Please click on the below link, download the PDF and READ IT. It relates to very important announcement to do with mast rocking in the R44. http://www.ntsb.gov/doclib/recletters/2011/A-11-082-086.pdf
This has been experienced in our R44's from time to time, I believe it mostly reflects the condition of the gear box mounts. The most severe event I experienced was in a machine we had just got back out of overhaul and it would sometimes enter into this ( for & aft- bounce / lurch ) as you returned to your paddock with a full chemical load whilst making a decending turn to line up onto your spray run. Sometimes it would become quiet alarming, but when you applied power and leveled into the spray run it would go away. At the next service we removed the gearbox mounts which turned out to be the softer ones, and refitted with the updated harder mounts. This immediately cured the aircraft of having this problem. You can tell when the gearbox mounts in the helicopter you are flying are in need of being replaced because the bounce / lurch will start to occur gradually and become more prevalent until the mounts are changed. I liken this type of ( for & aft - bounce / lurch ), back to my mustering days flying Bell 47's and the sprag mounts were shot, allthough the R44 can be a lot more violent.
Appreciate the info, HeliOps. Thanks for sharing your insights Ashley. Good to know RHC is teaching this at it's safety course, Dave.