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Putting it All Together

You have accomplished a lot over the last eleven lessons. You have learned about science, engineering, and aviation. You have flown a twin-engine airplane and landed on a carrier deck. You lengthened a wing and shortened a tail.

Now let’s put all that knowledge to good use and design your own airplane.

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Engineering Design Process

You know how sometimes it is difficult to start on a big school project? It can e tricky to know how or even where to begin! Plane design might seem that way, but we will guide you through the steps so you can design and produce your own aircraft.

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Engineering Design Process

The Engineering Design Process consists of four parts: Research, Planning, Prototyping, and Production. At the end you will have a new aircraft!

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Research

Research includes studying the underlying engineering, math, and science principles.

You have been doing research by working through the Fly to Learn lessons! Research includes looking at what other people and business are designing and building and what they have designed and built in the past.

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Research

Research also might involve studying what the public wants in an airplane. You might discover that people want an airplane that is faster or more fuel efficient than those for sale presently, or you might discover a new way to build airplanes that is cheaper than conventional methods.

Remember, engineers are very concerned with costs, money, and time. If a project takes more time, usually costs increase; also the engineer may not have time to wait!

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Planning

Planning consists of these steps:

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Planning

1. You begin the planning process by identifying an opportunity. In engineering, a need or problem should always be considered an opportunity. That is not a bad philosophy for life in general.

2. You then brainstorm to generate several possible solutions. Sometimes it can be tempting to choose the first idea that comes to mind. The best engineers know to generate more than one option and then consider all ideas to truly come up with the best and most innovative concepts.

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Planning

3. The next step is to choose an idea from the list you generated.

4. Once you have your idea chosen, you want to mathematically model that idea. It is better to do some calculations before constructions because you work smarter and faster with your brain than with your hands. This can ultimately save you time and money.

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Planning

5. After checking calculations it is time to build a proof of concept to test your idea. A proof of concept demonstrates whether an idea is feasible or possible. �
A proof of concept is usually narrow in focus. For example if you are designing a better airfoil you would build a small section of the wing, not the entire wing – and certainly not the whole airplane!

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Prototype

The prototype phase a few steps that may be repeated many times. Your goal should be for the prototype to get better with each repletion or iteration.

Iteration is an important part of the engineering process.

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Production

You build the airplane during the production phase. This can involve additional steps outside of manufacturing, such as marketing and sales. Many things have to be considered as well, such as your supply chain.

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Designing your airplane

Let’s go ahead and try it! You will be putting the engineering design process to work in this lesson by designing your own airplane, building your design in Plane Maker, and flying your design in X-Plane.

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Designing your airplane

Let’s assume during your research and planning phases you developed the following design specifications:

Airplane Performance Design Specifications:

Four-passenger airplane including the pilot
Each passenger can bring twenty pounds of luggage
150 knot cruise speed
550 nautical mile range

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Mathematical Modeling

Now let’s mathematically model your plane design. Since this is your first airplane, we will focus on the weight, wings, power, and range. Once we complete these calculations, you can build a prototype airplane in Plane-Maker.

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Mathematical Modeling: Weight

We need to calculate the weight of your airplane because all the other design calculations are based on the weight of your airplane without the weight of the fuel.

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Mathematical Modeling: Weight

We need to calculate the weight of your airplane because all the other design calculations are based on the weight of your airplane without the weight of the fuel.

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Mathematical Modeling: Weight

Gross airplane weight or take off weight is the weight of the empty airplane plus payload and fuel weight.

Modern airplane designers have learned through past experience that the airplane weight can be determine by dividing the Total Payload Weight by 30%, or 0.3.

This is an example of a rule of thumb. A rule of thumb is a rough estimation. Engineers often use rough estimations at the start of the design process.

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Mathematical Modeling: Weight

Gross Airplane Weight = Total payload weight divided by 0.3 = 253 lbs

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Mathematical Modeling: Wings

Now we need to calculate the size of the wings of our airplane. First we will calculate wing loading and then determine wing area, aspect ratio, and finally wingspan.

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Mathematical Modeling: Wings

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Mathematical Modeling: Wings

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Mathematical Modeling: Wings

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Mathematical Modeling: Wings

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Mathematical Modeling: Wings

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Mathematical Modeling: Wings

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Mathematical Modeling: Power

Power

The power required equals drag times velocity. The calculations to determine power are beyond the scope of this lesson. Let’s assume you need 150 horsepower. This kind of horsepower is called brake horsepower.

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Mathematical Modeling: Power

Power

A modern propeller is 80% efficient in converting the brake horsepower into actual thrust. This kind of horsepower is called thrust horsepower.

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Mathematical Modeling: Power

Power

A modern propeller is 80% efficient in converting the brake horsepower into actual thrust. This kind of horsepower is called thrust horsepower.

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Mathematical Modeling: Power

Power

We actually need more horsepower because we do not want to operate engines at full power. Engines running at full power wear out sooner, and they are less fuel efficient. Instead we want to operate the engines at 75% of Thrust Horsepower. This horsepower is called Rated Horsepower.

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Mathematical Modeling: Power

Power

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Mathematical Modeling: Range

Range

Let’s see how far we can fly our airplane on a single tank of fuel. We begin by calculating how much fuel the plane will carry. We calculate the total fuel available by multiplying Gross Airplane Weight x 15%.

15% is another rule of thumb used by engineers to design airplanes.

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Mathematical Modeling: Range

Range

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Mathematical Modeling: Range

Range

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Mathematical Modeling

Often we don’t meet all of our design goals with the first design. If we don’t achieve the necessary range, we can increase the amount of fuel, but then we will need more horsepower, which results in greater fuel consumption. Therefore, we will repeat this process several times to meet our design goals.

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Prototyping

We are now ready to build a prototype in Plane Maker!

Since you are using Plane Maker, you can quickly build your prototype, - in this case a virtual airplane – by modifying the RV-10. This will allow you to quickly try out your designs safely and economically.

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Prototyping

Complete the table in your student handbook. Begin by entering your values from our mathematical modeling in the second column. Note that for wingspan you will divide your value by two to calculate ½ Wing Span.

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Prototyping

Once you have completed your airplane, save it as yournameprototype and go fly it. Be sure to include the appropriate Payload Weight in the Weight and Balance section of X-Plane.

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Prototyping

How does your plane perform? Are there aspects that can be improved?

Based on your plane’s performance, make a change to your design. Make one change at a time, as any change you make to a design will have several effects on flight.

Each time you make a change, try out the new design. Each new design is called a prototype. Use these prototypes to optimize your flight performance.

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Production

Once you have iterated through designs and your plane performs well, you are ready for production. More details on production are outside the scope of this lesson.

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Additional Challenge

If you want another challenge consider designing a sports plane with the following requirements:

2 passengers including the pilot
250 thrust horsepower
Aspect ratio between 6 - 8