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Joined 3 years ago
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Cake day: June 14th, 2023

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  • It’s not just AI, but new android phones drive me spare.

    You can’t disable that. You can’t uninstall that. You can’t make a backup of the whole phone. You can’t make a backup of one app and restore it to a different phone, unless you go through Google. We’re going to install these apps you don’t want, and there’s no way to cancel it.






  • Paris’s RER A is an extreme example, with 10-car double-deck trains moving 2,600 people, ~30 trains per hour. More than a million daily journeys.

    The Victoria line is a more frequency-heavy system, with 8-car single deck trains at 1100 passengers at 36tph, or 40k PPHPD.

    Fully underground systems usually have shorter trains due to the constraints and costs of building longer underground platforms.


  • Honestly you’re in the 11-15m range in most cases, because you want lineside equipment (signal cabinets, masts, cable routing etc) and ideally a 4WD path for maintenance access.

    9m is doable but you don’t built an entire system like that unless you really have to. Equally, your roads have hard shoulders and crash barriers.





  • Commercial planes often take off in mild tailwinds; they’re typically certified for 10-15kt of tailwind. It’s sometimes easier for the airport than re-sequencing all the flights especially if it’s only a mild tailwind.

    Florence has hills to one side (the west?) that mean taking off in that direction also carries a performance penalty because you need good engine-out climb rates. So it can be a choice of tailwind or hills.

    It’s all statistics. If you’re never getting surprised by the weather, you are probably leaving money on the table. If it’s happening all the time, you’re selling too many seats.

    It will also depend on how far out the last seat was sold.



  • It’s often not just the heat, but also wind direction both at the airport and enroute. They probably plan for some combination of the three, but not worse case on all at once.

    Headwinds on takeoff mean you can takeoff with more mass. Tailwinds, crosswinds, and higher temperatures mean you can carry less mass.

    Tailwinds enroute mean you get a higher groundspeed for a given airspeed and arrive earlier, having burnt less fuel. If the tailwinds are known before departure, you can carry less fuel (less mass) and thus more payload (passengers).

    There is nothing you can do to ‘prepare’ other than sell fewer tickets (and thus leave the flight unnecessarily empty on days when there isn’t adverse weather) or use a bigger plane that still needs to be lightly loaded.