The Evolution Of The Airplane

Powered flight began over 100 years ago in 1903. Technology and aircraft design have, of course, changed a considerable amount since then. Early changes saw the perfection of the techniques and methods of flights. These then moved to improve designs to meet changing trends and demands and to focus on profitability and efficiency. Going forward, this will likely continue, but with an even greener angle.

In this article, we take a look at the key moments and events in the development of the airplane. There are lots of things to discuss, and we can’t cover everything, but we will choose some of the most significant.

Before powered flight

We tend to think of the start of the airplane as the first “sustained and powered” flight, and the Wright brothers are regarded as the first to achieve this, in 1903. But there had been interest and experimentation in flight long before this.

For possibly the earliest recorded pondering of flight, take a look at the Greek legend of Icarus, from over 2,000 years ago. Icarus and his father try to escape from Crete (and the Minotaur) using feather and wax wings. Around the same time, several Indian epics refer to flying palaces (known as Vimana).

The earliest possible real experiments start in the 9^th Century with the Andalusian inventor Abbas ibn Firnas designing a simple glider. Writings at the time refer to how he “flew faster than the phoenix in his flight when he dressed his body in the feathers of a vulture.”

Some more in-depth experimentation took place in the 16^th Century. Leonarda da Vinci researched the flight of birds and designed several flying machines based on this. His work survives in the “Codex on the Flight of Birds.” These are fascinating works, but as far as we know, no successful flying machine was built from them.

Powered propeller aircraft

Leading up to the Wright brothers

The English engineer George Cayley is one of the most important figures in the early development of the airplane. He was the first to investigate and document the forces of flight (weight, lift, drag, and thrust) and develop the concept of the airplane as a fixed-wing machine with systems for lift, propulsion, and control.

He designed and built several models, including successful gliders. His work, however, was limited by a lack of engine power or lightweight components. Nevertheless, what he designed had a lot of similarities with later powered aircraft, including the main wing and tail stabilizers.

Following the detailed studies by Cayley, there were several attempts to put them into practice. French aviator Jean-Marie Le Bris achieved flight with a glider pulled by a horse.

And in 1886, another French aviator, Clement Ader, built a steam-powered airplane, known as ‘Eole.’ This had partial success, achieving flight off the ground of about 50 meters.

The Wright brothers first flights in 1903

It was in 1903 that the first successful powered flight took place. Wilbur and Orville Wright flew the first powered airplane on December 17th, 1903, near Kitty Hawk in North Carolina. This is recorded by the record-setting body, the Fédération Aéronautique Internationale, as “the first sustained and controlled heavier-than-air powered flight.”

This first attempt in 1903 was a simple one. The aircraft only flew 37 meters and stayed airborne for just 12 seconds. The brothers kept working on this, and by 1905 their third aircraft, the Wright Flyer III, was capable of longer, controlled flight. The longest test flight in 1905 lasted 39 minutes and covered over 38 kilometers, with larger fuel tanks and engine coolant added to facilitate more prolonged operation.

After these successful flights, the brothers disassembled the aircraft to prevent competitors from copying it. It was not until 1908, when the brothers had secured contracts in America and France, that it flew again. This time it was converted to carry a passenger. And in May 1908, mechanic Charles Furnas became the first airplane passenger in history.

Other aviators were working on similar designs around the same time. Perhaps the most significant was from the French inventor Louis Bleriot. The Bleriot VIII airplane, flying in 1908, first introduced the concept of a single stick to control both roll and pitch, with a foot-operated pedal for the rudder. The same concept, of course, has remained with aircraft right up to today.

Military aircraft from 1914

The outbreak of World War I in 1914 led to many companies and governments expediting aircraft design for military purposes. The propeller-based technology developed for previous early aircraft was taken further, producing larger aircraft with more speed and range.

Italy was one of the first countries to operate military reconnaissance aircraft (during the Italian Turkish war in 1911). And during World War I, many countries used new or modified aircraft for photography, reconnaissance, bombing, and air to air combat.

In terms of aircraft technology, one of the most significant developments came from German engineer Hugo Junkers. His Junkers J1 aircraft, first flying in 1915, was the first aircraft to have an all-metal airframe. This was important for the later development of larger passenger aircraft.

Developing commercial possibilities

As well as development for military use, companies began looking at the possibilities for revenue earning passenger flights.

The first passenger service started in 1914. In January that year, the St. Petersburg-Tampa Airboat Line started a service between St. Petersburg and Tampa across Tampa Bay in Florida. This 20-minute flight was a significant milestone, forming the start of commercial aviation.

After the war, there was a rush of propeller based aircraft onto the civilian market. This gave rise to a new industry of leisure and sightseeing flights, as well as demonstrations and air shows. But there was also desire, and incentives, to develop new services and expand the limits of aircraft.

