Environmental News

Discussion in 'Environmental Discussion' started by tochatihu, Oct 22, 2015.

  1. tochatihu

    tochatihu Senior Member

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    Boeing 737 and direct descendants of original airframe are most numerous commercial haulers of 'self-loading freight' ever built. Step nephew is pilot thereof. Until recently I thought this many-ness was entirely a good thing.

    Original -60 year design has had many revisions. Latest, to make it a ~90-ton hauler with better fuel economy, was larger new engines hung further forward of wings. That Max can pull skyward at such an angle that wings stop doing their lifty thing. This aerodynamic instability* was 'patched' by Boeing with software designed to not be noticed by pilots.

    With 1000's of undramatic daily flights within type, one concludes that it works very well. It may be deemed by consensus to not work well enough.

    * aerodynamic instability in military jets and crop dusters is not a bug, it is a feature. It allows great agility. It has not been a design goal for for commercial haulers in general.
     
  2. tochatihu

    tochatihu Senior Member

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    Of 350 737 Max in service, I reckon that 76 are now grounded in this Asian country, along with 2 of Cayman. Other large operators I suppose are having urgent internal discussions.

    Should you, traveler, by fear, nix the Max? Not by my advice, or example.

    ==
    Should you avoid high-speed motorcycle travel, even with helmet and body armor? Oh heck yeah.
     
  3. fuzzy1

    fuzzy1 Senior Member

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    I thought that all of them, including the crashed Lion Air plane, had two such sensors. But the autopilot uses just one at a time.

    I haven't seen discussions about what autopilot (or human pilot) does or should do when then the AOA sensors disagree. But preliminary data from the Lion Air crash clearly showed a sharp disagreement, that disagreement was blatantly visible well before liftoff rotation, and apparently the autopilot was taking its input from the bad sensor, not the good one.
     
  4. tochatihu

    tochatihu Senior Member

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    @603 does not agree with my understanding. As stated, it seems to strongly indict Boeing MCAS software, in a way that would make the AD issued ... well... crap.

    Lion Air also had issues with airspeed sensors. One would need to climb far past me on ladder of knowledge or influence to obtain clarity. Down here as a 'consumer' I just get into the can that's offered. Even so I pay great attention during first 2 minutes of every flight. Good then and one has excellent chance of a happy ending.

    Discounting, of course, pilots being off their game or a random BUK missile launch.

    :eek:
     
  5. tochatihu

    tochatihu Senior Member

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    I've never 'driven' behind AoA sensors. Just a single airspeed (AS) sensor - I'm just an ASEL :)

    On takeoff roll, we junior pilots pay much attention to AS. If it does not indicate as expected, we cancel and taxi back to ramp. I have no expectation (understanding) that AoA sensor would say anything until I'm out of ground effect. Meaning, >10 meters up and in flight phase where I'm all about hard failures -> landing straight ahead (yuck). Soft failures -> climb and circle for MAYDAY landing (very often not yuck).

    If a terminology problem exists, it should be resolved.
     
    #605 tochatihu, Mar 11, 2019
    Last edited: Mar 11, 2019
  6. tochatihu

    tochatihu Senior Member

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    Total orders placed for 737 Max types from Boeing are 5111; far more than 350 already delivered. It is Boeing's responsibility (and to their benefit) to demonstrate that in all flight phases and under any (allowed) maintenance schedule, these types deserve certification that has already been granted. FAA and EASA provide such certifications and it would be surprising if they do not now take a closer look.

    I have found no evidence that any other than (US) Southwest Airlines add a second AOA sensor. I have found nothing about how its information is presented to pilots, nor if its information is used by MCAS.

    Global commercial jet fleet will grow to 29k by 2020:

    • Aircraft fleet - number of airplanes in service 2015 | Statistic

    Of which 737 Max will be many. Letting things stand as they are seems untenable already. If there is another Max lawndart, OMFG.
     
  7. fuzzy1

    fuzzy1 Senior Member

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    I'm remembering seeing the Lion Air flight data recorder data plotted vs flight time, starting before the takeoff roll. Once the plane had some ground speed, one AOA was reading as expected, but the other was indicating a serious nose-up attitude long before liftoff. (The autopilot apparently ignores it during this flight phase.) Thought it was on the Seattle Times, but haven't yet e-located it.

    But Wikipedia has so relevant sentences:
    Lion Air Flight 610 - Wikipedia
    "On 7 November, the NTSC confirmed that there had been problems with Flight 610's angle of attack (AoA) sensors. Thinking that it would fix the problem, the engineers in Bali then replaced one of the aircraft's AoA sensors, but the problem persisted on the penultimate flight, from Denpasar to Jakarta. Just minutes after takeoff, the aircraft abruptly dived. The crew of that flight, however, had managed to control the aircraft and decided to fly at a lower than normal altitude. They then managed to land the aircraft safely and recorded a twenty-degree difference between the readings of the left AoA sensor and the right sensor.[125]"

    Having two AOAs with sharply different readings on the ground during acceleration strongly suggests a software approach to flagging a fault and determining which sensor may be faulty. It ought to be able to determine that when the nosewheel is on the ground, the plant can't have a 20 degree upward pitch.

    Several prior cockpit crews were able to properly, or at least adequately, resolve the problem per their training and manufacturer's procedures. Shut off the autopilot and fly the plane manually. But as a past article pointed out, when the first fault(s) remain unresolved (sensor failure, and possible MCAS design defect) continue unresolved, opportunity for a deadly multi-fault scenario increases very rapidly. In Lion Air's case, the faults continued until they were finally matched up with a crew unable to handle it.
     
