176 DICTIONARY OF AVIATION
ferm density equal to that of the air at the point where the pressure is mesured; the height of a homogeneous atmos- fere.
pressure-plate 'pse$az,p3Leet n. a plate used in ascertain- ing the pressure of the wind.
pressure-reaction 'p5e$3-zi,aek$9n n. the reaction of a moving aeroplane to the pressure of the atmosfere acting against it.
pressure-region 'pse$3z,zii-d39n n. a region of air-pressure, as against the under or the upper surface of a moving aero- foil.
pressure-value 'p5e$9z,vseliu n. the value or numerical amount of the pressure of a fluid, as air upon an aerofoil.
primaried 'psai-ma-zid adj. furnisht with primaries or pri- mary fethers : as, nine-*primaried.
primary 'psai-ma-zi n. one of the wing-fethers seated upon the manus or hand of a bird.
prob pseb n,
old prob, the chief of the wether-bureau ; the wetherx prefet.
projector pso'dsektaz n. an apparatus for projecting or throwing a beam of light, eften consisting essentially of a parabolic mirror.
pronation pso'nee-$3n n. the act or result of pronating; the prone position of the forearm in which the bones of ,he forearm are more or less crest and the palm of the hand turnd downward : the epposit of supination.
propellant pso'petent n. an agent or force that propels; a propelling-agent.
propeller pso'petez n. any device for propelling, driving for- ward, or imparting t^anslatory motion; a contrivance such as an oar, a paddle-wheel, or especially a screw, actuated by a motor and used for the propulsion of an airship; a screw propeller.
collapsible propeller, a propeller so made as to be capable of being collapst or folded up.
curved propeller, a propeller the cress-section of whose blades, in a plane passing thru the shaft, is curvd; a pro- peller the surface of the rotation of whose blades is curvd.
dihedral propeller, a propeller whose blades ferm a di- hedral angle with each other.
fan propeller, same meaning as fanzpropcller. flexible propeller, a propeller which is made of flexible material mounted on a frame; a nen-rigid propeller; a col- lapsible propeller.
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