[HN Gopher] Plans to shift aviation from magnetic navigation to ...
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Plans to shift aviation from magnetic navigation to true navigation
Author : tankenmate
Score : 250 points
Date : 2021-10-25 08:44 UTC (1 days ago)
(HTM) web link (www.flightglobal.com)
(TXT) w3m dump (www.flightglobal.com)
| defenestration wrote:
| The article mentions that the magnetic field of the earth is
| changing more rapidly. Why is that?
| BurningFrog wrote:
| No one knows. We just observe it happening.
| phkahler wrote:
| >> The article mentions that the magnetic field of the earth is
| changing more rapidly. Why is that?
|
| It is heading toward Russia. Putin is a super villain and he's
| stealing the north pole.
| tankenmate wrote:
| It goes through cycles naturally and from time to time the
| magnetic poles flip (it happens every few hundred thousand
| years). The magnetic field is largely created by the movement
| of molten iron and nickel in the earth's outer core. Wikipedia
| has a pretty good article on it.[0]
|
| [0] https://en.wikipedia.org/wiki/Earth's_magnetic_field
| jcims wrote:
| Whoa it looks like we're estimating it takes ~7000 years for
| it to complete the flip.
|
| https://www.nsf.gov/news/news_summ.jsp?cntn_id=100358
|
| Biology appears to survive it but I'm curious what happens to
| our digital ecosystem when we lose a portion of our
| protection against charged particles.
| tzs wrote:
| OT: looking at the maps on FlightAware, Flightradar24, and
| similar sites and seeing the vast number of planes crisscrossing
| the US at any one time I wonder if it would be possible to do a
| peer to peer navigation system?
|
| A plane at 30k feet should have line of sight to any other plane
| within about 200 miles, and even farther the higher up the other
| plane is. If the other plane is at 30k feet, it should be in line
| of sight at about 400 miles.
|
| Have a way for planes to exchange information with other planes
| that are in of sight about where they are heading and how
| confident they are that they are on the right heading.
|
| So let us say you've got a plane flying from Los Angeles to New
| York. You see what other planes you can see. That should include
| others that are going to New York but are ahead of yours. Find
| out from those who confident they are that they are on course,
| and use that to figure out a good course for you to follow and an
| estimate of how confident you are in that course.
|
| You in turn provide your course information to other planes
| heading to New York that are behind you.
|
| I think you could probably make a viable system with
| omnidirectional transmitters on planes for broadcasting course
| and confidence information, and directional receivers for
| receiving those broadcasts.
|
| I've sometimes wondered if some whales use a system like this. I
| remember reading once about some species of whale (I totally have
| forgotten which species and even where they lived) that had a
| long annual migration. Researchers had attached GPS trackers to
| several of the whales and recorded their routes.
|
| The researchers were surprised by how direct the routes were. The
| various ways they had hypothesized that the whales might navigate
| would have enough uncertainty that they expect the routes to have
| a lot more deviation from the direct route.
|
| The number of whales they attached trackers to was only a small
| fraction of the number of whales in the migration, and from what
| I read the migration doesn't start all at once. As the weather
| turns more and more whales start the migration.
|
| Suppose the whales navigate like I suggested above for planes.
| The whales that leave early or using the imprecise methods that
| the researchers hypothesized. They go in the right general
| direction using clues like sun position, but can get quite a ways
| to the side of the straight route, such as when they lose sight
| of the sun.
|
| The whales that leave a little latter would do the same thing.
| But the ones behind would also be able to hear the calls of the
| ones ahead. If they can tell what direction those are coming
| from, they can use that as a navigation input. If there are
| several ahead going toward the average position of the leaders
| should put the follows on a more direct route.
|
| Even if there is only one ahead that you are following, as long
| as that one is on average going in the right direction you should
| end up on a more direct route. That's because if the leader is
| drifting side to side and you are going toward them which causes
| you to also drift side to side your drifts should have a smaller
| amplitude.
|
| Those farther back following you will have even smaller drifts.
| The ones following your followers will be doing even better, and
| so on.
|
| If the whales the researchers attached trackers to where all far
| enough back in the migration, the above mechanism might explain
| what the researchers saw.
| literallyaduck wrote:
| I wonder if someone got intel that we are about to have a pole
| reversal or it might stop working completely.
| phkahler wrote:
| Awe man, they just moved the runways at my local airport a couple
| years ago to align with the newer magnetic north. It used to be
| 18/36 and 9/27. After the move it's 1/19 and 10/28.
| Grustaf wrote:
| What is the advantage though? True North is of course easier to
| understand and use when navigating manually, but what's the
| benefit in a commercial airliner?
| dan_hawkins wrote:
| First Air Flight 6560 crash [0]
|
| [0] https://en.wikipedia.org/wiki/First_Air_Flight_6560
| redis_mlc wrote:
| > What is the advantage though?
|
| Canada needs to move off magnetic north because the magnetic
| north pole is located in Canada, and it's changing rapidly.
|
| But that doesn't apply to the US. Sounds like a terrible idea
| for the training aircraft fleet to force them to buy INS
| systems when they all have magnetic compasses.
| KineticLensman wrote:
| TFA doesn't precisely enumerate them but two I saw were:
|
| * removes the ongoing process / cost of updating mag tracks as
| the Earth's magnetic field shifts
|
| * avoids errors that occur when the true/mag difference is
| correctly specified
| maxerickson wrote:
| It removes the need to maintain the lookup tables that are used
| to compute magnetic north from the true north determined by the
| navigation system.
|
| I don't know anything about them, but looking it up, apparently
| inertial navigation systems can determine true north by sensing
| the spin axis of the planet! So it isn't just a 'gps is easier'
| kind of thing.
| andylynch wrote:
| There are two main ones 1. modern navigation systems often work
| in true North already but have to map to magnetic for display &
| to match charts. 2. magnetic north moves! This greatly
| complicates how you deal with the first point.
