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A HRB=11:06 del 16 de octubre del 2010, navegando al rumbo de aguja= 010º, nos encontramos en situación verdadera l=35º 59´N, L= 005º 14´W. Se pide calcular la situación de estima a HRB= 12:12 sabiendo que la velocidad de máquinas es 12 nudos y el desvío de aguja es 3,5ºNE. Elija la respuesta que más se aproxima.On 16 October 2010 at 11:06 on Ra = 010º at true position 35º 59' N, 005º 14' W, calculate your DR position at 12:12 at 12 knots with compass deviation 3.5º NE:
Show the answer
Correct answer: a) l = 36º 12' N; L = 005º 10.8' W
Why it is correct
In 2010 charted variation (2º 50′ W 2005, 7′ E) is dm = 2º 15′ W = −2.25º; with deviation +3.5º, Ct = +1.25º and Rv = 011.25º. In 1h 06m (1.1 h) at 12 knots you run 13.2 miles from 35º 59′ N, 005º 14′ W to l = 36º 12′ N, L = 005º 10.8′ W.
Why the others are not
- b) Does not match the position after running 13.2 miles on Rv = 011.25º.
- c) Does not match the position after running 13.2 miles on Rv = 011.25º.
- d) Does not match the position after running 13.2 miles on Rv = 011.25º.
How to work it out in the exam
- Update variation to 2010 (−2.25º), add deviation +3.5º (Ct = +1.25º) and find Rv = 011.25º.
- Plot 13.2 miles (66 min at 12 knots) from 35º 59′ N, 005º 14′ W: 36º 12′ N, 005º 10.8′ W.
Where this question comes from
- Ministerio de Transportes (Madrid) · 2021 · Convocatoria de octubre · PER Test 2 · question 43 Official paper · Official answer key
- Ministerio de Transportes (Madrid) · 2021 · Convocatoria de octubre · PER Test 4 · question 44 Official paper · Official answer key
Try it: Navigation calculations
Pending instructor review. Machine translation, not reviewed.