America's Strangest Bomber Experiment- Witteman-Lewis XNBL-1

After experiencing the horrors of World War 1 firsthand, a brave Lieutenant General defied the United States Army and set out to create his own aviation project: the Experimental Night Bomber Long Range.
The Witteman-Lewis XNBL-1, commonly known as the Barling Bomber, was the largest aircraft ever built back then and ended up winning several impressive world records.
The product of idealistic passions, this behemoth of an aircraft exceeded the technological realities of the 1920s and was the face of a political storm that surrounded the future of America's military might after the war.
It was also one of America's strangest long-range bomber experiments ever built.
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Join Dark Skies as we explore the world of aviation with cinematic short documentaries featuring the biggest and fastest airplanes ever built, top-secret military projects, and classified missions with hidden untold true stories. Including US, German, and Soviet warplanes, along with aircraft developments that took place during World War I, World War 2, the Korean War, the Vietnam War, the Cold War, the Gulf War, and special operations mission in between.
As images and footage of actual events are not always available, Dark Skies sometimes utilizes similar historical images and footage for dramatic effect and soundtracks for emotional impact. We do our best to keep it as visually accurate as possible.
All content on Dark Skies is researched, produced, and presented in historical context for educational purposes. We are history enthusiasts and are not always experts in some areas, so please don't hesitate to reach out to us with corrections, additional information, or new ideas.

[@StuSaville]

From this thing to B-17's in just 12 years. Crazy rate of progress!

[@scrappydude1]

Or from this to B-52’s in just 30 years

[@randomuser5443]

@@scrappydude1 b52B to maybe B21 in 80 years

[@10siWhiz]

Or from this to the Saturn V in about 40

[@admiral_alman8671]

There are so many interesting planes rarely anyone knows about today and Dark Skies brings those stories to us

[@nicholasmazzarella2720]

Well said : )

[@lancerevell5979]

I have seen pics and read short descriptions of the "Barling Nomber" through the decades, but never got the whole story, as presented here.

[@shauny2285]

Rare aircraft fan? Check out Ed Nash's Forgotten Aircraft series. Worth a look.

[@marcothommen2484]

It's like "forgotten weapons" for aircraft

[@joestephan1111]

You didn't have computers back then. If you had an idea you tried it. If it didn't work you went back to the drawing board.

[@Agent_3141]

The story of Mitchell having bombers sink a warship to prove their worth is at the National Air Force Museum in Dayton, Ohio. It's a pretty great story. And thanks to him saving the use of bombers, the B-25 Mitchell was named after him

[@LostInTheFarmersMarket]

You forgot, the B-25 is the only one to be named after a person as opposed to what the norm is and was.

[@kiwibonsai2355]

A couple of early bi wing bombers are apparently buried in the North head tunnels in New Zealand. They were stored for protection and able to be brought to the surface and built. Alot of mystery surrounds the sealed off tunnels and has always interested me. ✌️❤️🇳🇿

[@seavixen125]

The first two ever boeing aircraft built that were used by the Walsh brothers. I'd love to know weather they are down there.

[@topturretgunner]

That would be something if that story is true! Imagine two WWI era bombers sealed up in a tunnel and then brought out. That’s like the story of the P-38 Lightning that was recovered from deep in the ice of a Greenland Glacier and restored.

[@Minong_Manitou_Mishepeshu]

@@topturretgunner Lots of well preserved classic fighter wrecks have been pulled out of the Great Lakes. Just found a P-39 recently, this wreck was from a Tuskegee Airman while in training.

[@topturretgunner]

@@Minong_Manitou_Mishepeshu . Thank you for that. The stories surrounding the Great Lakes training carriers and the aircraft lost off of their decks in landing mishaps are many. The two that always come to mind are the early F4F's that were recovered in remarkable condition and restored to flying condition. One of the two later winding up at the Pacific War museum on Ford Island at Pearl Harbor in Hawaii. Many of the aircraft are at the Naval Air Museum in Pensacola FL. It seems to that the Navy is very jealous when it comes to the recovery of their wrecked and abandoned aircraft from those training incidents on the Great Lakes.

[@wormyboot]

The early days of aviation would be an amazing time to be alive, all things considered.