|
| I don't envy the Canadian pilots they were talking about who
| tested some of this current stuff, and found their plane's idea
| of the runway direction way very different from where it lay.
| JumpCrisscross wrote:
| > _What is the advantage_
|
| From the article:
|
| "The migration of the geographic magnetic poles has accelerated
| in recent years, adding to the relentless task of updating
| systems and distributing the associated flight information.
|
| The AHRTAG points out that updating aircraft declination look-
| up tables is a specialist and expensive maintenance activity
| that has no effect on the way an aircraft derives its
| directional information. It merely ensures the result is
| displayed as a magnetic value that is normally less accurate
| than the originally determined True heading.
|
| And, if a future variation shift is sufficient to affect
| airport assets - like runway and taxiway signage and markings,
| plus instrument procedures, landing aids documentation, and FMS
| coding - at a major hub, the cost can top $20-30 million."
|
| https://www.flightglobal.com/flight-international/why-aviati...
| Grustaf wrote:
| That last paragraph makes sense, changing taxi markings etc
| is inherently expensive. The lookup tables part is harder to
| understand, but perhaps the airplane software is very badly
| written.
| rkangel wrote:
| It's a fundamental principle thing, that has some knock-on
| practical effects. Navigation is fundamentally getting from
| point A to point B. To do that, you steer a course between the
| two. Do you want to describe the angle of that course in
| reference to
|
| (a) A fixed line that never moves, such that the angle
| ('bearing') of that course is always the same
|
| (b) A line that moves around, seemingly randomly, particularly
| if you are near one of the poles of our planet
|
| Obviously from first principles, you'd pick the first. Due to
| historical navigation technology it was more convenient to use
| the second though. We had an instrument (magnetic compass) that
| would directly give us reference for (b), and so we described
| everything in those terms, and maintained tables of offsets so
| that we could calculate (a).
|
| Using (b) - magnetic North - causes some problems and because
| very few aircraft, and no commercial ones, rely on magnetic
| bearings as a primary source of navigation those problems are
| not worth it. One of the problems comes when you start
| labelling things that are fixed relative to (a), because
| they're attached to the ground but you label them using (b).
| After a few years the labelling is wrong and they need
| relabelling. This requires everything from pointing of radio
| beacons to repainting runways. It's all needed for effectively
| historical reasons.
|
| There are two Norths:
|
| The one that points in a constant direction on the Earth's
| surface. Getting from point A to point B on the Earth is
| fundamentally what navigation is and so having a fixed
| reference for that is good (modulo continental drift).
|
| The direction that a magnetic compass points. This is at an
| arbitrary _and changing_ offset to any direction on the Earth
| 's surface.
|
| Why
| Grustaf wrote:
| I'm aware of all this, it's the same in sailing and it's a
| mess. But since aircraft are already set up to use magnetic
| north, and are basically flying computers, it shouldn't
| matter what crazy navigation scheme they are using.
|
| But a sibling comment already pointed out, what you also
| mention, that it also affects physical markings etc, and that
| makes much more sense.
| ryandrake wrote:
| > (a) A fixed line that never moves, such that the angle
| ('bearing') of that course is always the same
|
| Just to nit-pick your otherwise great comment: This may be
| true for short, general aviation navigation, but long haul
| airliners typically navigate via great circle routes, which
| do change true course throughout the route.
| rkangel wrote:
| Yes, there's lots of reasons why you don't fly in a
| straight line from airfield A to airfield B. Whether that's
| a great circle or just a multi segment line to avoid an
| airspace restriction I suppose what I was really talking
| about was "your bearing at any given moment on your
| course".
| flavius29663 wrote:
| Now I get it, using the magnetic north is akin to the
| daylight saving time kerfuffle, on steroids - you basically
| have to account for variations even during the same flight if
| you fly near the poles.
| Grustaf wrote:
| The magnetic north is even affected by local phenomena, at
| least when you're on the ground, so it's worse than that.
| pridkett wrote:
| This is really fascinating, but probably something that is
| needed. If nothing else it means airports will stop needing to
| re-paint their runways periodically. Tampa had to repaint runways
| in 2011, Stansted had to do it in 2009 and thinks they'll need to
| do it again in 2055 [0].
|
| Of course, to get there we'll have to repaint a lot of runways
| and replace a lot of signage for runways that currently
| correspond to magnetic north.
|
| [0]: https://phys.org/news/2011-01-tampa-airport-runways-
| renumber...
| closewith wrote:
| > If nothing else it means airports will stop needing to re-
| paint their runways periodically.
|
| Airports have to repaint their runways far more frequently than
| the multi-decade timespan it takes to shift 10 degrees due to
| wear-and-tear, weather, resurfacing, etc.
| jgtrosh wrote:
| I'd wager that maintenance repaint (in place) is less costly
| than repainting at a different location, which requires
| additional expertise
| p_l wrote:
| you do not repaint in different place, you change the
| numbers at most, because unless you rebuild the runway
| you're not going to change its axis to which paint marks
| locations are referenced.
| d1str0 wrote:
| You can't just arbitrarily change numbers though. Lots of
| documentation needs to be updated with a number change.
| p_l wrote:
| True. But I'd say not as much as people might think,
| assuming (oops) that people check NOTAMs
| UseStrict wrote:
| It changes regularly, and by significant amounts. Magnetic
| north can drift 45km to 55km per year, and in the article it
| was talking about a major airport in Canada, the Calgary
| airport, where even slightly out of date maps were off by as
| much as 7deg. Source:
| https://www.ncei.noaa.gov/news/tracking-changes-earth-
| magnet...
|
| Will it require repainting? Probably not, but the further
| north you go, the more noticeable even minor drift or
| fluctuations will be.
