How do Airliners navigate without GPS?

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England
Hi.
Been various news items in UK about alleged Russian interference with the GPS that Airliners use to navigate. This is allegedly happening over the Baltic states. UK has a large population of eastern Europeans, so a lot of UK budget airlines operate there.


How can an Airliner crew navigate without GPS?

Would a Pilot know if the GPS signal was being 'spoofed' into thinking the aircraft is in a different location than it actually is?

Thank you.
 
I assume a pilot also uses a compass in conjunction with a flight computer. There use to be a navigator on flights years ago. I have ZERO clue to anything I said. Interesting topic.
 
Hi.
Been various news items in UK about alleged Russian interference with the GPS that Airliners use to navigate. This is allegedly happening over the Baltic states. UK has a large population of eastern Europeans, so a lot of UK budget airlines operate there.


How can an Airliner crew navigate without GPS?

Would a Pilot know if the GPS signal was being 'spoofed' into thinking the aircraft is in a different location than it actually is?

Thank you.

I flew the A320 without any GPS until about 2004? We navigated with just the FMS IRS ( inertial reference system …which drifts over time unless updated by ground based radio signals ).

Other than the fact we obviously could not fly any GPS approaches, it did not affect en route navigation.

We can fly today with no GPS ( we have two….never flown with one inoperative ) but would not be able to fly a GPS approach. Certain airspace requires the use of GPS ( RNP 4 ….long distance flights without land based signals to update FMS….also RNP 1 & 2 airspace ).

When I fly to the Caribbean , I don’t need GPS ( airspace ) unless the flight is over 5.7 hours since IRS FMS alignment at the gate before pushback.

Depends on the route and whether or not pilots will need it for a GPS approach.

Flight dispatch would take any suspected GPS jamming into consideration on certain routes and pilots would be aware due to it being mentioned on the flight plan ( NOTAMS ).
 
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I assume a pilot also uses a compass in conjunction with a flight computer. There use to be a navigator on flights years ago. I have ZERO clue to anything I said. Interesting topic.
We would never navigate using just the compass unless we had lost everything else.

I fly a lot in the “ Bermuda Triangle” so it would be useless anyways lol 😊
 
The primary non-GPS means of aviation navigation is ground based navigation systems: mainly, VOR and DME.
These are stations worldwide that transmit radio signals. Receivers in the airplane tell you what direction the station is (which radial you are on), and how far away it is. Every pilot, from flying little bug-squashers to big commercial airliners, knows how to use VOR/DME.

Here in the USA, the VOR/DME system is being decommissioned, but not entirely. The FAA is keeping a minimum baseline of stations necessary for navigation as a backup for GPS system failures. In flight, I've seen GPS fail, and I've seen VOR fail, but I've never seen both fail at the same time. Also, when flying small planes VFR (visual flight rules), the primary navigation instrument is the Mark VII eyeball looking out the windshield, and situational awareness.
 
Dead reckoning

Then there's this: “Second star to the right, and straight on till morning” as Peter Pan said and which was quoted by Captain James T. Kirk.
 
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Many modern airliners use a combination of multiple GPS receivers, multiple IRS units (inertial reference) and multiple VOR/DME receivers (ground based). The FMS (flight management system) takes all those inputs and automatically figures out where it is with high confidence.

You can lose numerous sources (even GPS) and it’ll still know where it is with reasonable accuracy - at least for enroute flying.

I’ve been GPS “jammed” many times flying by the White Sands Missile range / Holloman AFB. ATC lets you know it’s gonna happen as you approach the area. You just get a GPS Fail warning but can continue cruising with IRS and automatic DME/DME triangulation.

The loss of GPS does mean you can’t do approaches that require GPS though.
 
I listen to a lot of old time radio and there was an episode on this topic. Not that they had GPS back then but the episode was about a pilot who got lost and air traffic control was trying to get him orientated based on ground signals. It had to do with listening to beeps on the radio. Da-Di or Di-Da. Depending of if the plane was coming towards or away from the signal. It was a lot more technical than I imagined.

