history VWTs

The history of wind tunnels!

31 August 2017

Just as in all areas of life, it’s easy to take for granted what has come before. ‘Back in my day…….’ I’m sure you’ve heard this throughout your life. On the DZs is no exception. In skydiving we take for granted the efforts, the trials, the errors and injuries of the pioneers of our sport. Everyone who has helped progress the gear, safety, bodyflight techniques, canopy design and control and coaching methods has benefited us now in a way we can never truly appreciate, because we weren’t there.

Wind tunnels are no exception. They have evolved bodyflight in a way no one could have predicted ‘back in the day’. They will have affected your skydiving even if you’ve never used one yourself. Because others around you will have used one of them. Knowledge has a habit of spreading like fire. The development of wind tunnels can be traced back to the 1700′s. I hope to take you on an interesting and slightly geeky adventure through this history until the present day. Now, I am neither an engineer, historian nor journalist. So please excuse any inaccuracies in this story I’m about to tell, just sit back, grab a beer and turn the fan up!

During the 18th century a bunch of rad dudes probably with fat moustaches and bowler hats were trying to make these flying machines. The inspiration for their designs, as with many engineering marvels, was taken from nature. They were pretty much trying to copy birds. It wasn’t really working out for them. Eventually they came to know what they didn’t know previously – How air flows over aircraft surfaces and all that funky fluid dynamics stuff.

They needed some kind of wind machine. These guys started mounting models of their flying machines on windswept ridges, and later developed makeshift aeronautical centrifuges or ‘whirling arms’. This was all happening back in the 1700s. And they proved successful by spawning unmanned gliders which were being ‘flown’ by Sir George Cayley as early as 1804.

It’s hard to make accurate measurements when your test subject is flying around in circles through it’s own wake of turbulant air. They needed something better. They needed constant, controllable air stream.

Credit seems to be given to Frank H Whenham of the Aeronautical Society of Great Britain for the first design and operation of a wind tunnel in 1871. We’re talking about horizontal wind tunnels for now, by the way. This tunnel was between 10 and 12ft long, 18 inches square and driven by a fan blower steam engine.

Over the years the wind tunnels grew in size and air speed all the way through to the second world war. As well as nature, war seems to be the major driving force and inspiration for new pioneering technologies. Now humanity wanted supersonic aircraft, missiles, faster cars, sturdier buildings. All being tested in wind tunnels.

Some of these tunnels were insane! The Brits had a supersonic tunnel by 1922 and Zee Germans had 3 different supersonic wind tunnels by the end of the war. One was capable of Mach 4.4. Some natural cave systems were excavated to become larger, then sealed to house wind tunnels.

During those years of developing horizontal wind tunnels, many lessons were learnt which apply to the vertical wind tunnels of today that we enjoy buzzing around in. Vanes were developed to smooth out the airflow, and in re-circulating designs to turn the air around corners. Look above and below next time you fly and you’ll see them. Circular test sections made to reduce the constriction of flow in corners that lead to turbulence. A fan blowing air into the test section creates lots of turbulence when compared to a fun sucking air through the test section. Reducing the diameter of airflow from the fans to the test subject can create faster wind speeds. Just like pinching a garden hose.

Going vertical

Trying to figure out when the first vertical wind tunnel was built wasn’t easy. Many websites claim the first was built here or there at some time. I think I may have narrowed it down to a NASA facility at Langley in the 1920s that was researching tailspin of aircraft, the most common danger of flying at that time. Although this one doesn’t quite count as the airflow was going down, not up. They built and started operating a 15ft vertical tunnel for the same purposes in 1935, where the model being tested was held in the airflow by a technician. Anything for some free tunnel time hey?

It wasn’t until 1941 when they built a 20ft tunnel with a top speed of 58mph to test the spin of (and I quote straight from an official NASA historical archive web page) ‘free-flying’ aircraft models. Boom Town! Free flying in the 1940s, Yeah! No need for the technician now.

 

Interestingly this design was a closed circuit, dual recirculating airflow. Just like the modern designs of today. With turning vanes, bell below the test section and everything. The ISG (Indoor Skydive Germany) website claims that their corporate ancestors were operating the first recirculating wind tunnels in the 30s. But I’m getting ahead of myself.

Although they were testing parachutes in vertical tunnels from 1946, the giant leap for skydivers happened in 1964 when Jack Tiffany told the guys running a vertical tunnel at the Wright-Patterson Air Force Base in Ohio to ‘Fire this puppy up, I think I can fly’. And there it was, the first human flight in a vertical wind tunnel. He had a little free fall time under his belt as he was a military test pilot, he had jumped out of some aircraft too. Apparently the US Army’s Golden Knights team used this same tunnel to train in before purpose built wind tunnels came on to the scene.

Time to get PAID

The first tunnel built specifically for human flying was designed and built by Jean St-Germain in 1978 in Montreal, Canada. Apparently he wanted his kids to experience flight! Lucky sods! He too built a recirculating model called the ‘Levitationarium’. It was built near Montreal Canada. He sold the franchising rights of this concept to Marvin Kratter and Les Thompson for $1.5 million dollars (no idea if this is US or CAN). Eventually this concept went on to become what Aerodium Technologies is today.

Jean’s design featured a DC-3 propeller below design with a recirculating airflow. A padded area surrounded the airflow for when you fell off the airflow. It cost $4/min to fly and $3 to hire the suit! It doesn’t seem, from what I can tell, he made much of an effort to turn his creation into a commercial success. Perhaps he was just after the rights and franchising pay out. So the first commercially orientated tunnel award goes to one of the guys he sold the franchising rights too.

