Check 6 Revisits: The Sweeping Influence Of The B-47 On Airliner Design
Boeing's Mike Lombardi joins editors for a deep dive into the B-47, the revolutionary bomber that shaped modern airliner design as we know it.
Check 6 Revisits delves into Aviation Week's more than 100-year archive. Subscribers can explore our archive here and read key Aviation Week articles related to this episode here:
- “The Northrop ‘All Wing’ Airplane”, by Jack Northrop (December 1941)
- Nazi Jet-Bats Which Never Took Wing (October 1945)
- Supersonic Plane and Jet Bombers Revealed by Army Air Forces (July 1946)
- Boeing Stratojet Bomber Heralds Transonic Combat (September 1947)
- What Has Been Learned Flying the B-47 (April 1951)
- Exclusive Report: 707 Designed for Low-Coast Operation (August 1954)
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Transcript
Speaker 1:
When you get in the front seat, even with an instructor pilot in the rear, you must have full knowledge of the aircraft. Its systems, emergency procedures, its capabilities and limitations. Can pay off with your life sometime.
Speaker 2:
How fast does the B-47 really go?
Speaker 3:
What's scoop on altitude?
Speaker 4:
Does the sweat back wing really stall out easier? What's the range?
Speaker 1:
Wait a minute, fellas. To fly the B-47 safely, you must learn it thoroughly. Believe me, you can't learn it overnight. So absorb all the training you can get, absorb it thoroughly. But sit down fellas, I don't want to scare you. There's nothing mysterious about the B-47. It's a good plan, a safe plan, provided you know what you're doing at all times.
Christine Boynton:
Welcome to Check 6 Revisits, where we comb through more than a century of aviation week and space technology Archives. On this podcast, our editors explore pivotal industry moments and achievements of the past while considering how they might relate to the events of today. I'm your host, Christine Boynton, Aviation Week senior editor for Air Transport. And today we're flipping back through our archives to the 1940s. Big Band was on the radio. Betty Grable was on the big screen, and Aviation Week was reporting the idea of a new swept-wing bomber. It was a decade of radical design for both the weird and wonderful and commercial jet airliners as we know them today, can trace pieces of their familiar shape back to this era. Joining me today to dive into this is Aviation Week defense editor, Steve Trimble, Aviation Week senior editor, Guy Norris, as well as a special guest, armed, of course, with their own archive, Mike Lombardi, Boeing Senior Corporate Historian. Thanks for being here today, Mike.
Mike Lombardi:
Great to be here.
Christine Boynton:
So we started out with some audio from a 1952 Army orientation film about the B-47, because that's where we're kicking off today's episode. With the first of the big swept-wing bombers and a real milestone in aviation history and design. A September, 1947 issue of Aviation Week reports;.ex-
Mike Lombardi:
Yeah, well, and based on that, what I've always argued is that, the B-47 is the second most important airplane in history behind the right
If you are familiar with aviation in 1930s, every airplane during that period when it went out to make its first flight, Eddie Allen was the test pilot. He was so well regarded that insurance companies wouldn't insure an airplane unless it was signed on there that Eddie Allen was going to fly that airplane. That's how brilliant he was. So he started out with Boeing as an airmail pilot flying for Bill Boeing's, Boeing Air Transport. And then he went to Douglas, he went to Consolidated, he went to Lockheed, he flew all these great airplanes. But in 1939, he came to Boeing to stay. Bill Johnson, the CEO at Boeing hired him to come to the company and what Eddie Allen did was just brilliant. He created the modern flight test program. He established a flight test team at Boeing, a flight test department, and a scientific approach to flight testing. So that was first thing.
The second thing he did, and this is where it fits into this B-47 story because it's fundamental, is that he went to Phil Johnson, the CEO, and he says, he told me, he said, "Boeing needs a wind tunnel." Now, no other companies, I think Lockheed did start and went, but everybody had to go to the universities to do flight tests or wind tunnel testing. Caltech, University of Washington, MIT and there were, you had to wait in line, for sometimes months to get tests and you couldn't do anything consecutively. So Eddie Allen, he said, "We need a tunnel," a million dollars at that time, 1939. It's the Great Depression. Boeing was actually in a bit of financial trouble at the time, and this was what was brilliant is that, Johnson said, "You know what, Eddie, you're right. We're going to build that wind tunnel."
And another brilliant thing is when they started it, they brought in Theodore Von Karman, the great aerodynamicist from Caltech and consulted him and he told Boeing, he said, "You need to think about making this tunnel capable of doing tests up to nine tenths mach, 0.9 mach." The theory is in his mind, he saw that jet engines were on the horizon, that high speed was on the horizon. And this is another great decision is that, the team at Boeing agreed. And so we had the first high-speed wind tunnel, and because of that, Boeing was able to do all of these incredible tests that led to the B-47. So I think that's an important thing to remember is that, Eddie Allen really is the hero of this story.
And the unfortunate thing about this is that once they got the tunnel going, the war started, Eddie Allen was out testing the B-29, the new super bomber, the war winning B-29 Superfortress. And famously this terrible tragedy occurred where the airplane caught fire and crashed and we lost Eddie Allen. And again, the world's most brilliant test pilot and the scientific test pilot, engineering test pilot set the pattern for all of our pilots today who are engineers and scientists and no more of the daredevil pilot, that they see the right stuff kind of thing that this was what Eddie Allen gave us, and he was just brilliant.
So there's a very human side to all of this, and we forget that. And one of the things that really drove this home for me at this human story was when that wind tunnel was started, that Eddie Allen that he told the Boeing leadership to build. When it opened, the day it opened, they took a picture of the ceremony and it was Eddie Allen's wife. She was given honor of starting out the wind tunnel with George Schairer and in this image, they're still mourning the loss of Eddie. And you can see the pain in their face while they're in this ceremony. And it just brought it home the real human story behind all of this. And that's what's so great about, there's so many incredible people throughout this story. It would make a wonderful Hollywood movie, but that's the foundation for this.