The first transatlantic flight took place in 1919, with British aviators John Alcock and Arthur Whitten-Brown flying a modified Vickers military aircraft. This followed the offer of a prize of £10,000 from the Daily Mail newspaper in London for the first successful flight “from any point in the United States of America, Canada or Newfoundland and any point in Great Britain or Ireland in 72 continuous hours.”

In 1927 Charles Lindberg won the $25,000 prize for the first solo non-stop crossing of the Atlantic. And Australian Charles Kingsford Smith (and crew) became the first to cross the Pacific in 1928 and the first to fly around the world in 1929.

This era saw a lot of experimentation and development with aircraft types as well. For example, the German-built Dornier Do X, launched in 1929, was the largest aircraft at that time. It could carry up to 169 passengers (but usually only 66, or less if converted for overnight sleeping accommodation). This twelve-engine aircraft had a range of up to 1700 kilometers and offered great potential. Only three were built, though, with the Great Depression of the 1930s taking its toll.

Commercial success with the Douglas DC3

The years after World War I saw many aircraft developments. The aim was always the operation of successful and profitable commercial flights. The first aircraft to achieve this was the Douglas DC-3, launched in 1936. This was not large (compared to aircraft today, or even some predecessors) with a capacity of just 32 passengers (or 14 if equipped with beds).

The DC-3 improved on range, speed, and reliability. It offered a transcontinental US service with just three stops. According to analysis in the Smithsonian, it was the first profitable passenger aircraft, able to operate passenger services without any cargo or mail subsidies.

In total, over 11,000 aircraft (including variants) were built. Production continued up to 1942 when the surplus of ex-military aircraft entering the market after World War II saw its end. It is certainly a long-lived and well-built aircraft. As of August 2020, there were 172 DC-3 aircraft still in operation (though sadly not in passenger service).

The start of the jet age – 1952

The next major advance in airplane design was with the introduction of the jet engine. Development work on jet engines began in the 1930s, and the first operational jet aircraft was the German Heinkel He 178 in 1939, and then the Messerschmitt Me 262, which saw military service in Germany from 1947. And in Britain, Boeing introduced the jet-powered B-47 for military use in 1947.

The first passenger jet aircraft though, was the de Havilland Comet, entering service in 1952.  While it marked a significant step forward in aviation, this early jet aircraft had a number of serious problems. Most notable were issues with its fuselage, windows, and pressurization. It was not until its fourth iteration, the Comet 4, that the problems were solved and sales increased. But, by this time, other aircraft designers had learned from its mistakes and offered competitive alternatives.

The Boeing 707

There were several successors, and competitors, to the Comet, including the DC-8, Vickers VC-10, the Tupolev Tu-104, and the Boeing 707. These were all interesting aircraft in their own ways, but the 707 stands out as the most successful.

Boeing built on its previous military success with the 707. It used the same Pratt & Whitney turbojet engines as the B-52 Stratofortress, and its original design was intended to double up as a military tanker aircraft. It first flew in December 1957 and remained in production until 1978, with 856 built and delivered to airlines.

While it was not the first commercial jet aircraft, it was the first highly successful one and is often credited as the start of the jet age. It also established Boeing as a dominant civilian manufacturer, with the 7×7 series continuing, of course, to today.

Boeing incorporated many design elements based on problems with earlier jet aircraft and from customer feedback. This included:

• A wider fuselage, allowing five abreast seating and better cargo payload.
• Moving engines to underwing pods was considered safer in the event of a fire.
• Changes to flap design, and fuselage strengthening.

Adapting to the market – the 737 and the A320

Since the 1950s, there have been fewer fundamental changes to airplane design. Jet engines have remained but improved in power and efficiency, and cabin and cockpit technology has similarly improved but is still based around the same designs and concepts.

Boeing’s evolution to the 737 series shows this well. Following its success with the 707 and 727, it designed a new aircraft to beat the competition and win customers. The aircraft launched in 1967 and offered several design differences from the competition:

• Two engines rather than three or four. This appealed to customers looking to lower costs.
• Engines mounted under the wings, offering easier access and allowing a wider cabin.
• A wider fuselage offering six abreast seating, and handling of standard cargo containers.

The 737 has remained with us since 1967, moving through many variants. Each of these has offered updates to meet airline preferences and demands. This has included, for example, options such as combined cargo models, and adaptions for gravel landing, and an evolving focus on new engine technology and efficiency improvements.

But the base design, fuselage structure, and wing design, for example, have remained much the same. Why change what is already working, when you can improve it instead?

