Second World War at Sea:
Advanced Air Search
By Robin Rathbun
March 2021

At about 0530 on 4 June 1942, the crew of a PBY Catalina made perhaps the most important sighting of the Pacific War: the Japanese carrier force enroute to Midway Island. The ensuing battle changed the course of the war. That search plane was in position to find the Japanese due to the success of the American code-breakers – and due to the Americans having a good air search plan and enough aircraft to carry it out.

Unfortunately, flying boats and land-based bombers are not as effective in Second World War at Sea scenarios as they should be. The reason is simple: They’re trying to cover too much area with too few planes.

In the lead-up to the Battle of Midway, open ocean search was conducted by Patrol Squadron 44 (VP-44). The squadron used 21 or 22 PBY Catalinas to cover a 180° arc (200° to 20°) out to 600 miles from the island of Midway. Coverage was generally described as “excellent” out to about 300 miles. This translates in game terms to four steps of aircraft searching out to 16 sea zones, with excellent coverage out to eight sea zones.

A check of the Air Search Table shows that in clear weather, four steps of PBYs have a one-in-three (33.3%) chance of locating a task force eight sea zones away. They have a one-in-six chance of locating a task force at maximum range (16 sea zones). Of course, air searches in Second World War at Sea cover the full 360° of the compass, not 180° as used in the Midway search plans.

By concentrating on one-half of the compass, the PBYs left half of the area around Midway unsearched. More importantly, they effectively doubled the number of search planes covering the area where the Japanese fleet was most likely to be found. In game terms, this translates to eight steps of search aircraft over the search area. This gives them a two-in-three (66.7%) chance of finding a task force within eight sea zones, and a 50% chance of locating a task force out to their maximum range. That fits the description of “excellent” coverage out to 300 miles.

On days when fewer search aircraft were available, the Midway search area was reduced even further by sending the aircraft out over a smaller arc. For example, on May 28, twelve aircraft (two steps) covered an arc of 120° out to 600 miles.

In many Second World War at Sea scenarios, players must make do with even fewer search aircraft than the U.S. had on their off days at Midway. In Coral Sea Operational Scenario 1 for example, the Allies have three steps of PBY search aircraft (about 18 planes). Unfortunately, they begin at three widely separated bases and cannot easily combine their efforts.

The combination of long ranges and low numbers of aircraft usually mean that the chance of locating an enemy task force is slim or nonexistent using the rules as written. Two steps of PBYs searching for an enemy task force eight zones away in clear weather must roll a six to spot the force. If the weather is cloudy or the task force is nine zones away, the PBYs can’t find it at all.

The solution to this problem is simple – follow the historical examples and narrow the search area. Search aircraft will provide better coverage at long range by concentrating their search aircraft in smaller sectors. The following Optional Rules give long-range search aircraft their due, at the cost of some extra bookkeeping and pre-scenario planning:

Long Range Search Aircraft
Long Range Search Aircraft are any non-fighter Land-based or Seaplane aircraft with a range of 14/1 (SM79) or better.

Search Plans
At the beginning of a scenario, each player writes a search plan for all aircraft to be used in long-range air search. Ideally, this should be done without looking at the initial starting zones of the enemy task forces. Write the plan to cover the length of the scenario from beginning to end. Search plans contain the following information: Day (turns), starting location, number of aircraft steps, search range, search sector size and search sector direction.

A Search Plan form may be downloaded here.

Day
Enter the day and/or turn numbers during which the search will be conducted.

Starting Location
Name of the land base or seaplane tender, or land/sea zone number where the search begins.

Steps
Number of steps involved in the search.

Range
Maximum number of sea zones from the starting point. Remember that search range is half the aircraft range, to account for the return flight.

Sector Size
Available sector sizes are 360°, 180°, 90° and 45°. Searches over the full 360° use the Air Search Table as written. In a 180° sector search, each step of search aircraft counts as two steps. In a 90° sector, each step counts as four steps. Each step counts as eight steps in a 45° sector.

Sector Direction
For 180° and 90° sectors, the direction is noted by compass direction. There are eight available directions: N, NE, E, SE, S, SW, W, and NW.

Examples of sector directions are available here and here.

For the 45° sectors, use the downloadable sector arc available here.

The sector direction is noted by the sea zone touched by the “sector direction” mark on the arc. When searching a sea zone only partially covered by the 45° arc, the number of search steps is halved. For example, when one step of search aircraft searches a sea zone partly covered by the 45° sector arc, that step counts as four steps instead of the usual eight.

An example may be downloaded here.

Changing Search Plans
When an enemy fleet is sighted by any friendly unit other than a submarine, the search plan for the following day(s) may be changed. Write a new search plan for the period beginning the following day, and lasting until the end of the scenario. If a search sector is changed or added, the new sector must include the sea zone containing the spotted enemy fleet.

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