6 ms·

The speed unit looks more like knots than mph.

jamesbvaughan 3y ago
Good catch! I'm not very familiar with knots - what specifically makes the speeds here look like knots to you? edit: Updated the article. Thanks!
- KolmogorovComp 3y ago
  Airline planes never use mph but only knots.
  - jamesbvaughan 3y ago
    That makes sense. One reason I think it could be MPH despite that is because some of the other data seems like it's been processed so that it doesn't need to be transformed any further on the client side before using it in the UI, and the UI displays the speed in MPH. If I were still on the flight, I could just compare the numbers in these payloads to the MPH number in the UI and confirm.
    - mulmen 3y ago
      Based on the lat/long of your destination and the coordinates of the plane I believe the distance and speed actually are in miles and mph: https://news.ycombinator.com/item?id=37694487 https://news.ycombinator.com/item?id=37694487
  - capableweb 3y ago
    Well, most airlines. I think both China and Russia already switched to SI units (so km/h), and supposedly ICAO recommends using km/h but there is exception for using knots and there is also no end date to stop using knots, so everyone just continues to use knots.
    - seabass-labrax 3y ago
      It's not that they 'already switched', but rather that early Russian aircraft had used the metric system for instruments and China acquired much of their early aircraft from the USSR. In the West, it was well into the 50s before knots became conventional. Many (but not all) British and American aircraft used miles per hour, and most of non-communist mainland Europe used the metric system. I am not aware of whether there was some agreement to choose knots, but by the 60s almost all western aircraft had instruments in knots and nautical miles.
  - deleted 3y ago
    [deleted]
  - mjpa86 3y ago
    Was on a UK flight last week, was told speed in mph. Pilots etc might use knots but if the data is for passengers, mph is more likely
- hocuspocus 3y ago
  Your ground speed plot hovering around 500 mph would be ~800 km/h which is oddly slow for an airliner, unless you were facing strong headwinds the entire way. The nautical mile is historically the common unit for marine and air navigation.
  - scatters 3y ago
    Clarification: a knot is one nautical mile per hour.
    - JoeAltmaier 3y ago
      Isn't it 1.15mph? https://www.metric-conversions.org/speed/knots-to-miles-per-hour.htm https://www.metric-conversions.org/speed/knots-to-miles-per-...
      - jdsnape 3y ago
        Yes for statute miles, but it is also one nautical mile per hour
      - toyg 3y ago
        nautical mile is 1.15 land mile.
- chx 3y ago
  487 miles per hour would only be 0.63 Mach which is very slow. 487 knots would be 0.73 Mach which is much closer to the rule of thumb 0.78 Mach cruise speed expected. https://krepelka.com/fsweb/learningcenter/aircraft/flightnotesboeing737-800.htm https://krepelka.com/fsweb/learningcenter/aircraft/flightnot... (and yes, it's a simulator but it's still good for real world)
  - mulmen 3y ago
    Mach is a product of altitude and we only have ground speed so we'd need weather information and heading to compare.
- kvmet 3y ago
  Knots are typically used for aviation. Also different planes have their own optimal speeds for efficiency that the airlines aim for so if you know the airframe you can derive what they are most likely targeting. You can also compare the value to the filed flight plan and see if it is similar.
  - dclowd9901 3y ago
    Knots are used for aviation, but this data looks like it's being consumed by the in-flight UI, and most _people_ are not familiar with knots in terms of speed. Indeed, using the UI shows MPH vs. knots. My money is this speed being mph.
- hocuspocus 3y ago
  Sorry it seems I was completely wrong, it's MPH, your ground speed was on the slow end: https://www.flightradar24.com/data/flights/wn2340#322ad9f6 https://www.flightradar24.com/data/flights/wn2340#322ad9f6
jandrese 3y ago
I'm not so sure. The same data packet claims that the flight has 2h 25m of flight time left to cover 1167 miles. That works out to 483 mph, which is pretty close to the stated 487 and might be explained by some padding added to the time to account for taxiing. Unless that 1167 figure is in a different unit it doesn't even come close to working out at 487 knots ground speed.
- deleted 3y ago
  [deleted]
- apendleton 3y ago
  ... I mean, it could be in nautical miles, no?
- mulmen 3y ago
  Coming at this another way: The blog says the destination was Oakland. The Oakland International Airport is at 37°43′17″N 122°13′15″W. The data packet also contains the current lat and long of the flight as 40.201 and -100.755 respectively. Plugging that in to a distance calculator [2] gives 1163 miles, 1010.6 nautical miles, or 1871.6km. So the distance value of 1167 appears to be miles. At 487mph covering 1163 miles would take 2.3963039014 hours or ~2h23m. If the speed is knots then it would be 2.08233112598 hours or ~2h5m at 560.4296mph. So mph makes the most sense given an estimated time of arrival of 2h25m. So I think you are right, the distance appears to be miles and the speed MPH. This makes sense for an in-flight infotainment system on a US domestic flight. The difference between 1167 and 1163 can probably be explained by the fact that the plane is 6.5 miles in the air traveling at 8 miles per minute and we don't know update interval or if the distance is in the air or on the ground. [1]: https://geohack.toolforge.org/geohack.php?pagename=Oakland_International_Airport&params=37_43_17_N_122_13_15_W_type:airport_region:US-CA https://geohack.toolforge.org/geohack.php?pagename=Oakland_I... [2]: https://www.omnicalculator.com/other/latitude-longitude-distance?c=USD&v=coordAngle:0,dmsLat1M:0,dmsLat1S:0,pHLongA:0,dmsLong1M:0,dmsLong1S:0,dmsLat2M:0,dmsLat2S:0,pHLongB:0,dmsLong2M:0,dmsLong2S:0,distPh:0,dLat1:37.721389!deg,dLong1:-122.220833!deg,dLong2:-100.755!deg,dLat2:40.201!deg https://www.omnicalculator.com/other/latitude-longitude-dist...
dclowd9901 3y ago
I don't think so. When you use the portal, it displays speed in MPH -- I highly doubt there's some knots->mph converter in the frontend code.
- mulmen 3y ago
  I have been on (international?) flights where the in-flight display gave me a choice. It may still be done on the backend but doing that kind of conversion in the UI is at least arguable.

