American Eurocopter’s blade shop in Grand Prairie, Texas, is a busy place. The 20 craftsmen repair and refurbish 1,000 helicopter main and tail rotor blades every year. That translates into 95 percent of all Eurocopter blade work in the U.S.
Much of the work is done by hand. “It is a slow process,” acknowledges shop manager Jim Tully. “It would be nice if we could find a way to go faster, but it has to be done the same way. With fiberglass, it wouldn’t take long to scrap out a blade completely” if a mistake were made.
Blades for the EC135 and EC145 have 11 layers of fiberglass, and stripping the blades requires careful wet sanding with progressively finer gradations of sand paper, from 80 to 300 grain, and then replacement of those layers one at a time in an equally painstaking process. The blades cost anywhere from $70,000 to $120,000 each and any error could prove costly.
The typical repair takes 10 to 20 days. The blades are uncrated and inspected. Then the customer receives a quote and work begins. All of the blade technicians are cross-trained to perform every job in the shop–this speeds workflow–and that training takes years, Tully said. “Somebody who comes in without any blade experience, it usually takes them three to four years to get all the way up to speed to be able to receive a blade, go through the inspection, do all the repairs and push a blade back out the door.”
The training is conducted by Eurocopter instructors who fly in from France and Germany, or by Grand Prairie shop leads who go to Europe for training and recurrent certification and then share the knowledge upon their return. Leads must be recertified every two years and the blade shop itself must be audited and recertified every two years by Eurocopter. Additionally, all technicians must have annual hearing and vision exams because most of the inspections are still done with eyes and ears. The auditory part of the inspection, tap testing, is complex, said Tully. “All of the blades have different zones and you will hear the difference in the tapping. They [the technicians] know what each zone is supposed to sound like and tap every inch on the way down [the blade].” On rare occasions, blades are sent back to France or Germany for ultrasonic inspection.
After inspection and sanding, the blades arrive in the climate-controlled bond room for skin and leading-edge repairs. From there they go to the balance room, where blades are put back to their nominal value for balance purposes and to determine how much paint can be applied. Then it’s off to the paint shop and then one more rebalancing. Careful balancing allows operators to have individual blades repaired, as opposed to entire sets, which is still the case on older Eurocopter models such as the BK117 and the Bo105.
Typically, blades need repairs after between 3,000 and 7,000 hours, Tully said, and most of that work involves sanding and refinishing. Most Eurocopter main rotor blades have a life limit of 20,000 hours. “Most customers never reach that point,” Tully said. Air-tour operators will get 12,000 to 17,000 hours on a set of blades. “At that point, the amount of money it takes to repair isn’t worth it. You are better off exchanging or just purchasing new blades.”
Blades that have been through the repair process are stenciled with the part number, serial number and center of gravity. Then a quality assurance inspector reviews the work before closing out the job and approving shipment back to the customer.