An inve tigation was conducted in the B.J..O.J.. 20- foot wind tunnel to determine the drag, the propulsive and net. efficieno1ea 1 and the coolinc characteristics of several scala-model arranementa of air-cooled radial-ancine nacelles and preaent-dar propellers in front of an 18- percent-thick, 5- br 15-foot airfoil. Investigations of like arranementa aimulatin the eometric proportions of airplanes in the 20,000-pound wei ht classification have been conductod br the N.J..C.A. and the results are summarized in previous reports. This report deals with an inveati ation of winc4nacelle arrangements simulating the geometric proportions of airplanoa in the 40,000- to 70,000- pound woiht classification and havinc the nacelloa looatod ln tho vicinitr of the optimum location determined from the earlier testa. Two 3-bla.de propellers with diamotera of 36 and 48 inches, reapectivelr, wore oach tested in conjunction with a 12-inoh-diamoter nacelle in three positions in front of the win and with a 16-inch-diameter nacelle in aiz poai tiona in front of the wing. Lift, dra. coolinc-air flo, and propeller characteristics wore determined for each of the arrnncementa. Comparisons on the basis of net effi aienor between the various arranementa indicated that, for h1ch-apeed and cruis1nc conditions, the moat-favorable location for a tractor nacelle-propeller arrancement of the trpe tested wna with the thruat azia on the win center line and with the propeller between 15 and 30 percent of the chord forward of the leadinc edgo of the wine. The ioaa in not effioionor throuh tho uae of either laresdiameter encinea or nacelle installation hnvin a hich lnterferonce drac is cloarlr indicated. In certain caaoa, the.action of the propeller slipstream on tho flow pnttern over the wine-nacelle arrangement mar be such as croatlr to influence the cooling qualities of a ivon wine-nacelle-propeller arrangement.