United States Fleet Anti-Submarine Instructions

Part III - Joint Air-Surface Action

  3010 Operational Control 3-1
    3011 Information Required 3-1
    3012 Tactical Control 3-1
    3013 Carrier Present 3-1
    3014 Aircraft Reporting 3-1
  3110 Coordination Required 3-1
  3120 Limitations and Capabilities 3-1
    3121 Coordination Requirements 3-2
  3130 Air/Surface Coordination on Search 3-2
    3131 A/C Sono-Buoy Contacts 3-2
    3132 Sono-Buoy Use with Surface Craft Present 3-2
    3133 A/S Vessel Closing Contact Instructions 3-2
    3134 Action of A/S Vessels Arriving at Contact 3-2
    3135 Surface Craft Interference with Sono-Buoys 3-3
    3136 Standard Sono-Buoy Orientation 3-4
  3140 Designation of Target 3-4
  3150 A/C Emergency Procedure 3-5
  3160 Communications 3-5
    3161 Frequencies Unknown and Essential Points 3-5
  3210 Basic Instructions 3-5
  3220 Stationing of Carrier Screens 3-5
    3221 Employment of Escorts 3-5
  3230 Ship at Radar Range 3-5
  3240 Carrier After Contact 3-5
    3241 Movements of Carriers 3-5
    3242 Movements Following D/F or Ground Wave 3-5
    3243 D/F Data to CominCh 3-5
  3250 Succession to Command of Carrier Task Group 3-6
  3260 Succession of A/C Director Duty 3-6
    3261 Water Landings in Emergency 3-6
  3270 Carrier Task Group Search Plans 3-6
    3271 When Plans Will Be Used 3-6
    3272 Flight Plan 3-6
    3273 Carrier Plan With Good Fix 3-7
    3274 Carrier Plan With Indefinite Fix 3-7
3300 AIRSHIPS 3-8 -- 3-9
  3310 Airships in Joint Operations 3-8
  3311 Airship Use of Sono-Buoy 3-9
  3312 Tactics for MAD 3-9
  3313 MAD to Assist A/S Vessel 3-9
  3314 Airship Advised of Sonar Contact 3-9
  3315 Airship Action when A/S Vessel Attacks 3-9
  3316 Instruction When Contact Lost 3-9
  3317 Designation of Target 3-9


United States Fleet Anti-Submarine Instructions

Part III



  1. The commander of the area in which an action occurs shall be in operational control of all forces employed in that action. All forces, air and surface, of other commands made available for this action, shall be placed under the temporary control of that area commander.
    1. The commander in "operational control" shall inform units concerned and the commander of any adjacent area into which the operation may extend, of such of the following items as are applicable:
      1. Summary of information at hand.
      2. Task.
      3. Focal point of action.
      4. Identity of the Officer in Tactical Command.
      5. Initial Area of Operations.
      6. Forces initially present.
      7. Additional forces being dispatched.
      8. Additional forces requested from other fleets or frontiers.
      9. Any special communication channels to be established for local communications. (Ref. USF 70 series.)
      10. Any special communication channel to be established between the Officer in Tactical Command and the officer in "operational control." (Ref. USF 70 series.)

    2. Unless otherwise directed by the officer in operational control the senior surface craft commander at the scene of action shall be in tactical command of the joint action.
    3. For the status of a carrier that may be present see Article 4050.
    4. Whenever joint action is undertaken, or whenever participating aircraft arrive on the scene of joint action then underway, the senior pilot of the aircraft shall inform the carrier of the number of aircraft present on arriving and the length of time such aircraft can remain on the scene. If no carrier is present the aircraft should inform the nearest participating surface craft who shall relay that information to the OTC.



  1. The most effective means of defeating the submarine is the coordinated effort of aircraft and surface craft. The possibility for this joint action will always exist while employed on convoy coverage, task force screening and killer group assignments and may occur during sweeps or searches. It is therefore essential that the personnel concerned understand the limitations and capabilities of the various types of aircraft and surface craft engaged in this phase of war.

  1. Aircraft and surface craft compliment each other in anti-submarine operations. The aircraft can search large areas quickly to locate submarines, attack and drive them down. They carry a limited bomb load, however, and compared to surface craft, have only a limited staying power. Surface craft, in addition to staying power and large depth charge load, have sonar equipment, but they are restricted in speed and visual field.