The Boeing 737 has been the most sold aircraft to date, with 10,580 aircraft delivered across all 737 families (according to data from Boeing as of July 2020).

And Airbus has followed a similar model with its A320 family. Since the launch in 1987, Airbus has offered several different sized variants and evolved these to provide technology and efficiency upgrades.

It may have started later than Boeing, but it has also seen tremendous success. The A320 family now beats the Boeing 737 in numbers of aircraft ordered.

Making aircraft larger – the Boeing 747

The other significant change since the early jet aircraft is the development of larger aircraft. The best example here is the launch of the Boeing 747 in 1970, which has been the best selling widebody aircraft to date.

The motivation for this came from Pan American World Airways. It asked Boeing to design an aircraft around 2.5 times the size of the Boeing 707, and development began once Pan Am committed to an order for 25 aircraft in April 1966. Such close interaction between one airline and a manufacturer is unusual, and the involvement of Pan Am in the development of the 747 is unmatched in other developments.

Such a large aircraft required several changes to previous aircraft design, including:

• The addition of a second deck. This was initially planned to be a full deck, but this was not possible due to safety restrictions at the time. The resulting design allowed for a full deck of cargo, and nose loading, a significant success factor for the 747.
• A new high-bypass turbofan engine design was needed for the larger, heavier airframe.  Pratt & Whitney joined the 747 development, designing the JT9D engine specially for it.

The 747 was significant not just from a technical point of view, but also from an economic one. It changed travel in several ways. It allowed airlines to offer lower fares and longer routes. Combined with the deregulation of airfares in the US around the time of its launch, this opened flying to more passengers.

The extra available space gave airlines new options for onboard facilities and cabins. Some of the luxuries seen in the early days of aviation returned, including spacious first class cabins and lounge areas. Airlines also used the extra space to create new cabins. This started in the 1970s with some airlines creating a ‘premium’ offering within their economy cabins, and by the 1980s, it led to the creation of business class as a third cabin.

And larger again with the A380

Aircraft size limits would not be pushed so far again until the development of the Airbus A380. Airbus looked at various versions of a large aircraft, including an interesting design of combining two large fuselages side by side (based on the A340). This eventually led to the concept of a two-deck aircraft. The A380 was formally announced at the Farnborough Air Show in 1990, with a target of 15% lower operating cost than the 747.

Several other large aircraft were proposed but never built, including:

• The two-deck McDonnell Douglas MD-12, proposed in 1993 but canceled due to lack of interest from airlines
• Lockheed Martin planned a Large Subsonic Transport aircraft in 1996, seating over 900, but faced technical challenges.
• Russia proposed an ever larger, up to 1000 capacity, Sukhoi KR-860.
• And Boeing twice proposed to stretch the 747 but dropped it to follow point to point models with the 777.

The A380 is a great aircraft, but it has not seen the same success as the 747. It is not so much the design that has let it down – finally engineering a two-deck aircraft was an outstanding achievement. It was more the changes in operating models and preferences that sealed its fate.

The A380 has been far from a failure, with 251 orders. We have looked before at why the A380 has not been so successful. The idea at the time of launch was that airlines would use it for high capacity, hub-to-hub routes.

Preferences changed though, with many airlines shifting to a point to point model, with more efficient, lower capacity aircraft. It also carries one significant design limitation: its size and large wingspan severely limit the airports to which it can operate. This is something that Boeing has learned from with its new 777X, developing folding wingtips to get around this problem.

Supersonic aircraft

For many aviation enthusiasts, the peak of jet age possibilities was reached with supersonic flight. The sound barrier was first broken in 1947 by the American experimental aircraft, the Bell X-1. This was powered by a rocket-based engine using liquid oxygen and ethyl alcohol.

Developments after this resulted in plenty of supersonic experimental and military aircraft. But it was not until the 1960s that supersonic passenger aircraft were developed, most famously, Concorde.

Supersonic aircraft required some major changes in aircraft design:

• Significant extra power was needed to overcome additional drag at high speed.
• The wings needed to be re-designed to lower wingspan (and with it, drag). The solution reached for Concorde was a delta wing, which is much more efficient at high speeds (but with compromise and high angle of attack at low speed).

Concorde is the most well known supersonic aircraft. It was a joint development aircraft between the UK and France and was launched in 1976. Only 20 aircraft were built, and only British Airways and Air France ever operated them. It was not initially intended for just these two airlines, though, and in fact, 18 airlines placed options for it.

There was also a supersonic aircraft developed by Russian manufacturer Tupolev, The Tu-144. And Boeing came close to producing the supersonic 2707 but canceled the project due to insufficient orders.

