Julian Bray writes: You spend countless milions of aviation dollars developing bonded lightweight composites for your latest state of the art lightweight aircraft type but when something breaks off or gets damaged (as recently happened to two Ryanair aircraft constructed of bonded primary composites, when wingtips touched during a ground airport taxiway manoevre); you don't repair by bonding the primary composite material but send for a technician armed with a 20th Century metal patch and an olde fashioned bolt gun! Otherwise the repair won't be passed as safe by the regulators....madness! According to a recent presentation at the industry MRO Europe Convention, reported by Aviation Week: Bolt-on metal repairs made to aircraft originally constructed of bonded primary composites could soon become a thing of the past, as work to improve the acceptance and standardization of bonded repairs progresses, specialists (LHT) suggest. They were speaking at the recent MRO Europe conference.
Traditional bolted on repairs can be conter-productive or detrimental, cutting the composite structure’s residual strength by up to 50% and also adding extra weight. But amazingly regulators still do not accept bonding as an airworthy repair mothodology.
LHT is a member of the Composite Adaptable Inspection and Repair (CAIRE) project team, which includes and many other industry stakeholders. CAIRE seeks to automate and standardize bonded composite repairs thus gaining certification and quality assurance approval.
“The only repair that is certifiable at the moment is bolted, meaning that just like a standard metallic aircraft you put a bolted patch on it,” he explained. “The problem is bonding -- which we believe is the best way to repair composite aircraft -- isn't allowed by the regulators.”
Bonded repairs are largely done as required, manually, strength and durability are hard to verify without physically breaking the repair.
Using technologies from the CAIRE project, LHT and its partners claim to have developed an automated system for assessing, designing and repairing damage to composite structures. It optimizes the repair before scanning the surface for contaminants, grinding out the damaged material and creating the fix, which is applied manually.
JULIAN BRAY [ 01733 345581 ], Journalist, Broadcaster, Aviation Security &Operations, Travel / Cruise Industry Expert, Writer and Coach EQUITY, NUJ, Broadcast ISDN changed number 01733 345020) SKYPE: JULIAN.BRAY.UK e&oe A later updated version is always on the Website