Structures Flashcards
Best way to prevent the formation of corrosion
Eliminate one of more of the basic requirements
- remove the electrical potential difference within the metals
- prevent the introduction of an electrolyte
Types of metallic coatings
Cladding: pure aluminium rolled onto aluminium alloy
Electroplating: plating cadmium, chromium, nickel or zinc on steel
Metal spraying: aluminium or zinc on steel
Surface conversion coatings
Anodising of al alloys
Alodine 1200, 1120 pens
Chromating of magnesium alloys
Phosphating of steel
Organic coatings
Paint
Jointing compound
Sealant
Cpcs
What are cpcs
Used as a secondary protective coating to the primary protection. Provided by paint, chromate primer, alodine anodising and plating
Oil/wax Base as a means of retarding and preventing corrosion
Types of cpcs
Type a- short term. Water displacing. Thin film. Base
Type b- medium term. Soft film. Common. Good penetrating properties
Type c- long term. Hard film. Low penetrating properties. Top coat.
Handling practices and husbandry
- Maintain adequate cleaning/preservation programme.
- Wear approved footwear and ensure soles are free from embedded abrasive material
- Treat corrosion and failure of protective coatings as often as possible
- Lubricate exposed mechanical parts regularly
- Store removed panels/cooking’s safely to prevent them being blown and scratched
- handle fuel hoses/ equipment carefully to avoid scratching Ac
- drain/ventilation holes are free from obstructions
- fit protective covers
Handling of al alloys
1) wear ppe
Gloves, overalls, steel toe/suitable footwear
2) seeks assistance if handling large sheets
3) clean work area
Storage of al alloys
1) store on edge to avoid damage to surface. But avoid damage to edge
2) take care of protecrivecoating
3) cut from one edge only. Take care to avoid removing identification markings
4) mark out in the most economical way prior to cutting
5) take particular care when inserting sheets into racks. Avoid scratching other sheets
Repair manuals and references
Specific Ac structural repair manual 13,-98
General Ac structural repair manual
General engineering manual
Manufacturers material and fastener data handbooks
Procedure for corrosion removal
Ref:srm 1) remove surface coating 2) consult srm for damage limits Measure corroded area Discuss with supervisor Remove 3) measure damage after removal, repair if necessary 4) apply appropriate treatment to area affected 5) reapply surface coating
Types of surface coating removals
Chemical
Mechanical
Surface coating removal. Non powered mechanical
Abrasive mats(scotch rite) Abrasive paper Abrasive cloth Wire brush Tube brush Pumice powder Metallic wool scrapers
Surface coating removal. Powered mechanical
Al oxide discs Scotchbrite discs 3m radial bristle discs Mediablasters Rotary file (burrs) Linisher (dynafile) Flapper wheel
Ways to measure damage for corrosion removal
Depth garage Optical depth gauge Ndt Fluerscent dye penetrant Eddy current Ultrasonic Radiographic Straight edge feeler gauge
Repair manuals
Specific aircraft structural repair manuals
general aircraft structural repair manual
General engineering manuals
Manufacturers material and fastener data handbooks
To- 1-1a series
To1-1a-1 general manual of structural repair
To1-1a-8 aircraft structural hardware
To 1-1a-9 aerospace metals general data/usage
Ap 101a series
Ap101a-1401-1 reverting process used on Ac
Ap101a-1402-1 aerospace sheet metals and fasteners
General engineering manuals
591
6003-1, Ac and aeronautical equipment maintenance- general orders and procedures
6000-1, Air Force maintenance orders
6005.042-1.1-3 engineering practices and procedures- ac and avionic systems cleaning and corrosion prevention
Identifying American al alloy
Four digit designation Clad bare Temper Thickness Fed specification number Manufacturers name
4 digit designations al alloys
1-99% or higher pure al 2-copper 3-manganese 4-silicon 5-magnesium 6-magnesium and silicon 7-zinc 8-others
Methods of harden ing al alloy
Cold work
Rolling, forging, extrusions
Heat treatments
Solution heat, natural age, artificial age or precipitation heat treated
Hardness designators
Cold- h1- strain hardened H2- strain hardened and partially annealed H3- strain harder and stabilised Heat- 0- annealed W-solution heat treated (unstable) T3-solution HT then cold worked T4 SHT then naturally age hardened T6 SHT then artificially age hardened
Go do we know which sheet to use?
