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Transponder Landing System enables precision approaches at McMurdo in Antarctica

flightradar24.com

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Re: Transponder Landing System enables precision approaches at McMurdo in Antarctica

#21

Post by MobiusHorizons »

mmaunder wrote: post #17

Wow that’s badass. It’s tempting to argue that a GPS based RNAV approach could have similar performance but this has several advantages: The ground based equipment dictates approach path with no updates to onboard approach databases on aircraft needed. RNAV can’t do curved approaches on a glide slope as far as I know. ILS minimums are generally slightly lower than LPV which is the RNAV approach type with lowest minim…

Would RNAV be able to handle the runway moving nontrivial distances? That seems to be one of the problems this solves.

Re: Transponder Landing System enables precision approaches at McMurdo in Antarctica

#22

Post by MobiusHorizons »

bigiain wrote: post #18
kylehotchkiss wrote: post #9

Year round aviation access to Antartica. Well Done! Every step towards McMurdo becoming a normal city despite its location seems like such an incredible accomplishment. Can this work at pole station too? I realize there's a lot of other considerations landing there in the winter (fuel freeze temp?) but the less isolated it becomes, the more science we can get.

I'm guessing there are a whole bunch of assumptions and simplifications in standard aviation practice around lat/long, GPS, and magnetic compasses - which all fail at the pole(s). I bet it's "quite exciting" to be a pilot trying to fly at the pole doing anything apart from flying straight and level right past. Your longitude readout becomes useless as the lines of longitude converge. Your GPS altitude becomes wildly…

I think a lot of aviation navigation is by named waypoints on charts. I am definitely not an expert, but I believe some of these would be visually identifiable in good weather, or even identified by radar transponders. Compas deviations would certainly be an issue, but I believe are important to account for even in much more populated areas. Aviation does use gps now, but many of the previous systems still exist and are quite clever. The ILS system this is based off of is such a system.

Re: Transponder Landing System enables precision approaches at McMurdo in Antarctica

#23

Post by jcalvinowens »

mmaunder wrote: post #17

Wow that’s badass. It’s tempting to argue that a GPS based RNAV approach could have similar performance but this has several advantages: The ground based equipment dictates approach path with no updates to onboard approach databases on aircraft needed. RNAV can’t do curved approaches on a glide slope as far as I know. ILS minimums are generally slightly lower than LPV which is the RNAV approach type with lowest minim…

> RNAV can’t do curved approaches on a glide slope as far as I know.

RNP approaches can, Monterey has one: https://aeronav.faa.gov/d-tpp/2408/00271RRZ28L.PDF

Re: Transponder Landing System enables precision approaches at McMurdo in Antarctica

#24

Post by 0xEF »

macintux wrote: post #19

Unsurprisingly, the challenges of getting to, living in, and managing infrastructure in Antarctica is a frequent theme of posts shared here. Some previous discussions of note: * How to Operate an Airport in Antarctica (also via flightradar24.com): https://news.ycombinator.com/item?id=26340384 (68 comments) * Nuclear Power at McMurdo Station, Antarctica: https://news.ycombinator.com/item?id=27549484 (192 comments) And…

Sadly, brr.fyi is done with the Antarctica stint and currently looking for another job.

Re: Transponder Landing System enables precision approaches at McMurdo in Antarctica

#25

Post by p_l »

mmaunder wrote: post #17

Wow that’s badass. It’s tempting to argue that a GPS based RNAV approach could have similar performance but this has several advantages: The ground based equipment dictates approach path with no updates to onboard approach databases on aircraft needed. RNAV can’t do curved approaches on a glide slope as far as I know. ILS minimums are generally slightly lower than LPV which is the RNAV approach type with lowest minim…

Main issue with RNAV is that GPS is just not that precise. WAAS helps a bit but it's not as good as having advanced local augmentation or things like RTK, and those are also non-trivial to deploy (not to mention there's no common standard for ground augmentation for aircaft to use).

So ILS or MLS had the benefit of being able to provide better precision without things like realtime ionosphere monitoring and correction. TLS let's you use all sorts of augmentation mechanisms without modifying the aircraft too.

Re: Transponder Landing System enables precision approaches at McMurdo in Antarctica

#26

Post by p_l »

bigiain wrote: post #18
kylehotchkiss wrote: post #9

Year round aviation access to Antartica. Well Done! Every step towards McMurdo becoming a normal city despite its location seems like such an incredible accomplishment. Can this work at pole station too? I realize there's a lot of other considerations landing there in the winter (fuel freeze temp?) but the less isolated it becomes, the more science we can get.

