This weekly report details technical activities for the week ending May 15, 1943.

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The two-dimensional, incompressible potential flow past a lattice of airfoils of arbitrary shape is investigated theoretically. The problem is treated by usual methods of conformal mapping in several stages, one stage corresponding to the mapping of the framework of the arbitrary line lattice and another significant stage corresponding to the Theodorsen method for the mapping of the arbitrary single wing profile into a circle. A particular feature in the theoretical treatment is the special handling of the regions at an infinite distance in front of and behind the lattice. Expressions are given for evaluation of the velocity and pressure distribution at the airfoil boundary. An illustrative numerical example is included.

"An analysis is made of the stability of an airplane with ailerons free, with particular attention to the motions when the ailerons have a tendency to float against the wind. The present analysis supersedes the aileron investigation contained in NACA Technical Report no. 709. The equations of motion are first written to include yawing and sideslipping, and it is demonstrated that the principal effects of freeing the ailerons can be determined without regard to these motions" (p. 255).

The following memorandum discusses experiments and methods to recover uranium from Colorado-Utah sandstone and leaving the vanadium in the tails, improving filterability.

"In this report are presented three figures which show how the relative activities (expressed as percentages of total activity) of the individual fission elements (produced by neutron bombardment of uranyl nitrate) vary with cooling time."

Report presenting stability, maximum lift, and high-speed tests of an observation airplane fitted with Maxwell leading-edge slots. The static and dynamic longitudinal and lateral stability was generally satisfactory and not affected much by the slots.