As someone who basically hates flying (but does when I have to) I have a question regarding flight plans.
So, looking up in my backyard here in Vegas, I see planes coming inbound and they are all on the same path…I mean almost to the millimeter. (This is not on approach per se, they go over my backyard - go way east a few miles, then turn around and come back west for landing at McCarren airport.)
Then I see planes way, way up - I assume they might be flights from Los Angeles to NY or Europe and again - they are almost always in the exact same position in the same direction.
It is almost as if there really were a highway in the sky.
Is this because they literally take the shortest distance, and that is why they seem to be flying in the exact same position - both inbound and those flying way high on paths elsewhere?
So as not to hit each other head on, are east bound flights at a certain height and west bound flights at a different altitude? And different altitude for north and south bound flights as well?
Just wondering…as a fearful passenger who does have to fly occasionally, it would be nice to know there is order up there.
There almost literally is a highway in the sky - the whole world is covered with a network of waypoints, and planes fly from one to another, not just as the spirit moves them (except for local light-aircraft flights, but they do that well out of the way of commercial aviation).
Yes, air-traffic controllers make extensive use of the z-axis to make sure that planes aren’t going to end up on a collision course.
A more qualified person will be along in due course to give a fuller answer.
Pretty much answered. The quickest route from A to B is normally a straight line, however flight routes (airways) used to be primarily defined by ground based radio beacons which would be located around the country, mainly at airports, towns, cities etc. This means that a straight line route may not be available as the beacons are not in the right places. A route from A to B may not be able to be flown direct but may require flying via C, D, and E. Some routes are now defined by latitude/longitude waypoints that can be flown by area navigation systems such as GPS, this means that more routes are now a straight line between A and B.
EDIT: inbound routes will only be the same as over-flight routes up until the point that the aircraft starts maneuvering for the approach and landing. In some cases this can start 100 miles out.
The rules vary by country but altitudes are divided up amongst either east/west tracks or north/south tracks. In Australia east bound flights fly odd thousands of feet and west bound flights fly even thousands. At higher altitudes (29,000 and above I think) the difference between opposite direction altitudes increases to 2000 feet. This is due to increasing altimeter errors at higher altitudes. Like with lateral navigation, the vertical navigation rules are changing and in some parts of the world the higher altitudes have started using a 1000 foot split provided the aircraft is approved for it.
When on departure and approach, ATC apply altitude restrictions and standard arrival and departure routes to keep aircraft separated. They can also give radar vectors which involves progressively giving headings for an aircraft to fly until it is either positioned for a landing or for tracking via the airways.
The increasing use of GPS for navigation means that aircraft our now much more accurately flying the airways, even the ones defined by ground based radio beacons (the location of the ground based beacons are in the aircraft GPS data base). This means that if two aircraft are on the same route on opposite headings and at the same altitude, due to a controller or pilot error, they are much more likely to collide. To reduce the risk of this, it is becoming accepted practice to fly a small offset from the airways. So if everyone always fly 1 mile right of their track then any aircraft coming the other way will be separated laterally by 2 miles as well as having vertical separation.
In addition to all this, there are airways routes that are one way only. If you want to fly from A to B then you fly via C, D, and E, but if you want to fly from B to A, you go via F, G, and H.
The busier the airspace is, the more likely there will be added protections such as one way routes.
The above applies to IFR flights (airline flights are IFR.) There is a similar set of rules for VFR flights although they can pretty much do whatever they like outside of controlled airspace.
Regarding “highway in the sky” or airways, in the US at least, the air traffic control system has mostly evolved to the point where suitably equipped aircraft (pretty much all airliners nowadays) only need to use designated departure and arrival routes near the busy terminal areas. Once they are out of the way, it’s usually just point A direct to point B. For example, a flight from LAX to JFK may depart on a standard route for everyone leaving LAX to the north east. This will lead the plane to a point somewhere a couple hundred miles from LAX. From there, it may be cleared to fly directly across the country to a point a couple hundred miles from New York, where controllers will start to sequence everyone into a neat line and feed them into the terminal area.
Yes. Basically for a VFR flight you say, ‘I’m taking off at [time Zulu] from [this airport] and plan to land at [this airport] at [time Zulu]. I have [this many hours] of fuel, and there are [this many] people on board. I’ll be flying [this high] and at [this speed]. In case of emergency notify [this person].’
If you don’t close your flight plan within 30 minutes of your expected arrival time, someone will start looking for you. Flight Service might call the tower at the destination airport and ask if you landed there. If they don’t know, then the next step would be a ramp check (look for your airplane in the parking area). If you’re not there, maybe some more phone calls to see if anyone has heard from you. If no one has, then Seach & Rescue will be notified and the Civil Air Patrol will start looking for you.
