[HN Gopher] Active turbulence cancellation makes bumpy flights s... ___________________________________________________________________ Active turbulence cancellation makes bumpy flights smoother Author : bookofjoe Score : 172 points Date : 2023-12-12 15:19 UTC (7 hours ago) (HTM) web link (newatlas.com) (TXT) w3m dump (newatlas.com) | robertkoss wrote: | Sounds like a perfect setup to replicate the MCAS disaster. | https://en.wikipedia.org/wiki/Maneuvering_Characteristics_Au... | adgjlsfhk1 wrote: | the counterpoint is that this is a system that would only be | engaged at cruising altitudes, and which would probably be | manually turned on. the problem with mcas (aside from using a | single sensor for flight control) was that it had large effects | at low speed and problems near the ground don't give you time | to react | metabagel wrote: | You might not have time to react to a failure in this system, | given how quickly it alters the wing geometry. | rowanG077 wrote: | Is this now the default comment for any improvement in airline | technology? | tekla wrote: | Of course. It makes people feel better about a system they | know nothing about | duped wrote: | If you're advocating against the existence of feedback control | systems in aerospace, you're going to have a bad time. | l33tman wrote: | The issue with the MCAS-fiasco was that it (by design) was not | communicated to the pilots, so when it failed, they didn't know | immediately what to do. If they had known, they would have cut | out the trim motor and left it off and trimmed manually until | landing. In the accident flight, the crew repeatedly turned on | and off the electric trim and never figured out why it started | moving the trim every time they turned it on again (though, | yeah, it's an open question why they did this more than one | cycle....) | toast0 wrote: | The second accident flight shows knowledge of the system | wasn't enough. On that flight, they did turn off electric | trim, but weren't able to manually trim because the force | required to manually trim from the limit was too much. So | they turned electric trim back on, and shortly after they | stopped touching the electric trim inputs, MCAS resumed | setting the wrong trim. | | IMHO, the second accident had a better chance of survival, | but it wasn't enough. IIRC, the flight before the first | accident also had erroneous MCAS activation, and the flight | crew did turn off electric trim and did it manual, but it | wasn't treated as a must fix maintenance item, because MCAS | was hidden. | | There really should have been a separate shutoff for MCAS | apart from the electric trim switches. Limited activation | authority will hopefully be sufficient, but doesn't satisfy | my airchair aerospace engineering demands. | adgjlsfhk1 wrote: | counterpoint: the primary problem wasn't that mcas was hard | to turn off well. it was that it was a critical system | without any redundancy and therefore failed about 100x too | often. if mcas had been based off of 3 sensors like it | obviously needed to be it would have failed (and known that | it failed so it could turn itself off instead of pitching | down the plane) one a decade or so rather than a few times | a year. | londons_explore wrote: | > on long pole masts that placed them some 2.65 m (8.69 ft) | forward of the leading edges. At cruise speed, that's enough to | give the system a tenth of a second's worth of advance warning | before turbulence hits | | 2.65m */ 0.1 seconds = 60 mph. | | Airliners fly about 500 mph, so something about this math is far | off... | JoshTriplett wrote: | I would guess that it gives them enough advance notice to | _predict_ turbulence, based on the delta between forces on the | plane and forces on the poles. If there 's a sharp gradient in | forces, that gradient seems likely to increase, in a partially | predictable direction. | sgc wrote: | > The company says it'll have a system commercially available | for light aircraft in 2024. It's looking into a version for | eVTOL air taxis by 2026, and hoping to have a system relevant | to commercial airliners by 2030. Godspeed, team, the world's | airline passengers - not to mention cleaning crews - need you | to succeed. | | They are not targeting airliners for the current generation. | FirmwareBurner wrote: | _> They are not targeting airliners for the current | generation._ | | Like someone else said in the comments, (if true) this tech | seems to have already been used in military bombers for a | long time now, so to me it's weird it hasn't made it to | civilian aircrafts already from the civilian arms of military | contractors, and instead needs to be reinvented by a start- | up. | post_break wrote: | So it has to be 72 feet long by your math. | Ekaros wrote: | So start making holes in front of gates? That would be cool, | but maybe slightly