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P-47s at the Evansville factory. Check out the latest restoration progress on the Dakota Territory Air Museum's P-47D Thunderbolt at AirCorps Aviation. (photo, courtesy of Harold Morgan Collection)
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Warbird Digest has just received the April, 2020 report from Chuck Cravens concerning the restoration of the Dakota Territory Air Museum’s P-47D Thunderbolt 42-27609 at AirCorps Aviation in Bemidji, Minnesota. We thought our readers would be very interested to see how the project has progressed since our last article on this important project. So without further ado, here it goes!
While the essential measures which AirCorps Aviation has taken this month to protect employees from the Coronavirus outbreak have slowed progress on the P-47, they haven’t halted it. One consequence, however, was that we weren’t able to conduct our usual photo shoot to capture images as work took place. Thankfully, one of our expert technicians, Aaron Prince, did take some photos to document what he has been doing. Therefore this month’s update will consist mainly of detailed images of fuselage wiring, instrument panel work, and the armor plate installation.
We will also review the historical changes to the Thunderbolt’s design that first started appearing on the P-47D-23 variant (the kind we have under restoration).
Armor Plate
This is the armor plate behind the pilot. While normally made of face-hardened steel, the restoration will employ aluminum due to the weight savings it offers. (photo via AirCorps Aviation)The armor has been painted and stencils applied. (photo via AirCorps Aviation)
Instrument Panel
Aaron did a great deal of work on the complex instrument installation in the cockpit panel this month.
This is a wide angle image of the cockpit. (photo via AirCorps Aviation)
Instruments have been mounted in the mockup panel to plumb and wire. (photo via AirCorps Aviation)
Aaron has started the wiring. (photo via AirCorps Aviation)
This assembly distributes vacuum to the various gauges. (photo via AirCorps Aviation)
The plumbing is completed except for flexible lines and some of the wiring. (photo via AirCorps Aviation)
Using historically accurate wire is an important detail for an authentic restoration. (photo via AirCorps Aviation)
The vacuum distribution assembly has been mounted to horizontal gyro. (photo via AirCorps Aviation)
Wiring
The P-47 has unusually complex wiring for a WWII era fighter, because of the need to control the turbo supercharger in addition to regular instrument and control systems. This P-47 also had several components moved from their standard position as part of the field modifications involved with installing the ‘Christmas tree’ auxiliary fuel tank just behind the cockpit.
Here we have an original
cannon plug and a plug being restored. Aaron was able to solder cannon plugs at home. (photo via AirCorps Aviation)
Shown here is the wiring for the intercooler door motor, and limit switches for intercooler doors. (photo via AirCorps Aviation)
The radio junction box is one of the components that was moved as part of the Christmas tree tank field modification. Here we see it mounted in its relocated position on the radio shelf support. (photo via AirCorps Aviation)
This is the downlock microswitch for the tail wheel in the landing gear circuit. (photo via AirCorps Aviation)
Here’s the uplock microswitch for the tail wheel. (photo via AirCorps Aviation)
This is a terminal block for the aft electric at station 180. It is mounted on a structure original to the airframe. It was moved from the position shown on Republic engineering drawings as part of the Christmas tree tank field modification. (photo via AirCorps Aviation)
The turbo supercharger oil tank mounted in its relocated position. The bracket and tank panel are original to airframe. Also visible is the auxiliary tank fuel vent line (indicated by a red band). (photo via AirCorps Aviation)
The battery junction box is mounted on the firewall. (photo via AirCorps Aviation)
A view of the firewall shows the generator junction box (bottom) and voltage regulator
box (top). The water injection pump is also visible to the left of the generator junction box. (photo via AirCorps Aviation)
This duct is the air intake to the carburetor from the turbo supercharger. (photo via AirCorps Aviation)
This is the oxygen bottle tank bracket prior to breakdown and cleanup (original to airframe).. (photo via AirCorps Aviation)
Here is a view looking forward from tail. Note part of the turbo is in place, and that the X-mas tree housing with turbo supercharger oil tank is mounted in the relocated position. (photo via AirCorps Aviation)
The oxygen bottle tank bracket is clecoed in its relocated position after inspection and cleaning. (photo via AirCorps Aviation)
D-23 Changes
The P-47D-23 was the last of the Razorback Thunderbolts.
Both the Evansville, Indiana-built P-47D-23 and the all-but identical P-47D-22, which rolled off Republic’s Farmingdale, New York production line, incorporated several changes over previous models. The most visible difference was that both new variants now used 13 foot diameter paddle-blade propellers. The D-22 employed a Hamilton Standard Hydromatic 24E50-65 propeller, while the D-23 used a Curtiss Electric C542S. Interestingly, Curtiss Electric propellers used both symmetrical and asymmetrical blade shapes.
The new 13 foot paddle blade props were designed to take full advantage of the increased power available with water injection. However, they had the disadvantage of leaving only 6 inches of ground clearance on landings and take-offs.
The P-47’s rate of climb wasn’t an initial strong point in its performance envelope, so the 400 feet per minute gained with the paddle blade props was a definite improvement.
These are Pacific theater P-47 D-23s with the Curtiss Electric asymmetrical paddle blade props. (USAAF photo)
. (image via AirCorps Aviation)
42-27615 is a P-47D-23 that was on the same carrier as our restoration P-47. It appears to have the Curtiss Electric symmetrical blade prop. (USAAF photo)
Curtiss Electric symmetrical paddle blade blade. (image via AirCorps Aviation)
The propeller boss on the P-47D-22 with the Hamilton Standard paddle blade prop is noticeably blunter and shorter than the one on the Curtiss Electric prop. (Photo Wikimedia Commons)
Drawing of a Hamilton Standard paddle blade prop. (image via AirCorps Aviation)
Another important improvement to the D-23 was the addition of a bullet-proof windshield and jettison-able cockpit enclosure; pulling a ring on the right, forward edge of the canopy pushed the cockpit enclosure back far enough for the slipstream to catch onto it and rip the frame off the Thunderbolt. The D-22/D-23 also had increased fuel capacity.
And that’s all for this month. We wish to thank AirCorps Aviation, Chuck Cravens (words and images) as well as Aaron Prince (images) for making this report possible! We look forwards to bringing more restoration reports on progress with this rare machine in the coming months, although it will likely be some time before we can do so given how the present pandemic has suspended almost all non-essential activities around the globe at the moment. Be safe, and be well!
Richard Mallory Allnutt's aviation passion ignited at the 1974 Farnborough Airshow. Raised in 1970s Britain, he was immersed in WWII aviation lore. Moving to Washington DC, he frequented the Smithsonian’s National Air & Space Museum, meeting aviation legends.
After grad school, Richard worked for Lockheed-Martin but stayed devoted to aviation, volunteering at museums and honing his photography skills. In 2013, he became the founding editor of Warbirds News, now Vintage Aviation News. With around 800 articles written, he focuses on supporting grassroots aviation groups.
Richard values the connections made in the aviation community and is proud to help grow Vintage Aviation News.