| captainredbeard wrote:
| Just more money for the avionics shops
| kumarharsh wrote:
| Kinda funny that the aviation industry cannot implement the more
| accurate inertial navigation systems (INS) right now because:
|
| "The biggest single problem in trying to implement this change
| worldwide would be inertia"
|
| XD
| dogma1138 wrote:
| Outside of military uses when GNSS can be jammed INS is
| pointless when GNSS is available.
|
| INS that is accurate is very expensive to build and maintain.
| INS that isn't reliant on external inputs including from a
| magnetic compass for calibration is even more so.
| rjsw wrote:
| Operation Black Buck [1] was done using INS [2] as GNSS was
| not yet available.
|
| [1] https://en.wikipedia.org/wiki/Operation_Black_Buck [2]
| https://en.wikipedia.org/wiki/Delco_Carousel
| ghaff wrote:
| And even top-grade military INS does external checkpoints
| where possible (although it's probably pretty accurate in any
| case).
| mr_overalls wrote:
| Not saying you're wrong, but. . . who actually knows what
| actual top-grade INS is doing these days? Those kinds of
| capabilities would probably be Top Secret or SCI.
| cm2187 wrote:
| The SR71 was using stars to navigate!
| HPsquared wrote:
| That worked in the SR71's case because, flying high as it
| did, the sky above is black and you can see stars during
| the day.
| PaulHoule wrote:
| They were teaching cadets at the Air Force Academy
| celestial navigation in the 1980s.
|
| This guy
|
| https://en.wikipedia.org/wiki/Guy_Murchie
|
| taught celestial navigation to navigators flying across the
| Atlantic in WWII.
| ampdepolymerase wrote:
| You need clear view of the sky and big lenses (you can
| always use more compact metamaterial lenses and infrared
| imaging for cloudy days but they are as expensive if not
| more than INS). Star charts also drift over the years and
| you will have the same problem as magnetic true north where
| the database needs to be updated regularly. Fine for
| airliners, not so great for skyhawks.
| adolph wrote:
| _An automatic celestial navigation system for navigating
| both night and day by observation of K-band or H-band
| infrared light from multiple stars._
|
| https://patents.google.com/patent/US7349803B2/en
|
| _In this celestial map, the bodies of the solar system
| are placed so exactly that those versed in astronomy
| could calculate the precession (progressively earlier
| occurrence) of the Pole Star for approximately the next
| 14,000 years. Conversely, future generations could look
| upon this monument and determine, if no other means were
| available, the exact date on which Hoover Dam was
| dedicated._
|
| https://www.usbr.gov/lc/hooverdam/history/essays/artwork.
| htm...
| JKCalhoun wrote:
| I'm imagining a navigation system by trying to pattern-
| match the earth terrain with a downward-facing camera
| from the plane.
|
| A suitably large database of satellite photos covering
| various conditions, day, night might work for all cases
| but cloudy (when the plane is above/in the clouds).
| maxden wrote:
| They've used that landing on Mars as well, Terrain
| Relative Navigation.
| fbanon wrote:
| Already exists: https://en.wikipedia.org/wiki/TERCOM
| Since the 1950s!
| JKCalhoun wrote:
| Oh yeah, contour-matching. I remember this being touted
| with regard to U.S. cruise missiles in the 80's, 90's.
|
| Guess radar + countour is more reliable than camera +
| imagery.
|
| (I'll crawl back to the 1800's now.)
| [deleted]
| cm2187 wrote:
| Yeah I guess that wouldn't work during takeoff and
| landing. But for the most common airliners (a320 to a380
| and boeing equivalent): are there clouds above their
| cruising altitude? By day I presume you could use the
| sun.
| p_l wrote:
| Some early jetliners had special cupola for star
| navigation, but it soon fell out of use because NDB, VOR,
| DME and other radio systems were easier and better.
| adolph wrote:
| Exactly what I was thinking about:
|
| https://www.thedrive.com/the-war-
| zone/17207/sr-71s-r2-d2-cou...
|
| https://www.thedrive.com/the-war-zone/41287/r2-d2-spotted-
| on...
| roenxi wrote:
| If something unforeseen happens an the GNSS systems go down
| for whatever reason we might be set up for a terrifying few
| months of disruption. Coronavirus was bad enough, and most of
| the disruptions were voluntary to some extent.
| scoopertrooper wrote:
| If all the various GNSS constellations went down
| simultaneously we'd definitely be in the shit. Not just
| because we lost GNSS, but we'd also probably be fighting a
| war or Kessler syndrome would be in effect. Either way,
| losing GNSS would be just one of many problems!
| p_l wrote:
| We still have VOR network and other legacy systems. Some
| are no longer integrated into parts of the avionics but you
| can still plan routes and use them to fly. Plus Primary
| Surveillance Radar will see you anyway.
| bronco21016 wrote:
| I wonder how long it will take to get the VOR network
| serviceable. Many of them are no longer maintained.
| p_l wrote:
| some dropped off maintenance, but not all. NDB is pretty
| much dead outside of few rare spots, though, and not
| everywhere had DME even at best time. But nav points used
| with GPS still often are based on VOR locations.
| p_l wrote:
| INS that doesn't drift pretty much immediately is expensive and
| needs periodic fixups, and the moment GPS became available it
| pretty much dropped off anyones purchase plans (as it can't be
| used as backup for GPS unlike VOR/DME)
| lazide wrote:
| I think they may have been joking since INS - is inertial
| navigation.
| uuidgen wrote:
| While INS is not simple, it's also not that difficult to
| implement. As even the cheapest drones that can hover show
| new MEMS sensors are accurate enough to work with a proper
| filtering.
|
| I did some prototype INS system as my master's thesis 10
| years ago, the code was quick and dirty and even then the
| accuracy was like 30 meters after an hour of walking around
| with the device.
