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Warren Pietsch and Mark Tisler hold a painting of Thunderbird by Daryll Legg, used by permission. (photo via AirCorps Aviation)
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Over the past several years, aviation historian Chuck Cravens has brought us regular updates regarding ongoing restoration projects at AirCorps Aviation in Bemidji, Minnesota. Many of the aircraft involved have been for the fabulous Dakota Territory Air Museum, and such is the case for this particular story about the resurrection of a long-lost, legendary racing Mustang which dates to the post-war Cleveland National Air Races. The original constructors of this race plane built the airframe up from the components of three different Mustangs, but did not record their serial numbers. They listed it as a P-51C with the FAA, with the registration being N5528N. During her racing career, the Mustang bore the names Thunderbird, and later, Mr.Alex, so with the lack of a definitive airframe serial number, we will refer to it henceforth simply as Thunderbird/Mr.Alex. This current episode is Craven’s fifth installment of that aircraft’s remarkable story and its journey back to flight…
Here is a closer view of Darryl Legg’s excellent painting. (image via AirCorps Aviation)
Work on the cowling, fuselage, and wings all progressed over the last few weeks. The cockpit components and cockpit enclosure were areas which also received attention.
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Cockpit Enclosure
Fitting the windshield assembly and the rest of the cockpit enclosure is an exacting process. The aluminum frame structure needs to be fitted, and each window has to be trimmed precisely.
Aaron works on the windshield installation. (image via AirCorps Aviation)
The top windshield section is set in place to determine where trimming is necessary. (image via AirCorps Aviation)
Tape protects the window from scratches as the part is checked for final fit. (image via AirCorps Aviation)
Aaron has also been working on the side windows for the cockpit enclosure. (image via AirCorps Aviation)
The side window is hinged for pilot access to the cockpit from the wing. (image via AirCorps Aviation)
One of the windshield side windows and the two rearmost panels of the cockpit enclosure are now in place. (image via AirCorps Aviation)
With the top panel in place, the enclosure nears the point where permanent installation can occur. (image via AirCorps Aviation)
The P-51C’s distinctive, birdcage-style cockpit enclosure is clearly visible here. (image via AirCorps Aviation)
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Fuselage
Work on components for the cockpit has progressed nicely since the last update. Some firewall-forward engine accessories were also installed. The air scoop area is under preparation and the radiator is now installed; several related skin sections were also trimmed and fitted into place.
This is the trim console. The smaller, round opening without a needle bearing is for the elevator trim tab control. (image via AirCorps Aviation)
The opening containing a needle bearing is for the landing gear lock handle shaft. (image via AirCorps Aviation)
The trim console has been installed. (image via AirCorps Aviation)
Aaron has fabricated the instrument panel and will soon install the instruments. (image via AirCorps Aviation)
This is the hand pump for the hydraulic system. (image via AirCorps Aviation)
To the rear of the cockpit area, the master relay has been installed. The cardboard box is used to represent the actual size of the battery, and its
eventual placement. (image via AirCorps Aviation)
The tank at the upper left of the photo is the hydraulic fluid tank. The box to the right holds components for the generator control. (image via AirCorps Aviation)
This is the starter relay, mounted to the firewall. (image via AirCorps Aviation)
This is the shield assembly for the booster coil. (image via AirCorps Aviation)
The large upper cable is an elevator control cable. Below that, the smaller cables are rudder trim cables. Finally, the large cable near the bottom of the opening is the rudder cable. (image via AirCorps Aviation)
This skin section fits below the radiator. (image via AirCorps Aviation)
The radiator mounting straps hang ready for when the radiator is mounted. (image via AirCorps Aviation)
Here is a detailed picture of the radiator strap end. (image via AirCorps Aviation)
The radiator has been installed. (image via AirCorps Aviation)
Here is another angle showing the radiator’s front side. (image via AirCorps Aviation)
This complex skin section fits at the rear of the radiator scoop and blends the scoop contour into the rear fuselage. (image via AirCorps Aviation)
Clecoes are installed to hold the skin section from the previous
image to the side of the fuselage next to the air exit duct. (image via AirCorps Aviation)
The clecoes have been replaced by permanent rivets. (image via AirCorps Aviation)
Thunderbird’s spinner rests on a parts shelf, awaiting its turn in the restoration process. (image via AirCorps Aviation)
Mike works on the fit for the carburetor air intake duct assembly. (image via AirCorps Aviation)
This image shows much of the length of the carburetor air intake assembly. The black dots with white centers are stickers called “positioning targets” and are used when 3D scanning a part. They will be removed before final assembly. (image via AirCorps Aviation)
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Cowling
Mike expended considerable effort in fitting skin sections to the cowling. Thunderbird’s cowling featured several deviations from a standard P-51C configuration.
