Fluid Lines & Fittings
How should a flexible hose be installed with respect to length, and why?
Answer
Provide about 5 to 8 percent slack because the hose changes length when pressurized
Flexible hose contracts in length (and expands in diameter) when pressurized, so roughly 5 to 8 percent slack is provided; an over-tight installation would place the hose under tension and could pull loose or fail. 25 percent is far more slack than needed, which invites chafing and snagging.
Source: FAA-H-8083-30B, Chapter 9, Fluid Lines and Fittings; AC 43.13-1B (flexible hose installation practices)
Not the answer
- Provide about 25 percent slack because the hose stretches greatly in length when it is under pressure
- Install the hose taut with no slack to minimize chafing
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