The next great part of the story, the next person, the next hero in this story is George Schairer. Boeing's lead Aerodynamicist, he came from consolidated, he brought the technology of the Davis wing, the long thin airfoil, high wing loading, which was a bit of a heresy at the time, but he brought that to Boeing and it went into the B-29 that airfoil on the B-29. And so he was a very well-respected, highly respected aerodynamicist, brilliant, brilliant aerodynamicist.
And so again, this is the war's going on, it's coming towards the end of 1940, I mean, in 1945, the war in Europe's starting to come to an end. And the Hap Arnold head of the United States Army Air Force was very interested in research and development. He knows that the United States needs to get into Germany and find out about all the research that Germany was working on, aerodynamics, jets, rockets. And so he created a team called the Scientific Advisory Group, and it had Von Karman headed up the group. Dr I think it's Sin from Caltech, was on the group. And then he invited George Schairer and they were given the mission to go to Europe.
And all of them had been kind of thinking about and talking about the swept wing. They were here at Boeing, we were working on a jet bomber as were other companies across the country, and notably North American with the B-45 was first to have one out, but Boeing continued to work on the idea and Schairer understood that there was an issue with the drag increasing as these straight-winged airplanes, as they went faster and faster, the amount of drag increased. And so they knew there was something that... It was a problem and how to fix it. And they kind of had an idea about the swept wing, but not solid knowledge. It actually was, it turns out they'd forgotten about some knowledge they had prior to the war. So Schairer goes to, they fly into Paris, they follow the American Army, United States Army into Germany, and they go to the Hermann Göring Research Lab, this great Luftwaffe research lab at Völkenrode.
And what's fascinating about this research area is that the Germans had done this incredible job of hiding it. There were no roads, no railroads to it, everything was underground. It was hidden in a forest. None of the buildings could be taller than the trees, they were all covered over, they're actually stork birds nesting on top of this building. It was so well hidden. And throughout the war, the allies never had a clue, never saw it, it was never touched. And as a matter of fact when, the story goes when Schairer and the other members of the scientific committee group got there, some of the scientists didn't even know the war was over, and they didn't know what to do, so they just kept doing their work. So anyway, they arrived there and started interviewing these different German scientists, and in particular Adolf Busemann, this great aerodynamicist and Schairer started, they started talking about the swept wing or about the problem that Boeing was having with this jet powered bomber.
And Busemann said, "Don't you remember back in 1935, we all went to Rome for the Volta conference. It was this general, Italian general, Arturo Crocco sponsored this." And they talked about the swept wing and Crocco drew this funny little drawing of a swept wing plane. And they're, "Oh yeah, of course." So Schairer, he wrote this all down and he figured out how the mail system worked, because things leaving Europe had to all be censored and looked through by army intelligence. So he figured out how that worked. I think he wrote on the outside of this envelope that he was sending back to Boeing, he wrote censored or something on it to get it through. And in that note was all of this information about the swept wing. And he was telling the team back at Boeing, back here in Seattle, he was saying, "Here, test this in our brand new wind tunnel, our high speed wind tunnel. Sweep the wing, sweep the airfoil back and see how that works." And so they did, and they found out that was the answer to that problem.
Christine Boynton:
Wow. And Steve, I know you found what was a fascinating paper that Schairer authored and he goes into a very interesting, what was it? A 26-hour flight with some of the names that we were just talking about.
Steve Trimble:
Right, right. Well, so it was a paper that Schairer published himself in 1980 in AIAA. You can look it up today. It's called Evolution of Modern Air Transport Wings. And it refers specifically to this episode. And that was a fantastic telling of that story. I loved every bit of it, and it was a lot in there that I haven't seen in my own research on it. But there was another part of that story too that was happening in the US. Because while Busemann did come to this realization first and then actually published it or presented it in 1935 to an international audience that included Theodore Von Karman, nobody really took any notice of it at that time. And so all the US scientists came back from that and kept working on straight wings. Meanwhile, Busemann starts in a classified setting, starts working on applying swept wings to German aircraft.
Which they didn't actually get, they didn't move very far, I mean, it was mainly just experimental research. I mean, there were a couple of German aircraft that used swept wings, but not really for the purpose of drag reduction. That was for the purpose of Center of Gravity. But meanwhile, there was Bob Jones, R.T Jones at NACA, who, well, not simultaneously, but several years later, but still independently because he wasn't at Volta. Von Karman was there and Jones worked for Von Karman, but Von Karman never told him anything about it and had forgotten it. And so he independently comes up with, "Oh wait, there's this way to increase the critical mach number of a wing by changing the angle and sweeping it back, and that can solve our problem."
Meanwhile, Boeing had been responding to an Army Air Corps RFI. I mean, it was probably called something else back then, but it was basically in 1943 saying, "Hey, jets are coming along. We'd like to figure out how to put an bomber or maybe a transport with long range we're going to do on fighters. That's a little bit easier. But if you guys have any ideas how to do that, we'd love to know because this straight wing problem with this critical mach number problem, we can't figure out how to solve it." So George Schairer is already thinking about this, and on the flight over this 26 hour flight in a Douglas C-54, a DC-Four, he is talking it over with Qian Xuesen, the jet propulsion laboratory later founded China's aeronautics and aerospace industry.
Mike Lombardi:
Big hero for Chinese rockets.
Steve Trimble:
Right. He was the grandfather of Chinese aviation, but at the time he was in the United States working for Von Karman and on this intelligence expedition with these other aerodynamicists led by Von Karman to Germany. And on this 26 hour journey, Xuesen had been, or Qian I should say, had been read into Bob Jones's work, and Schairer had heard about it, but they discuss it on this 26 hour flight, can't imagine, 26 hours from Washington to Paris. And on the way, Schairer writes that, he determines that based on his discussions that this will solve the problem. And that, so getting the wind tunnel data at Völkenrode from the Germans was just this bonus. I mean, he had just figured out to solve this problem for the B-47. And then here's all the research data years worth of research wind tunnel data that he can immediately apply on his own airplane.
