Exploring Different Types of Nondestructive Testing for Commercial Aircraft

Time is among the biggest agitators with any aircraft testing scenario. When concerned with time, the two most important methods for aircraft nondestructive testing include eddy current testing (ECT) and ultrasonic testing (UT).

Compared to other NDT methods, ECT and UT can detect more flaws in less time and without the hassle of extensive setup times. With ECT, NDT analysts can cover surface defects and near-surface defects with greater efficiency and speed. UT also probes the same anomalies on a volumetric level and with the same expediency.

With that, it is important to equip analysts with prime tools and equipment that enhance ECT and UT functionality—instrumentation with specialized capabilities that foster flexible scans and additional customization schemes. In particular, analysts should have access to instruments capable of phased array ultrasonic testing (PAUT) and eddy current array (ECA), the most effective NDT methods of all the currently available options for commercial aircraft inspections.

Advantages of PAUT

Conventional ultrasound is a step above most NDT techniques, but phased array ultrasound takes it to the next level. Traditional UT has inflexible scanning positions and limited customization options, preventing analysts from finding flaws in awkward angles. With PAUT, however, inspectors will benefit from the following features:

• Customizing the beam shapes
• Adjusting the focus depths
• Achieving several angles

PAUT addresses the inconsistent thickness patterns of aircraft components. It’s also malleable enough to conform to the shape and texture of any component being tested. For reading compositions such as fiberglass, aluminum, and carbon laminate in particular, PAUT is the best method. The added features allow inspectors to probe more problems that would have gone unnoticed, especially minute defects.

Additionally, PAUT allows for angular scanning, otherwise called sectorial scanning, which allows the user to steer the beam in multiple directions to obtain a complete profile of the design form.  

Example: A level 3 analyst must search for stress points on an airplane wing. Using a portable instrument with a corresponding probe, the analyst uses the wedge to adjust the angle beam. The beam pinpoints a few dents instantly, and the beam reads several aberrations that could compromise structural integrity. The combined power of the full matrix capture (FMC) and the total focusing method (TFM) technologies can read the stress points with impeccable resolution.

That same instrument can also support an NDT paintbrush scanner that finds abrasions, erosions, and pittings. Using a paintbrush-like scanner, the analyst moves around the brush through various parts of the tested item as the encoded wheels track the scanner positioning in real-time. The real-time tracking helps the analyst pinpoint areas that the scanner failed to read, ensuring thorough radius coverage.

Regardless of the UT probing method, choose an instrument with high-quality software that streamlines data and yields a detailed composition of the flaws. The primary goal of any NDT inspector is to investigate the depth of the damage; in this regard, PAUT retains a competitive advantage over other NDT options.

Advantages of ECA

Eddy current array enhances conventional eddy current testing through the multi-coil features in a single probe. The additional coils allow NDT inspectors to scan a wider radius while detecting more defects in less time. ECA also offers some of the best signal-to-noise rate (SNR) in the industry, boosting the probability of detection (POD).

ECA probes can also spot hard-to-find anomalies in the form of:

• Pitting
• Surface cracks
• Corrosion

An advanced instrument can capture additional data with a single scan and surpass other nondestructive testing methods that require longer time commitments.

Example: NDT analysts must decide between using magnetic particle testing (MPT) or ECA for a surface inspection application. With MPT, they would need to apply chemicals that pose a hazard to humans in confined spaces. MPT devices also require an electrical source at all times, and are not always capable of yielding a strong enough signal to provide reliable indicators. The inspector chooses an ECA instrument with a surface array probe. The portable ECA instrument requires no electric sources or chemicals. Rather, ECA probing delivers unrivaled data instantly, with a full-scale image of the cracks and defects mapped on a high-resolution screen.

Liquid penetrant testing (LPT) is another technique that requires dangerous chemical use and lengthy testing intervals. LPT and MPT require considerable setup and post cleanup times, which are vital minutes that get lost with each testing phase.

With surface array technology, no surface preparation is needed whatsoever. Overall, surface array probes reduce inspection times by up to 95 percent when compared to pencil probes.

NDT analysts can also choose a handheld device that offers the same surface array technology withfaster inspection times. Handheld instruments are also adept at reaching inaccessible areas, providing the same level of precise analysis. Moreover, an ergonomically designed ECA handheld device can increase inspection efficiencies as inspectors can comfortably hold the instrument far longer than other form factors.

More importantly, ECA yields data that can be more accurate and comprehensive than MPT or LPT. ECA also allows you to choose different probes and accessories, such as surface array encoders that yield a wider context of the structural positioning of the faults in question.

Ideal Methods for Commercial Aircraft Nondestructive Testing

Eddy current array and phased array ultrasound offer quality data and malleable inspection scenarios that shorten inspection times and hasten the overall testing process. They also offer the necessary portability that lowers operational costs and equipment investments. PAUT provides more beam customization plans and scanning options than most nondestructive testing strategies. ECA provides powerful signal quality that reads flaws with greater depth at the surface and near-surface levels.

When it comes to aircraft nondestructive testing, PAUT and ECA are the superior NDT methods on the market. The key to getting the most out of PAUT and ECA inspections is to choose high-quality instrumentation equipped with state-of-the-art software that makes the equipment easy to use for trainees and veterans alike.

Zetec provides highly-regarded PAUT and ECA products that read cracks, stress points, and breaches in all forms. For more information on our eddy current and ultrasonic testing solutions, contact Zetec today.