Topic 2.1 Extended H – Relative velocity – plotting courses

1. FYI: A nautical mile is 6076 ft (compared to the commonly used statute mile of 5280 ft). Topic 2.1 ExtendedH – Relative velocity – plotting courses Wisconsin Aeronautical Charts (WACs) are used by pilots to navigate from one airport in Wisconsin to another. Among the many things shown on the WACs are Maximum Elevation Figures (MEFs), obstructions, beacons, radio call signs, etc. Suppose we want to fly from Milwaukee Mitchell, to Hartford Airport. Suppose that the wind is blowing at 22 knots (22 nautical miles per hour) out of the west. Suppose further that your Cessna is capable of an airspeed of 100 knots. In what direction should you head your Cessna, and how long will it take to reach Hartford Airport?

2. FYI: Pilots measure angles WRT NORTH. In other words, North is 0°. vPA + vAG = vPG plane equation FYI: Always measure angles WRT PARALLELS or MERIDIANS. ORIGIN: Milwaukee Mitchell DESTINATION: Hartford Airport WIND: 22 kn from west AIRSPEED: 100 kn N = 0° VAG Bearing is 308°. Groundspeed is 83 knots. Distance is 32.5 nm. NORTH / SOUTH REFERENCE MERIDIAN OF LONGITUDE Time is 23 minutes. VPG VPA E = 90° W = 270° PARALLEL OF LATITUDE EAST / WEST REFERENCE S = 180° Find the magnitude of VPG using SAME SCALE: Line up plotter on course. Step 2: With your plotter, draw a scale WIND (VAG): It must BEGIN on the ORIGINAL LINE (the red one). Use any scale you like, but END it at DESTINATION. Place bull's eye on a meridian. STEP 5: Find BEARING of VPA: STEP 4: Draw in VPG: Step 3: With SAME scale, draw VPA: Be sure to use CORRECT SCALE FOR MAP: Step 1: Draw a line through ORIGIN and DESTINATION. The wind, and the destination's bearing. There are two directions we have no control over: Find ACTUAL DISTANCE between ORIGIN and DESTINATION: Bearing should be between 270° and 360°. Now we can calculate the travel time: t = d/VPG... It must END on the Tail if the WIND VECTOR.