Question 1

Your examiner asks: "What is the radar horizon, roughly how is it estimated, and why does it typically extend slightly further than the visual horizon?"

Accepted Answer

The radar horizon is the maximum theoretical range at which a radar beam can reach a target of a given height, limited by the curvature of the earth — beyond it, a target (regardless of size or radar reflectivity) simply cannot be illuminated by the beam because the earth's surface is in the way. It is commonly estimated using a formula of the form: distance to radar horizon (nautical miles) is proportional to the square root of the scanner height, combined with a similar allowance for target height — broadly comparable to the well-known visual/geographic horizon formula. The radar horizon is typically slightly GREATER than the optical/visual horizon (by very roughly 6%, depending on which reference formula and atmospheric assumption is used) because standard atmospheric refraction bends the radar beam slightly around the curvature of the earth, similarly to (though not identically with) the refraction that extends the visual horizon. The radar horizon concept explains why maximum detection range is not simply a function of transmitter power — a target beyond the radar horizon cannot be detected no matter how powerful the set, because the beam cannot physically reach it over the curve of the earth. The OOW should understand this as a practical planning tool: raising the scanner (or, for a small craft, a portable radar reflector) increases the radar horizon and therefore potential detection range, exactly as raising a lookout's eye height increases the visual horizon. The approximate 6% extension over the optical horizon comes from standard atmospheric refraction bending the radar beam very slightly downward around the earth's curvature — the same broad mechanism (to a different degree) that extends the visible horizon beyond the pure geometric horizon.

Question 2

You're asked to test a deck crane grab after electrical repairs nearby. As the grab is hoisted, what should have happened first?

Accepted Answer

The area within the grab's swing radius should be cleared of personnel before the lift On the bulk carrier Fairfield Eagle, a crew member working nearby was struck and fatally injured when a grab being test-lifted after repairs swung unexpectedly. The investigation found the area should have been cleared and barriered before the test lift began.

Question 3

A toolbox talk held before a lifting operation should explicitly cover which of the following?

Accepted Answer

Who must remain clear of the exclusion zone while the lift takes place A toolbox talk exists to make sure everyone present understands the danger zones, the abort signal, and — critically — who must not be in the area while the lift happens. The RMIMA investigation into the Fairfield Eagle fatality found the toolbox talk had not made this clear.