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Thread: Catalina search patterns

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    Default Catalina search patterns

    In the ORBs for the RAF station at Koggala and for 413 Squadron there are references to Catalinas flying the following types of patrols during March and April 1942:

    Crossover
    Square search to a given depth around a given position
    Creeping line ahead on a given bearing
    Search E
    Search W

    I know what a crossover search is but am a bit hazy about the next two and have no idea what a Search E or a Search W might be. Could anyone enlighten me?


    Thanks,

    Rob

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    Square search.

    Start at a particular position and spiral out ie
    1 unit north
    1 unit west
    2 unit south
    2 unit east
    3 unit north

    repeat expanding outwards until seach north covers full defined distance (depth)

    CLA
    Creeping Line Ahead

    start at a particular position
    x units on bearing -90 deg
    1 unit on bearing
    x + x units bearing +90 degrees
    1 unit bearing
    x + x units wbearing -90 degrees

    repeat until end position reached.

    Search E and Search W can be one of two things either:
    Line search (like crossover but not between two landfall locations) from a position eastwards/westwards

    or A defined area Area E and Area W with other areas F G H I J K L M N O P Q between

    Regards
    Ross
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    Hi Rob
    For the Creeping line ahead search imagine the given bearing as a line on a chart and superimpose over it a rectangle along the same bearing with the line as a centre and a width appropriate to the area to be covered. The search commences by flying along the top short side of the rectangle and then turning 90degrees and flying down the long side for an appropriate distance on the given bearing before another 90degree turn back across the rectangle in the opposite direction to the first leg to another right angle turn on the other side to the given bearing and so on until the whole rectangle has been searched. The size of the rectangle,the length of the legs before each turn etc is determined by what you are searching for and also what with,eg eyeball, radar, listening devices etc and of course the weather conditions.If the search was for a single dinghy or a survivor or body in a lifejacket (i.e. something very small)the distances between the runs across the rectangle could be as low as 1/2 mile and the a/c would fly at around 100ft.Turning that tight is very difficult and dangerous for an a/c of any size so the runs across the rectangle would not be done consecutively. You would fly the top of the rectangle as run no.1 down the side and back along say run no. 5 then turn towards the top of the rectangle and then fly run no.2 then no.6 then no.3 and so on and in this way the search area would covered twice over without exceeding the range that a visual searcher could cover. If Radar was used then the distances would expand to allow for the greater range possible and the a/c would be higher to expand the horizon and you would not need to turn back towards the top of the rectangle. It sounds confusing when written but I don't know how to draw on the forum
    Hope it helps
    Regards
    Dick
    Last edited by Dick; 4th April 2011 at 18:50.

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    Ross, Dick:

    Thanks very much for your responses. Your explanations of the square and creeping line ahead searches are very clear, and you've provided at least a lead for learning what E and W searches were.


    Thanks,

    Rob

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    Hi Rob:

    A bit more on Creeping Line Ahead:

    Most convoy escort work was based on Creeping Line Ahead (CLA) or the same astern, depending on where the U-boats were thought to be, although there were other search patterns that could be assigned by the convoy commander as needed. For creeping lines, the aircraft swept a swath of ocean 90 degrees to the convoy’s course for a given distance and time, then turned onto the convoy’s course to ‘creep’ ahead before repeating the pattern over several hours. The lines were more often flown some distance from the convoy with the majority of the ships’ captains unaware of the aircraft’s presence.

    Regards:

    Robert

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    Slightly off topic but was this search pattern 'Creeping Line Ahead' the method used by the D-Day decoy aircraft simulating an invasion fleet heading towards the Pas de Calais coast? I'm possibly way off but have always wondered how aircraft can appear as a fleet of ships moving at 15-25 kts on the radar?

    Norman

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    Hi Norman
    You would need to crosscheck in the literature of the period but I suspect that you are right, although the pattern would most likely be based on the Low level /short range of the visual type in my previous post.Remember they were attempting to simulate the approach of an invasion fleet which would not move forward at a fast speed. The Germans would have expected Radar interference to mask the size of any formation and knew about Window but if the "interference" moved forward too quickly it could give the game away. A 617 Sqn History might have some detail.
    Edit:The description in "Most Secret War" by R V Jones is that Lancasters would fly in rectangular orbits 8mls long by 2mls wide moving the centre point of each orbit in a S Easterly direction at a rate of 8 knots,the convoy speed,and drop Window continuously.There is an extract of the 617 Sqn ORB available online which refers only to a Special Operation during the night of 5/6/44 but indicates that the 2 a/c referred to each carried 3 extra crew mwmbers. A similar operation was carried out by Stirlings
    Regards
    Dick
    Last edited by Dick; 6th April 2011 at 10:08.

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    As Dick said, the intent was to get the German radar to focus on the Window returns, which far outnumbered the returns of the aircraft dropping them. Being dropped at fairly low altitudes, a single bundle of Window would not be airborne very long. The technique was to drop another bundle at a time and distance from a previous bundle that would appear on radar to be intermitant returns from a single source travelling at a low speed. Can't remember the source, but I recall reading that this technique was developed and practiced well before D-Day.

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