I fly tourist's during the of NZ summer season, and we land at 7000amsl on the top of the glaciers t let the tourists get out and have a walk on the snow. Now we leave the machines running the whole time, for a few good reasons.
1: Up there the weather can change really fast, it always amazes me just how fast. You can go from a picture perfect day to having cloud rolling in a matter of minutes and then the whole valley is gone...but then it can clear just as fast. So I dont really want to get stuck up there with the pax, so if it turns, we can bundle them in and get going again.
2: On a good day, we can do over 20 flights up there, so shutting down every 20-40 mins seems pointless, plus costly. Also if you cant restart.....see above. PLus refueling, seeing we only carry upto 56%, and dont ever go below 20%, it takes hardly anytime to refuel so again its easier to leave it running.
Now before anyone jumps up and down saying it only takes 30 sec to shutdown....we operate Super D's and D2's....which have a 2 min cool down time. I have refueled in that time.
It is not without its risks, but careful pax managment and proper safety briefings then the risk is reduced vastly.
cheers all
Hughesy