Why Can’t Engineers Improve on a 60 Year Old Aircraft Design?
John Hayes posted on February 16, 2017 | 10248 views

Here are two pictures of a Cessna 172. One is from 1957 and the other was built between 2001 – 2009. Can you spot the differences?  It’s not easy, because the design hasn’t changed a whole lot over that 50 year period.

1957 Cessna 172

Performance at 75% power

Cruise speed 108 kts

Range 395 nm

Fuel consumption 8.0 gph

(Source: Wikipedia)

2001 – 2009 Cessna 172S

Performance at 75% power

Cruise speed 124 kts

Range 516 nm

Fuel consumption 9.5 gph

(Source: Wikipedia)

Now look at two pictures of a Corvette from the same time periods.  Can you imagine that a 1958 Corvette design would pass the safety and performance requirements of 2006 (let alone 2017)?  Me neither.

1958 Corvette

Performance

0 – 60 mph 7 seconds

Fuel consumption 18.3 mpg

Top Speed – 155 mph

2006 Corvette C6

Performance

0 – 60 mph 4.2 seconds

Fuel consumption 21 mpg

Top Speed – 186 mph

Why haven’t aircraft designs kept up with automobiles when it comes to design and performance? It’s not due to a lack of creative and talented aircraft engineers. Rather, this fossilization of general aviation design is due to two other culprits: regulation and product liability. In short, regulations have made it too expensive for innovators to certify changes to small aircraft. At the same time, product liability cases have awarded huge settlements that have crippled companies, making small aircraft uneconomical to build and sell.

So the question for aspiring aircraft inventors is this: Have advances in materials and design technology now come far enough to reinvent small aircraft despite the challenges of regulations and product liability?


Elixir Aircraft is Building a Modern Small Aircraft

Cyril Champenois met Arthur Leopold-Leger at Kingston University while they were both studying aerospace engineering. Arthur later founded Elixir Aircraft with a goal to build a superior small aircraft using modern materials and design technology. Cyril joined Arthur as COO of Elixir.

Both Arthur and Cyril brought more than their engineering degrees to Elixir. Arthur’s experience as a competitive sailor showed him the performance gains that were possible with composite materials. He had also logged over 1,000 hours in the air and assembled 20 aircraft. Cyril, meanwhile, worked for five years as an aerospace consultant for clients that included Boeing and Airbus.

[2018] Elixir Aircraft

Performance

Cruise speed 153 kts

Range 1,000 nm

Fuel consumption 3.7 gph

What does it mean to reimagine a small aircraft? Cyril pointed out four areas where small aircraft were ripe for improvement:

  1. Safety
  2. Simplicity of operation and maintenance
  3. Performance
  4. Comfort

General aviation has a very poor safety record, particularly in the USA. The team at Elixir aims to improve that record with many safety enhancements. According to Cyril, “Every one of our aircraft will have a structural parachute that can land the entire aircraft in case of emergency.”  He also noted that “Aircraft are complex, which in itself can make them dangerous. We have developed a smart user interface that will reduce the risk of operator errors.” 

When it comes to performance, the Elixir team has a significant leg up on historic designs. “By using carbon fibre composites,” Cyril explained, “we can achieve superior performance in terms of speed, range and fuel economy.”

Not only does Elixir aspire to deliver a superior performing aircraft, they aim to make them more affordable for more pilots. For example, the larger 4-seat Cessna Skyhawk carries a base price of more than $300,000. Elixir hopes to debut their two-seater at less than $175,000 (160,000 Euros).

Elixir is not the first company to take their best shot at redefining the small aircraft market. Notably, Cirrus Aircraft has successfully introduced general aviation planes using composite materials. Many others have tried and failed, often due to the encumbrances of regulation. It is not easy to get a new design certified.

To minimize the chances that regulations will ground their dream, Elixir is introducing their first aircraft under European regulations CS-LSA (for two seater aircraft), a special designation that has no equivalent in the USA. The company began their certification process in January of 2017, and hopes to be complete by the end of the year.


