Tag Archives: aerospace

Boeing 737 vs Airbus A320 family deliveries, 1967 – 2018

In the previous post I shared a graphic with the Boeing 737 deliveries per year per model since 1967 till 2018. In this post, I want to share a few graphics comparing the evolution of deliveries of the Boeing 737 family with the Airbus A320 family of aircraft.


In the graphic you can see the tremendous growth in the past years. From the valley in 1995 (with 145 combined deliveries) till 2018 (with 1,206 combined deliveries) there has been a remarkable compound annual growth rate (CAGR) of 9.6%. The greatest sellers: the 737-800 with 4,959 aircraft delivered through end of 2018 and the A320 with 4,700.

The first time that the combined deliveries surpassed the 200 airplanes was in 1989 (204 aircraft). In 1998, the combined figure surpassed the 400 (450 aircraft). In 2012 they reached more than 800 (870). In 2016, more than 1,000 combined deliveries (1,035), reaching 1,206 in 2018.


The A320 family surpassed the 737 family in yearly deliveries for the first time in the year 2002, when 236 aircraft of the family were delivered (85 A319, 116 A320 and 35 A321) compared to 223 737s. Since then Airbus has taken the lead in the relative market share between both families, with the exception of 2015 (49.8% – 50.2% for Boeing; with 4 aircraft making the difference – 491 vs 495).


The 737 was introduced in 1967, the A320 in 1988, 21 years later. The 737 led the market for another 14 years, increasing the gap in aircraft deliveries. Since then Airbus has been narrowing it: at the end of 2018 the gap was of 1,839 aircraft with 10,444 cumulative 737s delivered compared to 8,605 A320s.



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737 deliveries per year, 1967-2018

Two weeks ago, both Airbus and Boeing have released the figures of aircraft deliveries for the complete 2018: 800 and 806 airplanes, respectively, in what is a new industry record. This is just a quick post to share the graphic below with the evolution of 737 family deliveries per model since 1967 (year of its introduction) till 2018.

737 deliveries per year, 1967-2018

Through December 2018, up to 10,444 Boeing 737s have been delivered, making it the most successful commercial jet aircraft throughout history. In the graphic you can see the different generations: -100/-200 till the mid-80s, the -300/-400/-500 till the end of the 90s, the Next Gen in the 2000s and 2010s, until the introduction of the MAX a couple of years ago. With the steep ramp up in the recent years, it reached 580 deliveries in 2018.

However, it is worth noting that since 2002 Airbus A320 have delivered more aircraft in every single year with the exception of 2015. The 626 A320 deliveries in 2018 have meant a new industry record for commercial jet aircraft.


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Memories of my days in a wind tunnel

Some weeks ago my brother Jaime wrote a couple of posts in his blog about wind tunnels. A first general post in which he described how they work and mentioned some techniques including PIV, and a second post in which he described the acoustic camera.

Master thesis front page.

Master thesis front page.

It happens that, back in 2005, I completed my aeronautical engineering master thesis with a project carried out in a wind tunnel at the Aerospace Institute (Luft- und Raumfahrt) of the RWTH-Aachen. Those two posts brought back some good memories and I thought I could share a couple of them here in the blog. Jaime has worked in a wind tunnel in Audi, and in his posts he included some pictures from other affluent wind tunnels. You will see here the contrast with budgetary constrains lived by universities.

I think that for this post I will be brief in the comments and will focus on sharing some pictures trying to bring you about what we tried to do and how we did it. Directly, from the thesis preface:

This Diplomarbeit is the result of two different experiments. Each one is dealing with different techniques but both share a common aim: the comprehension of the noise generation in the flap-side edge. That is the reason for presenting both experiments in a very similar way in this report, so the reader might see two parallel experiments which final results are analyzed together.

Thus we wanted to measure noise and correlate it with the flow around the flap. How did we measure the noise in the vicinity? “Aha! an acoustic camera!”, and you then remember the arrays of microphones my brother displayed in his post. See here the arrangement we had:

"Acoustic camera".

“Acoustic camera”.

Fancy, isn’t it? Except for which we indeed counted with a single micro, which we had to move to every position of the array and thus repeat long measurements endlessly. 🙂

Aerial view of the experiment.

Aerial view of the experiment.

In the picture above you can see the wing profile with the single micro in the left (to the intrados of the wing).

Once we had made dozens of measurements it was just a question of letting Matlab do the dirty job and plot measurements for each position at different flap deflections…


Noise measurements.

But remember that we wanted not only to measure noise but to correlate it with the flow structure at the flap edge. Let me advance you an image of what we wanted to see:

Vortex structure.

Vortex structure.

