Doc Flies Again: Think Your Project Is Hard? Try Restoring a B-29 Bomber!

There is more reflecting in the B-29 bomber plane’s mirrored surface than just the blue sky above and the runway beneath it. “Doc,” as this particular airplane is known, hadn’t flown in 60 years. Its polished skin reflects the surroundings, sure, but also a man’s dreams, a community’s effort, lives lost and wars won. For it to fly again for  the first time in six decades mere feet from where the B29 was originally assembled is a great example of the persistence needed to restore anything. Rescued from the Mojave Desert, Doc flew again from Wichita’s McConnell Air Force Base because of the blood, sweat, tears, and sheer determination of a large group of enthusiasts inclined to preserve The Greatest Generation’s history. Here’s some of that history.


Boeing broke all the molds with the B-29 Superfortress, which was the most advanced airplane ever built when it flew its first combat mission June 5, 1944. Not only was it designed with unparalleled scale and capability, but the Superfortress also featured important technological developments for all airplanes to come. The massive fuselage was pressurized, which allowed semi-comfortable flight at higher altitude where the airplane could fly faster using less fuel.

Many of the components used electric motors instead of hydraulic systems, another huge leap forward. With fewer hydraulic lines in the airplane, the B-29 gained a reputation for surviving with damage. Decades later, that design also somewhat simplified Doc’s restoration since electric motors are easier to source than obscure hydraulic components. The B-29’s gun turrets were also remote-operated through a primitive computer-controlled fire system, the first of its kind. Because the B-29 was heated and pressurized, it allowed gunners to ditch the bulky electrically heated suits needed on non-pressurized airplanes like the B-17 and B-24.

The B-29’s Wright engines were also remarkable and, coincidentally, contributed to automobile hot-rodding after the war. Because the massive airplane required performance at high altitudes, the two-row radial engines were both supercharged and turbocharged. This required a maintenance-intense schedule and as a byproduct of those countless hours of maintenance, airplane mechanics became very knowledgeable about forced induction. When those mechanics came home, they returned with a wealth of supercharger knowledge that found its way onto the odd Flathead Ford V8. [Read more on the B-29’s engines at the end of this story.]

Development of the B-29 paralleled the Manhattan Project, the United States’ first atomic program during World War II. The bomber program cost $3 billion, more than the weapons program it was designed around. While two B-29s did release the first atomic bombs on Hiroshima and Nagasaki in 1945, the bulk of the B-29’s operational history came in costly conventional and fire-bombing campaigns against the Japanese home islands.


Finding Doc

The B-29’s service life extended past World War II, which is where Doc comes in. Built in 1944, Doc never fought in World War II, although the airplane served later during the Korean War. After Korea, the airplane served from Rome, New York, in a radar-training squadron as one of nine B-29s, all of which were named after Snow White, the Seven Dwarves, and the Wicked Witch.

Doc flew for the last time in 1956 to the Naval Ordnance Test Station near China Lake in the California desert. The tail was removed after its final landing to clear power lines and the airframe was dragged many miles onto the China Lake range, where the Navy tested missiles by firing at Doc and dozens of other B-29s. Somehow, Doc avoided any direct hits and the worst damage came from baking in the desert sands untouched for 42 years.

This Superfortress would have been cut up into beer cans, if not for Tony Mazzolini. In the late 1980s, Mazzolini was after a large-scale airplane restoration project and he decided that the B-29 was the airplane he was going to restore. He knew where to start looking for the remaining B-29 airframes and in 1987, Mazzolini found Doc—an airplane he remembered seeing in the 1950s during his tenure as a B-25 pilot—mostly intact.

“[Tony] went out on a quest and said, ‘I’ve got to find a B-29,’” said Mark Paolucci, a Doc’s Friend’s board of directors member and former Cessna executive. “He’s the godfather of the whole project. It would not have happened without him.”

What followed was an 11-year odyssey just to free the airplane from China Lake. Before he could talk about plans for Doc, Mazzolini had to convince the Navy and the Department of Defense that Doc even existed. Since it had been cast into the desert and shot at, the airplane was gone, as far as defense officials were concerned.

