science

Saab 21R

Saab 21R 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 Saab 21R rather than just read about it. In short: The Saab 21R was a Swedish fighter/attack aircraft developed and produced by Svenska Aeroplan AB (SAAB). It was a jet-powered development of the piston-engined SAAB 21 and was the first jet aircraft to be produced by Saab.

Key takeaways

Saab 21R belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Saab 21R to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Saab 21R from memory before moving on to harder problems.

Reference excerpt

The Saab 21R was a Swedish fighter/attack aircraft developed and produced by Svenska Aeroplan AB (SAAB). It was a jet-powered development of the piston-engined SAAB 21 and was the first jet aircraft to be produced by Saab. The R-suffix stands for reaktion (reaction), referencing reaktionsdrift (jet power) or reaktionsmotor (jet engine). Along with the Soviet Yakovlev Yak-15, the 21R was one of only two jet fighters to have been successfully converted from piston-powered aircraft. Sweden was under threat during the Second World War, and ordered SAAB to develop an advanced fighter. The result was an unorthodox twin-boom pusher, with a low wing, tricycle landing gear, and a heavy forward-firing armament. Several options were then explored to improve its performance, leading to a jet-powered version. During 1947, SAAB began converting the piston-engined J 21s to jet propulsion, which required extensive modifications. One hundred twenty-four aircraft were planned, however this number was reduced to 64 and they were instead mainly used as fighter-bombers. It saw service in the late 1940s and early 1950s before it was replaced by a new generation of fighters designed from the onset with jet propulsion, such as the de Havilland Vampire and the Saab 29 Tunnan.

Design and development

Background During the early stages of the Second World War, Sweden was concerned that its neutrality and its independence could be threatened by one of the belligerent powers, and so enacted a series of emergency measures to increase its military's preparedness and deterrence value against potential aggressors. Between 1939 and 1941, the Swedish Air Force committed itself to a major expansion programme, which included the procurement of large numbers of foreign and locally developed fighters. As a consequence of the conflict, few nations possessed available production capacity or a willingness to supply modern fighters to Sweden, being a relatively small neutral country. While Sweden's own domestic production capability would be insufficient until at least 1943, Sweden would have to develop its own first-rate designs to meet its needs. In 1941, in response to Swedish Air Force requirements, the Swedish aviation company SAAB commenced work on a radical new fighter. The company envisioned an unorthodox twin-boom pusher configuration fighter aircraft, featuring a low wing, a tricycle landing gear, and with a heavy forward-firing armament. It was powered by a licensed version of the new German Daimler-Benz DB 605B inline piston engine, which was refined and built by Svenska Flygmotor AB. The Swedish Air Force designated it the J 21, and a prototype was flown on 30 July 1943.

By 1945, options were being explored to improve its performance. Many of these involved the substitution of the 605B engine with a more powerful powerplant. During the first half of the year, a variant was planned with a 2,000 hp (1,500 kW) Rolls-Royce Griffon engine which would have raised the top speed to 416 mph (669 km/h). Other projects, such as the SAAB 27, were intended to use the Griffon as well, but by the end of the year, all work on the piston-engine design was abandoned. In parallel with the piston-engine studies, SAAB and other Swedish companies had been evaluating a new type of engine - the jet engine. Two early studies, RX 1 and RX 2, had been studied, both of which being twin-boom aircraft similar to the 21. Recognising the Swedish Air Force's enthusiasm for a jet-powered aircraft for late 1945, SAAB decided to produce a version of the 21 harnessing jet propulsion. A design study was initiated for converting the J 21A to jet power. It was recognized that Sweden would otherwise be left behind while nations such as the United Kingdom already had the Gloster Meteor and de Havilland Vampire in production. The design study was proceeding in late 1945 despite no specific engine having been chosen, but the opportunity came up to purchase a license to manufacture the "Goblin 2" turbojet engine in Sweden. This was the first jet engine to be used by the Swedish Air Force, who designated it as the RM1. The first flight of Saab's first jet aircraft, a converted J 21, was on 10 March 1947, powered with a single Goblin 2 engine. The results of the flight test programme were largely satisfactory.

Conversion programme

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Saab 21R

Start with the simplest possible case. Write down what Saab 21R 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 Saab 21R 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 Saab 21R 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 Saab 21R

In research: Saab 21R 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 Saab 21R 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: Saab 21R is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1940s Swedish fighter aircraft, 1950s Swedish attack aircraft, Aircraft first flown in 1947, so understanding it makes those chapters shorter.
In everyday life: Look for Saab 21R 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 Saab 21R in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Saab 21R 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 Saab 21R out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Saab 21R in simple terms?

Why does Saab 21R 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 Saab 21R?

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 Saab 21R.