by wings during flight
What is the main use of stringers in fuselage construction
Give shape for the attachment of the skin
prevents tension and compression from bending the fuselage
How do radome lighting diverters strips prevent damage
Decrease lighting image and transmitting it to the airframe
During flight what loads will be felt on a cantilever wing’s spar caps
Compressive loads on top, tensile loads on bottom
Name the 4 main methods of joining structure together
Nuts and bolts
Riveting
Welding
bonding
Name the main components of the helicopter transmission system
Main rotor transmission
Tail rotor
Drive system
Clutch
Free wheeling unit
What are the main structural members in the helicopter fuselage
To longitudinal Beams that form primary structure
What forces are helicopter rotor blades subject to
bending and shear
Large centrifugal loads from blades during rotation
What is an aleron station
Is major outboard from, And parallel 2, Is the inboard age of the aileron, Perpendicular to the rear beam of the wing
What are nacelles stations
Measured either forward or behind the front spar of wing and perpendicular to a designated water line
Name Some properties of composite materials
light weight
High strength
Can be molded into complex shapes
Corrosion resistant
Define hardness
Ability to resist cutting, pentration or abrasion
What happens when a metal is cold worked
Increases in hardness and strength
What 2 types of hate treatment are used on aluminum alloys
Solution heat treatment
Precipitation heat treatment
What percentage of carbon is in low, Medium, And hard carbon steel
Low 0.1 to 0.3%
Medium 0.3 to 0.5%
Hard 0.5 to 1.05%
What is stainless steel
Steel with large amounts of caramelium and nickel
How is steel annealed
Heated to just above its critical temperature, Soaked for a specific time, And then cooled
What are the 2 methods of case hardening steel
Carburizing and nitriding
Where would you use inconel metal
Gas turbine engines due to maintaining strength at extremely high temperatures
What is The Matrix of composites
The glue that holds it together
What is the safe life of a structure
Min number of flight hours or flight cycles that statistically should elapse before major failure occurs
When could a structure be closed as damage tolerant
If it can continue carrying the load once a defect has occurred without affecting the integrity of the aircraft structure or safety until scheduled inspection and a repair can be carried out
What are the 4 evolutions of flight controls
Simple mechanical
Hydraulic, Power assisted
hydraulic, Fully powered
Fly by wire
How a cable fitting attached 2 cables
Swag using metal collars pressed onto the cable
Explain the construction of 7x19 extra flexible wire
7 strands, 19 separate wires in each strand
What is a lock clad cable
An aluminium tube swagged over parts of the cable. Causes steel cable to expand a similar expansion rate to aluminum structures
How are cables fitted through pressure bulkheads
Go through a special pressure retaining fairlead to reduce the air leakage around cable
Why would you use a bell crank
To change directions and a push pull rod system
Gain or decrease mechanical advantage
What is a torque tube
Tube which transmits rotary motion
Why have secondary stops
They are used as override stops to prevent stretching of cables and damage to the control system during violent maneuvers
Briefly describe the basic rigging procedure of an aircraft
lock cockpit control into neutral position
Adjust cable tension
Remove system locks
Check/adjust primary stop
Chick/adjust secondary stops
What basic equipment is required for rigging a flat control system
Rig pins
Rigging board
Protectors or Inclinometer
Rigging fixtures
Contour templates
Rulers
Tensiometers and cable rigging tension charts
When must a duplicate inspection be carried out
After any disturbance of a flight control system
What can backlash in a control system cause
Flutter
What prevents the stationary swashplate from rotating with the rotorshaft
Antidrive link
How would you determine whether an access panel was a stressed panel or not
In the aircraft maintenance manual / panel chart
What usually takes the presurisation loads on outward opening cargo doors
Hinges and latches
What a light aircraft windows usually constructed from
Single layer of perplex or polycarbonate
What can cause crazing on a plastic window
Mechanical stresses or the action of a chemical agent
Describe the construction of aircraft interior partitions
Composites, honeycomb materials, very lightweight and non structural (to aircraft)
What aircraft must carry a first aid kit
All aircraft with 10 or more passengers
What aircraft must carry a readily accessible axe
Aircraft with seating capacity of 20 or more passengers
What is the stipulation for the requirement of lifejackets
All flights that cannot maintain more than 1000ft altitude at more than gliding distance from the shore
How many cabin crew should there be on board
1 per 50 passengers
What is portable water
Water suitable for human consumption
How is the portable water system pressurized
Engine bleed air
If the recirculating pump on a recirculating toilet fails can the toilet still be used
Can still be used as a chemical toilet
If waste tank is full in a vacuum toilet system, how is flush cycle prevented
Point level sensor prevents flush cycle if full
How is overfilling of the portable water system prevented when servicing
Excess water flows through overflow fitting
