||Charles County RC Field
||Rev 2.2 with CVS head as of 2002-08-18
First step was to calibrate the accelerometers. Roll knife edge left,
knife edge right, nose down, nose up then back to level.
Next we held the rotor head and spun the aircraft 360 degrees clockwise.
An uneventful liftoff. Notice the yaw wagging -- the ball bearing gyro
was not very well attached to the airframe. Engine vibration transmitted
to its housing would cause it to wobble, leading to anti-torque inputs.
Aaron performs a pitch doublet of increasing frequency.
Followed by a roll doublet of increasing frequency. Note the
cross roll/pitch coupling visible in the gyro data. It is odd that
the accelerometers do not show more visible rolling during the low
In this graph, Aaron held the aircraft in a constant rate clockwise
pirouette for roughly 10 seconds. The estimated rate of turn was
60 deg/sec. Note the large noise level in the accelerometer data.
Now Aaron holds the aircraft in a constant rate clockwise pirouette
for roughly 40 seconds. The estimated rate of turn was 100 deg/sec.
Note the constant cyclic commands required to hold the helicopter in
one point over the ground. At some point during the flight the tail
rotor pitch control slider broke; we're not sure when this happened and
are still trying to identify it in the yaw noise.
It is difficult to compare the noise levels in the previous two graphs,
so I have extracted 10 seconds of pitch accelerometer data from each
and combined them on this plot. You can clearly see that the three
zipties used to hold the radio tray to the airframe's keel made an
enormous difference in the noise. Without the canopy installed, we could
see the tray vibrating quite a bit.
On the last flight of the day, Aaron flew until we were out of fuel.
We should have noticed the vibration noise levels reduced in the
accelerometer data, but due to other factors (blade balance, etc)
we did not. Unfortunately, the helicopter had its forward velocity
arrested suddenly and might have damanged the pitch accelerometer.
You can see its sensor reading become invalid after the touchdown.
The other sensors settle down as usual.
I've traced the problem to a broken resistor. Due to the way I had
strapped the Rev 2.2 board to the airframe, the shock snapped a
resistor lead that had been bent too tightly. I'll have to resolder