[@PORRRIDGE_GUN]

This is why one of my favourite films is The Great Waldo Pepper when flying, albeit dangerous, was FUN! (Before the creation of the FAA, aka 'Fucked Again and Again')

[@robertdragoff6909]

It was an ambitious experiment that was hobbled by politics and outdated thinking from the Navy that battleships win wars. I’m sure with bigger engines it might have had better performance.

[@redtomcat1725]

Thank you for bringing this bomber to light. I have studied aviation all my life[age 75] and did not know of this effort. Imagine if it would have proceeded in development. We could of been decades ahead in bomber design.

[@rong1924]

Between-the-wars was the strangest time ever for aircraft design.

[@thedungeondelver]

A close runner-up is Navy aviation in the late 50s. So many strange and very short-lived designs.

[@oneshotme]

Enjoyed your video so I gave it a Thumbs Up as a support

[@conservativemike3768]

Although old planes look primitive, the math & engineering principles were identical to today. Every component was optimized to the max extent, and only limited by the materials, test facilities, and economic conditions at the time. Everyone dreamed of building exoatmospheric vehicles, but they just had to wait until all the right factors came together at the right moment.

[@navyreviewer]

Thaaaaank you. Couldnt have said it better. As someone said "aside from the funny hats they're us." If the best engine you have is 400 horsepower you'll probably build a plane as light as possible with as much lift as possible. That means a cloth and wood bi-plane.

[@jimshorts6751]

All true, but NACA did invent wing shape never thought of before WWII. Granted, they were feasible because of an increase in HP.. then things went nuts with rocket and turbojet, and then turbofan engines. Just like computers, once one record was broken, the technology leapfrogged with subsequent designs. Most people get blurry eyed when they realize the A12/SR71 was designed in 1959 and were flying by 1963(A12) and 1964(SR71). The 747 from 1969 would awe these engineers.

[@conservativemike3768]

@@jimshorts6751 / The Dornier seaplane with what.. 12 engines? Things changed fast.

[@stevencoghill4323]

Thank you for this video. I have walked by that wheel dozens of times without knowing its significance.

[@spaceman081447]

@Steven Coghill At the Air Force Museum, there's an even bigger wheel - a main wheel from an early model B-36.

[@ChiChi-dy9qi]

Sad that anyone should feel ashamed or embarrassed by such a wonderful thing. Success or failure, it was a wonderful adventure into what might be possible.

[@usgator]

It always seems like people of the past had bigger dreams for the future. They always seemed so optimistic. We’re a world of pessimists now.

[@daveanderson3805]

Agreed 👍

[@grahvis]

We live in a different world, with a much greater knowledge of possibilities and limitations. There is also the law of diminishing returns, as everything is more advanced, future advances get smaller.

[@lordgarion514]

We're trying to figure out how to go faster than light. Put people on other worlds permanently. Fly at hypersonic speeds within our atmosphere. And on and on. You listen to the news and net repeat the same negative things over and over. Yeah, there's a LOT more people today, and everyone blabs everything negative that happens today. Them not telling the world doesn't mean life was all roses. It wasn't. Fact is what they were doing back then is peanuts compared to what's going on today.

[@RS-ls7mm]

War or fear of war is always an extreme motivator. We may soon be back to these times. The current research budget is a tiny fraction of what it was during the cold war. We seemed to have decided to use the money to make us more comfortable instead of safe.

[@forcesightknight]

My glass is half full. OF AIR

[@dougscott8161]

The main cause of this massive aircraft's failure to perform adequately was the Government's requirement that the only engine permitted to be employed was the old, under power Liberty 400 horsepower V-12's. 750 horsepower engines would have given the aircraft the needed airspeed and altitude capabilites. Also General Billy Mitchell was proven right, doubly, first when his forces did successfully sink a captured battleship, and again on Dec. 7th 1941, when the Japanese used his tactics to attack Pearl Harbor.

[@blackroberts6290]

And he also conceptualized something that would become the DoD later down the road.

[@aaronhunt1634]

This was a first for me. I had no idea such a plane had even been made let alone flew, and you can certainly see it as the missing link in heavy bomber evolution. Nice, clear ,informative video. Thanks, man, I enjoyed it.

[@GoodmanMIke59]

1:18 ... one thing is not "1,000 times less expensive" than another. It is "1/1000th the cost" of something else.

[@kmoecub]

Same = same, both mathematically and linguistically.

