Lightweight Aircraft Seating Takes off with Thermoplastic Alloy Sheet
SPOKANE, WA Aircraft seating is a challenge to design and manufacture. Seats must meet government and industry safety standards, be lightweight, and provide passengers with comfort, personal space and freedom of movement, as well as accommodate accessories such as tray tables, entertainment systems and controls. They are also expected to operate flawlessly and keep looking new despite constant impact from passengers, luggage and service carts, and repeated cleaning using harsh chemicals.
The 3050 FeatherWeight premium economy seat from TIMCO Aerosystems weighs as much as 25 percent less than similar seating. Shrouds, seat dividers, end caps, tray tables and other plastic components are formed by Multifab Inc. of Boltaron proprietary sheet for aircraft interior applications.
Center console shroud thermoformed of Boltaron 9815E sheet in .200 in. (5.08 mm) gauge shown on a 6-axis robotic CNC router.
Airlines periodically upgrade the seating of their fleets, and pay close attention to the evolving state-of-the-art in seat design, especially in terms of weight savings to reduce fuel consumption.
One newly introduced seat is as much as 25 percent lighter than other premium economy seats, according to its manufacturer, TIMCO Aerosystems, part of TIMCO Aviation Services of Greensboro, NC. The company's Model 3050 FeatherWeightTM seat is designed to maximize passenger comfort, provide a rocker-type recline mechanism that extends a foot and leg rest as the back reclines, and accommodate in-flight entertainment systems. Offered in 2- and 3-seat configurations, it potentially reduces overall weight of a 200 seat aircraft by more than 8000 lb (3629 kg).
Thermoplastic alloys cut weight, increase durability, improve aesthetics
"There are numerous part numbers for these seats," says Dean Cameron, sales manager of Multifab Inc., Spokane, WA, which thermoforms, pressure forms and vacuum forms armrest caps, end caps, tray tables, center dividers, electrical shrouds, life vest box assemblies and other parts of the seats.
Cameron says that Multifab specifies Boltaron sheet for all thermoplastic parts of the seats due to its processability and properties. "It is very friendly to thermoform," he says. "We form complex parts for this application to extremely tight tolerances. The grades of Boltaron sheet we use retain their cosmetic appearance during forming, and maintain a consistent wall thickness in deep recesses and on outside corners."
Multifab specifies two grades of Boltaron sheet: 4330 and 9815E. Both are proprietary thermoplastic alloys that carry an aircraft interior fire rating of FAR 25.853 A1, ii. Boltaron 9815E sheet is additionally rated to FAR 25.853 D as required for parts larger than 1 sq. ft. (305 sq. mm).
Because sheet products meeting the more stringent FAR 25.853 D standard typically exhibit lesser impact resistance, Multifab assessed that property across competitive sheet products. Although the Boltaron 9815E sheet is rated at 5.0 ft lbs/in (265 J/m) versus 3.0 ft lbs/in (159 J/m) for a competitive 65/65-compliant sheet, Boltaron's drop dart tests revealed that the competitive 60 mil sheet failed drop dart tests at 24 in. (61 cm), compared with 70 in. (178 cm) for 60 mil Boltaron 9815E sheet, a greater difference than published specifications indicate.
Forming diverse parts in a wide range of gauges and colors
Cameron says that the parts Multifab forms range in thickness from 0.080 to 0.200 in. (2.03 to 5.08 mm). Large parts, such as the shrouds between seats, average 2.5 ft (762 mm) in length, 18 to 20 in. (457 to 508 mm) in height, and can have 6 in. (152 mm) draw depths.
The parts may not look complicated when assembled in a seat, but Cameron says many require sophisticated tools to achieve the shape and functionality required for assembly. Some tools have slides to form undercuts in parts. The shrouds that separate seats, for example, are pressure formed in female tools. Each tool has a sidewall design feature that requires an undisclosed "process enhancement" to assure that the Boltaron sheet forms around the feature properly before vacuum is applied. Otherwise, Cameron says, the material would form a bridge between the feature and the sidewall.
Many of the tools are etched with an MT11020 chemical texture that is usually 0.0015 in. (0.040 mm) deep. The center divider seat shrouds and parts that interface in assembly are textured in the tools during forming. End bays and back shrouds are formed of textured sheet over male tooling.
Process considerations include whether the seating will be assembled in 2- or 3-seat sets, or installed in a left, right or center aisle. Some parts for left and right aisle seats differ slightly from each other, and so must be formed in different tools, explaining why there are a large number of part numbers.
Multifab orders the sheet in custom colors as specified by each airline. Cameron says the colors are generally special shades of gray, which Multifab and Boltaron develop according to specifications from TIMCO.
The company buys the Boltaron sheet in standard or custom sizes depending on part volume. Standard sizes are typically 4 by 8 ft (1,219 by 2,438 mm).
Multifab spent a year developing the program with TIMCO. By the end of 2012, Cameron expects that Multifab will deliver 30 shipsets of seating components. A shipset is the number of seats needed to equip one airliner for full operation.
Multifab has been providing thermoformed components to the aerospace industry since 1991. The company has a 180,000 sq ft (16,722 sq m) plant, and employs 160.
TIMCO Aerosystems is relatively new to the seating market. Parent company TIMCO Aviation has been involved in aircraft and engine maintenance, repair and overhaul for many years, and in 2002 acquired Brice Seating. TIMCO Aviation dropped the Brice name in April and made the business part of TIMCO Aerosystems. The 3050 FeatherWeight premium economy line is one of the first seating products marketed under the TIMCO Aerosystems brand.
"We are enthusiastic about this opportunity," Cameron says. "TIMCO Aerosystems' relationship with Multifab has been key to the development of this product line."