Many aeronautical books, state that the historical Dec 17, 1903 Wright Bros´ flight was the first SUSTAINED powered flight.
The data we are given is that the aircraft weighed about 840 pounds, and that the engine produced about 12 HP, that they used a catapult to assist the take off, that they had pretty efficient propellers (then) and that they were flying into a plus 25 mph wind in front of some sand dunes. We are also told that the aircraft´s stall speed was in the order of 32 mph.
I am not an aeronautical engineer, but I have read that a practical way to estimate the power requirements for sustained flight is to divide the aircraft´s weight by its L/D (at that speed).
An esay way to measure
Now, if you look at the aircraft, it is not as refined as, say, a QuickSilver ultralight (2 wings instead of one, many more wires and struts, but on the other hand, a pilot prone position, instead of a seating position). The Quicksilvers best L/D (glide ratio) does not exceed 5 to 1.
950 pounds (aircraft plus pilot) into, say, 5 = 190 pounds of thrust required to sustain level flight.
A very good UL prop over 64 inches in diameter that does not turn more than 2,500 rpms will produce about 5 lbs per HP of static thrust.
So, using these numbers the power requirement would be at least 195/5 = 39 HP.
The best ultralight single seaters designed for minimum power requirements need at least 25 HP aprox to keep aloft.
Granted that ground effect if flown very close to the ground would reduce the power required considerably.
No matter what reasonable propeller or aerodynamic efficiency we consider the power gap is too big to consider that historic flight as truly "sustainable"
No wonder, all true replicas built on the anniversary never flew off the rails.
The only ones to fly had a Harley Davidson 83 HP engine on.
I ask myself (and you):
Wasn´t that historic flight (recorded by cameras and witnesses) really a slope soaring flight taking advantage of those very high winds ?
Can anybody "straighten" my numbers ?
I could be wrong...