6.3.3 Fbric Covering Flashcards
Before fabric covering any component what must be done to the structure
Structure must be inspected, all foreign matter removed and protective treatments must be applied
What are the most stable temperatures for applying fabric to an aircraft
16-21°c and a relative humidity of no more than 70%
What is cotton tape also referred to as
Egyptian tape
What are linin tapes used for
Covering leading and trailing edges and repairs
What is used for stringing
Flax chord
What type of conditions should aircraft coverings be stored
About 20°c in the dry
What must be done to bolt heads and screw heads that would be likely to chafe before covering
They should be covered with tape
How may aircraft fabrics be fitted
With the warp or weft 45° to the slip stream or in line with the slip stream
What are the most common methods of re covering aircraft
- Prefabricated envelopes
- The Blanket method
How should stitching not be done
Seams should never be made at right angles to the direction of air flow
What two types of machine seams are used on aircraft
- Balloon seam
- Lap seam
What is the Balloon seem also referred to as
The French Fell
When would the Lap seam be used
Only when specified for the manufacturer. The Balloon seam(French fell) is the preferred method
What is the main hand sewing method
Overhand stitch
What are the 2 types of hand stitch used for repairs
Herringbone (baseball)
Boot
What should be done to all threads before sewing
A layer of beeswax should be applied
What is boom stringing used for
Deep aerofoil sections
How is fabric usually attached to plywood
It is usually done with dope
When attaching fabric to metal surfaces, other than doping in to place what could be used
Alternatively a thermoplastic adhesive may be used
What does drainage and ventilation provide for fabrics
Minimise corrosion of the structure and rotting of the fabric
What shape are drainage eyelets usually
Oval or circular
How are drainage eyelets applied to the structure
They are doped in to place, however they can also be sewn
What is the purpose of shielded eyelets
Used in marine environments to prevent the entry of sea spray
They must not be used instead of regular eyelets
They must be facing the correct way
What are the 3 methods of inspection panels which are used on wooden aircraft
- Woods frame
- Zip panels
- Spring panels
What are woods frames
A circular or square frame made of a celluloid sheet which are doped on to the fabric cover at required positions
What is the biggest disadvantage of the woods frame
A new patch has to be doped on every time
What are zip panels
Consist of two zip fasteners sewn in to the fabric in the form of a vee. They are used in areas where frequent inspection is required
What are spring panels
Particularly suitable for light aircraft
What method would be used to repair a fabric that has been damaged extensively
If the fabric is damaged extensively it should not be repaired and should be replaced
When should the herringbone stitch be used
Should be used when repairing straight cuts or tears which have sound edges. After the stitching has been completed, 25mm wide serrated tape should be doped over the stitching
What is the other method of fabric repair if the herringbone is not permitted to be used
Woods frame method
What is darning
Irregular holes or jagged tears in fabric may be repaired by darning provided that the hole is no bigger than 50mm wide at any point
What is used for damage over 100mm wide
Square insertion repairs are normally used
What is a boot stitch
Used for repairs, requires a lock knot every 150mm (6 inches)
What are the 2 portable fabric testers
- Maule
- Seyboth
What is the maule tester
If the tester has penetrated the fabric then the fabric has failed the test
What is the seyboth tester
Always pierce the fabric
Colour scale
Make sure not on double width fabric
All holes must be doped closed
What man made fabrics replace natural fabrics used on aircraft
- Polyester fibre materials
- Glass fibre materials
What is done to polyester fibre materials to apply them to structures
They are toughened by heat. (Usually and iron at 120°c)
How is glass fibre applied to an aircraft
Can only be slightly toughened by dope so it must be a good initial fit
What are the functions of dope
- Toughening of natural fabrics
- Waterproofing
- Airproofing
- Light proofing
What are the 2 different types of dopes used
- Cellulose nitrate
- Cellulose acetate butyrate
Why is aluminium dope sometimes used
To protect the fabric from sunlight (UV)
What is Methylethyl-Ketone (MEK) used for
It is a relatively low cost solvent, similar to acetone. It is widely used for a cleaning agent and to remove dirt or wax prior to doping
What is normally added to the first layer of dope
A fungicide to prevent the growth of fungus
What are the main hazards of dopes
Very flammable
Low flash point
Accumulation of vapours can ignite easily
What is the most common cause of dope ignition
The discharge of static electricity
What must be done to prevent the build up of static discharge when doping an aircraft
The aircraft should be grounded
What is the bet way airflow is regulated when doping an aircraft
A fan should be installed at floor level and the fan should be explosion proof
For applying dopes what temperature range is prime and shouldn’t really be exceeded
Between 21°c and 26°c
What is the ideal humidity required when doping
Between 45-50% however anything from 20-70% is acceptable
What is the most common way of measuring humidity
Wet bulb dry bulb method
What are priming coats
The first coats applied to a fabric