The air intake’s “smile” is in place. (image via AirCorps Aviation)
This bracket will be riveted to the cowl former and will attach the
former to the engine mount. (image via AirCorps Aviation)
Here we can see the bracket after it has been riveted to the cowl former. (image via AirCorps Aviation)
The lower cowl section on Thunderbird is broken down into a three-piece assembly which enables the fitting of a D-model wing to a C-model fuselage. A standard P-51C has a single piece cowl section here. (image via AirCorps Aviation)
Here is the rear lower skin section for the cowling placed just in front of the wing.
It is just one element of a three-section lower rear cowl, as used on P-51Ds, which covers the air induction assembly. Normally a P-51C would have a one-piece skin. This change is part of the necessary modifications to mount a D-model wing to Thunderbird. (image via AirCorps Aviation)
In contrast with the three-section, lower cowl skin on Thunderbird, P-51C Lope’s Hope 3rd has the standard C model one-piece lower cowl skin. (image via AirCorps Aviation)
Mike works on fitting another cowl skin panel. (image via AirCorps Aviation)
Here is a view from the left side as the cowl takes shape. (image via AirCorps Aviation)
Fitting work is progressing in this view of the inside upper cowling. (image via AirCorps Aviation)
Most Mustangs have a cover for the rectangular opening (near the center of this image) which has 32 holes in it. The holes allow air to pass through an intake air filter during ground operations. This would allow the Mustang to operate from dusty locations, which was often the case during WWII. However, given the pampered conditions which most P-51 warbirds operate in today, such provisions are not essential. Indeed many P-51s flying today do not have air filters even when they have the standard perforated cover. (image via AirCorps Aviation)
To lighten the airframe for its role as a long-distance racer, Thunderbird’s designers removed any unnecessary components, including air filters. To replicate this look in the resurrected Thunderbird, the restoration crew has installed new, hole-less covers for the fresh air intake opening.
The cover on the left side is identical. (image via AirCorps Aviation)
The original Thunderbird did not have intake holes in the rectangular panel (as seen in this famous image of Jackie Cochran standing beside the aircraft). There was probably a slight reduction in drag without said holes. (photo via Fédération Aéronautique Internationale World Air Sports Federation)
Mike works at forming a lower cowl skin on the English wheel. (photo via AirCorps Aviation)
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Wing
Thunderbird’s wings have a few differences to those of a stock military Mustang, most notably in their lack of armament bays and gun ports.
The right aileron has been installed. (image via AirCorps Aviation)
The olive drab pulley with aileron control cables encircling it is the outboard aileron pulley assembly. (image via AirCorps Aviation)
These are the aileron control cable tensioning turnbuckles. (image via AirCorps Aviation)
Aileron control cables run through a phenolic guide. (image via AirCorps Aviation)
The right landing gear leg has been retracted into the up and locked position. (image via AirCorps Aviation)
The upper end of the main landing gear strut is in place. The thin cables connect to the landing gear timing valve. (image via AirCorps Aviation)
The skin covering the upper landing gear is riveted in place. (image via AirCorps Aviation)
Unlike a military Mustang, Thunderbird has no gun ports on the wing leading edges. (image via AirCorps Aviation)
This is the left-wing leading edge section which fairs over the omitted gun ports. (image via AirCorps Aviation)
Here is a view into the gear bay. (image via AirCorps Aviation)
Mark works on a gear door. (image via AirCorps Aviation)
Mike attaches the air intake elbow assembly that directs air up to the carburetor. (image via AirCorps Aviation)
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Historical Highlights of the Bendix Trophy Race
Thunderbird’s fame comes in large part from its victory in the 1949 Bendix Trophy and its all-time, propellor-driven average race speed record of 470.136 mph. 1949 also marked the final running of the propellor-driven Bendix Trophy race, making Thunderbird its ultimate winner.
