This AIR is intended to describe and document a process presently in use for proof testing, which at the same time improves the fatigue life of 304 1.8 hard CRES and 3A1-2.5V CWSR titanium hydraulic tubing lines. Aerospace Information Report (AIR) 1419 "Inlet Total Pressure Distortion Considerations for Gas Turbine Engines" documents engineering information for use as reference material and for guidance. Inlet total-pressure distortion and other forms of flow distortion that can influence inlet/engine compatibility require examination to establish their effect on engine stability and performance. This report centers on inlet-generated total-pressure distortion measured at the Aerodynamic Interface Plane (AIP), not because this is necessarily the sole concern, but because it has been given sufficient attention in the aircraft and engine communities to produce generally accepted engineering practices for dealing with it. The report does not address procedures for dealing with performance destabilizing influences other than those due to total-pressure distortion, or with the effects of any distortion on aeroelastic stability.