Stated in drawing
Stated in srm/ repair scheme
Characteristics of al alloy sheets
Large Expensive Difficult to handle Sharp edges Easy damaged Major load carrying member
Storage of al alloy sheets
Store on edge to prevent damage to surface, but avoid damage to edge
Take care of protective coating
Cut from one edge only- don’t cut off identification markings
Mark sheet in most economical way
Take care when inserting sheets into racks to avoid scratching other sheets
Handling precautions for al alloy sheets
Ppe to be worn. Gloves, boots, overalls
Seek assistance if handling large sheets
Clean work area
Sphere of influence is what
5d
The area effected by the clamping force of each installed rivet
Edge distance?
2d minimum, specific limits in srm.
Distance between the centre of a fastener and a edge of the structure
What’s the pitch?
Distance between adjacent rivers centres in the same row. Commonly 4d
Transverse pitch of spacing?
Distance between the centres of rivets in rows. Commonly 4d
Clearence still does what
Allow for river expansion in the hole
Prevents burrs
Prevents hold damage and skin by killing
Prevents the protective coatings being removed on rivet installation
Drilling aids
Drill blocks
Bushings
Types of reams
Hand
Machine
Pilot holes-
Pre drill-
Used to locate new holes
Used prior to drilling final or clearance
Flush fasteners used where
Aerodynamically smooth skin surface is required
The fastener head may interfere with adjacent structure
Methods of flush fasteners
Countersinking
Dumpling
Why would u use countersinking
Used on thicker material Quick and easy Cheap Used where dimpling is impractical or not possible Cons-weakens material strength
Factors effecting countersinking
Diameter of fastener head
Height of the fastener head
Angle of fastener head
Dimensions of fastener head can be found in Ac srm, 6005.001-1 or manufacturers fastner handbook
Common countersinking cutting bits
Multi fluted, un piloted
Piloted
Microstop
Things to note about multiflute not and piloted csk bit
Mfb-less likely to chatter because of the many cutting faces
Piloted- uses the pilot to guide the cutter, helps to keep concentric
Things to note about microstop countersink
Adjustable to depth increments of 0.001”
Gives accurate depth control
Negates requirement for frequent stops to check countersink depth
Material thickness limits for countersinking can be found where
Ac srm
Snap 6005.001-1
Dumpling used when
Also known as what
Form countersinking
Thinner material
Used where cut countersinking is impractical or not possible
Gives greater shear strength at fastner joint
Things to be aware of when dumpling a piece of material
Male and female dies match and are the correct size
Dumpling pressure is correct, otherwise causes warpages
Dumpling pilot hole is correct dimension. Critical to ensure the simple is concentric to the hole
Types of dimpling
Coin
Radius
Formed rivet terms
Manufacturers head
Shank
Shop head or tail
Grip=
Allowance=
GL= same as the material thickness
A=protruding length of the unformed rivet required before forming. Normally 1-1.5d
D=rivet shank dia
Total rivet length =
Grip + allowance
Shop head dimensions after riveting
0.5d
Head shapes
Countersink
Universal
Solid rivet identifications
A dimple- ad 2117
Dd-double dashes 2024
Solid rivet part numbers
An 426 ad 4-5
Ms20470 ad4-5
Catalogue method Headstyle -426 countersink, 470 universal Alloy designation Diameter in 1/32 Length in 1/16
Methods of forming
Hand rivet
Squeeze rivet
Reaction rivet
Reaction rivet
Rolling
Pneumatic air hammer
Snaps
Dollies or bucking bar
Solid rivet faults
Cut head Sheared head Open head Damaged skin Snap damage Cracked shop head Formed between skins-0.003” or less is ok Cocked head-0.002 Opened edge-0.010 Under/over formed shophead Offset shophead
Servicae shophead dimensions
- 3-0.5d
1. 4-1.5d
Safety precautions when operating a snap
Don’t operate fun without safety spring fitted on snap
Disconnect air supply when removing or replacing snap
Wear ear protection
Prior to riveting shout a warning to inform others of hazard
Always have a snap on rivet or wood when operating the gun
What is a blind rivet
When is it used
Advantages
Rivet that can be fitted when access from only one side is possible
- when access is no longer available due to further construction
- when it would not be cost or time effective to gain access to use conventional fasteners
- fitted blind or from one side
- fitted by one person
Blind rivet substitution.
