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FLIGHT, July 6, 1939.

The rear section of the fuselage,looking toward the tail turret, with thechute for the reconnaissance flarefprotuding on ihe left amidships.the M ark I Wellingto n is a two-speed supercharged unit with the following ra t ing s : Take -of f pow er ,965 h. p. a t 2,475 r .p .m . ; intern a t io n a l p o w er ( us in g m e d i u msupercha rge ) , 780/815 h .p . a t 2 ,250r .p .m . a t 4,750ft . ; intern ation alpower (using full supercharge) , 720/750 h.p. a t 2,250 r .p.m. a t 14,750ft . ;ma x imu m p o w e r ( me d iu m s u p e r charge) , 1,000 h.p. a t 2,600 r .p.m.at 3,000ft. ; ma xim um power ( fullsupe rcha rge ) , 885 h .p . a t 2 ,600 r .p .m.at 15,500ft.

The Wel l ing ton ' s eng ines dr ive DeHavi l land th ree -b laded cons tan t -speed a irscrews with a diameter of12ft . 6in. Th ey are carr ied on mo untings bolted to the f ireproof bulk headframes, the insta l la t ion being designedto a l low quick replacement of a poweruni t . In addi t ion to the usua lBristol long-chord gil led cowling withtra i l ing-edge cooling gil ls , the enginesare p rovide d w ith lo uvred ' ' dish-pan " cow lings over the c rankca ses.The exhaus t on the por t eng ineheats a boiler , the steam from whichpasses through a heater in the wingroot; a ir warmed in the heater f lowsinto a fore-and-af t duct running pract ica lly the whole length of thefuselage.

Each engine has i ts own fuelsys tem , handl ing 500 ga l lons mad e upas follows: One main tank in enginenacelles (60 gal .) ; three wing tanks infront of spar in oute r wing pa nel (138 gal .) ; thre e wingt a n k s b e h in d o u t e r s p a r (1 62 g a l . ) , a n d o n e "o v e r l o a d "t a n k i n t h e b o mb c o m p a r tme n t . T h e t a n k s ar e ma d e ofAlclad, the over load tanks being cylindr ical in shape andsecured in the bom b bay s by strap s. All fuel is availab leto e i ther engine if required.Wh en the Wel l ing ton i s mak ing shor t - o r me dium-rang eThis aerial photograph gives a good idea of the Wellington 's external appearance. It also shows the excellentprovision for adm itting daylight. ^

f l ights the engines draw oil f rom tanks in the nacelles,bu t fo r long- range work an addi t iona l tank wi th a pumpis f it ted on the starbo ard side of the cabin. Ap art f roma thermosta tica lly controlled Serck oil cooler and aTecalemit oil c leaner for the main oil system, there is anaddit ional Tecalemit c leaner for the two-speed blowers y s t e m.The " hy dra u l i c s " a re of in te re s t in tha t the re a re twosepa rate syste ms . Of these the pr im ary c ircuit suppliesth e unde rcarr iage and ta i l wheel, , th e f laps, and th emechanism for ope ra t ing the bom b doors , while the o the r