But the funny part, the little anecdote was after they land in Paris, Von Karman, after this 26 hour flight, walks up to Schairer and says, "Now, I understand why you want to fly fast." But the interesting thing I found was that, so they come up with this discovery, but then they still have to figure things out because this is a new technology. And as they apply it on the B-47, they find new problems that they weren't expecting. One of which turns out to be high mach pitch up, which was something that really surprised them because up to that point with straight wings, they'd only seen a high mach pitch down or mach tuck, which is a problem that P-38s and other straight wing aircraft had with compressibility.
For some reason it was pitching up a swept wing aircraft like the B-47. And Schairer writes in that paper that they solved that with vortex generators, and he doesn't say how that solved it, but I can sort of imagine, and I'm going to try to put on, I'm not an aerodynamicist or a mathematician of any kind. And if aerodynamic experts want to write letters, please, I would welcome your feedback. Please send them to me. I'm at guy.norris@ [inaudible 00:19:33].
Mike Lombardi:
That's great.
Steve Trimble:
Well, so they solved that problem, but they did that I think by using those vortex generators to reenergize the airflow so that the control surfaces would be more effective to counter the pitch up. They also discovered according to Schairer that the critical mock number increase they were getting was only two-thirds of what Busemann's theory would've predicted. And that puzzled them for a while, and they actually made an important discovery that would have a major effect on transport design as they move from the bicycle landing gear configuration of B-47 to tricycle landing gear. Which is that, if you increase the thickness of the wing root where the wing meets the fuselage that solves that problem, they were able to increase the critical mach number much higher or slightly higher to get closer to what Busemann's theory had predicted for the B-47.
They also experienced some new rolling moments in yacht flight that they had to counteract by increasing the size of the ailerons and flaperons, they needed to really figure out the yaw dampers to counter the Dutch roll for a similar problem. And then they also had to figure out how to beef up the fuel systems because of this low dihedral with a high swept configuration. It meant that the kinds of fuel systems and vents that they were using for straight wing designs were inadequate. And so they had to figure that out as well. So they came up with that solution, but then there would create a whole bunch of more problems that they just aerated so quickly through. That's one of the more impressive things that they got through all those so quickly.
Mike Lombardi:
Yeah. And that's why I think it's... This is such an inspirational story, because at any one of those things, they could have just thrown their hands up and said, "Boy, we don't know what to do." But they kept pushing through and it was always some simple thing. It's say, "Well just go over to the shop and get this little piece and this little piece," like you mentioned, the Dutch roll. Bob Robbins, the test pilot, some of the team that was watching on the ground, they could see the plane kind of doing these S turns through the sky and they're like, "Hey, Bob, did you notice the plane?" "No, I didn't really know." And then they paid attention to it. He's like, yeah, there's this role. And so they just built a yaw damper, they called it Little Herbert. And then even in that it was like, "Well, how much deflection and well, how about five degrees? Let's go with that. And should there be feedback for the pilot?" Just these decisions, these real important decisions, they're like, "Let's just go ahead and yeah, no feedback."
And they perfected it right there. And that's something they found an inherent problem in the swept-wing jet with the Dutch roll, and they fixed it, and then it was no problem. I think even some of the, it was Douglas had a turboprop they were trying to pitch and they were going to use that against Boeing and said, well, look, their jets are unstable. And the Air Force was like, "No, no, no. Boeing's got it fixed. It's not a problem." And so it's just brilliant all these moments that could have just ended this, and they just pushed through with just using their instincts and their inherent knowledge and just believing in themselves. And that's what amazes me. Again, it's just a great people story. Right?
Christine Boynton:
Guy. I think there's a great story in here too about a secret screening in Kansas that has to do with overcoming some of these challenges. Is that right?
Guy Norris:
Yeah. Well, just before I do go into some of the quirky parts of the flight test story, which was predominantly in Wichita as well, we have to, even though the aeroplanes were built originally in Seattle, most of them, anyway. Mike mentions this is a human story. It's very much so. And when I think about Schairer, for example, was only 26 when he joined Boeing in 1939 coming out of Consolidate. And of course, he'd been to Caltech because Consolidated had sent him up there, and that's where he got his great sort of wind tunnel experience, I think to start with. And Mike had mentioned Eddie Allen and the tragic loss of him, that terrible crash in 1943. But the weird thing was that as a result of that, and Mike probably correct me if I'm wrong here, but as a fallout of that, the whole organization and engineering and aerodynamics had to be restructured slightly.
And because of that, Schairer was directed through the ranks really, and rose up. So by the time that Boeing had brought on Theodore Von Karman and John Markham, these MIT brilliant people from this best theoretical aerodynamicist from MIT, to help consult on that wind tunnel, the advanced high-speed wind tunnel that Mike mentioned, Schairer was on his way up. And Ed Wells, who was a key figure at that time, just appointed chief engineer, he was the one that said, when Hap Arnold's team came to him to say, who should we send? He was the guy apparently Mike, right, who said, "We need to send Schairer, he'll go." And Schairer had already said, we need to go faster, everybody knew that. But here's another weird thing. So when this group was getting together, who should go to Germany? And that sort of thing, two of the fellows that Schairer remembered was Bill Sears, who, and everybody who knows aerodynamicists History would know that he was one of the two people, Sears and Haack who put together the Sears Haack body, the classic lowest theoretical wave drag in supersonic flow.
