D. B. Cooper

Tickle The WireFBI Accepts New Evidence in Cold Case of ...
Sketches of “D. B. Cooper” with and without sunglasses, from 1972. Images: FBI, in the public domain.

Fifty years ago today, 1971-11-24, a man identified as D. B. Cooper highjacked a Boeing 727-100. Sometime that day he disappeared.

A middle-aged man stood at Northwest Orient Airlines’ flight counter at Portland International Airport, identified himself as Dan Cooper and purchased a one-way ticket in cash for a 30-minute trip north to Seattle. After boarding the aircraft he, in all likelihood, sat in seat 18C.

Flight 305, with 36 passengers and a crew of six, departed Portland on schedule at 14:50 PST. Shortly after takeoff, Cooper handed a note to flight attendant Florence Schaffner. Although she initially put it in her purse, Cooper asked her to read it. It mentioned a bomb and directed her to sit beside him, which she did. Cooper showed her the bomb, then demanded $200 000 in “negotiable American currency”, four parachutes (two primary and two reserve), and a fuel truck to stand by in Seattle to refuel the aircraft upon arrival. Schaffner conveyed Cooper’s instructions to the pilots in the cockpit, then returned.

William A. Scott (1920–2001), the captain, contacted Seattle–Tacoma Airport air traffic control, which informed local and federal authorities. The passengers were told that their arrival in Seattle would be delayed because of a minor mechanical difficulty. Northwest Orient’s president, Donald Nyrop, authorized payment of the ransom, and ordered all employees to cooperate fully with the hijacker’s demands. The aircraft circled Puget Sound for about two hours while the parachutes and ransom money were assembled, and emergency personnel mobilized.

FBI agents assembled the ransom money, 10 000 unmarked 20-dollar bills and microfilmed each of them. Cooper rejected military parachutes, and obtained civilian parachutes with manual ripcords.

At 17:39, the aircraft landed at Seattle-Tacoma Airport. The aircraft taxied to an isolated, but brightly lit section of the apron. All window shades in the cabin were closed. Northwest Orient’s Seattle operations manager, Al Lee, delivered a cash-filled knapsack and parachutes to flight attendant Tina Mucklow on the aft stairs. Once on board, Cooper allowed all passengers, Schaffner, and senior flight attendant Alice Hancock to leave the plane.

Cooper’s flight plan involved a southeast course toward Mexico City at the minimum airspeed possible without stalling the aircraft—approximately 100 knots = 185 km/h at a maximum 3 000 m = 10 000-foot altitude, with landing gear remaining in the takeoff/landing position, and wing flaps set at 15 degrees, and the cabin unpressurized. This meant that a second refuelling would be necessary. Cooper and the crew discussed options and agreed on Reno, Nevada, as the refuelling stop.

At about 19:40 the aircraft took off with only Cooper, Scott, Mucklow, first officer William J. Rataczak and flight engineer Harold E. Anderson on board. Two F-106 fighters shadowed the airliner, one above and one below, along with a Lockheed T-33 trainer, for part of the trip.

After takeoff, Cooper asked Mucklow to show him how to open the door to the aft staircase. He then ordered her to join the rest of the crew in the cockpit and remain there with the door closed. At about 20:00, a warning light indicated that the aft airstair had been lowered. At 20:13, the aircraft’s tail moved upward movement, requiring trim to level it. The plane landed at 22:15, at Reno Airport. Cooper was no longer on board.

From my perspective, the most interesting aspect of the case has to do with investigators describing the highjacker as D. B. Cooper, rather than the name he used on his ticket, Dan Cooper. Agents theorized that Cooper took his alias from a popular Belgian comics series of the 1970s featuring the fictional hero Dan Cooper, a Royal Canadian Air Force test pilot in a Belgian comic book/ graphic novel series, who participants in numerous heroic adventures, including parachuting. These comics were never translated into English, nor imported to the U.S. Thus, there are suggestions that Cooper was Canadian. In particular, the phrase “negotiable American currency”, aroused attention, because it would seldom be used by Americans.

Dan Cooper is a Royal Canadian Air Force test pilot appearing in Les Aventures de Dan Cooper, illustrated and written by
Albert Weinberg (1922 – 2011) and published in 41 albums from 1957 to 1992.

On 1980-02-10, Brian Ingram (ca. 1972 – ) uncovered $5 800 of the ransom from the Columbia River bank at Tina/ Tena Bar, about 14 km downstream from Vancouver, Washington. This is the only money from the highjacking that has ever been recovered.

