Game Composites GB1 GameBird, Maintenance Manual

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Maintenance Manual GB1 GameBird
Page date: April 24, 2020
51-2
Inspection for Delamination (Tap Test)
Warning: Any visual evidence of damage must be investigated by the tap test method described
here. The backside of the area should be inspected wherever possible.
If an impact is known to have happened, it is recommended to tap test the area even if
there is no visible evidence of damage, as well as the surrounding bond lines / load paths
to adjacent parts.
Tap Test
To check the airframe composite structure for delamination a tapping inspection should be performed by an
experienced person.
The following advice is adapted from FAA AC 41.13 issue 1B which is freely available on the FAA web site.
Tap testing is in section 8 paragraph 5-105 of the AC.
Tap testing is widely used for a quick evaluation of any accessible aircraft surface to detect the presence of
crushing, delamination or de-bonding.
a. The tap testing procedure consists of lightly tapping the surface of the part using either a coin, a special
lightweight hammer (less than 2 ounces / 57 grams, see figure 5-22 in the AC) or some other suitable
object. The acoustic response is compared with that of a known good area.
b. A “flat” or “dead” response is considered unacceptable. The acoustic response of a good part can vary
dramatically with changes in geometry so the entire area of interest must be tapped to establish its
responses. The surface should be dry and free of oil, grease, and dirt. Tap testing is limited to finding
relatively shallow defects in skins with a thickness less than .080 inch (2 mm). In a honeycomb
structure, for example, the far side bond-line cannot be evaluated, requiring two-side access for a
complete inspection. This method is portable, but no records are produced. The accuracy of this test
depends on the inspector’s subjective interpretation of the test response; therefore, only qualified
personnel should perform this test.
Experience shows that damage can be as small as 15 mm
(7/8”) across, so the tapping should not be widely
spaced.
General
These sections give information on the investigation, classification and repair of structural damage.
Before starting any repair, a decision must be taken whether the component, part, assembly etc. is to be
repaired or to be replaced.
Warning: Repairs must be conducted using materials and methods specified, defined and approved for the
task either in this manual or in applicable approved repair schemes or approved service bulletins.
All damage beyond cosmetic wear must be inspected by qualified and authorized personnel
before any flying or any repair action.