[@WALTERBROADDUS]

Just to put this in perspective, an f-15e today has a payload of 23,000 lbs....

[@lambastepirate]

Well that is comparing apples to oranges HAHAHA the one you should compare it to is the B-1 strategic bomber at 57,000 lbs. Or the stealth B-2a with a maximum estimated weight of 50,000lbs

[@EspionageTV]

Fantastic Dark Dynasty

[@davidanderson1889]

Just a small correction if i may. Billy Mitchell's highest achieved rank was Brigadier General (1 star), not Lieutenant General (3 stars). He was demoted to Colonel after disobeying a direct order during his demonstration flight when he sank an old captured German battleship, using 2000 pound bombs instead of 500 pound ones as ordered. Following his court-martial, during which he was sentenced to one year without pay and a further reduction in rank, he retired from the Army and died shortly after from pneumonia

[@captaccordion]

The Barling's predecessor, the Tabor never actually flew. The high mounted engines drove it's nose into the ground as soon as power was applied on it's first takeoff run. This mistake was notably not repeated on the Barling, but the wheels under the nose were a further precaution.

[@PORRRIDGE_GUN]

I was going to add that. Like stabiliser wheels on a kids first bike!

[@benjaminrush4443]

Excellent! First time I heard of this Bomber. I'm 70 yrs. old. Thanks.

[@joce0993]

A good watch, as always! Do the Fisher P-75 Eagle!

[@jamesroets800]

Just think of all the time and trouble that could have been avoided if someone had championed Gen. Mitchell's ideas. Instead, he was fought against, and ultimately court martialed for his advocacy of air power. Sweet revenge that his vision was borne out, but we could have been so far ahead of the world in strategic warfare. Instead, we had to learn again the lessons of the previous war.

[@scurge1971]

FREAKIN GREAT>>>>I was almost in tears....Great job

[@charleslatora5750]

Always learning something new.

[@mhos6940]

The concept was sound, but it would take over a decade for the technology to catch up. Culminating twenty-four years later into the best US prop driven bomber. The Convair B-36 Peacemaker. Only to be replaced less than a decade later by the ultimate bomber. The B-52.

[@yidy1]

Amazing! Thank you for this chapter of history!

[@arthurjennings5202]

The insistence of using the liberty engine for all military aircraft construction surly limited designers during the early 1020s. I am sure that service rivalry contributed to many dead ends during this period. 400 hp was not a lot of power to carry a useful payload. Also, naval technology was a mature science whereas aircraft technology was only 16 years old in 1919.

[@markmulder9845]

The OG flying fortress.

[@73honda350]

Amazing that aeronautical tech went from this failed effort to support a novel war strategy to the B29's technological success in proving that strategy in less than 20 years after this plane's last flight.

[@mikew2068]

Thank you for all the great content. I love watching your stuff!!

[@stephendoherty1275]

I believe dissolving NACA was a wrong move. The analytical information they provided was invaluable. NASA got the mission done, but has done little more... NACA would have furthered aeronautical engineering with leaps and bounds and we would have been so much further along than we are today. Damit - We might already have a warp drive by now! I think a solid video on NACA would be worth making. Thank you.

[@allangibson2408]

The NACA wasn’t dissolved - it formed the heart of NASA with all its programs continued.

[@WALTERBROADDUS]

NASA's doing just fine.

[@stephendoherty1275]

@@allangibson2408 Yes, NASA absorbed NACA and changed their main objectives and SOPs. NASA is all about space. NACA was all about aircraft, performance and designs... I believe this is much more important than space exploration. It, NACA, could have made more aircraft advancement that we have today.

[@stephendoherty1275]

@@WALTERBROADDUS I disagree. They haven't done much more that a couple of projects - and spend Billions of dollars that would/ could have been relegated to aircraft - What we use every day, all around the world. NACA did and would have continued aircraft development and design to break barriers and enhance performance in ways we do not know.

[@WALTERBROADDUS]

@@stephendoherty1275 I'm not sure what advancement you think we are missing?

[@grahamrankin4725]

If they access to more powerful engines at the time instead of surplus, it may have reached its design goals.

[@jonniez62]

Muir Fairchild is the name sake of Fairchild AFB, WA. As a General Officer KIA during a bombing mission and won the Medal of Honor.

