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A la HRB 1100 situados en l=36º10´N y L=006º10´W navegamos con un rumbo verdadero=152º y una velocidad de máquinas de 8 nudos. A la Hrb 1232 observamos el faro de Cabo Espartel con una demora verdadera de 127º y el faro de Punta Malabata a 19,4 millas. ¿Cuál es el rumbo e intensidad horaria de la corriente?At 1100 in 36º 10' N, 006º 10' W you steer true course 152º at 8 knots. At 1232 Cape Spartel bears 127º true and Punta Malabata is at 19.4 miles. What are the set and drift of the current?
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Correct answer: d) Rºc = 224º Ihc = 3.7'
Why it is correct
From 11:00 to 12:32 (1h 32m = 1.533 h) at 8 knots you run 12.3 miles along 152º to a DR position at 35º 59.1′ N, 006º 02.9′ W. Intersecting Dv(Spartel) = 127º with the 19.4′ arc from Malabata fixes the position at 35º 55.1′ N, 006º 07.8′ W. From DR to fix is 5.65 miles towards 224º ⇒ Ihc = 5.65 / 1.533 = 3.7 knots.
Why the others are not
- a) Does not divide the 5.65-mile drift by 1.533 hours or reverses the current direction.
- b) Does not divide the 5.65-mile drift by 1.533 hours or reverses the current direction.
- c) Does not divide the 5.65-mile drift by 1.533 hours or reverses the current direction.
How to work it out in the exam
- Find the 12:32 DR position (12.3′ on 152º) and observed fix (Dv Spartel = 127º, d Malabata = 19.4′).
- Join DR to fix: Rc = 224º and d = 5.65′ in 1.533 h ⇒ Ihc = 3.7 knots.
Where this question comes from
- Ministerio de Transportes (Madrid) · 2019 · Convocatoria de junio · PY Test 1 · question 34 Official paper · Official answer key
- Ministerio de Transportes (Madrid) · 2019 · Convocatoria de junio · PY Test 2 · question 36 Official paper · Official answer key
Try it: Navigation calculations
Pending instructor review. Machine translation, not reviewed.