Someone asked why there are different speeds and leg times on holding patterns. I gave up on trying to figure out why the designers do what they do. However, here’s a guess on this one.
Altitude (MSL) Airspeed (KIAS) Leg Time MHA - 6,000' 200 1 minute 6,001' - 14,000’ 230 1 minute 30 seconds 14,001' and above 265 1 minute 30 seconds
If you are holding below 6,000′ you are most likely on an approach to an airport or holding at the missed approach point. By limiting speed to 200kts and legs to 1 minute the protected area is much smaller. Often you will also see a note on the chart limiting the distance from the holding fix. The designer can make the hold closer to the airport elevation which makes the approach easier for the pilot.
The purpose of the hold on an approach chart is for a course reversal or missed approach. On other forums, general aviation pilots have stated that they have never, or almost never, been given a hold for spacing when on an approach. I was given the option to hold once when on a practice approach but opted instead for vectors.
If you are holding above 6,000′ you are most likely not a Cessna 152—you are probably in a much faster airplane. So the protected space needs to be substantially larger. That’s why the airspeed is limited to 230 kts between 6,001′ – 14,000’ and legs are 1 minute 30 seconds.
Above 14,000′ you are probably an airliner or business plane that is holding for spacing purposes. The highest mountain peak in the continental US is 14,505′ and we know that in mountainous areas the MEA is 2,000′ above the highest obstacle. So a hold along an airway has 4 miles on the holding side already protected. And outside of California and Colorado there is plenty of room. ATC can have an aircraft hold without worrying about them hitting the ground. But limiting airspeed to 265 kts and making legs 1 minute 30 Seconds makes it easier to ensure that the airplane won’t hit anyone else.
Holds used to be much more common in the US airspace but the FAA computers do a much better job of estimating traffic and the implementation of ground stops and EDCTs has made them much less common than in the past. From what I have read on other blogs, they are mostly used for unanticipated weather delays.