How did we make to study the flow? Another of the techniques introduced by Jaime, Particle Image Velocimetry, directly from the Wikipedia:

Particle image velocimetry (PIV) is an optical method of flow visualization […]. It is used to obtain instantaneous velocity measurements and related properties in fluids. The fluid is seeded with tracer particles which, for sufficiently small particles, are assumed to faithfully follow the flow dynamics (…). The fluid with entrained particles is illuminated so that particles are visible. The motion of the seeding particles is used to calculate speed and direction (the velocity field) of the flow being studied.


Typical PIV apparatus consists of a camera (…), a strobe or laser with an optical arrangement to limit the physical region illuminated (…), a synchronizer to act as an external trigger for control of the camera and laser, the seeding particles and the fluid under investigation.

Seeding the flow, recording it with a camera, using a laser beam… boy, doesn’t it sound fancy high-tech? Let’s go and describe it.

See a plan of the wind tunnel we used:

Wind tunnel plan.

Wind tunnel plan.

See an schematic of the equipment and connections we used for the experiment, all placed at the open section of the tunnel:

Schematic of the experiment.

Schematic of the experiment.

See exactly where we wanted to shoot at with the laser beam:


Laser bream.

See from where we recorded the images (camera at the right side of the picture, downstream from the wing):

Our single micro.


See in this other graphic a summary of the technique. The laser emits two consecutive pulses which light the seeded particles. The camera records those 2 consecutive images and a dedicated software measures the movement of each particle thus providing the information of the flow.

Schematic of PIV technique.

Schematic of PIV technique.

So far, so good.

However, it happens that this was the first time we were using the technique at the institute and despite of our reading of references it took us some time, trials and finally asking experienced people to pull the right strings. At the beginning we just either saw nothing or blurry images.

Blurry image.

Blurry image.

After days of running the tunnel seeded with oil particles you can imagine the fog we were in:

Oil fog.

Oil fog.

… and what we needed were two consecutive shots of very well-defined particles. In the end we managed to fine tune everything and get the desired results:

Image of particles.

Image of particles.

Once we had the images, we ran all the correlations with the acoustic measurements of our array of one microphone and had all the data to analyze, draw some conclusions, propose some new paths to continue experimenting and with which to write a nice thesis.

All that was left was to clean up the mess at the tunnel:

Cleaning the inside of the wind tunnel.

Cleaning the inside of the wind tunnel.

But, yeah, who’s got a picture of himself between the stator and the rotor of a wind tunnel? 🙂

Me among the vanes of the stator.

Me among the vanes of the stator.


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North American X-15

I once wrote about how it took me some visits to different museums and reading a book to connect the dots and see what was the controversy in France about the Wright Brothers pioneering first flight.

It takes several museums to get a complete glimpse of the story of the X-15.

This experimental aircraft, powered with a rocket engine, was used to reach the edge of outer space and gather data for aircraft and space design. In doing so, it set several records of speed and altitude. To date it keeps the speed record of any manned flight with over 7,000 km/h (bear in mind that this a rocket engine, vs. the record for an atmospheric engine reached with the SR-71). The aircraft also flew several times above 50 miles, which by then in the USA was considered the limit for outer space, thus making some of its pilots being recognised as astronauts by NASA and USAF. The International Astronautics Federation (FIA), however, sets the limit at 100km of altitude. Still two of the X-15 pilots flew over that height being them also recognised as astronauts by the FIA.

The aircraft itself, the North American X-15, is displayed at the National Space & Air Museum at the Mall in Washington DC (which I first visited in December 2008) and USAF Museum in Ohio, while one of the mock-ups is displayed at the Pima Air & Space Museum in Tucson (which we visited last May 2013).

North American X-15 the National Air & Space Museum in the Mall (picture from Ad Meskens).

The flight tests in which the X-15 set so many high altitude and speed records were performed at Edwards AF Base in Mojave (which we visited in May 2013). At the Flight Test Center museum you can read some displayes about its story.

Rogers Dry Lake at Edwards (public domain image).

Finally, the mother ships from which the different X-15 aircraft were launched were modified B-52 Stratofortress bombers. The two aircraft are displayed in the Pima Air & Space Museum in Tucson (which we visited last May 2013) and again the Dryden Flight Research Center which is also located at Edwards AFB.

NB-52, modified Stratofortress to drop X-15.

NB-52, modified Stratofortress to drop the X-15.

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The Boneyard

The US Air Force’s 309th Aerospace Maintenance and Regeneration Group (AMARG), known as “The Boneyard”, is one of the places that I had wanted to visit since many years ago. Luca and I visited it a couple of weeks ago.

The Boneyard is an aircraft and equipment storage facility located at Davis-Monthan AF Base near Tucson (Arizona). The are over 4,000 military aircraft stored at the place. Most of them come from the USA (not only from the air force, but from other services as well) but there are some aircraft from foreign countries. The aircraft are stored for several reasons and in different conditions.

