We regularly hear the predictions of continual growth in the use of advanced composites in aircraft manufacturing. However, the use of bonding as a method of fastening is not new to aviation. Decades ago nonstructural components such as fairings, closure panels, and floor boards were fabricated using fiberglass materials, aluminum skins with balsa wood core, and in some cases flight controls on airliners were fabricated using aluminum skins with aluminum honeycomb core bonded together. Eventually bonding would include advanced composite materials such as carbon graphite, synthetic aramid fibers, and hybrid fabrics, becoming more the norm for flight controls, engine nacelle systems, primary structure, and recently complete fuselages being fabricated using carbon graphite material.
Repair and overhaul of aircraft components using metal bond, fiberglass, and advanced composite materials requires facilities with specialized equipment and a well-trained staff. Airline shops, maintenance repair and overhaul (MRO) organizations, and their associated maintenance technicians these days need to be equipped and trained to accomplish these sometimes complex repairs.
Modern maintenance shops specializing in bonded repairs require purpose-built facilities having dust collection equipment, environmentally controlled rooms for layup, temperature-controlled storage units for material and adhesive storage, safety features for the skilled people doing the work, and all the specialized tooling and equipment necessary when repairing bonded components. No longer does the far corner of the hangar or remote shop location suffice for this sometimes dust generating preparation and highly sensitive processes.
The new shop at LAX
I had the opportunity to visit the recently completed composite repair shop at FedEx Express Air Operation’s maintenance facility at Los Angeles International Airport (LAX). The LAX maintenance facility has hangar capacity for two heavy maintenance lines of MD-10 and MD-11 aircraft, along with a variety of support shops; sheetmetal, welding, numerous component repair areas, and the recently completed new composite repair area.
The new composite shop is nearly 9,000 square feet, operates on two shifts with a current staff of 27 aircraft maintenance technicians (AMTs), two leads, and a manager. Additional technical support comes from the maintenance base’s inspection and structural engineering groups. Like most composite shops, this one is no different and is responsible for a variety of work from paint touchup to advanced repairs using carbon graphite material.
Hector Chavez, manager of the LAX composite shop, says, “Currently we accomplish fiberglass and carbon graphite wet layup repairs, pre-impregnated (pre-preg) material hot-bond repairs, metal-bond repairs, and painting. We support the two heavy-check lines here at LAX for removed components and on-wing repair work, line maintenance support here at LAX, and we provide emergency support for the entire system when needed. We do it all from simple paint touchup, to on-wing repairs, to complex bonded repairs only capable in the shop.”
When developing the new composite shop Chavez says, “The footprint of this shop is very similar to the FedEx Express composite shops in Memphis (MEM) and Indianapolis (IND). We have an environmentally controlled area for sanding and grinding, and a separate environmentally controlled “clean-room” for layup and curing of repairs.”
The dedicated sanding room has downdraft airflow into the grated floor for collection of the dust and debris from sanding and grinding. But personnel safety begins well before you enter this area. Prior to entering the sanding room you first come through the Doff room which contains all of the personal protective equipment (PPE) necessary for working in this area. Once suited-up the technicians pass through the “air shower,” a self-contained chamber that as the name implies, showers you with air blowing contaminants off your clothing and into a filtration system. You must pass through the air chamber both entering and exiting the sanding room.