There have been any number of suspects. Only one will be mentioned. In an article by Jake Rossen, writing in Mental Floss, in 2016, he suggests that D. B. Cooper may have been Barbara Dayton (1926 – 2002), who, before gender-reassignment surgery in 1969, was born Bobby. For the high-jacking she had disguised herself as a man. Pat and Ron Formans’ book, The Legend of D. B. Cooper (2008) gives a more detailed version.

There are any number of sources of information about D. B. Coooper, including a Wikipedia article that has provided much of the information here.

Honda e-Cub

A 1958 Honda Super Cub C100 featured a low-floor backbone step-through frame. The inexpensive but light weight plastic front fender and large leg shields, involved the first motorcycle use of plastic. The 17-inch wheels gave the vehicle a stability not found in scooters. The power train involved an automatic centrifugal clutch, 3-speed transmission, and an air-cooled 4-stroke 49 cc OHV engine. Top speed = 64 km/h. Wheelbase = 1 181 mm, Length = 1 781 mm, Width = 569 mm, Mass (wet) = 65.0 kg. Photo: Honda.

The Honda Cub is the best selling motor vehicle of all time, with over 100 million having been made in the years since 1958, when it was launched. Its origins are not in Japan, but in 1956 Europe when Honda co-founders Soichiro Honda (1906 – 1991) and Takeo Fujisawa (1910 – 1988) toured Germany and experienced the popularity of mopeds and other lightweight motorcycles.

Fujisawa was inspired, and wanted to produce a motorcycle for everyone: urban, rural or somewhere in between, living anywhere from a developed to an emerging economy. It had to be simple to survive in places without roads, advanced technology or access to reliable spare parts. It had to be quiet, reliable and easy to use. It also needed to have mass appeal, so that it could be produced on an enormous scale.

A scooter was considered but rejected: it was too complex for people in emerging economies, and, its wheels were too small for poorly maintained roads. Fujisawa specified ease of driving, by requiring that it could be driven with one hand while carrying a tray of soba noodles in the other. He is quoted as saying, “If you can design a small motorcycle, say 50 cc with a cover to hide the engine and hoses and wires inside, I can sell it. I don’t know how many soba noodle shops there are in Japan, but I bet you that every shop will want one for deliveries.”

Honda’s new vehicle was a 1958 Super Cub C100. It featured a low-floor backbone step-through pressed-steel frame. One important innovation, was their use of inexpensive but light weight plastic for the front fender and leg shields. This was the first motorcycle use of plastic. While the vehicle combined the characteristics of a scooter with the stability of a motorcycle. The 17-inch wheels, especially, gave the vehicle a stability not found in scooters. An automatic centrifugal clutch 3-speed transmission, and an air-cooled 4-stroke 49 cc (despite the model name) OHV engine, powered the vehicle. Top speed 65 km/h. Wheelbase 1 181 mm, Length 1 781 mm, Width 569 mm, Mass (wet) 65.0 kg.

The design was tested in advance of production, to eliminate any flaws. It would cost too much to fix problems after production started. It almost worked, except for an issue with the clutch, that required production and sales staff to visit each customer at home to fix each vehicle.

The early history of the Honda Cub will end here, with interested readers encouraged to either read the Wikipedia article or watch a more enjoyable but less extensive 8 minute video about it.

One challenge facing the world is reducing carbon emissions, and eliminating fossil fuels. This means transforming Honda Cubs into electric vehicles. So, even though Honda made an e-Cub prototype in 2019, they have never developed it into a production model. Why not? Is it because they are in too close a relationship with fossil fuel suppliers?

The facilities of Shanghai Customs Ltd, 57 Gao’an Road (near Hengshan Road), Xuhui District, Shanghai. Please note the Cub inside the facilities being modified, and the logo on the wall. Photo: Shanghai Customs.

Shanghai Customs Ltd was founded by Alexander Style. It sells e-Cub kits throughout the world for US$ 2 800. There are three kits available for the C50, C70 and C90 models. The non-battery kit lacks more than just a battery. However, it claims to come with everything needed except a battery, charger, frame, front forks and front suspension. One step up is the full kit. The name is a misnomer, since it too is another partial kit, which is like the above kit but with a battery and charger. The full kit with frame and forks provides everything needed for an e-Cub build. Kits are designed for amateur installation, described as plug and play, with colour coded and numbered wiring. Assembly takes from about 15 hours of work, using only hand tools. The finished e-Cub is powered by a removable 1.3 kWh Panasonic battery that provides energy to a 1 000 W, rear hub motor, that can be boosted to 3 000 W for short periods. Top speed for the vehicle is still 65 km/h, with a range of 50 km. Included in the kit are new LED lights, and fully digital instrumentation.