| p_l wrote:
| Thing is, it has to work over atlantic/pacific/cross north
| pole routes, etc. We're talking multiple hours and long
| distance, possibly with a lot of turbulence (even for GA,
| which actually gets less steady flight so...).
|
| And then it needs to provide guarantees about said
| navigation, guarantees that those drones _do not need_.
| FabHK wrote:
| That is surprising, you must have had an extremely accurate
| accelerometer and gyro, or employed tricks [1]. There are
| two problems with determining position from acceleration
| measurements:
|
| 1. You're integrating twice (acceleration to obtain
| velocity, then velocity to obtain position). So if you have
| any noise or error, you're integrating that, and integrate
| that again. Hello, parabola.
|
| 2. Gravity. It's strong. So you have to subtract it (as it
| induces an apparent acceleration upwards).
|
| If the difference between actual down and where your model
| thinks is down is just a fraction of a degree, you'll be
| totally off within minutes.
|
| See eg here:
| https://www.youtube.com/watch?v=C7JQ7Rpwn2k&t=1401s
|
| Or here: https://www.cl.cam.ac.uk//techreports/UCAM-CL-
| TR-696.pdf
|
| > As a concrete example consider a tilt error of just 0.05
| [degrees]. This error will cause a component of the
| acceleration due to gravity with magnitude 0.0086 m/s2 to
| be projected onto the horizontal axes. This residual bias
| causes an error in the horizontal position which grows
| quadratically to 7.7 m after only 30 seconds [and thus to
| 770 m after 5 minutes, unless I'm mistaken, and 110 km
| after an hour]
|
| Or here: https://liqul.github.io/blog/assets/rotation.pdf
| (search for "Accuracy of Velocity and Position Estimates").
|
| [1] such as assuming that your foot has velocity zero while
| on the ground, which does not hold when you're in an
| elevator, for example, and which you can't use in a drone
| without some serious sensor fusion.
| sheepybloke wrote:
| This also depends on the plane. For larger commercial
| applications, you need to have INS. You want to use a
| combination of sources ideally, since INS is accurate for a
| shorter period and GNSS/GPS for longer periods(often GPS/GNSS
| is only updated every second). Plus a lot of newer units have
| a much smaller drift. This FOG has a drift of 0.1 deg per
| hour, which is quite good
| (https://www.advancednavigation.com/solutions/spatial-fog-
| dua...).
| throw0101a wrote:
| There are a lot of old Cessna-type planes out there in the US
| (and to a certain extent Canada) that act as the backbone of the
| pilot training pipeline: what will it take to update all of
| those? (And a whole bunch are owned 'for fun'.)
|
| I guess after people had to pay to meet the FAA's ADS-B mandate,
| this is another equipment update that will need to dealt with.
| sleepysysadmin wrote:
| >I guess after people had to pay to meet the FAA's ADS-B
| mandate, this is another equipment update that will need to
| dealt with.
|
| Have us Canucks even done ADS-B? The USA is way ahead of us on
| that one.
| _n_b_ wrote:
| "Meanwhile, the ADS-B mandate in Canada has been under an
| indefinite suspension since November 2019. It was originally
| slated to begin in February 2021 but was placed on hold in
| response to stakeholder feedback."
|
| https://www.ainonline.com/aviation-news/business-
| aviation/20...
| sleepysysadmin wrote:
| Thanks, couldn't find anything. I knew that happened years
| ago and didn't hear much.
| throw0101a wrote:
| IIRC a major sticking point was "antenna diversity": in
| addition to having something point down, Nav Canada wanted
| antennas pointing up for space-based ADS-B (NavCanada was
| an initial investor in Aireon).
|
| But the extra antenna is still a bit pricey, but given
| Canada's vastness, satellites were the only way to get good
| overage outside of major urban areas.
|
| NavCanada/Aireon would also be using 1090ES and not the UAT
| that the US allows for lower-flying GA planes as well.
|
| However, if you're near the US border, your transponder can
| (IIRC) broadcast that you have an UAT receiver on-board
| (even if you have an 1090 transmitter), and the FAA's gear
| may send out UAT data (e.g., weather, UAT planes).
|
| * https://skiesmag.com/features/diversity-matters-canadas-
| perf...
| ChicagoBoy11 wrote:
| A lot of those are also being retrofitted with newer gauges...
| Garmin has a whole series of products that is basically "take
| your six-pack and make it digital!" sort of stuff. I think your
| ADS-B analogy is spot on -- I'd imagine this go somewhere in
| the same way as that.
| bencoder wrote:
| The direction indicator is gyro based rather than magnetic so
| for most GA it would probably be enough to just learn the
| offset for the area you are flying and add that when you
| set/check the DI.
|
| For VFR flying it hardly matters anyway
| lxgr wrote:
| The direction indicator is not a gyrocompass, though - it
| will eventually drift unless it's periodically adjusted.
| bencoder wrote:
| Sure but in small GA planes you're not likely to be
| travelling so far that the magnetic declination is
| significantly different so just keep it in mind each time
| you reset the DI. Or if you are travelling long distance
| you could make a note of it along your planned route, or
| your GPS app could let you know.
|
| My point was that this shouldn't require any instrument
| upgrades to the GA fleet
| perilunar wrote:
| > this is another equipment update that will need to dealt
| with.
|
| Even in planes with only 'steam' gauges the changes are minor
| -- you won't need any new equipment.
|
| Currently: direction indicator is set to magnetic. When
| planning a flight you take true headings from charts and have
| to convert them all to magnetic. You then fly magnetic
| headings.
|
| After the changeover: direction indicator is set to true. No
| need to convert headings when planning a flight. You fly true
| headings, and the only conversion you need to make is when
| setting the DI from the compass.
|
| (If you don't have a DI you can still pre-convert all your
| headings to magnetic and fly those. You'll need to mentally
| convert runways headings etc. though.)
