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95 and other considerations that quickly reduce righting arm as a vessel heels. To address this topic, USCG has added Section 170.173, Criterion for vessels of unusual proportions. The IS Code uses righting arm curve-based criteria for vessels on international voyages. With both the 170.173 Criterion and the IS Code criteria using required minimum areas under the righting arm curve to key heel angles, the suitability of the vesselâs long-range stability can be better assured. The simplicity of Section 170.170 is convenient for many smaller, coastal vessels and it does provide a check of the impact of wind on vessels with large superstructures or other features that make them prone to wind heel (e.g., large awnings on small passenger vessels). However, applying Section 170.170 as the sole method of assessing vessel stability raises concerns, because of its limitations. As discussed in Appendix G, supplementing Section 170.170, when applied, with another method of stability assessment could provide a truer picture of the sufficiency of a vesselâs stability over the full range of heel. Other examples of legacy initial GM-based criteria in Subchapter S are the passenger heeling criteria, Section 171.050, and the towline pull criteria, Section 173.095(b). The passenger heeling criteria, which is the only intact stability criteria in Subchapter Sâs Part 171 Passenger Vessels regulations, calculates a minimum required initial GM from the number of passengers, the width of the passenger decks, and the vesselâs freeboard. The towline pull criteria is slightly more sophisticated, utilizing the vesselâs horsepower, number and size of the propellers, effectiveness of the rudders, and the tripping arm from the towing bitts to the propellers. As with the weather criteria previously discussed, the same problem exists with these criteria as the minimum required initial GM does not ensure the vessel has sufficient stability over a range of heel angles, which is critical to a vesselâs stability. APPENDIX E
96 INSIGHT INTO THE REGULATORY UPDATE PROCESS: EXAMPLES OF THREE PAST MAJOR UPDATES OF SUBCHAPTER S In attempting to update Subchapter S, it is valuable to review past efforts to provide future insight on potential issues. During the more than 30 years since Subchapter S was adopted in 1983, there have been three regulation projects centered on the subchapter. Although various parts of Subchapter S have been amended in association with other regulatory projects, the following three projects provide a sense of the effort involved in amending the regulations. International Maritime Organization (Dry) Cargo Vessel Damage Stability Most U.S. Flag cargo vessels were built to the one-compartment standard (based on the U.S. Maritime Administration [MARAD] Design Letter Number 3) for decades, but there was no international (or Safety of Life at Sea [SOLAS]) standard. This was of concern as the U.S. fleet shrank and most of the cargo vessels coming into the United States were foreign cargo vessels. Damage stability had been on the International Maritime Organization (IMO) agenda for more than 10 years, but it was not until 1987 that the Marine Safety Center (MSC) raised the priority and a draft circular on subdivision and damage stability of dry cargo ships was completed. This circular was only possible due to its use of a âprobabilisticâ methodology, as compared to SOLAS 1974 for passenger ships, which had been âdeterministicâ since the early 1900s. In May 1990 MSC adopted resolution MSC.19 (58) into SOLAS Chapter II-1, part B-1, subdivision and damage stability for cargo ships that applies to ships constructed after February 1, 1992. To complete the U.S. regulatory process, the U.S. Coast Guard (USCG) issued the final rule in April 1993, with new regulations in 46 CFR 174 referencing resolution MSC.19 (58). It was not a significant change from a Subchapter S perspective, but it was significant to cargo ships operating in U.S. waters and internationally. The final rule only amended Subchapter S, not
97 33 CFR 160 (Subchapter P, Ports and Waterways Safety), because foreign vessels entering U.S. waters are SOLAS vessels and thus must comply with resolution MSC.19 (58). SOLAS 90 and IMO Passenger Damage Stability Upgrades to the Domestic Fleet SOLAS 1974 had only the minimum of requirements for passenger ship damage stability. With the March 1987 flooding and capsizing of the British ferry, Herald of Free Enterprise, IMO undertook an âemergencyâ program of passenger ship safety. In extremely rapid time, IMO MSC adopted the Herald Amendmentsâresolutions MSC.11 (55) and MSC.12 (56), in April and October 1988, respectively. See Chapter II-1, part B, subdivision and stability, Regulation 8 (stability of passenger ships in damaged condition). These amendments were significant for ships constructed after April 29, 1990, which had to meet the following requirements: ï· The righting lever (GZ) must have a minimum range of 15 degrees beyond angle of equilibrium. ï· There must be 0.015 meter-radians under the curve. ï· The heeling moments to be calculated are maximum of passenger crowding, lifeboats fully loaded and swung out, or wind. ï· The maximum GZ for intermediated stages of flooding is at least 0.05 m and a range of at least 7 degrees. These requirements, referred to as SOLAS 90, are still considered the major breakthrough in the 20th century for protecting passenger vessels in the damaged condition. USCG realized that the domestic passenger fleet (Subchapters K and T boats) were vulnerable as well and initiated a regulation project, with a Notice of Proposed Rulemaking (NPRM) published in February 1990. The NPRM included requirements for draft indicators, on- board computers to calculate stability, periodic stability tests, the closing of loading doors before
98 going to sea, and the stability of new passenger ships after damage. The damage stability standards proposed were for Type II passenger vesselsâÂ§ 171.080(d) and (e), minimum damage stability survival criteria for new passenger vessels that would provide a reasonable probability of not capsizing when subjected to flooding scenarios. The proposed regulations carried the SOLAS 90 in-force date of April 29, 1990. The proposal covered both SOLAS and vessels on domestic routes not subject to SOLAS. After 2 years of interaction with the operators and designers, additional analyses for K and T boats, and numerous public hearings, the final rule was published in October 1995. Due to the comments from the naval architects who design the U.S. fleet of small passenger vessels, a workable set of relaxed survival standards was proposed and agreed to for those domestic passenger vessels operating in protected and partially protected waters. The revised Â§ 171.080(f) ensured a consistent level of safety matching that of the full SOLAS 90 standards. The lesson was that simply taking amendments to SOLAS and bringing them directly into the CFR was not appropriate. Increasing Passenger Weights for Small Passenger Vessels The last major revision to Subchapter S followed the capsizing of the small passenger pontoon vessel M/V Lady D in the Inner Harbor of Baltimore, Maryland. In the final rule published on December 14, 2010, the Assumed Average Weight per Person (AAWPP) was established.25 In Subchapter S, the passenger heel (Â§ 171.050) was amended allowing the IS Code, but with the AAWPP to be used in the calculations. Other amendments included the new reference (Â§ 25 See Federal Register, Passenger Weight and Inspected Vessel Stability Requirements; Final Rule. Vol. 75, No. 239, Dec. 14, 2010, pp. 78063â78092 (https://www.gpo.gov/fdsys/pkg/FR-2010-12- 14/html/2010-30391.htm).
99 174.360) for dry cargo ship damage stabilityâIMO harmonized damage stability. In Subchapter T, pontoon boats were required to have a stability letter (Â§ 178.210), a simplified stability proof test (Â§ 178.330), and stability standards (Â§ 178.340). Considerable updates to Subpart C, intact stability standards, were promulgated: Â§Â§ 178.310, 178.320, and 178.325 were completely revised, with references to Parts 170 and 171 of Subchapter S. This significant regulatory update to Subchapter S was not easy and may have been adversarial at times, but once all parties became involved, the process worked. The outreach and direct interaction with the designers of small passenger vessels and the Passenger Vessel Association led to a successful conclusion, although without a lightweight verification requirement.