The Vincent Bendix race originated with a 1931 meeting in the club car of the New York Central Railroad’s premier passenger train – the Commodore Vanderbilt. Vincent Bendix was a famous and very successful industrialist and inventor. His company manufactured everything from automobile brakes and starters, to avionics and pressure carburetors for airplanes.
Clifford Henderson, the originator and promoter for the National Air Races, approached Bendix to propose an annual, free-for-all, cross-country air race. Henderson’s sales pitch involved the proposed race providing a goal for airplane designers, builders, and pilots to “really get down to business.” By this, Henderson implied that the competition would boost the design of faster, more reliable, and more durable aircraft. Henderson felt that the Bendix name had a magic ring to it, fostering an image of speed, reliability, and progress. Sponsoring the race would also help Bendix promote his aviation products.
Henderson showed Bendix a preliminary drawing of a trophy proposed for the race, but it failed to impress. Bendix thought that it resembled an ordinary loving cup, and told Henderson to return only when he’d designed a more impressive trophy.1
For a far more comprehensive history of the Bendix Trophy Race, please see Don Dwiggins’ book, They Flew the Bendix Race, footnoted below.
1Don Dwiggins, They Flew the Bendix Race, J.B. Lippincott Company, New York, 1965, p.14-15
The Vincent Bendix Trophy, donated by the Clifford W. Henderson Family Trust. (photo via Smithsonian National Air and Space Museum)
Henderson commissioned a new trophy from the artist Walter A. Sinz, who sculpted the design and then cast it.
Vincent Bendix must have liked the new 100-pound bronze trophy, because he agreed to sponsor the cross-country race with a contribution of $15,000 which had to be matched by the Cleveland Air Race Commission.
Laird Super Solution replica at the Fantasy of Flight museum. (photo Valder137, CC BY 2.0, via wikimedia commons)
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The legendary Jimmy Doolittle became the competition’s first winner, flying the Laird Super Solution at an average 223.058 mph, during the Bendix Trophy Race of 1931. Henderson’s vision to encourage aircraft designers/builders to strive for more speed and reliability worked. The nature of the long, cross-country race demanded significant reliability for an aircraft even to finish, and each iteration of the race saw developments which usually increased the average race speed.
Mr. Mulligan in 1935. (photo via Wikipedia)
The 1935 Bendix featured the first (and only) racer specifically created for the race. Designed by famed aeronautical engineer Benny Howard, the sleek high-winged monoplane was designated as the Howard DGA-6, although its nickname, Mr. Mulligan, is far better known.
Howard’s philosophy was for Mr. Mulligan to fly the entire Bendix race, nonstop, at high altitude.
Eliminating the fuel stops which each previous Bendix racer had to make saved a great deal of time, and the strategy proved successful; Howard finished first in 1935, ahead of Roscoe Turner. Howard even went on to win the Thompson closed-course pylon race on the following day.
Jacqueline Cochran, with the Seversky AP-7 which she piloted to victory in the 1938 Bendix Race. (photo via National WASP WWII Museum)
Variants of the Seversky SEV-2S won the three Bendix races run between 1937 and the onset of WWII, which saw the suspension of air racing. Jackie Cochran won the 1938 event in a Seversky AP-7, an improved civilian version of the Army Air Corps’ P-35. Jackie averaged 249.774 mph during that race. She later went on to feature in Thunderbird’s history too.
The post-war races took advantage of the accelerated improvements in aircraft design and technology which were the result of the all-out war effort. P-51 Mustangs won each of the propellor division Bendix Trophy’s from 1946, when racing resumed, through the last propellor-driven race in 1949. Paul Mantz won the race in 1946, 47, and 48, but Joe DeBona took the 1949 Bendix Trophy in Thunderbird, with a record speed of 470.136 mph, a record which still stands since it was the final Bendix race to include a propellor division.
This photo of Thunderbird was taken at the 1948 Bendix race. Notice that the rudder does not carry the yellow checkerboard paint, and there is no yellow stripe on the forward fuselage or yellow paint on the spinner. Next to Thunderbird on the left is the wing tip of Jackie Cochran’s P-51, Race Number 13. (photo by Pahl from the Dick Phllips collection, courtesy of Mark Phillips)
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One of the Mustangs sponsored by oilman Glenn McCarthy appears on the right side of the above photo. That aircraft was Buttonpuss, the nickname which the aircraft’s pilot, Edmund Lunken, gave his first wife, Dorothy. Lunken finished in 4th place with an average speed of 441.594mph.
