This blog entry borderline germane, nonetheless interesting.
That German Dornier Do X flying boat, the push-pull engine design incorporated, a grand total of twelve engines all in operation all at once.
From a casual glance it appears the Do X has six engines. Wrong.
A flying boat having a waterproof hull not using floats for buoyancy.
"The Dornier Do X was the largest, heaviest, and most powerful flying boat in the world when it was produced by the Dornier company of Germany in 1929."
"It was initially powered by twelve 391 kW (524 hp) Siemens-built Bristol Jupiter radial engines (six tractor propellers and six pushers), mounted in six tower nacelles on the wing."
Here with a better view of the engines mounted back to back. The turbulence and air flow from the tractor [puller] does NOT interfere with the airflow of the rear [pusher] engine and propeller?
Those engines, twelve of them mounted back to back on the wing, one operating as a tractor [puller] the other as a pusher. This design particularly unique to the Do X?
This is the flight engineer in action. That plane cannot have been easy to fly if indeed one or more engines had to be taken off-line. Compensating for difficulty an intense concentration a must at all times? Such was the technology at the time!
"While never a commercial success, the Dornier Do X was the largest heavier-than-air aircraft of its time, a pioneer in demonstrating the potential of an international passenger air service."
The modern flying boat often suggested as a means of power projection, enormous flying machines even larger than the Do X having a capability using wing-in-ground lift as a means to transport prodigious numbers of troops and material long distances and do so in a rapid manner.
That seventy percent of the earth's surface is covered by water offers potential "landing strips" to be almost anywhere. But that concept, the large-scale flying boat transport never seems to have "taken off"!