and experiment. The variable pitch propeller has been further developed to provide a complete reversal of pitch. This opens up new possibilities for brake effect on the ground and for use on airships in place of reverse gears. Variable pitch propellers have been tried on the Naval Airship C-10 and have proved very useful approaching a landing. One notable demonstration was made by the Army in California.

NEW ENGINES

New engines brought out in 1920 include improvements and refinements in existing standardized engines and a few entirely new. designs. Under the first classification come the 180 and 300 h.p. Wright engines which virtually complete the Americanization of the Hispano-Suiza which has been going on for the last three years, and under the latter come the new Aeromarine 120, Aeromarine 180, Packard 300, and Packard 600 h.p. types. The Lawrance 60 and 200 h.p. air cooled engines have been mentioned.

The Wright 180 and 300 h.p. models are essentially developed engines, and the changes made from the French designs are in the nature of simplification to give longer operating life and easier maintenance: V magneto brackets, dry sump, gasoline gear pump, thicker heads, more accessible connections, etc.

The Packard 300 h.p. is a new engine of 12 small cylinders and has given a very good account of itself as an economical smooth running engine. The Packard 600 h.p., however, is still an experimental engine. It failed to run in the Gordon Bennett race, but won the Pulitzer Race running at reduced power. The engine, however, is of a type much needed for larger planes which are now equipped with two engines, and it is hoped that 1921 will show the development stage passed.

The Aeromarine six cylinder 120 and eight cylinder 180 h.p. types are among the first engines that appear to be designed for commercial use. Both have been thoroughly tested on the block and give every promise of being sturdy dependable engines as nearly fool-proof as possible. Removable heads are a feature that appeals to the man in the field.

New engines under construction which should be heard from in 1921 are an eighteen cylinder engine of 700 h.p. building at McCook Field, and a special six cylinder heavy duty airship engine of over 300 b.h.p., for which the Bureau of Engineering at the Navy Department has let contracts with three separate manufacturers. The same Bureau has a large number of Liberty engines being rebuilt to incorporate a reduction gear.

"DOPED FUEL "

One of the outstanding technical accomplishments of the year is the culmination of the work of Kettering and Midgley on doped fuels. It has long been known that high compression engines knock badly on Pennsylvania gasoline, and that such engines knock less with California gasoline. It has now been determined that the addition of very small quantities of any one of several aniline derivatives to gasoline eliminates knock, that the pinking or knocking is not due to preignition but to detonation during combustion, and that higher compressions may be employed in aviation engines than were heretofore considered practicable.

A plausible and useful theory of knocking has been explained and practical use is already being made of it. If engines are run on benzol-gasoline mixtures, there is danger of freezing in cold weather and the benzol attacks rubber connections in the fuel leads. About 20% of benzol does stop knocking and makes a good fuel, but as little as 2% of aniline is claimed to be equally effective without the bad effects found in benzol. The Germans introduced blending with benzol during the war on account of the shortage of gasoline, but quickly discovered that with benzol-gasoline mixtures higher compression was permissible. The B.M.W. and later Maybach engines show the influence of this idea.

PROPELLERS

During the year further data for the design of propellers was furnished by the publication by the National Advisory Committee for Aeronautics of another report on Profs. Durand and Leslie's comprehensive research. So far as propeller performance in free air is concerned, the information available is now very complete. Unfortunately the mutual influence of a tractor propeller and a fuselage with a blunt entrance (or a nose radiator) is not known and evidence is accumulating that a good propeller design will give an abnormally poor performance when used with certain blunt fuselage forms.

Experiments during the year on the construction of propellers have led to improvements. The Forest Products Laboratory has developed improved methods of selecting, drying, and gluing propeller woods and an aluminum leaf coating to prevent change of moisture

content.

Propellers have been covered with linen and with leather in efforts to reduce erosion from rain drops and molded propellers of a bakelite preparation have been used with success. Metal propellers have not yet been proved practical but there is great promise in future developments along this line.

TORPEDO PLANES

The problem of the torpedo plane has been active during the year. The first torpedo carrying plane was a makeshift made up at the Naval Aircraft Factory from a lot of old Curtiss R.-6 seaplanes rebuilt with a Liberty engine and larger pontoons. These were used for practice drops in the schools.

Next, Glenn L. Martin built his well known Bomber with a divided landing gear so that a torpedo could be carried under the fuselage. The useful load was not sufficient and a further change was made by adopting an "Albatross " profile for the wings. To make up for the greater drag of this high lift wing, streamline wires were introduced. The result is that with the same power the modified torpedo carrier, I.M.T., has a high speed one mile in excess of the standard bomber, carries 1,600 lbs. more load and has a landing speed 2 miles lower.

SHIP PLANES

During the year the Naval Aircraft Factory has fitted hydrovanes and flotation bags on a number of land planes to adapt them for shipboard work. Experiments have been carried out with Hanriot, Nieuport, Sopwith, Vought and Loening planes. Parnall ship planes have been imported for test purposes, as well as Fokker and Macchi types. The problem is to develop a handy plane which can fly from a ship's deck, land again upon the deck, or in case of engine trouble, alight on the water and remain afloat. Experiments will continue with the collier "Jupiter" converted into an airplane carrier and renamed "Langley."

