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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.
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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FAA Introduces Voluntary Helo Bird Strike Safety Enhancements
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With autumn’s annual bird migrations underway, on October 3, the FAA issued a 4-page Special Airworthiness Information Bulletin 21-17 addressing Rotorcraft Bird Strike Protection and Mitigation. It also introduces the voluntary Rotorcraft Safety Promotion Concept (RSPC) that encourages the installation of safety enhancing designs, using specific safety equipment, and implementing operational procedures to mitigate the risks of helos having runs-ins with our feathered friends. Unlike fixed-wing aircraft that zip through densely populated avian territory, helos face increased bird strikes because they cruise in the lower reaches of the atmosphere, 3,500 feet and below, where 90% of snarge is created.
The RSPC webpage links to a list of bird-strike compliant helos. There are nine of them: the Airbus H225, MBB-BK 117 C2, D2, and D3; the Leonardo AB139, AW139, AW169, and AW189; and the Sikorsky S-92A.
It is followed by the Illustration of Voluntary Bird Strike Options that take normal category Part 27 helos toward the bird strike requirements of Part 29 transport category rotorcraft. These enhancements include bird resistant polycarbonate windshields, bird deterring lights, audio, and high visibility main rotor blades, and flight manual limits that limit the indicated airspeed to 80 knots.
Other operational risk mitigation options include flight planning and in-flight decisions that avoid bird-rich environments, mindful that these areas and the avion populations wax and wane with the season. If encountering birds in flight, slowing down, if practical, should be the pilot’s first reaction. More than three-quarters of all helo bird strikes happen when flying faster than 80 knots.
Gaining altitude, if possible, is another operational mitigation option. The SAIB says the likelihood of a bird strike decreases 32% for every 1,000 feet gained from 500 feet above the ground. And helo pilots should know and remember that birds fly at higher altitudes at night than they do during daylight.
Rotary wing aviators should also know and remember that their last line of bird strike defense is wearing a good helmet with the visor firmly in place. And if you fly in a birch world, you might consider the face guard many military helo crews use. Collecting snarge for a wildlife strike is never a good time, especially if you are scraping it from the facial folds of any member of the helo’s crew. — Scott Spangler, Editor
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X-65 Controls with the (Active) Flow
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The brothers Wright solved the conundrum of three-axis control for powered aircraft with the pitch, yaw, and roll control through the combined forces of an elevator, rudder, and wing warping. Glenn Curtiss effectively won his roll control legal battle with the brothers when he replaced a warping roll with a French “little wing, ” aka the aileron. (And then came roll-control spoilers, like those on the P-61 Black Widow.) One wonders what the Wrights (and Curtiss as well) would think of a powered flying machine that achieved three-axis control without any of these moving control surfaces? For DARPA, the Defense Advanced Research Projects Agency, Aurora Flight Sciences, a subsidiary of Boeing, is building the X-65 to realize the possibilities of Active Flow Control, part of DARPA’s CRANE, Control of Revolutionary Aircraft with Novel Effectors.
The X-65’s geometric joined-wing structure certainly is revolutionary, and I would have loved to have listened to the meeting that renamed aerodynamic flight controls, the rudder, elevators, and ailerons “effectors.” At least it makes sense. Without moving flight controls, active flows of air will effect changes in the unmanned X plane’s pitch, roll, and yaw. But wait! There’s more! The 7,000-pound research aircraft includes modular wing configurations so it can integrate and test other advanced CRANE technology. As DARPA put it: “Crane seeks to optimize the benefits of active flow control by maturing technologies and design tools, and incorporating them early in the design process. Active flow control could improve aircraft performance by removing jointed surfaces, which currently drive design configurations that increase weight and mechanical complexity. Demonstrating AFC for stability and control in-flight would help open the design trade space for future military and commercial applications.”