This is the episode for anyone curious.
 
I listen to a lot of old time radio and there was an episode on this topic. Not that they had GPS back then but the episode was about a pilot who got lost and air traffic control was trying to get him orientated based on ground signals. It had to do with listening to beeps on the radio. Da-Di or Di-Da. Depending of if the plane was coming towards or away from the signal. It was a lot more technical than I imagined.
...
This is historically correct. One of the older ground based radio nav systems worked like that. Different patterns of dots and dashes if you were R or L of intended path, and when you were on the path they blended into a different tone. I am so glad that I never had to use that system!

Another older system that is being phased out is called ADF/NDB: https://en.wikipedia.org/wiki/Non-directional_beacon
My plane still has an old receiver for this and I occasionally pick up a live stations. But they are mostly phased out. I should remove that hunk of junk from my panel one of these days... However, they use AM radio frequencies so it does let me listen to AM radio while flying.
 
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Hi.
Been various news items in UK about alleged Russian interference with the GPS that Airliners use to navigate. This is allegedly happening over the Baltic states. UK has a large population of eastern Europeans, so a lot of UK budget airlines operate there.


How can an Airliner crew navigate without GPS?

Would a Pilot know if the GPS signal was being 'spoofed' into thinking the aircraft is in a different location than it actually is?

Thank you.
Sextant of course ! jking
 
This is historically correct. One of the older ground based radio nav systems worked like that. Different patterns of dots and dashes if you were R or L of intended path, and when you were on the path they blended into a different tone. I am so glad that I never had to use that system!

Another older system that is being phased out is called ADB/NDB: https://en.wikipedia.org/wiki/Non-directional_beacon
My plane still has an old receiver for this and I occasionally pick up a live stations. But they are mostly phased out. I should remove that hunk of junk from my panel one of these days... However, they use AM radio frequencies so it does let me listen to AM radio while flying.
No more NDB approaches in Canada and am curious if it’s the same in the U.S now?

Pilots are not even trained to fly NDP approaches anymore up here as of 2 years ago. No longer a requirement to obtain an IFR rating.
 
No more NDB approaches in Canada and am curious if it’s the same in the U.S now?

Pilots are not even trained to fly NDP approaches anymore up here as of 2 years ago. No longer a requirement to obtain an IFR rating.
I believe Alaska has most of the still in service NDBs. NDB hasn't been a training requirement in the US for quite a long time.
 
I assume a pilot also uses a compass in conjunction with a flight computer. There use to be a navigator on flights years ago. I have ZERO clue to anything I said. Interesting topic.
There used to be 4 crew members, the Captain, 1st Officer, Engineer & Navigator.
Nav was the first to go followed by the Engineer then by 2 engines as in transoceanic flights for safety 4 engines were
required, now they say 2 are sufficient, and they are IF both are working :cool:;)
 
There used to be 4 crew members, the Captain, 1st Officer, Engineer & Navigator.
Nav was the first to go followed by the Engineer then by 2 engines as in transoceanic flights for safety 4 engines were
required, now they say 2 are sufficient, and they are IF both are working :cool:;)
We are back to 3/4 pilots ( on board, not always in the cockpit ) for safety on most overseas routes even though only 2 are required by the manufacturer.

I fly the longest turns allowed with only two pilots up here ( 14 hours ).
 




How would I know if ….

GPS signal jammed: cockpit alert ( “ GPS primary lost” on navigational display ).

GPS signal spoofed: old school comparing raw data position ( land based radio signals….VOR/DME ) versus computed position ( GPS ).

I would have previously thought receiving a cockpit alert “ FMS/GPS POS DISAGREE” alert would warn us but apparently not.
Hi.
Thank you for helping me out.

'GPS signal spoofed: old school comparing raw data position ( land based radio signals….VOR/DME ) versus computed position ( GPS )'.

Is this something you would be looking at as a matter of course or only if jamming or spoofing was suspected?
 
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