Professional Notes

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Contents

The Amoco Cadiz: An Avoidable Disaster? 109 By Commander J. W. McCurdy,

ChS. Coast Guard (Retired)

What V/STOL “Really” Is (A Pilot’s View) 111 By Major D. C. Corbett, U.S. Marine Corps

Mission Conversions for the Missile Hydrofoil 115 By Vice Admiral Joseph J. McClelland,

U.S. Coast Guard (Retired)

The Amoco Cadiz: An Avoidable Disaster?

By Commander J. W. McCurdy, U. S. Coast Guard (Retired), Marine Consultant—Surveyor—and Member of the National Association of Marine Surveyors

The information relating to the tides &ven on the chart and in other publica- Oons should be studied, as it is of impor­tance for the navigator to know not only ‘he height of the tide above the plane of ^reference of the chart, but also the direction ^and force of the tidal current. ( American Practical Navigator, U.S. Navy’s Hydrographic Office, 1943).

According to news reports on 16 March 1978, the supertanker Amoco Cadiz sustained a machinery failure ^which left the vessel drifting off the coast of Brittany and ultimately onto the rocks near the fishing resort port °f Portsall. One wonders if the master °f this 1,100 foot, 228,496 ton dead­light, Liberian tanker ever paused to reflect on Nathaniel Bowditch’s words 'n conjunction with the ever-present Possibility of a machinery derange­ment which could—and did—leave his vessel helpless. Or, as he set a course to pass close by the Brittany littoral, did he recall that barely be­yond the horizon in 1967, the tanker Torrey Canyon had outraged ecologists Worldwide by spewing on the Cornwall coast a mere dribble of oil compared to the approximately 64,000,000 gallons of crude oil con­tained in the hull beneath his feet?

While the first of that 64,000,000 gallons of crude gushed into the sea in what has become the greatest acci­dental befouling of nature by man in history, the largest tankship in the world, the Batillus, bearing the French flag and carrying twice the load of the Amoco Cadiz, was on the same run: Persian Gulf to Le Havre. When will this constant repetition of tanker casualties followed by the abhorrent destruction of nature end?

Consultative Organization) to formu­late a plan for the control of tank ships. As set forth in my April 1968 comment on the Proceedings article, "Black Wake of the Torrey Canyon” (December 1967), the plan should:

►  Establish international tanker con­trol from port of loading to port of discharge

►  Relieve the master of the decision

Steps must be taken by IMCO (the U.N.’s Intergovernmental Maritime

Top left, holes in wasted plating, main deck. Discovered under masking tape and a coat of paint.

Top right, cement patch, main deck, in way of Butterworth plate. Note missinglbroken studs.

Middle left, air pipes to ballast tanks with frozenlmissingldeteriorated watertight covers.

Middle right, wasted fuel oil sounding pipe, main deck. Holes provided for ingress of seawater which could lead to the loss of propulsion power.

Bottom, engineroom ventilator’s damper rusted tight and turning gear frozen. If a fire broke out in the engineroom, the space could not be secured.

on how close to land he will risk his ship

►        Route tank ships with due regard for all the vagaries of weather, wind, current, and tides

►        Provide escort for monstrous crude carriers when within prescribed dis­tances from ports of departure and entry.

This plan, of course, is only part of the answer to the problem. The Amoco Cadiz was a comparatively new ship having been built at the Astilleros Es- panole, S.A., shipyard, Cadiz, Spain, in May 1974, under the classification rules of the American Bureau of Ship­ping. From the writer’s experience as a former classification surveyor and operating marine engineer, a ma­chinery derangement in a ship of the Amoco Cadiz class is highly unlikely, unless attended by neglect or incom­petence on the part of operating per­sonnel and—even, possibly—by clas­sification surveyors. Neglect in failing to carry out preventative maintenance programs and tests and/or the inability to recognize potential engine malfunc­tions are generally the causes of most engine room failures in today’s ships.