Fully Charged YouTube channel presented a nine minute video about the company, and its conversion kits.

Phil Tucker commented 2021-02-25 on the YouTube video: “(Don’t get me wrong as I’m a massive “all electric” fan….) but I’m not necessarily convinced that someone who maybe bought an old hand me down cub off an older brother or sibling for say, fifty dollars to use to go to work on is then going to decide to spend 2500 dollars to go electric! Also I think some of those brand new Chinese electric bikes are actually cheaper than that?”

This brought several interesting replies including one from Siclmn Cyclerider: “I spent $6,000 on a Stromer electric bicycle.” However, several others commented on the need for improved brakes, that appear to come with the kit.

To put the e-Cub in perspective, it should probably be compared with a minimalist electric car, such as a Citroën Ami, measuring 2 410 mm in length, 1 390 mm (excluding mirrors) in width and 1 520 mm in height, with a total weight of 485 kg. It has a 6 kW electric motor operating at 48 V, and powered by a 5.5 kWh lithium-ion battery. It is registered as a light quadricycle for two, allowing a top speed of 45 km/h, and a range of 75 km. When it was first released, it came with a purchase price of $6 600, a leasing fee of $22 per month, or an on-demand rental for around $0.29 per minute.

One major difference between the two vehicles is that while the Ami is a purchase of a product, the e-Cub is buying parts for a project. This involves people with two totally different mindsets. The e-Cub will only appeal to people who have the desire, time and opportunity to customize their own vehicle. The Ami will only appeal to people who want to buy happiness.

Note: There will be no attempt to enter fruitless discussions about other best selling vehicles. Contenders will not even be named. The point of this weblog post is to examine a potential waste recycling challenge, that allows people to continue to use a perfectly good vehicle, despite its currently inappropriate power source, by replacing it with a suitable electric power train. Mopeds may not be for everyone, but this writer is convinced that in Inderøy they are part of a Rite of Spring where, much like the return of the swallows to Mission San Juan Capistrano, thousands of mopeds appear on the roads, allowing their 16-year old drivers to self-certify themselves as adults, and slowing traffic to 40 km/h. More mature readers, no longer subject to the excesses of teenage hormones, may prefer to see new opportunities that emerge from using a mobility scooter which, fortunately, are already electrified.

To this day, a Honda 50, probably a 1966 model, owned at the time by Victoria Ayerbe, is the only motorcycle I have ever driven, and only once. I have no intention of repeating this experience with either a fossil fuelled or electrified motorcycle. Indeed, I have no intention of converting a Honda Cub to an e-Cub. However, I would like to encourage people in Inderøy involved in the electrification of old scooterettes, as they were often called, possibly at Reodor, Inderøy’s bicycle repair shop. There could be other two-wheeled vehicle models that, because of local popularity, are more deserving to be adapted to electric power. Making kits for these could be an enjoyable community project. If readers have particular candidates for conversions, please tell other readers about them by making appropriate comments.

Intel 4004

An Intel C4004 microprocessor with gray traces. (Photo: Thomas Nguyen)

Today (2021-11-15) is the 50th anniversary of the Intel 4004 microprocessor. This featured a 4-bit central processing unit (CPU). It was the first microprocessor to be sold as an electronic component. At the time of its development, Intel considered itself a memory chip manufacturer. At about the same time, three other CPU designs were being developed, but for specific projects. These were: Four-Phase Systems AL1, (1969); American Microsystems MP944 (1970); and Texas Instruments TMS-0100 (1971).

The Intel 4004 project began in 1969, when Japanese adding machine manufacturer Busicom, approached Intel to manufacture a chip it had designed. Intel was a start-up, so small that they didn’t have the staff to design the logic required. Thus, they came with a counter proposal, to build a general purpose computer-on-a-chip and to emulate the calculator architecture using a read-only memory (ROM) byte-code interpreter.

