Maddam asked:
"How likely is it to get into rollover during wheel taxi AW139?"
Any wheeled helicopter is likely to rollover during ground taxi operations if the pilot mishandles the controls. See this accident report on a Dauphin 365 N3
http://dgca.nic.in/accident/reports/VT-SOK.pdf The pilot chose the wrong option i.e. he raised the collective instead of lowering it, when the incipient symptoms were recognised.
Another rollover accident to a wheeled Bell 214ST in Saudi Arabia (ex ROP machine) also comes to mind. I cannot find that report but I am aware that the commander did not have time to intervene when the copilot pulled pitch during the turn into dispersal. The wheeled 214ST had only been added to the fleet of skidded 214B models the week previously.
All 3 types AW139, AS365 and Bell214ST are safe to ground taxi if the pilots are aware of the causes of dynamic rollover and apply the correct techniques to prevent it.
speds