After Mazzolini demonstrated its existence, an arrangement was made that required the restoration of a B-25 Mitchell for static display. Once the Navy had their B-25 and could display it at the National Naval Aviation Museum in Pensacola, Florida, they would hand over a title for Doc. In 1998, Mazzolini’s dogged determination paid off. Impressed by his drive, the Navy handed him a title for Doc.


Unlike the only other (currently) flying B-29, Fifi, there was no setting up a canopy in the desert and making the B-29 flyable right there. While the arid climate preserved much of the airplane, the glass was nearly all gone, the wing spar was rotted, and the tail was missing. However, the landing gear still held the B-29’s substantial weight after four decades so great care was taken to tow the mighty airplane across the open desert. It took five days for a bulldozer to tow Doc 38 miles to a place where the Superfortress could be disassembled neatly. After that, flatbed trucks carried Doc in pieces to McConnell Air Force Base in Wichita, Kansas.


Coming Home

Wichita itself was significant. Not only did the Wichita Boeing plant assemble B-29s there in the 1940s, but Mazzolini had also convinced Boeing and its later spin-off company, Spirit Aerosystems, to offer some material help with Doc’s restoration. That help included engineering support and a home base from which Mazzolini’s assembled volunteers—hundreds of people that included former B-29 crew members, assembly workers, Boeing retirees, McConnell Air Force personnel, and employees from Wichita’s substantial aviation industry—could begin the arduous process of rebuilding an enormous airplane.

“[Taking Doc to Wichita] was symbolic in a way because the aircraft was manufactured here,” Paolucci said. “But to be completely honest, if Boeing and Spirit didn’t have work around, that plane could have never been restored. A number of parts—the wing spar particularly—could never have been built by a bunch of guys banging away with hammers in a hangar someplace. Five-axis milling machines are not hanging around everybody’s garage.”

The support from Boeing and Spirit carried incredible value, but the scale of the restoration soon outpaced the funding Mazzolini could secure for it. Doc’s restoration was placed on hold for several years until 2013. That year, several business leaders from Wichita pooled their resources to restart the project—incorporated as non-profit Doc’s Friends—with capital input. Ownership of Doc was transferred from Mazzolini to the organization and with renewed financial backing, Doc’s Friends revitalized the volunteer effort. The project moved forward, albeit slowly, through private donations.

“With my life’s runway running short, I wanted to leave it in the right hands,” Mazzolini, now in his mid-70s, said after Doc’s first flight. “And it couldn’t be left in better hands and in a better location in this country. They said, ‘Don’t worry, Tony. We’ll make sure it flies before the end of your runway.’”


While most of the airframe is original, many components were beyond restoration. Unlike a ‘68 Charger project, a B-29 doesn’t have a swap meet or a new-old stock (NOS) parts hoarder from which replacements can be gleaned. Rather, missing parts required fabrication. On Doc, that included crucial components like the wing spar and tail section, which Boeing rebuilt early in the restoration using the original blueprints from the Wichita B-29 plant’s archives. Much of the airframe is original, however, and was overhauled.

It is important to note that Doc’s restoration crews and volunteers did not have to blaze the entire restoration trail. They partnered with the crew who restored and maintain Fifi, the world’s only other flying B-29 that operates with the Commemorative Air Force. Fifi’s maintenance crews, including flight engineer Don Obreiter, collaborated with Paolucci and Doc’s Friends to draft up important things like maintenance procedures, something that requires three full-time maintenance techs on Fifi.

“We actually started a cooperative with them,” Obreiter said. “We had just done the new engines on Fifi in 2010 and Doc was curious how that was going. We had operational information and Doc had all these machine shops doing stuff, so all of sudden it became a collective effort of information and parts.”

The engines are a crucial component of Doc and like Fifi, the ones on the airplane now are not perfect matches to four period-correct Wright R-3350-57s. The Fifi crew had run that -57 engine—a turbo-compound version of the 3,350 cubic-inch two-row radial engine—but the maintenance upkeep turned out to be a nightmare.

