Originally Posted by
Baradium
The DC-7s have turbo-compound engines which are incredibly maintenance intensive. The DC-6 was fondly called the best 3 engine aircraft ever made while the DC-7s were flying emergencies. There were also a lot more DC-6s and 4s available to fly than 7s in the first place.
https://en.wikipedia.org/wiki/Wright...Duplex-Cyclone
True story - that is how my Dad got his start in commercial aviation with a 9th grade education and a GED. Air Force made him a mechanic, then crew chief and got his ratings out at the flying club. Cargo carriers hired him not necessarily to be the world's best second officer, but to fix the damn thing when it broke, blew up, went kablooey or caught on fire; which was often. Second Officer > First Officer > Seaboard > Flying Tigers > FedEx ... worked out for him. Not bad for a brighter than average wrench.
He's 80+ now and with his feet on the floor can tell more about the health of the engine in my airplanes than a digital engine analyzer. He's freaky when it comes to figuring out the balance of fuel delivery and health of cylinders.