FlightRadar24 app ADS-B "IN" only displays aircraft if your at an altitude that their receiver can pick up.

All_In

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Good morning...
You probably already know this but for those who do not... Here is the rest of the story:

While flying from San Diego to Spanish Fork Utah in the AG915 Dave Bacon and others were following us using Radar24 ADS-B "IN"display.
He called me several times along the route asking if our ADS-B was working because he can only see us part of the time.
I assured him it was at least when we fly through or land at airports with equipment to read ADS-B and the device is displaying lat/long as usual.
I told him that honestly, I have not researched how ADS-B works.
However each time you call me, Dave, and ask I've been flying lower than the radar can see while climbing over mountains in elsewhere areas.
The symptoms appear to me if a radar does ping not confirm ADS-B equipment it will not display ADS-B "IN".
He asked me but it uses satellites? Maybe it is only to display the "IN"s on the network if a radar confirms it? That's all I've got that match the symptoms.

Then Dave and I flew to Borrego over the mountains and descended down to the desert at about sea level to land.
On the way back Dave check Radar24 and we were not on the map.
We had others in the desert landing at local desert airports announcing in the pattern and I asked Dave can he see any aircraft in the desert that we are hearing there now?
"No" none of us showed up that was down low = under the radar! But aircraft over the altitude of the mountains were being displayed.

That confirmed my theory.

When we landed back at Gillespie and refueled Dave walked over to the avionics repair shop (1st hangar next to the gas dock) and asked why we did not show up on Raday 24.

He confirmed that if a radar in the system does not ping you.

You will not be displayed nor will any other aircraft in your area be seen by you or anyone else.

I'll keep my normal scan for traffic, thank you very much for a false sense of security watching a new screen... part of the time and not the sky.
 
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WaspAir

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I don't think that's correct. My understanding is that air to air direct broadcast to other equipped aircraft still works, even if you are out of ground station contact, so you can "see" each other, but it won't show up on internet tracking sites because neither aircaft is talking to a network-connected receiver.

P.S. If you have gps satellite data for your position, that gets transmitted. Radar is unnecessary for the system to work, and doesn't give gps-level accuracy anyway. There are many more ground stations than radar facilities, all passing network data.
 
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All_In

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I don't think that's correct. My understanding is that air to air direct broadcast to other equipped aircraft still works, even if you are out of ground station contact, so you can "see" each other, but it won't show up on internet tracking sites because neither aircaft is talking to a network-connected receiver.
That sounds like a much better solution, thank you!
We do not have ADS-B "IN" aircraft solution so could only test with Radar24 on a cell phone.
 

All_In

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Will ATC see ADS-B-equipped aircraft at lower altitudes than non-ADS-B-equipped aircraft?​


ADS-B can detect aircraft at lower altitudes than radar in many locations. See our ADS-B airspace and coverage map to identify where ADS-B coverage is around your home airport and where you fly.
 

All_In

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Under ADS-B, will ATC always see me as N12345 even if I am not under VFR flight following or an IFR flight plan?​

ADS-B Out equipment transmits information about the aircraft's location, ground speed and other data once per second. The broadcast includes the aircraft's unique ICAO aircraft address, which for a U.S. registered aircraft is associated with its tail number, and the Mode A code ("squawk" code). The signal also includes the aircraft's flight identification, which for GA aircraft is generally the registration "N" number, or for commercial/government operator's, their call sign or airline flight number. Air traffic controllers can immediately see this information if they desire, however the controller has display options where they can suppress the N-number for VFR aircraft that are not receiving flight following services. Additionally, GA operators that are equipped with UAT transceivers, squawking 1200, and flying below FL180, have the option to select "anonymous mode". This enables the transceiver to broadcast a randomized temporary address, but it disables ATC's ability to provide services. The transceiver reverts back automatically to the assigned ICAO aircraft address when the anonymous mode is turned off.
 

All_In

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More research reveals some helpful information specifically for us?

I operate an amateur-built experimental aircraft. What should I install?​


The ADS-B Out equipment installed in an aircraft must meet the performance requirements of the ADS-B TSOs. A TSO authorization, issued in accordance with 14 CFR 21 subpart O, is not required. However, ADS-B Out systems and equipment installed or used in type-certificated aircraft must have a design approval issued under 14 CFR 21 (or must be installed by field approval, if appropriate).


The performance requirements include those requirements referenced in section 3 of the applicable TSO (UAT or 1090ES), including considerations for design assurance and environmental qualification. Deviations to the requirements can be approved for equipment that does obtain a TSO authorization, as identified in 14 CFR 91.227.


For experimental category aircraft, there is no FAA approval required for the ADS-B Out system installation. Owners of these aircraft may elect to install equipment authorized under a TSO, in accordance with the installation instructions provided by the manufacturer. Alternatively, owners of these aircraft may choose to purchase uncertified equipment. For uncertified equipment, the owner should obtain a statement of compliance from the supplier, along with installation instructions, that identifies that the ADS-B equipment complies with section 3 requirements of the applicable TSO. When installed in accordance with the installation instructions, it will comply with the aircraft requirements of 14 CFR 91.227. The FAA expects manufacturers to perform appropriate engineering efforts to ensure their equipment complies with all requirements of section 3 of the TSO before issuing their statement of compliance, and expects installers to consider the guidance in AC 20-165B when performing the installation.


Owners of experimental aircraft should retain the statement of compliance from the equipment supplier in the aircraft records to assist in resolving in-service issues, should they arise. The FAA monitors compliance to the ADS-B Out requirements, and if the equipment, or an installation, is determined to be non-compliant, the aircraft may not fly in the airspace designated in 14 CFR 91.225 until the equipment or installation is brought into compliance.
 

All_In

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And...