McCarthy’s Buttonpuss, with Thunderbird visible in the background. (photo by Pahl from the Dick Phillips collection, courtesy of Mark Phillips)
Jackie Cochran’s P-51 (Race Number 13) is seen here; it would finish 3rd in the 1948 race. Thunderbird can be partially seen on the right side of the picture. (photo by Pahl from the Dick Phllips collection, courtesy of Mark Phillips)
In the first color photo, there is an odd-looking device atop Thunderbird’s vertical fin, which is depicted more clearly in the image below.
The unit on the fin shows in this 1948 photo of Thunderbird. (photo by Chalmers Johnson, courtesy of Tim Weinschenker collection)
The odd-looking protuberance on the fin is believed to have housed an ADF (automatic direction finding) antenna. This feature was moved under the wing center section and covered with a fairing for the 1949 race. (photo by Chalmers Johnson, courtesy of Tim Weinschenker collection)
From biplanes at 223 mph to Mustangs at 470 mph, the Bendix race showcased the aeronautical engineering progress that took place from 1931 through 1949.
Special thanks must go to the air racing historians/authors A.Kevin Grantham and Tim Weinschenker, as well as the author Mark Phillips for their help in providing images and proper credits for this segment on the Bendix Trophy air races.
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And that’s all for this exciting news about the resurrection of Thunderbird. We will present further updates as this famous racing aircraft returns to her former glory. Many thanks to Chuck Cravens and everyone at AirCorps Aviation and the Dakota Territory Air Museum for their help in making this article possible.
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.
What is the advantage of the D model wing over the C model? I thought the B’s and C’s had a thinner wing which gave it a slightly faster speed over the D models. Was it fuel capacity?
Hi Marc… well, as it turns out, the answer to your question about the wing choice is covered in the first of Chuck Craven’s articles about Thunderbird. Here is the quote which will offer some insight into their thinking…
“One of the aspects affecting this choice to use a D-model wing relates to both safety and handling qualities. The later model wing has more robust and reliable landing gear and gear door systems. The B/C wing’s clamshell doors were lighter and had a single uplock, while the D gear doors have multiple locks which make cycling the gear more reliable. Additionally, there are documented instances of B/C doors tearing off in high speed dives, so North American re-engineered an updated system for the D model.
Interestingly, the early model clamshell doors on the original Thunderbird may have been what caused the aircraft to crash in June of 1955 when they closed out of sequence, jamming the main landing gear. The owner at the time, Joe Cook, elected to bail out rather than risk a landing in the wet-winged Mustang with the gear now protruding from the airframe.
In addition to improved gear doors, the D model wing also has stronger and more effective ailerons. A seal added to the aileron leading edges reduced stick pressure during hard maneuvering.”
What is the advantage of the D model wing over the C model? I thought the B’s and C’s had a thinner wing which gave it a slightly faster speed over the D models. Was it fuel capacity?
That’s a good question Marc, I will ask them and see what they say. Many thanks for writing in!
Hi Marc… well, as it turns out, the answer to your question about the wing choice is covered in the first of Chuck Craven’s articles about Thunderbird. Here is the quote which will offer some insight into their thinking…
“One of the aspects affecting this choice to use a D-model wing relates to both safety and handling qualities. The later model wing has more robust and reliable landing gear and gear door systems. The B/C wing’s clamshell doors were lighter and had a single uplock, while the D gear doors have multiple locks which make cycling the gear more reliable. Additionally, there are documented instances of B/C doors tearing off in high speed dives, so North American re-engineered an updated system for the D model.
Interestingly, the early model clamshell doors on the original Thunderbird may have been what caused the aircraft to crash in June of 1955 when they closed out of sequence, jamming the main landing gear. The owner at the time, Joe Cook, elected to bail out rather than risk a landing in the wet-winged Mustang with the gear now protruding from the airframe.
In addition to improved gear doors, the D model wing also has stronger and more effective ailerons. A seal added to the aileron leading edges reduced stick pressure during hard maneuvering.”