Interactive module Conceptual aircraft design · Module 3
The First Estimate of Takeoff Weight
How heavy will it be? Before there is a drawing worth analyzing, a designer answers with a sketch, a page of statistics and the Breguet equations, and the answer sets the size of everything that follows. This module, written for third-year aerospace engineering students, works through that method step by step, sizing one business jet across seven lessons with interactive figures, a sizing calculator and questions that check your work.
- 7 lessons
- about 4½ h of lessons
- Works offline
Learning outcomes
By the end of the module you can:
- Derive and apply the sizing equation, and explain why it is solved by iteration. (Lesson 1)
- Evaluate statistical empty-weight trends in pounds or kilograms, choose the class, and apply technology factors. (Lesson 2)
- Estimate wetted area, \(\CDz\) and \(\LDmax\) from a sketch, and choose the cruise and loiter \(L/D\). (Lesson 3)
- Choose and convert specific fuel consumptions for jets and propellers. (Lesson 4)
- Build the mission fuel fraction from historical, Breguet and combat segment fractions. (Lesson 5)
- Close the sizing by iteration, check the answer, and size missions that drop payload. (Lesson 6)
- Find sensitivities and growth factors by resizing, and use trade studies. (Lesson 7)
How to use this module
Before you start: Module 1 (the design parameters, the drag polar, the Breguet range equation) and Module 2 (mission profiles and segment numbering). The course text is Raymer's Aircraft Design: A Conceptual Approach; this module uses its notation.
Work through the lessons in order. The times allow for working the examples on paper and doing the checks. A suggested plan in four sittings:
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Lessons 1–275 min
The sizing equation and its iteration; empty-weight statistics.
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Lessons 3–475 min
\(L/D\) from the sketch; engines and fuel consumption.
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Lessons 5–680 min
The mission fuel fraction; closing the loop and payload drops.
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Lesson 7, Practice Lab and Self-Check Quiz100 min
Sensitivities and trade studies, about 30 min of practice, then the 35-minute quiz.
About 5 h in total:265 min of lessons, 30 min of practice, 35 min for the quiz
Get the most out of it
- Keep pencil and paper handy
Try each worked example yourself before you open its solution, and keep track of units: the empty-weight statistics are in pounds, propeller fuel consumption in lb/(hp h).
- Do the checks
Every lesson has “Check your understanding” questions with hints and full solutions. You can type answers like
980/(1-0.2867-0.5721)orexp(-4600*0.65/(850*14.64)). - Practice until it is routine
The Practice Lab generates unlimited problems, each with a worked solution.
- Test yourself at the end
The Self-Check Quiz gives a score, solutions and a results page you can print or save as a PDF.
- Track your progress
Tick “Mark this lesson complete” at the end of each lesson. A ✓ appears here and in Contents; it is saved in this browser only.
- Keep the formulas close
Print the Formula Sheet and look up terms in the Glossary. The Sizing Calculator sizes any design you describe.
Lessons
Each lesson has interactive figures, worked examples and questions with instant feedback.
Practice, tools and reference
Use these alongside the lessons, or on their own when you revise.
Requirements
Any modern browser. Works offline.
- A current version of Chrome, Edge, Firefox or Safari, with JavaScript on. A laptop or desktop screen works best; the pages also fit tablets and phones.
- No internet connection, installation or account. Everything is inside this folder.
- Your progress is saved in this browser on this device. Private or incognito windows do not keep it.
Something not working? Read README.txt in the module folder for how to open the module and fix common problems.