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NI DPO Cheat Sheet

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DP Fundamentals + Control

  • Not published of exam
  • DP Control Loop Sensors + Inputs Controller vs Operator Seven DP Components

Reference Systems

  • Not published of exam
  • Position References PRS Failure Clues Reference Selector Absolute vs Relative

Power + Thrusters

  • Not published of exam
  • Power + Distribution Thrusters + Allocation Open vs Closed Bus Command vs Feedback

Redundancy + Assurance

  • Not published of exam
  • Classes + Redundancy FMEA + Assurance FMEA vs Trials Capability vs Footprint

Operations + Watchkeeping

  • Not published of exam
  • ASOG + Operating Modes Planning + Watchkeeping Document Picker CAM vs TAM

Failures + Response

  • Not published of exam
  • Alarms + Monitoring Failure Vocabulary Incident Priorities Failure Response Picker

Quick Facts

  • Credential NI DPO Certificate
  • Issuer The Nautical Institute
  • Scope New Offshore Scheme
  • Product Multi-phase certification route
  • Assessments Online + simulator practical
  • Experience Verified DP sea time
  • Final sign-off Statement of Suitability
  • Single blueprint Not published
  • Domain weights Not published
  • Training NI-accredited centres
  • STCW basis Part B guidance
  • Nigeria context NIMASA oversees STCW/MTIs
  • Operating rule Vessel procedures govern

Seven DP Components CO

  • Power, thrust, environment, position, control, interface, operator
  • Power: generation Thrust: force Sensors: environment + position Control: computer + HMI Operator: safety

Controller vs Operator CO

Controller

  • Runs control loop
  • Allocates thrust

Operator

  • Manages safety
  • Intervenes on failure
  • Automation vs accountability

DP Control Loop CO

  • DP purpose Automatic position and/or heading
  • Surge Fore-aft translation
  • Sway Port-starboard translation
  • Yaw Rotation about vertical axis
  • Setpoint Commanded position or heading
  • Feedback Correct measured error
  • Feed-forward Counter measured disturbance early
  • Vessel model Predicts dynamic response
  • Kalman filter Blends model and measurements
  • DP current Estimated residual environmental load
  • Thrust allocation Distributes force and moment
  • DPO Safety-critical human component

Sensors + Inputs CO

  • Gyrocompass Heading + turn rate
  • MRU/VRU Roll, pitch, heave
  • Wind sensor Wind speed and direction
  • Wind input Supports feed-forward control
  • Position reference Horizontal position measurement
  • Lever-arm correction Compensates sensor offset motion
  • Sensor voting Compares redundant inputs
  • Common-mode error One cause corrupts many
  • Command signal Controller requests thrust
  • Feedback signal Thruster reports response

Reference Check RE

  • Principle, path, geometry, health
  • Principle: truly diverse Path: no shared source Geometry: useful separation Health: stable residuals

Absolute vs Relative PRS RE

Absolute

  • Earth-fixed coordinates
  • DGNSS example

Relative

  • Target-relative offset
  • Target motion matters
  • Earth frame vs target frame

Reference Selector RE

  • Need earth-fixed position → DGNSS
  • Need moving-target offset → Relative PRS
  • Need underwater reference → Hydroacoustic PRS
  • Short seabed reference → Taut wire
  • Clear optical line → Laser PRS
  • Poor optical visibility → Microwave PRS
  • GNSS integrity doubtful → Non-GNSS principle
  • Need true independence → Different principle and path

Position References RE

  • DGNSS Absolute geographic position
  • Relative GNSS Target-relative position
  • Hydroacoustic PRS Underwater acoustic ranging
  • USBL Single topside transducer array
  • LBL Multiple seabed transponders
  • Taut wire Physical seabed reference
  • Laser PRS Optical target-relative range/bearing
  • Microwave PRS Radio target-relative range/bearing
  • Absolute reference Earth-fixed position
  • Relative reference Position from moving target
  • Reference independence Different principle and failure path
  • Reference geometry Diverse directions improve confidence

PRS Failure Clues RE

  • DGNSS jump Check satellites, corrections, datum
  • GNSS multipath Reflected signals distort position
  • Shared correction Potential common-mode failure
  • Hydroacoustic noise Thrusters can mask signals
  • Hydroacoustic aeration Bubbles weaken acoustic path
  • Sound-speed change Acoustic ray bending
  • Taut-wire deflection Current biases wire angle
  • Laser degradation Fog, rain, glare, blockage
  • Microwave degradation Interference or target multipath
  • Relative-target motion May mimic vessel movement
  • Wrong target Plausible but false position
  • Rising residual Reference disagreement increasing

Command Feedback PO

  • Command, feedback, compare; mismatch means investigate
  • Command: requested output Feedback: reported output Mismatch: possible fault

Open vs Closed Bus PO

Open bus

  • Sections separated
  • Fault containment favored

Closed bus

  • Sections connected
  • Protection must be proven
  • Isolation vs interconnection

