Happy National Aviation Day, dear reader! There’s a good chance you’ve not heard of this day, which actually is a federally observed day. As a lifelong aviation fanatic, I refuse to ignore the underappreciated National Aviation Day!
Why August 19?
Because that is the birthday of Orville Wright, born August 19, 1871! He and his brother Wilbur (born April 16, 1867), are the first people to ever make a sustained, controlled, flight of a heavier-than-air-aircraft. This historic occasion, took place at Kitty Hawk, North Carolina, on December 17, 1903. Despite lasting all of 12 seconds, this moment ushered in the age of the airplane, and revolutionized the entire world.
The Reason for the Season
National Aviation Day was established by President Franklin Delano Roosevelt in 1939. In the 36 years since those historic 12 seconds on a beach, aircraft had gone from flimsy wooden and fabric contraptions to metal machines that could fly for thousands of miles at speeds of hundreds of miles an hour.
Creating this holiday made perfect sense for the time. Aviation was new, exciting, and dashing. Celebrity pilots, such as Amelia Earhart, Howard Hughes, and Eddie Rickenbacker captured public imagination. Additionally, developing public support for aviation had a strategic purpose. The United States Army Air Force was deemed to be woefully inadequate early in 1939. FDR and other advisers watched nervously as aircraft proved hugely influential in the Spanish Civil War (1936-1939). Furthermore, Nazi Germany and fascist Italy boasted about their growing air power. A few months before National Aviation Day was declared, FDR ordered the USAAF to increase its strength as war loomed on the horizon.
What are planes made from?
The earliest planes were mostly built with wooden frames and covered in fabric. Engineers experimented with all-metal planes as early as 1920. These early planes were largely built with mild steel. But engineers didn’t like how metal folded and crumpled under stress, which fabric and wood did not. Wood is also lighter than steel, cheaper, easier to work with, and doesn’t rust.
Improved technology in the 1930s created better metal airplanes that used Chromoly steel, but wood remained popular. World War II largely spelled the end of wooden airplanes, but not entirely. A famous example of a successful wooden airplane from WWII is the de Havilland Mosquito. This amazing airplane was one of the exceptions to the the rule. Metal planes, now made from aluminum, were faster, tougher, and could fly higher than wooden ones.
With the dawn of the Jet Age, wood fell out of popularity. More advanced metals like stainless steel, titanium, and magnesium became more common.
Aluminum is the most popular metal in aviation history. Considering that aluminum is strong, light, and resists corrosion, this makes sense. Most modern airplane parts are built from aluminum, 75-80% typically. Even as far back as the 1800s, Count Ferdinand Zeppelin built his famous airships with aluminum. But it wasn’t until the 1930s that aluminum really took off.
Pure aluminum is too soft to be used. Typically, aluminum alloyed with copper is used for aircraft, as the copper gives it significant strength. Therefore, engineers use many different alloys for different components on planes. Alloys 2024 and 7075 excel in structural applications and also typically make the skin of airplanes. 6061 and 3003 regularly make cowls and plating. Finally, the excellent corrosion resistance of 5052 lends itself well to fuel tanks.
Steel also has a long history in aviation. While mild steel fell out of favor in the late 1920s and early 1930s, carbon steels and Chromoly remain popular. Planes built mostly from steel are rare, due to their weight. There are exceptions, such as the popular Beechcraft Staggerwing. In modern times, you see steel in components that require high amounts of stiffness, such as landing gears.
A less common material in aviation, magnesium is still worth mentioning. It has 66% the weight of aluminum and the best strength-to-weight ratio of all aircraft structural metals. However, magnesium has some serious problems. Firstly, it is expensive, and most distressingly, it burns quickly and brightly once it ignites. Magnesium catches fire at about 1200 F. Due to that, it is never used in areas with high heat. Consequently, magnesium is typically used in structural components or skin that is not in areas that get hot. However, it is worth noting that alloys of magnesium have recently been developed that maintain all of the strengths but are not as flammable. We may begin to see more magnesium in the skies in the future.
Stainless steel‘s strongest values are its strength and corrosion resistance. Because of this, engineers often use stainless in control cables, or components exposed to heat or salt. As such, stainless is most common on seaplanes or high speed aircraft. The biggest problem with stainless is that it lacks flexibility, and when put under stress is more prone to cracking. Given how much airplanes shift and move, this is a significant issue.
By far the most diverse and futuristic of the categories in this blog, synthetics includes carbon fiber, fiberglass, synthetic foam, and composites. There are far too many to discuss here, but there are a few takeaways. Many synthetics are extremely light and strong, such as carbon fiber. Others resist heat very well. Many synthetics are new enough that they are still being tested, but expect to see increasing numbers of airplanes built with these over the upcoming years. This is especially true as escalating fuel costs and growing awareness of the impacts of climate change set in. Many companies and contests are already proposing radically different aircraft which rely on large amounts of synthetic components.
In many ways, titanium is the perfect metal for aircraft. It is as strong as steel and resists corrosion better than aluminum and stainless. Also, while it is 60% heavier than aluminum, it’s 50% lighter than stainless. However, the big downside of titanium is that it is very expensive. This makes titanium aircraft pretty rare. Titanium is more common in airplane components that are exposed to high heat for long periods. Specifically, it is ideal for firewalls, turbine engine shrouds, and skins on high speed aircraft. The most famous example of an all-titanium aircraft is the SR-71 Blackbird.
Despite falling out of common use, wood fuselages are still being made today. Typically, modern wooden aircraft are either reproductions of historic aircraft, repaired historic aircraft, or private hobbyists building their own planes. Spruce is arguably the most popular wood for aircraft. In fact, by 1916, spruce from northern California, Oregon and Washington became the most popular aircraft wood in the US, Great Britain, France, and Italy. Also consider the famous all-wooden Hughes H-4 Hercules is also known as the Spruce Goose.
I hope this has proved informative and entertaining! If you have and pictures of aviation projects you’d like to share we with us, we’re happy to have them!
Also, check out this cool blog post about scrap drives during World War II, when civilians were encouraged to turn in metal, paper, wood, and rubber items to help recycle them for the war effort.
Have a great National Aviation Day!
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