12.3 Task Appropriate Mode (TAM)

Not every DP hour is a dive under a platform

If CAM were mandatory for every minute a thruster was in auto, vessels would burn unnecessary fuel, accumulate hours, and still not improve safety when the task risk is low. Task Appropriate Mode (TAM) exists for that reality: configure the plant appropriately for the task, even when that configuration would not guarantee position-keeping after the design worst-case single failure.

TAM is often misunderstood as “lazy CAM” or “broken redundancy.” Correct teaching treats TAM as a conscious, authorised risk decision with documentation — the counterpart to CAM, not its careless cousin.

TAM definition (exam-stable)

In TAM, the DP system may be configured such that a single failure could exceed the residual capability associated with the usual WCF case and could cause loss of position. That risk is accepted because the consequence of an excursion for the present task is judged acceptable (open water, no divers, no close structure, recoverable delay).

[!IMPORTANT] Exam trap: “TAM is more redundant than CAM.” False. TAM generally accepts less residual protection relative to critical-work CAM. Another trap: “TAM is only used during annual DP trials.” TAM is an operational mode for lower-risk tasks, not a trials-only label.

Why companies allow TAM

The key word is accepted. TAM without approval, without ASOG, and without understanding post-failure drift risk is just under-configured DP.

Typical TAM plant picture

Vessel procedures differ, but exam-level contrasts with CAM are:

TAM does not mean disable all references, trip all generators, or abandon watchkeeping. It means the redundancy bar is set to the task, and the crew has thought through “if we black one side or lose a thruster group, we may drift — and that is acceptable here.”

Contrast table: CAM vs TAM (memorise)

Intentional and documented — the non-negotiables

For TAM to be legitimate:

1. Task risk assessment shows excursion is acceptable (no divers in water, adequate sea room, no SIMOPS that turn drift into disaster).
2. Company procedure allows TAM for this activity class.
3. Master / DP authority (and client if required) approve the mode.
4. Configuration is logged — bus state, gensets, thrusters, PRS, defects.
5. ASOG for the task is active with clear red abort criteria (weather, proximity change, start of critical phase).
6. Trigger to leave TAM is pre-agreed — e.g. “on dive bell run, switch to CAM and verify before lock-out.”
7. Crew briefing so nobody assumes CAM residual when the plant is TAM-lean.

If any of those are missing, examiners and incident investigators will treat the setup as uncontrolled degradation, not TAM.

Exam scenarios: choosing the mode

Scenario 1 — Divers deployed. Always CAM (or stricter). TAM’s acceptance of post-failure loss of position is incompatible with divers in the water.

Scenario 2 — Open-water ROV standby 5 nm from nearest asset, calm weather, company TAM procedure. TAM may be justified: fewer gensets, possibly closed bus, documented ASOG. If ROV moves into a structure’s 500 m zone for close inspection, escalate to CAM before the critical approach.

Scenario 3 — Heavy lift. Approach and rigging may allow elevated readiness; the critical lift phase is CAM. After the load is secure and clear, documented return to TAM may be allowed for standby.

Scenario 4 — “Fuel saving” inside the 500 m zone. Candidate chooses TAM with reduced redundancy under the platform. Wrong. Proximity hazard demands CAM-type residual protection regardless of fuel price.

Scenario 5 — Generator trip in TAM. Position may start to degrade more than CAM would allow. Correct response is still ASOG-driven: assess whether residual risk remains acceptable; if not, restore plant or abort the (even low-risk) task and move clear. TAM is not “ignore failures.”

Scenario 6 — Mislabelled mode. Bridge says TAM but worksite starts diving without reconfiguration. That is an operational control failure. Mode labels must track real activity phase changes.

Operator decision flow (simple)

Is a position excursion after single failure unacceptable
(divers, close structure, critical lift geometry, client mandate)?
        │
        ├─ YES → CAM (+ tight ASOG) → verify plant residual → start critical work
        │
        └─ NO  → Is company TAM allowed and approved for this task?
                    │
                    ├─ YES → Configure TAM, document, brief, use TAM ASOG
                    │         Watch for task creep → re-enter CAM when risk rises
                    └─ NO  → Default to CAM / higher redundancy until approved otherwise

Worked comparison narrative

A DP construction vessel spends the morning in open water calibrating systems. Engineers run a lean generator set and closed bus under TAM; ASOG weather limits are wide; an excursion would only delay the schedule. At midday the vessel enters the 500 m zone for platform approach. Before the approach checklist completes, the DPO and Master exit TAM: open bus-ties, start additional gensets, enable full PRS set, activate the proximity CAM ASOG. After work, clear of the zone, they may return to TAM with a logged decision. The skill is mode switching with activity phase, not permanent loyalty to either label.

Exam traps for TAM items

Linking TAM to ASOG and CAM

• ASOG still governs yellow/red actions in TAM; bands differ, discipline does not.
• CAM is the default mental model when consequence is high; TAM is the authorised exception when consequence is low.
• WCF / consequence analysis still matter: in TAM you may accept a warning that WCF would lose position — but you must know that is the deal, not discover it after divers lock out.
• Power chapters (open/closed bus, spinning reserve) supply the technical content of what you are accepting.

Bottom line: TAM intentionally accepts that a single failure may exceed residual capability and cause loss of position when the task risk allows it. It is an efficiency and flexibility mode that remains deliberate, approved, and documented, with an ASOG and a clear path back to CAM when the work becomes critical. On the exam, match the mode to consequence, not to fuel price alone.