BOEING HOPES TO cover one of its two Joint Strike Fighter (JSF) concept-demonstrators with plastic film, rather than paint, following successful flight-testing under the Joint Paintless Aircraft Programme (JPAP).
Boeing and 3M were awarded a contract in 1996 to demonstrate the feasibility of replacing paint with appliques - thin polymer films backed by pressure-sensitive adhesive. Flight testing of a McDonnell Douglas F-18B almost totally covered in appliques began in October 1996 and has included several hours of supersonic flight.
Appliques are being considered for the JSF as a way of reducing the environmental hazards and costs of painting, stripping and repainting aircraft. Weight reduction and corrosion prevention are other likely benefits, says JPAP programme manager Smoky Burgess.
Coating weight tends to grow with repeated repainting, and paint weights on F-18s have exceeded 365kg, compared with under 73kg when new. Applique weights are lower - film covering the flight-test F-18 weighs 55kg - and remain constant throughout the aircraft's life, Burgess says.
The film can be peeled off using hot, high-pressure water and disposed of as non-hazardous waste. New film is applied by hand, "like wallpaper", he says. More than 400 individual pieces were required to cover the F-18. These were shaped using "gore cuts" to follow the aircraft's curved surfaces. Butt and lap joints were used and edge sealer applied to prevent peeling.
Burgess suggests that applique shapes could be stored on computer and cut from flat film "on demand", using a plotter/cutter, when recoating an aircraft. The material can be applied during maintenance, while other work continues on the aircraft, he says.
As JSFs will be deployed on carriers, and appliques produced by 3M for use on Boeing commercial aircraft absorb water, a non-hydroscopic film was developed for the JPAP. Salt-fog and sulphur-dioxide testing has demonstrated that the resulting material "-is almost self-sealing-[and] close to a vapour barrier," Burgess says.
The applique-covered F-18 is used as a chase aircraft for the F-18E/F programme at the USNavy's Patuxent River, Maryland, flight-test centre. Routine corrosion inspections have resulted in 50% less work on areas covered by appliques, compared with painted aircraft, he says.
The year-long test programme is likely to be extended to two years, Burgess says.
Source: Flight International