impractical... | sp332 wrote: | The distance is measured from the leading edge of the wing. | The nose of an Airbus A330 is almost far enough away | already. | dylan604 wrote: | I hope it's retractable! | wongarsu wrote: | Maybe they meant the cruise speed of the test aircraft. Some | quick googling reveals it as a Colomban MC-30 Luciole [1], | which according to Wikipedia [2] has a cruise speed of 110 mph | and a maximum speed of 120 mph. Mounting the long instrument | arm to the tiny aircraft probably doesn't do it any favors | (seriously, the aircraft looks tiny next to a Cessna), so | cruising at 60mph sounds reasonable. | | [1] https://www.wildbergair.com/registrations/C/OE-CRG_1_01.htm | | [2] https://en.wikipedia.org/wiki/Colomban_MC-30_Luciole | mathgenius wrote: | Yeah I'm guessing these poles just get out in front of the wing | aerodynamics enough that they can sense whats going on with the | air so that air pockets/turbulence can be predicted. Either | that or we are missing a decimal place, maybe they mean 10 | milliseconds? | Tadpole9181 wrote: | The pole is on the nose, the time available to react would be | before reaching the leading edge of the wing. You'll need to | include the length of the front of the plane in question. At | least as I understand it. | woliveirajr wrote: | If it saves fuel, it'll be promptly adopted. Economy beats | confort every time. | mh- wrote: | Agree that's where the real commercial opportunity is. At | cruise, the autopilot is ~continuously applying changes to | control surfaces to maintain. | | If this can achieve more fuel-efficient adjustments, it'll be | extremely valuable. | bookofjoe wrote: | >Turbulence load prediction for manned and unmanned aircraft by | means of anticipating differential pressure measurements | | https://link.springer.com/article/10.1007/s13272-021-00512-y | | https://youtu.be/9qydsN_acDs?si=IaufsLiHjRe9Rr8X | | https://youtu.be/4UfmsqtTGa0?si=79DpjLcNQaaYMFIz | post_break wrote: | I wonder how this will effect the wear rate of moving parts on an | aircraft. Normally they are "fixed" right? And now they are going | to be moving constantly, during the entire flight. | stephen_g wrote: | The control surfaces? The pilot (or autopilot) is fairly | constantly making small corrections, so no, they're not | 'fixed', but it's true this is a much higher frequency movement | than normal control. | post_break wrote: | Yeah that's what I mean, they are moving, but nothing like | this where the movements will be measured in hertz. | globalise83 wrote: | The idea of looking ahead at turbulence and preparing for it is | good, but it has to be done with a technology that doesn't | require placing an enormous pole in the air, e.g. laser, radar, | etc. | vlovich123 wrote: | Yeah that's one problem for airliners. The others are getting | accurate predictions to happen far enough into the future that | the contraction would work and being able to generate high | levels of thrust into a specific direction at a moments notice | to counteract it. | sixothree wrote: | The front of the airplane is very far ahead of anything that | could possibly act on that information. Not nearly as much in | the case for this test plane. | ianlevesque wrote: | That's a really good point. Napkin math on an Airbus A321 | gives about 81 milliseconds of time to react, not far off | from the 1/10th of a second they cite for their prototype. | YetAnotherNick wrote: | Apart from the looks, is there any issue with the retractable | pole? We already have that in few aircraft for aerial | refueling. | londons_explore wrote: | The real savings come when this tech can be built into the | airframe. The airframe can only bend and flex a certain number of | times before it cracks and fails. | | Todays airframes have a lifespan measured in flight hours, and an | estimation is done as to how much turbulence will be hit per hour | of flight. At the lifespan limit, the plane is typically scrap. | | If this tech can reduce the flexing of the airframe during flight | by 80%, you can probably get 5x the flight hours from the | airframe before it becomes too weak to be safe (or more - half | the flexing typically more than doubles the lifespan) | | Alternatively, you can make the airframe thinner and lighter for | the same number of operating hours (and that's what is likely to | happen, since aircraft manufacturers don't want to put themselves | out of business). Thinner and lighter airframe saves fuel and | makes the aircraft cheaper. | gilbertbw wrote: | Pressurised airframes also have a pressurisation cycle limit | ericpauley wrote: | This. My understanding is that airliners basically _always_ | hit the pressurization cycle limit before anything else, so | wing turbulence cycles are not important. | vlovich123 wrote: | First, I don't understand what "build it into the