Page 1 of 2 12 LastLast
Results 1 to 35 of 65

Thread: Lion Air 737 crashes

  1. #1
    Join Date
    Jun 2000
    Location
    Douglasville, Ga
    Posts
    5,068

    Default Lion Air 737 crashes

    737 Max, the latest version of the 737
    https://www.bbc.com/news/world-asia-46014463
    Tom

  2. #2
    Join Date
    Jul 2011
    Location
    Isle of Mull, Scotland
    Posts
    3,323

    Default Re: Lion Air 737 crashes

    Pure speculation, and not to be advised, but the pilot radioed technical problem and was turning back, so possibly not a bomb.
    However recovered artefacts seem to show fire damage, so some sort of in-flight fire?
    Hope the accident investigation nails it quickly.

  3. #3
    Join Date
    Jun 2001
    Posts
    28,462

    Default Re: Lion Air 737 crashes

    Established in 1999, Lion Air operates domestic flights as well as international routes to South East Asia, Australia and the Middle East.

    It has had issues of safety and poor management in the past and was banned from flying into European airspace until 2016.

    In 2013, Lion Air flight 904 crashed into the sea on landing at Bali's International Airport. All 108 people on board survived. In 2004, flight 538 from Jakarta crashed and broke up on landing at Solo City, killing 25 people.

    In 2011 and 2012 a number of pilots were found in possession of methamphetamines, in one incident hours before a flight.
    The best statement I've seen from this latest carnage came from a student who lived through it -

    "My generation will not allow this to continue!"

    Remember voting age is 18. Read it and weep reds.

  4. #4
    Join Date
    Jan 2010
    Location
    Northern Europe
    Posts
    9,457

    Default Re: Lion Air 737 crashes

    BBC apparently obtained information from the previous "technical issue", which was an instrument failure, the two sides of the cockpit were getting wrong/different information.
    From the flight data avaliable, might have been an air speed /stall issue. Black boxes will give it up.

  5. #5
    Join Date
    Jun 2000
    Location
    Douglasville, Ga
    Posts
    5,068

  6. #6
    Join Date
    Apr 2012
    Posts
    1,914

    Default Re: Lion Air 737 crashes

    This hits hard. I built part of that aircraft.

  7. #7
    Join Date
    Sep 2004
    Location
    Huntsville, AL
    Posts
    5,428

    Default Re: Lion Air 737 crashes

    Here's another crash attributed to faulty angle of attack sensors.

    https://en.wikipedia.org/wiki/XL_Air...ny_Flight_888T
    Will

  8. #8
    Join Date
    Jul 2013
    Location
    Aquitaine
    Posts
    859

    Default Re: Lion Air 737 crashes

    Most of the posters on the Pprune websit can't figure why they didn't set power and attitude standard settings to base levels, for a gentle climb, that would have eneabled them to find the problem and sort out a cure. The weather was clear, good viz, so they could fly visually.

  9. #9
    Join Date
    Apr 2012
    Posts
    1,914

    Default Re: Lion Air 737 crashes

    Tjese were very experienced pilots as well. I suspect a possible loss of flight control, maybe due to a system failure

  10. #10
    Join Date
    Apr 2012
    Posts
    1,914

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by Andrew2 View Post
    Most of the posters on the Pprune websit can't figure why they didn't set power and attitude standard settings to base levels, for a gentle climb, that would have eneabled them to find the problem and sort out a cure. The weather was clear, good viz, so they could fly visually.
    I recall reading, a pilots first responsibility is to fly the damn plane. That's qhy mechanics arent often pilots.

  11. #11
    Join Date
    Aug 2013
    Location
    S.W. Florida
    Posts
    4,213

    Default Re: Lion Air 737 crashes

    /*
    I hate this kind of crap..... instead of playing CYA with paperwork, they should be fixing the defective machinery.
    */


    FAA Issues Boeing 737 AOA Directive After Lion Air Crash

    The FAA has issued a new airworthiness directive (AD) on the Boeing 737 MAX after Lion Air flight JT610 crash investigators found the aircraft’s angle of attack (AOA) sensors are capable of generating erroneous inputs, potentially making the aircraft difficult for pilots to control.