It's the shape that anybody who's a student of that will learn about today. So it was that Sears. And he was also, by the way, lead developer of Jack Northrop's flying wing programs, by the way. So him and Xuesen, who Steve had mentioned as well, who by the way, we put on our front cover in 2008 as the father of China's rocketry, the space program. They went to Princeton and they were in the run-up to this. And they of course bumped into Bob Jones of... Who really Schairer does actually credit the end of the day with the reason that they really were looking at all this. And what I didn't realize was that Bob Jones was basically, and according to Schairer, self-taught a poor boy, he calls him. He grew up as an elevator operator in the library of Congress. Actually he turned out to be an operator in the house office building in Washington DC. But he spent his spare time studying in the Library of Congress where he met this guy called Albert Zam, who was chief of the Aeronautical division of the library.
And because of all these amazing people he met, and Bob had been a left's college or something to go to a flying circus. I mean, the guy was obviously crazy about flying. So he'd read all in the elevator while he was waiting to operate the lift, he read mathematics books. And because he met all of these experts who came in and out of the elevator, they all advised him on what he should read next. So through all of this process, he sitting there in the elevator, he invented the idea of the thin wing theory. I just love all of the fact that you've got all of these amazing characters who are household names to anybody who's at a science aerodynamics conference, and they were all bumping into each other almost in a haphazard way.
So anyway, so as Steve mentioned, they went on this torturous 26 hour flight to Paris. And the bit that I remember hearing about from Schairer was that he said that Karman was a great pacer. He would always be pacing up and down. So when they finally got to Orly after flying via, I think he said Gander and Keflavik and the Azores and 26 hour Odyssey, they looked down into the apron, there he was pacing up and down, and that was the bit of story about he always wants to go faster. So anyway, so moving forward then, getting to flight test, the great things, I think about the story of the fact that because swept wings were so new, they thought, well, hang on a minute. You've got a thing which has actually got a smaller span. It's got more weight because it's a dry wing. In this case, you have to structurally compensate for that.
And because it's a dry wing, you don't have enough fuel either, so how on earth are you going to meet the mission? But of course, as you pointed out, Mike, they began to find out there was actually more advantages than they thought. They had a high wing loading of over I think 105 pounds per square foot. But they kept coming into these unexpected discoveries like washout at the tips know improved cruiser, and Hey, Presto, you get bending moment relief because you've got Jets underslung outside on the wing. So-
Mike Lombardi:
Oh, no, I would just say that, that was another one of these that, and maybe even in a little bit, we can talk about Ed Wells and the engines, but that was one of these moments where they were trying to figure out to place the engines, and they called it the broomstick test. Where they put a little model of a nacelle, they called it the potted engine, and they placed it in different positions around the airfoil in the wind tunnel. And they found the optimal position was below and forward. And that's the way it is today. And that at the same time, it solved a turning moment that they had with the wing. And lo and behold there it solved another problem they hadn't even foreseen. It's just brilliant. And one more, one more, and I'm sorry to interrupt you Guy, but there's so many great stories.
The other one is the question about what degree of sweepback. And again, it was one of these moments, they're in the wind tunnel trying to decide about how to make this model of the wing what degree. And this one of the aerodynamicists at Boeing Vic Ganzer, he stepped up and he said, "Thirty-five degrees, let's go with 35." And it was brilliant because after they refined the test, they settled at 37 as the optimal position, and Ganzer, he went on to be a professor at the University of Washington and trained generations of Boeing engineers. But it was just brilliant. And all of a sudden just these guesses, they may pull just your calculator out of your pocket, your slide rule, and do a quick, oh yeah, this is it. It's just incredible. They were so brilliant and so confident in their abilities, and it's just what an inspirational moment this was.
Guy Norris:
I'm fast as well. I mean they went from deciding to do this, to flying it in about two years. When it flew in December, 1947. That was literally two years since they decided to come to get the thing built. I mean, and just a couple of things on what you were saying, and Steve had mentioned the wingtip unloading, so many lessons learned that they had no idea about, leading to that sudden instability. And of course they realized, well, the tips of the wings, because they're swept, they're halfway back towards the tail. So it's like, wait a minute. Well, that's probably why they're be to act like elevators in a sense. And so, of course, then they realized that they could compensate by the changing of the stabilizer angle, and then they had this curious bit of body bending. So they were beginning to figure out, wait a minute, this is aeroelasticity a transonic aircraft.
It's like, whoa, what's going on? And then aileron reversal, of course, the creation of spoilers or development of spoilers to help cure that. And I think Ken Holtby you know that name as well. He was the Air Force officer who was contract the contracting officer for the XB 47. And he said, we had this great floppy flexible airplane and we didn't understand it. And then the Dutch roll that you mentioned, and little Herbert, I'd love the story that Bill Cook, who was the XB 47 aerodynamics unit chief said. He said, we basically just said, "Well, we've got to do something." And they brought together all these bits. They had a turbo wastegate control from a B-29. They found a transformer and a servo motor from somewhere else, and then they kludged it together with a Honeywell gyro and a press that we had this sort of Heath Robinson creation, which today still is in every Boeing, not obviously a modern version of it, but it's still your damper and it's still flying today.
And then my final bit, little Herbie, the flow separation. So this is the bit to answer Christine's question about where Wichita comes in. The flow separation, which they didn't really expect, and Steve mentioned this before, was this outboard section where the airflow was separating during maneuvering and transonic accelerations and causing this sudden picture. And of course this magic formula of vortex generators. And NASA had previously, or NACA, I guess in those days, attested them, but on a straight wing. So again, the theory was there, but nobody had really looked at this in a swept wing. So to figure out what was going on, they tufted it to completely, today it's an accepted way visualizing the flow, but how do you record what's going on? So they put a 35 millimeter camera on the top of the fin, which was also swept again, another innovation. And to look to focus on the tough thing that they could see from the camera.
