14 CFR § 29.993

Each fuel line must be installed and supported to prevent excessive vibration and to withstand loads due to fuel pressure, valve actuation, and accelerated flight conditions.

Each fuel line connected to components of the rotorcraft between which relative motion could exist must have provisions for flexibility.

Each flexible connection in fuel lines that may be under pressure or subjected to axial loading must use flexible hose assemblies.

Flexible hose must be approved.

No flexible hose that might be adversely affected by high temperatures may be used where excessive temperatures will exist during operation or after engine shutdown.