For simple aircraft with reciprocating engines, the Aircraft  Flight Manual/Pilot’s Operating Handbook (AFM/POH)  supplied by the aircraft manufacturer provides gallons-per­ hour values to assist with preflight planning.  When planning a flight, you must determine how much  fuel is needed to reach your destination by calculating the  distance the aircraft can travel (with winds considered) at  a known rate of fuel consumption (gal/hr or lbs/hr) for the  expected groundspeed (GS) and ensure this amount, plus an  adequate reserve, is available on board. GS determines the  time the flight will take. The amount of fuel needed for a  given flight can be calculated by multiplying the estimated  flight time by the rate of consumption. For example, a flight  of 400 NM at 100 knots GS takes 4 hours to complete. If an  aircraft consumes 5 gallons of fuel per hour, the total fuel  consumption is 20 gallons (4 hours times 5 gallons). In this  example, there is no wind; therefore, true airspeed (TAS)  is also 100 knots, the same as GS. Since the rate of fuel  consumption remains relatively constant at a given TAS,  you must use GS to calculate fuel consumption when wind  is present. Specific range (NM/lb or NM/gal) is also useful  in calculating fuel consumption when wind is a factor.  You should always plan to be on the surface before any of  the following occur:  The rate of fuel consumption depends on many factors:  condition of the engine, propeller/rotor pitch, propeller/  rotor revolutions per minute (rpm), richness of the mixture,  and the percentage of horsepower used for flight at cruising  speed. The pilot should know the approximate consumption  rate from cruise performance charts or from experience.  In addition to the amount of fuel required for the flight,  there should be sufficient fuel for reserve. When estimating  consumption you must plan for cruise flight as well as startup  and taxi, and higher fuel burn during climb. Remember that  ground speed during climb is less than during cruise flight  at the same airspeed. Additional fuel for adequate reserve  should also be added as a safety measure.  Up to this point, only mathematical formulas have been used  to determine such items as time, distance, speed, and fuel  consumption. In reality, most pilots use a mechanical flight  computer called an E6B or electronic flight calculator. These  devices can compute numerous problems associated with  flight planning and navigation. The mechanical or electronic  Roads shown on the chart are primarily the well-traveled  roads or those most apparent when viewed from the air.  New roads and structures are constantly being built and  may not be shown on the chart until the next chart is issued.  Some structures, such as antennas, may be difficult to see.  Sometimes TV antennas are grouped together in an area near  a town. They are supported by almost invisible guy wires.  Never approach an area of antennas less than 500 feet above  the tallest one. Most of the taller structures are marked with  strobe lights to make them more visible to pilots. However,  some weather conditions or background lighting may make  them difficult to see. Aeronautical charts display the best  information available at the time of printing, but a pilot should  be cautious for new structures or changes that have occurred  since the chart was printed.  The checkpoints selected should be prominent features  common to the area of the flight. Choose checkpoints that can  be readily identified by other features, such as roads, rivers,  railroad tracks, lakes, and power lines. If possible, select  features that make useful boundaries or brackets on each  side of the course, such as highways, rivers, railroads, and  mountains. A pilot can keep from drifting too far off course  by referring to and not crossing the selected brackets. Never  place complete reliance on any single checkpoint. Choose  ample checkpoints. If one is missed, look for the next one while  maintaining the heading. When determining position from  checkpoints, remember that the scale of a sectional chart is 1  inch = 8 SM or 6.86 NM. For example, if a checkpoint selected  was approximately one-half inch from the course line on the  chart, it is 4 SM or 3.43 NM from the course on the ground.  In the more congested areas, some of the smaller features are  not included on the chart. If confused, hold the heading. If a  turn is made away from the heading, it is easy to become lost.  Pilotage is navigation by reference to landmarks or  checkpoints. It is a method of navigation that can be used  on any course that has adequate checkpoints, but it is more  commonly used in conjunction with dead reckoning and  VFR radio navigation.  Another aid in flight planning is a plotter, which is a protractor  and ruler. The pilot can use this when determining TC and  measuring distance. Most plotters have a ruler that measures  in both NM and SM and has a scale for a sectional chart on one  side and a world aeronautical chart on the other.  [Figure 16-18]  computer has an instruction book that probably includes  sample problems so the pilot can become familiar with its  functions and operation.  [Figure 16-18]  Plotter  Pilotage  Flight Computers  16-12  • Your flight time exceeds the amount of flight time  you calculated for the consumption of your preflight  fuel amount  • Your fuel gauge indicates low fuel level 