Non-motoring > Flight radar 24 Miscellaneous
Thread Author: sherlock47 Replies: 10
View Threaded 

New Wed 19 Mar 25 10:41 
 Flight radar 24 - sherlock47
SWMBO came back from Hong Kong last night on Cathay Pacific CX253. I usually track landings on FR24 as it gives a good guide on how much time I have to finish the house cleaning. Scheduled landing 20.10 at LHR. (Maybe I am a frustrated stalker?:)

I know there are several keen aircraft followers here but and would like their comments - normally on the positioning of the aircraft wrt to the runway. Where does the aircraft derive its positioning data from? Normally very accurate. On this occasion it did a go around from what appears to be a very low altitude - probably because the previous landing had not cleared the runway. Her comment was that it did not seem very late or steep. The only late go arounds i have experienced have been very noticeable with increased power and angle of climb!
Reply to this message | Report message
       
New Wed 19 Mar 25 10:59 
 Flight radar 24 - zippy
Aircraft get their positioning data from GPS but there are back up systems including inertia based navigation systems based on solid state gyros because nasty countries like Russia block GPS signals.

(In my banking life, I worked with a company that rented modules / parts to airlines and these were really expensive.)

Flight Radar 24 uses a network of radios that pick up the ADS-B signal that aircraft transmit once per second. The signal includes GPS location, ground speed and altitude.

The radios are operated by volunteers / hobbyists and automatically transmit the data via the Internet to websites like FlightRadar24 and ADSBexchange.com.

Some sections of a flight across large stretches of ocean cannot be tracked using ADS-B by hobbyists because they are not in-range of the radio receivers.
Last edited by: zippy on Wed 19 Mar 25 at 11:00
Reply to this message | Report message
       
New Wed 19 Mar 25 18:29 
 Flight radar 24 - Biggles
There are also a few VOR beacons dotted around for the aircraft to calculate its position using trigonometry.
Reply to this message | Report message
       
New Wed 19 Mar 25 12:02 
 Flight radar 24 - Manatee
Most landings will be manual, using the flight directors would be my assumption. They are effectively following a beam to the runway threshold on the lateral track, and the vertical track is AIUI generated by the aircraft from altitude and distance data which has a GPS component.

The FD bars are displayed on the primary flight display (the artificial horizon thing) and indicate up/down and left/right deviation from the glideslope so the pilot flying can make adjustments.

If by 1000'? AGL the aircraft is not on track and at the right speed in landing configuration then the aircraft will go around. Lower still, there is a decision height at which the runway must be in sight, and if it isn't then a go around is initiated.

A go around can be initiated right down to or even on the runway if there is a problem such as a runway obstruction or an over-long landing.

A GA at 1000' or above should be fairly undramatic but below that and I think you would definitely notice.

TBH I don't know much of the technicalities of this so I may have mixed up a few things.

I've only experienced one, on a flight to Turin (Ryanair) when the visibility was poor in the early morning. They couldn't see the runway in time and the application of power and change of attitude was very evident. There was an announcement that we would have another go and if that didn't work we would go to Genoa. In the event, the second attempt was successful.

Last edited by: Manatee on Wed 19 Mar 25 at 12:04
Reply to this message | Report message
       
New Wed 19 Mar 25 12:11 
 Flight radar 24 - zippy
>>or even on the runway

Yes, but some aircraft have sensors that detect wheels down on the runway and deploy airbrakes.

Stowing airbrakes and re-applying power is not instantaneous and if there is something on the runway the landing plane may not generate enough power to go around, leading to a potential disaster.
Reply to this message | Report message
       
New Wed 19 Mar 25 12:22 
 Flight radar 24 - Manatee
Once reversers are set I think most if not all airlines SOPs forbid a GA. The reversers can be armed such that they deploy when there is weight on wheels. GAs have been attempted in that situation and not always successfully.
Reply to this message | Report message
       
New Wed 19 Mar 25 12:33 
 Flight radar 24 - zippy
>>GAs have been attempted in that situation and not always successfully.

According to Air Accident TV documentaries, this has been the cause of some disasters.
Reply to this message | Report message
       
New Wed 19 Mar 25 12:34 
 Flight radar 24 - Zero
The links and interlocks between, and rules around TOGA and Reversers vary between manufacturers and models
Reply to this message | Report message
       
New Thu 20 Mar 25 08:24 
 Flight radar 24 - sherlock47
Back to the original question...... Flight also known as CPA253

www.flightradar24.com/2025-03-18/19:44/4x/CPA253/398478d5

Having looked at the FR track more closely on a large screen the first approach as far as the reservoirs looks correctly mapped (cf track of other landing aircraft) implying GPS data was accurate for N-S co-ords. At that point there is a discontinuity and adjustment resulting in non alignment with the runway. Approach continues down to 100' before TOGA.

On 2nd approach it looks more controlled and accurate but significant error in E-W co-ords showing an offset to the west. (Based on the the displayed position on map after landing). To me this looks as though switched between GPS and inertial source of data with a resulting FR24 reporting error,

Apologies for probable incorrect terminology but you should get the drift.

What is the definition of a good landing? If everybody walks away.
Last edited by: sherlock47 on Thu 20 Mar 25 at 08:26
Reply to this message | Report message
       
New Thu 20 Mar 25 11:55 
 Flight radar 24 - Manatee
ADSB data are not that accurate. It's possible they were off track but just as possible they weren't.

Lateral track typically wouldn't be from GPS which is part of the vertical track.
Reply to this message | Report message
       
New Wed 19 Mar 25 16:20 
 Flight radar 24 - Bromptonaut
>> Once reversers are set I think most if not all airlines SOPs forbid a GA.
>> The reversers can be armed such that they deploy when there is weight on wheels.
>> GAs have been attempted in that situation and not always successfully.

There was a nasty accident in Canada in the late seventies with a 737 'Jurassic' where that happened.

I'm also sure there was something more recent with an Airbus where circumstance beat the fail safe stuff bit in that case the crew got it on the ground safely at attempt #2.
Reply to this message | Report message
       
Latest Forum Posts