Frederico Faggin (1941 – ) was assigned responsibility for the project. He was able to design a customer-programmable microprocessor. The work included logic design, circuit design, chip layout, tester design and test program development. His initials F.F. were incorporated into the chip design. Assisting in the development process was Masotoshi Shima (1943 – ), a Busicom software and logic designer, but without any chip design experience. The chip was first used in the Busicom 141-PF adding machine.

Faggin is known for several microprocessor inventions. These include the buried contact, and the bootstrap load. He also created the basic methodology for random logic design using silicon gate technology. He was particularly vocal inside Intel in advocating the 4004 as a general purpose microprocessor, with a huge market potential. He subsequently led the design of the 4040, 8008 and 8080 processors.

Faggin was presented with the engineering prototype of their calculator with the first 4004. This was subsequently donated to the Computer History Museum.

Faggin and Ralph Ungermann (1942 – 2015) left Intel in 1974 to start Zilog. Intel’s reaction was to disown Faggin, and to rewrite company history. In particular, it credited more loyal, but less competent, employees, with the 4004 design.

Zahara: A tidbit

Singer and Poet Zahara in Nairobi, Kenya 2013-06-02 Photo: David Mugo/Reidarmax

Bulelwa Mkutukana, stage name Zahara = blooming flower. Born in East London, South Africa (1987-11-09 – ).

One Track: Loliwe The name refers to the train that brought workers back home after many years of working in Johannesburg, where they often had other families.

One Quotation: In an interview, Zahara described this first album as a metaphor. “It’s like … just pick yourself up. No matter who’s your father or who’s your mother … I believe that you’re not a mistake.”

One Comment: Zahara is a South African singer-songwriter and poet who sings in Xhosa and English. She started to sing at the age of six. Zahara released her debut album Loliwe in 2011 which sold over 100 000 copies in South Africa. Her debut single, Loliwe, featured here, currently has had over 1.8 million views on YouTube.


This weblog post is written to celebrate the upcoming 10th anniversary of Vortex Bladeless, as a concept, and the 81st anniversary of the collapse of the Tacoma Narrows Bridge on 1940-11-07. I have watched videos documenting the bridge collapse many times, and shown these to students in science classes over the years. Unfortunately, I lacked the insight of David Yáñez who was able to see the potential of oscillations in the generation of electricity.

David Yáñez and the Vortex Bladeless Tacoma at Avila, Spain in 2019. Photo: Vortex Bladeless.

Preliminary considerations

Living on a cliff-face, the residents at Cliff Cottage experience some wind, but less than many people might expect. The one-word reason is updraughts. That is, when the wind hits the cliff, it is deflected upwards, and then over the house. While the residents have considered installing horizontal bladed wind turbines at the cliff-face to provide electrical power, that take advantage of these updraughts, there is probably too little energy to make any investment economically worthwhile.

For example, a product was being offered on Kickstarter. On 2020-09-29, Nick Hodges, founder of Halcium, in Salt Lake City, UT, launched a funding round for (yet another device referred to as) a Powerpod, which was described as the “safest, most powerful wind turbine in the world”. He set US$ 200 000 as a minimum goal. When the fundraising period ended at the end of 2020-10, the goal was not met.

The product offered by Hodges, was not ideal for Cliff Cottage. The wind we are interested in using comes from one direction only, so being able to take advantage of wind coming from anywhere does not offer any advantages.

A major problem with the Kickstarter launch was an amateur approach to the electrical technology. After reading a description of the project, one was left with more questions than answers. Hodges apparently has a degree in small business management and an MBA with a finance emphasis from Arizona State University.

As another resident pointed out to me, entrepreneurship requires three competencies, finance (and related areas of business management), marketing and technical competence. From the material presented, it was obvious that Hodges had marketing competence, but lacked science and engineering skills.

For example, he claimed that Powerpods are “cheaper than solar panels and more efficient in places that get fewer than 300 days of sun a year.” When examining this statement, it is difficult to understand the specific apples and oranges being compared and contrasted. The number of square meters of solar panels is unspecified. Wind speed is an unknown factor, and there didn’t seem to be any documentation that related wind speed to power produced, only an attractive graph comparing power from a Powerpod with power from a normal wind turbine, whatever that is.

The number of days of sun is an unusual metric. Sunshine duration in hours per year is more common, something that can be determined using a World Meteorological Organization (WMO) standardized Campbell-Stokes recorder, which has been in common use since 1962. In 2003, the sunshine duration was finally defined as the period during which direct solar irradiance exceeds a threshold value of 120 W/m2.