Power + Distribution PO

  • Prime mover Drives alternator
  • Alternator Generates electrical power
  • Switchboard Distributes electrical power
  • Bus tie Connects switchboard sections
  • PMS Starts, synchronizes, shares, sheds
  • Spinning reserve Unused online generation capacity
  • Load sharing Balances generators
  • Load shedding Removes nonessential demand
  • UPS Maintains control continuity
  • Open bus Separates fault zones
  • Closed bus Connected power sections
  • Common auxiliary Can defeat redundancy
  • Blackout Loss of electrical supply

Thrusters + Allocation PO

  • Azimuth thruster Rotatable thrust direction
  • Tunnel thruster Transverse low-speed thrust
  • Retractable thruster Deployable azimuth unit
  • Main propeller/rudder Longitudinal thrust + steering
  • Allocation objective Meet force and yaw demand
  • Forbidden zone Blocks unsafe thrust direction
  • Thruster bias Opposed thrust improves response
  • Interaction loss Jets reduce useful thrust
  • Ventilation Air ingestion reduces thrust
  • Cavitation Vapour formation reduces performance
  • Thrust saturation No remaining allocation margin
  • Feedback mismatch Commanded and actual differ

FMEA vs Trials AS

FMEA

  • Analytical prediction
  • Defines failure effects

Trials

  • Physical verification
  • Proves expected response
  • Predict vs demonstrate

Classes + Redundancy AS

  • Equipment Class 1 Single fault may lose position
  • Equipment Class 2 Defined single fault tolerated
  • Equipment Class 3 Adds compartment failure tolerance
  • Redundancy Continues after defined failure
  • Independence Avoids shared failure path
  • Segregation Limits failure propagation
  • WCF Most severe defined failure
  • WCFDI Design basis for worst failure
  • Loss of redundancy Fault tolerance degraded
  • Equipment class Not activity approval

Capability vs Footprint AS

Capability

  • Predicted holding limit
  • Planning model

Footprint

  • Observed excursions
  • Recorded performance
  • Can hold vs did move

FMEA + Assurance AS

  • FMEA Predicts design failure effects
  • FMEA trials Validate predicted responses
  • Annual trials Verify continuing performance
  • DPVAD Documents guideline verification
  • Consequence analysis Continuously checks WCF survival
  • Capability plot Predicted environmental holding limit
  • Footprint plot Recorded position excursions
  • Change management Protects proven design basis
  • Hidden failure Testing reveals latent defect
  • Single point failure One fault defeats function
  • Common cause One event defeats redundancy
  • Proving record Evidence, not assumption

Redundancy vs Reliability AS

Redundancy

  • Survives defined fault
  • Requires independence

Reliability

  • Fails less often
  • May lack backup
  • Fault tolerance vs failure likelihood

CAM + TAM OP

  • CAM protects critical; TAM fits task
  • CAM: highest integrity TAM: risk based ASOG: limits + actions

CAM vs TAM OP

CAM/CAMO

  • Highest integrity
  • Matches FMEA redundancy

TAM

  • Task appropriate
  • Risk-based configuration
  • Critical protection vs task fit

Document Picker OP

  • Need activity limits → ASOG
  • Need critical configuration → CAM/CAMO
  • Need task-based configuration → TAM
  • Need generator combinations → TAGOS
  • Need failure boundaries → FMEA
  • Need validated responses → FMEA trials
  • Need live WCF check → Consequence analysis
  • Need environmental limit → Capability plot
  • Need actual excursion history → Footprint plot
  • Need onboard procedure → DP operations manual

ASOG + Operating Modes OP

  • ASOG Activity-specific limits and actions
  • CAM/CAMO Highest-integrity critical configuration
  • TAM Task-appropriate risk-based configuration
  • TAM consequence May allow reduced fault tolerance
  • TAGOS Generator + thruster strategy
  • DP operations manual Vessel-specific operating procedures
  • FMEA link Defines proven configuration boundaries
  • Status row Triggers specified operator action
  • Time to terminate Needed task shutdown time
  • Escape route Preplanned safe departure path
  • Bridging role Aligns vessel and charterer

Class vs Task Approval OP

Equipment class

  • Design fault tolerance
  • IMO classification

Task approval

  • Activity risk decision
  • ASOG limits apply
  • Capability basis vs permission

DP Readiness Gate OP

  • ASOG limits satisfied → Continue readiness checks
  • References not independent → Add independent principle
  • Reserve below requirement → Restore power margin
  • Thruster unavailable → Reassess WCF capability
  • Alarm remains unexplained → Do not commence
  • Escape route obstructed → Replan approach
  • Weather margin shrinking → Apply ASOG threshold
  • Teams not aligned → Rebrief communications

Planning + Watchkeeping OP

  • Task plan Define activity and hazards
  • Pre-DP checklist Verify system readiness
  • Location check Confirm position-reference agreement
  • Safe heading Balance loads and escape
  • Drift direction Know drift-on and drift-off
  • Reference status Health, independence, geometry
  • Power status Generators, bus, reserve
  • Thruster status Availability, limits, feedback
  • Alarm status Active, inhibited, standing
  • Weather trend Direction, rate, margin
  • Communications Bridge, engine, task teams
  • Watch handover Closed-loop status transfer

