Memorandum presenting investigation on reductions of friction on wings, especially by means of boundary-layer suction. The report is broken up into several sections, including: causes of transition, laminar profiles with the transition taking place, laminar boundary-layer suction, investigation of the laminar pressure increase, investigation of the slot flow for laminar boundary-layer suction with single slots, tests about keeping a boundary layer for high Reynolds laminar with the aid of boundary-layer suction, and an investigation of a slightly-cambered laminar suction profile of 10.5-percent thickness.

A table is presented which includes data for calculating the index of efficiency. The author uses this data to conclude that seaplanes cannot be considered inferior to terrestrial airplanes.

The author discusses various aspects of landing aircraft such as the actual process of touchdown and the problems associated with the tail skid touching the ground before the landing gear.

A simplified formula for calculating wing spars is presented.

The author presents a comparison and combination of the numerical and geometrical determinations of the maximum M, when calculating the maximum bay moment.

"It is profitable to examine the organization and equipment of the German airship stations. The stations best adapted for serving as the basis of this study were chiefly constructed by the German Navy, during the war, for exclusively military purposes and do not therefore entirely satisfy the conditions of exploitation required for a civilian air service. The requisite modifications for satisfying the latter conditions may nevertheless be readily determined according to circumstances" (p. 1).

This report presents experiments and calculations for the purpose of determining the landing gear requirements upon the water. Moving pictures are given which furnish data and also may give both the magnitude and direction of the forces acting. Different classes of seaplanes are examined and proposals for calculation instructions are given.

Results are presented for the moments and position of force centers of a series of cambered round bodies derived from a torpedo-like body of revolution. The effects of placing fins on the rear of the body of revolution are also included.

Report presenting some topics related to safety in flight and the importance of having accurate statistics and information regarding aircraft problems and accidents. Some of the topics provided included perverted statistics, the British accident record, unregulated air traffic in America, and air mail in bad weather.

The difference between aircraft for commercial and wartime uses is delineated, but the interchangability between the two is also discussed. Airships in both roles are also presented.

The development of the parachute is presented as well as the future possibilities. The primary topics covered include allowing for wind in design, the parachutes used at balloon exhibitions, parachute use in the war, the delayed-opening type of parachute, and the use of parachutes on commercial airplanes.

This report presents a study of an instrument that can warn the pilot of the turning of his airplane. This instrument must satisfy three conditions: 1) It must give useful indication immediately from take-off; 2) The indications must be instantaneous and require no exertion by the pilot; 3) The indicator must be sensitive only to changes of orientation in the horizontal plane. Different solutions are presented such as a gyroscope driven by the suction of a Venturi tube.

"A transverse test was made of the wood sample using a 5,000 pound Olsen testing machine, the deflection under load being measured by means of a Wissler dial. The results of the transverse test are given and the stress-strain curve is attached" (p. 1).

Different aspects of aircraft regulation are discussed such as: protecting the public; the restriction of flights over crowds; regulations of wing-walkers.

This report presents examples of different methods of comparing aircraft mathematically. In the example given a biplane and monoplane are compared as to what speed one type of airplane is better at than another.

"The Coutinho-Sacadura course corrector is an instrument with which, knowing the angles of drift of two different courses, we may determine by simple readings: a) direction and velocity of wind; b) correction to be made in course followed by compass, in order to fly in a given direction; c) ground-speed of aircraft, the resultant of its air speed and the velocity of the wind" (p. 1).

Different illumination systems for landing fields are presented which include fixed beacons, signal guns, and light patterns such as T's and crosses. Some of the advantages and disadvantages for each of the lighting patterns are provided.

The wing strain meter enables a pilot to know the strain on lifting surfaces and to warn him of the safe limits which may not be exceeded. In wing strain the most important factors are the force of gravity and the force of lift which gives the measure of the sustaining force, and their components which are perpendicular to the lifting surfaces. This reports methods for using the wing strain meter.

The first part of this report shows the differences between commercial and war airships and then goes on to show how some of the problems were solved. Their thorough investigations of these problems finally enabled the Schutte-Lanz Company to construct bulkhead diagrams for determining the buoyancy of airships, by means of which the size of each cell was established. These diagrams were derived from bulkhead diagrams employed in ship designing and are used in a similar manner.

The problems as to how an airship can best be stabilized and steered and to what stresses it is subjected in the air, are so important as to determine in large measure the future development of airships much more than formerly when velocities of 30-35 meters (98-115 feet) per second were not known and the effects of the air flow were not so great.

"In opposition to the advantage of larger dimensions, there is one disadvantage, namely, the weight of the structure increases more rapidly than the buoyancy. It is not possible, however, to determine a general law. In order to formulate one having the merit of simplicity, we will divide the structure into two parts: one subject to tensile and compressive stresses, varying directly as the ascensional or lifting forces; the other subject to varying stresses of the surface areas" (p. 1).

The results of wind tunnel tests for the determination of the effect of a jet on the lift and downwash of a wing are presented in this report. In the first part, a jet without rotation and with constant velocity distribution is considered - the jet being produced by a specially designed fan. Three-component, pressure distribution, and downwash measurements were made and the results compared with existing theory. The effect of a propeller slipstream was investigated in the second part. In the two cases the jet axis coincided with the undisturbed wind direction. In the third part the effect of the inclination of the propeller axis to the wing chord was considered, the results being obtained for a model wing with running propeller.

"In order to carry out the contemplated study, it was first necessary to provide hot spots in the combustion chamber, which could be measured and whose temperature could be changed. It seemed difficult to realize both conditions working solely on the temperature of the cooling water in a way so as to produce hot spots on the cylinder wall capable of provoking autoignition. Moreover, in the majority of practical cases, autoignition is produced by the spark plug, one of the least cooled parts in the engine. The first procedure therefore did not resemble that which most generally occurs in actual engine operation" (p. 1).

"The concept of the adhesive power of a tire with respect to the road involves several properties which result from the purpose of the tire; namely, connecting link between vehicle and road: (1) The tire must transfer the tractive and braking forces acting in the direction of travel (tractive and braking adhesion); (2) The tire is to prevent lateral deviations of the vehicle from the desired direction of travel (track adhesion)" (p. 1).