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#4545680 - 11/21/20 05:39 PM The guts of a P-47.  
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Thought you guys might like to see the internals of the P-47. I never knew the Supercharger was this big.

https://lynceans.org/all-posts/the-complexity-of-a-ww-ii-p-47-thunderbolts-powerplant/


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#4545683 - 11/21/20 06:31 PM Re: The guts of a P-47. [Re: Timothy]  
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Yeah I never understood the value of that added complexity and vulnerability, as tough as a P-47 was the supercharger is in a perfect place to be shot full of holes. That would not necessarily cause a loss of the aircraft but it would ruin it's combat performance.

The F4U had the same basic engine as the P-47 (P&W R2800) and it's mechanically driven supercharger was mounted just behind the engine with the intercoolers being in the inboard section of the wing. A much simpler and more compact arraignment.

I know the P-47 had better high altitude performance than the Corsair but that was due to the gearing of the supercharger it used, not the location. Bf109's and Fw190D's had mechanically driven superchargers like the Corsair and they operated well at high altitude.


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#4545686 - 11/21/20 07:09 PM Re: The guts of a P-47. [Re: Timothy]  
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You get *a lot* more power from the P47 installation than from that in the FG1/F4U

At 34,000 ft, the P47 is still producing 1575 HP, with 2000 being available all the way from the ground to 27,800ft and 429mph
F4U gets the same power only to 18,000ft, and by 23,300 ft power available is 1495 HP and speed is 390mph

The bulk and weight of the P47 does limit low altitude climb performance somewhat, and provides for a slightly lower (power limited) low altitude performance in speed, but this is more than compensated for by it's ability to generate power at altitude.

The FW190D9 had a full-throttle height of ~20,200ft and 413mph as a point of context for 'great high altitude performance' of a high altitude modified FW - slightly better than the F4U and lower than the P47 by quite a bit.

#4545688 - 11/21/20 07:21 PM Re: The guts of a P-47. [Re: Timothy]  
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#4545689 - 11/21/20 07:37 PM Re: The guts of a P-47. [Re: Timothy]  
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I also forgot... A turbo charger produces a smooth transition of power with altitude, retaining full power over it's critical altitude... while a geared mechanical supercharger produces maximum power only at the critical altitude of each stage, and has to sacrifice power both above and below this mechanical maximum - the characteristic 'sawtooth' performance envelope.

This can produce a very localised 'advantage' to both adversaries if they have similar power but different gear ratios... but for power, both will be equalled or beaten at every altitude for a turbo charged installation - at a penalty in bulk and complexity. The P38 manages a turbo supercharger and excellent high altitude performance - but also at the cost of size and complexity, and an aerodynamic and structural penalty around dive performance and recovery.

#4545690 - 11/21/20 08:13 PM Re: The guts of a P-47. [Re: Lieste]  
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Originally Posted by Lieste
You get *a lot* more power from the P47 installation than from that in the FG1/F4U

At 34,000 ft, the P47 is still producing 1575 HP, with 2000 being available all the way from the ground to 27,800ft and 429mph
F4U gets the same power only to 18,000ft, and by 23,300 ft power available is 1495 HP and speed is 390mph

The bulk and weight of the P47 does limit low altitude climb performance somewhat, and provides for a slightly lower (power limited) low altitude performance in speed, but this is more than compensated for by it's ability to generate power at altitude.

The FW190D9 had a full-throttle height of ~20,200ft and 413mph as a point of context for 'great high altitude performance' of a high altitude modified FW - slightly better than the F4U and lower than the P47 by quite a bit.



I know wink

But... a mechanically driven supercharger can be setup to deliver smooth boost, the Bf109 had a drive setup that allowed this. The Corsair also only a 2 speed supercharger, with a 3rd gear what would it's 25k altitude performance have been? I don't know but it bears thinking about. But the Corsair was never intended for very high altitude performance so it had what it had.

I know there were good reasons for the P-47 systems to be as it was, but I also believe there were other means to achieve the same or similar results with less complication etc.


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#4545691 - 11/21/20 08:44 PM Re: The guts of a P-47. [Re: Timothy]  
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The 109 still has a 'step' in it's power curve, and speed with altitude, as the second stage is introduced by the automatic compensator.
It also usually had performance closer to that of the F4U, rather than the P47 in terms of altitude performance, apart from a few specialist models from the late war.