| barbazoo wrote:
| It drifts considerably over time so you'd have to set it to
| true periodically which on the ground during start up is fine
| but not in the air, having to determine magnetic variation at
| your current location.
| jcrawfordor wrote:
| magnetic variation doesn't change all that quickly at 100
| knots, and charts provide the variation. I don't really see
| it being a much bigger workload, and I imagine that if this
| change does occur chart plotters like Foreflight will start
| displaying the current variation very prominently for
| convenience (it's already pretty easy to pull up). I can
| also imagine people starting to sell retrofit bug rings for
| heading indicators that let you set the variation in for
| convenient setting.
|
| But in general most pilots of slow aircraft probably
| already know the approx. variation around their area by
| memory, most pilots of fast aircraft will have instruments
| that do it for them.
| NikolaNovak wrote:
| I don't have a pilot license, but from what I recall of limited
| training, don't you do most of your training based on Heading
| Indicator? You adjust it at beginning, which can easily be
| switched to whatever heading/offset of the runway is (true or
| magnetic); then reset it to compass as needed on level flight -
| which is rare during short training flights, and could be
| adjusted to appropriate offset.
|
| So I don't think _training_ itself will be a problem.
|
| Once you have actual flights in those aircraft though, I
| imagine it'll be a bigger kerfuffle for pilots.
| p_l wrote:
| a lot of smaller planes have only magnetic compass, no gyro-
| based heading indicator
| RNCTX wrote:
| Not true, even the lowly rental C172 with 3 shades of paint
| and carpet at any raggedy flight school will have a gyro
| based indicator.
|
| Magnetic course calculation is only taught at the initial
| license level and to instructors. Anyone else is flying by
| GPS or radio-based nav.
| NovemberWhiskey wrote:
| OK but the vacuum gyro in said raggedy-ass 172 needs
| setting against something as part of the checklist (and
| quite possibly in flight), which today is the magnetic
| compass.
| RNCTX wrote:
| Yeah, but this is really only applicable to VFR-only
| airplanes (mostly trainers). I doubt there are many
| people really traveling in airplanes without any sort of
| precision nav equipment.
|
| Practically, it doesn't matter which direction the gyro
| points as long as you are receiving a VOR signal or GPS
| signal on a VFR flight.
|
| And yeah, a _lot_ in flight. By definition those gyros
| are gonna be old, and they cost more to overhaul than
| they 're worth so people who are too cheap to go buy an
| electronic replacement replace used for used off of eBay
| or the local radio shop's junk shelf. They're not gonna
| be reliable, at all.
|
| But, for VFR purposes it doesn't matter and for IFR
| purposes you shouldn't be flying such an airplane with
| such equipment IFR anyway, so...
| FabHK wrote:
| Right. And then you'd have to apply a correction (which
| might change a tiny bit over several hundreds of miles
| flown, or over the years).
|
| But no need to change anything in the aircraft, as far as
| I can tell. Just planning and procedures.
| p_l wrote:
| Great, C172 counts as "more expensive" option here,
| training will go on raggedy ass C150 recovered from a
| crash, be happy if you get turn indicator.
| 535188B17C93743 wrote:
| They just said "a lot of". There are a lot of pre-1950
| planes out there flying without a 6 pack to be heard of.
| Good ole stick and rudder flying. No gyro instruments
| needed... just altimeter, airspeed, tach, fuel, and the
| horizon.
| adolph wrote:
| NBC: Harrison Ford Lands On Taxiway
|
| https://www.avweb.com/news/nbc-harrison-ford-lands-on-
| taxiwa...
| repiret wrote:
| While it's legal under part 91 to have only a magnetic
| compass, a vaccine powered gyro DI (or solid state
| equivalent) can be found in the majority of the GA fleet.
| The aircraft without a DI are typically ones with bush
| flying or acrobatic missions, where pilots don't spend much
| time looking at their instruments for navigation anyway.
| jsight wrote:
| It took me a while to realize that you meant vacuum
| powered. :)
| AdamN wrote:
| Q up there made a Freudian slip :-)
| AdrianB1 wrote:
| In my country (Romania) all of the small planes I flied
| (about a dozen) had just 2 or 3 magnetic compasses. These
| planes are allowed to fly only on visual orientation
| conditions (weird local laws), so navigation is not a
| real concern.
| p_l wrote:
| I think any requirement to have gyroscope-based
| instruments only comes in with IFR (at the very least you
| need turn indicator due to lack of horizon reference).
|
| It's not any weird local laws, it's common aviation laws
| :) though navigation is a big thing even in VFR ;)
| endymi0n wrote:
| ...a Raspberry PI, some COTS sensors, a USB power bank and an
| old iPad:
|
| http://stratux.me/
|
| (or: less than the cost of a usual 100h overhaul ;-)
|
| source: PPL applicant and fellow hacker
| mysterydip wrote:
| Doesn't that need to be FAA certified to be relied upon in an
| aircraft? That's generally what adds all the expense between
| "homebrew" and "commercial", isn't it?
| rlpb wrote:
| It's classed as "pilot carry-on" equipment and doesn't need
| to be certified. Only stuff permanently installed gets that
| treatment.
|
| Just as I don't have to have my pen and pad (or indeed my
| iPad) certified either :)
| Scoundreller wrote:
| I wonder how many aviate with a big-ass "portable"
| lithium ion battery to power it all instead of paying
| $100 for a flight-certified cigarette lighter receptacle:
|
| https://www.aircraftspruce.com/catalog/elpages/cigrecept.
| php
| btgeekboy wrote:
| I have a pair of 13aH Anker batteries I use, rather than
| dealing with the lighter plug. The electrical isolation
| is a feature.
| repiret wrote:
| It needs to be certified to be permanently installed in a
| non-experimental aircraft, or to be relied upon for IFR
| use, but for VFR use powered from a cigarette lighter and
| suction cuped to the window, you can do whatever you want.
