Stories

Eddy current technology enhances flight safety

The latest generation fighter, the F-35 Lightning II aircraft, maneuvers dynamically through the sky at speeds exceeding 1,000 mph. Demanding flight envelopes, such as this, create stresses on airframes and parts making even this advanced military aircraft susceptible to any defects invisible to the human eye.

KBRwyle's Eddy Current Inspection System (ECIS) finds unseen cracks, helping to prevent aircraft loss caused by ruptures initiated from fatigue cracks. It detects flaws in high-performance turbine engine parts and identifies small cracks that may go undetected by other methods. The ECIS also automates the decision to return parts to service or discard them. These capabilities enhance the safety of military pilots and ensure that aircraft are mission ready.

KBRwyle's Eddy Current Inspection System (pictured above) finds unseen cracks in aircraft engine components, helping to prevent engine failures while saving taxpayer dollars.

U.S. Air Force turns to KBRwyle for help

KBRwyle's ECIS has played an integral role in the safety of the U.S. military for over 25 years. Prior to the 1980s, the U.S. Air Force used a "safe-life" design strategy, which requires the preventive replacement of costly engine parts at a small fraction of their life expectancy to meet safety standards. This approach often leads to stress-limiting component designs that affect engine performance.

Eventually, the Air Force mandated the "damage tolerance" approach to address these issues. This   approach allows components to remain in service if inspections can demonstrate that cracks do not exceed a certain size limit. Components can also be safely returned to service if there are no cracks in critical regions that could grow and cause structural failure over the next two service intervals.

The Air Force launched the Retirement for Cause Program to implement this approach. It called for original equipment manufacturers (OEMs) to employ inspection requirements that ensured structural safety, durability, reduced life cycle costs, and increased service readiness. The program also required an OEM-independent inspection system that could reliably detect small cracks.

The Air Force turned to KBRwyle for help, and chose the ECIS to meet these requirements. Since then, the military has relied on the ECIS to conduct inspections on many high performance turbine engine platforms, including those on the F-14, F-15, F-16, F-22, F-35, B-1, B-2, KC-135, AH-64, and H-60.

The latest ECIS design meets the increased demand and specific requirements of the Pratt & Whitney F135 engine, which powers the F-35 Lightning II, the U.S. military's latest fifth-generation fighter.

How it Works

The ECIS is an automated, eight-axis system that performs detailed inspections of engine parts by using eddy current phenomonology. It then documents and stores searchable results. Eddy current inspections use an induction coil to generate electrical currents within conductors through a changing magnetic field. Changes in the flow path of these currents caused by discontinuities in the geometry or conductivity of the engine parts are detected by a receiving coil and identified as potential defects.

To use the ECIS, operators load a carousel with the required eddy current probes, enter information to identify the part, and start the inspection. From that point the ECIS aligns and dimensions the part.  Then, the ECIS picks up the pre-programmed probes, calibrates the probes, inspects the part, checks the calibration, and returns the probes. Indications of any defects are displayed on LED monitors and stored in a database. A permanent record of the raw inspection data is stored for later analysis. All of this is automated with minimal operator intervention and without the need for skilled human interpretation of the results.

KBRwyle's ECIS conducts inspections on many high performance turbine engine platforms, including the F135 engine on the F-35 Lightning II, the U.S. military's latest fifth-generation fighter.

Top Five ECIS Benefits

KBRwyle's ECIS has helped maintainers detect flaws and keep aircraft safe for several decades. The ECIS has five key benefits:

1. Detect hidden, and potentially, deadly defects as small as .005 inches. The system uses an alternating electric field to generate currents in a part under test through electromagnetic induction. Discontinuities, such as conductivity differences and small cracks, result in a disruption of the induced current field. The ECIS captures these distortions in the processed signals, which are reported as defects when they exceed pre-determined thresholds.
2. Eliminate inspection-integrity issues associated with human error. The system automatically inspects all parts consistently and reliably to the OEM-specified flaw size limits.  Automated part clamping, sensor selection and calibration, and sensitivity verification ensure repeatable results independent of the operator, sensor, or ECIS system used.
3. Find inspection data in an easy-to-use database.. Users can search for detailed inspection data, or metadata, of inspections. Additionally, engineers can carefully scrutinize all aspects of an inspection through the sophisticated ECIS analytics software. Engineers may even virtually re-inspect a component using modified inspection parameters.
4. Inspect complex engine parts. The ECIS utilizes high precision positioning accuracy, sophisticated motion control, and advanced signal processing capabilities to extract small flaw responses from large geometry responses. This allows the ECIS to successfully inspect a wide range of engines that impact numerous platforms, including next-generation fighter aircraft.
5. Get more accurate reads. The latest ECIS version contains a KBRwyle-designed digital instrumentation and signal path that digitizes the eddy current response closer to the sensor. This reduces signal noise and extends the operable frequency range of the inspection. It also provides the latest digital signal processing, array capabilities, and improved integration of eddy current sensors that increase throughput and reliability.

Safety Track Record

The U.S. Air Force has successfully employed the KBRwyle ECIS for over 25 years to keep aircraft and pilots safe while saving taxpayer dollars. Over the life of the system, the ECIS has saved an estimated $1 billion for just two of the ECIS supported jet engine lines through the safe return of parts into service. Due to its success and versatility, the U.S. military, international allies, and companies around the world have relied upon KBRwyle's ECIS system to find hidden cracks before takeoff to help ensure their engine platforms are safe for flight.