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Supercritical airfoil

Supercritical airfoil is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Supercritical airfoil rather than just read about it. In short: A supercritical airfoil (supercritical aerofoil in British English) is an airfoil designed primarily to delay the onset of wave drag in the transonic speed range. Supercritical airfoils are characterized by their flattened upper surface, highly cambered ("downward-curved") aft section, and larger leading-edge radius compared with NACA 6-series laminar airfoil shapes.

Supercritical airfoil — main illustration
Supercritical airfoil — illustration

Key takeaways

  • Supercritical airfoil belongs to engineering; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Supercritical airfoil to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Supercritical airfoil from memory before moving on to harder problems.

Reference excerpt

A supercritical airfoil (supercritical aerofoil in British English) is an airfoil designed primarily to delay the onset of wave drag in the transonic speed range. Supercritical airfoils are characterized by their flattened upper surface, highly cambered ("downward-curved") aft section, and larger leading-edge radius compared with NACA 6-series laminar airfoil shapes. Standard wing shapes are designed to create lower pressure over the top of the wing. Both the thickness distribution and the camber of the wing determine how much the air accelerates around the wing. As the speed of the aircraft approaches the speed of sound, the air accelerating around the wing reaches Mach 1 and shockwaves begin to form. The formation of these shockwaves causes wave drag. Supercritical airfoils are designed to minimize this effect by flattening the upper surface of the wing. The origins of the supercritical airfoil can be traced back to the German aerodynamicist K. A. Kawalki, who designed a number of airfoils during the Second World War. Following the end of the conflict, multiple nations continued research into the field, including Germany, the United Kingdom, and the United States. In particular, Hawker Siddeley Aviation designed a number of advanced airfoils that were, amongst other programmes, incorporated into the Airbus A300. In America, the aerodynamicist Richard Whitcomb produced supercritical airfoils similar to Kawalki's earlier work; these were used to devise a supercritical wing that was, in turn, incorporated into both civil and military aircraft. Accordingly, techniques learned from studies of the original supercritical airfoil sections have been used to design airfoils for several high-speed subsonic and transonic aircraft, from the Airbus A310 and Boeing 777 airliners to the McDonnell Douglas AV-8B Harrier II jumpjet.

History

… excerpt ends here. Continue reading the full article.

Illustrations

Supercritical airfoil: Conventional (1) and supercritical (2) airfoils at identical free stream Mach number. Illustrated are: A – supersonic flow region, B – shock wave, C – area of separated flow. The supersonic flow over a supercritical airfoil terminates in a weaker shock, thereby postponing shock-induced boundary layer separation.
Conventional (1) and supercritical (2) airfoils at identical free stream Mach number. Illustrated are: A – supersonic flow region, B – shock wave, C – area of separated flow. The supersonic flow over a supercritical airfoil terminates in a weaker shock, thereby postponing shock-induced boundary layer separation.
Supercritical airfoil: NASA TF-8A in 1973
NASA TF-8A in 1973
Supercritical airfoil: Thomas McMurtry before his flight on the Vought F-8A Crusader Supercritical Wing Airplane
Thomas McMurtry before his flight on the Vought F-8A Crusader Supercritical Wing Airplane
Supercritical airfoil: Supercritical airfoil Mach number/pressure coefficient diagram (y axis: Mach number, or pressure coefficient, negative up; x axis: position along chord, leading edge left). The sudden increase in pressure coefficient at midchord is due to the shock.
Supercritical airfoil Mach number/pressure coefficient diagram (y axis: Mach number, or pressure coefficient, negative up; x axis: position along chord, leading edge left). The sudden increase in pressure coefficient at midchord is due to the shock.

Worked examples

Example 1 — a first encounter with Supercritical airfoil

Start with the simplest possible case. Write down what Supercritical airfoil claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Supercritical airfoil before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Supercritical airfoil ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Supercritical airfoil

In research
Supercritical airfoil appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Supercritical airfoil in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Supercritical airfoil is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aircraft aerodynamics, Aircraft wing design, American inventions, so understanding it makes those chapters shorter.
In everyday life
Look for Supercritical airfoil outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Supercritical airfoil in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Supercritical airfoil means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Supercritical airfoil out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Supercritical airfoil in simple terms?

A supercritical airfoil (supercritical aerofoil in British English) is an airfoil designed primarily to delay the onset of wave drag in the transonic speed range. Supercritical airfoils are characterized by their flattened upper surface, highly cambered ("downward-curved") aft section, and larger l…

Why does Supercritical airfoil matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Supercritical airfoil?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Supercritical airfoil.

Tags

  • Aircraft aerodynamics
  • Aircraft wing design
  • American inventions

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