Yes, it is necessary to have a switch that toggles between TE (free flight) &
Static (engine runs). If the TE is used during an engine start the vario
needle pegs up very hard and could cause damage. I use a panel mounted Clippard
Mini-Matic with a toggle switch (previously in a Ventus BT) and currently in my
Nimbus 3T. Clippard has a great web-site and their dealer list is also
provided. After finding the correct size, just call a dealer and they will UPS
one to you.

Steve (PSU)