    A statement and copy of the new directive obtained by Avionics International notes that the agency is issuing an emergency AD requiring a Boeing 737 MAX flight operations manual update. The directive comes a little more than a week after Lion Air pilots operating a 737 MAX 8 lost contact with Soekarno-Hatta’s air traffic control (ATC) and crashed into the Java Sea, north of Indonesia's Java Island.

    After safety officials from Basarnas, Indonesia's national search and rescue agency, retrieved the aircraft’s flight data recorder (FDR), a review of the data by Boeing and Indonesian safety investigators pointed to the plausible cause of the crash. FDR data resulted in investigators determining that if an erroneously high single AOA sensor input is received from the aircraft’s flight control system, there is a potential for the 737 to repeatedly perform nose-down trim commands of its horizontal stabilizer.

    (CONT'D AT LINK)
    FAA Issues Boeing 737 AOA Directive After Lion Air Crash (LINK)


    #include [ std-disclaimer ]

    Hope the voyage is a long one.
    May there be many a summer morning when,
    with what pleasure, what joy,
    you come into harbors seen for the first time...

    Ithaka, by Cavafy
    (Keeley - Sherrard translation)

  12. #12
    Join Date
    Sep 2000
    Location
    Baltimore Maryland
    Posts
    11,358

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by sharpiefan View Post
    /*
    I hate this kind of crap..... instead of playing CYA with paperwork, they should be fixing the defective machinery.
    */




    FAA Issues Boeing 737 AOA Directive After Lion Air Crash (LINK)


    #include [ std-disclaimer ]
    Well, it does make sense to get the word out. I understand the AOA sensors causing auto pilot issues but as it was daylight and they were low enough to have visual references to fly manually? The ADIs still use gyros don't they?
    Ratus ratus bilgeous snipeous!

    You must be the change you wish to see in the world."
    Mahatma Gandhi

  13. #13
    Join Date
    Jul 2002
    Location
    usa
    Posts
    6,519

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by Bob Adams View Post
    Well, it does make sense to get the word out. I understand the AOA sensors causing auto pilot issues but as it was daylight and they were low enough to have visual references to fly manually? The ADIs still use gyros don't they?

    Good questions. Without knowing the facts of this crash, it is possible to have an out of trim condition overpower the elevator authority. It doesn’t matter what your ADI says if you’re unable to control pitch. There are ways to mitigate this, but you need some time to figure it out.
    __________________________________________________ ________________________

  14. #14
    Join Date
    Feb 2014
    Location
    Kitty Hawk, NC
    Posts
    7,341

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by CK 17 View Post
    Good questions. Without knowing the facts of this crash, it is possible to have an out of trim condition overpower the elevator authority. It doesn’t matter what your ADI says if you’re unable to control pitch. There are ways to mitigate this, but you need some time to figure it out.
    The TV news showed how to shut off the automatic controls. Of course, sometimes there is not enough free time to determine what switches to throw.
    Life is complex.

  15. #15
    Join Date
    Aug 2013
    Location
    S.W. Florida
    Posts
    4,213

    Default Re: Lion Air 737 crashes

    "Get the word out", yes, but fix the machine too. The airlines may complain about spending a few bucks to fix each plane, but that's better than losing a plane, a flight crew, and hundreds of passengers.

    They may have changed how the controls work. Used-to-be™ that any positive manual control input (pilot pulling back the yoke, kicking rudder pedals) automatically disengaged the autopilot.

    Hope the voyage is a long one.
    May there be many a summer morning when,
    with what pleasure, what joy,
    you come into harbors seen for the first time...

    Ithaka, by Cavafy
    (Keeley - Sherrard translation)

  16. #16
    Join Date
    Nov 2003
    Location
    Rio de Janeiro, BRAZIL
    Posts
    4,396

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by willmarsh3 View Post
    Here's another crash attributed to faulty angle of attack sensors.

    https://en.wikipedia.org/wiki/XL_Air...ny_Flight_888T
    Similar also to the crash of an Air France Airbus from Rio to Paris; the aircraft was flying through ghastly weather, the pitot-tubes iced up, and an inexperienced captain sitting at the controls - with the autopilot doing the flying - was unable to distinguish if it was nose-up or nose-down.

