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Making the Brazilian ATR-72 Spin
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Note: This story was corrected on August 10th at 10:23 am, thanks to the help of a sharp-eyed reader.
Making an ATR-72 Spin
I wasn’t in Brazil on Friday afternoon, but I saw the post on Twitter or X (or whatever you call it) showing a Brazil ATR-72, Voepass Airlines flight 2283, rotating in a spin as it plunged to the ground near Sao Paulo from its 17,000-foot cruising altitude. All 61 people aboard perished in the ensuing crash and fire. A timeline from FlightRadar 24 indicates that the fall only lasted about a minute, so the aircraft was clearly out of control. Industry research shows Loss of Control in Flight (LOCI) continues to be responsible for more fatalities worldwide than any other kind of aircraft accident.
The big question is why the crew lost control of this airplane. The ADS-B data from FlightRadar 24 does offer a couple of possible clues. The ATR’s speed declined during the descent rather than increased, which means the aircraft’s wing was probably stalled. The ATR’s airfoil had exceeded its critical angle of attack and lacked sufficient lift to remain airborne. Add to this the rotation observed, and the only answer is a spin.
Can a Large Airplane Spin?
The simple answer is yes. If you induce rotation to almost any aircraft while the wing is stalled, it can spin, even an aircraft as large as the ATR-72. By the way, the largest of the ATR models, the 600, weighs nearly 51,000 pounds.
Of course, investigators will ask why the ATR’s wing was stalled. It could have been related to a failed engine or ice on the wings or tailplane. (more…)
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How the FAA Let Remote Tower Technology Slip Right Through Its Fingers
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In June 2023, the FAA published a 167-page document outlining the agency’s desire to replace dozens of 40-year-old airport control towers with new environmentally friendly brick-and-mortar structures. These towers are, of course, where hundreds of air traffic controllers ply their trade … ensuring the aircraft within their local airspace are safely separated from each other during landing and takeoff.
The FAA’s report was part of President Biden’s Infrastructure Investment and Jobs Act enacted on November 15, 2021. That bill set aside a whopping $25 billion spread across five years to cover the cost of replacing those aging towers. The agency said it considered a number of alternatives about how to spend that $5 billion each year, rather than on brick and mortar buildings.
One alternative addressed only briefly before rejecting it was a relatively new concept called a Remote Tower, originally created by Saab in Europe in partnership with the Virginia-based VSATSLab Inc. The European technology giant has been successfully running Remote Towers in place of the traditional buildings in Europe for almost 10 years. One of Saab’s more well-known Remote Tower sites is at London City Airport. London also plans to create a virtual backup ATC facility at London Heathrow, the busiest airport in Europe.
A remote tower and its associated technology replace the traditional 60-70 foot glass domed control tower building you might see at your local airport, but it doesn’t eliminate any human air traffic controllers or their roles in keeping aircraft separated.
Max Trescott photo Inside a Remote Tower Operation
In place of a normal control tower building, the airport erects a small steel tower or even an 8-inch diameter pole perhaps 20-40 feet high, similar to a radio or cell phone tower. Dozens of high-definition cameras are attached to the new Remote Tower’s structure, each aimed at an arrival or departure path, as well as various ramps around the airport.
Using HD cameras, controllers can zoom in on any given point within the camera’s range, say an aircraft on final approach. The only way to accomplish that in a control tower today is if the controller picks up a pair of binoculars. The HD cameras also offer infrared capabilities to allow for better-than-human visuals, especially during bad weather or at night.
The next step in constructing a remote tower is locating the control room where the video feeds will terminate. Instead of the round glass room perched atop a standard control tower, imagine a semi-circular room located at ground level. Inside that room, the walls are lined with 14, 55-inch high-definition video screens hung next to each other with the wider portion of the screen running top to bottom.