THE HELICOPTER

It can hardly be said that any great progress has been shown toward the development of a successful helicopter or direct lift machine, although there has been a surprising amount of interest evidenced. The technical journals have carried articles "proving the practicability of direct lift with screws and several experimental machines have been built.

The Hewitt-Crocker scheme has been tested on the ground and showed a good lift from the screws. But it has not flown. The Damblanc machine in France has had similar tests, but again no flight is recorded. It is reported that during the war, a helicopter was tried in Austria by Prof. Karman which did attain a considerable altitude while attached to the ground by several wires. So long as the machine kept a good tension in the wires, the equilibrium was maintained, but no free flight was attempted, as no means were pro

vided for steering and control. The idea was to replace the kite balloon at the front with a small direct lift machine. The advantages seem obvious but the experiments were abandoned.

A most interesting helicopter is that of Emile Berliner of Washington. With an 80 h.p. Le Rhone engine, H. A. Berliner has made several actual flights at an altitude of six feet or so. These were really sporting events, as the transverse motion was a crablike scuttle in random directions depending on the inclination of the machine. A circle of swift footed friends assisted in the control of the machine at critical times. However, the problem of control has now been shown up clearly, and various devices are proposed to solve it.

RACING

The year 1920 has seen the revival of racing, with the Gordon Bennett contest in France and the Pulitzer Trophy Race in this country. Both competitions were purely speed affairs but, fortunately, were over courses long enough to require some degree of reliability.

The Gordon Bennett race was naturally a great disappointment to American aeronautical engineers on account of the failure of the three American entries, each of which possessed new features of obvious interest. However, if any lesson can be drawn it is that a speed race is a gamble on whether any given machine can start and hold together long enough to finish. The French could have won the Cup this year with a training plane.

Technically, the French winner showed no advance in design over their best of 1918, but that best is still an object lesson to the world in harmony of form and superb finish.

The Sopwith entry was to have shown the 450 h.p. Jupiter and the British Nieuport the 300 h.p. A.B.C., both air cooled engines. It is of the greatest technical interest to know whether the additional head resistance of such radial engines is made up for by the saving in weight over, say, the 300 Hispano as installed in the winning French entry.

The Curtiss and Dayton Wright entries were monoplanes in which every artifice had been resorted to in the effort to obtain aerodynamic efficiency. The Curtiss reduced the landing gear to a most rudimentary type without shock absorbers, while the Dayton Wright had mechanism completely to retract the landing gear into the fuselage. The Curtiss scheme is light and simple, but demands a perfect landing field. The Dayton Wright scheme obviously saves an important amount of resistance.

The most novel and interesting feature of any entry was the variable camber device in the wing of the Dayton Wright. The theo

retical advantages of variable camber are well recognized and its adoption has been deferred only by mechanical difficulties. With regard to the Dayton Wright design, the question remains to be answered from experience: Does the aerodynamic advantage compensate for the mechanical complication and risk of breakdown? The resistance of operating mechanism on top of the wing does not seem to be inherent in such gear and should be eliminated in a perfected design.

The U. S. Army entry mounted for the first time the new Packard 600 h.p. engine and was by far the most powerful machine in the competition. The design of the plane was clean, but conventional.

The American entries in the Gordon Bennett Race failed from an excess of optimism. Each was frankly experimental and untried. The Curtiss plane smashed up in landing before the race, the Dayton Wright entry quit because of control or stability troubles and the big Packard engine of the Verville Army plane misbehaved. There was no real race, as the only British starter quit with a broken oil pump and two French entries also had oil troubles.

THE PULITZER RACE

The Pulitzer Race was really a race, with 37 planes to start and 24 to finish. Again, it was demonstrated that experimental planes and engines have small chance to keep up a long grind at full power. True, the Verville Packard won the race, but the engine had to be run at less than 500 b.h.p. instead of its rated 600 b.h.p., and finished but two and one-half minutes ahead of the Thomas-Morse which had but 320 h.p. The experimental engines in the Curtiss-Kirkham triplanes both failed. Both Loenings failed because of cooling system troubles, known to exist in the type and thought to be taken care of. In all there were 13 unlucky planes which failed to finish.

It appears that only one plane quit because of a defect in the airplane proper, while ten had power plant trouble. Two contestants were disqualified for reasons of piloting and have no bearing in a technical discussion.

Of the ten planes in power plant trouble, only two broke a main engine part: a Liberty and a Curtiss-Kirkham engine. The rest were forced to abandon the race because of defects in engine accessories, cooling, ignition, oiling, etc. It is discouraging to have the lesson repeated time and time again that it is the accessories that let the plane down.

However, there was not one single propeller failure or gasoline fire, no case of loss of control, no burst wing fabric, and best of all nobody was hurt. This is certainly encouraging and no such record could have been expected two years ago.