and you should also choose the profile that matches the
accelerometer orientation.
It is strongly recommended that you use the PB-4's offline capture
button to capture the data while flying as this obviates the need to
interact with the tablet while flying, it doesn't even need the tablet
to be in the aircraft. If you want to use it, check that it has been
enabled in the
.
If you do wish to use the tablet to capture the points, consider using
the data tab as that just requires you to click on the data display
box so it's easier to do while flying. Check that it has been set up
to capture points (and optionally, spectra). Also, if the machine has
an open cockpit, take precautions to avoid the tablet disappearing
aft through the propeller! If possible, attach it firmly to a knee pad
or to the aircraft structure.
8.3.1. Measuring the effect of adjustments
Before the move lines can be created, you will need to measure the vibration
(capture polar points) for two different values of each adjustment. For example,
to define the spanwise move line you need to add weight to one of the rotor
blade tips, enter the adjustment value as described in
and capture
a few polar points. You then move the weight to the other rotor blade tip, enter
the new adjustment value and capture a few more points. Finally, remove the
weight again (to return the rotor to the original condition).
The process should be repeated to gather the data required to define the
chordwise move line. This time the adjustments would involve shifting the
rotor mass on the teeter pivot. Lastly, you could gather the data required to
define the pitch move line (if required).
Important
To ensure that the move lines are good, follow this advice:
• Only make one adjustment at a time.
• Always fly the aircraft at the same speed, weight and rotor RPM
when capturing the data.
• Fly smoothly and avoid turbulence.
• Capture multiple points (3, say) to avoid being fooled by a “rogue
point”.
• Wait a few seconds between capturing each point to give the
PB-4 software time to measure and average further points.
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Measuring the effect of adjustments
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