Negligence and incompetence are

aggravated by the material conditions often found in older vessels. In my June 1977 Proceedings professional note, “Flagging the Unsafe Liberian Flag Ships,” I faulted owners of cer­tain Liberian vessels for their neglec¹ to maintain seaworthy ships and non-exclusive surveyors retained by the various classification societies for failing to enforce the regulations laid down by the various international conventions for the safety of life at sea. Since the publication of this profes­sional note and within the past nine months, the pictures shown here were taken on board a flag-of-convenience ship. Unfortunately, the photographs do not depict unusual conditions. On the contrary, they are representative of conditions I have found on other such flag ships over the past five years.

Now, if these facts relative to flag- of-convenience ships have not im­pressed the reader, perhaps this one will: investigation has disclosed that forged, fraudulent, Liberian licenses for deck and engineer officers are for sale on waterfronts throughout the world—Rotterdam, Hong Kong, Singapore, and Panama! Recently, a maritime student was apprehended after obtaining a Panamanian captain s certificate authorizing him to com­mand the largest ships afloat. Again, one is compelled to wonder, how many impostors are standing watches in the engine rooms of supertankers.

> 

s

I i

At the risk of repeating myself, when will it all end? Surely the intro­duction of new and stringent rules for the construction of tankers, though these rules may have merit, is not the answer. The solution may lie in the constant, unrelenting, surveillance of tankers. Since many of these catas- trophies begin on the high seas and are beyond the control of the various sovereign states whose shores are being devastated, it is urged that this sur­veillance be conducted by sponsored supranational inspection teams.

To understand present-day V/STOL (vertical or short take off and landing) requires a discussion of the AV-8A Har­^rier and its capabilities. When we have done this, we can address what ^m*ght be called the “ new threat.”

The AV-8A is a transonic, single­^engine day/night, light attack aircraft ^w'th a secondary but significant fighter capability. It is powered by a Rolls Royce, axial flow, twin-spool, turbo fan jet, capable of producing 21,500 pounds of static thrust at sea level. The aircraft is 45.6 feet long, ^w*th a 25.25 foot wing span, and tveighs 12,400 pounds (empty).

The Harrier, like its current light ^attack counterpart, the A-4M, is equipped to carry and deliver an as­sortment of conventional stores from four wing stations and one center line station. Two externally mounted 10-mm. gun pods are located on the forward lower fuselage. In addition, infrared Sidewinder missiles can be carried on the two outboard wing sta- t!ons. Designed for varying combat situations, the aircraft has four takeoff

°- C- CORBETT

and four landing options: conventional takeoff (CTO), short takeoff (STO), roll­ing vertical takeoff (RVTO), vertical takeoff (VTO), conventional landing (CL), slow landing (SL), rolling vertical landing (RVL), and vertical landing (VL).

The aircraft’s small wing gives it “high wing loading,” which causes a large turn radius. High wing loading normally degrades performance for a conventional aircraft in an air-to-air combat role. The Harrier, however, is able to overcome any resultant dis­advantage through the use of its unique control devices. The aircraft is equipped with four variable sweep nozzles, capable of being rotated up to 98.5° (or 8.5° forward of the vertical), and three-position maneuvering flaps. The ability of the Harrier pilot to use both systems while airborne gives him a distinct maneuvering advantage over almost every fighter/bomber in the world today. In the past six years, AV-8AS have engaged nearly every type of aircraft in the Air Force, Navy, and Marine Corps inventories and, below 20,000 feet, have proven to be for­midable and worthy opponents, and in most cases superior.

The newest aircraft in the Marine Corps inventory has been accused of not being able to carry enough ordnance. But, the Harrier can take off with 7,000 pounds of ordnance and 5,200 pounds of fuel, at sea level and 85° in 1,850 feet of takeoff roll, and using the basic engine, with no JATO (jet-assisted takeoff), catapult, or other external types of assistance.

The aircraft’s weak ordnance reputa­tion stems from the lack of a multiple bomb rack (MBR) which is compatible with its wing station pylons. The British have MBRs for their Harriers, but MBRs were not procured as part of the Corps' Harrier package. The re­quirement for an AV-8A MBR has been identified and is being developed. But, like so many other things, fund­ing constraints have slowed develop­ment. I assume that if the Harrier were committed to conflict, an MBR would be immediately provided.