I operate an S-LSA aircraft. What should I install?​

Owners of standard light sport aircraft (LSA) do not need to use certified equipment, but any alteration to install ADS-B must be authorized by the aircraft manufacturer or a person authorized by the FAA (see AC 90-114A). LSA owners may alter their aircraft if they change their airworthiness certificate to an experimental certificate.
 

All_In

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Operation​


Is it true that the flights directed into areas of GPS interference testing that has been announced via a NOTAM or operators that are affected by GPS interference will not be in violation of 14 CFR 91.227?​


There may be times when the GPS position source cannot meet the required technical performance for compliance with 91.227 due to planned GPS interference. In the event of a scheduled interference outage of GPS, the FAA will issue a Notice to Airmen (NOTAM) that identifies the airspace and time periods that may be affected by the interference. The FAA has determined that it would be impractical and not in the public interest to require operators to avoid the affected area based on the chance that an otherwise compliant flight could experience GPS interference. Accordingly, operators should proceed with their intended operation if the only impediment to their operation is possible planned GPS interference.



What happens if there is GPS interference or a GPS outage?​


The FAA uses back-up systems to provide resiliency and guard against GPS interference, spoofing, or degradation. The FAA also monitors for GPS interference at its ADS-B and WAAS reference sites. In the event of GPS failure, interference, or spoofing, the FAA maintains backup terrestrial radar to provide resiliency for the National Airspace System.


There are a number of built-in ADS-B message quality indicators in the aircraft that are constantly checking accuracy and integrity of the position source information.


If operators encounter actual GPS interference during their flight that results in a degradation of ADS-B Out performance, the FAA will not consider these events to constitute noncompliance with 14 CFR 91.227.






What happens if the FAA's ADS-B ground infrastructure goes down? What is the pilot's responsibility if that happens?​


If the FAA's ADS-B ground system service is unavailable at a facility, then air traffic control services are still provided using either backup surveillance or procedural separation.
 

All_In

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PS: You should not rely on FlightRadar24 for showing all aircraft with ADS-B out.

From our tests. For sure FlightRadar24 does not show your position unless your transponder is being pinged by radar.
 
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Sv.grainne

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Lots of stuff but ADS-B is not radar dependent. Unit gathers GPS Position data and transmits that every second. Any ADS-B equipped AC in the vicinity will see and display that data. Very similar to Marine system AIS, also not radar based.

Can't say what to expect from a phone app.
 

Tyger

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ADS-B uses a system of satellites and ground stations. Radar is not part of the equation. The title of this thread is, simply, wrong.
 

All_In

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ADS-B uses a system of satellites and ground stations. Radar is not part of the equation. The title of this thread is, simply, wrong.
Thanks for reminding me of the original title when I assumed they all worked the way FlightRadar24 behaved.

I thought they all used satellites too but in reality, with FlightRadar24 aircraft below radar scan altitudes do not show up.

I'll test more apps and see how I can try out an in-aircraft solution and let you know the reality of those showing up or not too when we fly over the hill.
.
 
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All_In

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Lots of stuff but ADS-B is not radar dependent. Unit gathers GPS Position data and transmits that every second. Any ADS-B equipped AC in the vicinity will see and display that data. Very similar to Marine system AIS, also not radar based.

Can't say what to expect from a phone app.
That is what I thought and expected with Radar24 too until so many friends told us we disappeared on part of the trip to Utah.
 

All_In

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On afterthought. The name itself should have been our first CLUE.
FlightRadar24, not named Flight ADS=B 24.
 
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All_In

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Flightradar24 uses ADS-B as the primary tracking source.
This is a specific warning not to trust Flightradar24 to show you all the traffic all of the time! We have tested it!!!!

Dave Bacon believed it showed all ADS-B traffic and was using it as his primary ADS-B "IN" display in his Vortex.
On the west coast of CA in LA and San Diego, it seems to always display all aircraft.
What we learned from experience with my flight from San Diego to Spanish Fork Utah is that Flightradar24 loses /dropped me off the map every time I fly over or in front of a mountain that blocks the radar signal.
Dave and 3 others lost us =46S on the map as soon as we flew over our 6+K mountains where for 50 years I've lost flight following too when that low.
Dave called me worried that we had crashed.
We showed up again as soon as Plam Springs class B airspace radar pinged my transponder with its radar.
Then lost us again when I descended behind a small hill (1500') blocking Plam Springs radar to land at Twentynine Palms for fuel.
This continued for the entire trip Flightradar24 could see us flying over Las Vegas airspace but lost us when I descended over the first major mountain on the radar shadow side.
A couple of days after I returned I flew with Dave in the AG915 to his dune buggy pad in the desert and we discovered that none of the aircraft flying in the desert shows up on Flightradar24. Until we flew back and gained enough altitude to be seen/pinged from San Diego's class B airspace radars.

Do not trust Flightradar24 to always show you the traffic!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
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All_In

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Dave's and my observations:
Using Flightradar24 if an aircraft's transponder is not being pinged you will not show up or be seen!
 

Mayfield

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This is a specific warning not to trust Flightradar24 to show you all the traffic all of the time! We have tested it!!!!

Do not trust Flightradar24 to always show you the traffic!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Of course not. Use as "ADS-B in" is not even remotely the purpose of the program. Flightradar24 is simply a tracking service.

If you are not in range of a Flightradar24 receiver you get nothing, and your aircraft will not be seen by Flightradar24 users.

From Flightradar24.com:
Flightradar24 has a network of more than 20,000 ADS-B receivers around the world that receive flight information from aircraft with ADS-B transponders and send this information to our servers. Due to the high frequency used (1090 MHz) the coverage from each receiver is limited to about 250-450 km (150-250 miles) in all directions depending on location. The farther away from the receiver an aircraft is flying, the higher it must fly to be covered by the receiver.
 
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