Critical parts and their operating conditions have been selected as have analysis tools, and modifications have been started.
A load spectra preprocessor has been developed and a material data bank established.
A Round Robin exercise has been performed to establish degree of confidence and reliability of each test laboratory involved and material tests and analytical verification has commenced.
Damage tolerance requirements for helicopters have to be treated separately from their fixed wing counterparts since life requirements and vibration/manoeuvre related load spectra are rather different. Up to now there are no guidelines available for a systematic approach to an improvement of helicopter component life assessment or improved safety level at less or equal maintenance costs, taking into account all aspects of a damage tolerant design philosophy;e.g. systematic approach for the calculation of crack growth by means of fracture mechanics, systematic design, systematic choice or improvement of materials, etc.
Therefore, the assessment of a 'Helicopter Damage Tolerant Design Guide' is essential. This Design Guide has to be planned as a compilation of all the knowledge needed to achieve a damage tolerant design of a modern civil helicopter. These efforts are also required in the light of the newly proposed FAR 29.571 which is calling for the approval of damage tolerance as a certification requirement.