Time will tell whether the X-65 begins its flight testing, scheduled for 2025, but the project has completed four weeks of wind tunnel testing in Phase 1. Surely those tunnel tests included controlling the aircraft’s attitude with inhaling and exhaling air from the myriad vents on the wings that give Active Flow Control its name. With only a rudimentary comprehension of fluid dynamics, it seems that ACF will create a pitch, roll, and yaw effector by changing the shape of the boundary layers flowing over the geometrically joined wings. (Here is BAE’s YouTube take on the subject.) What I’m curious to learn is how effective this new active flow effector is compared to mechanical airflow deflectors, the traditional rudder, elevators, and ailerons (and spoilers, too!). The roll control legal patent battles between the Wrights and Curtiss aside, the aileron won because it was more immediately effective and it was easier to design and build, and it weighed less. In these regards, aviation’s practical demands remain unchanged. Scott Spangler, Editor
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Defining Aviation Learning Experiences
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To maintain my social skills, on Fridays I hike the Wiouwash Trail for 2.46 miles from the trailhead just east of Winneconne to the Bare Bones Brewery, which is trailside where the former interurban railbed enters Oshkosh, Wisconsin, on its northwest side. The Bone opens at noon, and I’m a member of its mug club. Exercise leading to (and from) good beer is guaranteed, and rare is the Friday that does not include a handful of people to talk with.
Conversations typically start with beer, and the craft breweries we’ve visited. This conversation is usually punctuated with our respective vocations and avocations. Talking with a couple somewhere in their 50s, the woman seemed especially interested after learning I was a pilot. She’d not met many, she said, and she peppered me with a curious collection of questions, such as who were the best pilots I’d ever flown with (a story for another day).
Flowering from the old saw that “There old pilots and bold pilots, but no old, bold pilot,” Most of them seemed to focus on things that define a pilot’s personality. Delving into this spectrum, which ranges from timid to foolhardy, I described myself as a pragmatic pilot who considered the relevant risks and played them out as possibilities influenced by the flight’s conditions. For more than 50 years now, mantra has been, “If in doubt, don’t.”
The couple asked if this guiding principle grew out of some inflight epiphany. In truth, this aviation moment that defined my flying life occurred in Alameda, California, during February 1973, three years before I started my flight training farther down the coast, in Long Beach, in 1976. Just before intermission during the film, Fiddler on the Roof, at the Alameda Theater, A Navy A-7 Corsair II dove almost straight into an apartment building a little more than a half-mile down Central Ave.
A photographer stationed at NAS Alameda, I spent a couple of weeks documenting this undesirable aviation outcome as the mishap investigators dug into the hole sifting the mess searching for evidence, for some clue to the mishap’s cause. They found the A-7’s engine about 20 feet under the basement garage floor. As far as I know, they never did find any of the pilot’s remains, but the 10 civilians who resided in the apartment building introduced me to the unmistakable, unforgettable aroma of seared human flesh.
The flight of two A-7s had left NAS Lemore on a night out and back training flight, and the flight’s leader said suddenly, his wingman was no longer off his wing. The rumor among the people sifting through the site was the pilot was sucking on a cigarette in-between whiffs from his oxygen mask, not an approved procedure at 37,000 feet. Nothing in the mishap investigation confirmed this rumor, but what stuck in my 18-year-old mind is that a momentary lapse in judgement, no matter what it might be, can turn any airplane into a dirty collection of metal scraps, slivers, and shards spread across a hangar floor. Aside from the compacted lump of the A-7’s Pratt&Whitney TF30-P-6 turbofan, few of them were larger than an index card.
Photographic work on subsequent fatal mishaps, the final approach meeting of the four turboprop P-3 sub hunter and a Boeing 707 lookalike, the Convair 990, at NAS Moffet Field on the other side of San Francisco Bay, and a Marine Reserve CH-53 that shed a main rotor blade up north in the Napa, fixed this reality in memory.
Asking for an example of how this guided my flying life, I recalled my invitation to introduce the “new” Cessna 172 to Flight Training’s readers when Cessna resumed production of its single-engine airplanes. It was an event attended by usual GA media outlets, and for some reason, I was selected first to fly. Searching for differences between the legacy Skyhawk and the new one, I started by following the handbook’s preflight inspection checklist. I stopped when I found good sized nick in a prop blade, and said I would not fly the airplane until the problem was properly addressed.
Seeing two quizzical looks above their beers, I explained that the nick might lead to the loss of part of the prop blade, and that the unbalanced blade might torque the engine off the airframe, which would destroy not only the center of gravity but also the airplane’s aerodynamics, and what was left would fall out of the sky. I like flying a lot, I said, but not enough to die for, especially when it would have been my fault for taking off with a known problem. “Ultimately, we all are responsible for the consequences of our decisions. — Scott Spangler, Editor