  8. fuzzy1

    fuzzy1 Senior Member

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    Maybe this is what you saw? It is new to me. What is unique about Southwest is not the second AOA sensor, but the optional fault indicator light indicating disagreement between the two AOAs.

    "The Lion Air Boeing 737 MAX 8 that crashed shortly after taking off from Jakarta on Oct. 29 activated an automatic trim system resulting from erroneous angle of attack (AOA) information and the pilots were without an optional feature that would have alerted them to the error, ...

    An optional feature that was not installed on Lion Air’s 737 MAX is an alerting mechanism notifying pilots about erroneous AOA readings. Maintaining an angle of attack that preserves lift and avoids stalls is a key flight parameter that pilots learn to monitor in flight training. Lion Air’s managing director confirmed to Reuters that they did not install the feature because it is not mandatory.

    A representative of Southwest Airlines, the world’s largest operator of the Boeing 737, said that its fleet already features an AOA disagree light to identify erroneous inputs. The carrier is working with Boeing to enable the optional indicator on its current and new MAX deliveries as well."
    Lion Air Report Analyzes Pilot Struggle With 737 MAX Trim System - Avionics
     
  9. fuzzy1

    fuzzy1 Senior Member

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    bwilson4web and tochatihu like this.
  10. tochatihu

    tochatihu Senior Member

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    Extremely useful information @609 that is no doubt under study by current crash investigation team. It is subtly tragic to see manual and automatic trim in extended conflict.

    Opinions vary on whether flight-data recorder from current crash will contain recoverable data. Surely there will be excavations. After such an energetic crash, I can't imagine useful forensic evidence from any other squished bits.
     
  11. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Not looking good for Boeing. I see EASA has suspended all Boeing MAX flights in Europe.

    Something was bugging me and I went back to check. I did not ride a MAX 9 last week, it was the tried-and-true 900ER model. It was too dirty to have been a new plane.

    Boeing can't be happy that half of their open-orders revenue is tied to a plane that (now) has the second-worst fatality record after the Concorde.
     
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  12. bisco

    bisco cookie crumbler

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    A report this morning said an eyewitness saw smoke coming out of the tail
     
  13. tochatihu

    tochatihu Senior Member

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    FDR has been recovered. If previous procedures followed, there will be a very early announcement about data integrity. Slower to reveal what it says.

    Several other airlines have grounded their B38M fleets. But oddly enough if you visit

    Aircraft Type ✈ Boeing 737 MAX 8 (twin-jet) (B38M) Aircraft ✈ FlightAware

    Those in flight include several of Chinese airlines (including CCA) which were previously stated to be grounded. A mystery.

    Eyewitness reports on ground include mention of trailing smoke. Also reported for Lion Air crash. Perhaps in neither case are these accurate or material.

    Yes, Boeing stock price is in need of a horizontal stabilizer at this time.
     
  14. bisco

    bisco cookie crumbler

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    boing maybe be head off the slide with misinformation. for all we know, there may be a lithium battery problem.

    we shall see
     
  15. tochatihu

    tochatihu Senior Member

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    First thought you were just clowning around, but maybe there is an issue.

    787 has rechargeable lithium-ion batteries. 737 Max may only have non-rechargeable (primary) lithium batteries. Needs attention perhaps.
     
  16. bisco

    bisco cookie crumbler

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    Tough situation, abundance of caution? Or throw capitalism to the wind?
     
  17. bisco

    bisco cookie crumbler

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    And yes, I am almost always clowning around, can’t help myself.
    Life is too short...:)
     
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  18. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I sure hope they work this one out. Getting to be that the only place you can fly a MAX is from Renton to Renton.

    It's been a long time since I bothered to look up my flight bookings to see which kind they were going to use for my ride, but I caught myself doing that just now. Apparently I just scheduled two more trips on old trusty rusty 1990s-era 737s.
     
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  19. bisco

    bisco cookie crumbler

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    trump orders all 737 max 8 and 9's grounded. must have been pilot error then.
     
  20. tochatihu

    tochatihu Senior Member

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    Stated reasoning for type grounding today (vs. few days ago) is similar flight profiles from two crashes. In some sources this is attributed to satellite data. In others, faintly implied from (second) flight-data recorder. Should get less vague soon.

    With 2/3 of fleet already grounded, many regional air spaces closed to entry, airline unions asking for caution, plus some media fizz, it would have been hard for FAA to continue appearing to be a commercial advocate here.

    So, 737 Max 8 and 9 are parked. They can still be 'repositioned' but no paying passengers. Mystery that flightaware still shows many B38M airborne can only mean airlines have not indicated what equipment they are using as substitutes. Anyway I have no other guess.

    ==
    Earlier 737 types had earlier engines. Front of (fan) nacelle has a flat bottom. I believe all 737s now flying look like that. New engines are larger and more powerful and mounted further forward. Full throttle makes plane pitch up sharply. Thrust 'appeared' at a different place relative to aircraft's center of gravity.

    Software and automatic trimming were to keeping that from bothering pilots. It is (explicitly I believe) promised that software will be further modified and pilots will get more training about it. It new override switches are also deemed necessary, this pause will be longer. One does not just add wiring to a certificated aircraft.

    ==
    There may be no fundamental reason why this type cannot grow to its full ~5000 in service and compete with Airbus for decade or two Unfortunately and in some was similar to 787, Boeing appears to have cut some corners and got caught doing so.
     
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