    1. The accomplishment of satisfactory joint air and surface craft operations requires perfection in teamwork. Coordination of the following is essential:
      1. Air and surface craft will keep point of submergence well marked.
      2. Aircraft will keep surface craft notified of any indications - visible or by sono-buoy - of the submarine's position.
      3. Aircraft will guide surface craft to the scene by use of radio, blinker, surface markers, or zooming the spot. (Float lights have an advantage over slicks in that they can be seen from a greater distance by an approaching vessel.
      4. Aircraft will stand ready to attack the submarine if brought to the surface by surface craft attack.
      5. When practicable, at least two A/S vessels will be dispatched to the scene of contact.

  1. When aircraft and surface craft are working together attempting to establish contact on a submarine, the following plan for coordinating the search shall be used.
    1. In the situation where first contact is made by the aircraft, the aircraft attacks if possible and lays the standard 1500-yard sono-buoy pattern (Article 2717). If sono-buoy contact is not obtained within the first half-hour, or is lost and not regained within one half-hour, Article 2264 applies. If sono-buoy contact is obtained continue monitoring sono-buoys until A/S vessels arrive.
    2. When aircraft and two or more surface craft are on the scene of a submerged contact, or when two or more A/S vessels come within 8 miles in approaching the scene of a submerged contact, the submarine will be considered as primarily a target for the surface craft and sono-buoy location and tracking will be done primarily for the purpose of assisting the surface craft in gaining sonar contact. Under other conditions aircraft will operate according to instruction for employing the weapons carried.
    3. The A/S vessels will close the contact in accordance with the following procedure:
      1. A/S vessels will close at highest speed consistent with Article 1136 (c).
      2. Proceed to the contact in accordance with the latest effective instructions regarding Countermeasures for Acoustic Torpedo.

    4. On arrival, A/S vessels will use search plan in accordance with section 1100. If sono-buoy contact was not gained, Initial Point and time elapsed since loss of contact will be based on the position and time, respectively, of the original contact. If sono-buoy contact was gained, Initial Point will be position of sono-buoy giving the latest submarine indication and time elapsed will be computed from the time of latest submarine indication over this buoy. Any knowledge as to submarine's course and speed gained from sono-buoy indications may be taken into account by orienting the search plan so as to sweep the most probable area first.


    1. The usefulness of sono-buoys in joint operations is restricted because surface ships, especially when towing FXR gear, create so much noise that submarines cannot be heard over sono-buoys in the vicinity of the ships. In order to illustrate this effect the graph below is given.



    1. In order that information on the layout of standard sono-buoys pattern, illustrated in Articles 2717, 2718, and 2719 may be given to relieving air or surface craft with minimum chance of confusion, the following procedure is presented for guidance.
      1. Irrespective of the procedure used to lay out the sono-buoy pattern, the axis of the pattern will be considered the magnetic heading of the aircraft during the approach to drop the center buoy. This will be the magnetic heading on which the directional gyro is set on 000°.
      2. The sono-buoys will be graphically described as Center, Top, Bottom, Left and Right (see Figure 2 below).
      3. Figure 2

      4. In exchanging information on a sono-buoy pattern, the following data will be provided: (1) The axis of the pattern (in degrees magnetic), and (2) the color of the buoys dropped.

  1. Unless a surface craft is in position to ram, a submarine on the surface or submerged with periscope or Schnorchel showing is primarily the aircraft's target. All other submarines are primarily the target of surface ships. A surface craft's echo-ranging task is difficult, and, when the water has been disturbed by depth bomb explosion, it is increasingly so. When a surface craft is within sonar range of a submarine and is indicating by the display of black pennant (USF 10) that she is making a sonar approach,


    aircraft shall not drop depth bombs unless a part of the submarine is visible on the surface or has been submerged less than 15 seconds.

  1. All surface craft commanders shall be familiar with aircraft emergency and forced landing procedure (see Section 5700).

  1. Communications for forces involved in joint air-surface action shall be conducted in accordance with the instructions contained in USF 70 series.
    1. When frequencies and/or call signs are unknown, they should be ascertained by use of appropriate "Q" signals sent visually after recognition signals are exchanged, or by radio, utilizing 3000 kcs. Observance of the following points is essential:
      1. Maintain efficient communication between aircraft and surface craft.
      2. Aircraft be alert to home surface craft to scene of action and vice versa, maintaining sufficient altitude for radar bearings.



