Dakota Territory Air Museum – P-47D Restoration Update – September/October 2021

AirCorps Aviation technicians have attached a spare R-2800 engine to the P-47's airframe to enable the trial-fitting of various firewall forward components. (image via AirCorps Aviation)


Warbird Digest has received the September/October, 2021 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!


Update

This month, work on the control surfaces continues; the turbosupercharger system ducting is also progressing nicely. We also reached two exciting milestones in October, fitting the landing gear to the wings and an R-2800 to the engine mount for firewall forward mock up work.

In the history section, we look into the long-range challenges a pilot had to endure on missions lasting as much as 8 hours in a tropical climate.

Control Surfaces

Work on the rudder, flaps, and aileron linkage was a big part of the restoration work this month.

In this image, we see that the rudder structure is now painted and ready for the skins to be permanently attached. (image via AirCorps Aviation)
Work on skinning the rudder continues after the internal structure has come back from the paint shop. (image via AirCorps Aviation)
The flap structure also has been painted and placed back in the fixture for final assembly and skinning. (image via AirCorps Aviation)
The aileron pushrod has been installed. (image via AirCorps Aviation)
Inside the wing, there are connection interfaces between the aileron pushrods and several lever assemblies which carry the linkage from the control stick to the ailerons. (image via AirCorps Aviation)

Main Landing Gear 

The main landing gear assemblies require a great deal of precision fitting to be sure they will function flawlessly. They were fitted, adjusted and installed in October.

Randy examines the main gear wheel well. (image via AirCorps Aviation)
Here is a close-up of the main gear. (image via AirCorps Aviation)
Mark and John check the fit of the right wing’s main landing gear assembly. (image via AirCorps Aviation)
The gun heater tube had to be fastened out of the way while the landing gear work took place. (image via AirCorps Aviation)
Steve is sizing the main landing gear attachment bolt hole. (image via AirCorps Aviation)
This image shows the gear well clearly. (image via AirCorps Aviation)
John and Mark work on the swing of the right gear. (image via AirCorps Aviation)
Mark and Brad work on the free movement on the left main gear. (image via AirCorps Aviation)
Brad and Mark swing the gear up into the retracted position. (image via AirCorps Aviation)
The left main gear is tucked up in the retracted position. (image via AirCorps Aviation)
This is the landing gear in a transition position between retracted and down-and-locked. (image via AirCorps Aviation)
Here is a close-up of the landing gear strut and tire. The rod connecting the lower gear fork and the landing gear box in the wing is the compression rod that reduces the length of the gear strut as the landing gear retracts, allowing it to fit in a shorter wheel well than would otherwise be possible. This allows more room outboard of the gear for the gun and ammo bays. It was the Republic engineers’ solution regarding the problem of fitting four .50 caliber M2 machine guns in each wing. (image via AirCorps Aviation)
The gear is installed in this view of the right wing gear well. (image via AirCorps Aviation)
Mark Tisler worked on fabricating the landing gear doors this month.
(image via AirCorps Aviation)
The basic gear door structure is fitted for skins. (image via AirCorps Aviation)

Induction and Turbosupercharger System Parts

This section of the turbosupercharger system has been nicknamed “the pants” by the guys for its resemblance to a pair of trousers. These passages carry exhaust gases back to the turbosupercharger’s turbine section. (image via AirCorps Aviation)
The large casting is the housing for the bearing which goes between the turbosupercharger’s compressor and turbine sections. The smaller part to the left is the turbosupercharger’s oil pump. (image via AirCorps Aviation)
The carburetor and intercooler air duct is ready for installation. (image via AirCorps Aviation)
This large duct component guides incoming air to the intercooler and turbosupercharger. (image via AirCorps Aviation)
The turbosupercharger regulator adjusts oil pressure to operate the waistgates. (image via AirCorps Aviation)
Here is another view of the turbosupercharger regulator. (image via AirCorps Aviation)
Aaron working on an intercooler duct. (image via AirCorps Aviation)

Firewall Forward

One of this month’s milestones was the trial installation of an engine for mock up purposes. This allowed all of the connecting assemblies to be fitted in readiness for delivery of the airworthy overhauled R-2800.

These are the engine Lord mounts for the Pratt&Whitney R-2800; they will help absorb some of the vibration as the big radial turns 13 feet of Curtiss Electric propellor! (image via AirCorps Aviation)
A Pratt & Whitney R-2800 Double Wasp core engine is seen here mounted to the P-47. It is, of course, not the overhauled engine which will eventually power the Thunderbolt, but serves as a very useful tool for trial-fitting the various accessories before the refurbished powerplant arrives from the overhaul shop. (image via AirCorps Aviation)
Some of the myriad collection of exhaust manifold parts resting on a bench. Some of these components were not usable, or were missing, but a trip to the California desert this month happened and enough new old stock exhaust parts were found and purchased to complete that phase of the restoration. (image via AirCorps Aviation)
This new/old stock exhaust manifold section still has sand from the desert visible inside. (image via AirCorps Aviation)
The R-2800 as seen from the front. (image via AirCorps Aviation)
Mark works at assembling the exhaust manifold. (image via AirCorps Aviation)
Work progresses from the top of the manifold to the left side. (image via AirCorps Aviation)
This is the upper right side
of the exhaust manifold. (image via AirCorps Aviation)
The relationship between the accessory section and the manifold shows clearly in this image. (image via AirCorps Aviation)
The completed manifold from the right side. (image via AirCorps Aviation)
Here is the left side of the exhaust manifold. (image via AirCorps Aviation)
One of two exhaust tubes leaves the collector ring and routes to the waste gate and the turbosupercharger. (image via AirCorps Aviation)
The exhaust manifold feeds into the ducts running back to the turbosupercharger. The waste gate part of that system is shown here. (image via AirCorps Aviation)
The waste gate is used to regulate pressure to the turbosupercharger. When excess exhaust gas pressure isn’t needed, the waste gate is opened and the pressure bleeds off. (image via AirCorps Aviation)
Work on the cockpit enclosure has been resumed, and the skin pieces along the lower part of the assembly are being fitted. (image via AirCorps Aviation)