In my experience (VFR), that’s what a flight plan is for: to allow people to start looking for you within a reasonable time if you don’t show up where you say you will. If you fail to close it (because you forgot to – not because you’ve actually crashed) and a search is initiated then you may be liable for the cost of the search. That’s why they have ‘Flight plan closed?’ signs on the way out of airports.
Flight plans are not required for VFR flights.
1920s Style “Death Ray”: Yes, ‘Odd fellows fly east’ here as well. I’m pretty sure it’s an international rule.
Search and rescue is one of the main reasons for both VFR and IFR flight plans. *
In the case of IFR, the flight plan also allows controllers to cordon off airspace in the event of a communications failure. In that situation (unless weather permits a landing in visual conditions), the pilot is expected to fly the route on file and perform an instrument approach at the destination. ATC would then not permit other IFR traffic to operate in that area, on the assumption that the pilot could not scan visually for traffic.
You can actually obtain an IFR clearance without having filed a flight plan, so long as you’re staying in a controller’s area of coverage. This is referred to as a “pop-up”, or “local” IFR clearance.
The pilot usually requests that clearance with the intention of flying an instrument approach in the local area. That being the case, and assuming good radar contact, the need for search and rescue information on a flight plan is obviated.
Of course, this is at ATC’s discretion. I have local IFR clearances approved routinely where I fly, but you may have less luck with ATC in busier airspace.
Do altimeters’ natural precision variations mean that aircraft will be spread out fairly evenly over the entire 1000 foot section, or will there be a cluster of aircraft, all at 10,000 feet say, and a few at 10,250 or 9,750? Do pilots deliberately fly in a range +/- 100 feet of their supposed lane in order to naturally vary this or do the natural variations create that without having to deliberately create it?
Altimeters are re-set to local barometric pressure frequently during flight. When passing from one controller’s area of coverage to another, the first thing the new controller tells a pilot is the local altimeter setting. That’s for IFR, or when flying VFR with ATC advisory service.
When flying VFR and not in contact with a controller, a savvy pilot can pick up the local altimeter setting in a few ways. However, in a plane with no radio (which is permissable in some airspace) you’d have no way of setting it properly.
Theoretically, it’s great if everyone is on the same page. And besides altimeter settings, we’re also supposed to fly certain altitudes based on direction of flight (as previously mentioned in this thread). But yes, some pilots do hedge their bets.
For example, if I’m flying westbound VFR, I’m supposed to fly even + 500, such as 4500’ or 6500’. But sometimes I’ll fly 6300 or 6700 instead. Once or twice that’s helped me avoid a merge.
For IFR, you fly what you’re told to fly, and you generally do it with precision and the correct altimeter setting. But stuff happens, and sometimes there’s slop in an instrument. ATC can check that against their radar, but aren’t too likely to notice a small difference. ATC also sees your transponder’s altitude signal, but that only displays what you’ve set in the instrument. If you set it wrong, it will read wrong to ATC also.
The variation in altimeter setting is less a concern for traffic avoidance, and more a concern for terrain avoidance, especially on landing. Very important to have the correct altimeter setting when flying an instrument approach or departure. Some instrument procedures have conditional minimums (the lowest altitude you can fly) depending on the source of your altimeter information.
You don’t want them evenly spread because that means opposite direction traffic may be too close. Altimeters are allowed an error of 65 feet on the ground, I’m not sure how much error the calibration allows for at higher altitudes. The two primary altimeters on our aircraft will generally be within 20 feet of each other at all altitudes while the secondary altimeter may be a couple of hundred feet out up high.
Aircraft with an autopilot will fly the selected altitude very precisely. If the pilot is hand-flying then they will try and fly the altitude exactly but won’t be as consistent as the autopilot, they should be able to fly within 10-20 feet or so depending on weather and how easy the aeroplane is to fly and if you are 50 feet off the desired altitude you’d be expected to be doing something about it. In controlled airspace you are not permitted to fly an altitude other than what you’ve been cleared for, so if you’ve been cleared to 25,000 feet, you must attempt to fly 25,000 feet, not 24,900.
It’s a bit like tracking tolerances. There are tolerances within which you must be to be considered on track, but you are not permitted to use those tolerances to deliberately fly off the track’s centreline.
I left it a bit open because I know that in New Zealand they fly odds north and evens south, most likely because NZ is a long thin country and most routes are oriented north/south.