airframe" | means. These are sensors that are used to predict turbulence | and then generate forces in opposition. Are you imagining small | sci-fi rapid thrusters throughout that can generate enough | thrust to counteract? | | Secondly, the turbulence prediction is extremely hard for an | airliner because it's traveling so fast - you'd need sensors | extended comically far forward and at that point you've got | real risk of them breaking off mid flight meaning you would | have to add significant amounts of weight to strengthen them | (assuming you could). You've also got the problem that you need | to retract this stuff on landing probably which adds more | weight and complexity. Adding even more problems, generating | sudden thrusts to counteract turbulence for a commercial | airliner seems really difficult since that's not how the | engines work (eg you probably can't generate a countervailing | force quickly enough). | | This is a neat concept but keep in mind this is a PoC on a very | lightweight craft going relatively slow. It's not clear how | big/fast an aircraft it can scale up to. An easier turbulence | reduction would be to mount the passenger area in something | that could actively mechanically stabilize like optical image | sensors. If you could decouple things so that the airframe | could be repaired/replaced cheaply independent you everything | else in the aircraft, that would be much more cost effective. | However I suspect the mechanical stabilization itself would add | a lot of weight/also need replacement and you wouldn't see fuel | savings I think, just a more comfortable ride. | lagrange77 wrote: | > Are you imagining small sci-fi rapid thrusters throughout | that can generate enough thrust to counteract? | | That's exactly, what i imagined, at least. | vlovich123 wrote: | Yeah unfortunately I don't think such tech exists and at | our current tech level I wouldn't imagine it would work and | could present real safety issues - you'd have fuel | pipelines running throughout the airframe which is likely a | significant amount of really serious fire risk, all of this | adds a significant amount of weight and maintenance cost, I | don't believe such adjustment thrusters exist but I could | be wrong, and I'm sure you would still get things wrong in | your prediction which means your thrusters would add wear | and tear on the airframe as well. | | This article is about a PoC where they put sensors extended | out of the airframe of a small slow moving aircraft and | demonstrated a 60% prediction accuracy for a 10% fuel | savings. It's unlikely this approach would scale up to an | airliner. The sensor problem might be but I have big | questions about the adjustments an airliner moving at | 600-900 mph can make to successfully counteract the | prediction. | swells34 wrote: | Doppler radar systems can detect airflow vectors in | arbitrarily large areas, so I imagine that we have the | tech for that portion, but I too am concerned about | trying to take something with that large a mass and | surface area and counteract turbulent forces with it. | That's also going to stress the airframe and avionics, | cause maintenance schedule changes, etc... | lagrange77 wrote: | Yeah, i was joking. Those thrusters would have to be | insanely powerful to accelerate such a big mass fast | enough to counteract the rapidly changing forces, caused | by turbulence. | capnrefsmmat wrote: | These problems are hard, but have already been solved. The | B-1 Lancer has active turbulence reduction built into the | airframe, via the small canards on its nose. | https://ntrs.nasa.gov/citations/19840005129 | | It's designed to work at Mach 0.85, and was meant to increase | the lifespan of the airframe during low-altitude penetration | flights where lots of turbulence could be expected. | mlyle wrote: | I think the real idea is to have surfaces or controls | distributed that could unload turbulence from individual | surfaces nearly instantly. | | This could be a few extra control surfaces, like a canard or | actuated slat, or it could be through something like Active | Flow Control -- | https://www.scientificamerican.com/article/the-next- | darpa-x-... -- where puffs of bleed air or electrostatics | adjusts airflow rapidly. | | I think systems-- like the B-1 Lancer highlighted by a | sibling comment-- show it's not completely impractical for | larger aircraft. | vlovich123 wrote: | Neat. The best way to learn something is to post something | wrong on a forum and wait for experts to correct you :). I | hadn't considered using puffs of air. I do still think | adapting it for a commercial airliner may be tricky but it | would be neat if one day a bunch of tech came together to | realize this. | ben_w wrote: | This may be equally scifi, but for sensors I'm imagining | small jet powered drones flying in formation a few