scope:

Description of Driving Event:

On October 29, 1985, a failure occurred in the 16' transonic tunnel during testing of a Lockheed designed powered turboprop model. The model failed while being tested at mach 0.8. The model propeller, spinner, balance, and air motor separated from the model nacelle and impacted the tunnel fan blades. The separated model components were irreparably damaged and all except one of the tunnel fan blades were damaged.

The investigating committee found the most probable cause of failure to be high dynamic loading due to loss of one or more prop blades. It was also found that:

• The model design approach attempted to eliminate blade loss as a credible failure mode.

• The consequence of blade failure was not considered by Langley, Lewis, or Lockheed.