So this was great, except when they got back to Wichita, they realized that nobody had a 35 millimeter projector. So they were okay. So they went out, went downtown Wichita, rented out a local cinema, a movie house. And because it was still classified, I think test pilot Dick Taylor, who's one of the test pilots, remember this, he said we had to darken the house, seal all the doors, and then of course the projectionist couldn't be read into the program. So the projectionist had to operate the machine, but he wasn't allowed to look at the screen. So they had to sort of say, he had to operate the lens to get it in focus, and they would say, "Left a bit, right a bit. That's good." But he wasn't allowed to look at what was going in the screen. Anyways, good stuff.
Mike Lombardi:
Yeah, it was just brilliant. So many things that they discovered, and again, they just faced these issues and it took them head on and with just this incredible confidence. Yeah.
Guy Norris:
There was one other thing I thought was worth mentioning. Obviously the German, as Steve mentioned, the data and the fact that the Germans had done a lot of the basics and were kind of backed up what they already beginning to suspect. But there was some other discrete elements of German technology, and I think even Dick Taylor might've mentioned this, the weird thing about the B-47 was the engines were so primitive. All of these early turbojets took a long time to spool up and spool down 30 seconds in the case of these original GE engines. And they had to... So that means when they're coming in on approach, they came in real hot. So they would be coming in over the fence at about 140 knots, touchdown at 136. They had to keep the engines really spooled high. And of course, they didn't have reverse thrust. They didn't have anti-skid brakes. None of that had been invented that time.
Mike Lombardi:
Not yet. Not yet. They were working on it. Yeah.
Guy Norris:
Yeah, right. And so Dick Taylor had said that they'd been flying B-17s down to Antarctica, I think for the first time, and they were worried that the things wouldn't be able to stop on the ice. So what they'd come up with was an idea of throwing parachutes out of the waste gunner positions. And they said, "Well, why can't we do something like that?" So they did get, there was a guy from Operation Paperclip, which was the great allied plan to get as many of these people as, like Von Braun for example, was a paperclip guy. These scientists and engineers, and he was working, I think at Wright Field by then, and he'd invented this ribbon shoot which had been developed for the Arado Ar 234 Blitz bomber. And that was what they ended up using.
Mike Lombardi:
So isn't that brilliant? And actually I think Dick Taylor, and they talked about flying the B-47, how the airplane would just continuously just glide over the runway. Because it had the high lift devices when it was coming in, so it's got good lift. And with the bicycle landing gear, they had to maintain pretty much the same attitude that the airplane would have when it was taxiing. That was not just because it was hot, but it was also just, it didn't want to land, it wanted to stay in the air. Yeah. Well, that was brilliant. Yeah.
Guy Norris:
Hence the training video that Christine introduced us with. It was pretty a handful, basically you might say.
Mike Lombardi:
That was one thing about the airplane is that, as flying the airplane, you had to constantly fly the airplane. That the high speed when it got up to altitude and speed, the high speed stall and the low speed stall were just a few knots from each other. So you constantly had to fly the airplane. But it was such a pioneer in so many ways. And what they learned, not just in developing the airplane, but as you're saying with pilots like Dick Taylor and Brian Weigel and what they learned flying the airplane and passed on, it is just brilliant.
Christine Boynton:
And of course, all these technologies then lead the groundwork for the 707 and really what we know great commercial jet airliners of today, so.
Mike Lombardi:
Right, right. And the one other piece of this, and if you don't mind, I wanted to talk about Ed Wells and his brilliant contribution because there's two parts of this brilliant discovery. There's the swept wing, but there's also the position of the engines. And this was a really great story too. One of the things that Boeing understood very well was engine, what they during the war, all right, so our bombers B-17s, B-29s, they knew that what caused most of those airplanes, the loss of those airplanes was when they took damage to the engines. So enemy fire would hit an engine cause a fire, the fire would spread to the wing, get to the fuel, and that's how most of our bombers were lost in combat. So one of the things they wanted to do with this new bomber was get the engines out of the wing. And that was the conventional thinking.
You look at all of the jets, these first jets that were developed, whether it's the B-45 or what Consolidated was doing what Martin did in competition. They all had the engines in the wing that was a conventional thinking. And Boeing wanted to get away from that and they puzzled over this. And even they made a design where they packed the engines onto the fuselage. So they had four jet engines right behind the pilot on top of the fuselage, and they took that back to right field, and colonel P. Warden was evaluating this, and they said no, there's just no way. And they showed them, they had done a test on a P-80 where they shot the engine while it was running. And here's this, I guess they said something like 18 foot long blowtorch. And they said, "We don't want this on the fuselage. That's not a good idea." So plus it made a really ugly airplane. It was hideous. And we all know that ugly airplanes don't go anywhere.
So Ed Wells was back there at Rayfield and on his way home he puzzled over this. And another point I want to make towards the end too, just about engineers and how some of my thoughts about educating engineers. But anyway, Ed Wells was a brilliant artist. He was a painter, did beautiful paintings. And so on his way back, he puzzled over this whole problem and he made these drawings where he put the engines, people had them in pods and he hung them off the wing. And this is where that idea of put the potted engine idea, hanging them off of wings, and the cells suspended off the wings held by struts. And that's, I mentioned earlier, they got back to the wind tunnel in Seattle. Again, Boeing had this wonderful facility to do all these tests, and they did that broomstick test and determined that was the best placement for the engine. So they invented this brilliant invention of hanging the engines off the wings. And so that was it.
Guy Norris:
Sorry, Mike, do you have those drawings in the archive?
Mike Lombardi:
Yeah, yeah. Right.
Guy Norris:
Really? Wow.
