Again, coming back to Hiram Maxim, that article from Scientific American - September 15, 1894 [From Engineering, London], about a flight on July 31, 1894, does not talk about witnesses and the evidence, it presents to support the flight, is indirect: "
The machine fell on to the soft sward, embedding its wheels deeply in the grass, and testifying, beyond contradiction, that it had fallen and not run to its position. If it had not been in actual flight, the small flanged wheels would have cut deep tracks in the yielding earth."
The ideal flight of Maxim's plane, if everything had worked perfectly, would have been 1 inch above the steel rails!
"
Four extra wheels were fitted to the machine on outriggers and so adjusted that, if the machine should lift one inch clear of the steel rails, the wheels at the ends of the outriggers would engage the under side of the pine trackway." ...
Source:
The Pioneers : An Anthology : Sir Hiram Maxim (1840 - 1916)
The description given by Hiram Maxim himself about the flight is quite complicated. He was not 100% sure his plane had really flown, even at a height of 1 inch. It is not quite clear what happened to the right wheel which rolled on one of the steel rails. After running 1000 feet the plane started to tear up the upper rail with its outer right wheel. This means the inner right main wheel could well have been in contact with the steel rail. It is also not clear how far from the steel rail Maxim's plane stopped. The flying machine could have been 6 wheel in the air but the other two (right front) evolved in a mysterious way. Also, between 600 and 900 feet the plane, according to Maxim, floated 1 inch above the steel rail. Are we sure all inner wheels were in the air simultaneously? I have serious doubts the machine had such a vertical stability to fly (even guided horizontally by the outer wheels) 1 inch above the rails for 300 feet, a long distance.
Maxim's own words:
"
The enormous screw-thrust started the engine so quickly that it nearly threw the engineers off their feet, and the machine bounded over the track at a great rate. Upon noticing a slight diminution in the steam pressure, I turned on more gas, when almost instantly the steam commenced to blow a steady blast from the small safety valve, showing that the pressure was at least 320 lbs. in the pipes supplying the engines with steam. Before starting on this run, the wheels that were to engage the upper track were painted, and it was the duty of one of my assistants to observe these wheels during the run, while another assistant watched the pressure gauges and dynagraphs. The first part of the track was up a slight incline, but the machine was lifted clear of the lower rails and all of the top wheels were fully engaged on the upper track when about 600 feet had been covered. The speed rapidly increased, and when 900 feet had been covered, one of the rear axle trees, which were of two-inch steel tubing, doubled up and set the rear end of the machine completely free. The pencils ran completely across the cylinders of the dynagraphs and caught on the underneath end. The rear end of the machine being set free, raised considerably above the track and swayed. At about 1,000 feet, the left forward wheel also got clear of the upper track, and shortly afterwards the right forward wheel tore up about 100 feet of the upper track. Steam was at once shut off and the machine sank directly to the earth, embedding the wheels in the soft turf without leaving any other marks, showing most conclusively that the machine was completely suspended in the air before it settled to the earth. In this accident, one of the pine timbers forming the upper track went completely through the lower framework of the machine and broke a number of the tubes, but no damage was done to the machinery except a slight injury to one of the screws."
Source:
The Pioneers : An Anthology : Sir Hiram Maxim (1840 - 1916)
Hiram Maxim's plane
Hiram Maxim's plane