Many people are attributing the A2 CofC 1:1 rule to the Specific category and though it is a great way to work in a risk adverse way, the spirit of the rule is for the Open Category were the CAA has no oversight on Operations.
The A2 CofC 1:1 rule was devised as a simple principle (as opposed to an exact rule in law) which can be used to quickly work out what separation from uninvolved persons is safe enough in the short term.
It is based on the relationship between the unmanned aircraft’s height and its distance from the uninvolved person (the 1:1 line).
Cap 722 has defined two use areas for it specified below though we would recommend integrating it into your risk mitigation procedures.
• A2 subcategory – (for C2 aircraft only)
When operating in ‘low-speed’ mode within 30m of uninvolved persons, remote pilots should aim to maintain a horizontal separation distance that is greater than, or equal to, the aircraft’s height, using the same units of measurement. (i.e. if the aircraft is at 10m height, it should be kept at least 10m horizontally away from uninvolved people.
Operations where the aircraft’s height is greater than the separation distance (i.e. above the 1:1 line) should be avoided or kept to the absolute minimum time necessary, due to the increased risk.
• A3 subcategory
The 1:1 rule is a short-term separation measure aimed at dealing with unexpected issues, such as a person that is approaching or has entered the area of flight.
If/when the UA is below the 1:1 line, then the remote pilot can continue to monitor the situation until the person has vacated the operating area. Note: the separation from any uninvolved person must not be reduced below 50m horizontally at any time.
A good example to put this into context is imagine you are operating 10m linear distance from an random dog walker, if you drone was 10m in height or under and a motor failed it is more likely not to hit the dog walker as it falls out of air.
Now imagine if it was at 100m in height and the motor failed, would it move onto a direct collision track to hit the dog walker during the extra 90m descent?? Think winds, trajectory etc. Who knows, but the CAA believe it is more likely during the later situation and therefore the 1:1 is born.
A2 subcategory – (for C2 aircraft only)
With a C2 drone in slow speed mode X may not be more than 5m.
With a C2 drone in slow speed mode, X may not be more than 25m.
If the UA is above the 1:1 line (i.e. X is above 75m), then it must be moved further away quickly, or its height reduced below 75m (until below the 1:1 line).
Note: the separation from any uninvolved person must not be reduced below 50m horizontally at any time.
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