Report discussing tests of 2-blade, adjustable-pitch, counterrotating tandem model propellers, adjusted to absorb equal power at maximum efficiency. The characteristics at several pitch settings and diameter spacings were compared with 2-blade and 4-blade propellers. Tandem propellers were found to have an advantage over single propellers at higher pitch settings.

Report discusses the important principles involved in the operation of a baffle for an engine cylinder and how using a correctly designed baffle can improve cooling. The baffle-exit radius and width and exit-duct length were found to be the most important parts of the baffle and a baffle that gave a relatively uniform temperature distribution was designed.

In many installations of castering rubber-tired wheels there is a tendency for the wheel to oscillate violently about the spindle axis. This phenomenon, popularly called 'shimmy,' has occurred in some airplane tail wheels and has been corrected in two ways: first by the application of friction in the spindles of the tail wheels; and, second, by locking the wheels while taxiing at high speeds. Shimmy is common with the large wheels used as nose wheels in tricycle landing gears and, since it is impossible to lock the wheels, friction in the nose-wheel spindle has been the sole means of correction.

At the request of the Materiel Division of the Army Air Corps, seven tapered wings having sections based on the N.A,C.A. 230 mean line were tested in the variable-density wind tunnel, The characteristics of the wings are given.

"In connection with the application of stable tricycle-type landing gears to transport airplanes, the question arises as to whether certain passengers may not experience relatively great accelerations in an emergency landing. Since the main landing wheels are behind the center of gravity in this type of gear, a hard-braked landing will cause immediate nosing down of the airplane and, when this motion is stopped due to the front wheel striking the ground, there will be some tendency for the rearmost passengers to be thrown out of their seats, The provided rough calculations are designed to show the magnitudes of the various reactions experienced in a severe landing under these circumstances" (p. 1).

The effects of the geometrical arrangement of tricycle landing gears on various characteristics of an airplane equipped with such landing gear is discussed. The characteristics discussed include directional stability, overturning tendencies, steering and ground handling, shimmy, takeoff, and porpoising. The conclusions are summarized in a table.

"An investigation was undertaken to determine the character and importance of the transition phase between the ground run and steady climb in the takeoff of an airplane and the effects of various factors on this phase and on the airborne part of the takeoff as a whole. The information was obtained from a series of step-by-step integrations, which defined the motion of the airplane during the transition and which were based on data derived from actual takeoff tests of a Verville AT airplane. Both normal and zoom takeoffs under several loading and takeoff speed conditions were considered" (p. 1).

"Various transparent organic plastics, including both commercially available and experimental materials, have been examined to determine their suitability for use as flexible windshields on aircraft, The properties which have been studied include light transmission, haziness, distortion, resistance to weathering, scratch and indentation hardness, impact strength, dimensional stability, resistance to water and various cleaning fluids, bursting strength at normal and low temperatures, and flammability" (p. 1).

This supplement to a NACA study issued in May 1937 entitled "A Study of Transparent Plastics for Use on Aircraft", contains two tables. These tables contain data on bursting strengths of plastics, particularly at low temperatures. Table 1 contains the values reported in a table of the original memorandum, and additional values obtained at approximately 25 C, for three samples of Acrylate resin. The second table contains data obtained for the bursting strength when one surface of the plastic was cooled to approximately -35 C.