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Thread: Distress Calls from stricken aircraft - R/T procedure?

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    Default Distress Calls from stricken aircraft - R/T procedure?

    What kind of distress calls would an aircraft crew make if they believed their aircraft is going down, either over sea or on land? If the aircraft was in control for a sufficient time to allow the crew to bale out, or to do an ordered ditching, would the Radio Operator have any standard phrases he would use to indicate their going down? Do they ever use "May Day! May Day!" type of emergency calls when hit or going down?


    I am sure there will be different answers depending on type, unit, area of operations. Appreciate all inputs on these

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    Hi Jagan, Lots of info available from different sources for BC ditching and bale out procedures. Can't begin to pull it together tonight, but will do so over the next few days. If you can narrow down to more specific questions it might save time?

    Richard

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    Richard, more specifically about the R/T calls. What would have been the format/verbage

    1. Would there be a pre-decided frequency on which they would broadcast?
    2. any specified message format called out over the R/T? eg: "Aircraft <CallSign> , going down Position RUXXXXXX . <Cause>"?

    When reports suggest that aircraft went down without any distress calls, what were they expecting to hear ?

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    I have had some correspondence from a 78 Sqn veteran about this subject but don't have it to hand at the moment. From memory transmissions were made in morse code on a given frequency, normally the HF/DF frequency and using Q codes to give details. Q codes were established in 1912 under an international agreement, they are 3 letter codes all starting wth Q that have a given meaning e.g. QRK - "the readability of your signal is". I think for ditching the code was QUG which means I am landing at current position. In some cases the morse key would be clamped down so it transmitted a constant tone which could be triangulated by means of direction finding. To ask a question, I.e. What is the readability of my signal, the letters INT would be transmitted before the Q code, so INT QRK; the INT was transmitted 'barred' in that all letters are joined together where as each letter of the code would have a space in between. The transmission may have been something like this:

    CQ DE NOSMO 11 QUG AR

    CQ stands for all stations listening on that frequency
    DE stands for this is
    NOSMO 11 the call sign allocated to a given aircraft (NOSMO being specific to a Sqn) and 11 being the aircraft
    QUG means I am forced to land at current position
    AR means end of transmission

    There may have been other transmissions before a ditching e.g. Requesting a position INT QDR - what is my magnetic position from you?

    Depending on the urgency it may have just been a straight forward SOS signal. Survival radios for use In the life raft transmitted the SOS in morse followed by 12 Dashes then a gap and then repeated. The dashes gave the DF operator something to home in on. These were I think transmitted at 500khz.

    Will try and do out the correspondence when I get home tomorrow.
    Last edited by 78SqnHistory; 10th September 2016 at 12:08.

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    Hello All,
    Post #4 deals, mainly, with W/T procedures, whereas Jagan’s original request was for info on R/T procedures (and – one assumes – R/T procedures in WW2? (or thereabouts)).
    Don’t know when the internationally used/agreed aviation Emergency Frequency of 121.5 megs (and – latterly – 403 megs) came into force. Several sites indicate its initiation was by agencies that did not come into existence until after WW2.
    The use of “Mayday, Mayday, Mayday” (French m/aidez) seems to have originated around 1927 on the London-Paris civil routes when the air/ground comms would – most likely – have been in the H/F range.
    When the lesser emergency states (“Pan, Pan, Pan”, or “Securite, Securite, Securite”) came into being I know not.
    Any transmission on 121.5 and/or 403 megs would have initiated auto-triangulation in the UK. And, latterly, when H/F SSB became the norm (before satellites) for long-range air/ground comms ditto for oceanic emergencies. (There is BTW a move to phase out 121.5 in the near future).
    I suspect that the WW2 RAF airborne emergency comms may have been connected to the DARKY (or DARKIE?) system, which was a form of manual triangulation. I do not know what frequencies it used – but somebody will!!
    And, similarly, there would – almost certainly – have been Rules&Regs for its operation and use. These may have been from Air Min level, I would have thought, rather than Command and/or Group!
    Best I can do!
    Peter Davies
    PS The Morse interrogative was, I was taught, to use the ‘Q’ code followed by ‘IMI’ ‘QSD IMI’ = ‘Is my keying defective?’ (which, in my case, it nearly always was/is!!!)
    Meteorology is a science; good meteorology is an art!
    We might not know - but we might know who does!

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    Thank you for the answers - i am a bit more informed now but still awaiting a definitive answer.

    Post #4 is quite informative and i am left with the question - why use W/T Morse when the Radio Telephony was already in use. I can imagine W/T for coded cypher messages. why would ac still use W/T Morse in an era of radio communications? Is Range a reason?

