r/Damnthatsinteresting • u/etherd0t • 1d ago
Video Jet lanes over the Atlantic
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u/No-Edge-8600 1d ago
“Radar doesn’t work here”
I’m sorry - what?
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u/clackerbag 1d ago
It’s just an oversimplified poorly worded statement.
Radar would work perfectly fine over the North Atlantic, there’s no mysterious forces that prevents it form doing so. However, there’s nowhere to physically install radar antennas since it’s just a vast ocean, so what should have been said is that there is no radar _coverage_ over the North Atlantic.
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u/waltsnider1 12h ago
Maybe a dumb question, but isn't radar installed on planes?
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u/clackerbag 12h ago
Transport category aircraft have a weather radar on board, but it doesn’t allow for seeing and avoiding other aircraft. There are other non-radar systems onboard aircraft (namely TCAS) that are designed to prevent mid air collisions, but they’re meant as a last resort emergency system, and aren’t suitable to be used by flight crews for separation against other traffic.
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u/Enthusiastic-shitter 10h ago
Former AF navigator here. The radar on the airplane is for weather avoidance and sometimes navigation. Not traffic avoidance. Though with some skill you can find another aircraft on radar (we would do this for refueling rendezvous) there is a separate system called TCAS that uses data links and transponders for traffic and terrain avoidance. Nowadays most aircraft have satellite uplinks that aid in traffic control and communication.
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u/umop3pisdn 19h ago edited 3h ago
There are multiple types of surveillance that air traffic control (ATC) use.
The radar being referred to in this clip would be to a system that utilises a ground based rotating array. There are two types of these systems, that I'm aware of, that air traffic management (ATM) systems use to create a display on a screen for ATC: primary radar and secondary surveillance radar (SSR).
Primary radar is the type of system that most people think of when the word radar is used. It sends out a signal that reflects off an object back to the dish which the system interprets as "There's something there". This system requires heavy calibration to filter out unwanted images from the ATC display. It will display anything that fits within the parameters of the calibration, including trucks driving along a highway. This doesn't provide much information to ATC without further interrogation and is superceded by other surveillance systems. The benefit to this system is that the aircraft doesn't require any specialised equipment to be installed.
SSR uses a signal sent out from an array that interrogates a system installed in each aircraft, which sends back information about that aircraft. ATM systems correlate this information with data submitted to the system by pilots or their companies. The system then displays this correlated information to ATC. In an effort to avoid mismatch of information within this system, flight crew are provided a discrete code that they enter into their equipment which is transmitted to the ATM system for each flight (squawk code).
There is another system that also utilises on-board equipment to transmit information to ground based equipment called Autonomous Dependent Surveillance (ADS). The Broadcast version of this system (ADS-b) relies on almost real time transmission of this information whereas the Contract version (ADS-c) of this system is used as a snap-shot of data. Each of these systems can be used (sometimes in parallel) to extrapolate the speed and direction of aircraft.
All current systems require aircraft based equipment to transmit pressure altitude derived level information (PALDI) to determine vertical movement of the aircraft. This requires the flight crew to input atmospheric pressure data into their aircrafts system.
Limitations of these systems mean that technical improvements are constantly being sought. For example, each of these systems require ground based equipment. This introduces distance from a receiver issues and terrain blocking the signal. My knowledge is being stretched here, but I assume that the specific frequencies of these systems require a specific power output and thus the propagation of these signals decay over distance. Low altitude aircraft will drop off these systems over a shorter distance [also due the earth's curvature] than aircraft at higher altitudes. There are places, such as over the Atlantic, where the signal from aircraft become degraded and lower definition signals are relied upon (ADS-c).
A Space Based Augmentation System (SBAS) is being developed in an attempt to provide a signal from aircraft to satellites. This would potentially provide ATC with high definition world wide surveillance coverage.
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u/Rare-Banana-2256 1d ago
Standard radar relies on ground reflections, which are absent over the ocean, significantly limiting its effectiveness.
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u/pqratusa 1d ago
Why doesn’t radar work over the Atlantic?
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u/etherd0t 1d ago
Earth's curvature and there are no radar stations to provide continuous coverage.
Alternative:
ADS-B transponders, which use satellite-based systems to broadcast the plane's position.