Recent articles have used the AV-8A to degrade many of V/STOL’s capabilities, sometimes without un­derstanding the systems involved. Many people seem to forget that the Harrier is a first generation aircraft. In the 1950s, the helicopter was not con­sidered a viable or long-range concept; we all know the merits of vertical envelopment today. At first, the A-4 faced the same type of criticism, and not many pilots thought very highly of its special weapons capabilities; today the A-4M is truly a lethal weapon. The AV-8A is not an end in

and of itself; it is the beginning of a new line of aircraft.

If the Marine Corps is to remain successful, then it must continually look to the future and analyze poten­tial conflicts that it will most likely encounter. The Corps cannot survive on past tactics. It must change to meet the “new threat.”

When examining various areas of the world in which the Marine Corps may be employed for limited or full- scale operations, it must be recognized that the Vietnam-style close air sup­port (CAS) is a thing of the past for at least three reasons:

► Air Defense Systems: Air defense is no longer a hodge-podge of unrelated antiaircraft (AA) gun emplacements. Rather, it is a network of highly sophisticated radars, guns, missiles, and communications. Add to this the rapid portability of the entire network and you have changed the whole com­plexion of air warfare.

The advent of missile systems which incorporate radar and optical tracking modes up to 10 miles or more for point defense changes the entire method of close air support. The enemy can quickly and effectively integrate missile systems which will cover all altitude spectrums. We, as attackers, are no longer confronted with merely a SAM-2 in the mid-to high-altitude ranges, but must now also consider and plan for a SAM-9 in the target area. The attacking force must also consider the integrated and overlapping radar-controlled AA gun system. Here again, the key is mobil­ity. Triple A (antiaircraft artillery) can and will move with the enemy to for­ward positions. Tank-, track-, and truck-mounted guns of devastating ac­curacy (many radar controlled) will move to protect known threat areas. Extensive communication nets will be established within this entire network of missile and gun emplacements, with the ability to rapidly advise all segments of the air defense system of the nature of the attacking force.

Air superiority, under present con­cepts and those of the Vietnam era, may no longer be achievable. Even without an enemy air-to-air threat, the previously described sophistication of ground-to-air defense systems pre­sents the aviator with problems he has rarely faced in the past.

►  Communications and Navigation Capabilities: Communications and elec­tronic or radar navigation cannot be taken for granted. In future conflicts, pilots will likely have to conduct entire mission scenarios under elec­tronic emission-controlled (EMCON) conditions. The enemy will use every means available to jam radio com­munications. To believe that we will have the freedom of the radio airways, as we did in Vietnam, is to invite dis­aster. The day of the extensive forward air controller’s briefing over the target area is probably over.

The American pilot has grown to rely on various types of navigational aids, including automatic direction finding (ADF), tactical air navigation (TACAN), instrument landing system (ILS), and radar, all of which are easily jammed or spoofed. The Marine Corps EA-6B does possess capabilities to over­come enemy jamming attempts, but there will be times when enemy jam­ming will, in effect, require EMCON operations. Are we, as a force in read­iness, capable of entering any would- be combat zone, flying at airspeeds in excess of 500 knots, and navigating to a pinpoint target, “without” naviga­tional aids?

►  Weather and Terrain: Finally, in what type of terrain and weather con­ditions will the Marine Corps be fight­ing? The variations and combinations can only be imagined as one looks at the troubled zones of the world, from deserts to jungles, from warm and foggy to cold and clear. The Marine Corps—its men and its machines— must be capable of fighting almost anywhere in the world.

The “new threat” requires new thoughts, innovative tactics, and air­craft capable of taking the war to the enemy. The AV-8A Harrier is one of many steps the Marine Corps has taken to counter the forces this coun-

^M«ONNELL DOUGLAS

^try is likely to face. Future v/STOL technology likely will supersede the A-4 and in all probability the F-4 and ^m°st other conventional aircraft.

The Marine Corps supports the ^v/STOL concept because it:

^ Provides rapid responsive airpower to the ground commander.

^ Improves basing flexibility.

