This Plan Review Guideline provides guidance and information for carrying out successful stability test and submitting stability test procedures to the MSC.

It applies to vessels certificated under any subchapter of 46 CFR.


In order for the US Coast Guard to issue a stability letter to a vessel with approved lightship characteristics, a stability test must be performed. Namely, an operator must ensure that the requirements of 46 CFR 170.185(g) are included in the procedures:

  • Identification of the vessel to be tested;
  • Date and location of the test;
  • Approximate draft and trim of the vessel;
  • Condition of each tank;
  • Estimated items to be installed, removed, or relocated after the survey, including the weight and location of each item;
  • Schedule of events;
  • Person or persons responsible for conducting the survey.

Vessel Floating Condition

Regarding the ships floating condition, that includes the following:

  • The vessel should be moored and free floating;
  • Trim should be less than 1% of the length between perpendiculars (LBP), unless the hydrostatic properties for the as-surveyed condition include the actual trimmed amount;
  • The ship’s initial heel should not surpass ½ degree;
  • A hydrometer of appropriate scale should be available to measure the specific gravity of the water at the time of the inclining, as well as any onboard liquid loads.

In addition, at least five separate and approximately equally spaced freeboard readings should be taken on each side of the vessel and plotted on a profile view of the vessel at the time of the survey.

Vessel survey

As for the survey of the vessel itself, the US Coast Guard emphasized seven key points:

  1. A survey of the vessel should be performed in the presence of the US Coast Guard witness to make sure the vessel is at least 98% complete;
  2. The list of weights to add/remove/relocate should be supplied to the US Coast Guard witness before the survey;
  3. Ensure on-board personnel are limited to individuals essential to conducting the stability test. Their overall weight should remain constant throughout the test and should be recorded for each individual rather than estimated;
  4. All empty tanks and voids should be open, ready for inspection, and have a gas free certificate;
  5. Ensure that the tankage specified in the procedure is acceptable per reference (d). The number of slack tanks should be minimized. No free surface correction will be allowed for loose water (in bilges and voids) or excessive slack tankage. Free surface correction for slack tanks may only be permitted if the slack tanks are of regular cross section and either: 20 to 80% full if they are deep tanks; 40 to 60% full if they are double-bottom tanks;
  6. The vessel’s downflooding points should be identified and their locations clearly delineated in the stability test results submittal;
  7. The USCG witness should initial each page of the rough field notes after verifying the recorded data.

You may see more information in the PDF below