From time to time, we encounter hazards in flight that we need to divert around. A hazard could be anything from the weather to multiple police aircraft operating in a specific area at short notice!
We need to have a reliable technique for diverting around a hazard – trying to “just turn around it a little bit” is a great way to get yourself lost! This is where the Hazard Avoidance Turn comes in.
The simplest way to divert around a hazard is by making 60° turns.
With 60° turns, you will fly a triangle that has three equal sides. This means that when you turn back onto your original track, the distance you have flown on your diversion will be twice the distance of the original planned route.
In other words, if you make 60° turns to divert around a 1nm section of your planned route, you will have flown 2nm.
If you diverted around a 2nm section of the planned route, you will have flown 4nm instead.
Since we have flown extra distance on the diversion, our original ETA at the destination will need to be revised.
The time taken to fly a 60° diversion is twice the time of the original planned route section that you diverted around.
So if we fly away from the planned track for 2 minutes and back towards the planned track for 2 minutes, it will have taken 4 minutes to divert around a 2 minute section of the original planned track.
After this diversion, we need to add 2 minutes to our original ETA.
Any distance flown parallel to the planned track in between the two turns can be disregarded in terms of extra time taken to reach the destination.
This is because the parallel section takes the same amount of time as flying the same section of the planned track.
You may assume nil wind for this question.
While enroute to your destination, you encounter adverse weather that you want to divert around. You turn 60° to starboard for 3 minutes before turning to fly parallel to your original planned track for a further 3 minutes. You then turn 60° to port for 3 minutes before establishing back on your original planned track. What change to your ETA is required?
This is a typical example of how a hazard avoidance question will be worded in the exam.
As the turns are 60°, we know that our flight time on the diversion will be twice the time of the original track that we diverted around. So in this case, we flew 3 minutes away from the track and 3 minutes back towards the track, so we need to add 3 minutes to the original ETA.
The 3 minutes spent flying parallel to the planned track has no effect on the ETA.