Its a good discussionThe land at full collective thing, here is where it comes from:
If you land at less than full collective, you still have energy in the head and furthermore the blades are not flying as high as they possibly can.
If someday you have a "rough" landing at less than full collective, one were you hit a little hard and bounce so to speak, what can happen is the blades will flex down from the bump and if you're unlucky and the blade happens to be in the right place it will catch the boom and you'll get the instant boom strike. Doesn't always happen as sometimes you hit when the blade just passes the boom in this case the blade will bend down and back up before it gets to the boom. So its not always obvious.
But if you land at full collective even if you bounce the blades are flying higher and the chances of a boom strike are lower. Spool up your heli and look at the blades at 0 pitch and then at +4 degrees say before liftoff. You will see when you add pitch the blades rise up, and when you lower it they will drop down.
This is like telling you to slow down when you turn on a wet road. If there are leaves on the road in the fall you could skid and wipe out. If there isn't you probably won't, but its the same idea.
Land at full collective gives better chance of success given a bounce than not. I can land all day at part collective too and pick it up and put it back down, but I choose to fly it out until its stalls in or in other words I touch down at the same moment my stick touches the stop on the top of the TX.
As far as 0 pitch, that is the minimum collective you can use to auto down, which would produce the slowest auto possible, and you're right you will lose headspeed all the way down but you'll get something like a 30 to 60 second auto depending on how high you start, maybe even more if you can see it higher than that. I did a 52 second auto last week after a 15 second climbout at full collective here at the field doing just this. At the end of the auto, the blades are pretty well scattered and you drop in faster and faster and you just punch full collective and bounce in so to speak. This is for experts only (the bounce in landing) as I was trying to stay aloft as long as possible to get a longer time (52 seconds). Of course you can drop pitch from 0 to -4 say at 150 feet regain some head speed and do a greaser landing if you want.
MA 1005 Hanson 280, 4210 flts
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Whiplash V1-2 Hanson 300, 1570 flts
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