After connecting the video feeds, the compression technology manages to consolidate 360 degrees of viewing area into a 220-degree spread across the video screens. That creates essentially the same view of the entire airport that a controller would normally see out the windows of the tower cab without the need to move their head more than 220 degrees. Another Remote Tower benefit is that each aircraft within visual range can be tagged with that aircraft’s tail number, just as it might if the controller were looking at a radar screen. (more…)
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Crew Dragon Demo 2: A Short Course in 21st Century Spaceflight
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As it did when Alan Shepard kicked off the US Space program with his suborbital flight in 1961, I eagerly anticipated watching the program’s most recent chapter, the resumption of flights launched from American soil. Watching the preparations for the Demo 2 departure of Crew Dragon on Wednesday and on Saturday was much more than I expected, a short course in 21st century spaceflight.
Used to the military-toned phraseology employed during all of the NASA launches I’ve watched since Shepard went flying in 1961, it was clear this was a commercial operation because everyone on the NASA TV Launch America referred to everyone involved by their first names. Watching the launch on Saturday with my sister and brother-in-law, we considered (briefly) starting a drinking game where we had to take a sip every time someone said “Bob and Doug,” referring to the Crew Dragon crew of Bob Behnken and Doug Hurley. Thankfully we didn’t. If we had, the four of us would have been sleeping it off under the TV long before Bob and Doug closed their helmet visors and armed the launch escape system so they could start filling the Falcon 9 with densified LOX and RP1.
Like the NASA flights that preceded it, acronyms and multi-letter abbreviations liberally seasoned the comments and conversations of launch communications. What I did not expect, based on this past experience, is that the Launch America crew would translate and explain—in English—what they were talking about, hence the much appreciated short course in 21st century space flight.
Chances are you were, like me, one of the more than 10 million online viewers, so I won’t bore you with a geek-worthy catalog of new learning. But as a sample, the super turbo pumps feed the Falcon 9’s nine Merlin engines a mixture of densified liquid oxygen, which is colder than traditional LOX to provide more oxidizer in the same volume, and Rocket Propellant 1, which is a rocket-grade kerosene. To “complete the fire triangle,” the Falcon 9 adds TEA-TEB—a mixture of triethylaluminum and triethylborarne—a pyrophoritic compound that spontaneously combusts when exposed to oxygen (gaseous or liquid or densified liquid).
What they did not explain is why the crew kept their helmet visors open until arming the launch escape system. I remember from spaceflights previous when the crew had to prebreathe oxygen to purge their system of nitrogen before launch, to prevent any chance of bubbles of that gas in their bloodstreams should the spacecraft lose pressurization on its way to orbit. (Anyone have any ideas?) The boldly numbered members of the ground crew, on the other hand, seem an efficiently brilliant way to assigning and keeping track of their essential duties, responsibilities, and contribution to the flight.
If Launch America discussed the roots of the whimsical equipment names, I missed it, so I had to do some post flight research. SpaceX founder and chief engineer Elon Musk is a science fiction fan (like that was a surprise), so he named his reusable rocket after Hans Solo’s Millennium Falcon. Elon explained the capsule’s moniker in a Twitter response to a question about its name. The reusable capsule “was originally called Puff the Magic Dragon, as people said I was high if I thought it would work, so I named it after their insult.”
Expecting the Falcon’s Merlin engines to be named after King Arthur’s wizard, I discovered it was named after the bird, as were SpaceX’s other engines, Kestrel and Raptor. The drone ships that are the landing pads for the Falcon’s first stage were a bit more esoteric. Of Course I Still Love You and Just Read the Instructions are the sentient space ships in Ian M. Banks’s science fiction novel, The Player of the Games.
Taking notes during this enthralling short course was beyond difficult because I could not avert my eyes from the stunning HD video from almost every conceivable angle. Given technology today, I should not have been surprised, but my visual memory was stuck in the shuttle era. But some commercial aspects remain unchanged. On Saturday we turned into the Discovery Channel, and we greatly enjoyed the program that recounted the history of SpaceX and all of its successes and failures. But when the announcer announced the celebrities, including Katy Perry, who would be part of the launch coverage, we switched back to NASA TV and Launch America.
