scope:

Description of Driving Event:

On 5-2-85, a mishap occurred at the water tunnel at Building 1234. While the tunnel was filled with water for leak checks, the test section door detached from the test section, resulting in 3500 gallons of water escaping the tunnel and the building. Significant damage resulted to the test section door, model support mechanism, test section, flow channel, and the honeycomb flow straighteners.

The cause of the accident was the prying action between the door and the adjacent wall. This prying action, which was not considered in the design analysis, created stresses in the lucite door material beyond its flexural strength. There were other errors in the door design, to include: stresses were not combined (however, in the analysis performed - prying action not included - the material strength would have been sufficient for the loads considered). Acrylic materials should not be tapped and threaded (manufacturers recommend use of oversize bolt holes, grommets, and washers to minimize stress from through bolting) as was done with the test section door; and, framing, which could have provided for the load, was not used. The tunnel critical design review stipulated that, due to the effects of vibration, the water tunnel and the jet exit facility should not be run simultaneously. Effects of the jet exit facility vibrations on the water tunnel were not considered in the analysis.