engineering

Tokyo tanks

Tokyo tanks 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 Tokyo tanks rather than just read about it. In short: Tokyo tanks were internally mounted self-sealing fuel tanks used in the Boeing B-17 Flying Fortress and Consolidated B-24 Liberator bombers during World War II. The tanks increased the B-17's total range at combat weight with 4,000–5,000 pounds (1,800–2,300 kg) of bombs by about 1,000 miles (1,600 km) and the combat radius was doubled to about 650 miles (1,050 km).

Key takeaways

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

Reference excerpt

Tokyo tanks were internally mounted self-sealing fuel tanks used in the Boeing B-17 Flying Fortress and Consolidated B-24 Liberator bombers during World War II. The tanks increased the B-17's total range at combat weight with 4,000–5,000 pounds (1,800–2,300 kg) of bombs by about 1,000 miles (1,600 km) and the combat radius was doubled to about 650 miles (1,050 km). Although nicknamed "Tokyo" tanks, the name was hyperbole, as no B-17 had the range to bomb Japan from an allied base during the war.

Description These fuel tanks consisted of 18 removable containers, called cells, made of a rubberized compound, installed inside the wings of the airplane, nine to each side. The wings of the B-17 consisted of an "inboard wing" structure mounted to the fuselage which held the engines and flaps, and an "outboard wing" structure joined to the inboard wing and carrying the ailerons. The Tokyo tanks were installed on either side of the joint (a load-bearing point) where the two wing portions were connected. Five cells, totaling 270 US gallons (1,000 L) capacity, sat side by side in the outboard wing and were joined by a fuel line to the main wing tank, which delivered fuel to the outboard engine. The sixth cell was located in the space where the wing sections joined, and the remaining three cells were located side-by-side in the inboard wing; these four cells delivered 270 US gallons (1,000 L) of fuel to the feeder tank for the inboard engine. The same arrangement was repeated on the opposite wing. The Tokyo tanks added 1,080 US gallons (4,100 L) of fuel to the 1,700 US gallons (6,400 L) already carried in the six regular wing tanks. 820 US gallons (3,100 L) could be carried in an auxiliary tank that could be mounted in the bomb bay, for a combined total of 3,600 US gallons (14,000 L). All B-17F aircraft built by Boeing from Block 80, by Douglas from Block 25, and by Vega from Block 30 were equipped with Tokyo tanks, and the entire run of B-17Gs by all three manufacturers had Tokyo tanks. B-17s with factory-mounted Tokyo tanks were first introduced to the Eighth Air Force in England in April 1943 with the arrival of the 94th Bomb Group and 95th Bomb Group, equipped with new aircraft. By June 1943, aircraft that were so equipped began to appear in greater numbers as replacement aircraft and with new groups moving to England. Beginning in July 1943, all replacement aircraft that did not have the tanks already installed were equipped before issue. Use of the term "Tokyo tanks" appeared in American newspapers by mid-November 1943, in a first-person account of a bombing raid authored by Beirne Lay Jr., then a lieutenant colonel in the United States Army Air Forces. Although the tanks were removable, this could only be done by first removing the wing panels, and so was not a routine maintenance task. A drawback to the tanks was that there was no means of measuring remaining fuel quantity within the cells. Fuel was moved from the cells to the engine feeder tanks by opening control valves within the bomb bay so that the fuel drained by gravity. Although the tanks were specified as self-sealing, vapor buildup within partially-drained tanks made them explosive hazards in combat, such as when struck by flak or cannon shells.

Sources Bishop, Cliff T. (1986). Fortresses of the Big Triangle First. East Anglia Books. pp. 50–51. ASIN B002CEJICS. ISBN 1-869987-00-4.

References

Illustrations

Worked examples

Example 1 — a first encounter with Tokyo tanks

Start with the simplest possible case. Write down what Tokyo tanks 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 Tokyo tanks 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 Tokyo tanks 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 Tokyo tanks

In research: Tokyo tanks 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 Tokyo tanks 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: Tokyo tanks is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aerospace engineering, Aircraft fuel system components, Fuel containers, so understanding it makes those chapters shorter.
In everyday life: Look for Tokyo tanks 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 Tokyo tanks in 20 minutes

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

Frequently asked questions

What is Tokyo tanks in simple terms?

Why does Tokyo tanks 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 Tokyo tanks?

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 Tokyo tanks.