“The original engines were very high-tech, very state-of-the art. I would say ahead of their time, almost,” Obreiter said. “However, they were extremely unreliable and absolutely horrible to maintain, especially 70 years later. Even during the war, those guys were lucky to get 100 hours out of the engines. In 2006, we had had [Fifi’s] last core-overhaul that cost $157,000. That lasted about five hours before it let go.”

As a result, Fifi’s crew chief Gary Austin helped design and built a “hybrid” R-3350 engine using parts the later members of the engine family. When it came time to power Doc, the same type of engine setup was used.

“Our crew chief discovered that if you take the back half from a [R-3350]-26 that was on a Skyraider, it bolts to the engine mounts on the front spar of Fifi. And if you take the [R-3350]-95 version that was in the C-119s, that actually fits in front of the nacelle,” Obreiter said. “You put the two halves of the engine and basically create your own R-3350…It’s just like building a Small-Block Chevy, like a 383.”

With the engines sorted, there were only a few thousand more problems to solve. The entire airplane got miles of new wiring and brand-new, modern fuel cells. Because nobody was going to be shooting at Doc anymore, the original self-sealing fuel tanks were replaced with 13 lightweight-but-sturdy fuel bladders in each wing. Doc’s hydraulic components, which primarily run the brakes, were rebuilt using mostly original parts. The cockpit now includes some modern avionics in the interest of safety. That includes a Global Positioning System (GPS) and modernized navigation systems that improve situational awareness..

However, all of the restoration in the world means nothing without approval from the Federal Aviation Administration (FAA) to fly a B-29. Getting Doc off the ground meant passing an FAA inspection and having an airworthiness-continuation plan. That required development of an entire inspection plan and, again, Doc’s Friends were lucky enough to have Fifi around to have lain that ground work.

“When you buy a Cessna or a Beechcraft, it comes with a type certificate that the FAA has already approved: all the research, the development, the engineering, the repair methods,” Obreiter said. “When you get to a B-29, they never had a civilian-type certificate. They were a machine of war with no civilian market so there’s no type certificate. Everything is on a case-by-case basis. You have to do all the paperwork for operations, for maintenance, for all this stuff.”

Once Doc passes all of its flight tests, the FAA can only issue an experimental aircraft certificate for the purposes of exhibition. That comes with a number of limitations, namely that the aircraft cannot fly at night or in Instrument Flight Rules (IFR, basically when it’s too cloudy to see the ground), although the plane was and still is capable of IFR flight.

Additionally, Doc’s pilots must be FAA-approved. Again, since there is no FAA-wide pilot certification for the B-29, the FAA instead can only grant the pilot-in-command with a letter of authorization (LOA)—more or less approval for something outside of normal certifications—based on the aircraft’s weight and number of engines. That comes after completion of pilot training in a B-29 with an FAA-examiner check flight. That kind of check flight is the same you’d get in a Boeing 737, except the number of certified check pilots is more limited when it comes to the B-29. In fact, there’s only one such check pilot in the world.

Fifi has again blazed this trail with its own FAA-approved training program, which will again be used to train Doc’s pilots until Doc’s own training program can be undertaken. The training entails a minimum number of hours flying as second-in-command until certified for that position, at which point the second-in-command can begin training for the pilot-in-command. Certification applies to the flight engineer, as well, who is tasked with monitoring the B-29’s many mechanical, electrical, and hydraulic systems. When Doc was at last ready to fly, the FAA required certified crew—Fifi’s regular crew—to make the first test flight.


First Flight

On July 17, 2016, Fifi’s flight crews climbed aboard Doc on the apron at McConnell Air Force Base and set to work on putting the gleaming silver B-29 back in the air. Gathered next to Runway 19L sat a small cluster of a couple hundred people. Some were dignitaries of varying levels, but most were the Doc’s volunteers and their families, many of whom had been working on the B-29 since it arrived in Wichita.

“That airplane is such a complicated and huge machine,” Obreiter said. “It’s an overwhelming task just keeping them going, let alone put one together not to mention the cost. The Doc people really stood up.”

Estimates for the number of man-hours required to complete Doc extend well past 300,000. The hundreds of volunteers had spent those unimaginable hours disassembling, organizing, cleaning, checking, sorting, reassembling, and documenting every inch of Doc.