Not a direct shbsititute forsolid rivets. Used only iaw ac srm(-3) and 6003-1 substitution chart
Blind rivet terminology
Mandrel or stem Driving anvil Locking ring Tail or bulb Body or sleeve
Generations of blind rivets
Pull thru-cherry pull thru
Friction locked-self plugging. Tucker pop
Mechanically locked, self plugging- huchloks, cherryloks, Olympicloks.
Self plugging mechanically locking mandrel bulged type- cherry max, huck clinch, huck max
RNZAF blind rivet policy
Laid out in NZ ap 6003-1 leaflet d1 Tuckerpop Olympic lok Cherry max Cherry pull thru Huckclinch/huck max Huck blind bolt & jo bolt (heavy duty structural fastner)
How to get correct length for grip length for blind bolt
Grip length gauges
Grip length chart
Cherrymax/ huck clinch nominal and oversize indicators
Gold driving anvil-nominal
Silver driving anvil- oversize. Oversize is 1/64” bigger than the actual shank dia stated
Tuckerpop identification
AGS2051630BS
Ags2051-rivet type, material headshape
6-dia in 1/32”
30-rivet length in 1/100”
Bs-breakstem
Cherrymax identification
Cr3213-6-5
Cr-cherrymax rivet
3213-material, nom/over, headshape
-6-dia in 1/32”
-5-grip length in 1/16”
Cherrymax tooling
Hand
Hydraulic hand
Pneumatic hydraulic
Huck clinch identification
Hc3213-6-5
Hc-huck clinch rivet
3213-material nom/oversize
-6-dia in 1/32”
-5-GL 1/16”
Headstyles for jo bolt
Made of what alloys
Hexagon protruding bead
100* flush head
100* flush billable head
Steel and titanium alloys
Installation inspections for jo bolt
Looseness-checked with driving tool nose adapter, torque wrench
Head flushness- no more than 0.010”
Break off limits-go/no go gauge
Gaps under head-0.005” + reject, 0.004” around 40% of circumference or less=acceptable
Collar inspections-where possible
Structural fasteners in rnzaf
Jo holy
Huck or cherry blind bolt
Blind bolt identification
Ms90353-06-05
Ms90353-pn, head shape, material, nom/over
- -double action, S single action U unimatic
06-dia in 1/32”
05-GL in 1/16”
What does the green dye on a blind bolt indicate
Single action installation
Lock bolt identification
Pin- NAS1466-5
Collar-NAS1080-6
NAS146-pn, material, head shape, bom/over, stump/pull thru type
6-dia in 1/32”
5-GL in 1/16”
NAS1080-pn material
6-collar dia in 1/32”
How do you inspect a lock bolt
With a go no go gauge
Types of hi loc pins
Hi lox Pin
Hi tigue pin
Hi tigue pin fatigue resistance benefits
Burnishes the hole Preloads the hold Cold works the hole Sizes the hole Protects surface coatings Lowers the installation loads
Hi loc pn identification-part numbers
Pin-
HL50-6-6
Collar-HL90-6
HL50-pn material bead shape nom,over HLT=hi tigue
6-dia in 1/32”
6-GL in 1/16”
HL90-PN material
-6-dia in 1/32”
Hi loc identification-head markings
Pin-
HL18-6-6
CollarHL70-6
HL18-pn material, head shape, nom/over, HLT-hi tigue
6-dia in 1/32”
6-GL in 1/16”
hl70-pn material
6-dia in 1/32”
What is the preferred pin fastner for general repair work in the RNZAF during design of modifications and repair schemes
Hi lock
Ac loads
Aerodynamic loads
Inertial
Concentrated
Engine
Types of composites
Ceramic
Fibre reinforced plastics
Types of FRP
Glass fibre
Carbon
Aramid/Kevlar
Boron
Alternatives to al alloy
High strength steel alloys
-carbon
Stainless
Molybdenum
Titanium alloys
Magnesium
Types of bulkheads
Structural Pressure Fuel Fire Cantered
Typical damage to Ac structure
Warpage Fatigues Oil canning Buckling Corrosion Impact damage
Typical damage to Ac composite structure
Substructure damage Voids Ingress of water and absorbsion Disbonding Delaminatiln Barely visible impact damage Cracking/brittle fractures
Methods of ndt
Magnetic particle detection Ultrasonic Fluescent dye penetrant Visual Eddy current Radiography
3 conditions needed for corrosion to exist
