Create AH-9 on Altis next to powerline.
In init field of the heli type:
this addeventhandler ["handledamage", {0}];
This should stop it from taking damage.
Fly into powerline.
Watch game getting confused.
Adding no handledamage EH or adding
this addeventhandler ["handledamage", {_this select 2}];
doesn't seem to cause any problems.
Other combinations that cause avalanche:
this addeventhandler ["handledamage", {0.01}];
this addeventhandler ["handledamage", {0.1}];
this addeventhandler ["handledamage", {0.9}];