  1. Instructions for maneuvering Carrier task groups, including their screens, are set forth in USF 10, Section 3300.

  1. Screening ships with carriers engaged in A/S operations should be stationed primarily in accordance with requirements of sonar screening. Four ships constitute an ample screen for the carrier, normally three are considered adequate. Circumstances may dictate a lesser number.
    1. Vessels of the screen may be employed profitably:
      1. By placing one vessel of the screen near the center of air sweep to provide surface support in a minimum of time.
      2. By placing one vessel of the screen at limit of TBS range on most probable bearing of the enemy.
      3. As a picket or patrol in expected position of the enemy.
      4. As link with or guide for planes conducting extended search.
      5. In running down bearings of HF/DF ground waves.

  1. At night or in reduced visibility when more than three screening vessels are available and when sir operations are not being conducted, the search may be extended by placing one or more screening vessels on the bean of the formation at about double the radar range obtainable on a surfaced submarine.

  1. Once a positive contact is made (either by day or by night), two ships (if they can be spared from the screen) should be concentrated on the contact. The Carrier and remaining ships should keep clear.
    1. The movement of the Carrier should be governed by other operations in prospect and by by the extent that the Carrier can assist with regard to:
      1. Air support.
      2. Further Surface Support.
      3. Need for night radar search for other enemy submarines possibly closing the scene of the attack.
      4. Desirability of confining communications to VH/F voice communications.
      5. Necessity for early rendezvous for further group operations.


    1. If a direction finder bearing of a ground wave of a submarine transmission is obtained, a unit of screening vessels and aircraft (but not the carrier) should, when practicable, be employed to develop it by advancing along the bearing. If the carrier proceeds in the direction of the contact, screening vessels will be stationed sufficiently in advance to permit the carrier to turn away outside of torpedo range should they make contact.
    2. Data with respect to bearings obtained which supplement information disseminated by activity disseminating shall be transmitted to the Commander in Chief, United States Fleet, at the earliest practicable time.

  1. Succession to Command is in accordance with War Instructions (FTP 143).

  1. Carrier Task Group
    1. In the event of inability to land on the deck of the carrier, water landings should be made in the vicinity of the Task Group during daylight, if practicable, unless positive orders to the contrary are received. [See War Instructions (FTP 143) and USF 74.]

  1. Carrier Task Group Search Plans
    1. The following plans will be employed by a Carrier Escort Group when searching for a transmitting submarine whose track is fairly well known and whose position is approximately established by D/F's, sightings or estimates based on recent information. These plans are outlined below to make contact on a transmitting submarine assumed to be running submerged by day and surfaced by night. However, the plan may be varied to operate during any period of the day or night that the submarine is expected to run surfaced.
    2. The following flight plans for carrier based planes are designed to ensure simple navigation and frequent check points on the carrier:
      1. Figure 3 shows the basic flight plan. Two planes take off together and fly duplicate plans on both sides of the carrier. In order to have the planes meet the carrier at the end of the return leg, the distances s and w must be related by the equation:
          w=s(v/V-1) Formula (1)
        where w=distance of flight to beam of carrier.
          s=sweep spacing between beam flights.
          v=ground speed of the planes.
          V=speed of advance of carrier.
      2. The value of s should be chosen to suit the following conditions: (1) probability of contact as high as possible; (2) w not too far from the carrier (not more than 100 miles); (3) circuit time fits in satisfactorily with endurance of plane. A value of s should be selected for the desired probability of contact (use Nomograph 1, Article 2262) and w obtained from formula (1). If w is too long or too short the length may be balanced against the probability of contact until the best compromise is obtained.


    1. When a submarine has been located (by a D/F fix, sighting, etc.) close enough so that the carrier group can reach the estimated position of the submarine during the ensuing night, the carrier group will head on an estimated collision course with the submarine, attempting to intercept the enemy approximately at midnight. The basic flight plan shown in Figure 3 will be used. If no estimate of the course and speed of the submarine is available, the carrier will head for the position of the fix.
    2. When searching for transit U-Boats whose track is fairly well known or for U-Boats known to be contained within a certain area, the following plan is applicable (RPM 2043):
      1. The carrier group will make a series of cross-over sweeps well ahead of the estimated position, and across the estimated track, as shown in Figure 4 and explained in (b) below.
      2. In the track plan of the carrier group (Figure 4 below) the lead angle a is determined by the triangle with side OY equal to the speed of the carrier V and XY equal to the speed of the submarine u. The distance w from the carrier to which the planes fly should be as large as practicable, with s, the distance between successive aircraft tracks determined by w and V in Formula 1, Article 3272. The maximum width of channel or seaway (OO' in Figure 4) which can be effectively patrolled by this plan is given by Formula 2.


