The B-29 is not type-certified because they were never used for a civilian job. As a result, they must operate under the "experimental" category. The engineer is the only one who must be certified. The position is that complicated. They say it is confusing for a pilot to become an engineer because of the orientation of the panels. They are reversed (engineers 4-3-2-1) rather than in normal order to match the reversed seat. By the time the plane neared production they new the reversed engineer was a mistake. Instead, they should have placed him facing sideways like they did in the C-97. But the production schedule was so urgent that they just left the design as-is.
The CAF runs FIFI with a six-man crew. The FAA is often after them for that because they prefer minimum crews on planes at air shows. But the B-29 still has problems with engine fires and needs spotters in the back to watch the engines. They say that from the time a fire is spotted to the time the wing collapses you've got a minute and a half to get everyone out. The crew wears parachutes. The pilots keep the flaps up when they are on the ground because they block the spotters' view of the engines. They retract them at the first possible instant. The reverse is true on landing.
The B-29 is known to pull to one side on takeoff and there is no nose wheel steering (it just casters). As a result, it is normal to take off with differential throttles. Speaking of which, there are three throttles coupled to each control surface (pilot, copilot, engineer) which contributes to a loose throttle system. The main mounts would like to come off the ground first when taking off!!!
More, HERE and HERE.
Bob