The Poms were great destroyers of DC3 engines. Their CAA had this ridiculous requirement for an annual C of A air test. Basically, it involved loading the old girl up with fuel and ballast, blasting off with a sprog co-pilot who had a stopwatch and all the forms to fill out. It didn't matter if it was solid IMC, the test had to be done on the appointed due day; otherwise the aeroplane - already then some 35 years old - would suddenly become unairworthy. Fortunately, it was easier to fly accurately in fog, and the cool conditions probably helped a bit to save the engines from instant destruction.
After logging temps and pressures during takeoff (when CHTs are in a constant state of change, so what they did with this information, I dunno) and time for the gear to retract, we got down to the seriously engine-damaging stuff. The critical engine was feathered (time taken to feather was recorded) and the other one set at max takeoff power - the whole 48 inches - and the climb rate at 86 knots was measured over 5 minutes (or it may have only been 3 minutes, but it felt like forever). Then that engine was unfeathered (timed with stopwatch of course) and the other engine, having been flogged half to death, was then feathered (timed of course) and the first engine then run at METO power for some interminable time like 5 or 10 minutes while the climb continued to be measured; this time at the magic number of 91 knots. When that was over, the by now snap-frozen engine was re-started and we carried out various configuration stalls while timing flap extension times and recording onset of buffet and final stall speeds. We may have even measured VMCA - I can't remember if it was on the test form. We certainly did that one during endorsement training.
The other gross injustice to the old girl was meat-bombing. Most summer weekends we would rip the seats out and 30 parachute-equipped peanuts would sit on the floor while we climbed as quickly as possible to 12,000 feet, then they'd all leap out in waves of 6 or so. While they were floating down holding hands like they were in some kind of love-fest, we had to get the DC3 back on the ground as quickly as possible to pick up the next mob of nutters; to do it all over again.
Although I was always as sympathetic as possible to the engines by cooling them slowly and warming them up again, and I am sure others were also, we always seemed to have a failure within weeks of such silly games. I had two engine failures with this company and I know that there were many more. As a result the company dumped the DC3 as 'uneconomic' when in fact it should have been unbeatable for some shorter routes.