Electrical potential difference between anode and cathode
Metallic connection between anode and cathode
Continuous liquid path (electrolyte)
Factors influencing rate of corrosion
Type of metal Heat treated Grain direction Anode and cathode surface area Presence of electrolytes and degree of acidity Salts Temperature Mechanical stress Fatigue
Corrosion prone areas-accessible
External skin Engine inlet Engine exhaust Wheel wells/landing gear Battery compartments/cents Lavatories/food service areas
Types of forms for transparent plastic material
Simple curveformjng
Compound curve forming
Types of compound curve forming
Stretch forming Mal and female die Vacuum forming without forms Vacuum formwith a female Sawing
What do you drink a plastic transparency with
Unibit for windshields and windows
Repair of windows/windshields
Temporary-fly to a location where it can be replaced. Stop drill with no 30drill. No40 half inch from the edge
Permanent-stopdrill no30. Hypodermic syringe and needle to fill the crack with ethylene dichloride
How are acrylic plastics joined together
Ethylene dichloride
Types of construction
Integral Bonded Sandwich -honeycomb -end grain bulsa -plastic foam
Defects for laminated glass
Scratches
Shattering
Delamination
Cracking
Defects for plastics
Scratches
Crazing
Cracking
Distortion
Ac locations using reference line sys
Fs-lengthways from a reference point along the fuselage
Ws-measured along the span of the wing with zero the centreline of the fuselage
Bl-left or right of the centreline of fuselage
Wl-measurement of height from horizontal line fixed below the bottom of the fuselage
XYZ-longitudinal,lateral,vertical axes as xyz and is identified by the manufacturer
Define skin Frame Former Stringer Bulkhead
Smooth outer covering of the af
-transverse structural member, provides aerodynamic shape and rigidity
Lighter than a frame
-a long continuous memberthat assists skin load carrying to other structural members
Major transverse membersin the fuselage or Wing and other structure
Lightening hole. Define
Longeron
Stringer
A hole in a member to decrease weight with strength maintained by flagging around the hole
Main longitudinal structural member. Heavier than a stringer
A long continuous member hat assists skin load carrying to other structural members
Stiffener
Doubler
Normally a strip or beam attached to a sheet to resist load normal to the surface. Short component used to stiffen a localised area
A piece of sheet or strip placed against Ac skin to provide stiffness it additional strength
Cantilever construction
Spar
Cap
Boom
Supported internally by structural members assisted by the skin
The main structural span wise member of an aerofoil
The longitudinal member atthe top and bottom of a beam often called a boom
Longitudinal structural member
Web
Rib
Vertical member of a beam, spar or other length of a wing or fuselage providing strength necessary to resist shear stress and keep upper and lower booms apart
-structural crosspieces combining with sparks and stringers to make the framework of wings, ailerons, elevators, riders and stabilisers
Nacelle
Cowl panrl
Fairing
Any auxiliary structure that encloses the power plant or other equipment
- surrounds the power plant or other equipment circumferentially and improves airflow
- a smooth covering over a joint or a junction in an Ac structure providing a smooth surface for the airflow reducing drag
Access panel
Structural/stressed panel
A seperate or distinct portion of the surface of an Ac structure earily removed
-similar to access panel but more substantial design and iaw mm or srm ay needyk Be fittedprior to Ac movement or jacking
Fillet
Radome
Aerodynamic fairing giving radius atthe junction of two surfaces
