science

Ground-effect vehicle

Ground-effect vehicle is a science 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 Ground-effect vehicle rather than just read about it. In short: A ground-effect vehicle (GEV), ekranoplan (from Russian: экранопла́н "screenglider"), wing-in-ground-effect (WIGE or WIG), ground-effect craft/machine (GEM), wingship, flarecraft, or surface effect vehicle, is a hybrid surface vehicle/aircraft that makes use of wings to generate minimal lift and ground effect, to reduce aerodynamic drag. Ground effect is the interaction between a moving wing and a stationary surface…

Key takeaways

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

Reference excerpt

A ground-effect vehicle (GEV), ekranoplan (from Russian: экранопла́н "screenglider"), wing-in-ground-effect (WIGE or WIG), ground-effect craft/machine (GEM), wingship, flarecraft, or surface effect vehicle, is a hybrid surface vehicle/aircraft that makes use of wings to generate minimal lift and ground effect, to reduce aerodynamic drag. Ground effect is the interaction between a moving wing and a stationary surface below it. Typically, a GEV will glide just above a relatively level surface. Some vehicles can operate over any flat area such as a lake or flat plains. Technically, GEVs do not include racecars that utilize ground-effect, for increasing downforce, as such vehicles are intended to remain in direct contact with a racetrack.

Ground effect

Takeoff Any airfoil passing through air increases air pressure on the underside, while decreasing pressure on the upper side, which generates lift. The high and low pressures are maintained until they flow off the ends of the wings, where they form vortices that are the major source of lift-induced drag—normally a significant portion of the total drag. In GEV, the angle of attack is the angle between its chordline (a straight line from the leading edge to the trailing edge) and the ground. On takeoff, airplanes pitch their noses up to increase the angle of attack to reach the ideal of 12-20 degrees (depending on wing design and other factors).

Design

Placing the wing near a surface has the same effect as increasing the aspect ratio because the surface prevents wingtip vortices from expanding, but without the complications associated with a long, slender wing. The stubby wings on a GEV can produce as much lift as the much larger wing on a transport aircraft, though only while close to the earth's surface. Once sufficient speed has built up, some GEVs can function as conventional aircraft until approaching a destination. However, they are unable to land or take off without a significant amount of help from the ground effect, and cannot climb until they have reached a much higher speed. The greater the wingspan, the less drag created for each unit of lift and the greater the efficiency of the wing. GEVs are not statically supported upon a cushion of pressurized air from a downward-directed fan. Some GEV designs, such as the Russian Lun and Dingo, blew air under the wing using auxiliary engines to assist takeoff; however they still require forward motion to generate sufficient lift to fly, unlike hovercraft, also lacking low-speed hover capability. GEVs also have no contact with the surface when in flight.

Straight wing Used by the Russian Rostislav Alexeyev for his ekranoplan. The wings are significantly shorter than those of comparable aircraft, and this configuration requires a high aft-placed horizontal tail to maintain stability. The pitch and altitude stability comes from the lift slope difference between a front low wing in ground-effect (commonly the main wing) and an aft, higher-located second wing nearly out of ground-effect (generally named a stabilizer). A design by REGENT uses a related design in the form of an approximately L-shaped wing attached to the top of the fuselage, with a pontoon at the end for water landings.

Reverse-delta wing Developed by Alexander Lippisch, this wing allows stable flight in ground-effect through self-stabilization. This is the main Class B form of GEV. Hanno Fischer later developed WIG craft based on the configuration, which were then transferred to multiple companies in Asia, thus becoming one of the "standards" in GEV design.

Tandem wings Tandem wings can have three configurations:

A biplane-style type-1 utilising a shoulder-mounted main lift wing and belly-mounted sponsons similar to those on combat and transport helicopters. A canard-style type-2 with a mid-size horizontal wing near the nose of the craft directing airflow under the main lift airfoil. This type-2 tandem design is a major improvement during takeoff, as it creates an air cushion to lift the craft above the water at a lower speed, thereby reducing water drag, which is the biggest obstacle to successful seaplane launches. Two stubby wings as in the tandem-airfoil flairboat produced by Günther Jörg in Germany. His particular design is self-stabilizing longitudinally.

Advantages and disadvantages

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Ground-effect vehicle

Start with the simplest possible case. Write down what Ground-effect vehicle claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Ground-effect vehicle 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 Ground-effect vehicle 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 Ground-effect vehicle

In research: Ground-effect vehicle appears in science 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 Ground-effect vehicle 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: Ground-effect vehicle is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aircraft configurations, Amphibious vehicles, Ekranoplans, so understanding it makes those chapters shorter.
In everyday life: Look for Ground-effect vehicle 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 Ground-effect vehicle in 20 minutes

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

Frequently asked questions

What is Ground-effect vehicle in simple terms?

Why does Ground-effect vehicle matter?

Because it connects several science 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 Ground-effect vehicle?

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 Ground-effect vehicle.