4 ms·

Could you explain to a layman like me the interesting parts?

by bcyn 8y ago

jen729w 8y ago
Check the 'detailed track log' - you have to click to show it on mobile - for the altitude & speed graphs. A normal flight (https://flightaware.com/live/flight/QFA804 https://flightaware.com/live/flight/QFA804) goes up smoothly. This one very much does not, and the patterns shown bear a resemblance to a layman like me to the published flight patterns of the Lion Air flight. Note the very steep climb on this flight also. Who knows what that means. People who know way more than I do, please step in!
- nawtacawp 8y ago
  Perhaps the steep climb has to do with how the incident airports were setup? “Data released by the Sweden-based service suggested the aircraft had climbed almost 1,000 feet after taking off from Addis Ababa, a hot and high-altitude airport whose thinner air requires extra effort from an aircraft's engines.” https://af.reuters.com/article/worldNews/idAFKBN1QR07Z https://af.reuters.com/article/worldNews/idAFKBN1QR07Z
  - bshipp 8y ago
    Extra effort from the engines? That sounds a little silly, like they just need to be motivated to work a little harder. Take-off power is take-off power. Reduced air density just means the engines don't produce as much power and the wings don't generate as much lift; a double-whammy of lower available engine thrust and greater speed required for the same takeoff roll.
    - DuskStar 8y ago
      > Take-off power is take-off power. I don't think it is anymore - not with noise abatement rules. You can take off in X meters with 100% throttle, or 2X with 80% - but the runway is 4X meters, so you takeoff with reduced throttle to make things quieter for the neighbors.
      - chopin 8y ago
        I don't know whether there are really regulations for that but as a pilot (which I am not) I would not want this as this would lower the decision velocity (I think it's v2) after which the start can't be aborted.
- samstave 8y ago
  I would assume they were testing flight overide logic... which takes some balls...
  - yjftsjthsd-h 8y ago
    Yeah, I can hardly imagine being the crazy/gutsy person actually doing a test of failure modes on a plane in the air. I mean, what exactly are your options if it goes wrong? Maybe you can parachute, but seems like a long shot given altitude and the plane itself (just aim it at an uninhabited area before you jump?) I'm just... gonna go back to my office job, I think.
    - samstave 8y ago
      Dont be so hard on yourself, office jobs crash and burn at a much higher rate.
    - dentemple 8y ago
      I suppose if the hazard pay is enough to set my family up for life...
      - yjftsjthsd-h 8y ago
        There is literally no amount of money that compensates for an absent parent. YMMV, of course, and the calculus is different if you're single or something.
        dsfyu404ed 8y ago
        That's like saying money can't buy happiness. Technically it's true but money can buy you things that make the difference imperceptible.
    - bwilliams18 8y ago
      The type of error that this appears to be is solved if you know what it is, you can just turn the MCAS system off and hand-trim the plane no problem. So testing the failure at a high altitude is of a relatively low risk, you've specifically briefed and likely practiced in a simulator exactly how to turn these systems off. The pilot not flying the plane almost certainly has their hands right on the switches and or fuses.
- hindsightbias 8y ago
  If a test aircraft, it is probably very light, Boeing Field is probably under noise abatement procedures and they might just be optimizing for minimal flight time to get to test altitude. Would have to compare to normal test/aircraft checkout flights and not airline tracks. But no doubt they would be flight testing the reputed MCAS changes at this time so it’s a reasonable guess.
- AlexAltea 8y ago
  The apparent difference in steepness arises from different scaling in both altitude ("typical flight" reaches almost 12 km, while "test flight" reaches almost 6 km) and time (the 5 minute intervals are twice as large in the "typical flight" graph). The actual time to reach 6 km was around 6.5 minutes in the "typical flight" and around 5 minutes in the "test flight", as can be seen by scaling both graphs to the same proportions. (I've done it quickly with Paint here: https://i.imgur.com/IZyYoCl.png https://i.imgur.com/IZyYoCl.png) Is that 1.5 minute difference really that high? Honest question, I really don't know anything about this topic. EDIT: Sorry, this should have been a reply to @rkagerer's comment.
snek 8y ago
It has some interesting dips that seem to be testing some form of sudden dip in altitude which could be seen as related to the system under scrutiny, a safety system designed to prevent stalls which could in some cases "send the plane into a fatal descent if the altitude and angle information being fed into the computer system is incorrect" (not that any of this confirms that the MAX has issues or this is what they were actually testing)
rkagerer 8y ago
Illustrating the answers from snek and jen729w to help clarify: https://i.imgur.com/p8uEwMh.png https://i.imgur.com/p8uEwMh.png

Could you explain to a layman like me the interesting parts?

by bcyn 8y ago

Could you explain to a layman like me the interesting parts?

