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Thunderbolt

Weapons Loads

With the default weapons loads, the Gross Weight of the P-47D-23 for CFS would be 13,497 pounds which is about 85 pounds below the gross weight of the actual aircraft. The difference is accounted for by partial loads of Engine Oil and Anti-Detonant which would be consumed during the flight but are not accounted for in the disposable loads.

With full ammunition, bombs, and rockets, the maximum take-off weight of 17,400 pounds may be exceeded by around 500 pounds.
At maximum take-off weight, the island airstrip that is typically used for testing gets to be a bit short even with flaps and emergency power.

Screenshot shows a low pass by the aircraft currently being used for testing.

- Ivan.
 

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The P-47D-25 is back in the Workshop after a fairly long break.
The most recent work has been to add a couple extra pieces and redo the animation of the Main Gear.

The First Screenshot shows the final sequence as the Gear Doors close.
The Second Screenshot shows the internal Canopy Frame before it has been flipped inside out.
Note that in this screenshot, the Component is "Sharp".
The highlights got a bit distracting and they were even worse from an interior view, so in the "final" version, they were made "Smooth".

The Third and Fourth Screenshots show the interior view of the Canopy Frame after it has been flipped.
The shapes are passable, but still not completely right, so there may be yet another version shortly.

-------
 

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Panel Differences

The attached Screenshot shows the Panel I have been using for all Thunderbolts.
The background is obvious for a Razorback aircraft (P-47D-23 and earlier) and needs some changes to look more like what is found in the D-25 and other Bubbletops.

One other feature worthy of note is the Fuel Gauge.
The stock gauge is intended for a Main Tank of about 200 Gallons capacity (actual is 205 Gallons) and Auxiliary Tank of about 100 Gallons capacity.
Although the Aux tank did not change, the Main Tank increased in size from 205 Gallons to 270 Gallons starting with the P-47D-25 series.
A new Fuel Gauge would seem appropriate.

- Ivan.
 

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P-47 Fuel System Differences

The attached diagrams show the differences between the fuel systems in the early and late D model Thunderbolt.
The stock fuel gauge is clearly incapable of reading the larger quantity.


- Ivan.
 

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Attached is a screenshot of the updated panel and fuel gauge (50% fuel load) for the P-47D-25.
The pointer for the Main Tank is slightly below the mark for 150 Gallons which seems appropriate for 135 Gallons.
Actually this panel is being shown on the P-47D-27 which also got an internal Canopy Frame this morning.
It is pretty much the same for all the Bubble Top P-47 with the exception of the P-47N which carried a couple more fuel tanks and gauges for them.

The next steps are to edit the AIR File for Compressibility Effects which were tested on Smilo's Hammer and to build a Propeller Table.
Earlier versions did not have Compressibility Effects that matched the aircraft manual's descriptions.

- Ivan.
 

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Last night I did a bit of engine tuning on the D-25 Thunderbolt.
The general specs are the following:
Military Power is 2000 HP @ 2700 RPM and is available from Sea Level to 27,000 Feet. (52 Inches Hg.)
War Emergency Power is 2600 HP @ 2700 RPM and is available from Sea Level to 25,000 Feet. (64 Inches Hg.)
Achieving this was done with the typical CFS power curve where the power is a bit too low at Sea Level and Maximum altitude and of course a bit too high at medium altitudes which in this case was around 20,000 Feet.

Next step is to build a new propeller for this beast. The propellers for the various Thunderbolts were a little odd. The original "Toothpick" propeller was actually capable of slightly higher maximum speeds but was not nearly as good at using the available power at lower speeds such as for acceleration and climbing. There were at least 4 different "Paddle Blade" propellers. Three are very easy to distinguish in photographs.
So far I have attempted to build Thunderbolts with the Curtiss-Electric Asymmetric Blade (rather poorly) and one version of the Hamilton Standard (This aircraft).

The Thunderbolt had a propeller optimized for higher altitudes and this was a bit too large for the installed power at low altitude. This is reflected by the relatively poor Take-Off performance and low speed acceleration. The stock propeller actually does a pretty fair job of simulating this but of course has the typical issues of all the other stock propellers.

- Ivan.

P47D25_Flightline.jpgThunderboltSpeedRun.jpg
 
There is a pretty radical difference in engine output and performance with and without Water Injection in many of the later model Thunderbolts.
Along with that difference in power output, the power level does not drop off until nearly 30,000 Feet. This combination is a very wide range of conditions for the propeller to handle.
As an example, the Power Coefficient at Take-Off without Water Injection is around 0.105 to 0.110.
At Altitude WITH Wather Injection, Engine Output is up by around 30% and Power Coefficient rises to just over 0.300.

The stock propeller tables do address this to some extent though they have all the strangeness typical of the stock tables.
Attached are the stock Power Coefficient and Efficiency Tables.
Note that the .305 dashed line is the highest power coefficient that this engine / propeller combination will achieve.
Note also that there are curves that will not be reached under power under any circumstances. They might be reached if the engine is run at very very reduced speed.

- Ivan.

P-47D_StockPowerCoefficient.jpgP-47D_StockEfficiency.jpg
 
These are the Propeller Tables for the new Hamilton Standard Paddle Blade propeller. It is intended to mostly mimic the performance of the stock propeller in key places while making adjustments in the necessary places. These tables were done over a week ago but Anna Honey has been on travel and that tends to cut down on my time and increases my workload.

This evening, I put them into the AIR file and tried a few tests. Keep in mind that the first propellers from Ivan's Propeller Shop would not even complete a Take-Off run. This one did a bit better.

Please compare the Propeller Tables of the New Propeller with the Stock Propeller in the Prior Post.
It is hard to believe the two would perform in any way similar by the appearance.

- Ivan.

P-47D_PowerCoefficientV1.jpgP-47D_EfficiencyV1.jpg
 
The D-25 Thunderbolt's initial flight tests were not too far from where I wanted. The only thing that had changed significantly with the new propeller was that the airspeed at which the engine would achieve full RPM was about 20 MPH higher than before. This was fairly easy to correct.

With this aeroplane, there is a pretty significant increase in power when Water Injection (ADI) is used. At Military Power without ADI, there is 2000 HP available which isn't bad, but having an additional 30% more power available with WEP makes things a bit more interesting. The problem with the simulator is that the WEP is of very short duration which meant that it was barely enough for two speed runs.

With the new propeller, here is what I am getting:
Idle speed 497 RPM - Identical to the Stock Propeller
Full RPM is reached at 173 MPH TAS. With the stock propeller, testing showed somewhere between 170 and 175 MPH.

Military Power
Maximum Speed at 500 Feet is 317 MPH on 1910 HP.
Maximum Speed at 30,000 Feet is 412 MPH on 1645 HP
Maximum Soeed at 22500 Feet is 424 MPH on 2335 HP

War Emergency Power
Maximum Speed at 500 Feet is 345 MPH on 2495 HP.
Maximum Speed at 30,000 Feet is 436 MPH on 1978 HP
Maximum Soeed at 22500 Feet is 446 MPH on 2774 HP

Initial Climb Rate with a full fuel load is 2800 FPM at 225 MPH TAS
Initial Climb Rate with Half Fuel Load is 3200 FPM at 225 MPH TAS
Both are with Military Power.
So far, nothing seems really outrageous.

Service Ceiling has not been checked yet.

- Ivan.

ThunderboltNewProp.jpgThunderbolt_ClimbTest.JPG
 
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