To a pilot, the airworthiness of the airplane is both a legal obligation and a direct responsibility. Careful personal attention to preflight procedures is the mark of a safe pilot and will be repaid not only in safety, but in lower airplane maintenance costs.    As the pilot approaches the airplane, the external visual inspection should be started by looking for hazardous obstructions in the parking area, and for dripping oil and fuel leaks under the airplane. Upon reaching the airplane all tiedowns, control locks, and chocks should be removed and the general appearance of the airplane checked for signs of damage such as dents, cracks, or scratches. Then, the preflight inspection should be performed in accordance with the printed checklist provided by the airplane manufacturer (Fig. 5-2).

   Water and dirt contamination in the airplane's fuel system is potentially dangerous; therefore, the pilot should take certain actions to prevent contamination or eliminate contamination that may have occurred. If the airplane's weight and balance will not be adversely affected for the next flight the fuel tanks should be completely filled after each flight, or at least after the last flight of the day. The reason is that when air in the fuel tanks cools, the moisture it contains condenses into water, and contaminates the fuel. The more fuel there is in the tanks, the less moist air the tanks will contain and the less condensation and contamination will occur.

   The pilot should always assume that the fuel in the airplane may be contaminated with water, and take the necessary steps to eliminate it during the preflight inspection. A substantial amount of fuel should be drained from the fuel strainer (gascolator) quick drain and, if possible, from each fuel tank sump into a transparent container to check for dirt and water. Water will be noticeable since it will sink to the bottom of the sample. Water (being heavier than gasoline), seeks the lowest levels in the fuel system - that is where the fuel drains are located. If water is found in the first sample, drain further samples until no trace appears.

   A second preventive measure is to avoid refueling from cans and drums, which may introduce fuel contamination by dirt or other impurities.

   Since each make and model of airplane has different features to inspect, it is impractical to provide an appropriate checklist here. Nonetheless, the following are some of the major items that should be given particular attention during a preflight inspection:

      1. Check landing gear control DOWN (if retractable gear).
      2. Turn master switch ON; check the fuel quantity gauges.
      3. Check master switch and ignition switch OFF.
      4. Visually check fuel supply in tanks; secure the tank caps.
      5. Drain fuel system sump (gascolator); check for contamination.
      7. Check that fuel system vents are open.
      8. Check oil level (ensure that dipstick is properly seated).
      9. Check for obvious fuel or oil leaks.
      10. Check cowling and inspection covers for security.
      11. Check propeller and spinner for defects or nicks.
      12. Check tires for cuts, wear, and proper inflation.
      13. Check nose gear and landing gear shock struts for proper inflation. Check wheel wells (if retractable gear).
      14. Check hydraulic lines and landing gear struts for leaks.
      15. Inspect tailwheel spring, steering arms, steering chains, and tire inflation (if tailwheel type).
      16. Remove pitot tube cover, if installed, and inspect pitot tube for clear opening.
      17. Inspect static air source for clean opening.
      18. Ensure that wings and control surfaces are free of mud, snow, ice, or frost.
      19. Remove control surface lock, if installed.
      20. Check for damage and operational interference of control surfaces or hinges.
      21. Check landing flaps for signs of operational interference.
      22. Check windshield and cabin windows for cleanliness.
      23. Check carburetor air intake for obstructions.
      24. Check baggage for proper storage and security.
      25. Close and secure the baggage compartment door.

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