hundred | metres ahead of the passenger plane. | | Given how slow and cautious the industry is (and for good | reason), even if someone has been working on this for a | decade already, I don't expect to see anything like that | before 2030. | ak217 wrote: | You don't need thrusters (which would be impractical). I | think you can get most of the benefit by sensing with tiny | canards in the front next to pitot tubes, and using electric | motors to adjust ailerons/flaperons/spoilerons multiple times | a second. | wrsh07 wrote: | I think route optimization that this will enable (not avoiding | certain turbulence) might be valuable (save fuel) - I'm very | excited about the potential implications per flight that this | might have | | The lighter airframe is really interesting, too, given the | ongoing cost savings | bobthepanda wrote: | At least with commercial aviation, unless you can't get ahold | of new planes they get replaced much earlier than that due to | wanting ever more efficient planes and more stringent noise | regulations. | | The old clunkers still around are mostly used in sanctioned | countries, or where a market failure has failed to provide a | decent equivalent (757/767) | hef19898 wrote: | Or they are used as a basis for freighter conversions. | | Not sure who still flys 757/767s so, at least for pax. Most | shoupd have been replaced by 777/787/A350s by now. | | Edit: Totally forgot about Delta. | sokoloff wrote: | Delta operates nearly 200 of the 75s & 76s. (They are the | largest operator of both, I'm pretty sure.) | awad wrote: | Delta and United both do, with Delta being the largest | operator of both types. | weaksauce wrote: | I flew on a 75 on delta the other day | BizarreByte wrote: | > or where a market failure has failed to provide a decent | equivalent | | A whole lot of weird, or just simply old planes still operate | in Canada for this reason. Until this year you could still | find 737-200 flights in the north. | cm2187 wrote: | I am not aware that the aiframe is the main reason why planes | are taken out of service. Fuel inefficiency is typically the | primary reason, plus increased maintenance cost. I can't | remember an accident of a major airliner as a result of the | airframe failing post the 1970s. | | Will be interesting to look at fatigue of the control surfaces | though, if they get used many times more per flight to adjust | for minor turbulences. | mlyle wrote: | > I am not aware that the aiframe is the main reason why | planes are taken out of service | | This is true--- these days. We've been tending to replace | planes before the airframe life limits are met. | | > I can't remember an accident of a major airliner as a | result of the airframe failing post the 1970s. | | Well, on the other hand, this is mostly true because airframe | life limits and expensive inspection programs that we | established after horrific accidents. | | And things like | https://en.wikipedia.org/wiki/Aloha_Airlines_Flight_243 | (1988). | | > Will be interesting to look at fatigue of the control | surfaces though, if they get used many times more per flight | to adjust for minor turbulences. | | Control surfaces are on bearings and have, in general, a lot | of excess strength to minimize internal deflection. Even if | there were a trade in wearing out control surfaces faster, | they are a more easily inspected and replaced part of the | airplane. | cm2187 wrote: | On the control surface, I mean less the surface itself than | the mechanism behind, i.e. the moving parts. | tiffanyh wrote: | > " Todays airframes have a lifespan measured in flight hours" | | Isn't the lifespan related to the number of cabin | pressurizations (not flight hours). | | Which is why long haul planes like 787 have longer lifespans | than a 737, because 737 are doing way more quick turn trips | (more pressurizations) than a long haul international flight | plane. | cabirum wrote: | Fighting turbulence must have an impact on fuel efficiency and | range. Additionally, pressure probes add weight and drag to the | aircraft. Overall, I think these kind of solutions look brittle | and error-prone. | asdfadsfgfdda wrote: | Pilots still fight turbulence today, usually by changing | altitude. If this system allows the plane to stay at optimal | (but turbulent) altitude, it could save fuel. | partdavid wrote: | And slowing down, which is usually the first measure and | reduces fuel efficiency from whatever's optimal there. | sixothree wrote: | Remote control airplanes have been using gyros to achieve the | same effect for some time now. It's a complete game changer and | changes the amount of enjoyment in a huge way. Instead of telling | the airplane what to do, you're more so telling the airplane | where to go. | | I'm not suggesting gyros are the correct way to do this. But I | can say the difference is night