Page:Dictionary of aviation.djvu/146

 122 DICTIONARY OF AVIATION

sities communicating at their bases; also, the pressure of a confined volume of gas upon a unit of the interior surface of the confining vessel.

head-area 'hed,e:-<d-9 n. [also spelt hedtarea} the area of the hed (or part in front of the shoulder) of an aerofoil or airship; the area of a surface which offers hed^resist- ance.

equivalent headtarea, a hed^area or area of hed which is equivalent to the aggregate of the hed^areas of all the parts of an airship considerd separately; the sum of the hed# areas of any airsmachine.

head-breeze 'hed,bziiz n. [also spelt hedtbreeze] a breeze or light wind blowing directly against the hed or forespart of an airship; a breeze coming from the front.

header 'hed9z n. [also spelt heder] a fall hed^first or en the hed, as of a bird, compare cropper.

headless 'hed-tes adj. [also spelt hedless"] having no hed; destitute, or nearly destitute, of hed^piece or front project- ing portion : as, the Wright *hedless biplane.

head-piece 'hed,piis n. [also spelt headpiece, hedfpiece] the piece or part which forms the hed or front projecting portion of an aeroplane flying^machine : the epposit of tail- piece.

head-resistance 'hed-zi,zistns n. [also spelt head resistance, hedzresistance] the resistance which the hed, hull, bedy, frame, or car of a balloon, airship, or flyer, considerd apart from the spars, rigging, and sustaining^surfaces, of- fers to the air, in flight; the hullsresistance ; the bedy ^resist- ance, compare drift.

headway 'hed/wee n. [also spelt hedway] the motion (of an airship) ahed or forward ; rate of progress : as, initial *hed- way; to make *hedway against the wind.

head-wind 'hed/wind n. [also spelt hedtwind] a wind blow- ing directly against the hed or forepart of an airship; a wind coming from in front.

heat hiit n. the form of energy concomitant with the sensa- tion felt when near fire, etc.

latent heat of precipitation, that part of the latent heat of evaporation which is set free when the vapor is precipi- tated or condenst in the form of water or cloud.

heat-haze 'hiit,heez n. a hazy condition of the air in hot wether; haze.

heat-lightning 'hiit^ait-nirj n. [also spelt heat lightning] sheet lightning, occurring in het wether as a result of a sterm so distant that the thunder is inaudible; summer* lightning.

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