^ Facilitates aircraft dispersal.

^ Creates an independent deployable

unit.

^ Operates within the Marine Corps’ existing command and control sys­tems.

The Marine Corps’ V/STOL plan is designed to meet the threat and satisfy the CAS mission. V/STOL gives the Marine Corps the aircraft it needs to develop new tactics for modern am­phibious warfare. Current V/STOL tac­tics have not been developed over- ⁿ'ght, nor are they complete. Just as the aircraft has undergone changes, so have the tactics, and they will con­tinue to be revised and improved as faults are found. More important, however, the tactics are valid.

In the amphibious assault, V/STOL aircraft will be employed in three phases—I-Operations from a Sea Base, U-Initial Operations Ashore, and III- Fully Operational Ashore.

In Phase I, the AV-8A leaves a sea base/platform (LHA, LPH, or LPD) armed and fully capable of launching a strike. If there is no immediate mis­sion, the aircraft lands at a forward site^[1] within 20 miles of the forward edge of the battlefield (FEBA) and uses ground loiter while awaiting a mis­sion. After the strike, the aircraft re­turns to the sea base/platform for re­arming.

As the battle moves inland, Phase II commences when an air facility^[2] is established. The forward site is still used and is constantly moving with the ground forces. The sea base/ platform provides heavy maintenance support, but will no longer be used to stage mission strikes.

As the situation ashore broadens, so do the demands on air operations. A main base^[3] may now be in use and targets may be struck from any or all three types of bases. The determina­tion of where the strike might ema­nate would depend on the ground commander’s needs and the response time required. Phase III is attained when the main base assumes the role of the sea platform and conducts heavy maintenance.

Considering the threat, it must be assumed that the enemy will not pro­vide an airfield for an attacking force. If friendly forces are able to capture an airfield, it is doubtful that there will be very much left of the actual field. Construction of airfields delays the movement of conventional aircraft forward with the battle. The AV-8A’s employment in forward combat areas, however, is not delayed for such con­struction. If almost any section of the field is left intact, be it mat area, taxiway, runway, or even an access road, the Harrier can move a facility- size unit ashore. Once the facility is established, AV-8A operations will begin in earnest.

The attack phase of a close air sup­port mission will be initiated, as in the past, by the forward air controller (FAC) through normal and time-tested lines of communication. The Harrier force, operating from a facility or a site, will be standing ready in a three-minute alert status. As the pilots receive the mission require­ments, engines are started and normal ground checks are completed. The mission brief will identify an initial point (IP) to which the pilot can navi­gate and, once there, can contact the FAC. As has been proven during sev­eral Marine Corps and joint exercises, the AV-8A can react to the ground commander’s needs in three to five minutes from the time of the request. In the case of the site, where aircraft are within 20 miles of the FEBA, the pilot monitors the FAC’s request (UHF or FM) and can start the aircraft’s engine and launch prior to receiving final clearance from the TACC (tactical air control center) or DASC (direct air support center). In this operation, there is no air loiter time, thereby eliminating exposure and waste of fuel.

For the CAS aircraft to fly at medium altitudes to within 30 or 60 miles of the FEBA and wait for a target request would be to invite disaster. Enemy missile systems would not allow such operations in combat. In­sert enemy fighters into the picture, and air loiter becomes a tactic of the past.

Flights to the target area will be low (250 feet or below) and fast (420 knots or more.) This approach coun­ters most radars’ ability to acquire adequate weapons firing data. Thus, the missile threat is considerably re­duced. Further, the low altitude and high speeds severely curtail the capabilities of the SAM-9 type weapons. Small arms fire presents lit­tle problem at low altitudes and very high airspeeds since sighting the air­craft and firing must be accomplished extremely rapidly. Although the AV-8A has only a pod-mounted elec­tronic countermeasures (ECM) capabil­ity at this time, ECM modifications have been developed for incorporation in the AV-8B. The AV-8A has flown against and defeated missiles of all types in the low altitude environment.