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    Jagan,
    W/T comms required the use of a WOP - a long, and somewhat cumbersome procedure (particularly if one is cyphering/de-cyphering!!). R/T procedures (whether in the very early days by H/F, or latterly, VHF/UHF) simply require the Pilot to press a transmit button to initiate a 'panic/distress' call, and/or subsequently to reply to any answer(s).
    W/T could be used over long distances (ionospheric conditions permitting!).
    VHF R/T was - essentially - 'line-of-site' from transmitter to/from receiver (with a few rare exceptions!).
    I await the words of the experts!!!!!
    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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    Hi,

    R/T was commonly said to have a workable range of 8-12 miles so voice transmission generally limited to airfield control and the Darky channel (6440 kc/s). R/T operated on H/F, but is different to the H/F morse comms (long range, up to 500 miles for two-way traffic).

    A 1 Group Signals Instruction for Operational Flights states that the W/Op (May '42) was responsible for ensuring the following were carried on a/c:

    F398 log book
    AP982 Aircraft Operating Signals
    SD0182/H1 - A/c and ground D/F Verification Signals
    Schedule of operations for British M/F Beacons for the duration of the flight
    Op c/s for the particular operation, a/c letter and the M/F D/F section specifically allocated to the a/c for the flight
    Standard destructible paper [flimsy] giving -
    c/s and freqs for H/F D/F Stations in BC and other relevant Stations, esp the Diversion Schedule for the flight.
    c/s for Group HQ, collective c/s for all group a/c in flight and Group Operational Freq
    c/s and freqs (both D/F and Guard) of Flying Control Centres
    diversion numbers set out in Diversion Schedule for the flight
    c/s and freqs of the various M/F D/F Sections, incl their constituent stations [each section = 2 or 3 stations]
    The Station a/c c/s
    c/s and freqs of selected continental wireless stations

    A/c maintain W/T and R/T silence where possible. Station H/F D/F transmit c/s for 3 mins at 15 minute intervals commencing at the clock hour (unless working an a/c)

    Group broadcasts are on the hour and half hour, on Group Medium Power tx on Group Operational freq, repeated for 3 mins.

    No 1 Group was allotted M/F D/F Section F (Sealand (Control), Andover, Leuchars), so W/Ops would normally address distress calls, requests for assistance and ident signals to this Section. They could use any other available Section as reqd.

    Emergency Reports were to use a code when it was doubtful that the a/c would reach GB:
    FTR - damaged by en fighter
    FLK - damaged by en flak
    BAL: - damaged by en balloon
    ICE - icing
    ENG - engine failure
    PET - fuel shortage
    LLL - lost

    Such messages were to be addressed to Group and passed if poss on the Group Operational freq, but could be sent on any medium D/F freq or Station D/F freq if reqd. The message was to be given emergency priority and added to the SOS signal if a/c needed to send one.

    Until Jan 1944, IFF would also be switched on when 100 miles from GB coast on return flight (or crossing en coast out if nearer than 100 miles to GB). Band 1 (narrow) was the normal setting, a/c in distress were to set Band 3 (very wide) instead.

    A/c who were below 2,000' or who suspected IFF was not working were to send an i/d signal. A/c requiring a D/F fix or bearing were to use the same format of signal:
    c/s of D/F section - 'V' - c/s of a/c
    No of a/c in formation if more than one
    [if needing fix or bearing] operating signal requesting fix or bearing
    A long dash of 15 seconds
    c/s of a/c made once only
    [NB the above was in morse, and coded if time permitted using Syko machine]

    Control Station would reply with an 'R' if a/c transmission was for I/d only, or would transmit bearing to a/c if requested or, if a fix reqd, transmit 'R' then, after a short pause, transmit the posn of the a/c.

    If in distress (eg decision made to ditch), then the distress call would be made, if possible, to allotted M/F D/F Section - Section F for 1 Group. Ditching information passed by the W/Op was in the form of a CHAPT report - course, height, airspeed, position, time. He would also add the estimated ditching position and pass bearings or fixes received to the Nav. When ordered to ditching stations, the W/Op would clamp the morse key to leave the set on permanent send.

    If the a/c made it to the GB coast, then emergency procedures included voice calls on the Darky channel and/or use of nav lights and very flares.

    NB - by winter 43/44, the Berlin campaign, 1 Group was using Sect G (Bircham Newton no1 (Control), Lympne No 2 and Newcastle No2). ASR a/c used Section J.

    Hope this helps,

    Richard
    Last edited by Richard; 10th September 2016 at 17:20.

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    Interesting Richard, looks like you've also been reading the No.1 Group Appendices.

