Futaba GV-1 - Manual (Page 26)

FUNCTIONS
Set the speed of each point by repeating step "2".
The set points can be verified at "rSx" (x=1,2,3) of the
display screen.
Speed
Point 3
rs3
Point 2
rs2
Point 1
rs1
Neutral
Speed setting
channel travel
Note:
When the speed setting channel travel (ATV, AFR) is made 20% or less,
points 1 and 3 cannot be set.
Speed setting points
The engine maximum speed range limits the maximum speed setting.
Test fly the helicopter with the governor turned off and tach the main rotor
R.P.M. while in horizonal flight. This is the maximum R.P.M. that can be
achieved with the engine and pitch setup that you are using. Please set the
governor maximum speed to approximately 50 R.P.M.'s less. (Example: If
1800 R.P.M.'s is max then set governor to 1750)
The maximum speed can be verified at the MAX. speed display, however
this could show some unlocked main rotor condition which is not accurate.
Reference
The transmitter ATV function can also be used to change the point 1 and
point 3 speed settings to a certain extent. The amount of this change is
proportional to the difference between the point 1 and point 3 set speed and
the point 2 set speed. For example, if point 1 is set to 1300rpm and point 2
is set to 1500rpm, and the transmitter ATV is changed from 20 to 100%,
the point 1 speed will change from 1460 to 1300rpm. The transmitter ATV
function has very little effect on the point 2 speed setting.
The speed changes linearly on a line
connecting points 1, 2, and 3.