The Long Range Missions

A P-47 looks ready for a mission with wing and centerline drop tanks, as used on SW Pacific long range missions. USAAF photo
A P-47 looks ready for a mission with wing and centerline drop tanks, as used on SW Pacific long range missions. (USAAF photo)
July of 1944 was a relatively quiet period for the 35th Fighter Group. The 39th Fighter Squadron flew no combat missions between late June and the beginning of August. The lull in combat allowed for experimentation in the long range operation of the new P-47-23s. Training pilots to execute the newly-discovered techniques which resulted from these experiments took up much of July.

Flying from Nadzab on August 7, 1944, Major Richard Cella led a flight of twenty-six of the newly-received P-47D-23s on a 900 mile mission to Noemfoor. This mission involved providing defensive cover for the SeeBees constructing new airfields on Middleburg Island below them. Similar missions continued for 6 weeks, but the 39th was able to move up to Noemfoor earlier than that.

The 39th conducted its first operations from Noemfoor on August 9th. Noemfoor offered some significant advantages with its 7,000 foot, compacted coral runway. Continued testing to verify maximum permissible takeoff loads could be conducted on the long, smooth, and relatively unobstructed runway; the squadron settled on two 175 gallon tanks under the wings, with an additional 75 gallon belly tank. The combined total of these three tanks, 425 gallons of fuel, added 2,550 lbs. to the takeoff weight. With this additional weight, the P-47’s minimum take off speed proved to be between 125 and 130 mph,  15 to 20 mph higher than what the Thunderbolt needed without the drop tanks fitted.

During this time period, the legendary aviator, Charles A. Lindbergh visited various 5th AF and Navy fighter groups as a consultant. His role was to help improve range and load carrying performance for the fighters in use in the Southwest Pacific Theater of Operations.

Lindbergh visited the 35th Fighter Group on August 14, 1944 and presented his increased range procedures.1

He demonstrated how raising manifold pressure and lowering engine revolutions, could greatly improve P-47 fuel economy, and hence the aircraft’s range.

On August 20th, another long range mission involved a fighter sweep led by Captain Gordon Prentice. The duration of that sortie extended to over 5 hours and 20 minutes, making it the longest mission the 39th Fighter Squadron had flown thus far, and perhaps the longest of any 5th AF mission to date.2


1 Charles A. Lindbergh, The Wartime Journals of Charles A. Lindbergh, Harcouirt, Brace, Jovanovoch, Incv., New York, New York, 1970,p 905-906
2 John Stanaway, Cobra in the Clouds,Historical Aviation Album 1982.

Kornasoren Airfield, Noemfoor Island diagram
Kornasoren Airfield, Noemfoor Island diagram from Airdromes Guide Southwest Pacific Area, Office of Assistant Chief of Air Staff, A-3 Headquarters, Far East Air Forces.

With the maximum range techniques Colonel Lindbergh encouraged, together with the knowledge learned from the experiments which the squadron’s pilots conducted, the P-47 could now perform missions of nearly triple the range experienced before these innovations.

“No longer would the skeptics berate the P-47’s range. Later in the year, the squadron registered missions up to eight hours.”3

These techniques certainly increased the Thunderbolt’s combat utility in the Southwest Pacific, but what is seldom discussed is the price pilots paid for these extended missions. To take advantage of the technique of high manifold pressure and low rpms, the long range flights had to be flown at low altitudes. High enough manifold pressure couldn’t be maintained at the low rpms if the P-47s flew much higher than 3,000 feet.

A P-47’s pilot sits just above two tubes which supply hot exhaust gases to drive the turbosupercharger and just behind the big radial R-2800, both of which generate a lot of heat. Even in a tropical environment like New Guinea, where triple digit temperatures on the ground were common, pilots would normally mitigate the heat to some degree by climbing to an altitude which was cooler. Unfortunately for them however, the new long range techniques didn’t permit that option, so pilots now sweated in their cockpit for as long as 8 ½ hours at a time. They would often return home dangerously dehydrated and exhausted from missions like these.


3  John Stanaway, Cobra in the Clouds, Historical Aviation Album 1982, Temple City, CA, p.29


And that’s all for this month. We wish to thank AirCorps Aviation, Chuck Cravens for making this report possible! We look forwards to bringing more restoration reports on progress with this rare machine in the coming months. Be safe, and be well

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