I was not aware of the radar rule as well. I am grateful it was brought up.
Reading the rule, the statement "appropriate to the prevailing circumstances and conditions" appears to indicate the requirement is condition dependent.
From Navrules FAQ:
11. Am I required to have Radar? Radar is not required on vessels under 1600 GT (
33 CFR 164.35), however,
Rule 7 states that
proper use shall be made of radar equipment if fitted and operational. In other words, whoever has one must use it. The Navigation Rules are not meant to discourage the use of any device, rather they expect prudent mariners to avail themselves of
all available means appropriate...as to make full appraisal of the situation (
Rule 5), e.g. the use of radar. At issue is whether the use of radar is appropriate in the prevailing circumstances and that is a determination made by the Master; and, ultimately decided by a trier of fact.
Should you be in a collision how would a judge/jury rule on your contention that the use of radar was impracticable (due to electrical drain, crew shortages, etc.)? Also, if a collision does occur, then there was obviously a
risk of collision beforehand. Could the determination of that risk have been made sooner with the use of radar? It is difficult to answer such questions because the circumstances of each case are different.
More importantly, remember that
Rule 7 specifies that assumptions shall not be made on the basis of scanty information, especially scanty radar information.
§ 83.07 (a) Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist. (b) Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observation of detected objects. (c) Assumptions shall not be made on the basis of scanty information, especially scanty radar information. (d) In determining if risk of collision exists the following considerations shall be among those taken into account: (i) Such risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change. (ii) Such risk may sometimes exist even when an appreciable bearing change is evident, particularly when approaching a very large vessel or a tow or when approaching a vessel at close range.