This article first appeared in Practical Engineering 1940 Vol1 No5. The information that is contained within the article is accurate as of 1940. This article describes new technological developments in Aeronautical Engineering at the time.
One of the most significant indications of the progress anticipated in the development of aircraft engines within the next few years, was the announcement recently by Guy W. Vaughan, president of the Curtiss-Wright Corporation, that the Wright Aeronautical Corporation is preparing for the production testing of power plants of twice the output of the Wright Double-Row Cyclone whose rating of 1,500 h.p. is the highest ever accorded an aircraft engine of any type by the U.S. Civil Aeronautics Authority.
These preparations for the future quantity production of high-powered aircraft engines, Mr. Vaughan disclosed, consist of the building of a battery of 14 test cells in which engines up to 3,000 h.p. may be mounted for the 10 hours of operation, under their own power, which all Wright engines must complete before delivery to the aircraft manufacturer for military service. Four of the new test cells, Mr. Vaughan said, are already in use, while others will be placed in operation as rapidly as they are built.
Mr. Vaughan pointed out that the new equipment will be used solely for the purpose of carrying out the final tests on engines being built on a production basis and not for experimental development.
“The trend in aircraft engines is unswervingly toward single units of higher power to meet the demands created by the larger aircraft projected," Mr. Vaughan said. "Aircraft manufacturers already have designs of ships whose size would dwarf any aircraft now in operation or actually being built. While there are many other problems to be solved before these planes become a reality, one of the principal deterrents to the execution of the designs is the lack of single engines of sufficiently high output to enable the plane manufacturer to obtain the total power required without resorting to the use of a larger number of power plants than is deemed practical.
"During the past 1-0 years we have doubled the output of the nine-cylinder radial air-cooled engine, and by building similar engines with 14 cylinders arranged in two rows, have produced power plants three times as powerful as those of a decade ago.”
"In 1929 anyone who had ventured the belief that the radial air-cooled engine could be satisfactorily produced in units of more than 600 to 650 h.p. would have been regarded as an extreme optimist", to say the least. Today we have in production the 1,500 h.p. Wright Double-Row Cyclone which has been selected to power the Boeing 314 flying-boat, the Curtiss-Wright CW-20 transport and the new Martin patrol boats for the U.S. Navy.
"Exactly what the future will bring in the line of higher powers I am not now in a position to state. However, last year the Wright Company completed a $250,000 experimental testing laboratory which will provide for the endurance proof-testing of engines of 3,000 h.p., swinging flight propellers up to 20ft. in diameter. That we are preparing to-day for the testing of production engines of similar capacity should be significant at least of our confidence that more powerful engines will be built."
The fact that they are stressed for 3,000 h.p. engines is only one of the features of the new production testing equipment which Mr. Vaughan described as the most modern in existence. Of particular interest are the provisions made in the new test cells for the reproduction of conditions which are encountered in flight. A blower connected to the carburettor air intake by a duct enables test engineers to simulate the "ramming" effect of air entering the carburettor at 200 miles an hour as in a modern airliner. This blower is also equipped with controls by means of which the air fed to the carburettor may be "thinned" out to simulate flight at high altitudes and heated or cooled to reproduce changes in temperature.
The test cells are built in pairs separated by a control room on each side of which are tables and panels. On these are mounted the throttles and the various instruments with which the engines are checked for power output, fuel and oil consumption, cooling and other functions during the test runs. A clear-glass window above the instrument board gives the test observer an unobstructed view of the test cell and the engine. The control rooms are kept free from exhaust gases and other fumes by special air-conditioning equipment.
Soundproofed to a greater extent than most modern airliners, the new cells could be operated on a 24-hour-a-day basis without disturbing residents in the vicinity of the Wright factory.. Even with an engine operating at full throttle, the noise level outside of the testing building is no greater than from a mill or ordinary manufacturing plant. In the control rooms, a telephone conversation may be carried on in normal tones without difficulty.
Mounting The Engine
A new method employed in mounting the engine in the test stand closely approximates the actual installation in the aeroplane. In place of the conventional framework of structural steel bolted to the floor, a steel tube is used.
This tube is suspended from the ceiling by four cables and anchored to the floor by two more. Cradled in rubber, these cables provide a flexibility in the engine mount which could not be obtained with a rigid test stand.
Two towers, one at each end of the test cell, provide for a free circulation of air.
Drawn in through the forward tower by the propeller, the air passes over the engine and is discharged to the atmosphere at the rear. In these towers, which extend over 30 feet above the ground, is concentrated most of the soundproofing material which dampens out the engine's roar. A monorail track extending from the front of the test cell, which opens on to a corridor leading from the assembly department, enables mechanics to lift engines from their assembly stands by means of a sling and guide them to the engine mount. This facilitates attachment and removal of the engine from the stand.