    A friend of mine at the club - a retired Jumbo captain - commented at the time that Boeing´s aeroplanes have an almanac/table which on entering data such as loading (fuel + payload), time into the flight, throttle position, airspeed etc. they are immediately able to determine their AOA for all practical purposes.

    Airbus is known to be automated up to the eyeballs, and Boeing may be going the same route.

  17. #17
    Join Date
    Aug 2013
    Location
    S.W. Florida
    Posts
    4,213

    Default Re: Lion Air 737 crashes

    Hang a pair of dice from the rear view mirror --if they're tapping the windshield, you're in trouble. It's hard to screw up gravity.

    Hope the voyage is a long one.
    May there be many a summer morning when,
    with what pleasure, what joy,
    you come into harbors seen for the first time...

    Ithaka, by Cavafy
    (Keeley - Sherrard translation)

  18. #18
    Join Date
    Apr 2012
    Posts
    1,914

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by sharpiefan View Post
    Hang a pair of dice from the rear view mirror --if they're tapping the windshield, you're in trouble. It's hard to screw up gravity.
    Now that is funny

  19. #19
    Join Date
    Nov 2003
    Location
    Rio de Janeiro, BRAZIL
    Posts
    4,396

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by sleek View Post
    Now that is funny
    I recall meeting a gentleman in my youth in the UK (mid-late 60´s), who as a humble, young chap unloaded cabbages at Covent Garden in the early 1930´s.

    By the end of WW II he had several aircraft instrument patents to his name following which he inaugurated his own factory in the early 50´s, which went strong till the mid-80´s.

    Funny, yes, but not a joke

  20. #20
    Join Date
    Sep 2000
    Location
    Baltimore Maryland
    Posts
    11,358

    Default Re: Lion Air 737 crashes

    I read an article this morning that indicates this sure isn't your Father's 737. Much more automated flight control systems. The pilots might not have had time to do anything, apparently this flight when from 5,000 feet to termination in one minute. Automation can enhance safety, until it goes wrong.
    Ratus ratus bilgeous snipeous!

    You must be the change you wish to see in the world."
    Mahatma Gandhi

  21. #21
    Join Date
    Apr 2000
    Location
    Barrie, Ontario, Canada
    Posts
    4,855

    Default Re: Lion Air 737 crashes

    In a fly-by-wire system, which this and all Airbus are, you never have manual control at any time. All inputs from the control wheel or stick are simply commands to the flight control computers, which interpret what the pilot wants (hopefully), and then wiggle the ailerons and elevator.

    When you "disengage " the autopilot, you are simply switching to a different command-system. There is no direct physical connection between the wheel and the flight controls. Just a more direct interface via the control wheel or stick.

    The flight control computers have lots of sensors, and internal programming. If there is garbage-in, there could be garbage-out.

    There were dire predictions made in the late '80s when the A-320 was introduced. But overall the safety record is very good.

  22. #22
    Join Date
    Jan 2010
    Location
    Northern Europe
    Posts
    9,457

    Default Re: Lion Air 737 crashes

    I have heard it said that pilots have been pretty much redundant as a means to fly from A to B, but usefull to have onboard if anything happens to the electronics; would appear in this case, it was no help. Hard to imagine that the amount of testing an aircraft goes through before being put into use, and this can happen.....software glitch?

