- Aircraft Engineering: NDT of Outer Starboard Main Plane
Aircraft Engineering: NDT of Outer Starboard Main Plane
The inspection process as specified by the United
States of Defence for testing of airplane components is
recommended. Initially a preliminary survey of the damage has to be
done and then the appropriate inspection process has to be followed
(USDF, 28 August 2001).
- Preliminary survey of the damage: The component is inspected
using techniques such as visual inspection; by touching and by
using mirrors, magnifying glasses, borescopes, optical micrometers,
camera, and depth gauges.
- Selection of Inspection Process. Several factors are considered
when choosing the suitable penetrant inspection process. These are
as follows: required sensitivity of test, surface condition of test
areas, part configuration, testing equipment whether part would be
damaged by the dye.
Remaining steps for the process are explained in
- Select the penetrant inspection process to be used.
- Select a part identical to the part to be placed under
- Perform penetrant inspection on the part selected in step 2 in
the same manner in which all parts will be inspected.
- After each inspection process procedure, check the part for
damage or adverse effects.
- If damage occurs, or adverse effects are noted, select an
inspection process which will eliminate the problem.
Precleaning. The material is
carefully cleaned first of water, carbon, engine varnish, dirt
paint, oxide, plating, oil or other contaminants, otherwise the
penetrant will not be able to get into the flaw and misleading
indications may result.
Drying. This process is used to assure the
evaporation of any water, solvents, or other cleaning solutions,
which might be loaded in a crack.
Penetrant Application. Penetrant is applied to
a part under test in a manner appropriate to the facilities
available. Sufficient dwell time should be allowed for optimum
penetration. The penetrant is allowed to remain on the surface for
a sufficient time to allow penetrant to seep through the defects by
Dwell (Draining). The part is set aside to
drain after the part has been coated with the penetrant. The
penetration (draining) time, in minutes, ranges from 5-240 minutes
depending on the material of the part and the characteristic of the
damage as well as the type of the penetrant (whether water-washable
or post-emulsified penetrant). For a post-emulsified penetrant
there is usually the additional step of applying the emulsifier
after penetration time has elapsed.
Emulsifier application, draining and dwelling.
This step is optional depending on the type of penetrant used.
Developer Application, Draining and Dwell
Time. Apply developer to the part. There are several
methods but spraying aqueous wet developer is preferred due to its
high sensitivity. Wet developers are allowed to drain prior to
drying. Developer is applied to the part under test as appropriate
to the process being used and the configuration of the part.
Developer dwell time will depend on the type of penetrant
developer. Sufficient time is allowed for an indication to form,
but the penetrant is not allowed to bleed into the developer in
such quantities to cause a loss of definition. The part is ready
for inspection under appropriate lighting to detect the presence,
location, and size of crack.
Inspection. The part should be inspected and
the crack interpreted. When the surface has been sufficiently
developed it will then be examined to see cracks formation.
Removal Methods. The developer is removed
after inspection by spraying with water or by washing.
Repair. The part should be repaired based on
the size, depth and nature of the crack. If necessary, repaint the
part before returning aircraft to service.
The paper has presented an overview of NDT and Dye
Penetrant Test. The same test has been used on the outer starboard
main plane section to detect a suspected crack. The structured
procedure specified for the inspection was presented and discussed
and the steps to be followed during the testing have been