Good catch! I'm not very familiar with knots - what specifically makes the speeds here look like knots to you? edit: Updated the article. Thanks!

KolmogorovComp 3y ago
Airline planes never use mph but only knots.
- jamesbvaughan 3y ago
  That makes sense. One reason I think it could be MPH despite that is because some of the other data seems like it's been processed so that it doesn't need to be transformed any further on the client side before using it in the UI, and the UI displays the speed in MPH. If I were still on the flight, I could just compare the numbers in these payloads to the MPH number in the UI and confirm.
  - mulmen 3y ago
    Based on the lat/long of your destination and the coordinates of the plane I believe the distance and speed actually are in miles and mph: https://news.ycombinator.com/item?id=37694487 https://news.ycombinator.com/item?id=37694487
- capableweb 3y ago
  Well, most airlines. I think both China and Russia already switched to SI units (so km/h), and supposedly ICAO recommends using km/h but there is exception for using knots and there is also no end date to stop using knots, so everyone just continues to use knots.
  - seabass-labrax 3y ago
    It's not that they 'already switched', but rather that early Russian aircraft had used the metric system for instruments and China acquired much of their early aircraft from the USSR. In the West, it was well into the 50s before knots became conventional. Many (but not all) British and American aircraft used miles per hour, and most of non-communist mainland Europe used the metric system. I am not aware of whether there was some agreement to choose knots, but by the 60s almost all western aircraft had instruments in knots and nautical miles.
- deleted 3y ago
  [deleted]
- mjpa86 3y ago
  Was on a UK flight last week, was told speed in mph. Pilots etc might use knots but if the data is for passengers, mph is more likely
hocuspocus 3y ago
Your ground speed plot hovering around 500 mph would be ~800 km/h which is oddly slow for an airliner, unless you were facing strong headwinds the entire way. The nautical mile is historically the common unit for marine and air navigation.
- scatters 3y ago
  Clarification: a knot is one nautical mile per hour.
  - JoeAltmaier 3y ago
    Isn't it 1.15mph? https://www.metric-conversions.org/speed/knots-to-miles-per-hour.htm https://www.metric-conversions.org/speed/knots-to-miles-per-...
    - jdsnape 3y ago
      Yes for statute miles, but it is also one nautical mile per hour
    - toyg 3y ago
      nautical mile is 1.15 land mile.
chx 3y ago
487 miles per hour would only be 0.63 Mach which is very slow. 487 knots would be 0.73 Mach which is much closer to the rule of thumb 0.78 Mach cruise speed expected. https://krepelka.com/fsweb/learningcenter/aircraft/flightnotesboeing737-800.htm https://krepelka.com/fsweb/learningcenter/aircraft/flightnot... (and yes, it's a simulator but it's still good for real world)
- mulmen 3y ago
  Mach is a product of altitude and we only have ground speed so we'd need weather information and heading to compare.
kvmet 3y ago
Knots are typically used for aviation. Also different planes have their own optimal speeds for efficiency that the airlines aim for so if you know the airframe you can derive what they are most likely targeting. You can also compare the value to the filed flight plan and see if it is similar.
- dclowd9901 3y ago
  Knots are used for aviation, but this data looks like it's being consumed by the in-flight UI, and most _people_ are not familiar with knots in terms of speed. Indeed, using the UI shows MPH vs. knots. My money is this speed being mph.
hocuspocus 3y ago
Sorry it seems I was completely wrong, it's MPH, your ground speed was on the slow end: https://www.flightradar24.com/data/flights/wn2340#322ad9f6 https://www.flightradar24.com/data/flights/wn2340#322ad9f6