-protective covering and aerodynamic fairing overtaxation antenna
Impact damage to composite materials
Substructure damage Voids Water ingress and absorption Disbonding / delamination Barely visible impact damage Cracking/brittle fractures
Classes of structural damage
Negligible
Repairable
Replacement
Ac inspection types
Zvin
Gvin
Corrosion
Inspection tooling equipment
Light
Magnification
Mirrors
Function of ndt
Method we are able to use to detect flaws without affecting the serviceability of the material
Define corrosion
Deterioration of metals that result from an electro chemical reaction between a metal and its environment. Corrosion occurs due to the tendency for metals to return to their natural state
Three conditions that must exist for corrosion
Difference in electrical potential between anode and cathode
Metallic connection between anode and cathode
Continuous liquid path
Factors that influence corrosion
Type of metal Heat treatment Grain direction Dissimilar metals Anode/cathode surface area Presence of electrolytes and concentration Salts Oxygen Temperature Mechanical stress Fatigue Length of exposure
Corrosion looks like- Al and al alloys Magnesium alloys Iron/steel Copper alloys Cadmium Stainless steel Titanium
White-grey powdery particles White-grey powder fluffy particles Reddish brown scale Blue/green powdery particles White powder deposite Red brown or black stain No visible corrosion at low temp
Accessible forrosion prone areas
External skin areas Eng Inlet Eng outlet Wheel wells and landing gear Battery compartments and vents Lavatories and good service areas
Why corrosion of lavatories and good service areas
Organic materials are highly corrosive
Food waste traps water
Disinfectences are corrosive
Inaccessible areas corrosion prone
Electronic equipment Welded areas Fuel tanks Control surface recess Piano hinges Bulge areas Landing gear boxes Eng mount structure
Ac sealants do what
Aid structural integrity
Contain vital gases and liquids
Prevent the ingress of damaging liquids and gases
Sealant type for each application is contained in what publication/s
Ac srm.
Authorised sealants are listen in the nzap 6005.009-1
Sealant construction is made of what compound
Two part polysulphide rubber compound and made to various different specifications
Sealant part number
PR1440GB2
Product number G-Increased soluble chromate content. Helps prevent corrosion B-method of application A-brushable B-sealant gun/spatula C-faying surface sealant sprayable 2-application time in hours
Reliving sealants and adhesives?
Condition of container -leakage, corrosion, degradation Condition in container -separation,layering, settling Application of properties -lumps, foreign matter, viscosity Drying or cure time Appearance
If yes, extend by one half of initial assigned shelf life. 591, 7.17
Non extendable shelf life of sealants
- Not been stored in a controlled temperature environment
- Products marked with an “N” in their relief code column
- Locally purchased products
- Those is aerosol containers
- Those with no DOM
Surface preparation sealants
Remove old sealant using a specialist type scraper
Thoroughly clean and degrease area
Mask around area to be sealed
Sealant CHeck prior to mixing
- Self life
- separation of contents that may prohibit a homogenous mixture being achieved
- Degradation of container
- discolouration of Base compound or accelerator
- hardness or tackiness
- leakage from container
Sealant application methods
Nozzle
Polythene tune
Spatulas
Two part sealants are mixedhow
Iaw instructions on the semkit cartiridge
General instructions
Sealant handling precautions
Avoid eye contact Avoid skin contact Avoid breathing vapour Ensure adequate ventilation Store sealants correctly