Thompson went on to build one in Pigeon Forge, Tenessee and Kratter went on to build one in Vegas. They were in competition to open first. Thompson had some construction issues (what tunnel hasn’t!) a big issue was a fire breakout.

The Vegas tunnel opened it’s doors first in 1982, later that year the Pigeon Forge one opened. Both operating under the Flyaway franchise. And they’re still running as successful businesses! Although The Vegas one started operating under Vegas Indoor Skydiving when it was bought out in 2005. The limitations of it’s design soon became apparent. For a start, you could ‘fall off’ the airflow, and the flight chamber size was limited to the size of the prop below. Not to mention it was slow and bumpy. Over the years there were many different types of tunnels built. Some open flow and portable, used outdoors, some recirculating. Essentially they all had the same limitations.

It was in 1997 when Skyventure filed a patent for the first wall to wall open flow tunnel. A step forward in terms of air quality. Awesome! Multiple props with electric engines were placed above the airflow creating a smoother experience, but at the cost of being much louder due to it’s open airflow. A bell shape below the flight chamber allowed the airspeed to be increased.

And so in 1999 Skyventure Orlando was born. It was a 12ft Octagonal tunnel. It lacked climate control due to pulling air (and debris) from the outside environment. This put a limitation on where and when tunnels of this design could be operated. Skydivers seemed to be reluctant to embrace this new technology. For skydivers to really adopt this technology though, 2 things needed to be addressed, speed and size.

Aerokart built in 2002 in France was the first 14ft round design tunnel, closely followed by Skyventure Arizona, built on the Eloy DZ. Then Bodyflight Bedford, a 16ft tunnel in the UK, opened its doors in 2005. Remember Flyaway from the US? They had some involvement in this. Although Bedford was actually a converted tunnel, having previously been used for military research.

Training camps held by the top competing teams really started to pull in the skydivers. Even those who were initially too stubborn to accept that this was a game changer for the industry. Now the speed and size to fly 4 way flats and to free fly was available in the US, mainland Europe and the UK. And the level of skydiving went through the roof. More people with more skills meant better skydiving all round. Coaching styles became refined and diversified.

The Military were also keen on these tunnels, providing another market for tunnel operators to tap into. Some military organisations were ordering their very own private tunnels. And of course, the first timer market, just like tandems on a DZ, ensured a steady flow of revenue.

So where did the design go from here? We had the size, and the speed. Efficiency was the next step, and a reduction in the operation costs. In 2004 Skyventure filed a patent in the US for a multiple fan driven, recirculating wind tunnel. Same prop and electric engine style, but in a closed circuit. Where the fans would be mounted 90 degrees’ perpendicular to the direction of the flight chamber air flow.

Milton Keynes

This design would first be built in the UK and operated by Airkix Milton Keynes. The new design offered a high quality airflow, and a reduction in ambient noise (to stop those pesky residents getting in the way of your flying!). But the heat of the engines would cause the airflow to heat up to uncomfortable levels. Louvers were added to the return air towers. Essentially just giant vents that could be opened to different angles to let in fresh air from outside and cool the air within the tunnel. The problem here is that the more you open the louvers, the more turbulent the airflow became. ‘Sir, would you like it hot or bumpy?’ I genuinely used to ask VFS teams back in Manchester UK that question before they flew. At a high wind speed it was necessary to have the louvers open after only a few minutes to keep it at an acceptable temperature. At lower speeds, or in winter months the louvers would only have to be opened a small amount, or could even be left shut.

And so air conditioning was added. Those vanes used to turn the air 90 degrees into the basement, before being turned again up toward the flight chamber would have cold water pumped through them to keep the air cool. This general design and shape of tunnel would become the standard for most manufacturers. Fans in the top blowing air horizontally in both directions through cooled turning vanes in a closed circuit, recirculating system.

Skyventure took the lead with the design and build of these, especially in the US and branded most of their tunnels iFLY. But they aren’t the only players. ISG based out of Germany built their first tunnel of a similar design in 2008 in Bottrop, which became the epicenter of tunnel flying in Europe. Other manufacturers have popped up, Eydisa, Tunnel Technologies, Strojirna Litvinov who built skydive Arena, now Hurricane Factory Prague in 2011 and Aerodium, who built the Sirius tunnel in Finland in 2010, to name just a few.

Aerodium have been involved with some awesome projects and were used in the winter Olympics closing ceremonies back in 2006. A huge open flow design that had the performers hanging pretty damn high with boards on. Definitely wouldn’t want to mess that up! They were also involved in the latest Peter Pan stage show that was touring around a while ago. They were able to install a tunnel within 5 hours and have it incorporated into the stage design. They even provide the stunt double to do the flying scenes!

Size Matters

You can also find wind tunnels on cruise ships these days. It seems between all these manufacturers every major city of the globe will have a tunnel. There’s been talk of a 22ft tunnel in Dubai since the dawn of time. I heard years ago from a ‘reputable’ source that the parts were actually delivered to Jebel Ali, but then who hasn’t heard something from someone about that tunnel. Anyway, I’ve actually seen a picture of the inlet contractor sat on a site in the US. WOW it’s huge. Who knows if the thing will ever get put together.

But as the large populations of the world get saturated with multiple tunnels within one city, smaller tunnels offer reduced operating costs and the ability to capture and sustain smaller populations, in more prime locations.

Wow, that ended up being a long article. I hope you enjoyed the journey. I hope at least some of the facts were correct and you’ve at least had a go in a wind tunnel, and if not are planning on soon.

PS – every attempt was made to get the facts right. If you spot something that you think is not quite right, please contact your local police station…



By Mike Brigg
IBA Level 4 Instructor and Coach