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Thread: RAF Coastal Command ORB - decypher help needed

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    Default RAF Coastal Command ORB - decypher help needed

    Hi all,

    I would like to ask for help with explanation of phrases I have found to be used very often in several Coastal Command ORBs in erly months of 1945:

    1. "on patrol using 5 NM vis. Area covered 2 times"
    I suppose the patrol track has been folwn twice but what about the first phrase? It evokes me "visbility" but as nearly always there is value 5 NM (what I expect means nautical miles), sometimes as "using 5 miles visibility" I came to the conclusion it was 5 NM range used on the radar during the patrol. Am I right or totally wrong?

    2. "Efficiency 90%. Radar has been used continuously"
    The second expression is clear, but what means the first one? The value varies from abotu 75 to 95%. Some kind of radar efficiency? How it was established?

    Any help wich explanations would be much appreciated.

    TIA

    Pavel
    Czechoslovak Airmen in the RAF 1940-1945
    http://cz-raf.webnode.cz

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    5 NM vis would be 5NM visibility for visual searching by the crew (Mk1 eyball).

    Early Radar would have been quite temperamental and difficult to maintain in good 'Tune',so I guess perhaps the 75%- 90% efficiency could either be that particular Radar set estimated range as against a known 'good' set or perhaps the percentage of time when the Radar set was actually working properly.

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    My understanding of your second quote, the percentage "efficiency" would be that the crew was satisfied that 90% of their allotted search area had been covered, either by the "Mark I eyeball" of various crew members, as well as being supplemented as well as backed up by the available radar equipment carried. Somewhat similar statements were used in RNZAF Hudson patrol reports in 1943 throughout the Solomon Islands, using the old-fashioned (but reasonably reliable by that time) ASV MK. II sets, when every patrol had to estimate the actual coverage (by percentage) of the theoretical search area they had cleared. Low cloud and poor visibility were common over the sea so radar served as a very useful adjunct to the many eyeballs available, and anything important (and suspicious) which showed up on radar would be thoroughly investigated to the best of the ability of the crew. I imagine that the radar carried by RAF Fortresses in 1945 might well have been a generation ahead of the early "ASV MK. II", but the latter type was, I think, still in fairly widespread service till end of the war in most Allied air forces.
    David D

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    Thanks chaps, I will try to make my conclusion from your answers.

    Pavel
    Czechoslovak Airmen in the RAF 1940-1945
    http://cz-raf.webnode.cz

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    Pavel,
    A horizontal visibility of 5nm in daylight means that the Mk 1 Eyeball is only covering a very small area. A Slant Visibility (from the a/c height) of 5nm usually means that the horizontal vis is much less!
    You don’t, normally, do visual searches at night in anything other than very good vis. You won’t see anything in/on the sea/land surface that is not cultural lighting. At sea, you would be looking for distress rockets/flares. A vis of less than 5nm and you would be wasting your time! But the Siggies, in the back, could conjure a tiny ‘blip’ on their radar screen(s) and vector you to the area where a Vis Search (even in the dark!) might be of value!
    HTH
    Peter Davies
    Meteorology is a science; good meteorology is an art!
    We might not know - but we might know who does!

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    Peter, many thanks for pointing out that not all patrols were during daytime! But I still thing it has to do something with the radar range etc. thanks to the word "using".

    Pavel
    Czechoslovak Airmen in the RAF 1940-1945
    http://cz-raf.webnode.cz

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    It could be to do with radar range, language useage alters with time but 'visibility' would be an odd way of saying 'range',do you know which mark of ASV was being used during these flights ? the later marks had much improved performance especially against U Boats.

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    Hi bvs/all,

    1. I fully agree with last post from bvs, I have searched more deeply 210 Sq ORB as an example having Catalina IVAs but I do not know which exact type of radar they had. Earlier records from 1944 shows another records "using x miles visibility", when X is again quite often 5, but also other values like 6; 4,5; 7,5; 7; 10 what confused me a little bit as I do not expect the radar would have so many ranges.

    2. I have searched this unit ORB more into the past and I have found more interesting examples. It seems to me that a lot of factors were considered when the efficiency was counted - weather, aircraft serviceability(?) and it can be also 100 % even if radar was not used!
    "Efficiency first time round the area 90 % deterioating for the rest of the patrol to 10 %"
    "Efficiency 80 %. Vis. poor in places. Radar U/S" - patrol from 20.51 till 14.52 i.e. during night without radar but efficiency still quite high...
    "Efficiency 65 % owing George U/S"
    "Efficiency 100 %. Radar serviceable but not used." patrol from 10.50 till 05.20
    So it seems to me like percentage how they were able to cover the prescrpted patrol area?

    Any additional ideas based on the new records from the ORB?

    TIA

    Pavel
    Czechoslovak Airmen in the RAF 1940-1945
    http://cz-raf.webnode.cz

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