and day. | wussboy wrote: | I've occasionally thought about getting into RC planes, but the | piloting of them always seemed too hard. I'd love some links to | what you're talking about if you have some to recommend? | thsksbd wrote: | Rc planes are a few orders of magnitude smaller than commercial | aircraft. They have practically no flex and therefore fatigue. | | A gyro large enough to counter turbulence in an airliner would | be too heavy to fly and too the fuselage apart | snovv_crash wrote: | It isn't a gyroscope that physically resists rotation. It is | an active sensor that is used to control a PID loop to | control the actuators and reduce the disturbance. | | The technology in the linked article is even different, they | put a sensor far in front of the wing and preemptively | control the surfaces to counteract turbulence. | 83 wrote: | The gyros in RC are misleading. They are a sensor (gyrometer) | which isn't using mass to counter movement, the are merely | letting the plane know when it has shifted so it can move the | control surfaces accordingly. Gyros have mostly been replaced | by accelerometers at this point. | robertsconley wrote: | I thought Chris Kraft of NASA Apollo fame figured this out in the | fifties. | | From https://www.defensemedianetwork.com/stories/naca-the-jet- | age... | | In 1951, Kraft issued NACA Technical Note 2416 that proposed a | theoretical solution to the problem. Tests first on a modified | DC-3 and later on a C-45 validated the theory, and by 1955 the | system was perfected. | | Can be downloaded from here. | | https://digital.library.unt.edu/ark:/67531/metadc64927/m2/1/... | vlovich123 wrote: | I wonder if adding spinning wheels arranged in multiple axis | might be simpler ways to counteract the forces. Might be too hard | to do it in a safe/lightweight way and spin the wheels fast | enough to counteract the forces at play. | voldacar wrote: | I don't think a reaction wheel can do a ton in 100 ms. | vlovich123 wrote: | I was thinking more of a constantly spinning wheel and | conservation of angular momentum but maybe that doesn't help | if most of the motion of turbulence is translational? I'm | sure it's an impractical idea. | tullianus wrote: | You're describing a Control Moment Gyroscope (CMG), | famously used on the ISS. They have very high torque output | per unit power and mass/volume. They and reaction wheels | (fixed axis of rotation) are convenient for spacecraft | applications because they don't require an external medium | to push against. Aircraft are surrounded by air, so they | can use control surfaces instead. | L_226 wrote: | Hmm, I was thinking small flywheel / gyro units in the plane | fuselage itself similar to active roll damping in boats. I guess | active control surfaces make more sense for airplanes, without | knowing much about how turbulence affects felt vibration in the | fuselage. | lawrenceduk wrote: | I think this would effectively increase the stresses on the | airframe leading to greater metal fatigue which probably isn't | a good outcome | rowanG077 wrote: | Isn't the upto 10% fuel saving a much bigger deal? I mean | turbulence is just a minor inconvenience... | photochemsyn wrote: | The projected climate-driven increase in turbulence as a | marketing point is interesting, but there are caveats. Research | studies do point to turbulence increases in certain seasons and | latitudes: | | > "Climate modelling studies have indicated that the volume of | airspace containing moderate-or-greater clear-air turbulence on | transatlantic flight routes in winter will increase by 40%-170%, | relative to pre-industrial times, when the CO2 is doubled" | | https://link.springer.com/article/10.1007/s00376-017-6268-2 | | The CO2 doubling point is expected to arrive in ~60 years at | current fossil fuel combustion rates, but I'd expect by that time | a very large fraction of short-distance air travel will have | moved to (electrified) high-speed rail as it's far cheaper per | distance traveled. Also, as others note, this technology doesn't | seem applicable to trans-oceanic jet travel. | SomeCollegeBro wrote: | Whenever I'm flying on the B787, I prefer to sit right behind the | wing to watch the flaperons do their thing. I know it's a little | different than this, as it's more of a PID driven behavior rather | than an active predictive system. But regardless, it's quite | impressive to watch how they are constantly reacting despite the | plane seemingly not moving at all. They move very delicate and | precise, which must be difficult to do when travelling at 500mph. | FirmwareBurner wrote: | _> as it's more of a PID driven behavior rather than an active | predictive system_ | | Self tuning and active predictive PID controllers are also a | thing aided by the _' ye olde'_ faithful Kalman-Filter. At | least I remember reading about