Name: P-47 Thunderbolt 的疯狂工程（The Insane Engineering of the P-47 Thunderbolt）
Uploaded: 2021-06-02T02:50:26.000Z
Duration: 18 min 19 s
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關係子句

Earlier this month I posed this question to my twitter followers. Was the P-47 Thunderbolt

one of the best planes of World War 2? And 35% of my audience said, no. So, in today's

video I am going to explain why I disagree with 35% of my audience.

As we will see over the course of this video, the P-47 had it's flaws, but by the time

the P-47D-25, easily identified by its distinctive bubble canopy, entered service in the spring

of 1944, the P-47, in my opinion, was an excellent plane that was instrumental to the success

The P-47s reputation may have been a victim of its image. It's not sleek and aerodynamic

looking like the Spitfire or P-51 Mustang. It lacks the stylish gullwing of the F4U Corsair

and has never gained the infamy of the Stuka.

The plane is unusually….thicc? Seeing images of it's crew standing next to their planes

really demonstrates how huge the fuselage was. The crew of this P-47 clearly agreed.

They painted the word chunky onto the engine cowl. But if you are like me, this should

indicate to you that there was something unique about the plane, that the designers tried

something different. The best way to illustrate this is through a size comparison.

This is the P-51 Mustang. It's a streamlined, athletic looking plane...and this is the P-47.

You could have literally fit a P-51 inside the P-47 with room to spare. It simply doesn't

look the part, but what if I told you it's frame was purpose built to fit one incredibly

Just as its namesake, the A-10 Thunderbolt II, was built around it's gun, it's ancestor

was built around it's colossal engine. The massive Pratt and Whitney R-2800 Double Wasp.

A two row, 18 cylinder air-cooled radial engine with a massive displacement of 46 litres.

[1] The Merlin engine of the Spitfire and P-51 Mustang for comparison, one of the most

commonly used Allied engines of WW2, was 27 litres.

And this is just the powerplant, the P-47 was also fitted with a supercharger that took

up a significant volume of the aft fuselage, and this gave the P-47 some incredible high

This shows the basic layout of the engine and supercharger inside the P-47 fuselage.

[2] The P-47 had a massive air intake just underneath the engine, big enough for a man

to fit in. The air from this intake was not immediately funnelled into the engine, instead

it was routed to the back of the plane first. Where it split into two ducts. One flowed

into a supercharger impeller, which compressed the air and returned it to the engine carburetor,

while the secondary duct flowed into an intercooler to cool the air from the compressor section

which had heated up as a result of the compression.

Ofcourse, this compressor section needed to be powered. This was done through hot energised

exhaust which was collected from the engine through this collection ring in a separate

duct system. This air was funnelled to a lower turbine section of the supercharger before

the hot exhaust was vented to the atmosphere here.

At lower altitudes less of this energised exhaust made it to the supercharger, as there

are two gated exhaust nozzles on either side of the plane that gradually closed as the

This ensured the R-2800 double wasp was supplied with plenty of cold compressed air even at

27,000 feet, where other planes could not funnel enough of the oxygen needed to achieve

This wasn't the only trick the P-47 had up it's sleeve.

P-47D-4 variants and onward were fitted with a 30 gallon tank filled with an alcohol water

mixture located between the pilot and the engine in the firewall.

In times of emergency this mixture could be injected into the engine. This gave short

bursts of additional horsepower, taking the engine from it's already massive 2,000 horsepower

So how does spraying water into an engine increase horsepower? The water isn't fuel

and it displaces some air entering the engine surely. Your immediate thought would be that

this reduces horsepower. To boot, water is corrosive and incompressible, which could

Water injection increases horsepower in two ways. Both as a result of water's cooling

effects. When water is injected into the engine it absorbs heat from the air and engine in

the process of evaporating. This increases engine pressure and lowers the temperature

of the piston. [3] Colder air is denser, and thus more air/fuel mixture is carried into

the piston with each stroke, increasing the energy released in each power stroke. The

evaporation also cools hotspots in the engine that can cause pre-ignition of the air-fuel

mixture. Meaning the air fuel mixture ignites before the piston is at the bottom of it's

compression stroke and thus is working against the power strokes in the other cylinders,

The limited water supply meant this power boost was saved for emergency use only, but

emergencies are the exact time a little boost in horsepower is needed. Whether that is climbing

a little faster to regain an altitude advantage after a diving attack, taking off with a little

extra weight, or simply speeding away from an aggressor.

With all these design features, the P-47 was a fast plane with few planes being able to

match it's high altitude performance. Early versions of the P-47 did suffer from poor

climb and turning performance. That massive engine added a great deal of weight, and by

virtue of the large fuselage needed to hold it, a great deal of parasitic drag too. In

order to climb or turn, the engine and wings needed to provide the force necessary to lift

the plane to higher altitude or shift it's direction.

These characteristics did not affect the P-47s roll rate however, where it excelled thanks

to fantastic aileron control. [10] However, in a dog fight being outturned or out climbed

Climb rates were improved for the P-47D-22 and onward with the addition of a new larger

propellor, a 4 metre diameter propellor nicknamed the paddle prop. It had a longer chord and

distinctive cuffs which helped channel more air into the engine.

This new prop made the climb rate disadvantage marginal, surprising German pilots who had

become accustomed to pulling up sharply to evade P-47s. [1]

So the P-47, wasn't the best out and out fighter. Surely that supercharger gave it

excellent high altitude performance, making it the perfect bomber escort. Yes and no,

because of another design flaw it's range was lackluster.

The huge fuselage and engine made the P-47 a thirsty plane. It's fuel tanks were always

going to struggle to feed this hungry engine. The plane could carry 305 gallons in two tanks

located around the cockpit. [4] The main L shaped tank located in front of and below

the pilot could hold 205 gallons, while the secondary tank located below and behind the

pilot could carry an additional 100 gallons.

These tanks gave the pilot between an hour and a half and 2 hours of flight time and

only just 50 extra miles of range over the spitfire, a notoriously short range fighter.

The spitfire was primarily designed as an interceptor to protect British Airspace, the

P-47 was not designed for this purpose and it's lack of range frustrated bomber crews

who relied on it's protection. The pilot's of the Luftwaffe were perfectly aware of the

P-47's range issues and often waited for the pilots to turn for home before launching

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P-47 Thunderbolt 的疯狂工程（The Insane Engineering of the P-47 Thunderbolt）

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