Again, as we consider the threat, visual navigation will be a require­ment, not something we do only on a part-time basis. In low-level flight, there will be little requirement for TACAN or ADF simply because the air­craft’s navigation equipment will not function properly much farther than 20 nautical miles from the radio bea­con. And since those same TACANs could so easily be jammed or spoofed, why bother? Training programs are being developed within the Harrier community to increase the pilots’ abil­ity to fly tactical formations at high speeds during low-level flight.

The IP is located 10 to 12 miles be­hind the FEBA. The aircraft will re­main low, using terrain to mask their presence when they reach the IP. The FAC will brief the flight as he always has, but he will include information for a low-altitude flight to the target pull-up point. That added information includes:               time/airspeed/heading to

pull-up point, a description of the area Surrounding the target, and the direc­tion and heading to turn during the pull-up to attack altitude. The flight leaves the IP for the target, at the pull-up the FAC directs the flight leader’s eyes to the target using ground reference points. The flight then initiates a one-run salvo attack and exits at low level. This method af­fords the absolute minimum of expo­sure time for the attacking aircraft and, thus, greatly reduces the possibil­ity of losing the flight to gun or mis­sile fire. Certainly, should the ground situation dictate, more than one run could be made, but the risk must be weighed against the actual need and the increased possibility of losing close air support capabilities.

Using this system, the Harrier can always bring weapons to bear on the enemy. The total tonnage of bombs on target will be determined by the reac­tion time the ground commander de­sires. If that need is immediate, then an AV-8A may be launched from a for­ward site. True, the amount of bombs carried may be less, due to the vertical takeoff, but the ground commander can expect bombs on target in five to 10 minutes after making his request.

An offensive combatant force may expect to encounter enemy aircraft in the next conflict. If V/STOL is a valid concept, it must continue to provide CAS even with a threat from the air. And Marine AV-8A squadrons have a fighter role. Realistically, the AV-8A cannot operate as an interceptor—a mission best left to the F-4 and F-14 which have large fuel capacities. The AV-8As will look to the fighter com­munity for high-altitude protection and interception. However, for enemy air below 15,000 or 20,000 feet, the Harrier can fend for itself, provided it is given warning of the impending threat. Due to the small size and the camouflage paint scheme, at 250 feet and 420 knots, the Harrier is difficult and sometimes impossible to see from higher altitudes. Should an enemy fighter attack, he flies into the Har­rier’s backyard. Certainly the AV-8A must counter the air-to-air missile threat, as do all other attack aircraft. In fact, squadron-level studies have shown that the high wing over the nozzles effectively masks the infrared print of the aircraft. This is particu­larly true in an angle of bank. Dop­pler- and radar-guided missiles can be defeated, if proper combat formation tactics are used. Acceleration and de­celeration times, with the use of noz­zles and maneuvering flaps, give the AV-8A air-to-air teeth which bite and bite hard.

The entire V/STOL scenario has been discussed except inflight refueling- Again, considering the threat, where will air refueling be accomplished? Certainly not in the area of battle! If we combine the air-to-ground threat and the air-to-air threat, then slowing to 200 knots at even a relatively low altitude, say 3,000 feet, may well prove fatal. Instead, the Harrier is ca­pable of landing at several basing facilities and sites. In other words, fly to your fuel within the battle area, out of reach of guns and missiles.

The AV-8A Harrier meets the threat with realism and forethought; it matches defensive enemy tactics with highly versatile offensive tactics; and it can survive.

V/STOL is the method the U.S. Marine Corps will employ to success­fully execute its amphibious warfare missions. V/STOL (AV-8A and AV-8B) is the wave of today and of tomorrow. ^{1 * 3}

Mission Conversions for the Missile Hydrofoil

% Vice Admiral Joseph J. McClelland,

■ S. Coast Guard (Retired), formerly associated with Boeing Marine Systems •ind now Vice President of the Matson Navigation Company

The missile hydrofoil USS Pegasus (PHM-i) _was commissioned in July ^977 and joined the Pacific Fleet’s Destroyer Squadron Nine in August. The Pegasus’ performance as an ad­vanced small fast warship may well determine the future of hydrofoils in ^cBe U. S. Navy. She will be testing •operational concepts and developing tactics, as well as providing the means for continuing needed research in hy­drofoil technology. The results of her efforts will greatly influence her future ^Use and that of her five planned sister

ships.

