"Yes," said the Lateral and Directional Stabilities in one voice, "that's so, and the wash-out helps us also, for then the Surfaces towards their Wing-tips have less Drift or 'Head-Resistance,' and consequently the gusts will affect them and us less; but such decreased Angle of Incidence means decreased Lift as well as Drift, and the Designer does not always care to pay the price."
"Well," said the Ailerons, "if it's not done it will mean more work for the Rudder, and that won't please the Pilot."
"Whatever do you mean?" asked Efficiency. "What can the Rudder have to do with you?"
"It's like this," they replied: "when we are deflected downwards we gain a larger Angle of Incidence and also enter an area of compressed air, and so produce more Drift than those of us on the other side of the Aeroplane, which are deflected upwards into an area of rarefied air due to the suction effect (though that term is not academically correct) on the top of the Surface. If there is more Drift, i.e., Resistance, on one side of the Aeroplane than on the other side, then of course it will turn off its course, and if that difference in Drift is serious, as it will very likely be if there is no wash-out, then it will mean a good deal of work for the Rudder in keeping the Aeroplane on its course, besides creating extra Drift in doing so."
"I think, then," said Efficiency, "I should prefer to have that wash-out,[7] and my friend the Designer is so clever at producing strength of construction for light weight, I'm pretty sure he won't mind paying the price in Lift. And now let me see if I can sketch the completed Aeroplane."
"Well, I hope that's all as it should be," she concluded, "for to-morrow the Great Test in the air is due."