Iowa Public Television

Challenge Question Number 1 for Deputy Group Commander #1193

Clearly describe what you expect from the students:
You are the Navigation Officer on board a U.S. Coast Guard Cutter "Indefatigable." The cutter is ordered to intercept a sailboat which is on fire to rescue those onboard. Your heading is 010º true and your speed is 8 knots. You will have to change course 90º to the right to be traveling in the correct direction. The sail boat is 12 nautical miles away.(Hint: "True" north is the geographic North Pole whereas "Magnetic" north is the position where the charged pole is located. These poles are not located in the same position and Magnetic North periodically moves.)

a. What course "true" will you be heading to intercept the sail boat?

b. At your current speed, how long will it take you to reach the sail boat? (Hint: 1 knot = 1 nautical mile per hour. A nautical mile is 2000 yards.)

c. What speed would you have to increase to in order to reach the sail boat in 30 minutes?

d. If a Coast Guard helicopter were in the same location as the cutter but could travel at 200 knots, how long would it take to reach the burning sail boat?

What could the helicopter do that the cutter could not and vice versa?

e. What does "Indefatigable" mean?

3. Your gyro-compass which designates True north breaks and you must rely on your magnetic-compass which designated Magnetic north. Magnetic north is not geographically located where true north is located. Why? If your magnetic compass has a 9.5º error to the east, answer question 2.a. above.

In order to give the teacher some guidance in evaluating the student's project(s); list some tips that may help to assess the student's work:
Did the students recognize, or know, there are 360º in a circle?

The above problems do not account for wind or current and assume the sail boat is stationary. The instructor could include additional vectors to complicate the problems or for discussion. For example, a 5 knot wind out of the southeast may slow the cutter by 1 knot true speed, as opposed to the speed the engines are set to make, which would delay the cutters arrival. To compensate for the wind, the navigator should suggest the ship increase its speed by 1 knot.