This document summarizes recent (First quarter 1925) research and development activities relevant to the Air Service. Article listing: Aircraft development: Airplanes: 'XO' observation airplane competition; New Curtiss observation XO-1; Boeing and Curtiss pursuits in combat; Production amphibian on performance test--Polar flight; Bids received for heavy bomber; Curtiss XNBS-4 makes favorable showing--Description of first article; First ambulance airplane received (XA-1); New training types received, Models AT-1 and PT-1; Water spray tests on propeller tipping; Effects of gunfire on Dural propeller; Fuselage effect on propeller efficiency (T-3 transport); Airships and balloons: Highly mobile balloon winch including history of balloon winches; Erection of RS-1 airship delayed; Armament: Tests on tracer ammunition for aircraft use; Aircraft gunnery target; Gliding bombs; Equipment: Accelerometers for impact tests; New aircraft storage batteries under development; Luminosity of instrument dials improved; Developing time for T-1 film shortened; Flash powder for night aerial photography; New single-lens cameras, Models K-7 and K8; Five-lens camera proposed for aerial mapping; Night triangulation with searchlight beams; Power plants: Almen 'Barrel' engine, Model A-4; The experimental 'Cam' engine; New Curtiss V-1400 engine passes endurance test; More Packard engines ordered; Research and experiment: Resume of Engineering Division serial reports: Airplane section: Structural members under combined axial and transverse loads--Serial no. 2400. Section II; Study of French S.T. Ae formula for load factors--Serial no. 2441; Method of computing horsepower available for performance prediction--Serial no. 2443; Loadings for experimental wing spars--Serial no. 2450; Flow of air around rotating cylinder--Serial no. 2462; Predicting cruising range of proposed airplane--Serial no. 2464; Large capacity skis--Serial no. 2474; Torsional test of Curtiss XNBS-4 fuselage--Serial no. 2476; Torsional test of Curtiss (Martin) NBS-1 bomber--Serial no. 2479; Static tests conducted at the Engineering Division; Wind tunnel tests; Armament section: Experimentation on bombardment cannon for airplanes--Serial no. 2329; Remedies for machine gun malfunctions--Serial no. 2442; Equipment section: Porosity of parachute fabrics--Serial no. 2429; 'Tasco' distant-reading gasoline gauge--Serial no. 2480; Flying section: Take-off and landing characteristics of an airplane--Serial no. 2375; Control stick force indicator--Serial no. 2385; Carbon-coated paper for recording instruments--Serial no. 2409; Performance tests; Material section: Heat treatment of Al-Cu-Fe-Mg (piston) alloy--Serial no. 2439; Airplance wheel and tire, size 64x14--Serial no. 2444; Comparison of re-heated piston alloys at room temperature--Serial no. 2452; Al-Cu-Si alloy as sand-cast and as heat-treated--Serial no. 2457; Power plant section: Power plant laboratory standard test methods and computations--Serial no. 2343 revised; The airplane and the future--Serial no. 2387; Performance and carburetor data on Packard 1A-1500 engine--Serial no. 2414; Fifty-hour endurance test of inverted Liberty--Serial no. 2423; Lonergan radiator--Serial no. 2424; Test of Stromberg caburetors on Curtiss D-12 engine--Serial no. 2426; Carburetion of Wright T-3 engine with Stromberg NA-U6T carburetors--Serial no. 2446; Magnesium alloys as bearing materials--Serial no. 2447; Bearing loads for proposed 1200-h.p. aircraft engine--Serial no. 2448; Instructions for re-enforcing Liberty cylinders--Serial no. 2456; Preliminary performance of Packard 1A-1500 engine--Serial no. 2460; Wright 'E' engine performance with Stromberg NA-U5 and NA-D4 carburetors--Serial no. 2466; Investigation of materials: Balanced balloon fabric; Processed castor oil; Piston alloys; Reverse bending machine; Straight-side airplane tire and wheel development; New books and documents--Data on aeronautical development in United States and foreign countries added to technical files of the Engineering Division, U.S. Army Air Service--Documentary data on international aeronautics: Britain; Czecho-Slovakia; France; Germany; Italy; Sweden; United States; Aerial navigation: Airways and airdromes; Aids to navigation; Meteorology; Competitions and records; Instruction: [General]; Air Service Engineering School; Research; Aircraft--Heavier-than-air: [General]; Blackburn; Bothezat; Bristol; Cierva; DeHaviland; Farman; Ferbois; Hanriot; Heinkel; Liore-Oliver; MB-3A; NB-1; Parnell; Potez; SC-2; Schneider; S.E.C.M.; Straisand Strella and Akrona; Aircraft--Lighter-than-air: [General]; ZR-3; Equipment; Fuels and lubricants; Materials: [General]; Aluminum and its alloys; Dopes, paints, varnishes, etc.; Fabric; Glass; Magnesium; Platinum; Radiator compound and its anti-freeze; Steel; Wood; Foundry methods and tests; Parachutes; Photography; Propellers; Power plants: [General]; Breguet; Curtiss; Farman; Gnome; Hispano-Suiza; Odier; Packard; Panhard; Renault; Siddeley; Wright; Accessories; Radio; New books on aeronautics and allied subjects--Accession of books to Engineering Division technical library during 1924.