The U. S. Navy has examined po­^tential uses for hydrofoils but has not yet thoroughly tested the craft in dif­ferent mission areas, even though a number of developmental vessels have been built in the last decade and a half. These earlier U.S. hydrofoils in- elude the High Point (PCH-l), Dennison, ^la in view (AGEH-l), Tucumcari (PGH- ²)> and Flagstaff (PGH-l).

Meanwhile, other navies have been developing their own hydrofoils. Canada built the Bras D’or (FHE-400), a 15 1-foot, 180-ton vessel, to "establish ^ln practice the feasibility of an ocean­going hydrofoil of the proposed size and characteristics, and to evaluate the Prototype as an ASW system.” The feasibility of operations in open-ocean conditions was confirmed, but the ac­tual testing of the ASW systems was suspended because of a change in na­tional priorities.

The People’s Republic of China has been building the "Hu Chwan’’ (White Swan)-class hydrofoil torpedo boat since about the mid-1960s. This *s a 70-foot, 45-ton vessel with a bow subfoil and a surface-piercing main foil set back approximately one-third of the hull length from the bow. At high speed the greater part of the hull rises clear of the water. Some 60 to 70 of these boats are in service with the

PRC Navy and a substantial additional number have been lent or leased to other countries, including 32 to Al­bania, six to Pakistan, six to Ro­mania, and four to Tanzania.

The Italian Navy has a hydrofoil missile craft which is an improved ver­sion of the Tucumcari, built under license from Boeing. The Sparviero (Swordfish)-class is 80 feet in length, weighs 63 tons, and carries two fixed-Otomat missile launchers. She also has one dual-purpose 76-mm. automatic Oto Melara antiaircraft gun. Production of nine more craft is planned.

The Soviet Navy now has three classes of combatant hydrofoil vessels. The “Pchela” is an 88-foot coastal pa­trol vessel of 70 tons which carries two twin machine guns and depth charges. Twenty of these are in service. The “Turya,” a 124-foot torpedo ASW ves­sel of 200 tons, carries four 21-inch torpedoes and 25-mm. and 57-mm. twin guns. There are 24 boats of this class. The newest and most advanced Soviet hydrofoil is the "Sarancha-”class submerged-foil, gas turbine-powered missile craft. She is 140 feet in length, displaces 235 tons, carries four SS-N-9 antiship missiles, two SA-N-4 surface-to-air missiles, and a 23-mm. six-barreled rapid-fire gun.

The Philippines has four hydrofoil patrol craft in the 30-ton range armed with machine guns.

This brief summary illustrates that hydrofoils currently assigned surface warfare missions are configured as fast torpedo boats, gunboats, and missile ships, with some ASW and AAW capabilities. Yet, hydrofoils have per­formance characteristics which give them the potential for serving in other naval warfare missions, within the size and powering specifications of existing craft. These characteristics are:

► Speed—in excess of 45 knots, foil- borne (The PHM’s actual top speed is classified.)

►  Maneuverability—banks into turn, high turn rate, and completes 360° turn into initial wake

►  Low water noise level—hull clear of water when foilborne, and with water jet propulsion, no propeller noise

►  Unique pressure characteristics from foils—radically different from that of conventional hulls

►  Superior crew comfort and efficiency—improved platform stabil­ity, foilborne

With these characteristics in mind, the Pegasus-class PHM will be used to examine possible design variations for hydrofoils.

Antisubmarine Warfare Configura­tions: The PHM is the only U.S. Navy surface combatant faster than the fast­est submerged nuclear submarine, re­gardless of seas up to Sea State 5 which limits foilborne operation. This characteristic provides an unsurpassed potential for the hydrofoil as a sub­marine hunter and killer. The major problem associated with the design of a hydrofoil ASW ship is the sensors, not the platform. Current state-of- the-art underwater search and classifi­cation sensors for such ships still lag behind the capabilities of submarines for avoiding detection and evading at­tack.