Supersonic travel is an exciting development, but it ended with the retirement of Concorde in 2003. The limitations are not so much in airplane technology but in efficiency and cost. High operating costs lead to high ticket prices, and this is not a route that manufacturers and airlines have chosen to follow post-Concorde. This may change soon, however, with US company Boom Supersonic developing Overture, a Mach 2.2 supersonic passenger aircraft.

Improvements in efficiency

A major focus of the past couple of decades has been on improving airplane efficiency. Many of the early achievements were fantastic, but resulted in heavy aircraft, fuel-hungry engines, and high levels of emissions. As technology has improved and attitudes towards carbon footprints and greener industry have shifted, manufacturers have focussed on making changes.

Switching to twin engines

One of the significant changes to affect aircraft since the 1970s has been the improvement in twin-engine performance and safety. Early jet aircraft (such as the Comet and the 707) had four engines. At the time, twin engines were severely limited in where they could fly, having to remain no more than 60 minutes away from a diversion airport. Transoceanic flights remained the domain of four-engine and later three-engine aircraft.

This changed from the 1980s with the introduction of  ETOPS (Extended-range Twin-engine Operational Performance Standards). This allowed twin-engine aircraft to be approved to fly further from a diversion airport, recognizing their improving safety standards. The first rating, of 120 minutes, was given to Trans World Airlines flying a 767.

Ratings have since increased significantly. The A350, for example, is rated to fly 370 minutes from a diversion airport. This has been a major factor in the decline of four-engine aircraft, making way for significant improvements in much more efficient and cost-effective twins.

Four engines now are only needed for heavy airframes (such as the A380). There are limited advantages in routing any more, as this map of the off-limits areas for the higher ETOPS ratings show. The only places that require four engines now are flights over Antarctica.

Improving new aircraft

As new twins have been introduced, there has been a constant effort to improve efficiency. Changes have included more efficient (and lower emission) engines, aerodynamic and wing design changes, and increasing use of composite materials in aircraft construction.

This has been one of the major changes in the new series of 737 and A320 aircraft introduced over the past decades. For example, each new series of the 737 has introduced improvements. The Classic series improved engines and aerodynamics over the Original series; the Next Generation series did the same to compete with the new A320; and the 737 MAX Series took this even further to compete with the A320neo.

To put this into numbers, according to The 737 Information Site, there is a 14% efficiency improvement between the Next Generation and 737 MAX series. And the same source quotes fuel burn reduction of 20% moving from the Original to the Classic series and a further 7% improvement in the Next Generation series.

A similar evolution has taken place with widebody aircraft. The 777 series has seen many improvements since its launch in 1989, including efficiency improvements. And the new 777X will take this even further.

The Boeing 787 is another excellent example of this. The program was initially known as the 7E7 program. The E represented the leap the aircraft would make in efficiency, economy, and environmental standards. And it has delivered on this efficiency, as Simple Flying explored previously (in comparison with the A350). It is regarded as the most fuel-efficient aircraft on the market.

More improvements coming in the future

The 777X and further improvements in efficiency

For the moment, the near future of airplanes lies in further technology and efficiency gains.  One of the most anticipated new aircraft, the Boeing 777X, is due to enter service in 2021.

The 777X promises incredible fuel efficiency with innovations including:

• The largest engines ever on a civilian aircraft (though also made lighter with composite fan technology).
• Folding wingtips to allow larger wings to improve efficiency, but not restrict airport operations.
• Composite wing construction, and raked wingtips.

Boeing is not alone with pushing efficiency in new aircraft. The A350 is also a highly fuel-efficient aircraft, with 53% composite construction, ‘adaptive’ wings that move in flight to reduce drag and advanced aerodynamic improvements to the wing shape.

Introducing new technology

Looking further ahead, there are moves to radically change how aircraft are powered. The use of kerosene is increasingly acknowledged as a problem in a carbon-conscious world. Options currently being explored and developed include battery technology and hydrogen power.

Both of these technologies have seen smaller prototype developments, but are likely a long way from adoption in large aircraft design.

Battery technology needs to improve to deliver enough power with acceptable battery size and weight. Hydrogen power requires extensive engine and technology updates, as well as a large scale change in fuel storage and delivery infrastructure globally. These are significant challenges that will require a shift in focus to allow the investment needed, but this is starting to happen in some areas.

And as we move forward, high technology and pushing the capabilities of aircraft have not been forgotten.  Boom Supersonic’s Overture aircraft could carry passengers as soon as 2025 (and takes much more interest in its carbon footprint than Concorde did). And missions such as Qantas’ Project Sunrise are pushing the limits of ultra-long direct flights.

There are so many events, developments, and different aircraft involved in the evolution of air travel. This article has looked at just some of the most significant. Feel free to discuss more in the comments below. We would love to hear about other events of importance you would like to highlight.