[fingpilot]

That was a great airplane according to the guys that flew it. The 'tunnel' was so the crew could pass from the front of the plane to the back (past the bomb bays) and stay in the pressurized comfort of (then) high altitude flight. Boeing learned a great deal from Convair about building BIG from that plane.

If you look (not even from too far away) you'll see design elements of the B-52 there.

The propellers were always an issue, they couldn't keep the engine oil warm enough at altitude to flow thru the hubs and control pitch of the blades (meaning engine RPM went out of control. In the time it takes you to say 'instant detonation', you had started melting things in any one of the triple rows of cyl heads). There were jokes about minimum number of engines required to land the plane. I have a grandfather whose logbook has a funny section about total takeoffs with 10 engines and total landings with 10 engines. The two numbers are drastically different. They ended up going with electrically controlled pitch mechanisms (which introduced a whole new set of problems).

As I remember, the jets were used at takeoff, then shut down as radials cooled after initial climb power reduction and cowl flaps went to trail. They were started inflight again at altitude when a climb was needed.