“[Doc’s restoration] was an excitement to begin with and then it became a very emotional journey for many of them because most of them were Boeing retirees and several of them passed away between the time the project started and finished,” Paolucci said. “Their spouses were connected with it. It became a small family of volunteers that continued to work on it for many, many years. For them, the first flight was very emotional with feelings both of sadness and elation.”

Doc’s main landing gear left earth for the first time in 60 years. As the crew guided it from the runway, the decades-absent B-29 shadow once again flashed over the building, Plant II, where thousands of wartime workers had constructed Doc and its 3,969 buffed-aluminum siblings in less than four years.


“After we landed, I was so happy and so proud of the people that had worked on that thing and the people who had come out to see it,” Obreiter said. “And especially for Tony. He said he continually prayed to god to let him see that plane fly before he dies.”

Mazzolini had turned over the reins of the project to Doc’s Friends, but he had stayed involved throughout. He participated in every board meeting and phone call. When a big part of the restoration was taking place like an engine first running or a wing being fit, Tony showed up. And he was of course in Wichita when Doc flew for the first time.


“I’m extremely thankful for this to see what I consider a dream come true,” Mazzolini (right, with Obreiter) said to the crowd after Doc’s first flight. “But it could not have happened without the help of many volunteers. Those volunteers stretch from the Mojave Desert who helped me move the airplane to relocating it here in Wichita and the volunteers who put forth 16 years of restoration to make a dream come alive and fly today.”

Doc has since flown a handful of test flights, which have shaken out some of the expected bugs and started to pave the way for the B-29’s future. Wherever it ends up, the hope is for Doc to serve the same role of Fifi as a historical ambassador for The Greatest Generation. The goal is to bring the sights, smells, and feelings back to the remaining veterans and to introduce them to younger generations to reflect on history.

Obreiter’s first day touring with Fifi and the CAF illustrates that importance:

“We went to Clovis, NM, of all places. We landed and…got everything set up,” Obreiter said. “I was wiping everything down and there’s a guy standing back by the [Auxiliary Power Unit] door, a small door in the tail on the right side of the airplane where your gunners entered through that door. This old guy is back there, crying.

“I walk up and thought something was physically wrong with him. He asked me if I was with the crew and then said, ‘You know, the last time I saw that door was in 1945 over Japan. We got hit, I don’t know what hit us or what happened. The bailout horn came on and we were all scurrying toward the plane to get to that door. I was the first one out. I watched that door all the way to ground and nobody else came out of it. I can still see those guys’ faces.’

“He hugged me and said ‘I can’t thank you enough for keeping their memories alive and bringing this thing out so people can see it.’ From that day on—that was my very first day out on tour—that completely changed what that machine means. I’ve never forgotten that day and I’ve been blessed to meet a thousand other ones just like him…That’s what this is all about.”



About “modern” B-29 engines

Wright built their 3,350 cubic-inch, two-row 18-cylinder Duplex-Cyclone family of radial engines from the B-29’s early development period in the 1930s until the late 1950s, where it powered everything from the Lockheed Constellation airliners to single-engined A-1 Skyraider ground-attack planes. The version originally used in the B-29, the R-3350-57, was an incredibly advanced engine that featured fuel-injection coupled with both turbocharging and supercharging. However, the engines seldom lasted long in wartime and even proved difficult to keep running for Fifi’s maintenance crews. Later versions of the R-3350 vastly improved the reliability, but the design had changed enough from the B-29 variant that those more reliable versions wouldn’t fit in the B-29’s engine nacelle without cutting them up and ruining the original appearance.

After a lot of examining and measuring, Fifi’s crew chief discovered that the back end of the Skyraider’s R-3350-26WD used the same mounting structure and the accessories on it would fit within the nacelle using minimal modification. If the nose case of the R-3350-95 from a C-119 Flying Boxcar was mated to the -26WD, that “hybrid” engine could fit the original four-blade B-29 propeller assembly. The resulting engine has been designated R-3350-B29, a part number you can order from the engine builder used by Doc and Fifi if you need a B-29 engine.

