Vertical altitude override
In all flying modes other then manual a controlled vertical override is available.
In position hold for example you can increase the throttle and the copter will climb with a vertical speed proportional to the throttle, decreasing the throttle will cause the copter descending with a set maximum velocity around 1 m/s.
|In short, any mode with automatic altitude control, the throttle will control the altitude with a throttle deadband in the middle to maintain the current height.|
This is great to use in photographic situations, just use the throttle to climb or fall while staying put in the locked position.
To prevent that any throttle input will cause a change in vertical position, a dead band is present around the throttle center position.
A deadband (sometimes called a neutral zone) is an area of a signal range or band where no action occurs.
The deadband is a settable parameter.
When entering an altitude controlled mode, the current throttle will be used as a baseline but in most cases that is around the center position.
Make sure that the copter will hover around that center position, if you need a lot more throttle to hover the copter you should change the physical powers like bigger props (diameter increase) or increase the lipo cell count.
Adjusting the Throttle Factor (Scale)
The following is the process to calculate and adjust the Throttle Scale (CTRL_FACT_THRO) parameter to set your Manual hover at mid-stick. In AQ QGC it is found on the Radio & Controls setup page, under Additional Control Settings.
View a LOG file with a good level hover and take the value for LOG_RADIO_CHANNEL0 (or whichever channel is your throttle control) from the graph. It should be around 700.
The formula is: Corrected Throttle Scale = Current Throttle Scale * LOG_RADIO_CHANNEL0 value / 700.
If the value read from the graph was 700 it would make no change. If your hovering throttle value is low like in the picture then the throttle factor was too high and needs to be reduced. Using the example from the above log, where the channel value at hover is around 460, and assuming the current Throttle Scale setting is the default 0.7:
Throttle Scale = 0.7 * 460 / 700 = 0.46
Here is a log from the same quad in a hover after throttle scale adjustment from 0.7 to 0.46, showing throttle radio channel properly centered around 700: