Escort Tug - Operating Speed Window
Operating-speed window of an escort tug based on rudder-direct / indirect assist mode - the governance of escort missions for laden tankers.
Direct-mode range
0–8 kn (direct mode)
Indirect-mode range
6–12 kn (indirect mode)
Formula, assumptions, and limits
$$v = f(\text{tug type}, \text{assist mode})$$
Indirect mode uses tug as rudder, increasing braking force at higher speeds via hydrodynamic lift of the hull. OCIMF / ISPO escort requirements mandatory for laden tankers in some ports.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $ASD$ | Azimuth Stern Drive | - | tug type |
| $Indirect$ | Tug hull used as rudder at speed | - | tug operation |
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