Eddy current testing is one of the Non Destructive Testing (NDT)

NDT is a science and technology which allows the examination ofcomponents without disturbing their condition.
Sati Reel, the Managing Director of Phoenix Aviation Limited,explained, "Aircraft parts are subjected to vibrations,structural stresses and temperature variations which can causedefects. Initially these are very small, but they continue to growin size."
"NDT techniques enable aircraft technicians to detect suchflaws in their early stages and carry out the repair, orreplacement of the weak component before there is a completestructural failure."
"Aircraft are required to be checked at set intervals based onaccumulated hours of operation and the passage of time. Initiallytechnicians carry out a visual inspection aided by a magnifyingglass, light source, or a borescope which is an instrument used toinspect the inside of an engine by inserting a probe which islinked to a monitor screen."
Floyd Laval, the head of the engine workshop at Phoenix Aviation,described the examination processes, "While most defects aredetected by visual inspection in aircraft maintenance, furtherassessments are carried out on key components and those which arelikely to develop faults.
"We use a Zetec eddy current tester to detect surface, or nearsurface defects."
"This machine can be used on aircraft parts or assemblieswhere the suspect area is accessible to contact by the eddy currentprobe.
"In other cases, components are removed from the aircraft andplaced on a work bench for the test."
"The inspection involves applying the probe to the surface andinducing eddy currents and observing the variations in the inducedfield on the screen of the tester.
"A trained operator notes the changes in the field andinterprets them to determine the condition of the components."
Talking about other methods, Floyd Laval said, "Liquidpenetrant testing is used to detect small cracks on the surfacewhich may not be evident by normal visual inspection.
"A liquid is applied which penetrates into the surfacedefects.
"After removing excessive liquid, developers are applied todraw the penetrant from the surface defects.
"Visual indications are obtained by the application of a"black light" which produces colour contrasts."
"Testing for surface, or near surface defects in parts thatcan be magnetized (ferro-magnetic) may be carried out by inducing amagnetic field in the part and applying a dry powder, or liquidsuspension of iron oxide particles.
"Any defects form magnetic poles which attract the oxideparticles and a "black light" is used to evaluate theproblem."
Sati Reel concluded, "NDT tests are being carried outregularly during each working day in our hangars and workshops.
In addition to looking after the Phoenix Aviation fleet ofBeechcraft King Air turbo prop aircraft and Cessna Citation Bravojets, our repair and maintenance facility provides services forother operators of light aircraft within the East African region.