Aviation, at its present stage, with the devices and engines at its disposal, seems very close to having reached its limit in speed and altitude. There are perhaps a few kilometers left to gain in speed and a few hundred meters in height, thanks to cells refined to their critical point, to machines pushed to their maximum efficiency and resistance, to propellers made lighter and more solid by duralumin, to pilots of incomparable skill and audacity: however, we can hardly hope that the planes will fly at more than 500 kilometers per hour and that they will exceed 12,000 meters at above sea level.

The supercompressed internal combustion engine, running on benzol at low altitudes and fueled by gasoline at great heights, is still the king of powerplants. Will it always be?

It does not seem likely to be dethroned by the steam engine, which Ader used on his bat, and which the United States has rehabilitated by using it on automobiles, or even on airplanes. The result of the tests was just satisfactory for the cars and it has not been published regarding attempts to adapt to heavier than air.

The electric motor is currently neglected. However, the France airship, designed by Renard and Krebs, was equipped with an electric motor which managed to develop a low power of 8 horsepower. This motor was powered by batteries. We cannot imagine an electric motor installed on board a modern-day aircraft, because the accumulators would be terribly bulky and prohibitively heavy. The only solution would be to power this machine by telemechanics, by waves transmitted from the ground or by capturing the electrical energy spread in the atmosphere. Until now, tests of using ambient electricity have only just made it possible to light lamps, which is already a very honorable result. The compressed air engine, of which it is surprising that no application has been made to automobiles, worries the Germans, who have carried out all kinds of experiments in the Rhineland, with no currently known outcome.

Machines operating with heavy oils, alcohols, charcoal, such as Diesel, semi-Diesel, Tartrait, etc. must be linked to internal combustion engines. The gas turbine, which has been the subject of countless research, has not yet provided a real solution. The Coanda turbine does not do without the internal combustion engine; it simply replaces the propeller. The Odier turbine, the efficiency of which the Technical Section is currently studying, is the driving force. It forms a powertrain which retains the use of the propeller.

Will we ultimately be reduced to perfecting the internal combustion engine and the propeller? All hope is not lost. The jet propellant has been the subject of numerous studies, the oldest of which is that of Mr. Robert Esnault-Pelterie.

What is jet propulsion? This is the thrust effect caused by the reaction, in the ambient air, of a gas jet. It is, in short, the application of the rocket principle. Tests of direct propulsion by reaction have been applied for more than thirty years to river boats and cars, but without conclusive results, due to the enormous loss of energy due to the high speed of exhaust gases. combustion. Mr. Esnault-Pelterie sees the jet engine as the engine of the future. Captain Hirschauer is of the same opinion.

A young French engineer, Mr. H.-F. Mélot, is currently experimenting at the Technical Section with a jet propellant that he invented in 1918 and has been developing since then. This device would be adapted to current model aircraft, and it would replace the internal combustion engine, the propeller, and it would eliminate all the mechanical operating difficulties of the powertrain. The gases necessary for combustion would be provided by gasoline, alcohol, heavy oils. It is reasonable to predict that they could also be produced by powders or explosives. Papin and Rouilly's gyropter, which would rise vertically like a helicopter and which began to be tested during the war, is also based on the principle of direct reaction propulsion.

What will result from the researchers' efforts? Will the direct reaction propellant supplant the current explosion engine-propeller formula? The next future will teach us. At the same time as adapting his jet propeller on board large-scale aircraft, Mr. Mélot is considering entering an aircraft in the Tour de France des avionnettes, which the French Air Association is organizing from July 24 to August 10. It therefore appears that the era of achievements of the new powertrain is near. GABRIEL HANOT.