Radar and ARPA operation
What is being checked
The inspector is checking whether both radar and ARPA units are tuned and used as independent collision-avoidance and position-monitoring aids, with officers able to configure, cross-check, test and respond to failure of the actual equipment fitted.
Ready onboard
0/6 completePractice questions
Answer aloud, then open the preparation point.
1What safety function does radar and arpa operation provide?
Both radar and arpa units are tuned and used as independent collision-avoidance and position-monitoring aids.
2How is the complete function tested?
Use the approved performance monitor and operational checks, compare both radars, verify heading and speed inputs and demonstrate acquisition, tracking and alarm functions.
3What is its principal limitation?
ARPA vectors depend on stable targets, correct inputs and adequate tracking time; small, weak, manoeuvring or rain-obscured targets can be lost or misrepresented.
4What is your response if it fails?
Use the second radar, visual bearings, manual plotting and safe speed, call the Master and repair or formally control the defect.
5Show the latest test and operational evidence.
Link the dated record to the actual unit, test method, result, defect response and restoration; a panel lamp test alone is not sufficient where the full signal path can be tested.
Where an observation may arise
The responsible officer cannot explain safe use, limitations or failure response.
Testing does not prove the required operational function or remote indication.
Automatic settings are accepted despite lost targets or excessive clutter.
Wrong speed or heading input corrupts vectors and closest-point calculations.
The second unit is not set up as an effective independent aid.
Past observations for practice
Operator's PMS stated magnetron to be changed at 7500 RH. Present RH on S band radar was noted as 10249.7 RH.
OP has completed the job in PMS without the job being done and without operator permission. Comment was included stating that the radar performance for not in order.
The OP was not aware of which Radar (X band or S band) was more efficient during the rains and during the bad weather.
Master's practical note
Compare one target on both radars and explain any vector difference. A clean presentation is not necessarily a correctly stabilised or well-tuned picture.
Equipment boundary and references
Equipment boundary: Radar and ARPA support but do not replace COLREG assessment by all available means. Trial manoeuvre is advisory and must not be treated as an automatic decision.
References
- OCIMF SIRE 2.0 Question Library Part 1, Version 1.0, Question 4.1.2
- SOLAS Chapter V regulation 19
- COLREG rules 5, 6, 7 and 8
- ICS Bridge Procedures Guide
- IMO radar performance standards
Last reviewed: 2026-09-11
