For the update procedure from VBar Firmware Version 3.6.16 to 4.0 the following procedures are recommended: 
- at first download the 4.0 PC software and install it
- read out the serial number with the 4.0 PC sof and write it down
- buy now the upgrade to 4.0 in our VBar webshop for this serial number
- after finishing the purchasing process you can do the online update
- please read the manual, watch the videos and take note about the hints for our trim flight
For conversions from 3.6.16 to 4.0 we recommend to watch the videos No. 1, 8, 18,19 20. On every converted hei it will be necessayr to adjust the tail rotor center and travel completly new because we made some changes there.