Cumulus Granitus

Having worked in PNG in the same airline that has just crashed, and in fact on those exact aircraft, I can say that yeah flying up there is scary seat of the pants stuff... What most of the "pilot commenters" on various TV programs aren't explaining properly is the relationship that mountains, clouds, and airplanes share up there.

Aircraft are generally VFR (Visual Flight Regs) and limited to remaining in sight of the ground. In most places, that means you stay beneath the clouds because the ground stays underneath the clouds..

In PNG though, the base of the cloud and the terrain intersect a lot, so you can often be above the clouds and still in sight of the ground, thus technically flying VFR. The problem arises when you're flying along following the ground, and suddenly find yourself above a blanket of rapidly-moving cloud.

Well, actually, the problem arises when you look for a hole in the cloud to get back in sight of the ground, drill down into it, and you suddenly find that the cloud has terrain in it. The pilots that flew our aircraft in the 70's had a word they coined, "cumulus granitus" which you can loosely translate for yourself...

UPDATE 2024: This was originally posted when a light aircraft, (I think mission-owned) crashed and in Australia there was this blank "how could this have happened?" attitude. I've personally been in an aircraft that was flying at the correct altitude, and as it flew, cloud rushed in below us faster than we could fly, blocking the view of the ground. With only basic instruments, it was impossible to know if we were over a peak, a ridge, or a valley. Getting under the cloud could have involved any of those, only one was safe. And we did fly back along our track until a rift in the clouds, descended, checked for terrain very carefully, and descended through the hole to regulation below-cloud height. Luckily we had a valley we could follow out under the clouds. There are always variables in flying, and some are more dangerous than others. Controlling for those variables is why modern airliners are bristling with technology to mitigate those variables, and pilots get updated regularly. Please help support the blog by sharing and donating.