SAFE Response RE

  • Stop, alert, find cause, escape
  • Stop: apply ASOG Alert: Master + teams Find: verify evidence Escape: planned route

Drift-off vs Drive-off RE

Drift-off

  • Too little counterforce
  • Weather often dominates

Drive-off

  • Erroneous thrust
  • Control/input fault possible
  • Insufficient force vs wrong force

Alarm Triage RE

  • Many alarms arrive → Find first-out event
  • PRS values split → Cross-check independent references
  • Gyros disagree → Compare independent headings
  • Command differs feedback → Suspect thruster response
  • Bus frequency falls → Check generation deficit
  • Power reserve shrinks → Apply power procedure
  • Excursion rate rises → Prepare terminate/escape
  • Cause remains uncertain → Adopt conservative status

Alarms + Monitoring RE

  • Alarm Condition requiring attention
  • Acknowledgement Confirms receipt, not repair
  • First-out alarm Earliest detected initiating event
  • Alarm flood Many dependent alarms
  • Bypass/inhibit Protection intentionally reduced
  • PRS residual Reference disagreement measure
  • Thrust feedback Verify demanded response
  • Bus frequency Power balance indicator
  • Reserve trend Remaining power margin
  • Excursion trend Position error direction/rate
  • Consequence alarm Post-WCF holding risk

Acknowledge vs Resolve RE

Acknowledge

  • Confirms alarm seen
  • May silence annunciation

Resolve

  • Corrects condition
  • Restores safe state
  • Receipt vs remedy

Failure Response Picker RE

  • Drive-off develops → Transfer control per procedure
  • Drift-off develops → Terminate and escape
  • Blackout occurs → Blackout recovery procedure
  • Reference input fails → Use verified independent PRS
  • Wind input corrupt → Validate then isolate input
  • Thruster output corrupt → Isolate per vessel procedure
  • Fire or flood → Emergency and class response
  • Collision imminent → Emergency shiphandling

Failure Vocabulary RE

  • Drift-off Insufficient counter-thrust
  • Drive-off Erroneous commanded thrust
  • Blackout Electrical supply lost
  • Sensor drift Gradual measurement bias
  • Sensor jump Abrupt measurement step
  • Frozen signal Stale value appears stable
  • Latent failure Hidden until demanded
  • Common-mode failure Correlated channels fail together
  • Fault propagation Failure crosses intended boundary
  • Position loss Excursion exceeds safe limit

Incident Priorities RE

  • First priority Protect people and environment
  • Announce Alert Master and teams
  • Task status Apply exact ASOG action
  • Control mode Follow vessel emergency procedure
  • Escape Use preplanned safe route
  • Isolation Remove confirmed faulty element
  • Remaining assets Preserve healthy redundancy
  • Alarm reset Diagnose before clearing
  • Event log Record times, alarms, actions
  • After event Report, investigate, learn

Common Traps

NI vs NIMASA

  • NI issues DPO certificate ≠ NIMASA oversees Nigerian STCW

Certificate vs exam

  • Certificate spans multiple phases ≠ No single exam blueprint

Weights vs practice allocation

  • Official weights not published ≠ Local categories are editorial

Auto DP vs unmanned

  • Controller automates thrust ≠ DPO remains safety critical

Count vs independence

  • More references add quantity ≠ Different principles add independence

Class vs operation

  • Class describes fault tolerance ≠ ASOG governs activity limits

Alarm vs cause

  • Alarm shows detected condition ≠ Root cause needs diagnosis

Loss redundancy vs position

  • Redundancy can be degraded ≠ Position may remain temporarily

Capability vs forecast

  • Capability plot models limit ≠ Weather forecast predicts exposure

Footprint vs capability

  • Footprint records movement ≠ Capability predicts holding

Generic vs vessel-specific

  • Sheet gives principles ≠ Vessel procedures control action

Reset vs recovery

  • Reset may hide evidence ≠ Recovery restores safe state

Last Minute

  • 1. Scope = NI New Offshore Scheme
  • 2. No single universal exam blueprint
  • 3. All domain weights are unpublished
  • 4. Surge, sway, yaw are controlled
  • 5. DPO remains safety critical
  • 6. References need true independence
  • 7. Cross-check before rejecting PRS
  • 8. Track power reserve continuously
  • 9. Verify command against feedback
  • 10. Class does not approve activity
  • 11. FMEA predicts; trials demonstrate
  • 12. Capability predicts; footprint records
  • 13. ASOG supplies limits and actions
  • 14. CAM maximizes critical integrity
  • 15. TAM must fit task risk
  • 16. Acknowledge does not resolve alarms
  • 17. Find first-out alarm
  • 18. Distinguish drift-off from drive-off
  • 19. Keep escape route clear
  • 20. Use vessel emergency procedures
  • 21. Log facts before resetting
  • 22. Protect people and environment

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