5 ms·

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

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