5 ms·

When I worked at Boeing, I talked about autoland systems with my lead engineer. He said the autoland was too perfect, as the airplanes would touch down at the s

When I worked at Boeing, I talked about autoland systems with my lead engineer. He said the autoland was too perfect, as the airplanes would touch down at the same place every time. This caused that place in the runway to suffer severe fatigue damage.

psunavy03 10mo ago
IIRC, there was a similar problem on aircraft carrier flight decks, where they had to induce some randomized amount of dispersion to keep the tailhook from hitting the same spot over and over again.
- refibrillator 10mo ago
  Hmm in distributed computer systems similar patterns exist, e.g. adding jitter to avoid thundering herd effects. This feels like an essential pattern of the universe or something…
  - HPsquared 10mo ago
    "Spread spectrum" is used in EE to spread out the frequency ranges used and reduce interference. The extreme version being CDMA.
    - username135 10mo ago
      Intriguing
- krisoft 10mo ago
  I work at a self-driving car company and we observed a similar problem when we did some off-road testing on dirt tracks. The cars were too precise and they were cutting deep ruts into the soil. We too solved it by adding a pseudo-random offset to the track.
  - bobthepanda 10mo ago
    Before the current wave of automation there was a previous technology to automate buses using optical sensing and lines in the road which had the same issue.
    - namibj 10mo ago
      If you want rails: build rails.
      - bdamm 10mo ago
        There are entire subway systems built with tire-on-concrete where the trains ride precisely the same routes down to the millimeter. Montreal’s is a famous one. These systems are not as efficient as rail, but they are quieter and gentler than the typical subway.
        namibj 10mo ago
        That's still rail. It's just not steel-on-steel. Otherwise you'd have to seriously limit what systems you call "monorail".
        bobthepanda 9mo ago
        The problem is that the optical guided bus was built with the intention of reducing cost, since painting lines is a lot cheaper than building rails. The moment you have to build rail-like things you lose most of the cost advantages.
  - mikepurvis 10mo ago
    I believe Google Maps adds a bit of a rng in which route it will recommend when two otherwise similar in distance/time. Obviously the traffic input also affects this, but that's a slower feedback mechanism; better to distribute the cars all leaving the airport for downtown across the 2-3 possible routes upfront rather than dumping them all onto route A until it's a jam and then all onto route B until it's a jam, etc.
- cucumber3732842 10mo ago
  Citation please. Doesn't pass the sniff test. I suspect the ocean in its various states provides quite a bit of dispersion. Replacing deck plates on a ship is a normal part of maintenance. I find it very hard to believe they'd induce randomness rather than having just that one plate get a different hardness (I know some people will screech about that but trust me, the warship industry is well practiced at such things).
  - Onavo 10mo ago
    Not sure about the ocean industry but carrier landings have full autoland support for a long time (see e.g. magic carpet).
    - psunavy03 10mo ago
      I wouldn't call it a "long time." MAGIC CARPET per se, especially as a default mode of operation, did not become mainstream until the last 10 years, and that's only for the aircraft that have it.
  - Cerium 10mo ago
    I interpreted the effect here not to be on the deck plates but to be the point of impact between the cable and the hook. Sudden bends in cables can wear them fairly quickly in the immediate vicinity. I'm sure you can extend cable life proportionally to the spread of the loading.
    - cucumber3732842 10mo ago
      That makes far more sense.
  - psunavy03 10mo ago
    Citation is my professional network as a former Naval Flight Officer who flew off aircraft carriers, and it's not the deckplates, it's the nonskid coating that goes on top of them. It's expected to wear and be replaced every so often, but when you have to do it more often than that, it becomes a pain logistically and operationally. And the entire point of the system is to counter the dispersion the ocean provides, much like a Naval Aviator is already required to in order to trap successfully. You are literally flying through a very narrow window that is moving in three dimensions.
- gosub100 10mo ago
  Similar problem with catenary wires on electric trains wearing into the contacts. The wires zigzag to distribute the wear.

psunavy03 10mo ago

IIRC, there was a similar problem on aircraft carrier flight decks, where they had to induce some randomized amount of dispersion to keep the tailhook from hitting the same spot over and over again.

refibrillator 10mo ago
Hmm in distributed computer systems similar patterns exist, e.g. adding jitter to avoid thundering herd effects. This feels like an essential pattern of the universe or something…
- HPsquared 10mo ago
  "Spread spectrum" is used in EE to spread out the frequency ranges used and reduce interference. The extreme version being CDMA.
  - username135 10mo ago
    Intriguing
krisoft 10mo ago
I work at a self-driving car company and we observed a similar problem when we did some off-road testing on dirt tracks. The cars were too precise and they were cutting deep ruts into the soil. We too solved it by adding a pseudo-random offset to the track.
- bobthepanda 10mo ago
  Before the current wave of automation there was a previous technology to automate buses using optical sensing and lines in the road which had the same issue.
  - namibj 10mo ago
    If you want rails: build rails.
    - bdamm 10mo ago
      There are entire subway systems built with tire-on-concrete where the trains ride precisely the same routes down to the millimeter. Montreal’s is a famous one. These systems are not as efficient as rail, but they are quieter and gentler than the typical subway.
      - namibj 10mo ago
        That's still rail. It's just not steel-on-steel. Otherwise you'd have to seriously limit what systems you call "monorail".
      - bobthepanda 9mo ago
        The problem is that the optical guided bus was built with the intention of reducing cost, since painting lines is a lot cheaper than building rails. The moment you have to build rail-like things you lose most of the cost advantages.
- mikepurvis 10mo ago
  I believe Google Maps adds a bit of a rng in which route it will recommend when two otherwise similar in distance/time. Obviously the traffic input also affects this, but that's a slower feedback mechanism; better to distribute the cars all leaving the airport for downtown across the 2-3 possible routes upfront rather than dumping them all onto route A until it's a jam and then all onto route B until it's a jam, etc.
cucumber3732842 10mo ago
Citation please. Doesn't pass the sniff test. I suspect the ocean in its various states provides quite a bit of dispersion. Replacing deck plates on a ship is a normal part of maintenance. I find it very hard to believe they'd induce randomness rather than having just that one plate get a different hardness (I know some people will screech about that but trust me, the warship industry is well practiced at such things).
- Onavo 10mo ago
  Not sure about the ocean industry but carrier landings have full autoland support for a long time (see e.g. magic carpet).
  - psunavy03 10mo ago
    I wouldn't call it a "long time." MAGIC CARPET per se, especially as a default mode of operation, did not become mainstream until the last 10 years, and that's only for the aircraft that have it.
- Cerium 10mo ago
  I interpreted the effect here not to be on the deck plates but to be the point of impact between the cable and the hook. Sudden bends in cables can wear them fairly quickly in the immediate vicinity. I'm sure you can extend cable life proportionally to the spread of the loading.
  - cucumber3732842 10mo ago
    That makes far more sense.
- psunavy03 10mo ago
  Citation is my professional network as a former Naval Flight Officer who flew off aircraft carriers, and it's not the deckplates, it's the nonskid coating that goes on top of them. It's expected to wear and be replaced every so often, but when you have to do it more often than that, it becomes a pain logistically and operationally. And the entire point of the system is to counter the dispersion the ocean provides, much like a Naval Aviator is already required to in order to trap successfully. You are literally flying through a very narrow window that is moving in three dimensions.
gosub100 10mo ago
Similar problem with catenary wires on electric trains wearing into the contacts. The wires zigzag to distribute the wear.