| ubermonkey wrote:
| uh, no.
|
| Homebrew hacking is one thing on your dining room table, or
| for basic home automation, or whatever.
|
| Homebrew hacking in an airplane sounds like an awful idea.
| rrss wrote:
| why?
| adgjlsfhk1 wrote:
| homebrew solutions generally don't have the excessive
| redundancy that keeps planes from crashing.
| samus wrote:
| Not all systems are safety-critical though. Most hackers
| probably wouldn't mess with control surfaces, engine
| control, and instruments, and would err on the side of
| safety too. But planes don't immediately drop from the
| sky just because their radio is off or their navigation
| systems have a hickup.
| bityard wrote:
| You mainly see "excessive redundancy" in larger cargo,
| passenger, and military aircraft. Small general aviation
| airplanes don't have as many redundant systems as you'd
| think. There is neither the space or weight budget. For
| safety, they mainly rely on well engineered systems,
| frequent inspections, required maintenance and updates,
| and failsafe design, such as the ability to pilot the
| plane as a glider if the engine cuts out.
| bityard wrote:
| Uh, yes.
|
| There is a whole aviation subculture of experimental
| aircraft designers, builders, and hobbyist engineers. There
| are limitations of course (mostly to do with passenger
| safety) but the FAA grants a surprising amount of leeway
| once an aircraft is granted the "experimental" label.
| zajio1am wrote:
| Homebrew hacking of ultralight airplanes (including
| homebuilt planes) is common here in Czechia, legislation is
| much less restrictive than for homebrew hacking of cars.
| krisoft wrote:
| > Homebrew hacking in an airplane sounds like an awful
| idea.
|
| These are not for commercial aviation. The only area where
| homebrew can "fly" is experimental airplanes. And in that
| application it kinda makes sense. Many of those airplanes
| were made in someones garage themselves, so why stop there
| and why not make the instruments yourself too?
| AdrianB1 wrote:
| As a GA pilot, one of the complications of the navigation exams
| for small planes was navigation and calculation of magnetic
| versus true and the entire range of derivations. It was mostly
| useless because of the local legislation demand to fly only in
| visual conditions (IFR not allowed for small planes), but it made
| the exams unnecessarily harder. The ever worse part was the
| demand to be able to calculate a flight path to something like
| New York, where Earth curvature matters, for planes that cannot
| fly more than 1000km at low altitude and speed, so they are never
| allowed to fly over the ocean or on distances big enough to have
| a significant difference between a straight line on the map and
| the shortest route. I am happy to see at least one of these going
| away, even in 9 years.
| aj7 wrote:
| Bad idea. Wouldn't want to be flying over water in Asia when
| China decides to invade Taiwan with just GPS.
| MayeulC wrote:
| I have some training as a VFR pilot (for ultralight aircraft). I
| was under the impression that true north was always used
| everywhere (maps mainly), and adjusted with the local (and
| current) magnetic deviation when preparing the flight plan, to be
| able to take accurate bearings.
|
| Using magnetic north in maps and databases seems... misguided.
| Not updating instruments with the latest value too, although it
| must be a lot more complex to do so over long flights, with non-
| negligible deviation changes.
|
| Don't lose your bearings! I can imagine it's easy to rely too
| much on instruments when they're available.
| ls65536 wrote:
| Related to this topic, here's an interesting NOAA site with more
| details about Earth's magnetic declination and containing lots of
| data about how it changes spatially and temporally:
| https://ngdc.noaa.gov/geomag/declination.shtml
|
| They even have detailed data for predictions about how it is
| likely to change in the coming years (presently up until the year
| 2025).
| AshamedCaptain wrote:
| > They even have detailed data for predictions about how it is
| likely to change in the coming years (presently up until the
| year 2025).
|
| They have been publishing the models in 5-year packages for as
| long as I can remember (e.g. previous one was 2015-2020 model,
| and so forth). I still have 30 year old devices/PDAs/GPSs that
| see firmware updates just for the magnetic declination models.
|
| Curious how they do it these days, since all these devices with
| a compass need these up-to-date models. Likely they just phone
| home every time. :(
| ls65536 wrote:
| It probably depends on the specific application, but I would
| imagine the models/data that various devices in the field are
| using are probably updated as part of some periodic
| maintenance schedule. They don't change significantly enough
| or quickly enough to demand online updates that frequently,
| but I suppose every device manufacturer/maintainer has their
| own way of doing it for whatever reasons they might have.
|
| In my own work, I've downloaded the dataset from NOAA and
| their tools to parse and work with this data to generate my
| own global 1-degree by 1-degree by 1-year "grid" for magnetic
| declination [0], along with some code [1] to read this data
| and be able to give you an estimated value for magnetic
| declination for any position on the globe for any time
| instant between 2020 and 2025. Before 2025, I will probably
| need to download the new data, run the tools again, and
| update my own dataset (to include values for 2025-2030 or
| whatever the case may be), but this will definitely be a
| manual process.
|
| [0] https://github.com/ls4096/sailnavsim-
| core/blob/master/compas...
|
| [1] https://github.com/ls4096/libproteus/blob/v0.6.2/include/
| pro...
| temptemptemp111 wrote:
| Wouldn't want more people realizing the nature of the earth!
| maxcan wrote:
| Its kind of funny. In our initial training the FAA requires that
| instructors really drill it into our heads when we using magnetic
| vs true numbers then as soon as you pass your first check ride
| you basically never think about it again.
|
| I've been flying since 2013 with almost 500 hours at this point.
| I could make some educated guesses about where we use true vs
| magnetic, but aside from runway designations couldn't tell you
| much for certain.
|
| Its never come up in my flying.
| ah88 wrote:
| CFI here. It's not a big deal in most of the country but the
| Pacific Northwest does have variation of about 20 degrees. It
| can make a difference when calculating takeoff and landing data
| as winds are true but runways are magnetic.