        Maximum width   (Formula 2) (RPM 2043)

        Additional, but less intensive coverage is given to a distance w to each side of the end legs O'A and CO. The length M of these legs is chosen to place O' directly across the channel from O and C directly opposite A. The maximum length of M, corresponding to the maximum width of channel OO' (from Formula 2) is equal to 2Vw/(V+u).

        To illustrate by example, suppose it is desired to cover as wide an area as possible. Assume speed of carrier 13 knots, aircraft speed 135 knots, U-Boat speed 5 knots, aircraft sweep 66 miles abeam of carrier, then

        By construction angle a equals 22.6°
        By formula 1 (s) equals 7 miles.

        By formula 2 OO' equals 228 miles (plus less intensively covered sections of 66 miles at each end)
        By formula M equals 95 miles.

        The time to complete one cycle in this case will require about 48 hours. The same lead angle could be used to set up a barrier width approximately 110 miles (plus 66 miles on each end sweep) with a cycle of about 24 hours.

      1. The barrier should be maintained for a time sufficient to assure that the submarine has had ample time to reach and pass beyond the searched area. If contact has not resulted the position of the barrier should be retreated in the direction of the estimated track a distance which will place it once again well forward of the target. The barrier should also be retreated when bad weather, investigation of contacts, etc., interrupts its proper continuous execution.
      2. The probability of obtaining a contact depends primarily on the track spacing s. Since s is always small (5 to 8 miles), the probability of contact with all but the smallest surfaced targets is bound to be high, even if fairly low values of E (effective visibility, Article 2260) apply. The probability given by Nomograph 1 (Article 2262) for such spacings is only a minimal value for the present plan, especially when barriers of less than maximal width are patrolled. This is because the area through which the target must pass in the time required to make one cycle is covered more than once each in cycle. The probability of contact in the extra width covered on the short end legs is one-half of that given by Nomograph 1 for the central area.
      3. A barrier which advances toward the target instead of standing in one place may be set up whenever the distance OO' is less than the maximal value given by Formula 2. The track for the carrier group is set up by following the procedure given in Article 2273, setting S equal to 2w. Instead of returning to O, the starting point, at the end of the return cross-sweep, the upsweep on the end leg is extended beyond O to make M equal on both ends of the barrier. The cycle is repeated from the new starting point. This progressively advances the position of the barrier, while maintaining maximum tightness.



  1. The primary value of the airship in joint operations lies in its effective use of MAD and sono-buoys to prove and develop contacts and to relocate lost contacts, thereby affording considerable assistance to surface craft particularly in areas where poor sound conditions exist. The airship's excellent communication with surface craft, good observation platform, and its maneuverability render it a valuable adjunct to surface craft in operations against submarines.


    1. The provisions of Section 3100 apply in general to airships equipped with sono-buoys.
    2. The MAD tactics to be employed by the airship in joint airship-surface action are described in Article 2940.
    3. If an airship has established MAD contact at a scene of action it will advise the nearest anti-submarine surface craft which will then develop sonar contact centered on the last MAD contact position.
    4. The airship will continue MAD tracking keeping the surface craft advised of the results. When sonar contact has been gained this information should be transmitted to the airship together with the bearing, range, course and speed of the submarine.
    5. The A/S surface craft will advise the airship when its attack approach is commenced and whether or not ahead thrown weapons are to be used.
      1. If ahead thrown weapons are to be used the airship will haul clear of the area this is immediately ahead of the firing vessel and remain clear until completion of the attack, then close the area immediately to regain MAD contact.
      2. If ahead thrown weapons are not to be used the airship will continue to track and mark contacts during the approach of the surface craft, reducing MAD sensitivity momentarily during proximity of the surface craft to avoid false indications.

    6. If both sonar and MAD contacts are lost the surface craft will commence operation "Observant" and the airship will employ MAD trapping tactics and use sono-buoys as necessary.
    7. The provisions of Article 3140 apply to airships.


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