PNAA aerospace manufacturing conference visitor's guide – Aerospace Manufacturing and Design (press release)

Figure 1: Rockwell Collins’ test system can pull or push multiple lavatory surfaces simultaneously.

The only chair on an airplane without a seatbelt, lavatory structures have stringent safety requirements. Keeping passengers safe in these tiny private rooms requires extensive testing, something that has traditionally been a manual process. The Interior Systems Business of Rockwell Collins in Everett, Washington, primarily produces lavatories for commercial aircraft. Before the lavatory units can be installed in aircraft, they must be structurally tested to standards specified by the Federal Aviation Administration (FAA) in conjunction with Rockwell Collins’ customer.

“The FAA mandates a number of load cases that you have to meet,” says Jeff Whitaker, Rockwell Collins test engineering supervisor.

To test the integrity of the structures, Rockwell Collins’ test group executes a protocol that will push or pull on one or more lavatory surfaces simultaneously (see Figure 1, above). The tests ramp the force up to more than 10,000 lb max. loads, applied in different configurations by a series of hydraulic or pneumatic cylinders acting on the lavatory surfaces through mechanisms called whiffletrees, which distribute force from a single cylinder evenly across a surface through bars, poles, and linkages.

The need for improved controls

Historically, running the tests at Rockwell Collins was a very manual process, relying on the skill of a human operator who had to operate multiple hydraulic or pneumatic cylinders simultaneously.

“It could take 20 minutes to run a test, with the results recorded on a PC via LabVIEW software,” Whitaker says.

Besides being time-consuming, the human element reduced precise repeatability from one test to the next. Figure 2a (page 65) shows the forces applied by four cylinders in a typical test when run manually. The solid lines show the desired increase in force through time, while the jagged lines show the

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