Like a horse operating a treadmill, an airplane engine mounted on a special turntable does a hard day’s work but goes nowhere. The turntable in reality is a testing laboratory, and the engine does more to increase engineering knowledge than any on flying duty. Since it is on the takeoff that engines are speeded to full horsepower and undergo the greatest strains, tests that simulate takeoff conditions are among the most important. Although normal takeoffs occur into the wind, airplanes frequently must take off in a cross wind. In the latter case a difference in pressure is created between the two sides of a radial engine, with the result that some cylinders get hotter than others. The merry-go-round laboratory at the Boeing Aircraft plant in Seattle, Wash., permits the engine to be turned as desired in order to check oil cooling, fuel flow, exhaust back pressures, vibration of engine and propeller, propeller clearances and dispersion of the heat generated in the cylinders. The tests can be run at cruising speeds to learn what may be expected in the air. The “test pilot” and crew are housed in a soundproof cabin on the turntable, equipped with instruments to measure pressures at many points and cameras for recording all instrument readings at one time.