Which is true of pyrotechnic visual distress devices?

Answer 1

Visual distress signals can be sent by flashing a light in the SOS pattern; that's 3dots(quick flashes) then 3 dashes (longer flashes) then 3 dots again. One naval instrument for doing this was the Aldis Lamp.

SOS signals can also be sent by semaphore, it being a system of using 2 flags in various positions such as 1 out to the right and 1 to the left (raised 45 degrees above the horizontal), different positions of the two flags together representing letters of the alphabet, or words.

People have laid out pebbles from the beach to spell out large SOS letters.

I expect the American Indians could send and understand the meanings of various smoke signals.

Flares of various colours can be shot into the air to give information. An aircraft pilot coming in to land when it was too dangerous to do so would see a red flare fired into the sky.(possibly because the pilot hadn't seen another plane just taking off)

From the Merchant Shipping (Distress signals and Preventions of collision )Regulations 1996. Annex IV Distress signals.The visual distress indications are:-

• Flashing Morse SOS, by any method
• Rockets or shells showing a red stars singly, at intervals.
• International code flag signal showing 'N' 'C'
• A square flag showing above or below it, a ball, or something resembling a ball.
• Flames on the vessel, from a burning tar or oil barrel.
• A rocket parachute flare or hand held flare showing a red light.
• A smoke signal giving off orange colored smoke.
• Slowly raising and lowering of 'out stretched' arms.
• A large piece of orange canvas showing a black square and a circle on it or other appropriate symbol for recognition from the air.
• A dye marker in the sea.

These signals are recognized Internationally at sea.

3rd Answerer says: You may also fly your country's National Flag upside-down as an internationally-recognized sign of distress.

Answer 2

Pyrotechnic visual distress devices are used to signal distress, usually at sea, or due to an accident in the mountains. Orange smoke flares during daylight, and bright white light flares during darkness.

Answer 3

They're only visible over relatively short distances (line of sight). Radio signals travel much further.