Excessive stress on fluid or pneumatic metal tubing due to temperature changes can best be avoided by?

• A. using short, straight sections of tubing between fixed part of the aircraft
• B. using tubing of the same material as the majority of the adjoining structure
• C. providing bends in the tubing
• D. using bends in the tubing

Answer: (C)

When metal tubing is heated or cooled, it expands or contracts. If the tubing is tightly fixed at both ends with little or no give, those temperature-induced length changes create axial stress in the line. Providing bends in the tubing introduces flexibility, letting the tube accommodate expansion and contraction without building up harmful stresses. The bends act as built-in slack or a small “accordion” effect so the system can adapt to temperature shifts.

So, the best way to avoid excessive stress from temperature changes is to include bends in the tubing, which allows the tubing to move with temperature changes rather than being rigidly restrained. Short straight sections between fixed points increase restraint and stress, and simply matching the material to the surrounding structure doesn’t inherently prevent the stress without allowing some movement.