Check the 'detailed track log' - you have to click to show it on mobile - for the altitude & speed graphs. A normal flight (https://flightaware.com/live/flight/QFA804 https://flightaware.com/live/flight/QFA804) goes up smoothly. This one very much does not, and the patterns shown bear a resemblance to a layman like me to the published flight patterns of the Lion Air flight. Note the very steep climb on this flight also. Who knows what that means. People who know way more than I do, please step in!

nawtacawp 8y ago
Perhaps the steep climb has to do with how the incident airports were setup? “Data released by the Sweden-based service suggested the aircraft had climbed almost 1,000 feet after taking off from Addis Ababa, a hot and high-altitude airport whose thinner air requires extra effort from an aircraft's engines.” https://af.reuters.com/article/worldNews/idAFKBN1QR07Z https://af.reuters.com/article/worldNews/idAFKBN1QR07Z
- bshipp 8y ago
  Extra effort from the engines? That sounds a little silly, like they just need to be motivated to work a little harder. Take-off power is take-off power. Reduced air density just means the engines don't produce as much power and the wings don't generate as much lift; a double-whammy of lower available engine thrust and greater speed required for the same takeoff roll.
  - DuskStar 8y ago
    > Take-off power is take-off power. I don't think it is anymore - not with noise abatement rules. You can take off in X meters with 100% throttle, or 2X with 80% - but the runway is 4X meters, so you takeoff with reduced throttle to make things quieter for the neighbors.
    - chopin 8y ago
      I don't know whether there are really regulations for that but as a pilot (which I am not) I would not want this as this would lower the decision velocity (I think it's v2) after which the start can't be aborted.
samstave 8y ago
I would assume they were testing flight overide logic... which takes some balls...
- yjftsjthsd-h 8y ago
  Yeah, I can hardly imagine being the crazy/gutsy person actually doing a test of failure modes on a plane in the air. I mean, what exactly are your options if it goes wrong? Maybe you can parachute, but seems like a long shot given altitude and the plane itself (just aim it at an uninhabited area before you jump?) I'm just... gonna go back to my office job, I think.
  - samstave 8y ago
    Dont be so hard on yourself, office jobs crash and burn at a much higher rate.
  - dentemple 8y ago
    I suppose if the hazard pay is enough to set my family up for life...
    - yjftsjthsd-h 8y ago
      There is literally no amount of money that compensates for an absent parent. YMMV, of course, and the calculus is different if you're single or something.
      - dsfyu404ed 8y ago
        That's like saying money can't buy happiness. Technically it's true but money can buy you things that make the difference imperceptible.
  - bwilliams18 8y ago
    The type of error that this appears to be is solved if you know what it is, you can just turn the MCAS system off and hand-trim the plane no problem. So testing the failure at a high altitude is of a relatively low risk, you've specifically briefed and likely practiced in a simulator exactly how to turn these systems off. The pilot not flying the plane almost certainly has their hands right on the switches and or fuses.
hindsightbias 8y ago
If a test aircraft, it is probably very light, Boeing Field is probably under noise abatement procedures and they might just be optimizing for minimal flight time to get to test altitude. Would have to compare to normal test/aircraft checkout flights and not airline tracks. But no doubt they would be flight testing the reputed MCAS changes at this time so it’s a reasonable guess.
AlexAltea 8y ago
The apparent difference in steepness arises from different scaling in both altitude ("typical flight" reaches almost 12 km, while "test flight" reaches almost 6 km) and time (the 5 minute intervals are twice as large in the "typical flight" graph). The actual time to reach 6 km was around 6.5 minutes in the "typical flight" and around 5 minutes in the "test flight", as can be seen by scaling both graphs to the same proportions. (I've done it quickly with Paint here: https://i.imgur.com/IZyYoCl.png https://i.imgur.com/IZyYoCl.png) Is that 1.5 minute difference really that high? Honest question, I really don't know anything about this topic. EDIT: Sorry, this should have been a reply to @rkagerer's comment.

snek 8y ago

It has some interesting dips that seem to be testing some form of sudden dip in altitude which could be seen as related to the system under scrutiny, a safety system designed to prevent stalls which could in some cases "send the plane into a fatal descent if the altitude and angle information being fed into the computer system is incorrect" (not that any of this confirms that the MAX has issues or this is what they were actually testing)

rkagerer 8y ago

Illustrating the answers from snek and jen729w to help clarify: https://i.imgur.com/p8uEwMh.png https://i.imgur.com/p8uEwMh.png