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BOTTOM SKIN OF FUSELAGE
Figure 2: Diagram Fuselage Bottom Skin Restricted Area Diagram
DA20-C1 AMM
Standard Practices
And Structures
Doc # DA201-C1
Rev. 14 51-00-00 Page 5
30 Oct 2008
5. Repair Limitations
You cannot do in-service repairs on these components:
− The main spar and the spar bridge.
− Damage close to the main attachment fittings for the wing or horizontal stabilizer.
These are major repairs. You must ask the manufacturer for a repair scheme.
Figures 1 and 2 are the Restricted Area Diagrams. They show where you can do external skin
repairs.
6. Inspection Techniques
There are different methods of inspecting a damaged composite area. The following gives the
procedures for inspecting a damaged Fiber Reinforced Plastic (FRP) area.
A. Examine Visually
Look carefully at the outer surface of an area or component. If the paint has cracks or bubbles,
then the composite may be damaged. Surface damage, e.g. dents or scratches may be
detected by visual inspection. Look especially in the areas where stones can hit the airplane
below the fuselage and wings. By visual inspection, you can see where fiber breakage or matrix
cracking has happened. Damage to the core may also be visible.
A bright light can be used to visually examine the inside of a component. Glass Fiber
Reinforced Plastic (GFRP) must be green or brown. If the GFRP has white areas, then it may
be damaged. Look especially at areas where components bond to the GFRP.
Carbon Fiber Reinforced Plastic (CFRP) must be black or black/brown. If the CFRP has white
areas, then it may be damaged. Look especially at areas where components bond to the CFRP.
B. Light Test
A light test can be used to find delamination on components which do not have rigid foam inside.
CAUTION: DO NOT LET THE COMPOSITE GET HOT.
HEAT CAN CAUSE DAMAGE TO THE COMPOSITE.
Point a bright light at the surface of the composite and look at the other side of the surface.
Damage shows as a dark area. You can point the light from the inside or from the outside of a
component.
NOTE: You can use the light test on thick GFRP but it is difficult to use on CFRP.
Standard Practices
And Structures
DA20-C1 AMM
Page 6
30 Oct 2008 51-00-00 Doc # DA201-C1
Rev. 14
C. Coin Tap Test
Damage to the laminate can be detected by tapping a coin on the laminate. The sound of
tapping will change its frequency as you move over the damaged area in relation to the sound
of other areas of corresponding thickness. By performing a tap test, you can detect disbonds
(the separation of one component which is bonded to another component) and delaminations
(the separation of individual layers of the glass cloth).
Pay special attention to the area surrounding the damage, because there could be secondary
damage, which can remain undetected.
DA20-C1 AMM
Standard Practices
And Structures
Doc # DA201-C1
Rev. 14 51-00-00 Page 7
30 Oct 2008
100
40
100
100 100 400 400
500
600
500
200 200
200 200
300300
300 300
400 400
Mass Balance
Area on Aileron
150
250
LIMITED AREA 1
Repairs allowed on external
skin damage up to 250mm
(10 in) diameter
LIMITED AREA 2
Repairs allowed on external
skin damage up to 50mm
(2 in) diameter
PROHIBITED REPAIR AREA
Repairs to be carried out only by
the manufacturer or an approved
repair facility
NOTE: All dimensions are mm
NOTE: THE WING DATA IS VALID
FOR TOP AND BOTTOM SHELLS
Figure 3: Wing, Top Fuselage and Horizontal Stabilizer Restricted Area
Standard Practices
And Structures
DA20-C1 AMM
Page 8
30 Oct 2008 51-00-00 Doc # DA201-C1
Rev. 14
7. Approved Materials, Suppliers
A. Resin and Hardener
Supplier: Scheufler, D-70327 Stuttgart
Resin: L160 (100 parts by weight) Hardener: 163 (28 parts by weight)
NOTE: L285/286 resin shall be used for DA20-C1 S/N C0186 to S/N C0199.
L160/163 resin shall be used for DA20-C1 up to S/N C0185 and S/N C0200 and higher.
B. Glass Fiber Cloth
Supplier: Interglas Textil Gmbh
Interglas Technologies AG
BenzstraBe 14. D-89155 Erbach, Germany
Cloth Mass per Area
grams/m²
Interglas
No.
Double twill 2/2 161 92110
Double twill 2/2 276 92125
Double twill 2/2 390 92140
Warp reinforced 220 92145
Warp reinforced 433 92146
All cloth is made from alkali free E-glass with Volan-A-Finish or Finish I 550, and complies with LN
9169
C. Carbon Fiber Cloth
Supplier:
Cloth Mass per Area
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