The capabilities of hydrofoils for the ASW mission may be reviewed in de­tail by applying the requirements for ASW ships as catalogued in Modern Ship Design (Naval Institute Press, 1970) by T. C. Gillmer.

►  A steady platform: No other ASW- capable ship is as steady in rough seas as PHM (in foilborne mode).

►  ABC warfare compatibility: This re­quirement can be met without any loss of performance.

► Fast reaction fighting capability: This will be achieved by a combined command and control center, with a set of functionally interchangeable display and control consoles operating through a central computer system. The central data processor must be ca­pable of handling multiple targets. Since the hardware exists, this re­quirement can be met.

Y Fast and accurate deployment, ren­dezvous, and station-keeping with maximum radio and radar silence: High speed and advanced electronic navigation equipment meet this re­quirement.

►  Escort and hunter-killer role: Speed enables sprint and drift tactics to be employed effectively at high speeds of advance, but limited fuel capacity re­stricts range. However, conventional escorts also require refueling on long­distance escort assignments.

►  Ability to be replenished at sea:

PHM has this capability.

► Weapon systems requirement: A primary ASW suite and a minimum point defense are adaptable to the PHM for general-purpose use.

The requirement for a fast reaction fighting capability can only be met with a totally integrated system. Fig­ure 1 shows such a system, based on the CSS 280 weapon control system employed in Canada’s Tribal-cla^sS DDHs. This system uses existing hardware and integrates the equip­ment through interface links into a complete PHM-ASW command and control system.

Even though many effective light­weight sonars and ASW weapons are now available, the PHM’s space and weight limitations prevent the devel­opment of the optimum ASW config­uration. As always in ship design, compromises have to be made. Two families of sonars available to the PHM are: (1) the long-range sonars such as variable depth sonars (VDSs) having a very limited towing speed capability, and (2) the high-resolution sonars able to sense echoes at medium to high speeds, but only at short range.

The long-range sonar configuration is depicted in Figure 2. The gun fire control system has been revised to in­clude a torpedo fire control system- The Mk 92 system enables the ship to track one air, one surface, and one subsurface target. The underwater sen­sors are represented by a Westing- house HS 1001 VDS or a towed passive array handled by a “Fathom” winch and a forward pod-mounted continu­ous transmission frequency modula­tion (CTFM) sonar. The ASW armament consists of two Mk 32 triple torpedo tubes for a total of six Mk 46 ASW torpedoes, plus a Bofors 375-mm- ASW mortar. The surface-to-surface capability has been reduced from eight to four Harpoon missiles, mounted on the port side. The Emerlec 30-mm- gun provides the ship's air defense capability and contributes to surface warfare capability. The full-load dis­placement of this configuration is only 15 tons over the standard 235.

Figure 3 shows the high-resolution sonar configuration. This coastal pa­trol ASW version retains the full surface-to-surface capability with eight

Harpoons. The Mk 92 gun fire control system and the 76 -mm. gun are re­placed with the Honeywell H930 and the Emerlec 30 mm., a lighter and ^m°re compact gun fire control system ^and gun. The purpose of these changes *s to save weight. This allows the in­stallation of a CTFM sonar in a foil- tnounted pod for attack, and a modu- ^ar dipping sonar installation for search and classification, and six Mk 6 torpedoes. The sonar module con­sists of three units: the transducer in a Watertight dome, a hydraulic power Winch, and a rack with all the electric hardware. These components are ^oused in a trailer-type box situated ^on the 01 level. This configuration weighs 235 metric tons.

Mine Warfare Configuration: The last ^nial^or advance in mine warfare was the deployment of helicopters with mine­sweepers, which occurred 15 years ^ago. Lieutenant J. M. McCoy ably de­scribed the situation in his article ti­ded, “Mine Countermeasures: Who’s Fooling Whom” (July 1975 Proceed- ^,ngs). Anything that can destroy a ^01,06 faster, cheaper, and in a safe banner would be a welcome addition ^t0 the fleet. Admiral B. McCauley, who was commander Task Force 78 during Operation End Sweep, the tfdnesweeping operation off North Vietnam, summarized the need for new platforms in his March 1974 Pro­ceedings article by saying:

Even with the success of the helicopter sweeping, End Sweep demonstrated again the need for surface minesweepers. . . . The MSO can sweep to much greater depths than the helo. It currently has the only useful system against a pressure mine, the mine hunting sonar. Pressure mines must be found—and then destroyed or avoided.

