This video (though exagerating when animating the autorotation) is quite interesting to watch. Do helicopters on the north sea really get hit by lightning on a regular basis? This cant be true
They do suffer several strikes every year in the North Sea, although the majority are probably static discharges. A static discharge is very hard to predict, and are more common in winter in cold temperatures (around freezing) with snow present. This serves to cook up a nicely charged atmosphere that then needs a helicopter with rotating bits to come in and create an opposite charge. The result is a static discharge. The damage is usually very costly, and often requires replacement of main and tail rotor blades, as well as MGB and TGB's depending a little on the path of the current. I have also seen a case whereby all of the flight controls had to be changed as well as there were very clear scorch marks all the way through the control runs including the tail rotor drive shafts. The aircraft had many burn marks and what looked like shotgun spray - for want of a better description, over the blades where current had entered and exited the aircraft. This is generally the most obvious and common initial indication on inspection. Different types react differently and the overall cause and effect is still poorly understood, as is the actual amount of power contained in lightning, but it can hugely vary. A pure lightning strike as opposed to a static discharge I would say is somewhat rarer, but probably considerably more serious. I suspect they are rarer because we avoid at all costs through the use of weather radar and weather reports. Tests have shown that the heat generated by a lightning strike can cause temperatures of many thousands of degrees C, which has the effect of melting instantly and shearing various parts. Generally our helicopters are well bonded to allow for the transfer of the electrical power through the aircraft, but that is not to say that will be a safeguard. I have seen aircraft lose all their electrics following a strike, aircraft with major structural damage all sorts of other varying degrees of damage.
I believe many people fly around in thunderstorms due to ignorance or inexperience, but for those of us who have seen and experienced their effects, it is something we treat with extreme caution in a helicopter. When you consider the potential of damage to one blade on the outcome of your successful flight you may think twice. Not so dramatic in a fixed wing, but bloody scary in a helicopter. The simple answer is - YES it is bloody dangerous and bloody unpredictable. If lightning is being observed - be somewhere else and wait until it moves away. It generally does not hang around very long. 30 mins usually is enough (not always - google supercells) If it is forecast take extra holding fuel and have a backup plan and landing area alternate.