  23. #23
    Join Date
    Jun 2000
    Location
    Douglasville, Ga
    Posts
    5,068

    Default Re: Lion Air 737 crashes

    I've never been a huge fan of all fly by wire technology. It's been quite safe over the years buy you are relying on electronics and I like mechanical backups. The MD-88 can be flown with nearly complete loss of power and hydraulics. Complete manual reversion with tabs to fly your primary flight controls, hydraulic accumulators to keep brake and thrust reversers active with a hydraulic loss. It's old tech and it works but it's heavy. The bottom line is these are very complicated machines and things break. (md-88 stab jackscrew is another example though that was a maintenance issue)

    I'm waiting to see what the final report says on this one but it's possible they were too low to have enough time to realize what was happening and correct. At 5000 ft they are barely off the field and there is a lot going on during that phase. If the stab auto trimmed further than they can correct then they were doomed. If this is an unrecoverable design flaw it needs to grounded until such time as they are fixed. If it's a recoverable event then pilot training need it incorporated to ensure there are aware, similar to training for an engine out during takeoff.

    I make unpopular decisions all the time when it comes to safe aircraft. No one wants to hear the we aren't making a ready time because the plane isn't fixed, but I don't get any pushback on it if it's a safety of flight issue either. I know that isn't the case everywhere, but I'm thankful not to have to work under those conditions.
    Tom

  24. #24
    Join Date
    Aug 2013
    Location
    S.W. Florida
    Posts
    4,213

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by Tom Wilkinson View Post
    I've never been a huge fan of all fly by wire technology. It's been quite safe over the years buy you are relying on electronics and I like mechanical backups. The MD-88 can be flown with nearly complete loss of power and hydraulics. Complete manual reversion with tabs to fly your primary flight controls, hydraulic accumulators to keep brake and thrust reversers active with a hydraulic loss. It's old tech and it works but it's heavy. The bottom line is these are very complicated machines and things break. (md-88 stab jackscrew is another example though that was a maintenance issue)

    I'm waiting to see what the final report says on this one but it's possible they were too low to have enough time to realize what was happening and correct. At 5000 ft they are barely off the field and there is a lot going on during that phase. If the stab auto trimmed further than they can correct then they were doomed. If this is an unrecoverable design flaw it needs to grounded until such time as they are fixed. If it's a recoverable event then pilot training need it incorporated to ensure there are aware, similar to training for an engine out during takeoff.

    I make unpopular decisions all the time when it comes to safe aircraft. No one wants to hear the we aren't making a ready time because the plane isn't fixed, but I don't get any pushback on it if it's a safety of flight issue either. I know that isn't the case everywhere, but I'm thankful not to have to work under those conditions.
    Right On, Brother! If it's not safe, it doesn't fly. Stick to your guns & keep them flying, amigo.

    Reading between the lines, it looks as though a major contributing factor in this accident is going to be poor maintenance.

    JAKARTA — The final moments of Lion Air Flight 610 as it hurtled soon after dawn from a calm Indonesian sky into the waters of the Java Sea would have been terrifying but swift.

    The single-aisle Boeing aircraft, assembled in Washington State and delivered to Lion Air less than three months ago, appears to have plummeted nose-first into the water, its advanced jet engines racing the plane toward the waves at as much as 400 m.p.h. in less than a minute. The aircraft slammed into the sea with such force that some metal fittings aboard were reduced to powder, and the aircraft’s flight data recorder tore loose from its armored box, propelled into the muddy seabed.

    As American and Indonesian investigators puzzle through clues of what went wrong, they are focusing not on a single lapse but on a cascade of troubling issues that ended with the deaths of all 189 people on board.

    That is nearly always the case in plane crashes, in which disaster can rarely be pinned on one factor. While investigators have not yet concluded what caused Flight 610 to plunge into the sea, they know that in the days before the crash the plane had experienced repeated problems in some of the same systems that could have led the aircraft to go into a nose dive.
    At Doomed Flight’s Helm, Pilots May Have Been Overwhelmed in Seconds (LINK)


    #include [ std-disclaimer ]

    Hope the voyage is a long one.
    May there be many a summer morning when,
    with what pleasure, what joy,
    you come into harbors seen for the first time...

    Ithaka, by Cavafy
    (Keeley - Sherrard translation)

  25. #25
    Join Date
    Jun 2001
    Posts
    28,462

    Default Re: Lion Air 737 crashes

    They would have had to recognize that a problem with the readings on the cockpit display was causing the sudden descent. Then, according to the F.A.A., they would have had to grab physical control of the plane.

