Understanding the Start Process of Large Piston-Engined Aircraft
Have you ever wondered how large piston-engined aircraft start without the need for a starter motor or batteries to spin the pistons? This article delves into the fascinating history and methods used to start these powerful engines. From electric starters to cartridge starters, we explore the different techniques and technologies that have been employed over the decades.
Electric Starters: A Common Method
One of the most common methods to start a piston-engined aircraft is through the use of an electric starter. This system relies on a robust electric motor that spins the crankshaft, which in turn drives the pistons. As of now, a 24-volt starter is often used, especially in aircraft like the Pratt and Whitney 4360 28-cylinder engine. While older aircraft may have used a variety of start methods, the modern electric starter is reliable and efficient, making it the preferred choice for many pilots.
Historical Methods for Starting Aircraft Engines
Historically, there were several methods to start aircraft engines, often depending on the aircraft and its year of manufacture. For instance, many piston engines now use an electric motor to start the engine, but in the 1930s and 1940s, aircraft used more unconventional methods.
The Coffman Starter System
The Coffman starter was a popular choice in the aviation industry, especially during World War II. This system utilized a large, shotgun-like cartridge filled with cordite, a form of pyrotechnic gunpowder. When the cartridge was fired, it provided the initial impulse to turn the engine over. Interestingly, this method was also used for some early jet fighters, such as the De Havilland Vampire, where a single cartridge was sufficient for one attempted engine start.
Cartridge Starters: A Consistent Supply
Some aircraft, including the B-24 Liberator, had a built-in auxiliary power unit (APU) in the form of a small petrol engine. This motor would be started first to help the batteries get the aircraft engine running. This early APU concept would later evolve into more advanced systems. Cartridge starters required a consistent supply of cartridges, and thus, a good stockpile was kept on board to ensure reliable starts in challenging conditions. Aircraft like the Spitfire, Hurricane, and Mustang often required the pilot to turn a starting handle vigorously for several minutes to spin a flywheel to high speed before engaging the engine's clutch.
Inertial Starters: The German Approach
During World War II, the Germans favored a different method of starting their engines: inertial starters. These systems involved a ground tech manually cranking a small flywheel, which the pilot then used to start the engine. This method was labor-intensive and required coordination between the ground crew and the pilot. Although not as commonly used as cartridge starters, it was an effective method in specific contexts.
The Hucks Starter: A Historic Solution
Another interesting method was the Hucks starter, invented by RFC Captain Bentfield Hucks in the early 1920s. This system utilized a chain and sprocket system connected to a Model T's engine via a clutch. The Model T's engine turned an "A" frame mounted countershaft, which was connected to the aircraft's propeller via a special nut. Versions of the Hucks starter were widely used up to and including World War II, demonstrating its reliability and adaptability.
Manual Starting: Early and Inefficient
For smaller engines, starting was often done manually. The pilot would turn the starting handle, either directly on the engine or via a gear or chain reduction system. Larger engines required a more vigorous approach. A handle would be turned frantically for several minutes to spin a flywheel to high speed. The pilot would then engage a clutch to connect the rotating flywheel to the crankshaft via reduction gearing. This method, while effective, was labor-intensive and required a precise sequence of actions to be successful.
Modern Advances in Starting Systems
While manual and cartridge starters were prevalent in the early days of aviation, modern aircraft engines rely on more sophisticated, electrically powered starters. These systems are safer, more reliable, and easier to maintain. However, legacy aircraft and those outside of mainstream operations may still use some of these historical methods to ensure reliability and safety.
Conclusion
The process of starting a large piston-engined aircraft is both complex and fascinating. From the modern electric starters to the historical methods like the Coffman starter and the Hucks starter, there is a wide array of techniques that have been developed and refined over the years. Understanding these methods not only provides insight into the evolution of aviation technology but also highlights the innovative solutions that have kept aircraft engines running across different eras.