[@Otokichi786]

"Lt. Mitchell"!? That reminds me of a Reader's Digest Humor In Uniform entry. A Lt. General hospitalized at a military hospital was referred to as "Lt. Smith." Miffed, he roared: "Do you call a Navy Admiral 'Rear!?" This interesting/continuing error earns this channel The Brass Ruptured Duck with Akatombo clusters.;)

[@HollywoodMarine0351]

I also heard it. Every time I watch Dark series videos I know it will come with mistakes and errors.

[@mp1335]

Can you make an episode on other, lesser known series from smaller countries? Like Lithuanian ANBO series for example.

[@chuckdeyo291]

as I was watching this I could not help but see a good looking fuselage that looked out of place with everything else.

[@Rincypoopoo]

Poor things. Those wretched Liberty engines. Imagine it with two Pratt & Whitney engines and one less wing !

[@sheilaolfieway1885]

1:20 court martialed for wrong think, sounds familiar... also b-25 mitchell.

[@discount8508]

from big things bigger things grow

[@Idahoguy10157]

The years of trench warfare created millions of casualties for no gain. Aviation was vaunted as a better way to defeat an enemy without the casualties

[@MisteriosGloriosos922]

*Amazing!!!*

[@MtnManLucas]

Very interesting!

[@antr7493]

He later became Major General William "Billy" Mitchell, namesake of the North American B-25 Mitchell bomber 😁

[@bobbyhill3323]

Sometimes, a cigar isn't always a cigar.

[@Wideoval73]

Great video. Thanks

[@BarDog57]

7:30 Boeing Field is in Washington state, not D.C.

[@rolandrodriguez3854]

Gee Thanks, Hap Arnold.

[@bobjove6511]

this is a legend

[@peterfichera2027]

As Tim Taylor would have said ,"More power!"

[@shawntyrrell5473]

Mostly a helicopter junkie. Don't get me wrong, I love flying and aviation. Love the videos you do about different aircraft, some have never heard of. Learned a lot from your videos. Keep up the good work..

[@LeifEriccson43]

Muir Fairchild is the namesake of Fairchild AFB outside of Spokane WA.

[@robertphillips6296]

You referenced the rank of Lieutenant General for William “Billy” Mitchell. This is incorrect he never rose above the rank of Brigadier General and held the permanent rank of Colonel.

[@rodsprague369]

It is a pity they did not fund a second prototype after learning how not to build a large bomber. It reminds me of how the Comet passenger jet was fixed by its maker de Havilland after using their own money researching how it failed in the first place, made into a remarkably safe aircraft, only to be feared due to its old reputation, nearly destroying the de Havilland company.

[@davidelliott5843]

Stock and string failures like this lead to USA making all metal aircraft. It also meant they missed the point wood of composite construction as used in the DeHavilland Mosquito.

[@robertguttman1487]

The "Barling Bomber" was designed by the same individual who had previously designed the disastrous British Tarrant Tabor bomber. The fact that the latter had tipped over onto its nose during its' initial take-off attempt, killing the pilot, explains the presence of the over-sized nose wheel on the "Barling Bomber", which was clearly intended to prevent such an eventuality. Although the "Barling Bomber" did not crash, it was no less disastrous because it proved completely impractical. Ironically, although the "Barlong Bomber" was designed specifically to be a night bomber, during WW-II the USAAF's strategic bombing force specialized in daylight bombing.

[@JohnSmith-yv6eq]

It's like night and day....

[@edletain385]

Mitchell was never a Lieutenant General. He was a temporary Brigadier General as shown in the photos you used. He was later demoted to his permanent rank of Lieutenant Colonel and later promoted to Colonel. After a second appointment as a temporary Brigadier General, he was again demoted back to his permanent rank of Colonel. In 2004, Mitchell's posthumous promotion to Major General was finally authorized in the FY2005 National Defense Authorization Act.[ According to the former editor of Air Force Magazine, "neither the Pentagon nor the White House took any action as a result of the authorization," which meant Mitchell was never promoted.

[@aerobat161]

Clearly they were making a point with a forward mindset into the future direction of wartime needs. We need forward thinkers.

[@maercyme61]

It was Lieutenant General Mitchell, not Lieutenant Mitchell. OMG

[@markpatterson4917]

People always forget we generally learn more from our mistakes. Also it flew and didn't crash a win for those days.