There are claims that each 1kW in the Powerpod wind turbine creates up to three times more power than a regular, mounted turbine. The extra power comes from the blade system in the pod. While there is a graph showing this magic, there appear to be no supporting documents. There are no wind speed or power measurements, In fact, the graph incorrectly expresses power in volts, rather than correctly in watts.

The Powerpod system uses 12 Volt components. These are typically used on recreational vehicles to be compatible with vehicle electrical power systems. While they are used in residential systems, 48 V is quickly becoming the new standard. In part, this is because of the high amperage involved with 12 or 24 V. Transmitting 960 W of power with a 12 V system involves wiring capable of transmitting 80 A. With 48 V this is reduced to 20 A. Of course, if this power has to be transported any distance, it will have to be even thicker. Thick wiring is expensive and difficult to obtain.

Hodges goes on to compare wind and solar energy. In Norway it costs from NOK 30 000 to NOK 120 000 to have solar cell panels installed on an average single-family dwelling. This is typically financed by re-negotiating an existing mortgage. On average, the payback time for such an investment is about 17 years. The life-expectancy of the solar cell panels is from 25 to 50 years, and manufacturers offer a 25 year product guarantee on the solar cell panels, so that house owners do not face additional risks. Inverters may have a shorter life-span, and are not usually covered by the guarantee.

Unfortunately, the climatic situation in Norway means that solar panels can only produce substantial quantities of electricity during the summer. It is not that the equipment doesn’t work in the winter. Rather, the sun is close to the horizon, and not visible for many hours. On the date of publication, sunrise was at 08:16, sunset will be at 15:41. This gives 7h24m 43s of daylight. At the winter solstice (2021-12-21) daylight hours will be reduced to 4h17m21s. At the next summer solstice (2021-06-21) there will be 20h53m32s of daylight. Selling power usually requires one to participate in a spot-market, where prices are usually low in the summer, but high in the winter. Despite this, most people who install solar panels in one form or another want to connect to the mains in order to to sell excess electricity, or to access electricity when there is a production deficit. Batteries could be used, but new batteries are expensive. Some people will decide to buy discarded batteries from electric vehicles and store electricity with these. This is a more common model for cabin/ vacation cottage solar panels, less common for primary residences, because the cost is too large in relation to potential savings. Once again, people have risk aversion.

Another approach is to produce electricity in the summer and store it until it is needed in the winter. While the return-on-investment calculation for this looks good, mainly because of the high price for electricity in the winter, a large battery capacity is necessary.

Hodges’ main goal is admirable. He wants to reduce dependence on fossil fuel. He wanted to use the $200 000 funding to mass-produce Powerpods. The money sought would cover the cost of having the product tested, the raw materials for products being sold as part of the kickstarter project, as well as factory tooling.

After reading the project description, I was not totally convinced that Hodges had a viable product, or the necessary skills to make one. Hodges should partner with someone who has the necessary electrical engineering skills. This would allow for the development of the entire infrastructure needed for off-grid power production. These will have to meet agreed standards. At a minimum this consists of battery storage, a suitable inverter and a net metering system to allow produced energy to be used in the residence, or fed to the grid (especially at peak times). The equipment must be able to handle abnormal situations, such as power surges and power failures. The system should also prohibit sending power onto the grid, when it is down, as this could be potentially dangerous for crew members working to restore power.

There are also a number of legal issues that have to be negotiated, including energy purchase and sales agreements, and liability (including liability insurance). The specifics vary from jurisdiction to jurisdiction. Thus, it might be appropriate for Hodges to restrict his sales to Utah, and to find other people to cooperate with in other states, provinces and countries.

At Cliff Cottage we probably won’t participate in such a project. Instead, we will work slowly and methodically to find solutions that meet our specific energy needs. As a first step this will involve measuring wind speeds at the cliff face, to determine if wind energy is viable. If it is, then this process will slowly intensify as we select a more viable solution.

A More Viable Answer

The Vortex Bladeless turbine, popularly referred to as the Skybrator, has its origins in 2012 after David Yáñez watched a video of the Tacoma Narrow’s bridge oscillating in the wind. Since then, Vortex Bladeless, a Spanish tech startup, has been working to produce electricity from oscillations induced by wind.

