Mohammad Riahi - Center for Advancement in Mechanical Testing & NDT
Mehdi Sharafy - School of Mechanical Engineering, Iran University of Science and Technology,Tehran, Iran ۱۶۵۵۷

Maintenance is an essential part of aviation industry activities. Amongst several common methods, preventive maintenance has been regarded as the most fundamental means of safe, reliable, operation of machinery and equipments by experts. Although predictive, proactive and computerized management are some other forms of effective maintenance of aviation machinery, however, preventive method is still regarded as the base for all other approaches. Mean Time Between Failures (MTBF) and Mean Time Between Repairs (MTBR) are used for the determination of proper replacement time of parts to avoid unexpected failures. Optimization of appropriate time to replace parts for the performing equipments is sought to reduce maintenance cost as well as to increase the reliability. Ambulance helicopters have dual characteristics in being utilized for transportation purposes. In addition to flying, which calls for a safe and sound operation, emergency nature of their work in many applications adds to the importance of their function. Tension-Torsion Strap is a part in helicopters in need of precise maintenance. In this study, determination of optimized replacement time for Tension-Torsion Strap of a helicopter with ambulatory operation has been carried out.

Preventive Maintenance (PM)- Increasing Reliability- Part Replacement Optimization-Mechanical Reliability