jandrese 3y ago

I'm not so sure. The same data packet claims that the flight has 2h 25m of flight time left to cover 1167 miles. That works out to 483 mph, which is pretty close to the stated 487 and might be explained by some padding added to the time to account for taxiing. Unless that 1167 figure is in a different unit it doesn't even come close to working out at 487 knots ground speed.

deleted 3y ago
[deleted]
apendleton 3y ago
... I mean, it could be in nautical miles, no?
mulmen 3y ago
Coming at this another way: The blog says the destination was Oakland. The Oakland International Airport is at 37°43′17″N 122°13′15″W. The data packet also contains the current lat and long of the flight as 40.201 and -100.755 respectively. Plugging that in to a distance calculator [2] gives 1163 miles, 1010.6 nautical miles, or 1871.6km. So the distance value of 1167 appears to be miles. At 487mph covering 1163 miles would take 2.3963039014 hours or ~2h23m. If the speed is knots then it would be 2.08233112598 hours or ~2h5m at 560.4296mph. So mph makes the most sense given an estimated time of arrival of 2h25m. So I think you are right, the distance appears to be miles and the speed MPH. This makes sense for an in-flight infotainment system on a US domestic flight. The difference between 1167 and 1163 can probably be explained by the fact that the plane is 6.5 miles in the air traveling at 8 miles per minute and we don't know update interval or if the distance is in the air or on the ground. [1]: https://geohack.toolforge.org/geohack.php?pagename=Oakland_International_Airport&params=37_43_17_N_122_13_15_W_type:airport_region:US-CA https://geohack.toolforge.org/geohack.php?pagename=Oakland_I... [2]: https://www.omnicalculator.com/other/latitude-longitude-distance?c=USD&v=coordAngle:0,dmsLat1M:0,dmsLat1S:0,pHLongA:0,dmsLong1M:0,dmsLong1S:0,dmsLat2M:0,dmsLat2S:0,pHLongB:0,dmsLong2M:0,dmsLong2S:0,distPh:0,dLat1:37.721389!deg,dLong1:-122.220833!deg,dLong2:-100.755!deg,dLat2:40.201!deg https://www.omnicalculator.com/other/latitude-longitude-dist...

dclowd9901 3y ago

I don't think so. When you use the portal, it displays speed in MPH -- I highly doubt there's some knots->mph converter in the frontend code.

mulmen 3y ago
I have been on (international?) flights where the in-flight display gave me a choice. It may still be done on the backend but doing that kind of conversion in the UI is at least arguable.