Flashing and quick lights
1The lesson in plain words
Flashing lights range from slow single flashes to an ultra quick flicker. Count the flashes in each group and judge the speed: both are part of the name.
Flashing
A flashing light (Fl) shows single flashes repeated fewer than 50 times a minute, with each dark spell at least three times as long as the flash. Fl 5s is one flash every 5 seconds. A long-flashing light (LFl) shows a flash of at least 2 seconds. White LFl 10s, one long flash every 10 seconds, marks a safe water mark.
Groups
A group-flashing light shows a set number of flashes, then a longer dark gap. Fl(2) 5s is two flashes, then a pause, the whole sequence repeating every 5 seconds. White Fl(2), every 5 or 10 seconds, marks an isolated danger. In a composite group such as Fl(2+1), two flashes, a pause and one flash come before the long gap. In red or green, it marks a preferred channel.
Quick, very quick, ultra quick
Faster rhythms are named by rate. A quick light (Q) flashes 50 to 79 times a minute, usually 60. Very quick (VQ) is 80 to 159, usually 120. Ultra quick (UQ) is 160 to 300, usually 240, and looks like a flicker. Some countries use 50 for Q and 100 for VQ.
Quick groups
Quick and very quick lights also come in groups, and cardinal marks use them: Q(3) 10s or VQ(3) 5s for east, Q(6)+LFl 15s or VQ(6)+LFl 10s for south, Q(9) 15s or VQ(9) 10s for west, and continuous Q or VQ for north. Think of a clock face: 3, 6 and 9. Full rules: /iala/iala-cardinal.
Counting well
Judge the speed first: about one flash a second is quick, about two a second is very quick. Then count each group aloud and time the period at least twice. On a south cardinal, the long flash after the six quick ones marks the end of the group, so six is not mistaken for three or nine.
2Key data
- Fl
- Fewer than 50 flashes a minute; dark ≥ 3 × flash
- LFl
- Flash of at least 2 s
- Q
- 50–79 a minute, usually 60 (some countries 50)
- VQ
- 80–159 a minute, usually 120 (some countries 100)
- UQ
- 160–300 a minute, usually 240
- Fl(2+1)
- Composite group; red or green = preferred channel
3Key points
- 1
Fl is fewer than 50 flashes a minute; LFl shows a flash of at least 2 s.
- 2
Q is usually 60 flashes a minute, VQ 120, UQ 240.
- 3
Group lights repeat a set number of flashes: Fl(2), Q(3), VQ(9).
- 4
Cardinals: continuous Q or VQ north; groups of 3 east, 6 + a long flash south, 9 west.
4Frequent mistakes
Wrong: Q(3) and VQ(3) are different marks.
Right: Both mark an east cardinal. The speed and period differ, but the group of three is what counts.
Wrong: A long flash is any flash longer than the others.
Right: A long flash lasts at least 2 seconds.
Wrong: Fl(2+1) means three flashes in one even group.
Right: It is a composite group: two flashes, a pause, then one flash, before the longer dark gap.
5Practice case & exam keys
You start watching a white light halfway through its sequence. You count three quick flashes before a long dark gap. A crew member calls it an east cardinal. Is that enough?
Show the answer
No. You may have joined a longer group partway through. Watch at least two complete groups, count every flash, look for a long flash, and time the period. Match the complete character to the chart before identifying the mark.
Exam keys
- Q ≈ 60 a minute, VQ ≈ 120, UQ ≈ 240.
- LFl: at least 2 s; white LFl 10s = safe water.
- White Fl(2) = isolated danger; red or green Fl(2+1) = preferred channel.
- Cardinals: Q or VQ; groups of 3 east, 6 + LFl south, 9 west.
Finish this unit
When you've read it, match the terms, then answer three questions. Get them all right to finish the unit; opening the page alone doesn't count.
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