CHAPTER XIII – Flying Machines Construction And Operation

This chapter delves into the specific demands for power in airship propulsion, distinguishing markedly from terrestrial vehicles like automobiles in terms of power requirements for a given load. Unlike cars that rest on the stable ground and require relatively less power to move heavy loads at significant speeds, airships, due to the absence of a solid resting platform, necessitate much greater power to maintain both lift and forward motion. An automobile might carry a load weighing 4,000 pounds at speeds up to 50 miles per hour with just a 30-horsepower engine. In stark contrast, a modern flying machine, carrying 1,200 pounds, requires a 50-horsepower engine to achieve the same speed, demonstrating a significantly higher power demand relative to its load.

The key factor in this discrepancy lies in air resistance or wind pressure. When an object moves through the air, it encounters resistance, with the resistance force increasing exponentially with the speed. This phenomenon results in dramatically higher power requirements for airships as their speed increases. A table provided in the text shows how horsepower needs surge dramatically with speed due to wind pressure against the moving object. For instance, moving from 60 to 100 miles per hour doesn’t merely double the power requirement; it increases it eightfold.

Additionally, it’s explained how the engine’s horsepower is allocated, with a portion dedicated to overcoming wind resistance and the remainder for propulsion. The chapter further illustrates how these calculations apply to real-world aviation, using the Curtiss aeroplane as an example, where out of a 50-horsepower engine, 12 horsepower is spent overcoming wind pressure alone.

The chapter also touches on the comparison between birds and aeroplanes in terms of supporting area and horsepower required for flight, indicating that while aeroplanes have made remarkable advances, they require substantially more power for the weight they lift compared to birds.

In terms of design implications, the chapter concludes that a larger supporting area can reduce the power needed for lift but at the expense of increased bulk and potential difficulty in handling. Additionally, the chapter introduces fuel consumption as a critical factor, with increased power demands necessitating higher fuel consumption, setting the stage for further exploration of this challenge in aviation.