SARAH [Main Title]

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  • Title: SARAH [Main Title]
  • Film Number: AMY 549
  • Other titles:
  • Summary: SARAH is a portable self contained radio beacon transmitting a signal that enables its geographical location to be identified by search and rescue teams, and thus that of the survivor. It is incorporated in the life jackets of all aircrew and is activated automatically after they have exited the aircraft. A two way speech facility with the search and rescue teams is provided. The film shows how a typical search and rescue exercise is conducted.
  • Description: A radio announcer reports an aircraft has been lost between Gibraltar and Cairo, and search operations are in progress. Many aircraft are lost each year in similar circumstances but most crew escape unharmed. In the vicinity of the United Kingdom crew can expect to be found soon, but elsewhere in the world, including the sea, there are thousands of square miles to search. If at sea in a fully equipped dinghy crew can survive for several days and their chances of rescue much improved, but a single pilot who cannot get into his dinghy depends upon his life jacket to keep him afloat. The problems associated with locating a survivor in the sea are addressed: Flying at 500 ft you can just about see a man in the water at 750 ft providing the sea is not too rough, visibility is good and it is daylight. Film cuts to a map with a plot of the lost aircraft’s track, and it will be necessary to search an area of some 30,000 square miles. Since it is only possible to visually scan a track 1500 ft wide and a quarter of a mile apart in ideal conditions, a search plan based on these legs and flying at 200 mph would take two aircraft 600 hours. To search this area in a reasonable time 300 aircraft would take four hours, and even then glare or momentary distraction may leave the survivor unnoticed. To overcome these visual disadvantages some form of small radio wave transmitter is required. Film cuts to a Shackleton aircraft flying above thick cloud, with the crew wearing their life jackets which incorporates the new equipment that has been introduced. Camera closes up to the equipment comprising a radio transmitter, an aerial stowed under a cap and a battery pack of capable of 20 hours continuous operation. On removal of the cap the transmitter is switched on and the aerial erects itself. The equipment requires no further action by the survivor as the system is fully automatic. This equipment is known as SARAH, Search and Rescue at Home. The film shows crew being introduced to the SARAH beacon and how it is deployed. The range of the beacon increases with altitude and at 10,000 ft the signal covers an area of some 10,000 square miles, requiring 16 watts of power from the battery. An ordinary battery would last only for about six minutes, and by arranging for a transmission duration of 1/10 of each second the power available lasts for one hour. However, the intermittent nature of the signal makes it unsuitable for normal receiving equipment, so a 1/200 pulse is split up evenly into shorter pulses of 200 pulses per second, giving a signal duration of 20 hours with a constant characteristic. A survivor is seen in the water with his SARAH equipment transmitting to the under wing antennae of the search aircraft which feed into a special receiver monitored by the radio operator. The monitor is a modified cathode ray tube displaying the track of the aircraft as a vertical line superimposed with a horizontally elongated blip that represents the signal received from the SARAH beacon. The track towards SARAH is indicated by the blip: straight ahead and the blip is centralised on the vertical line, blip movement to the left or right indicates SARAH is to the port or starboard respectively. The signal transmitted by SARAH is of low strength immediately above the beacon taking the form of an inverted cone. By locating this area of low signal strength the aircraft can accurately home onto the beacon by descending from 10,000 ft to 500 ft, the display now shows three vertical lines and three blips, the central line blip is the smallest when the aircraft is flying directly to the beacon. Returning to the initial search plan let us see how this is affected by SARAH. At 10,000 ft flying along lanes 100 miles apart the whole area can be scanned by one aircraft in four hours, at night and in all weathers. The film cuts to Royal Air Force launch 2594 fitted with the SARAH equipment. At sea level the range of the beacon is five to six miles but working in conjunction with aircraft (cut to Shackleton) having ten or more times this range launches can complete a search to within a few feet of the survivor without ever seeing him. The launch is manoeuvred towards the beacon but because it has difficulty in rough seas and poor weather to respond to small signal changes, it is necessary to provide a method of locating the survivor unrelated to the launches heading. A rotating aerial provides this service right up to pickup. Film cuts to external rotating aerial and control dial on the bridge that indicates the direction in which the aerial is pointing and hence the bearing of the survivor. “A typical search operation”: Film shows pilot without a dinghy in the sea with SARAH deployed. His aircraft is reported missing and a search initiated. The crew board an Coastal Command Shackleton and take off, while the crew of a Royal Air Force rescue launch get under way and head towards the approximate position of the survivor using fixed aerials. The Shackleton flies along the course of the missing aircraft and is normally the first to locate the survivor. The radio operator monitors the SARAH blip on the cathode ray tube and guides the pilot towards the survivor, the Shackleton descends to 500 ft to fix the final position, which is transmitted to the launch ten miles away. The launch changes course and soon receives the SARAH signal and starts to rotate the aerial for a precise location. The Shackleton crew drops a Very light (flare) as they pass over the beacon, but the launch already knows where the survivor is. Where aircraft ditch close to land a helicopter may be used to search the area as an alternative to aircraft and launch. Film cuts to Whirlwind helicopter that has already picked up the SARAH signal using the same equipment as in the Shackleton. The helicopter can search, home and save in one operation – clip of survivor being winched out of the sea. SARAH is not restricted to sea borne operations, it can also be used on land. A pilot has ejected and parachuted into enemy territory, initiated his personal SARAH beacon and a helicopter search is under way. The helicopter locates the beacon but the area is under gun fire, the pilot waves to the helicopter who overflies him. Voice communication is vital in these sort of situations and to meet this need a speech unit is incorporated in the SARAH beacon. The helicopter tells the pilot to locate another tactically suitable area and advise him when he has done so. A scrub free area is found, messages exchanged, the helicopter lands and picks up the pilot and rapidly departs. A code module attached to the SARAH transmitter enables several portable SARAH beacons to be represented on the cathode ray tube and thus no survivors are left behind. The yellow dinghies fitted to all aircraft are also equipped with SARAH beacons. The beacons are tested at very high and low temperatures, sealed against water and may be used on submarine equipment: film clip of mariner surfacing and deploying SARAH. The only limitations to search are the search craft themselves. The words “End” appear on the screen but a promotional film for Ultra Electronics commences. SARAH initially comprised two units but these have been replaced by sub miniature equipment with several operational improvements, many of which have been seen in the main film. An instructor demonstrates to air crew how to correctly fit a SARAH equipped life jacket. Finally a small yellow SARAH for use by amateur sailors is shown.
  • Alternative Title:
  • Colour: B&W
  • Digitised:
  • Object_Number: AMY 549
  • Sound: Sound
  • Access Conditions:
  • Featured Period: 1946-1975
  • Production Date: 1955
  • Production Country: GB
  • Production Details:
  • Personalities, Units and Organisations:
  • Keywords:
  • Physical Characteristics: Colour format: B&W Sound format: Sound
  • Technical Details: Format: 16mm Number of items/reels/tapes: 1 Length: 797ft
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  • Link to IWM Collections page:

    AMY 549

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