The Aeroplane Speaks | Page 4

horizontal component, sometimes, though rather erroneously, called Head Resistance; he's a villain of the deepest dye, and must be overcome before flight can be secured.''
``And I,'' said the Propeller, ``I screw through the air and produce the Thrust. I thrust the Aeroplane through the air and overcome the Drift; and the Lift increases with the Speed and when it equals the Gravity of Weight, then--there you are--Flight! And nothing mysterious about it at all.''
``I hope you'll excuse me interrupting,'' said a very beautiful young lady, ``my name is Efficiency, and, while no doubt, all you have said is quite true, and that, as my young man the Designer says, `You can make a tea-tray fly if you slap on Power enough,' I can assure you that I'm not to be won quite so easily.''
``Well,'' eagerly replied the Lift and the Thrust, ``let's be friends. Do tell us what we can do to help you to overcome Gravity and Drift with the least possible Power. That obviously seems the game to play, for more Power means heavier engines, and that in a way plays into the hands of our enemy, Gravity, besides necessitating a larger Surface or Angle to lift the Weight, and that increases the Drift.''
``Very well,'' from Efficiency, ``I'll do my best, though I'm so shy, and I've just had such a bad time at the Factory, and I'm terribly afraid you'll find it awefully dry.''
``Buck up, old dear!'' This from several new-comers, who had just appeared. ``We'll help you,'' and one of them, so lean and long that he took up the whole height of the lecture room, introduced himself.
``I'm the High Aspect Ratio,'' he said, ``and what we have got to do to help this young lady is to improve the proportion of Lift to Drift. The more Lift we can get for a certain area of Surface, the greater the Weight the latter can carry; and the less the Drift, then the less Thrust and Power required to overcome it. Now it is a fact that, if the Surface is shaped to have the greatest possible span, i.e., distance from wing-tip to wing-tip, it then engages more air and produces both a maximum Reaction and a better proportion of Lift to Drift.
``That being so, we can then well afford to lose a little Reaction by reducing the Angle of Incidence to a degree giving a still better proportion of Lift to Drift than would otherwise be the case; for you must understand that the Lift-Drift Ratio depends very much upon the size of the Angle of Incidence, which should be as small as possible within certain limits. So what I say is, make the surface of Infinite Span with no width or chord, as they call it. That's all I require, I assure you, to make me quite perfect and of infinite service to Miss Efficiency.''
``That's not practical politics,'' said the Surface. ``The way you talk one would think you were drawing L400 a year at Westminster, and working up a reputation as an Aeronautical Expert. I must have some depth and chord to take my Spars and Ribs, and again, I must have a certain chord to make it possible for my Camber (that's curvature) to be just right for the Angle of Incidence. If that's not right the air won't get a nice uniform compression and downward acceleration from my underside, and the rarefied `suction' area over the top of me will not be as even and clean in effect as it might be. That would spoil the Lift-Drift Ratio more than you can help it. Just thrust that chalk along, will you? and the Blackboard will show you what I mean.''
``Well,'' said the Aspect Ratio, ``have it your own way, though I'm sorry to see a pretty young lady like Efficiency compromised so early in the game.''
``Look here,'' exclaimed a number of Struts, ``we have got a brilliant idea for improving the Aspect Ratio,'' and with that they hopped up on to the Spars. ``Now,'' excitedly, ``place another Surface on top of us. Now do you see? There is double the Surface, and that being so, the proportion of Weight to Surface area is halved. That's less burden of work for the Surface, and so the Spars need not be so strong and so deep, which results in not so thick a Surface. That means the Chord can be proportionately decreased without adversely affecting the Camber. With the Chord decreased, the Span becomes relatively greater, and so produces a splendid Aspect Ratio, and an excellent proportion of Lift to Drift.''
``I don't deny that they have rather got me there,'' said the Drift, ``but all the same, don't forget my increase due to the drift of the Struts and their bracing wires.''
``Yes, I dare