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Heading Figure 16-17. Establishing a wind correction angle that counteracts wind drift and maintains the desired course. 16-11 dniW 075° Wind correction angle 090° Track Desired course Basic Calculations knots). Pilots, therefore, should learn to convert wind speeds that are reported in knots to mph. Before a cross-country flight, a pilot should make common calculations for time, speed, and distance, and the amount A knot is 1 nautical mile per hour (NMPH). Because there are of fuel required. 6,076.1 feet in 1 NM and 5,280 feet in 1 SM, the conversion factor is 1.15. To convert knots to mph, multiply speed in Converting Minutes to Equivalent Hours knots by 1.15. For example: a wind speed of 20 knots is Frequently, it is necessary to convert minutes into equivalent equivalent to 23 mph. hours when solving speed, time, and distance problems. To convert minutes to hours, divide by 60 (60 minutes = 1 hour). Most flight computers or electronic calculators have a Thus, 30 minutes is 30/60 = 0.5 hour. To convert hours to means of making this conversion. Another quick method of minutes, multiply by 60. Thus, 0.75 hour equals 0.75 × 60 conversion is to use the scales of NM and SM at the bottom = 45 minutes. of aeronautical charts. Time T = D/GS Fuel Consumption To find the time (T) in flight, divide the distance (D) by the To ensure that sufficient fuel is available for your intended GS. The time to fly 210 NM at a GS of 140 knots is 210 ÷ flight, you must be able to accurately compute aircraft fuel 140 or 1.5 hours. (The 0.5 hour multiplied by 60 minutes consumption during preflight planning. Typically, fuel equals 30 minutes.) Answer: 1:30. consumption in gasoline-fueled aircraft is measured in gallons per hour. Since turbine engines consume much more Distance D = GS X T fuel than reciprocating engines, turbine-powered aircraft require much more fuel, and thus much larger fuel tanks. To find the distance flown in a given time, multiply GS by When determining these large fuel quantities, using a volume time. The distance flown in 1 hour 45 minutes at a GS of 120 measurement such as gallons presents a problem because knots is 120 × 1.75 or 210 NM. the volume of fuel varies greatly in relation to temperature. In contrast, density (weight) is less affected by temperature GS GS = D/T and therefore, provides a more uniform and repeatable To find the GS, divide the distance flown by the time measurement. For this reason, jet fuel is generally quantified required. If an aircraft flies 270 NM in 3 hours, the GS is by its density and volume. 270 ÷ 3 = 90 knots. This standard industry convention yields a pounds-of-fuel- Converting Knots to Miles Per Hour per-hour value which, when divided into the nautical miles Another conversion is that of changing knots to miles per hour (NM) per hour of travel (TAS ± winds) value, results in a (mph). The aviation industry is using knots more frequently specific range value. The typical label for specific range is than mph, but is important to understand the conversion for NM per pound of fuel, or often NM per 1,000 pounds of fuel. those that use mph when working with speed problems. The Preflight planning should be supported by proper monitoring NWS reports both surface winds and winds aloft in knots. of past fuel consumption as well as use of specified fuel However, airspeed indicators in some aircraft are calibrated management and mixture adjustment procedures in flight. in mph (although many are now calibrated in both mph and