The applicability of FAR 121.377 is not eliminated by a person's performing a mix of work such as you describe. Such an interpretation would defeat the purpose of the regulation which is to insure that person's performing part 121 maintenance or preventive maintenance are provided relief from duty.
The cause of rheumatoid arthritis is unknown, although it appears to be an autoimmune disease. When the body's immune system does not operate as it should, white blood cells that normally attack bacteria or viruses attack healthy tissue instead â in this case, the synovium, or joint tissue.
The specific cause of rheumatoid arthritis has yet to be identified despite decades of medical research. While we donât know specifically what causes rheumatoid arthritis, we do know that it is the result of an autoimmune disorder. An autoimmune disorder occurs when immune cells begin to attack the body. In the case of rheumatoid arthritis, the body attacks its own healthy joint tissue called the synovium. The synovium is what produces a clear liquid substance known as synovial fluid. This fluid lubricates healthy joints and gives cartilage and bones the nourishment required to remain effective and mobile.