feet. This trigger is also useful as part of a landing detection. To detect landing, set
AGL3 well below the main deployment altitude but higher than the highest terrain that
the rocket might land on. Set the velocity < 0 check (so that it won’t happen on the way
up), and set the accelerometer check consistent with the direction of the landing impulse.
For a typical setup with the rocket’s main chute attached above the av-bay, look for a
positive acceleration, and use a value that is higher than the rocket might get on the main
chute (> 1.5-2 Gs), but lower than the landing impulse (typically 5-20 Gs). Note that the
default settings in the FIP for landing detection assume that the av-bay will land in the
same orientation as it has on the pad. If your rocket configuration leads to a nose-down
landing, the landing detection should be set up to look for accel < Accel2, and Accel2
should be set to a negative number.
Burnout counter (default of 1 for all outputs):
This condition is the count of the motor burnouts detected by the Raven. It is settable
between 0 (don’t wait for any burnout indication) and 1023 (not that anyone can make a
1024 stage rocket!), and the burnout count can be set individually for each output. The
Raven watches for a change in velocity of at least 40 ft/sec, and then waits for the
velocity to drop by at least 5 feet/second before adding 1 to the burnout count. When the
burnout counter is greater than or equal to the user burnout count for that output channel,
the trigger will be true.
Unlike the burnout counter used in other altimeters, this version will not mistakenly trip
if a launch rod snag or noisy motor burn causes a brief drop in the motor thrust. It also
won’t mistake a stage separation charge from a motor ignition. However, very low-
impulse airstart motor may not trigger the burnout counter, so this should only be used
for motors that will increase the velocity by 40 feet/second or greater.
Calibrating the accelerometer:
The Raven has a user-calibration function for the accelerometer to ensure correct
accelerometer operation and account for accelerometer drift over time. If the average
axial G reading in the live data is outside of 0.8 to 1.2, the accelerometer should be
recalibrated. To calibrate the accelerometer, push the “calibrate” button in the cal/test
flight tab and place the Raven on a flat surface on its short edge. Follow the FIP
instructions to hold the Raven in each of the 4 positions shown. Each position is a 90
degree rotation from the previous position.
Running a flight simulation
The Raven has a flight simulation feature that allows a realistic flight simulation to be
performed on the Raven, using the Raven’s own sensors, the current deployment logic,
and real activation of the outputs. This is useful for verifying the deployment settings, as
well as the compatibility of the Raven power source with the e-matches or igniters used.
