science

Operation Sigma Sigma

Operation Sigma Sigma 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 Operation Sigma Sigma rather than just read about it. In short: The Sigma is an experimental glider developed in Britain from 1966 by a team led by Nicholas Goodhart. After disappointing performance during flight testing the Sigma was passed on to a Canadian group which carried out modifications, making the Sigma more competitive.

Key takeaways

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

Reference excerpt

The Sigma is an experimental glider developed in Britain from 1966 by a team led by Nicholas Goodhart. After disappointing performance during flight testing the Sigma was passed on to a Canadian group which carried out modifications, making the Sigma more competitive.

Design and development Designed to compete in the 1970 World Gliding Championships, the team aimed to develop a wing that would climb well through a high lift coefficient and a large wing area, but equally had the "maximum possible reduction of area for cruise at low lift coefficients". At the same time for the minimum possible drag they aimed for "extensive" laminar flow. To achieve this they employed flaps that would alter both wing area and wing camber. Based on analysis of the nature of thermals encountered in cross-country flying, they reasoned that by having a slow turning circle, their sailplane could stay close to the central (and strongest) part of the thermal and gain maximum benefit. Its unusual feature is its ability to vary its wing area using Fowler flaps. It had been tried before by the Hannover Akaflieg in 1938 with their AFH-4, the South African Beatty-Johl BJ-2 Assegai and the SZD Zefir gliders. Operation Sigma Ltd. was formed, attracting sponsorship from Hawker Siddeley and assistance from eminent aerodynamicists, and construction of a prototype was started at the Slingsby Kirbymoorside factory. A fire at the Slingsby factory in 1968 destroyed the prototype, which was nearing completion. Slingsby Sailplanes Ltd. soon went into receivership after the disastrous fire so the remaining prototype Sigma Type C was relocated to the British European Airways workshops at London Heathrow Airport (LHR). After completion it eventually flew for the first time on 12 September 1971 at the College of Aeronautics, Cranfield. The wings and tail boom are of aluminum alloy construction and the front of the fuselage is glass-fibre composite, with a welded steel tube centre-section connecting the fuselage components and wings. Other equipment fitted include a retractable main wheel, speed limiting air brakes and a tail parachute housed in a compartment in the rudder. The hydraulically actuated flaps increased the wing area to 177 square feet (an increase of 35%), lowering the wing loading and stalling speed (37 knots), allowing the desired tight circling when thermalling. The hydraulic pressure needed to move the flaps was provided by the pilot pumping on the rudder pedals, this proving to be tiring, not to mention that moving the flaps in flight was found to be almost impossible due to bending in the wings. Performance testing revealed a disappointing best L/D of 41:1 and the project was wound up in 1977. The group offered the Sigma up to further development by other parties, selecting a proposal by David Marsden a professor of mechanical engineering at the University of Alberta (on sabbatical at Cranfield Institute of Technology and a glider pilot holding records with his own glider designs such as the Marsden Gemini). The aircraft was moved to Canada in 1979 by Marsden, modified with a new flap system, conventional ailerons in lieu of outboard flap sections and the tail parachute was removed from the rudder. Despite the glide ratio only increasing to 47:1, its good climb rate made it competitive with contemporary Open Class gliders of the time, breaking the US 300 km triangle record in 1997 at 151 km/h (82 kn).

Variants Data from:British Gliders and Sailplanes 1922-1970

Sigma Type A This version was under construction at the Slingsby factory at Kirbymoorside in 1969 when they were completely destroyed in the 1969 Slingsby factory fire. Sigma Type B A version differing in detail from the Type A, not completed. Sigma Type C After the fire the project was taken on by Operation Sigma Ltd., ostensibly to supply a world beating sailplane for the World Gliding Championships. Of similar outline, shape and size to the original prototypes, the Type C was completely revised in detail, but retained the construction methods of the earlier aircraft. (Marsden) Sigma The Sigma after modification in Canada by David Marsden.

Specifications (before Marsden conversion) Data from Sailplanes 1965-2000General characteristics Crew: 1 Length: 28 ft 11 in (8.81 m) Wingspan: 68 ft 11 in (21 m) Wing area: 131 sq ft (12.2 m2) (flaps retracted) 16.5 m2 (177.60 sq ft) (flaps extended) Aspect ratio: 36.2(flaps retracted) 26.8 (flaps extended) Airfoil: Wortmann FX-67-Σ136-017 Empty weight: 1,338 lb (607 kg) Max takeoff weight: 1,550 lb (703 kg) Performance

Maximum glide ratio: 41:1 as completed (47:1 with Marsden modifications) Rate of sink: 126.6 ft/min (0.643 m/s) (1.25 kts)(flaps retracted) 151 ft/min (1.5 kts) (0.772 m/s) (flaps extended) Wing loading: 11.8 lb/sq ft (57.6 kg/m2) (flaps retracted) 42.6 kg/m2 (8.725 Lb/sqft) (flaps extended)

Notes

References Simons, Martin (2005). Sailplanes 1965-2000 (2nd revised ed.). Königswinter: EQIP Werbung & Verlag GmbH. ISBN 3 9808838 1 7. Goodhart, N (27 March 1969), "Sigma—design of a super-glider", Flight International

External links Photograph - Sigma

Worked examples

Example 1 — a first encounter with Operation Sigma Sigma

Start with the simplest possible case. Write down what Operation Sigma Sigma 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 Operation Sigma Sigma 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 Operation Sigma Sigma 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 Operation Sigma Sigma

In research: Operation Sigma Sigma 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 Operation Sigma Sigma 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: Operation Sigma Sigma is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1970s British sailplanes, Aircraft first flown in 1971, Glider aircraft, so understanding it makes those chapters shorter.
In everyday life: Look for Operation Sigma Sigma 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 Operation Sigma Sigma in 20 minutes

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

Frequently asked questions

What is Operation Sigma Sigma in simple terms?

Why does Operation Sigma Sigma 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 Operation Sigma Sigma?

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 Operation Sigma Sigma.