Mike Lombardi:
Yeah. So it's just brilliant. And that was a part, and you speak about how brilliant Ed Wells was, I mean George Schairer. But Ed Wells just a man, of course, we still honor him as our greatest engineer here at Boeing, and he continues to inspire our engineers, but it was just brilliant what he did and thinking up this idea amongst other things that he did. So those combinations together, that was what was brilliant, is that they brought these two big items together. And again, it's because of the brilliance of a particular person, these wonderful people stories. And they made that combination made the B-47, this beautiful jet, and I think it is one of the most beautiful jets ever. It's just right? Even if I didn't work for Boeing, I would think that it is just a beautiful airplane.
Guy Norris:
And you're right about the human aspect. I remember Phil Condit even saying that Ed Wells had advised him on some aspects of when they were doing the seven five and seven six and saying, we made the big mistake of making the 707 gear too short. So when Douglas stretched the DC eight, we couldn't do it. So he said, "Never do that. Make sure the seven fives got some big tall gear." And he said, "That's why it looks the way it does today."
Mike Lombardi:
Absolutely. And that's a great point is that Ed Wells, he started, what, 24 years old? He was the assistant chief engineer developing the B 17. 24 years old and then he was here through the 767 he was on the board of directors. So it's just the people that did this. And I think it would make a brilliant movie. It would be a wonderful movie.
Guy Norris:
Yeah. Who's going to play Schairer?
Mike Lombardi:
Oh, right, but yeah. And so on one final point to make about this, about the B-47, and I know you want to go on and talk about some other things, but this was such, the Air Force called it a revolution. And for Boeing, we looked at the Boeing, our marketing team, our communications team looked at what was going on and they said, "We're moving into a new area. We're moving in the future. We need to change. We need a new trademark, a new logo for Boeing." And so they created the Stratotype. So our Boeing name is at an angle. That angle is 37 degrees because of the B-47. And that's an official brand, right? That's just not me saying that is our brand, is that the angle of our Stratotype that we use for the Boeing, for the Boeing logo and other Boeing official names is 37 degrees because of the B-47 wingsuit.
Christine Boynton:
I do want to get into more of the designs of the time to bring it back to the forties, more of the weird and wonderful. But before we get to that, I just want to come back, Mike, to you to ask about some of the weird and wonderful you may have found in your exploration of the archives before this podcast, what did you uncover?
Mike Lombardi:
Well, I think one of the things I want to share is that some of the things we talked about here, one is that, Schairer’s letter that he sent back that started all this research is still in existence and it actually ended up at the Museum of Flight where they keep it in a safe there. But I talked about Ed Wells drawings, which we have here, and one of the more interesting collections we have is that all of this research that was done in Germany, all these, the research that United States brought back from Germany, all the documentation, a lot of it was microfilmed. We have that, we have the entire set of these documents. A lot of them have been translated, the microfilm through the various mergers that we've had with Douglas and North American. North American gathered up a lot of this, and it was used for the F-86 as well as a little bit of Schairer's letter, but we inherited that.
So all that information is part of our archives along with the memories of these brilliant aerodynamicists and engineers and leaders who did this. We have this tremendous archive with all of those records. So it really is, and the photography of all these wind tunnel tests and those actual tests we talked about back in 1945, '46, we have all those records here. They're preserved in our archives. So it's an incredible treasure.
Christine Boynton:
That's amazing. And so what else was being explored around this time? And Steve, I think I'm going to toss it to you. I know we had a lot from Jack Northrop around this time, and we kind of touched on that earlier.
Steve Trimble:
Yeah. And Jack Northrop. Yeah, he's another great story too. We could go into, a Guy was talking about Bob Jones's story. I had no idea that he was elevator attendant to learn aerodynamics at the Library of Congress, that's incredible. But I mean, Jack Northrop is another just amazing character. I mean, he never went to college, he graduated high school in Santa Barbara, eventually started working for Lockheed and then went to Douglas. But he had this idea, this vision for flying wing aircraft. As far back as the early 1930s, he started working on a series of his own designs of flying wings with the N-1 and the N-9M and sort of in the middle of the war as he's doing other things like the P-61 and subassembly manufacturing, he keeps working on this and gets the Army Air Corps interested.
And with the idea of flying wings and whether straight or swept, the idea was that you can just get a lot more aerodynamic efficiency if you don't have this big fuselage just along for the ride, that the payload and the crew compartment is all enclosed within the wing. And at the time, the structural, I mean the aerodynamic efficiency advantages were there, but the control mechanisms for the aircraft were not efficient quite yet, especially to handle the adverse yaw. The configuration like that creates without a vertical stabilizer. And that would later be addressed through fly-by-wire and other types of techniques, control surface techniques by the Air Force. For a while, norther tried to get airlines interested in the idea, but there were some passenger comfort issues in addition to just the safety issues that had never been fully addressed, or at least it wouldn't be for a while.
Of course, that would come back later on as the Air Force not only saw the aerodynamic efficiency advantages for a non-human payload especially, but also a stealth advantage because you don't those vertical tails and 90 degree points in the design quite as much as you would with a standard tubing wing. But then, I mean, all through the history of the industry and the technology, there's been attempts to try to figure out how to do this better, how to make things more efficient and not always making the engines more efficient, which is usually the sort of the default. Just kind of cleaning up the aerodynamics as best as possible and then trying to do some huge generational improvement with propulsion technology. But not too many of those have worked out too well. I mean, you think about the Avro Canada, WZ-Nine, essentially a flying saucer that they attempted in the 1950s with US Air Force funding, that didn't work out so well.
Bob Jones, who we heard about in his involvement with NACA and the invention of swept wing technology, he came back into the picture with this idea for the oblique flying wing, which was to come up with a wing that it was kind of like a straight wing at low speed at takeoff landing and other low speed configurations. But then to address these critical mock number concerns or issues, you have with higher speed flight and high mock number flight, his idea was to simply rotate the wing 37 degrees, 45 degrees, whatever the right number would be for that airfoil. And they tested it through a NASA and DARPA program. But I mean, there are some issues there, especially if you want to scale it up, especially if you have engines embedded on the wing, they've got to translate as the wing changes angle as well. That creates some issues.