On Launch America the countdown conversation held us rapt, until one of the astronauts uttered a trite cliché, “Let’s light this candle.” Really? The Mylar Puff the Magic Dragon that floated up beside of the seats, described as the zero-g indicator, helped make up for the cliché, and trying to keep up with the speed and altitude readouts, in meters per second and kilometers, quickly buried the B-movie quote in 21st century appreciation and amazement. — Scott Spangler, Editor
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ADS-B Turbulence Reports: How Do They Work?
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The FAA recently posted a fascinating story on Medium, Taking the Turbulence Out of Flight that said ADS-B turbulence reports offer the possibility of more accurate reports on the bumps in the sky. What the story never fully explained is how the ADS-B system would generate the reports.
Like driving on a bumpy road, turbulence is what happens when atmospheric forces result in rapid changes in the vehicle’s horizontal and vertical planes. Its intensity depends on the size of the bump or pothole in the sky. And until this article, reporting such turbulence was a subjective evaluation made by the individual filing a pilot report.
Given a baseline understanding of the system, it is easy to intuit without explanation how the ADS-B turbulence position reports used its GPS WAAS engine. And its extended squitter bandwidth certainly had room for turbulence reports, but it never said how ADS-B would know it was in turbulence.
An FAA ADS-B FAQ page offered clues. ADS-B reports barometric pressure altitude as well as the airplane’s GPS-computed geometric altitude, “the height of the aircraft above the earth ellipsoid.” The two altitudes are not the same, the FAQ explained, “but having both allows for applications that require one or the other as an altitude source and provides a means of verifying correct pressure altitude reporting from the aircraft.”
The next paragraph provides another assumed part of the ADS-B turbulence report puzzle. “ADS-B does not report vertical or horizontal airspeed. Instead, ADS-B reports horizontal and vertical velocity relative to the earth. This velocity is useful for air traffic control functions and ADS-B applications. Airspeed can be provided by other aircraft sensors.” (And speaking of sensors, how will ADS-B separate atmospheric turbulence from the roiling vortices created by other aircraft?)
Might ADS-B turbulence reports be one of the system’s new applications? It seems that the necessary ingredients—position, altitude, and horizontal and vertical velocities—are available for a turbulence-sensing algorithm. But for the reports to have any value, the system must be communicating constantly with a ground station. With an update interval of once a second, that could be considered constant, even with uncompensated latency.
But this is merely an exercise in supposition, a guess of how ADS-B turbulence reports might work. If this guess is anywhere near to close, the best part of it, besides more granular turbulence reports, which any pilot would appreciate, is that that capability might become part of the ADS-B system with a software update, and not the installation of another piece of hardware.
Another benefit to pilots would be buried in the ADS-B turbulence report algorithm. It would consistently define different aircraft-appropriate levels or categories of turbulence with standardized variations or changes in altitudes and horizontal and vertical velocities. So before making a Pirep, pilot would not have to recall the Turbulence Reporting Criteria Table in the Aeronautical Information Manual. — Scott Spangler, Editor
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A Few Thoughts on Chicago’s Hometown Airline
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Like one of Chicago’s other major aerospace companies, Boeing, the town’s hometown airline has had more than its own share of problems, in addition to those gnawing customer service problems that plague the airline.
Certainly, many of the issues – like COVID-19 – facing United right now were not of the airline’s own making, but how the airline reacted certainly were.
I had a chance earlier this week to chat with Jenn White, from WBEZ’s midday Reset Show (@WBEZreset) about a host of issues related to United including how the COVID-19 virus chaos has and will affect United Airlines.WBEZ is Chicago’s NPR outlet.
Click below to listen to the show.
My apologies for the lousy audio quality on my side but they caught me on my cell.