[@jmackman]

That is not a $700,000 dollar hanger in the 1920s. Somethings up

[@alanwilkin8869]

They re-cooped there losses on the cancellation of the second prototype, you could build that in the present for 750 000 bottle tops, Probably with the consent of marshall, Britain built ah similar plane, had to to progress I think.

[@ebenezer1690]

God bless Billy Mitchell!

[@alm5992]

I like how it's shaped like a giant bomb, itself!

[@rayceeya8659]

Sounds like it just needed better engines. But it was a bit of a scrap yard build. The Liberty V-12 was a great engine, but way too small for this application. Imagine if they had re-engined it with a pair of Wright Cyclone 9s. Like in the DC-3. Same power for half the weight.

[@danielcruz8347]

Vaudevillian megaphone US Army.across fuselage !!!

[@george6252]

Looks like the underpowered surplus engines were the bomber's demise .

[@nicholasmazzarella2720]

Dark Awesome video. Thanks for all the great content.

[@bradolsen8629]

My thoughts are wow

[@jjeckerm06]

Everything needs a start, however primitive or inadequate!

[@carlinglin7289]

Hap Arnold ordered it burned??? What a loss to a future museum.

[@Steve-GM0HUU]

Although Hap Arnold may have ordered the burning of the XNBL-1, maybe worth noting that Arnold was a supporter of Mitchell.

[@JohnSmith-yv6eq]

And therefore didn't want the rearing of an ugly head from the past to detract from the future of the Airforce he still envisioned and championed....

[@demonprinces17]

Army generals didn't think tanks were the future at that time

[@topturretgunner]

Sadly it was perhaps a bit ahead of its time. The technology was yet to catch up with it’s design intentions.

[@thecooky7744]

I would be interested in hearing more about Mitchell himself or what he was doing how he tried to advance aviation between the wars

[@washingtonradio]

Mitchell was basically PT Barnum at Barnum's worst. Many of his 'advancements' had already been done (see WWI German and Russian strategic bombers) or were concerns by other branches. His most famous 'test' that 'proved' bombers could sink ships was implicitly agreed to by the USN. The USN needed data on what various sizes of bombs would do to various types of ships so they could properly design the next generation with bomb damage in mind. Implicitly the USN privately agreed aircraft could be a threat to the fleet. What Mitchell did was say basically airpower could replace navies and armies which cannot do.

[@shanegagliano6857]

I'm not sure the what the best way to is to make requests for videos but I recently came across an unbelievably unique looking aircraft called the Bell X-14. I'm not sure if you have covered this plane yet but if not, give it a look and see what you can find out. I would be really interested to see some of the history behind it.

[@GermanShepherd1983]

Billy Mitchell was way ahead of his time. It's too bad the US military as usual didn't see it.

[@davidjaeckel776]

Billy Mitchell was a one star general, Brigadier not a Lieutenant general 3 star

[@nicolek4076]

Wonderfully mangled English.

[@martinwarner1178]

It was a lot of things, not one being good. Peace be unto you.

[@tonbopro]

It flew！still covered in Fabric hmmm

[@Capitan0Guinea]

The correct way to address a leutenant general is "general" not "leutenant"

[@paulpowell4871]

Technology begets Technology, already the Super computer builds the next supercomputer.

[@ak_downrange_threat7251]

Could you please do one on the Flying Boxcar/Specter Gunship.

[@michaelpeters7044]

Don't forget the Pacemakers of the cold war.

[@rollfpeters5159]

😀 Great plane - same problem as Do X -- Gen. Michel was right

[@edquier40]

The list of bombers at the end of the show did not include the B25 Mitchell bomber.... just saying

[@robertmarx1954]

Where are the remaining wheels on display at?

[@SKILLED521]

Should have been dubbed The Drag Queen.

