Topic 2.1 Extended H – Relative velocity – plotting courses FYI: A nautical mile is 6076 ft (compared to the commonly used statute mile of 5280 ft). Topic 2.1 Extended H – 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. © 2006 By Timothy K. Lund 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?
NORTH / SOUTH REFERENCE FYI: Pilots measure angles WRT NORTH. In other words, North is 0°. 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. vPA + vAG = vPG plane equation Distance is 32.5 nm. MERIDIAN OF LONGITUDE NORTH / SOUTH REFERENCE Time is 23 minutes. VPG VPA © 2006 By Timothy K. Lund E = 90° W = 270° PARALLEL OF LATITUDE EAST / WEST REFERENCE S = 180° The wind, and the destination's bearing. Step 1: Draw a line through ORIGIN and DESTINATION. Step 2: With your plotter, draw a scale WIND (VAG): Use any scale you like, but END it at DESTINATION. Line up plotter on course. STEP 5: Find BEARING of VPA: Step 3: With SAME scale, draw VPA: There are two directions we have no control over: STEP 4: Draw in VPG: It must END on the Tail if the WIND VECTOR. It must BEGIN on the ORIGINAL LINE (the red one). Find ACTUAL DISTANCE between ORIGIN and DESTINATION: Place bull's eye on a meridian. Bearing should be between 270° and 360°. Find the magnitude of VPG using SAME SCALE: Be sure to use CORRECT SCALE FOR MAP: Now we can calculate the travel time: t = d/VPG...