Vortex Bladeless is a vibration resonant wind generator: It does not rotate, and is not a turbine, in contrast to the common horizontal-axis wind turbines (HAWT) and less common vertical axis wind turbines (VAWT) that work by rotation. Instead, it harnesses energy by allowing a fibreglass and carbon fibre reinforced polymer mast to oscillate in the wind, taking advantage of von Kármán vortices that form when a moving fluid (air) passes over a slender structure (the mast). At the bottom of the mast, a carbon fibre rod moves an alternator to generates electricity.

Wind turbines have issues, including maintenance costs, amortization rates, noise levels, bird deaths and other environmental impacts. Remote locations can have logistics challenges, while their visual and aural impact on a location is not always appreciated. The mass (and dimension) of vortex generators, indicate that they will use less raw materials in their construction compared to rotary wind turbines of the same power. They have a low centre of gravity that allows for a smaller foundation and less wake turbulence. Thus, they can produce more power (greater energy density) per unit of land area.

However, the market Vortex Bladeless envisions if for a small wind-turbine alternative for the end-consumer market and for low-power systems. These are markets that are served poorly (or not at all) by larger-scale wind turbine manufacturers.

  • Vortex Nano – 1 m high and 3 W nominal power output. For off-grid, low-power systems, especially with solar panels.
  • Vortex Tacoma – 2.75 m high and 100 W nominal power output. For small-scale residential/ rural autonomous operation, with solar panels.
  • Vortex Atlantis/Grand – 9–13 m high and around 1 kW nominal power output. For residential/ rural autonomous operation, with solar panels.

All of these are slender, vertical, cylindrical devices, composed of two main parts: a fixed base where the device is attached to an anchor, and a flexible mast which, acting as a cantilever, that interacts more freely with moving fluid (air) in an oscillating movement. The oscillator has no gears or moving parts in contact with each other, so there is no need for lubricants.

A linear alternator, with neodymium magnets and its stator is located inside the moving part of the device, converts mechanical to electrical (chemical) energy. During this process the alternator damps/ cushions the induced oscillation movements. These devices operate with minimal maintenance and operating costs.

Tacoma Narrows Bridge

With newspaper editor Leonard Coatsworth’s car still on the deck, vertical and torsional motion was recorded on the Tacoma Narrows Bridge, 1940-11-07. Oscillations eventually destroyed the bridge. Credit: Library of Congress Prints and Photographs Division.

There is 1.4 km of Puget Sound separating Tacoma from Gig Harbor. Yet, before the construction of the Tacoma Narrows Bridge, one had to drive 172 km between them. With the bridge in place, this was reduced to 13 km. The bridge also linked McChord Air Field near Tacoma with the Navy shipyard in Bremerton, both important elements of the American military’s infrastructure, and probably the most critical one that allowed the funding of the bridge. Washington States bridge engineer, Clark Eldridge, had proposed a conventional design for the state highway department and Toll Bridge Authority. However, the federal Public Works Administration, insisted that bridge engineer Leon Moisseiff, designer of the Manhattan and Golden Gate bridges, be hired as the lead consultant and designer, and to use deflection theory as the basis of the design, producing a lighter, narrower, more flexible and cheaper structure.

Construction of the bridge started in 1938 and took 19 months. When finished, the Tacoma Narrows Bridge had an 853-meter-long centre span, almost half its total length. It was the third longest suspension bridge in the world, behind the Golden Gate and George Washington bridges. It also had the smallest ever width-to-length ratio: 1 to 72. Even before the bridge was completed the bridge deck shook in a wave-like vertical motion. This earned the bridge its nickname, Galloping Gertie. The bridge opened on 1940-07-01.

On 1940-11-07/ November 7th, 1940/ 7 November 1940, south-westerly winds, with gusts up to 68 km/h began to buffet the bridge. The deck began its customary rippling, bouncing up and down with more than a meter of displacement from its normal position at times. Shortly after 10:00 traffic was halted because of bridge deck oscillations. Soon after the bridge’s vertical movement was supplemented by a twisting motion that whipped the deck up and down to either side of the centre of the roadway. The twisting grew increasingly severe, with one sidewalk up to 8.5 meters higher than the other.

At 11:02., a 180-meter portion of the centre span gave way, crashing into the water below. Additional sections followed. The last major section fell at 11:10. With most of the centre span gone, all that was left were dangling suspension cables, a hole between the two towers and remnants of sagging side spans at either end of the bridge.

Earth magazine has an article that provides further information about this bridge failure.