    I can only speak for 1940, although I do have the 1944 RAF Flying Control Air Publication re Aircraft in Distress and Flying Control info from 1939/1940 files, regarding:-
    Distress;
    Urgent Assistance; and
    Safety and Navigation of aircraft and crew in need of assistance.
    These levels of Distress and Assistance are also listed in my pre WW2 Q code.

    Generally, in 1940 each Bomber Station was responsible for its aircraft using H.F., wireless, most transmissions away from the Station were mainly Morse w/t transmissions.

    However, when nearing the British coast the Fighter Command M.L.S. (Movement Liaison Section / Movement Liaison Officers) through a series of Medium Frequency M.F. D/F Sections:- Section A ; Section B etc., were responsible for the identification of aircraft, S.O.S. from any aircraft and providing direction finding (D/F) fixes of aircraft, by using two or more stations in their particular Section, that the aircraft had been instructed to work before the Operation.

    At least half an hour before each Bomber Flight took off, the MLS at Fighter Command would be sent the information of each Bomber, including its Call Sign and its Movement Serial Indicator (M.S.I.).

    Fighter Command and Fighter Command M.L.S., were criticised by Bomber Command for not identifying aircraft approaching the British coast, as Bomber Command stated Fighter Command M.L.S. are sent all this information in advance and still can't identify some of our aircraft.

    If the Group diversion signal had been sent out, the aircraft would likely be on the Group Guard Frequency, once the Identification Signal was sent to the M.L.S., via the Section Wireless Stations.

    When sending an S.O.S., over the Sea around the British coast, you would give your Aircraft call-sign, your Movement Serial Indicator and number of Souls on board the aircraft, if you were working a Section on M.F. D/F.

    If you were working a wireless station and then needed to send Distress, you might also transmit an S.O.S. with a Q.D.M., giving the Wireless Station you are working the direction to reach the aircraft, in degrees from magnetic North.

    If you were going down and felt you had made the last transmission, you would lock the key down, giving a permanent transmit in the hope that the Station, or Section, or some wireless Station might get a fix.

    1. Therefore, an S.O.S., might be received on H.F. wireless, if more than about 300 miles from coast, probably by your own Bomber Station.

    2. If over the Sea around the British Coasts, an S.O.S., would most likely be sent on M.F. D/F and usually received by the Section you were allotted. A Wireless Section, usually consisted of 3 Direction Finding (D/F) wireless Stations, including the Controlling Section Station.

    3. General Post Office (G.P.O.) Wireless Stations would also be involved with receiving S.O.S. transmissions and had lines to the M.L.S., and could make Distress Broadcasts to Shipping ... look out for aircraft at ...

    EDIT: I also have a 1940 list of Distress Area HQs in the British Isles, who should also contact M.L.S., Fighter Command, assist aircraft in Distress and instruct G.P.O., Coastal Wireless to make Distress Broadcasts in the event of hearing of Distress calls and passing info to Naval Authorities.

    4. If diverted by your Group Operations, the RAF Regional Flying Control Station, to which you were being diverted would be on D/F Watch and when within V.H.F. range, change to R.T.

    5. When Darky came in, they would probably be involved to, if the aircraft was making use of darky, which was R.T.

    6. The British Observer Corps, Coastal Wireless, Naval Areas and Coast Guard would be watching for Red Distress Flares over the sea and passing them to Fighter Command, for the M.L.S., and plotting these using the Fighter grid co-ordinates (letter and four numbers).

    I have discovered that even in 1940 the Winchester Observer Group (receiving plots, coloured lights, recognition lamp signals and flares from the Observer Posts in their Observer Group) as well as passing this to Fighter Command, also had unofficial telephone liaison with their nearest RAF Regional Flying Control at RAF Boscombe Down.

    The Distress flares overland, were White Distress Flares, but I can see from A.A. Battery and other Records, some aircraft fired a series of Red Flares, over land.

    In 1940 and in bad or cloudy weather, the whole M.F. D/F system became overloaded, so new Sections were added.
    Last edited by Mark Hood; 11th September 2016 at 23:50.

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    Hi Mark, yes, spent many happy hours with the 1 Group ORB and appendices.

    Just to add on the specific question about use of the word 'Mayday'. The Feb 1944 Bomber Command landing scheme confirms emergency R/T procedures as follows:

    5. Aircraft requiring emergency landings are to:-

    (i) Call Control by R/T in the normal way, prefacing the message with the word 'Mayday' and giving a brief explanation. Aircraft will be given 'Prepare to land' and all airfield lighting will be switched on.
    (ii) If aircraft are unable to contact Control on R/T they are to fly up the runway at 1000' or below cloud with all navigation, upward and downward identification lights on and flash the aircraft letter on all lights and fire a series of red Verey lights.

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