Just a couple things to check Dave . You shouldn't have to run noseheavy , I
don't have an Xterminator but it's been my experience that recommended CG's
are usually at least a touch on the conservative side . Something else is
most likely wrong as you suspect . I would return to the recommended CG and
look elsewhere for corrections .
Is there anything loose in the fuse ? , more specifically is the battery
secure ? Usually more often a power plane problem ( huge empty fuse for
batteries to roll around in ) . But I had to ask . Variable CG make you
chase the plane around the sky rather erratically stall/dive , stall/dive
... - usually can't be trimmed at any speed , changes every time the plane
changes attitude .
Loose servo mounts ? Control rod/cable bind ? Servo centering problem ?
Bottom line - does the elevator/vtail surfaces return(center) to the exact
same place when moved up full throw compared to down full throw . Don't rule
out poor servo percision without first checking . That one will drive you
nuts .
If it looked OK mechanically then look to alignment .Can you trim it to fly
level at a slow speed but it slowly porpoises at any faster speed (launch
speed or dive) . Check your decalage - the relative alignment (incidence) of
the wing and stab/vtail . If you notice your elevators are flying with some
down trim at cruise speed then try to spacer up the trailing edge of the
wing . 1/16" at a time until the elevator(s) cruise at level ( minimum
drag ) . If this was (part of) the problem you should notice a wider speed
range for a given trim setting now , and a longer glide . It's usually
trainer type planes that are designed with extra positive incidence - that
makes the plane sort of auto-recover from a dive .
Then there's the dive test ... well it should be made stable before that ...
Hope that made sense ,
Wayne
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