The 10-engine plane time forgot: Convair's B-36 Peacemaker

The Convair B-36 Peacemaker is the largest piston-powered combat aircraft ever built. Powered by six radial and four jet engines, it bridged the gap between WWII propeller aircraft and the jets of the Cold War. Here's a look at this unique machine.

For the full story, check out Six turning, four burning: A closer look at the enormous 10-engine B-36.

Designed during World War II, only one prototype was built, the XB-36 seen here. It first flew in August 1946. While there were numerous differences between this and the first production aircraft, the most noticeable is the more traditional cockpit design.

Though not unique, the B-36 features the rare pusher-prop configuration, with the propellers mounted behind the 28-cylinder engines.

The B-36 has the largest wingspan of any combat aircraft, at 230 feet or 70.1 meters. For scale, that's a B-29 on the left, which was one of the largest aircraft of World War II and first flew only four years before the B-36.

An RB-36D reconnaissance variant on the Convair assembly line in Fort Worth, Texas. Note the higher-visibility bubble cockpit.

Multiple modifications, including the aforementioned addition of four J47 turbojets, gave the B-36D and later versions the performance intended by the initial design. But by the time they flew, WWII was long over and the need to fly from the east coast of Canada to Berlin and back was no longer the main goal.

B-36s were known for their slogan of "six turning and four burning," though the jet engines were typically only used for takeoff and, though never required, additional speed over a bombing target. 

In flight the engineer could shut the jets down and close special louvers at the front of each engine to reduce drag. This extended maximum range at the expense of cruise speed.

Compared to its predecessor, the B-29, the B-36 has slightly faster cruising speed, had a much higher top speed and service ceiling, and could carry a significantly greater bomb load over a longer distance. It was, to put it mildly, a huge leap in performance.

Despite its capabilities, the B-36 never fired a shot or dropped a bomb in combat.

Being one of the largest aircraft to ever fly, and having such impressive lifting abilities for its day, the B-36 became a sturdy platform for a wide range of testing. This is the original prototype, outfitted later to test tracked landing gear.

As you probably assumed, the tank-like arrangement wasn't successful.

It wouldn't be long before entirely jet-powered aircraft replaced the B-36. Here it's helping test the delta wing design of a next-generation bomber, what would become the Mach 2-capable B-58 Hustler.

The B-36 covers one of my favorite eras in aviation, the post-WWII/early Jet Age, where engineers experimented with all sorts of wacky ideas. For instance, this is the NB-36H. It carried, I'm not kidding, an active nuclear reactor.

The reactor never powered the aircraft, though it was running during several dozen flights to test radiation exposure for the crew (how would you like that job?), and overall feasibility of using a reactor to power an aircraft. With the advent of ICBMs, the need for permanently aloft aircraft abated.

The lead-shielded cockpit had greatly reduced visibility. This was the nuclear engineer's position, directly behind the pilots. Note the screen at the top to show the status of the engines.

Next station rearward was the flight engineer, who had the same number of controls as a standard B-36, with dials and levers for all 10 (10!) engines. We'll see what a standard B-36 cockpit controls look like a bit later.

Convair designed and built an experimental cargo version of the B-36, called the XC-99, which featured a taller fuselage with two decks.

The XC-99 could potentially transport up to 400 troops. For comparison, this is about how many passengers early 747s carried 20 years later.

Convair considered making an airliner version of the XC-99, but the radial engines were too expensive for profitable commercial service. The XC-99 remained in Air Force use until 1959. It's currently in storage at the AMARG Boneyard awaiting restoration.

The "flying aircraft carrier" idea has been a dream of engineers long before the S.H.I.E.L.D. Helicarrier. With the GRB-36D a modified B-36 would carry a modified F-84F.

Initially the idea was for the smaller, faster jet to carry a small tactical nuke while the longer-range but slower bomber loitered outside enemy defenses. Later this was changed to a reconnaissance role, using the RF-84F Thunderflash.  

Apparently the docking and undocking procedure, using a hook attached to the nose of the F-84, was very difficult. This doesn't seem surprising.

Unlike previous iterations of this idea, the fighter pilot in this version could enter and exit his aircraft midflight. Related: The B-36 had a toilet.

The Jet Age was already ramping up when the B-36 entered service. Its four turbojets were a harbinger of things to come. Convair certainly knew this, and built the all-jet powered YB-60, which was essentially a heavily modified B-36.

The YB-60, seen here with a B-36, had many issues and only the prototype was built. Instead, the Air Force chose a similar design from Boeing that first flew three days before the YB-60: the B-52. 

B-52s are still in active service with the Air Force 68 years after the design first flew. They're expected to remain in service until the 2050s, some 90 years after the last aircraft rolled off the assembly line.

Production on the B-36 ended in 1954 with this, serial number 52-2827 The City of Fort Worth. It now lives a quiet, sun-drenched life in the Arizona desert, at the incredible Pima Air and Space Museum.

"The City of Fort Worth" was stationed in El Paso, Texas until 1959, when it and its sisters were retired and replaced by B-52s. Nearly all of the 384 B-36s were scrapped. Only four intact airframes remain.

This one is a "J" Featherweight III high-altitude variant with fewer guns and crew.

The massive 28-cylinder, 71.5-liter engines developed 3,800 horsepower. Maintenance was time consuming, as you'd expect with a total of 336 spark plugs across six engines. The props are larger than the propellers on the RMS Queen Mary cruse ship.

The only intact surviving RB-36H is at the Castle Air Museum in California which has many classic bombers. Note the "tiny" F-16.

Nearly a third of all B-36s were reconnaissance variants. Depending on the cameras used, the RB-36 could photograph straight down, or obliquely to the side.

The huge wings are thick enough that engineers could climb inside and perform maintenance on the engines in midflight. 

Cruising speed, depending on the variant, was around 230 mph (370 km/h), but with the four jets throttled up, that could increase to a rather impressive 435 mph (672 km/h).

Nearly all variants had rear-facing canons. In later versions, like this one, the turret was controlled by radar (the two domes above the canons).

The B-36 could carry up to 86,000 pounds (39,000 kg) of bombs. For comparison, the B-29 could only carry 20,000 lbs. (9,100 kg) and only for short distances.

To get from the forward compartments to the rear, there's a small tunnel with a dolly. That's the tunnel there, and we'll see the dolly inside a bit later.

The radar and navigator stations in the lower nose of the B-36J at the National Museum of the United States Air Force.

Bomber variants had a crew of from 9 to 15 airmen. Reconnaissance variants, with several of their bomb bays converted to cameras and a darkroom, could have up to 22.

The radio operator's station, which is aft of the navigators station and below the pilot and engineer. To the lower right, just beyond the edge of the image, is the entrance to the "communication tube" that allowed access to the rear of the aircraft.

The dolly that let crewmembers go between the front and rear compartments.

The bubble cockpit gave an expansive view. Quite a contrast to, say, the tiny windows of the Avro Vulcan that first flew only a few years after the B-36 was introduced. 

The flight engineer had plenty to manage in flight. He faced rearward.

The B-36 is a fascinating look at a peculiar time in aviation. Its size and rapid obsolescence means only a handful remain, but it seems that almost all of those are well taken care of in some excellent aviation museums. 

For more about this bizarre and unique aircraft, check out Six turning, four burning: A closer look at the enormous 10-engine B-36.