Composite Materials Allow a Completely Different Design and Manufacturing Process

Like many start-ups, Elixir focused their design efforts on the aspects that will create the biggest differentiation between their aircraft and the competition. Elsewhere, they used generally available parts. In Elixir’s case, that meant using standard avionics, GPS and engines, for example, while creating original designs for the fuselage, wing and landing gear.

The biggest difference in the design of the Elixir aircraft is that both the fuselage and the wings are molded into a single part made from a carbon fibre composite material. This material and process allows the Elixir to be both lighter and stronger than those made from riveted aluminum.

For example, this aileron weighs only 745 g. The entire aircraft will weigh in at only 265 kg (585 lbs) when empty. The payload is planned to be 280 kg (617 lbs).

“This single part design also makes the aircraft safer,” according to Cyril, “because there is no corrosion between parts.”

The company is in the process of building their first wing now, layering pre-impregnated carbon composites in a mold. This approach should save considerably on maintenance costs going forward as there are fewer parts and fasteners to inspect.


New Design Technology Makes Disruption Possible

In the 1950’s when Cessna was developing the 180, they had to build and test a number of prototypes. That can be very slow and expensive. Fast forward to 2017 and aerospace designers can complete a virtual prototype much faster and at far less expense. “We were really lucky that there was a cloud-based design environment available when we launched this project,” said Cyril.

He was speaking of the 3DEXPERIENCE Platform from Dassault Systèmes. “I initially wanted to use CATIA V5 for the aircraft design. However, there were only three of us and we were trying to conserve funds, so it made sense for us to use a cloud-based system so that we didn’t spend money on software licenses and computer hardware.”

That decision to save funds came with additional benefits.  The Elixir team used their cloud solution to capture and manage their design requirements, develop their detail design models and to manage the various project steps. According to Cyril, “This had the added benefit of storing all of our documentation in one place, which is really important when it comes to certification.”

According to Andy Kalambi, Vice President at Dassault Systèmes, the 3DEXPERIENCE platform allows data to flow seamlessly between various apps, allowing all participants in a design project access to the latest version of any design and documentation. He said that, “having total transparency and no silos within a design team can greatly increase the velocity of designs.”


Having total transparency and no silos within a design team can greatly increase the velocity of designs. 

Andy Kalambi


He also pointed out that Dassault Systèmes has been integrating a wide range of applications onto their platform with a goal to support a complete virtual experience before building any prototypes. For example, an ideal scenario would allow a design team to:

  1. Identify design parameters for optimization
  2. Identify and share the optimum designs
  3. Analyze the product performance virtually
  4. Run optimizations directly on the platform

Elixir was not able to influence all of their design partners to use the 3DEXPERIENCE platform. For example, they outsourced their FEM analysis to an external consulting firm who used their own set of tools. As Cyril said, “when you are in a hurry, it is sometimes best to let people use the tools they have rather than introducing them to new ones.” The Elixir team also outsourced the renderings. In this case, the external consultants were also using the 3DEXPERIENCE platform, so the data transfer was easy.

The dream, according to Dassault’s Kalambi, however, is that data won’t have to be transferred at all. Rather, it will be developed, analyzed, and produced virtually, all on a single platform on the cloud before any prototypes are built.


Next Steps to get Elixir Off the Ground

The company is currently going through the first stages of certification with the European Aviation Safety Agency. They plan to complete their first prototype in time for the Paris Air Show this spring.

Once that hurdle is crossed, the commercial sales will follow, ideally in 2018.

Personal flight is simply out of reach for most aspiring pilots. Elixir’s project represents an important step towards a safer high-performance aircraft at a more accessible price.

Many teams before Arthur and Cyril have tried to invent exciting new small aircraft, only to run into an impenetrable wall of regulations and product liability challenges. This team has their work cut out for them. I hope they make it. 

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