  • Some of them are maintained waiting for a possible future use of them (be it with US armed forces or through some foreign military sale, that is the case of several old versions of C-130, F-16).
  • Other aircraft are kept so their parts can be used as spare parts for other active flying aircraft (e.g. C-130, KC-135).
  • Finally, there are aircraft which are stored waiting to be scrapped so the metal can be reused somewhere else.
KC-135 partly scrapped.

KC-135 partly scrapped.

Hundreds of C-130.

Hundreds of C-130.

There are whole fleets of retired aircraft: C-141 Starlifter (retired once the C-17 took over their role), half of the C-5 Galaxy fleet (the A versions, due to budget constrains and fleet strategic decisions), the Vietnam-era helicopters Hueys and Cobras

The Boneyard can be visited with a guided tour organised by the Pima Air and Space Museum (I will write about this museum in another post).  The tour is made with a bus which goes through the Boneyard very slowly and making several stops (though guests cannot exit the bus). The guides are veterans from the US armed forces, who have flown or maintained some of those models that you get to see. The wealth of knowledge that they have about them, the anecdotes and stories that they tell during the tour are worth much more than the 7$ that the tour costs.

The place is impressive, overwhelming. Not only there are thousands of aircraft but the seeing of them fully aligned, whole fleets of different models helps you put things into perspective:

  • World commercial airliner fleet (over 100 pax) has about 16,000 aircraft vs. the 4,000 at The Boneyard.
  • The largest airline fleets have about 1,200 aircraft.
  • Spanish AF has 14 C-130 Hercules vs. the hundreds of them you see at The Boneyard.
  • The dozens of retired Lockheed C-5A Galaxy that you can see there have a combined payload capacity of over 5,000 tonnes… which is more than the complete payload capability of any other air force in the world except the US one…

You may want to take a look at satellite images from the Boneyard here:


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Was Orville Wright’s the first flight ever?

Last Monday, December 17, it was 109 years since the first flight of the Wright brothers at Kitty Hawk. However, there was some skepticism in Europe about the flight. I had already read about that skepticism in the book “The Airplane: How ideas gave us wings“(1) (by Jay Spencer (2))

In the book, the reader gets the idea of the skepticism, of how in France there was also a race for performing the first flight and how it was not until the Wright brothers flew in Europe years later (1908) that people got convinced of that first flight in 1903. When I read about that, the idea that came to my mind was French chauvinism.

Let me now start connecting the dots…

Flyer I (picture by 350z33, available at Wikimedia)

  • Visiting the National Air & Space Museum, in Washington D.C., you could see a real scale Flyer I, the aircraft with which the brothers first flew. When you see the aircraft you first notice that the surface controls are at the front of the airplane, or that the airplane has no independent ailerons but the wing is bent at the tip…
  • Reading the book “The Airplane” there is chapter dedicated to the evolution of each configuration item of the aircraft. One of them is dedicated to the landing gear. In relation to the Flyer…

[…] European experimenters put the Wrights to shame by adopting wheeled undercarriages from the outset. The Wrights stuck with skids far too long, perhaps because they viewed their airplanes as scientific proof-of-concept vehicles first and practical machines second.

  • Last summer, when we visited the Aviodrome (3) museum in The Netherlands, we found another Flyer model of the Wrights. This one was a bit more complete: it showed the skids and how the airplane was propelled into the air thanks to a system composed of rails and a kind of catapult.
  • Finally, when reading about French aviation pioneers for the previous post in this blog, I got to read in the Wikipedia article about the Brazilian residing in France Santos-Dumont the following passage:

The Wrights used a launching rail for their 1903 flights and a launch catapult for their 1904 and 1905 machines, while the aircraft of Santos-Dumont and other Europeans had wheeled undercarriages. The Wright Brothers continued to use skids, which necessitated the use of a dolly running on a track. The Fédération Aéronautique Internationale, founded in France in 1905 to verify aviation records, stated among its rules that an aircraft should be able to take off under its own power in order to qualify for a record. Supporters of Santos-Dumont maintain that this means the 14-bis was, technically, the first successful fixed-wing aircraft.

Thus, it was not just simple French chauvinism as the more simple explanation given either in “The Airplane” or Wikipedia article about the Wright brothers may point to, but there was at the time a discussion about the way in which the aircraft were indeed propelled into the air. That is a legitimate discussion, not chauvinism. (4)

Since I am not invested in either position, to me the first flight will always be the generally accepted of Orville Wright on December 17, 1903. That is the one I celebrate (see tweet below). However, you can see how sometimes to get a clearer picture and connect some dots it takes visiting 2 museums in DC and The Netherlands, reading a book and serendipity researching in the Wikipedia. 🙂

(1) “The Airplane” is a terrific book of which one day I hope to write a review. By the way I purchased the book at Boeing HQ in Chicago almost 2 years ago.

