Notar Helicopters Under NTSB Microscope

The NTSB has asked the FAA to require MD Helicopters to conduct tests to “enable the full analysis” of all critical loads for tension-torsion (T-T) straps installed in the notar anti-torque fan of MD 500N, 600N and 900 rotorcraft. The recommendations stem from the Safety Board’s ongoing investigations into two nonfatal accidents involving MD 900s in 2004. Based on existing data and additional data acquired under the recommendation, the NTSB wants rules issued to “require changes in the inspection and replacement of the T-T straps.” The Safety Board also wants the results of x-ray inspections to be examined for indications of both “progressive fiber fractures and for longitudinal cracks” and the removal of T-T straps in which damage of this kind is found.