Case Studies: High-Speed Damage Detection
Because damage inflicted on aircraft can affect structural integrity and radar signature, specific aircraft types are inspected to triage damage and define repair actions. To improve current manual damage identification practices, metrology specialists from Survice Engineering Co. (Belcamp, MD) are integrating Metris iGPS from Brighton, MI-based Metris as the core of a turnkey aircraft damage inspection solution.
Metris iGPS, a noncontact, large-scale metrology solution, quickly and accurately acquires locations and characteristics of aircraft damage, both indoors and outdoors. The spatial coordinates of visual damage are instantly tracked by Metris iGPS and marked on a digital 3-D aircraft model, simultaneously stepping up process accuracy and efficiency.
Consistent Damage InterpretationAircraft incur structural and other damage from a variety of sources. Currently, aircraft damage is detected through visual inspection or through the aid of handheld, nondestructive inspection devices. Regardless of the inspection method, capturing exact damage location and spatial orientation is critical for determining effects on aircraft capability and accurately cataloguing damage for future reference.
Typically, hand measurements are taken relative to structural features, such as fasteners, doors and panels, and then manually noted and archived on paper.
To improve the speed and quality of aircraft damage inspection procedures, the company’s metrology group, Survice Metrology, researched potential solutions, identifying Metris iGPS as the appropriate solution for its needs.
“The principal asset of Metris iGPS is the capability to create a local, GPS-enabled environment using two or more iGPS transmitters,” says Mark Butkiewicz, manager of Survice Metrology. “In this large-scale environment, iGPS technology allows the location of aircraft damage to be determined instantly. By pinpointing a particular damage location with the tip of a measurement probe that incorporates iGPS receivers, the 3-D coordinates of the damage location are acquired on the spot.”
Large-Scale MeasurementAircraft inspection personnel need a robust solution that is easy to operate, practical to carry and based on a large inspection volume. Successfully proof tested in a major aircraft program, the technical capability of commercial, off-the-shelf Metris iGPS hardware coupled with software developed by Survice confirms valid measurement and provides a controlled digital data flow, regardless of indoor or outdoor use.
Through the use of custom software, data is immediately translated, overlaid onto the aircraft computer-aided (CAD) model and made available to various analysis tools for real-time processing. “The ability to use the Metris software development kit to dynamically interface with the iGPS hardware and develop custom solutions for our clients is one of the key elements that has led to the success of this program,” says Butkiewicz.
To begin the process of locating damage, the operator sets up the iGPS system near the aircraft. After calibrating the system by using fixed reference points on the aircraft, the software loads the geometric aircraft model and orients it into the iGPS field coordinate system. Based on triangulation of transmitter signals, the iGPS system determines the location of the probe tip positioned by the operator. Any location the operator measures on the aircraft is automatically superimposed to the same location on the geometric model.
Automatic mapping establishes accurate damage cataloguing and helps determine threat trajectory and radar cross-section changes. In this way, details of external damage and the direction of the threat provide useful information regarding potential internal damage.
Practical Solution Exceeds Accuracy“The system is truly portable and entirely battery operated,” says Butkiewicz. The system includes two environmentally sealed Metris iGPS transmitters mounted on tripods. The operator positions the touch-probe unit and wears a belt equipped with iGPS peripherals to wirelessly stream geometric data to a laptop computer.
Measurements are taken with a click of the probe button; 3-D coordinates are acquired and the location is visualized on the digital aircraft model. The system functions inside aircraft hangars as well as on flight lines, carrier hangar decks and forward deployed areas.
More transmitters can be added to increase the size and accessibility of the GPS-enabled area, and multiple operators can run probe measurements simultaneously to compress inspection time. Using a set of extensions, the probe can be lengthened up to approximately 1.8 meters.
Because the sensors are in the rear of the probe bar, the tip can be placed deep inside the aircraft structure without compromising the signal. As long as the probe sensors are within visual range of at least two transmitters, Metris iGPS is able to perform a valid measurement. In a two-transmitter setup, 1-millimeter precision is guaranteed at 50 meters. In a configuration with more transmitters, accuracy increases to 0.4 millimeter.