chemistry

Sikorsky S-72

Sikorsky S-72 is a chemistry 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 Sikorsky S-72 rather than just read about it. In short: The Sikorsky S-72 was an experimental Sikorsky Aircraft compound helicopter developed as the Rotor Systems Research Aircraft (RSRA) for the National Aeronautics and Space Administration (NASA) and the United States Army. The RSRA was a testbed for rotor and propulsion systems for high-speed.

Key takeaways

Sikorsky S-72 belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Sikorsky S-72 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Sikorsky S-72 from memory before moving on to harder problems.

Reference excerpt

The Sikorsky S-72 was an experimental Sikorsky Aircraft compound helicopter developed as the Rotor Systems Research Aircraft (RSRA) for the National Aeronautics and Space Administration (NASA) and the United States Army. The RSRA was a testbed for rotor and propulsion systems for high-speed.

Design and development

RSRA

Sikorsky and Bell Helicopters competed for the RSRA contract. Bell's preferred proposal was the "Bell 646A" with rotors based on the Bell 240 UTTAS; the alternative was the smaller "Bell 646B" based on the Bell 309 KingCobra. Sikorsky proposed either a new aircraft or a modified Sikorsky S-67 Blackhawk with the rotor and gearbox from the Sikorsky S-61. Sikorsky won the contract for two aircraft in January 1974. The modified S-67 became the S-72. The S-72 could be fitted with wings and General Electric TF34 turbofans to allow compound helicopter configurations to be experimentally investigated at speeds up to 300 knots (560 km/h; 350 mph). In addition, it could fly as a fixed-wing aircraft without a main rotor. Unique among helicopters of its time, it was fitted with a crew emergency extraction system. This system, when activated, fired explosive bolts that severed the main rotor blades, escape panels were blown off the roof of the aircraft. The crew was then extracted using rockets, rather than by a traditional ejection seat as on fixed-wing aircraft. The RSRA was a pure research aircraft developed to fill the void between design analysis, wind tunnel testing, and flight results of rotor aircraft. The joint NASA/Army project began in December 1970, with first flight on October 12, 1976. The first of two aircraft arrived from Sikorsky to NASA on February 11, 1979. One notable test performed with the RSRA was the use of the main and tail rotor load measurement system to determine the vertical drag of the airframe. In 1981, NASA and the US Army solicited proposals for fitting a four-bladed main rotor to the RSRA. Sikorsky proposed fitting a UH-60A main rotor to the RSRA in their proposal, while Hughes Helicopters proposed fitting a YAH-64A main rotor, and Boeing Vertol proposed fitting a YUH-61A or BV-347 main rotor. In the end, this program did not proceed.

X-Wing

The X-Wing Circulation Control Rotor Concept was developed in the mid-1970s by the David W. Taylor Naval Ship Research and Development Center under DARPA funding. In October 1976, Lockheed Corporation won a DARPA contract to develop a large-scale rotor to test the concept. The X-Wing was conceived to complement rather than replace helicopters and fixed-wing aircraft. The X-Wing was intended to be used in roles such as air-to-air and air-to-ground operations, as well as airborne early warning, search and rescue and anti-submarine warfare. These roles could take advantage of the aircraft's ability to hover and maneuver at low speeds and to cruise at high speeds. Intended to take off vertically like a helicopter, the craft's rigid rotors could be stopped in mid-flight to act as X-shaped wings to provide additional lift during forward flight, as well as having more conventional wings. Instead of controlling lift by altering the angle of attack of its blades as more conventional helicopters do, the craft used compressed air fed from the engines and expelled from its blades to generate a virtual wing surface, similar to blown flaps on a conventional platform. Computerized valves made sure the compressed air came from the correct edge of the rotor, the correct edge changing as the rotor rotated. In late 1983, Sikorsky received a contract to modify one S-72 RSRA into a demonstration testbed for the X-Wing rotor system. The modified airframe was rolled out in 1986. While many of the aircraft's technical issues had been resolved, with plans for it to begin flight tests with the rotor/wing system, it never flew. Budgetary requirements led to the program being canceled in 1988.

Specifications (S-72)

Data from Jane's all the World's Aircraft 1977–78General characteristics Crew: 3 Length: 70 ft 7 in (21.51 m) Wingspan: 45 ft 1 in (13.74 m) Height: 14 ft 6 in (4.42 m) to top of rotor hub Wing area: 370 sq ft (34 m2) Airfoil: NACA 63-415 Empty weight: 21,022 lb (9,535 kg) (compound helicopter configuration) Gross weight: 26,200 lb (11,884 kg) (compound helicopter configuration) Powerplant: 2 × General Electric T58-GE-5 turboshaft, 1,400 shp (1,000 kW) each Powerplant: 2 × General Electric TF34-GE-400A turbofan, 9,275 lbf (41.26 kN) thrust each Main rotor diameter: 62 ft 0 in (18.9 m) Main rotor area: 3,019 sq ft (280.5 m2) Performance

Maximum speed: 300 kn (350 mph, 560 km/h)

Illustrations

Worked examples

Example 1 — a first encounter with Sikorsky S-72

Start with the simplest possible case. Write down what Sikorsky S-72 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, 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 Sikorsky S-72 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 Sikorsky S-72 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 Sikorsky S-72

In research: Sikorsky S-72 appears in chemistry 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 Sikorsky S-72 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: Sikorsky S-72 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1980s United States experimental aircraft, 1980s United States helicopters, Aircraft first flown in 1976, so understanding it makes those chapters shorter.
In everyday life: Look for Sikorsky S-72 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 Sikorsky S-72 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Sikorsky S-72 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 Sikorsky S-72 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sikorsky S-72 in simple terms?

Why does Sikorsky S-72 matter?

Because it connects several chemistry 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 Sikorsky S-72?

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 Sikorsky S-72.