Fifi’s crew had a couple of hurdles to clear with this hybrid engine, however. The B-29’s engines were originally set up with the front cylinder banks’ exhausts exiting from the front side of the engine. Later variants had the exhaust ports on the back side of that cylinder row, so new collector rings had to be built to tie in the exhaust with the second cylinder bank. The replacement engines also dispensed with the complicated fuel-injection and turbochargers, replacing them with carburetors and using the intercooler inlets below the engine to funnel air to the carbs.

While the engines from which Fifi had borrowed both held FAA certificates, there was no type certificate on file for the R-3350-B29. Fifi’s crew had to demonstrate its airworthiness through an intense battery of tests and conservative testing with the B-29 propeller, which was also never historically used with either of the contributing “donor” engines. Ultimately, the “hot-rod” style engine matching has worked extraordinarily well on Fifi and was duplicated for Doc. The R-3350-B29 has proved robust and easier to maintain, even while Fifi has racked up lots of flight time.

  • Like all radial engines, the R-3350 engines consume oil. The average oil consumption is around 10 gallons per hour for each engine. Each engine carries an 85-gallon oil tank full of 100-weight aviation oil. The engines have trouble running cold below 50-degrees Fahrenheit because the low-viscosity of cold 100-weight oil can cause fluid-lock in the upside-down cylinders at the bottom of each radial row. The annual oil change flushes the engine with 120-weight mineral oil, which is also used during engine break-in.
  • During shorter demonstration flights with more takeoff and landing cycles, the B-29 will burn about 500 gallons of fuel per hour and about 400 gallons per hour during longer cruises.
  • Each cylinder has two spark plugs, each fed by a separate magneto for redundancy and improved reliability. That’s 144 spark plugs for each tune-up plus two more in the auxiliary power unit (APU).
  • The original fuel-injection system has been replaced by Bendix PR-58 pressure-injected carburetors.
  • If you want the tech specs on the engine, bore is 6.125 inches and stroke is 6.312 inches. The compression ratio is 6.5:1. The supercharger impeller is 13.5-inches in diameter and is driven off the back of the crankshaft with a gear ratio of 6.45:1. The reduction gear for the one-ton propeller is 0.4375:1. There’s no official horsepower rating on the “hybrid” engine, but the engines from which it’s based were both rated at 2,800 shaft horsepower.


What is maintenance like on a 70-year-old B-29?

Fifi’s maintenance schedule on the B-29 looks roughly like this (and Doc’s will look similar):

Annual Maintenance – Every November, Fifi flies to Fort Worth to undergo annual maintenance inspection. In addition to the usual FAA requirements for this kind of annual maintenance, Fifi has 72 more pages of procedures to follow. It takes the crew chiefs, flight engineers, and maintenance volunteers three to four months to do all the necessary tearing down, repairing, and overhauling. Once that maintenance is done, Fifi starts training flights for the following season’s tour with the Commemorative Air Force.


Every Six to Eight Weeks – Fifi is parked for a week or two. Crew chiefs go over a checklist of key items to give Fifi a good shakedown and to do several proactive checks.

Weekly – While on tour, the flight engineers are tasked with regular checks that include lube jobs, inspections, pressure checks, and more.

How labor-intensive is that? The running estimates on Fifi is that it takes roughly 100 man-hours of maintenance for every hour in flight. That’s not to say Fifi is problematic. “It’s a reliable machine, but it’s very complicated and 71 years old, maintenance chief Don Obreiter said. “It takes a lot to keep it going and take care of her.”

And how much do Doc and Fifi cost? Mark Paolucci of Doc’s Friends notes that the organization estimates a little less than $10,000 an hour to fly a B-29. That’s to say nothing of the restoration costs, which are so vast as to be virtually incalculable. “The financial aspects of restoring an airplane like this are excessive,” Paolucci said. “There’s no way to even calculate the money Boeing, and later Spirit, donated in kind by providing parts and/or tooling for assembly of the aircraft.”

After an initial capital investment when Doc’s Friends was incorporated, Doc’s restoration and operating funds have come from donations, the bulk of which have come from private citizens. See the Doc’s Friends website for more information on donating or volunteering.

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