Specifications

The Corona doesn't have a feathering shaft, and instead has an aluminum rod which holds
the subrotor on the rotor hub. This rod is very thin and has a tendency to bend after a few
crashes. You will notice this because the subrotor paddles will "droop down" and will not be
parallel to each other. This problem can be easily fixed by carefully bending the subrotor
paddles up to straighten the aluminum rod or bye replacing the aluminum rod.
• Check if the rotor head is balanced. Reinstall the head and swashplate assembly but re-
move the main rotor blades. Connect the battery and slowly apply throttle. If the heli is vi-
brating then you should check if the flybar is straight and centered and balance the main ro-
tor head using a Tru-spin prop balancer or equivalent.
• Check if the main shaft is bent. A quick test for this is to remove the main rotor head,
swashplate and all the related linkages. Run up the motor without the head and hold a
screwdriver against the top of the shaft as the shaft turns. If you feel vibration while holding
the screwdriver against the turning shaft, then the shaft is obviously bent.
If you do not feel any obvious vibration, then the shaft may still be bent. To perform a more
precise test for bent shaft checking, first you need a perfectly flat surface, preferably a
sheet of glass. It isn't necessary to remove the glass cover from a frame; just use the entire
photo or award.
Second, take a new shaft and place it on the glass and tilt the surface slightly. Watch it roll
back and forth as you tilt the surface. The first thing you should notice is a straight shaft will
easily start rolling from a stopped position. You do not need to tilt the surface very much to
start it rolling. The second thing to notice is a straight shaft can be rolled at all speeds. If
you tilt it only slightly, it rolls very slowly. If you tilt it a lot, it rolls very quickly.
Now remove the new shaft and place the suspect shaft on the glass. Roll the suspect shaft
back and forth as you did the new shaft. If the suspect shaft requires more tilt to start rolling
than the new shaft, then it is bent. If the suspect shaft cannot be rolled as slowly as the new
shaft, then it is bent.
If you hold the surface to your eyes and roll the suspect shaft, then you may be able to see
gaps between the shaft and glass as the shaft rolls. If you can see these gaps, then the
shaft is obviously bent.
• Check the main rotor bearings. Remove the main shaft bearings from the helicopter. Put
the main shaft through each bearing and spin it by hand. If the bearing does not rotate
smoothly or feels gritty, then replace it.
26.1.2. Excessive vibration (tail only)
Checklist for tail rotor vibration
• Check tail rotor blade balance
Reinstall the main rotor shaft and main gear, but do not reinstall the head and swashplate
assembly. Remove the tail rotor blades and run up the helicopter. If the vibrations are gone,
then the tail blades need to be balanced or replaced.
• Check the tail blade grip spacing
If the tail blade grip screw is not screwed in equally on both tail blade grips, then the tail
blade grips will not be the same distance from the center of rotation which will cause vibra-
tion.
Troubleshooting Common Problems
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