    That would not have been a simple matter of pushing a button. Instead, pilots said, Captain Suneja could have braced his feet on the dashboard and yanked the yoke, or control wheel, back with all his strength. Or he could have undertaken a four-step process to shut off power to electric motors in the aircraft’s tail that were wrongly causing the plane’s nose to pitch downward.


    A FOUR STEP PROCESS to regain control? You GOTTA be ****ing me!
    The best statement I've seen from this latest carnage came from a student who lived through it -

    "My generation will not allow this to continue!"

    Remember voting age is 18. Read it and weep reds.

  26. #26
    Join Date
    Aug 2013
    Location
    S.W. Florida
    Posts
    4,213

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by John of Phoenix View Post

    {SNIP}

    A FOUR STEP PROCESS to regain control? You GOTTA be ****ing me!
    That was my point about pilot input disengaging autopilot -- pilot input should have priority over machinery, that's why he's there. It's like when Armstrong had to manually control the final descent of the LM Eagle....the computer was taking them toward a field of boulders the size of cars, which would have destroyed the LM, so Neil took control and found a safe place to land.

    Hope the voyage is a long one.
    May there be many a summer morning when,
    with what pleasure, what joy,
    you come into harbors seen for the first time...

    Ithaka, by Cavafy
    (Keeley - Sherrard translation)

  27. #27
    Join Date
    Jun 2000
    Location
    Douglasville, Ga
    Posts
    5,068

    Default Re: Lion Air 737 crashes

    While the autopilot uses stab trim for pitch control, autopilot doesn't have to be engaged for automatic stabilizer movement. It is also used as a stall prevention device.

    It sounds like the aircraft was trying to prevent a stall that wasn't actually happening. I do wonder if the proper AOA checkout was done when the AOA vane was replaced earlier that day (if the reports of that are correct). If it wasn't nulled out properly the plane could very well have been doing what it was told. Garbage in=garbage out. The fact that it happened on takeoff makes me think that's a possibility. We don't fly the max so I'm not sure what the adjustment/test procedure is, but I know on a 737-900 you have to verify what the vane is reading throughout it's travel after changing it.
    Tom

  28. #28
    Join Date
    Jul 2002
    Location
    usa
    Posts
    6,519

    Default Re: Lion Air 737 crashes

    The Airbus has this exact same issue, albeit rarely. If you get an uncommanded pitch down, or if the low speed band on the airspeed indicator rises abruptly while maneuvering towards your actual airspeed, turn off two Air data computers to force the aircraft into direct law. Direct law is flight controls with no protections.

    If you know what the problem is, it’s two buttons. There are 3 ADRs total. It doesn’t really matter which 2 ADRs you turn off. Any 2 will solve the problem and leave you with a set of different ,less serious problems.

    At altitude, no problem. At 5000 feet, you better have your **** together.
    __________________________________________________ ________________________

  29. #29
    Join Date
    Nov 2003
    Location
    Rio de Janeiro, BRAZIL
    Posts
    4,396

    Default Re: Lion Air 737 crashes

    Even UBER has experienced some mishaps during trials with 'cars-with-no-onboard-driver'.

  30. #30
    Join Date
    Apr 2000
    Location
    Barrie, Ontario, Canada
    Posts
    4,855

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by skaraborgcraft View Post
    I have heard it said that pilots have been pretty much redundant as a means to fly from A to B, but usefull to have onboard if anything happens to the electronics; would appear in this case, it was no help. Hard to imagine that the amount of testing an aircraft goes through before being put into use, and this can happen.....software glitch?
    No, that's what people want to believe, because it's comforting, but it's utterly false. The flight management computer in a A330 is basically a 486. Your cellphone has more actual computing power.

    It doesn't take much computing power to run a machine. But it takes a gigantic amount to exercise judgment. It's far simpler and cheaper to use a human brain for decisions, and a computer to monitor systems.

