Your CD4 count. These cells are a type of white blood cell that is destroyed by HIV. A healthy person's count varies from 500 - over 1,000. If you have fewer than 200 CD4 cells, then your HIV has progressed to AIDS.
Aircraft fluid lines are usually made of metal tubing. or flexible hose. Metal tubing (also called rigid fluid. lines) is used in stationary applications and where long, relatively straight runs are possible. They are widely. used in aircraft for fuel, oil, coolant, oxygen, instru-. ment, and hydraulic lines. Flexible hose is generally. used with moving parts or where the hose is subject. to considerable vibration. Occasionally, it may be necessary to repair or replace. damaged aircraft fluid lines.
During NOE flight, geographical features are used as cover, exploiting valleys and folds in the terrain by flying in, rather than over, them. This keeps below enemy radar coverage, avoiding skylining. Other terms are also used, including ground-hugging,  terrain masking , or flying under the radar . The older term, commonly used for fixed-wing aircraft practicing this flight tactic in the World War II era, was hedgehopping.