(2) Jay Spencer is also coauthor of “747” another great aviation book of which I wrote a review here.

(3) Aviodrome is a great museum north of Amsterdam, at the height of the Smithsonian institution National Air & Space Museum… if only it had free entrance as well. I will have to write about this museum too.

(4) That same federation did not accept as a first flight one made by the French Clément Ader in 1890, because it was an un-controlled flight.


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Iowa Aviation Museum

“What made you come here?”

“We saw a sign at the interstate and decided to come.”

“Great, it’s nice to see that advertisement works”…

This was our first exchange with the clerk at the Iowa Aviation Museum. We had just bought our tickets for 7$ and registered our names in a pristine visitors’ list. I guess we were the first visitors of that day, probably of the week, conceivably of the month, who knows if even in the year.

Luca and I were in our way from Des Moines to Omaha. I thought it would take 4 hours but soon discovered that we would arrive much earlier than we wanted. Having already passed the exit for the John Wayne birth place, when I saw the sign for the “Iowa State Aviation Museum” I didn’t think it twice. I turned the wheel and took the exit.

We had to drive another 10 miles on a more than boring road and then 2 more miles to reach the museum at the aerodrome or the Greenfield Municipal airport.

The museum had some unique pieces from the early days of aviation (e.g. the 1st airplane ever to carry the name “Piper”, the J-2… a one derived from it was the plane I flew in Poland). Nevertheless I wanted to commend the museum for 3 other things:

  • Diffusion of passion for aviation: I find it admirable that in such remote places, they do gather some resources, collect some assets and put up a museum for the delight of fans, to spread the passion for aviation and seed the souls of future engineers.
  • Scheme of contributors to the museum: to finance that museum they have in place a scheme in which both companies and individuals contribute to its sustaining. In exchange they get public recognition in the form of a golden plaque at the Hall of Fame of the museum.
  • Hall of Fame: I also admire the tribute paid to pioneers from the region and people who played a key role in aviation in the form of that Hall of Fame.

In that Hall of Fame you learn that an Iowan volunteer became the youngest aviator in US Army Aviation Section in WWI (Clifton P. Oleson); another Iowan built the 1st multi-passenger seaplane, the 1st twin-engine bomber, designed the 1st honeycomb structural supports and was the founder one of the companies behind today’s Lockheed Martin (Glenn L. Martin); another Iowan, this time a woman nurse, unsuccessfully sought a pilot position at Boeing Air Transport, but influenced the president with her idea of placing nurses on-board airplanes to make passengers feel more comfortable with flying (Ellen Church became the first stewardess in history); and another 2 Iowans were the chief engineer and the first pilot to fly the famous Lockheed SR-71 Blackbird (William J. Fox & Louis W. Schalk).

In the hall you also find out that an Iowan lost the first ever race between a car and an airplane (Carl S. Bates) and that a cloth sewn by the wife of a first cousin of the Wright Brothers is worthy enough to make it to the Hall of Fame (especially if that cousin happens to be the great, great, great-grandfather of a fellow from Greenfield…).

Barnstorming is a term I learnt at the museum (well, you go to museums to learn, don’t you?) that refers to the entertainment that first aviators provided in different villages in the 1920s, where they would fly as in a circus to show the airplanes to villagers, perform some stunts and get some cash by carrying affluent citizens in short demonstration flights. This, also contributed to spread the passion for flight.

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PD: I join the legion of admirers of Luca for standing these #avgeek visits not only stoically but even enthusiastically.


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What was my childhood dream job?

Some days ago, I got an email from a source-of-ideas-for-blogs service called Plinky, from which I have already picked some good ideas to write about in posts in the past (on charities, advice…).

The question I liked this time from the email was:

“What was your childhood dream job?”

I don’t know whether I have been posed this precise question many times or not, what I know is the answer to it and that I have given that answer many times to other questions.

When I was a child I wanted to be an astronaut. I don’t know exactly why, but that was my dream job. Surely, I can recall memories of toys related to space, such as a model of the Challenger that my brother and I played with (I presume it came before the accident), or toys related with Star Wars, etc.

This passion, among other factors, led me to study aerospace engineering, and then work for Airbus, which is not working as an astronaut but is still working in the aerospace business. Many times, I have been asked why I studied what I did, sometimes by corporate HR quizzers, and this is what came as a response.

Would I still want to be an astronaut?

Sure! But, yes, I am not pursuing it. I guess I am just waiting for the moment when commercial space flight costs not 20M$ but about 100k$, and if by then I can afford it I guess I would pay for enjoying a stunt out there.


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