[@Trindal]

Lt. Mitchel was fighting a losing battle but it was still the right side. To this day if we used more strategic aircraft we could possibly save more lives than dragging out campaigns to win over locals and protecting a peaceful solution. War sucks. But when it comes down to war, we should save some of the ground fighting folks by using more air strikes over setting up outposts in remote areas that really don’t have a purpose. We see places that woman can’t walk to the market by themselves without being beaten and we have the air power to take it out the groups doing it. They are using hobby grade drones and remote vehicles that can even match the heat signature of a human in the drivers seat. All just to keep “their own people” under an archaic state of law. But we have to tread with it caution because if we kill a civilian that they where using as a shield to hide behind, we have them say we targeted that person who was just a simple civilian. Let’s go in to those areas and take out the ones who wish to not live the way these people are trying to make them live. Even if that’s setting up a complete new city built for their freedom. Then when they kill all the people who chose to stay, we carpet bomb the rest of the city until nothing left moving. Then we help the original residents rebuild a state in which they can be free to go to school, drive a car or go on date and to markets alone if they choose. And then teach a police/military force to keep the bad people out and the good people safe. We really need people to know that war is a hell like no other and if you restrict your military organizations with rules that they are made to follow and the enemy doesn’t have to then you are tying hands behind the back of our men and women. It’s stuff that has caused loss of life of our loved ones to appease a treehugger that should be forced to sit and watch what happens to our troops when captured. To go to the front line and see what happens when the kids in that village that we are trying to help get paid to throw a grenade over a wall and then goes back to. Playing like nothing happened.

[@oceanhome2023]

Look at those huge white wheels !!!

[@JohnSmith-yv6eq]

The natural colour of rubber...before the black is added.....

[@matthewlok3020]

It reminds me of a Tallboy bomb with wings. I guess a Lancaster could carry it when the wings are removed?

[@terrymarshall5480]

Balls.

[@BengalLancer]

Billy Mitchell wasn't Lt.Gen

[@53kenner]

Mitchell did not get court-martialed for promoting the idea of bombers. He got busted for disrespect of superior officers, insubordination, and ignoring orders. For instance, he bombed those battleships from very low altitudes, where he could not miss. This meant the test was worthless because it was much less likely that they would hit a target ship from a higher altitude. This was relevant because ships are moving, and maneuvering, targets -- chock full of sailors who are SHOOTING BACK. So, basically, the only thing he proved was that enough explosives can sink a ship -- which was hardly some mystical insight; navies wouldn't put guns on their ships if they didn't believe that. So, he not only wasted government resources by making the tests meaningless -- he then wanted the government to spend money on more bombers based on meaningless tests. I'd be the last to deny the usefulness of bombers, but let's not get carried away. By WW2, the US was fitting ships with an enormous number of anti-aircraft guns -- including the 5-inch, 38-caliber dual-purpose gun. When lobbing proximity fused shells (meaning, the shells had a small radar which caused them to detonate when they got near their target), their kill rate was impressive. Between that, smaller guns such as 40 mm, carrier combat air patrol, and world-leading damage control -- it wasn't as though warships couldn't function in a world full of dive and torpedo bombers -- which were largely carrier-based. The heavy bombers, such as Mitchell espoused, had to fly at very high altitudes to avoid getting shot to pieces. Various air forces claimed all kinds of kills on naval targets, which greatly amused the company of those ships when they read the paper after getting back to port. Let's face it, gravity bombs were highly inaccurate when dropped from high altitude and they spent so much time falling that fast-moving ships could just turn away. Heavy bombers were an incredibly ineffective weapon against warships and we can safely say that Billy Mitchell was wrong on this point.

[@omartorres5688]

Little did they relieve that in that this strategy would prove its worth in the coming war just ask the Allies

[@MartinWillett]

Several of the film clips show evidence of being shown at the wrong speed. The standard frame rate of 24 frames per second only became universal after "talkies" came in. Many earlier films were filmed at a hand-cranked 16 frames per second. Playing these at 24fps makes for comical jerky over-rapid motion. If in doubt slow it down.

[@WildBillCox13]

A step in a direction.

[@huwzebediahthomas9193]

4, 5, 6, or 7? Why make not make it ten one's, to show everyone how powerful we are, ey? 😎 😁😁😁

[@alohathaxted]

How do you spend 700K on a hanger, but not the engines?

[@JohnSmith-yv6eq]

Political shenanigans; backhanders; mob influence etc. etc.

[@marks501]

How did they measure such heights? Why did these planes at the time have three wings and why don’t we now?

[@JohnSmith-yv6eq]

The loading on the wings had to be kept to what the materials of the time could withstand. Wood flexes after a certain length vs. a certain dimension of lumber vs. the species of tree it originates from. There were no aluminium spars etc let alone wing coverings then..... Those all came within the following 10 years...pioneered by the DC1, 2 and 3.