Citing the dangers of poor composite repair, Michael J. Hoke, owner of Abaris Training Resources Inc., focused his half-hour talk on Tuesday, Dec. 12, at the CAMX Presentation Theater on the solution: establish industry-wide standards for aircraft repair and reintroduce more hands-on training for repair technicians.
Hoke says that universal standards are key to reducing confusion. “One of the things you hear about the composites industry is that we have a lack of standards,” he explained. “That’s really not true. We have hundreds of standards [for aircraft repair].” The problem, Hoke added, is that OEMs have developed their own standards. For example, Boeing’s repairs are done in a certain way, while Airbus or Embraer may repair virtually identical structures in a different way. “So, you really confuse the poor aircraft mechanic who is working on a Boeing airplane one day and an Airbus airplane the next day,” said Hoke.
The Commercial Aircraft Composite Repair Committee (CACRC), a technical committee of SAE International of which Hoke is a member, has been working to establish standards since 1990, but progress has been slow, he said. While some standards have been developed by the committee and published by SAE – and they are beginning to make their way into airline structural repair manuals – much remains to be done to standardize repair techniques, materials, tools, inspection and training.
Training is also crucial to help prevent repair errors like one that caused a rotor blade failure in a Black Hawk helicopter. In that instance, Hoke said, the technician conducted the tape repair correctly, but then overheated the repair because he didn’t understand cure cycles. This, in turn, overheated the resin, causing it to burn in spots along the blade. That later caused the rotor blade to come apart in flight. (Fortunately, the helicopter landed in a muddy field, and the crew all survived.)
“There is no consistency mandated,” said Hoke. “You would think that the FAA, for example, would set standards for aircraft repair training – and they do — but not for composite repair training. There are no standards for aircraft composite training. Zero! They don’t exist.”
Instead, Hoke said, the FAA is currently using advisory standards that are not regulations, but suggestions. Hoke and other members of the CACRC committee are working with the FCC to develop regulatory training standards, but the process is moving slowly.
Hands-on training is invaluable, according to Hoke. It allows technicians to get a feel for working with the materials, seeing the result and experiencing some failures. That provides “the most valuable lessons they can learn,” said Hoke. Technicians particularly need hands-on training in tasks that appear simple, but aren’t. These include ply orientation, pleating, cleaning a vacuum bag around a complex shape and scarf sanding.