  31. #31
    Join Date
    Aug 2013
    Location
    S.W. Florida
    Posts
    4,213

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by Dave Hadfield View Post

    {SNIP}

    It doesn't take much computing power to run a machine. But it takes a gigantic amount to exercise judgment. It's far simpler and cheaper to use a human brain for decisions, and a computer to monitor systems.
    "Aye, there's the rub." Can you say, 'Information Overload'?



    I still say hang some fuzzy dice from those nifty handles above the ADIs.


    Actually, a small, flexible ball chain hung between the handles would be better. The lowest point of the catenary would tell you if you were in a bank, in what direction, and how much; while fore-and-aft clearance with the windscreen would tell you your noseup/nosedown state. Any pilots want to test this?

    Hope the voyage is a long one.
    May there be many a summer morning when,
    with what pleasure, what joy,
    you come into harbors seen for the first time...

    Ithaka, by Cavafy
    (Keeley - Sherrard translation)

  32. #32
    Join Date
    Jul 2002
    Location
    usa
    Posts
    6,519

    Default Re: Lion Air 737 crashes

    G forces would defeat this. It would be straight up and down in level flight and a coordinationated turn or a pitch up. I’m guessing it would work in a steady un-accelerated climb or descent. Search bob Hoover and ice tea on YouTube. Hell, search fuzzy dice and airplane. Someone’s prolly already tried your idea.
    __________________________________________________ ________________________

  33. #33
    Join Date
    Nov 2001
    Location
    Germany
    Posts
    1,454

    Default Re: Lion Air 737 crashes

    Trim rudder going berserk is part of an old film, check https://www.youtube.com/watch?v=AlDvP_YVz8Q at 1:40:52.

    Even though it is electronics today, the effect just might be similar - retrim on its own until you have no stick travel left to pull up ...

  34. #34
    Join Date
    Aug 2013
    Location
    S.W. Florida
    Posts
    4,213

    Default Re: Lion Air 737 crashes

    Quote Originally Posted by CK 17 View Post
    G forces would defeat this. It would be straight up and down in level flight and a coordinationated turn or a pitch up. I’m guessing it would work in a steady un-accelerated climb or descent. Search bob Hoover and ice tea on YouTube. Hell, search fuzzy dice and airplane. Someone’s prolly already tried your idea.
    I found this:
    Would a plumb bob work on an airplane to determine a level horizon?

    The Atlantic Magazine

    D E C E M B E R 1 9 9 3

    The Turn

    At the very heart of winged flight lies the banked turn, a procedure that by now seems so routine and familiar that airline passengers appreciate neither its elegance and mystery nor its dangerously delusive character. The author, a pilot, takes us up into the subject

    by William Langewiesche

    PEOPLE who distrust the sensations of flight, who balk when an airplane banks and turns, are on to something big. I was reminded of this recently while riding in the back of a United Boeing 737 that was departing from San Francisco. Directly over the Golden Gate we rolled suddenly into a steep turn, dropping the left wing so far below the horizon that it appeared to pivot around the bridge's nearest tower. For a moment we exceeded the airline maximum of a thirty-degree bank, which is aerodynamically unimportant but is imposed for passengers' peace of mind. Sightseeing seemed more important now. Our pilots may have thought we would enjoy a dramatic view of the famous bridge and the city beyond. But as the airplane turned, startled passengers looked away from the windows. A collective gasp rippled through the cabin.

    When the wing dropped, the large, sharp-eyed, and alert man sitting next to me during that steep turn over the Golden Gate said, "Hey!" and grabbed the armrests. Now he rode "above" me in the bank, leaning into the aisle as if he feared toppling into my lap. He need not have worried. If he had dropped his pen, it would have fallen not "down" in the conventional sense -- toward me and the earth -- but rather toward the tilted carpet at his feet. If he had dangled the pen from a string, it would have hung at a ninety-degree angle with respect to the tilted floor.

    A dangled pen is a primitive inclinometer, like a plumb bob or the heel indicator on a sailboat. On land or at sea it will hang toward the center of the planet. But in flight it will hang toward the floor, no matter how steeply the airplane is banked. A carpenter's level would be equally fooled.