#4545692 - 11/21/20 09:55 PM Re: The guts of a P-47. [Re: Timothy]  
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The P-47's setup might be bulky, but is it really more complex than its contemporaries?

I would think it would somewhat easier to service given that every component isn't squeezed into a relatively small volume, and all that extra mass and volume might be contribute to the aircraft's toughness?

#4545720 - 11/22/20 09:32 AM Re: The guts of a P-47. [Re: Timothy]  
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The main difference between a turbocharger and a supercharger is the supercharger, being mechanically driven off the engine, takes engine power to make power for the engine. Turbochargers are driven by exhaust and for all intents and purposes provide free power, with no parasitic losses. Their one drawback is turbo lag, the delay between acceleration and boost production due to inertia in the turbine & impeller wheels. Smaller turbos have less lag but make less power, larger turbos produce more power but lag is more noticeable. Sequential turbos - a smaller turbo driving a larger one - reduce lag but at the expense of greater complexity. Remote-mounted turbos also have the problem of the exhaust cooling down by the time it reaches the turbo, producing less power.


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#4545727 - 11/22/20 10:10 AM Re: The guts of a P-47. [Re: semmern]  
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Originally Posted by semmern
...and don’t try to dive to get away from one smile


RAF Spitfire pilot on sighting this behemoth for the first time: "Good grief; how do you take evasive action in that? Run around the cockpit?"



#4545736 - 11/22/20 02:59 PM Re: The guts of a P-47. [Re: Timothy]  
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They are in fact huge. I was in awe the first time I stood next to a P-47 (N model).

edit: especially considering I had flown down to ogle it in a Cessna-150.

Last edited by Nixer; 11/22/20 03:00 PM. Reason: More stuff


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#4545752 - 11/22/20 07:09 PM Re: The guts of a P-47. [Re: NH2112]  
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Originally Posted by NH2112
The main difference between a turbocharger and a supercharger is the supercharger, being mechanically driven off the engine, takes engine power to make power for the engine. Turbochargers are driven by exhaust and for all intents and purposes provide free power, with no parasitic losses. Their one drawback is turbo lag, the delay between acceleration and boost production due to inertia in the turbine & impeller wheels. Smaller turbos have less lag but make less power, larger turbos produce more power but lag is more noticeable. Sequential turbos - a smaller turbo driving a larger one - reduce lag but at the expense of greater complexity. Remote-mounted turbos also have the problem of the exhaust cooling down by the time it reaches the turbo, producing less power.



Turbos also tend work better with more cylinders, and thus exhaust pulses, feeding them.

Having at least 4 more cylinders than comparable engines of the time, plus that long straight intake path which probably contributes to a substantial ram air effect, both probably go a long way towards the power losses of the remote mounted turbo.

#4545782 - 11/23/20 01:52 AM Re: The guts of a P-47. [Re: Timothy]  
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The P-47 looks like a flying HVAC system to me now.

#4545783 - 11/23/20 02:04 AM Re: The guts of a P-47. [Re: Timothy]  
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Took my wife to the planes of Fame museum at Flying Cloud airport back in early 90s when they were still here. We
walking between hangers and they had P-47 pulled out between them and were just starting it. OMG, when that thing
get going, Talk about LOUD. we were both temperately deaf from it. They also had the engine cowling removed and
must have been working on it. It was pouring oil out when it shut down.


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#4545791 - 11/23/20 04:21 AM Re: The guts of a P-47. [Re: Timothy]  
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The P-47 cockpit is one of the very few WW 2 fighter cockpits I think I could actually fit into.


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#4545825 - 11/23/20 04:46 PM Re: The guts of a P-47. [Re: Timothy]  
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I've always like the Jug but never knew any of the engineering that went into until a few weeks ago. This Youtube video popped up in my recommendations. It talks a lot about the pros and cons of it's design. Excellent video on the subject.

The Insane Engineering of the P-47 Thunderbolt

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#4545831 - 11/23/20 05:18 PM Re: The guts of a P-47. [Re: Wizard43]  
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If you want more vids there's 8 really good technical ones on the jug here

https://www.youtube.com/channel/UCynGrIaI5vsJQgHJAIp9oSg/videos


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