| bronco21016 wrote:
| I think it's important to point out the nuance. Observational
| winds (eg METAR) are recorded in true. Reported winds (ATIS,
| ASOS, AWOS) are given in magnetic. [1]
|
| The adage goes "If you read it, it's true. If you heard it,
| it's magnetic."
|
| [1]
| https://www.faa.gov/documentLibrary/media/Order/7900_5D.pdf
| Chapter 7.4
| barbazoo wrote:
| What if you read the ATIS though? /s
| maxcan wrote:
| one of my favorite apocryphal exchanges:
|
| airplane inbound to land: "KXYZ tower, N12345 at 3000'
| tower: "N12345, KXYZ tower, confirm you have Romeo"
| airplane: "KXYZ tower, N12345 has Romeo" tower: "N12345,
| fine, but bravo is current, recommend you recheck atis"
| bronco21016 wrote:
| Oh you must have meant KDTW.
| sheepybloke wrote:
| When I was working on FMS, that's what we used to test our
| true north to mag conversions. Just fly across the Pacific
| Northwest and toggle the switch to verify that everything
| looks good.
| euroderf wrote:
| GPS goes down or is spoofed or blocked, a solar storm hits,
| software bugs & crashes, how many RISKS to the public ?
| wwn_se wrote:
| GPS is not involved in this change really. Solar storms affect
| the magnetic field of earth to. Magnetic north is just a sensor
| going through software like everything else. Less risk... not
| more.
| rob74 wrote:
| Er... I get it that it's about changing the "reference
| system" and not primarily about GPS. But the difference
| between "magnetic North" and "true North" depends on your
| position, and how are you going to get your position if not
| using GPS?
| jcrawfordor wrote:
| Using a wide variety of "traditional" techniques that range
| from dead reckoning (or "pilotage" which is dead reckoning
| corrected by landmarks) to politely asking a controller if
| they have you on radar. Airplanes operated under
| challenging conditions without falling out of the sky for a
| long time before GPS became a ubiquitous flight instrument
| (pretty recently, really).
| chrisseaton wrote:
| > GPS is not involved in this change really.
|
| How do you determine true north without a GPS system?
| lisper wrote:
| How do you determine true north _with_ a GPS system? GPS
| only gives you your position, not your orientation.
| chrisseaton wrote:
| > How do you determine true north with a GPS system?
| def true_bearing(magnetic_bearing, location)
| magnetic_bearing + gma(location) end
|
| And that's the point - your true bearing is a function of
| your location.
| lisper wrote:
| Ah. Right. Duh. (I must be having an even worse day than
| I thought.)
| lxgr wrote:
| Wouldn't it be possible to broadcast local magnetic
| declination over ATIS or other automated broadcast systems?
|
| As far as I know (and according to the article), modern
| navigation systems contain databases of the local magnetic
| declination anyway; instead of updating maps and
| navigational databases, we could just update these
| declination database instead every once in a while if I
| understand it correctly.
| chrisseaton wrote:
| How do you apply these things without knowing where you
| are?
|
| True/magnetic deviation is localised. You need to know
| where you are to know what the localised value is.
| lxgr wrote:
| Wouldn't a very rough location suffice, i.e. something
| that could be either manually set (for general aviation
| and shorter distances), derived from a VOR station
| identifier or similar, or just estimated via dead
| reckoning/an INS?
|
| In other words, if you don't even have a rough idea of
| where you are, what good will a magnetic heading do?
| chrisseaton wrote:
| Rough yeah - but I think it does change by integer
| degrees from actual map sheet to map sheet, so you could
| probably drift a couple of degrees without knowing it
| within an hour or so of flying.
| Ekaros wrote:
| Magnetic declination and deviation are already trained concepts
| in nautical navigation. Don't see why they couldn't be used
| with aeroplanes as well. Bit more calculating, but not really
| very big deal.
| NovemberWhiskey wrote:
| They already are; every private pilot is trained on magnetic
| variation and deviation as well as magnetic dip (turning) and
| acceleration errors.
| JumpCrisscross wrote:
| > _GPS goes down or is spoofed or blocked, a solar storm hits,
| software bugs & crashes, how many RISKS to the public_
|
| None. The second sentence in the article:
|
| "...navigation by global navigation satellite systems (GNSS) -
| backed up by ring laser gyro-stabilised INS/attitude and
| heading reference system platforms, radio beacons and air
| traffic control surveillance using multiple technologies."
|
| https://www.flightglobal.com/flight-international/why-aviati...
| ah88 wrote:
| The FAA is also maintaining a core set of ground navigational
| based stations (VOR) in case of GPS failures. It's the COBOL of
| the aviation industry :) There are occasionally parts of the
| sky that have GPS outages due to military activity anyway.
| dosman33 wrote:
| With how much the military has been practicing for situations
| where GNSS will be jammed in the past few years it seems...
| overly optimistic to coerce the entire industry to ditch the
| magnetic compass at this point.
|
| https://www.thedrive.com/the-war-zone/17987/usaf-is-jamming-...
|
| https://www.thedrive.com/the-war-zone/15194/russia-jammed-ph...
|
| FAA issued NOTAMs (Notices To Airmen) reveal a lot of deliberate
| GNSS jamming across the US around military bases, it's not just
| limited to the Nelis area:
| https://notaminfo.com/explain?id=1630592
|
| Also Russia enjoys just messing with GPS to annoy NATO exercises,
| so you never know when you might fly through an area of active
| GNSS denial: https://www.ofcom.org.uk/spectrum/information/gps-
| jamming-ex...
| peytoncasper wrote:
| I mean the article mentions that GA (General Aviation) has
| pretty much adopted GNSS at this point. And its likely that
| airliners can afford the cost of INS as a backup system along
| with the other backup mechanisms mentioned in the article.