I'm guessing there are a whole bunch of assumptions and simplifications in standard aviation practice around lat/long, GPS, and magnetic compasses - which all fail at the pole(s). I bet it's "quite exciting" to be a pilot trying to fly at the pole doing anything apart from flying straight and level right past. Your longitude readout becomes useless as the lines of longitude converge. Your GPS altitude becomes wildly…

Flying over north pole became quite popular due to great circle routes going that way. use of GPS in civilian aviation actually came from compass getting confused during polar flight resulting in heading reversal. GPS satellites also supported polar operations from the start as the critical user needed flights over north pole. (this is one of those cases where typical map projections confuse people).

That said, magnetic compass deviations are common all over the world due to things like iron ore veins, so maps have corrections available.

GPS isn't used for altitude in aircraft in practice, it's too inprecise - barometric altimeter plus radar altimeter are the precise instruments for that.

Re: Transponder Landing System enables precision approaches at McMurdo in Antarctica

#27

Post by zokier »

How they do aircraft positioning is the most interesting aspect here. The article says its multilateration, but I don't think it's quite the tradional simple multilat. Instead they are doing some cleverness with two angle of arrival detectors arranged perpendicularly, which feels novel?

Found this random paper that has more details

https://www.icasc.co/wp-content/uploads/2023/02/Application_...

Re: Transponder Landing System enables precision approaches at McMurdo in Antarctica

#28

Post by lxgr »

mmaunder wrote: post #17

Wow that’s badass. It’s tempting to argue that a GPS based RNAV approach could have similar performance but this has several advantages: The ground based equipment dictates approach path with no updates to onboard approach databases on aircraft needed. RNAV can’t do curved approaches on a glide slope as far as I know. ILS minimums are generally slightly lower than LPV which is the RNAV approach type with lowest minim…

I would honestly not be surprised if pure GPS approaches were discontinued in the near future, giving all the spoofing incidents recently, and the shocking vulnerability of avionics systems to them. (I would have expected the GPS/INS to reject highly unplausible GPS signals in favor of the IRS, and huge clock deviations in favor of a simple internal quartz oscillator, but apparently neither is the the case.)

TLS seems much less vulnerable to spoofing, given the signal strengths involved.

The idea of an onboard TLS spoofer seems both feasible and very scary, though, now that I think about it...

Re: Transponder Landing System enables precision approaches at McMurdo in Antarctica

#29

Post by lxgr »

MobiusHorizons wrote: post #21
mmaunder wrote: post #17

Wow that’s badass. It’s tempting to argue that a GPS based RNAV approach could have similar performance but this has several advantages: The ground based equipment dictates approach path with no updates to onboard approach databases on aircraft needed. RNAV can’t do curved approaches on a glide slope as far as I know. ILS minimums are generally slightly lower than LPV which is the RNAV approach type with lowest minim…

Would RNAV be able to handle the runway moving nontrivial distances? That seems to be one of the problems this solves.

You'd have to update the approach plates and their digital version in the FMS's database occasionally, but that has to happen anyway, given that I believe almost all of them still use magnetic north as a reference. (Not sure if modern FMSes can store that data in true north format internally, but at least once the runway gets officially renamed I bet that requires an update.)

Re: Transponder Landing System enables precision approaches at McMurdo in Antarctica

#30

Post by lxgr »

p_l wrote: post #26
bigiain wrote: post #18

Earlier quoted context omitted.

I'm guessing there are a whole bunch of assumptions and simplifications in standard aviation practice around lat/long, GPS, and magnetic compasses - which all fail at the pole(s). I bet it's "quite exciting" to be a pilot trying to fly at the pole doing anything apart from flying straight and level right past. Your longitude readout becomes useless as the lines of longitude converge. Your GPS altitude becomes wildly…

Flying over north pole became quite popular due to great circle routes going that way. use of GPS in civilian aviation actually came from compass getting confused during polar flight resulting in heading reversal. GPS satellites also supported polar operations from the start as the critical user needed flights over north pole. (this is one of those cases where typical map projections confuse people). That said, magne…

> use of GPS in civilian aviation actually came from compass getting confused during polar flight resulting in heading reversal

Do you have a source for that? I was under the impression that INS-based navigation was much more precise than for that to have been an issue by the time GPS became available to civil aviation.

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