So there was never a transition path for that. And then along the way, another, I guess, you might call it legacy Boeing project, started out at McDonnell Douglas by Robert Liebeck came up with this idea with the blended wing body. So you have not quite a flying wing, where there's a distinct fuselage, but it's blended into the wing in a much smoother way than you see with a tubing wing configuration, which incorporates some level of blending as well in all modern aircraft, you see that. But that was the idea. Boeing and NASA tested that out with the X-48. That again, brings you a much higher aerodynamic efficiency. Like the triple seven is sort of the gold standard in a tuba wing design with, I think it was a 19 lift over drag. Mike Lombardi can correct me on that. But then what Bob Liebeck was saying was that we can get to lift over drag ratios of 26, even higher perhaps, by going to those.
The downside is it is a lot harder to build. It's not a circular constant section. There's very little constant section in the aircraft. That's just a harder thing to build. It's harder to pressurize because pressurization smooth circular type of vessels, not things with 90 degree angles. So then you have to create these circular vessels within it, which reduces a little bit of the structural efficiency that you're gaining from the blended wing. And then there's passenger comfort, egress issues and all that kind of stuff. And that has been talked about and talked about, but we're still at this point where we're trying to figure out what that next leap in aerodynamic efficiency technology will be. Really since the sweat wing, there really hasn't been anything huge at high speeds, and we can't just keep relying on the propulsion to kind of bail us out perhaps. So there are some new projects and I think Guy's got some more to say about those things.
Guy Norris:
Yeah, thanks Steve. And just to make the last point is just to build on what you just said about Bob Liebeck and his blended wing idea was that there are companies, there's a lot of them actually now all trying to push the blended wing body concept like Jet Zero for example, with a different twist in each case. Boeing and NASA of course worked together on the ways of getting around the pressure vessel with the PRSEUS Stitch composite structure ideas. So it's amazing what innovation is coming out because of that.
Steve Trimble:
PRSEUS. PRSEUS, Pultruded Rod Stitched Efficient Unitized Structure.
Guy Norris:
See, that's why we love Steve on these. I can ever say, is it PRSEUS or PRSEUS? Anyway, nevermind. Yeah, and as you quite rightly mentioned, we've been through the move to super critical aft loaded designs like the triple seven, of course, as you mentioned, a kind of gold standard. Improved them in some cases with winglets like the 737 family of course famously did that. And then recently, well, I'm sort of saying in the last 20 years, I guess we've seen the introduction of composites, which are stiffer of course in structurally stiffer, and that enables these much higher aspect ratio designs, which is really the ultimate way of developing long-range cruise efficiency. And one of perhaps the ultimate expression of this'll be the extended wingtips of the triple 7X because that really maximizes that benefit. And of course going to the composite wing for that derivative.
But what do you do beyond that? And so this is where it gets really interesting. The latest is, of course, Boeing is working with NASA on sustainable flight demonstrator, which in 2023 was christened the X-66. And it is just part of this, everybody's efforts to try and get to net-zero carbon for a next generation single aisle at some point. And so this is called the Transonic Truss-Braced Wing TTBW, not easy to say, which is why a lot of people love the fact it's now called the X-66. But anyway, they're basically looking at this. They're going to do a test program where they're converting at the moment an MD-90. And what you basically have is this high mounted slender wing structurally braced by trusses. And the idea is that it'll be in-flight test by the end of the decade. And most of the design helps in reducing drag, because the high aspect ratio reduces the induced drag while the low thickness that you get decreases the wave and form drag.
Another good thing about it is you can also get a much shorter cord. So that gives you a much more opportunity for increasing laminar flow, which is like this sort of golden, the goal that everybody's driving for. That's the last great frontier of untapped efficiency in all of these designs. How to get more laminar flow. Now the problem is that, if you unsweep the wing, it goes back in a way back on itself, back to the old days of having unswept wings. That increases obviously the cord wise length of available laminar flow due to the high transition Reynolds numbers and that sort of thing.
And the friction drag has decreased as well. But, on the other hand, unsweeping as an adverse influence on the wave drag. So what you've got to do is really balance these two factors. So if you can get a final sweep that balances between these two trends, hey presto, you might have it. And that's what Boeing's really looking at with this, because they've decided they can do a Transonic Truss-Braced Wing with sweep. And that's the great big experiment here. So generally, adding truss members reduces the drag actually weirdly, and increases the lift to drag ratio and therefore decreases fuel weight. So you have virtuous cycle, but it's still as many unknowns. And I think that really what we're looking at here with TTBW X-66 is kind of like getting to the nearest equivalent we've seen really to the great leap that was made with the B-47.
And even NASA have said that, this could be the dash 80 moment again for Boeing, because in the future, the B-47 ultimately evolved as Mike had said, towards what became the dash 80 demonstrator. And that was a pivotal moment, again in Boeing's history and in fact in the history of world air transport. So I don't know, it's the newest wrinkle, but it's the only thing that's happening apart from the rebirth of blended wings in a serious way in subsonic transports.
Christine Boynton:
And from a historical perspective, Mike, when Guy's talking about maybe the next great leap like we saw with the B-47, I mean, how should we be thinking of, are there any lessons that you can kind of identify from the archive, from these past moments that should be on the top of mind as these technologies progress? And I think earlier you said you wanted to mention something about engineers.
Mike Lombardi:
Well, and I was going to say from a historical point of view, that I always think of the Bellanca Aircruiser. Just in my personal opinion, I think it should be the X-66 Air Cruiser. But a little more serious on that, really going back to the foundation of the Boeing company and Bill Boeing, that there's a DNA that he put in corporate DNA in our culture that he said that his famous statement about never letting, always that we're pioneers, always be looking for the latest innovations, latest discoveries, and get those onto our airplanes as soon as possible, that pioneering spirit. So there's a pioneering spirit. There's also a spirit of, a can do spirit that goes together with that. That has been foundational, and I'd say across the aerospace industry, that's just something that's part of being an engineer, that you have that.