■ . . . Both the helicopters and the surface ship will require future de­velopment. A shift to hydrofoil or hovercraft can offset to some degree the speed limitations and vulnera­bility of present surface ships.”

The PHM has the speed advantage to offset many of the limitations and the vulnerability of present ships for toine countermeasures (MCM) opera-

BOFORS 375 mm ASW

EMERLEC 30 mm GUN . LN06HP NAV RADAR

AN/SPS-58V AIR SEARCH RADAR -HW-120 TRACK RADAR

-(2) TRIPLE MK32 £) MOOS

TORPEDO TUBES

CD Ship 't prstturs lignsture - variition of hydrottltic prsnurt ® Vsrlstion of tound prsuure

© Variation of Earth’s magnetic field underneath ship with permanent magnetism

© Variation of Earth's magnetic field underneath degaussed ship

Note:      Magnitudes shown era not relative. Only phase relationships are approximate.

tions. The hydrofoil’s aluminum con­struction together with stainless steel struts and foils creates a magnetic sig­nature completely different from that of a conventional displacement vessel.

In 1974, tests were conducted to obtain acoustic, pressure, and mag­netic signatures of the High Point as a function of speed and operating modes in shallow waters. The results of these tests showed that a hydrofoil has a typical signature that cannot be iden­tified with any displacement vessel. Figure 4 shows how the pressure, sound, and magnetic signatures of a submerged-foil hydrofoil compared to those of a conventional ship. The phase presentations are only approxi­mate. The difference in pressure signa­ture illustrates a very interesting phenomenon. The hydrofoil pressure gradient shows only two “zero- crossings” instead of the four shown by a displacement vessel. This means that no foilborne hydrofoil would det­onate a depression mine, which is the most difficult mine to sweep.

The measuring of the pressure and influence fields of two hydrofoils steaming in formation has not been accomplished. Such a test would de­termine the longitudinal and lateral spacings of the two foilborne craft so that the influence field change would be similar to that of a displacement ship. This could provide a solution to the problem of detonating a pressure mine.

Thus, the high speed, small dis­placed water volume, distinct under­water pressure signature, and smaller and different magnetic influence of the hydrofoil make her well suited to the mine countermeasures mission. Iⁿ Europe, the modern mine countermeas­ures which have been developed are generally based upon a common prin­ciple: the MCM vessel searches for the bottom-laid influence mine with her mine-hunting sonar, and, once found, a remote-controlled craft, surface or submersible, is piloted to the mine to place a destructive charge.

Figure 5 shows PHM armed as a MCM vessel (MCMH). The weight of the MCM equipment is less than the normal armament suite, so the dif­ference could be carried as fuel, thus extending the PHM’s range. In this configuration, the MCMH is equipped with the British “Spiny Cat” system- two remote-piloted catamaran mine disposal vehicles tow a submersible weapon carrier. The MCMH transmits a radio signal to the “Cat” which places the device over the mine where it transmits signals through the towing and control cable. The sonar trans­ponder placed below the PHM’s for­ward foil assists the mine hunter m identifying the submersible weapon carrier and steering it within the sonar beam. When the slant range of the target and the weapon carrier coin­cide, the mine-hunting operator re­leases the charge. The carrier is now buoyant and rises to the surface.

Minelaying Configuration: Minelay­ing does not require any sophisticated transport and delivery system. Mines can be laid by airplanes, submarines, and all kinds of surface vessels from hydrofoils to ferryboats. The only req­uisites are accurate navigation equip­ment, adequate stowage space, and support and tie-down equipment.

Mines are normally stowed and se­cured on expendable carriages. The carriages rest on small steel wheels which fit in or on mine rails secured to the deck of the launching platform. Standard NATO mine rails can be fit-