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:
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 minimums.
This supports older aircraft with ILS (localizer with glide slope) that don’t have a WAAS capable GPS.
Edit: Also, using the Mode S transponder with precision approach radar instead of ADSB-out for the aircraft position means older planes without ADSB (because they don’t fly under a mode C veil) can be supported and it also means the base is trusting their equipment for the aircraft position rather than trusting an aircraft that potentially doesn’t have an SBAS GPS on board.
RNAV RNP approaches can contain curved descents. They’re usually used in areas with high terrain but I don’t see why they couldn’t be used down here. LPV minimums seem to usually be very close to ILS minimums these days.
That said, it’s always nice to have a ground-based alternative approach. I wonder if they have sustained issues with GPS this far south.
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.
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...
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 inaccurate because the orbital inclinations of the constellation means they never get above 45 degrees or so from the horizon. Your compass is pretty much trying to point straight down (and at the magnetic pole which is some way apart from the rotational axis of the earth pole).
And it's cold, likely very bad weather, the landscape make orienting yourself and even seeing upcoming mountains challenging, and you are a long long way from a safe landing spot and even further from any realistic help.
The Instrument Carrier Landing System (ICLS) is basically just an upgraded version of the civilian ILS which they squashed down onto a ship. It broadcasts a beam of radio waves into the air and any aircraft can pick it up and follow the glide slope.
There is also the Automatic Carrier Landing System (ACLS), which is roughly equivalent to this system. Radar receivers on the carrier are fed into a computer, which calculates the aircraft's position and transmits back commands back to the aircraft's autopilot.
The cool part about this Transponder Landing System is that it doesn't require any equipment upgrades to the aircraft. An aircraft equiped with original ILS equipment from the 60s can use it.
The glacier moves orders of magnitude slower than an aircraft carrier does, so I doubt that the TLS used does any comparable automatic adjustments. It's probably more than enough to periodically survey the runway and input that data manually.
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?
There a couple companies that make a DILS where the localizer and glideslope can be temporarily deployed. The intent is for emergency or short term use.
I would guess it to be pretty rare that multiple aircraft would be on approach at once, and if so, I'd imagine one could hold at a distance to allow approaches to be serialized.
There are a few other airports that have this, and my understanding is that only one aircraft can do the approach at a time. If another plane tunes in the ILS they will see the localizer and glideslope indications for the other plane.
I’m not sure how the TLS figures out what transponder to look at, I guess either the controller enters in the code of the plane on approach or there’s some reserved transponder code for the approach.
macintux|1 year ago
* 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 perhaps my favorite blog, brr.fyi makes frequent appearances here. An example:
* South Pole Water Infrastructure: https://news.ycombinator.com/item?id=40615530 (63 comments)
For all Antarctica posts: https://brr.fyi/tags#south-pole
0xEF|1 year ago
mmaunder|1 year ago
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 minimums.
This supports older aircraft with ILS (localizer with glide slope) that don’t have a WAAS capable GPS.
Edit: Also, using the Mode S transponder with precision approach radar instead of ADSB-out for the aircraft position means older planes without ADSB (because they don’t fly under a mode C veil) can be supported and it also means the base is trusting their equipment for the aircraft position rather than trusting an aircraft that potentially doesn’t have an SBAS GPS on board.
turrican|1 year ago
That said, it’s always nice to have a ground-based alternative approach. I wonder if they have sustained issues with GPS this far south.
jcalvinowens|1 year ago
RNP approaches can, Monterey has one: https://aeronav.faa.gov/d-tpp/2408/00271RRZ28L.PDF
p_l|1 year ago
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.
lxgr|1 year ago
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...
MobiusHorizons|1 year ago
kylehotchkiss|1 year ago
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.
bigiain|1 year ago
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 inaccurate because the orbital inclinations of the constellation means they never get above 45 degrees or so from the horizon. Your compass is pretty much trying to point straight down (and at the magnetic pole which is some way apart from the rotational axis of the earth pole).
And it's cold, likely very bad weather, the landscape make orienting yourself and even seeing upcoming mountains challenging, and you are a long long way from a safe landing spot and even further from any realistic help.
webnrrd2k|1 year ago
I wonder how similar their ILS is to the ILS used on navy aircraft carriers?
phire|1 year ago
The Instrument Carrier Landing System (ICLS) is basically just an upgraded version of the civilian ILS which they squashed down onto a ship. It broadcasts a beam of radio waves into the air and any aircraft can pick it up and follow the glide slope.
There is also the Automatic Carrier Landing System (ACLS), which is roughly equivalent to this system. Radar receivers on the carrier are fed into a computer, which calculates the aircraft's position and transmits back commands back to the aircraft's autopilot.
The cool part about this Transponder Landing System is that it doesn't require any equipment upgrades to the aircraft. An aircraft equiped with original ILS equipment from the 60s can use it.
lxgr|1 year ago
standardUser|1 year ago
https://wandereatwrite.com/how-i-got-paid-to-live-in-antarct...
butlike|1 year ago
zokier|1 year ago
Found this random paper that has more details
https://www.icasc.co/wp-content/uploads/2023/02/Application_...
gte525u|1 year ago
computerdl|1 year ago
dweekly|1 year ago
https://www.usap.gov/sciencesupport/scienceplanningsummaries...
I would guess it to be pretty rare that multiple aircraft would be on approach at once, and if so, I'd imagine one could hold at a distance to allow approaches to be serialized.
cameldrv|1 year ago
I’m not sure how the TLS figures out what transponder to look at, I guess either the controller enters in the code of the plane on approach or there’s some reserved transponder code for the approach.
FireBeyond|1 year ago
phire|1 year ago
polemic|1 year ago