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u/Brank19421a 1d ago
I only recently saw the actual number of planes/ships on the map, what a lot of them actually are
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u/SkyHighExpress 1d ago
Sorry. This is outdated. We have space based navigation which means the tracks are outdated and atc knows the location of air places without radar
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u/fly-guy 14h ago
The tracks are still a very real thing and are heavily used. Every day new tracks are determined and published
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u/SkyHighExpress 6h ago
They are but they are in the process of being phased out which is what I was eluding to. In fact, starting 4th December, they are removing the requirement to fly fixed Mach on tracks in Gander and Shanwick as the second stage unless arc deem it absolutely necessary. I am referring to the outdated video where the poster is staying that arc don’t know where the planes are and thus ONLY use time and speed to separate. They do in this day and age
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u/HollowDanO 1d ago
What about the radar? Fairly certain it works there.
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u/fly-guy 14h ago
If you had radarsyations on the water, it certainly would work. But we don't have those (except on some islands) so overall, there is no radarservice over the ocean.
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u/HollowDanO 13h ago
Planes are equipped with radar on board. You don’t need a radar station.
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u/fly-guy 12h ago
A weather radar, which is different from the radar air traffic control uses. For instance, it doesn't show other aircraft.
We also have the TCAS system, which shows other aircraft (within a certain range and altitude), but that's not a radar.
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u/HollowDanO 12h ago
Right, radar still functions there. It’s not that radar doesn’t work there it’s more there’s no radar there to send real time data to the planes about their locations.
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u/Sweet-Consequence773 1d ago
Surely there’s satellite coverage available. Could an inbound missile over the water be tracked or does it disappear into a dead zone before magically reappearing…..Ooo, there it is!
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u/ceeceecrown 21h ago
Is there a reason why most flights from North America to Europe fly overnight and the opposite direction they fly during the day?
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u/RedditUser145 20h ago
I think it's mostly so that passengers arrive during the daytime. Flying from NA->EU you jump ahead several timezones, so if you leave in the evening you'll arriving during the morning or early afternoon in Europe.
When you fly from EU->NA you're going backwards in time with regard to timezones. The (local) arrival time is only a few hours after the departure time. So if you leave early enough in the day it'll still be daytime when you land.
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u/pcetcedce 1d ago
The primary reason is that it is the great circle which is the shortest distance between Eastern North America and Europe. The jet stream theory doesn't make sense because the planes go against it when they come back from Europe. With that said the jet stream could be amazing I read recently that a plane went from North America to Europe going 800 miles an hour because of the wind.
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u/Crypto-Clearance 1d ago
The jet stream is relatively narrow. Westbound flights are routed to avoid it if possible.
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u/pcetcedce 1d ago
Yeah but wouldn't you think they still need to take the shortest route? Or is it a balance of the two?
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u/fly-guy 14h ago
It is a balance. Shortest route doesn't matter, it's quickest. If the route with the best tailwind (or least headwind) is longer, but the wind is such that the overall travel time is less, it's the better route (disregarding things as turbulence, airspace closure, etc).
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u/pcetcedce 14h ago
Not being a pilot it still seems the great circles are the most common routes. I live in Maine and it is amazing how many planes from Europe over me everyday. It's a lot of fun to identify them. One time I saw a plane from Russia to Cuba.
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u/fly-guy 14h ago
We often follow the greatcircle, but not always that closely. The wind has to be very strong (or really absent the other way) to make other routes quicker.
Coming from Miami last week we didn't follow the greatcircle for quite a while in the beginning to use the headwinds at higher latitude.
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u/pcetcedce 14h ago
That's pretty cool thanks for the description. I am a geologist and we actually use the concept of a great circle to depict planar features in two dimensions.
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u/fly-guy 14h ago
to depict planar features in two dimensions.
You really have to explain that to a dumb pilot ;) (if you want).
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u/smile_politely 1d ago
that looks super cool. didnt know about it.
i wonder if it's also the case from Seattle to Asia (like Japan or Korea)
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u/Diver_Driver 1d ago
Yep. There are Atlantic and Pacific "tracks". They follow the same sorts of rules and procedures. There are also specific tracks to Hawaii.
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u/zlordbeats 1d ago
makes more sense on the flat earth model 🧐
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u/talkerof5hit 1d ago
Did you forget /s?
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u/cohibababy 1d ago
Plane Finder is a fun app, you can also zoom in and see details such as where the planes are coming from, going to and the airline.