And I always think about the space program, going to the moon and that effort that we started out with nothing. We started out with what Jupiter boosters that were exploding on the launch pads that, and then all of a sudden we're planning to build this giant Saturn booster that's going to go to the moon and did that in just less than 10 years. And it's just amazing. And as Kennedy said, we do these things because they're hard. We choose to do these things, because the difficult things. And that Boeing, I was think with people like Wells and Schairer, Jack Steiner, Joe Sutter, these famous people that designed these airplanes, they understood that. They understood that if you wanted to motivate engineers, you give them, the Steiner said this about the 727. If you want to motivate your engineering team, give them something they think is impossible and they're going to jump into it.
And so that's, I think, the important lesson. And going forward, that is going to be a constant. And one of the things that go, as far as educating engineers, one of the things, one of my soapbox issues is that, for a couple of decades now, we've really enforced this idea of STEM education, really focusing on science, technology, engineering, math. But when I look back at these engineers from these early days, and I knew them and I talked to them, and when I talked to Joe Sutter, for example, and he would say when they were developing the 737 and trying to figure out where to put the engines, he said it just looked right to put the engines under the wing, the airplane looked right.
And I hear that from a lot of these, sadly, now they're gone. But they would always say something like, "My gut feeling, or I looked at it and it was, this is the..." They didn't say, "Well, I went back and I used my computer tools or did some calculations." They trusted their instincts. And what the difference was, and I mentioned this with Ed Wells. They had a classical education where they were taught art, they were taught literature. And so in other words, they use both sides of their brain. And right now, we are focusing on just half of your brain. And you need that creative side of it to be a great engineer. And that's why I say that in good engineering, there's actually art, there's beauty. For me, I look at the Mustang, the P-51 and the conical shapes and all that that they use, the combination of math and art. And so this is, I think is an important mess. Guy's going to show me he's got his... Oh and yes, I can't forget the Spitfire, I'm sorry. The greatest airplane ever.
Golly, I've learned that lesson too. Don't ever mention the Mustang without mentioning the Spitfire. So these are just beautiful, beautiful airplanes and the art, it is the art in engineering. And so we need to remember that. So going forward, encouraging that can-do spirit, that pioneering spirit, but also encouraging engineers, encourage them to, we need to do both sides of our brain. We need to have that spatial part of it where we can see problems and work them out in a spatial format as well as a linear format. And that's what these engineers had, and that's why on the B-47, they were able to, they've come across a problem and say, "Oh, let's do this." And they were right. It was just amazing, all the steps, every step where again, like I said, they could have just ended the program, throwing up their hands. Maybe that's how it would be approached today, but they were able to push through, and I think that's one of the reasons, one of the big reasons is that they were just brilliant and they were trained to use their entire brain and solve these problems.
Christine Boynton:
Wow. That's amazing. Both sides of the brain. I love that. As an English major, I love that.
Mike Lombardi:
And as a history major, yeah.
Christine Boynton:
Right, right.
Mike Lombardi:
Right. Yeah. Yeah.
Christine Boynton:
I guess for the final, as we're kind of wrapping this up, I know we could talk for another two hours then I would love to. But for our final question, I guess I kind of want to get your perspective on this, and I'll start, Steve, you might have the shortest answer, so I'm going to start with you. Are either Truss-Braced Wing, or blended wing body likely to replace familiar tube and wing within our lifetime.
Steve Trimble:
We live in a world that the B-47 created for high subsonic transport and bombers. And I mean, we just haven't found a way to beat that from an overall perspective. Which includes how you integrate it into an airport, how you refuel it, how you maintain it. Those are all important considerations. But part of that has been driven by the fact that advances in propulsion have always bailed us out on this drive to increasing efficiency more and more. And the question is, can we squeeze more out of that propulsion side than we already have? There are efforts a foot with hydrogen power, which we've covered just in a most recent podcast, that are not progressing that quickly. So that's a long answer, longer than you were expecting, but it's going to be hard to beat a tube and wing. They're trying to do it, but they're going up against a mountain of a challenge when they do it.
Christine Boynton:
Guy, what do you think?
Guy Norris:
Yeah, there's no argument or anything Steve said there. I would just add that, what we are now looking at is maybe a diversification, a period where we've never had the opportunity really to expand beyond tube and wing in a realistic way. And I think now thanks to several innovations and the becoming innovations in things like distributed propulsion, maturity and different structural capabilities and design techniques, I think there will be an opportunity at different scales for new shapes in the sky. So, for the big long haul, the classic, the 777, A350, ,787, I think those are going to stay. I think it's going to be difficult to replace that. But in the smaller markets, and in maybe the 737, A320 area, there is an opportunity for new innovations and things like TTBW, kind of those shapes.
And as you get even further down the scale, some other things too. I mean, look at the advent of EVTOLs, for example, maybe, but the point is there are niches developing. And I think within that, even blended wing bodies have an opportunity in that mix. So I wouldn't discount it, I think that hopefully within our lifetimes, we're going to see some big changes and new shapes in the sky.
Christine Boynton:
Awesome. Excellent. Well, thank you all. And on that note, I think we'll wrap this episode of Check 6 Revisits. A very special thank you to Mike for joining us for this today. And thanks also to our podcast producer Corey Hitt and to Steve and Guy. For links to our archive check the show notes on aviationweek.com, Apple Podcasts, Spotify, or wherever you get your podcasts. And to delve into our archive for yourself, Aviation Week subscribers can head to archive.aviationweek.com. If you enjoyed the episode and want to help support the work that we do, please head to Apple Podcasts and leave us a star rating or write a review. Thank you for listening and have a great week.
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