them in research papers. | | Now what exactly from those has materialized in commercial | applications, I have no idea, since it's not like they publish | such in depth info in the public facing spec sheet. | onlyrealcuzzo wrote: | Am I just flying weird routes, or are newer planes already super | smooth? | | I fly a ton and have only experienced bad turbulence a handful of | times in the last 5 years. | | It's actually astounding to me how little turbulence there seems | to be now. | | Maybe I'm just getting lucky? | wlesieutre wrote: | I wonder if that has more to do with the planes or with better | monitoring of atmospheric conditions for planes to dodge it | danans wrote: | In recent years I've heard pilots announce that they are re- | routing to avoid turbulence. I'm not sure what's new: the | announcement of this, or the ability to do so. | Scramblejams wrote: | Probably the former. It's long been customary for pilots to | broadcast turbulence over the radio so others can avoid it. | tynorf wrote: | Anecdotally, I fly round trip out of SEA ~3 times a year and | experience very bad turbulence on about half the flights. | Earlier this year it was bad enough to suspend drink service. | FanaHOVA wrote: | > Earlier this year it was bad enough to suspend drink | service. | | If drink service wasn't suspended on others, it wasn't very | bad turbulence. A rule of thumb is that if your seat belt | isn't hurting you, it's moderate or lower intensity. | Ocerge wrote: | I also fly commonly out of PDX and SEA. Generally anywhere | near mountains is going to be bumpy (Denver is a roller | coaster every single time). | adamredwoods wrote: | About a decade or two ago, turbulence seemed worse. My uncle | told of a time when he saw people hit the ceiling. I've | rarely had issues, although plenty of smaller pockets where | service does get suspended. I fly out of SEA, but in my | opinion, DEN is much bumpier because of the sheer winds from | the Rockies. | | My rule of thumb is if the drinks didn't fly into the air and | spill, then turbulence is minor. | | Also pilots largely avoid microbursts now: | | https://www.aerotime.aero/articles/microbursts-the-danger- | th... | drak0n1c wrote: | The 787 is far more comfortable than earlier aircraft in | regards to vibration, sound, air quality, and lighting - | there's a lot of internal upgrades. My mother who has had | severe headaches and sinus issues that are extremely sensitive | to altitude pressure when flying through the 1990s-2010s has | had no problems since flying on the 787. | thsksbd wrote: | This is terrible. Turbulence is the only time on a flight where | adults behave like adults [1]. Even their sphincters pucker | preventing them from degassing. | | "Nobody likes to fly through turbulence" | | Thats not true! There are dozens of us! (Actually, quite a big | more, I read a stat that we're about 5% of the fliers) | | [1] kids be kids, of course - as a kid I once ran up and down the | aisle during take off, so Im cool w/ kids. | furyofantares wrote: | My wife has a fear of flying but she likes some mild | turbulence. It helps her sense that flying is a physically | sensible thing, not some magical thing that shouldn't work. | thsksbd wrote: | Yea, but a quick prayer on take off/landing is not | unwarranted. Normalized by journey instead of mile, flying is | more dangerous than driving (according to Wikipedia anyway). | travisjungroth wrote: | That transport comparisons table puts it at 3x per trip. | This is like praying for your safety because you're going | into work and stopping for groceries on the way home. | | There have been _five_ fatalities of US airline passengers | in the last 10 years. That's billions of passengers. It's | incredibly safe. | BobaFloutist wrote: | That kind of makes sense, it's like how rock-climbing on a | rope is scary until you actually fall (or descend) and can | feel the tension of the rope actually supporting you. | | Even on a gut level, feeling the plane bounce against the | "road" gives you a confirmation that, yes, in fact, it is | bouncing against something (even if that something is just | air under the wings). | terryf wrote: | Yes! Glad to see someone else who also enjoys the turbulence! | | Flights are boring, the rocking around is fun! | chankstein38 wrote: | I agree, turbulence can be a fun experience! It gets old but | for a while the rush is great! | twism wrote: | was just wondering how pilots know ahead of time that there is | turbulence a minute or 2 out (obviously can't see it in the | distance) and it's the least technical way I thought possible | Tommstein wrote: | Am I the only one who actually likes airplane turbulence? | d1sxeyes wrote: | I mean, if it didn't then what would it be for? ___________________________________________________________________ (page generated 2023-12-12 23:00 UTC)