    This peculiar phenomenon is a manifestation of the turn's inherent balance. The earth's gravity acts on an airplane, and of course on objects in an airplane, but so do the forces of inertia, the desire of any mass to keep doing what it has been doing. The neatness of this Newtonian package is beautiful to behold. Bob Hoover, a stunt pilot, mounted a video camera in his cockpit, set an empty glass on the instrument panel, and poured himself a soft drink while flying full rolls.

    Our United pilots seemed inclined to fly the same way. If they had done so, as we passed inverted above the Golden Gate Bridge and saw it hanging from the water, my sharp-eyed neighbor could have watched his pen dangling toward the sky. During the roll the flight attendants could have walked upside down. And some passengers, too busy to look outside, wouldn't even have noticed.

    The human body is another inclinometer. Undisturbed by the view, it sits quietly, dangling toward the tilted floor, churning out memos for the home office. The man next to me was not about to fall into my lap. He could have relaxed, lowered the tray in front of him, and called for a coffee. Unlike a table on a sailboat, an airplane tray requires no gimbals. Flight attendants do not develop sea legs. They brew coffee on a fixed counter, deliver it without worrying about the bank angle, and fill cups to their brims. Full cups make people behave during turns: if they try to hold them level with the earth, the coffee pours out and scalds their thighs. If this is hard to believe, imagine the alternative -- an airplane in which "down" was always toward the ground. Bedlam would break loose in the cabin during turns.

    The increased loading caused by inertia during a well flown turn is felt within the cabin as a peculiar heaviness. Pilots measure it in "Gs," as a multiple of gravity's normal pull. An airplane that banks to thirty degrees creates a loading of 1.15 Gs: the airplane, and everything in it, temporarily weighs 15 percent more than normal.

    Fifteen percent is hardly noticeable. But when the bank grows only a bit steeper, to forty-five degrees, the load increases to 1.4 Gs: people feel pressed into their seats, and they might notice that the wings have flexed upward.

    Technically it is not important. Airplanes are strong. Pilots shrug off two Gs, and may feel comfortable at twice as much. But passengers are unaccustomed to the sensation. As we pivoted over the Golden Gate, I estimated that my neighbor had gained about eighty pounds. Had he dangled his pen toward the tilted floor, it would have pulled on the string with surprising force. This might not have reassured him. But the extra heaviness is a measure of the pilot's success in resisting the spiral dive. If we had felt "normal" during the turn, it could only have meant that the nose was dropping fast toward the water.

    Pilots, too, have relied on pendulums. It is said that an airliner inbound to New York in the 1950s lost all its gyroscopes in heavy weather over Block Island. The captain was a wise old man who had risen with the airlines from the earliest airmail days and was approaching retirement. A lesser pilot might have fallen for the trap of intuition. But the captain simply took out his pocket watch, dangled it from its chain, and began to swing it toward the instrument panel. Flying by the pendulum and the compass, he proceeded the length of Long Island in the clouds. After breaking into the clear near the airport, he landed and wished his passengers a good day.
    Question: There is emphasis on "coordinated turn"; are ailerons, rudder, and elevators interconnected, so that when you start a roll, they work in concert to maintain altitude? I'm thinking about one wingtip dropping, with no other control movements, so that the plane rolls around the long axis.

    Hope the voyage is a long one.
    May there be many a summer morning when,
    with what pleasure, what joy,
    you come into harbors seen for the first time...

    Ithaka, by Cavafy
    (Keeley - Sherrard translation)

  35. #35
    Join Date
    Jun 2000
    Location
    Douglasville, Ga
    Posts
    5,068

    Default

    Quote Originally Posted by sharpiefan View Post
    I found this:





    Question: There is emphasis on "coordinated turn"; are ailerons, rudder, and elevators interconnected, so that when you start a roll, they work in concert to maintain altitude? I'm thinking about one wingtip dropping, with no other control movements, so that the plane rolls around the long axis.


    They are not interconnected.


    Sent from my iPhone using Tapatalk
    Tom

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •