A Chieftain operator in Qld has brought in a requirement to check the magnetos at top of descent for dead cut at cruise power of 31MAP. While the mag switch is not switched off, the operator simply selects left then right magneto position to see if the engines runs OK. A dead mag will cause a big backfire and the theory is that delays on the ground can be anticipated and other arrangements made in plenty of time before the aircraft lands.
Except, that when the 'big bang' (which is caused by unburnt fuel igniting in the exhaust manafold) caused a failure downstream in the exhaust system (manafold, turbo, etc) will cause a lot more than a small delay. Engine fires are fun.
How completely and utterly dumb.