|
| "Today, however, navigation by global navigation satellite
| systems (GNSS) - backed up by ring laser gyro-stabilised
| INS/attitude and heading reference system platforms, radio
| beacons and air traffic control surveillance using multiple
| technologies - means that aviation has no real need to use a
| magnetic reference."
|
| Lastly, I would imagine the inclusion of AHRS systems as backup
| still supports a mission critical VFR/IFR type of flight.
|
| In the event of GPS jamming, I doubt non-critical operations
| would operate given the heightened risks.
| [deleted]
| alfalfasprout wrote:
| I doubt we'll lose the magnetic compass tbh... but the idea is
| that we would use true north for everything. If you needed to
| use your magnetic compass because your GPS is INOP you'd just
| apply the appropriate declination + compass card correction
| then.
|
| In practice, most GA pilots have at least a VFR GPS on the
| plane and the majority fly with iPads w/ Foreflight now. You
| put one of those window-mounted ADS-B receivers and you even
| get traffic alerts and <1m accuracy. For IFR, pretty much all
| approaches are VNAV and use GPS now anyways.
| BoiledCabbage wrote:
| And how much do they change while flying from LA to NYC? Or
| on medium distance trips? Or out over one of the owns.
|
| Having to recalibrate continuously during a flight seems very
| counterproductive. Especially if you drift off course and so
| can't recalibrate accurately.
| jcrawfordor wrote:
| The HI needs to be adjusted continuously during flight
| (every 15 minutes is a rule of thumb but more if
| maneuvering) anyway. Having to factor in the variation when
| doing so doesn't seem like a significant increase in
| workload, and the industry will quickly start producing
| aids to doing so.
| [deleted]
| AdamN wrote:
| I think they're saying in the extreme event of needing to
| do declination manually you are safe and can navigate and
| land the plane, not that it would be a normal occurrence.
| The default would be using true North and all the modern
| navigation equipment.
| sokoloff wrote:
| On an LAX to JFK trip, magnetic variation changes from 12E
| to 13W, or about 1o per 100 miles. In a case of falling
| back to magnetic navigation from a GPS/INS failure, this
| would represent an insignificant increase in workload (on
| that trip; around the magnetic poles, it's higher workload,
| but it's already higher workload to do magnetic navigation
| very near the poles).
| [deleted]
| willis936 wrote:
| Magnetic variation can be pretty dramatic, especially at
| latitudes past the tropics. It's reasonable to use a
| combination of magnetic compass with dead reckoning.
| lazide wrote:
| And ever changing - drift is quite visible over a decade or
| so, and using old maps can cause real problems if you're only
| using magnetic when you get even as far north as Seattle.
| ls65536 wrote:
| And this is why when doing any sort of navigation activity
| you should always check the publish dates on your
| maps/charts and act accordingly!
| BayAreaEscapee wrote:
| My uncle was a private pilot. He used to take me flying
| from time to time.
|
| I remember him saying that it's legal to fly _without_ a
| map, but it 's not legal to fly with an outdated map. If
| you have a map, it must be up-to-date.
| mordechai9000 wrote:
| Don't some maps actually show the current rate of change?
| I seem to remember some of the USGS maps I purchased
| showed this.
| ls65536 wrote:
| You're right that they do often show the local magnetic
| declination's rate of change (around the time of
| publishing), but even that goes out of date eventually.
| For relatively short periods (maybe on the order of years
| or possibly even a decade or two, depending on the
| particular location), applying this rate of change may
| give a good approximation of the present day's magnetic
| declination value, but beyond that the errors can become
| unacceptably large.
| [deleted]
| shadowgovt wrote:
| As context: aviators have at least five references that (in
| reasonably-populated and infrastructure-supported areas) they
| can usually use:
|
| * GNSS
|
| * compass
|
| * VOR (ground radio beacons emitting a patterned signal to
| point to where the beacon is)
|
| * Visual landmarks
|
| * Asking air traffic control where radar spots them to be
|
| The meat of this planned change, IIUC, is that maps that have
| to change to account for shifts in magnetic north over time
| will now be static, and instead additional offsets to correct
| the true north / magnetic north error will need to be factored
| in when an aviator uses one of their five common navigational
| aids. This seems like a reasonable place to put the costs.
| Scoundreller wrote:
| Not just maps, but also runway number repainting and all
| associated documentation.
| vwcx wrote:
| Flying as a GA pilot in Montana, I can't rely on VOR for two
| reasons: signal interference from terrain and the fact that
| the FAA is actively decommissioning the VOR system. I can't
| rely on ATC radar because of terrain, either.
| ryandrake wrote:
| Don't forget (if you're VFR): Your eyeballs looking out the
| window. My instructor would pull the circuit breaker on the
| GPS if I looked at it too often, to encourage me to always be
| actually looking outside of the aircraft for ground reference
| points and point them out on the paper chart.
| jillesvangurp wrote:
| NDB (non directional beacon) is also still in use in quite a
| few places. With two beacons in reach and a bit of math, you
| can cross reference your position.
| FabHK wrote:
| While you're at it, please shift to metric! Feet for altitude,
| nautical miles for distance, statute miles for visibility, metres
| for runway visual range (most often)...
|
| Take a plane that has a glide ratio of 1:10, say. It's 1 km high.
| How far can it glide? 10 km.
|
| Now it's 3000 ft high. How far can it glide, in nautical miles?
| joncrane wrote:
| Neat article, but I have a question that's kind of a tangent:
| what are those rose-colored lenses that the pilots have flipped
| down to look through the windshield of the plane in the picture?
| BrentOzar wrote:
| A heads-up display: https://www.flyingmag.com/how-it-works-
| head-up-display/
| this_is_not_you wrote:
| My first guess would be heads-up displays. On photos they
| always appear blank.
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