archive-com.com » COM » T » TWA800.COM

Total: 669

Choose link from "Titles, links and description words view":

Or switch to "Titles and links view".
  • ap-11-24-00
    Young said the company is happy to support the 1 5 million monument planned by The Families of TWA Flight 800 Association We are deeply touched by their experience Young said They are good people brought together in a terrible situation John Seaman of Clifton Park N Y who lost a niece in the crash and heads the association said the contribution was key because it boosted fund raising efforts to 900 000 enough money to begin construction The project which entails a large curved piece of black granite engraved with the victims names on one side and 230 doves facing the ocean is slated for completion by 2001 in time to mark the crash s five year anniversary But Seaman who lobbied TWA for a contribution is disappointed that the St Louis based airline declined They value their dollars more than their integrity he said The airline and its insurance carrier have spent 13 million on funerals memorial services burials and travel arrangements for grieving families said TWA spokesman Mark Abels As time has gone on we have found it increasingly difficult to support group activities simply because the interests of the families differ and what comforts some invariably

    Original URL path: http://twa800.com/news/ap-11-24-00.htm (2016-02-13)
    Open archived version from archive


  • zehr
    calculation although I did use it to determine the original static margin Why because it contributes only about 5 percent as much moment as does the pitch damping not enough to justify calculating alpha the angle of attack I have also left out another coefficient that is even more significant I will leave its identification as an exercise for the Usenet engineering staff One of these worthies went so far as to suggest that I did not understand the significance of aircraft stability derivatives Very well let s see how much HE really knows about this subject But doesn t that mean that I am cooking the figures One Usenet expert has accused me of plugging in numbers contrived to give the answer which I had already decided upon before setting pencil to paper If this person had any grasp of the fundamentals involved he would realize how utterly laughable this notion really is In every instance where a judgement call is required I have leaned so far to err on the side of conservatism as to virtually give away the store For example I arbitrarily cut the first estimate of cg shift in half I have also disdained to include the effect of the increasing angle of attack upon the lift force This is by no means a trivial consideration as can be realized with a bit of reflection upon the significance of the lift curve stall Lift Coef C L C L0 3 10 or 12 angle of attack deg If the angle of attack was initially 3 degrees as indicated by the FDR data only about a third of the lift curve was being used Thus by the time the aircraft stalled the lift would have greatly increased We can estimate how much from the following relationship L C C alpha cuebar S L0 L alpha Where L is the lift force in lbs cuebar is dynamic pressure 202 lbs sq ft S is the wing area 5500 sq ft alpha is angle of attack in radians C the lift curve slope 4 4 L alpha C the value of the lift coefficient at zero alpha 21 L0 Yes I know I ve left out a few things such as elevator deflection which was quite small on the FDR tape and the incidence angle of the horizontal tail Anyone who feels that such things are important in a rough approximation such as this should feel free to calculate them Plugging the numbers for an AOA of 3 deg X pi 180 L 489 600 lbs This may be a tad low but nothing to lose sleep over my original estimate of a c weight was 500 000 lb Doing the same calculation for an AOA of 10 deg that is 175 radians L 1 087 000 lbs In other words the lift which is driving the pitchup would have just about doubled by the time the aircraft had stalled How does this stack up against the diminution of pitching moment due to aerodynamic forces acting on the airframe The pitching moment is given below for the first three seconds t sec M ft lbs 0 7 000 000 1 4 850 000 2 3 230 000 3 2 150 000 The significant thing here is that in two seconds the pitching moment has been reduced to about half its initial value unless one takes into account the fact that the lift which generated the 7 million ft lb moment due to the static instability of the aircraft or what was left of it has roughly doubled in the same time frame Do you begin to see why I felt comfortable about not including aerodynamic pitch damping in my initial calculation In the first place the additional aero moment is more or less balanced by the increase in pitch moment due to the effect of increasing AOA upon lift And in the second place it wouldn t make much difference even if it weren t A pitchup is an extremely violent maneuver which occurs when the angle of attack is driven completely out of control We can assume that this happened with TWA 800 since pilot co pilot and autopilot had all punched out at the time the forward fuselage separated from the rest of the aircraft There was nobody home to look after the AOA The fanciful notion promoted by the FBI those noted aerodynamics experts that TWA 800 bobbed around for almost half a minute like a punctured blimp or went zooming off into the wild blue yonder sans 40 percent of its fuselage trailing fuel in a neat little stream appearing to ground observers like a rocket in flight is exactly what it appears to be a cartoon phantasy best relegated to the Saturday morning tv ghetto for kiddie viewing I have yet to see a single credible technical argument supporting the official version of what is supposed to have happened to TWA 800 after the nose fell off Instead those of us who question the official nonsense put out by the FBI and the NTSB have been showered with personal abuse accused of technical incompetence by immature tyros who lack the guts to show us the basis of their own reasoning if any and haughtily dismissed by make believe experts who utterly lack even a rudimentary understanding of flight dynamics To those who would nit pick this addendum to my earlier calculation I have this to say the price of admission is a basic understanding of what this problem is all about Anyone who has some familiarity with the aircraft equations of motion should know which term I left out of the pitch damping relationship this is elementary really I ll even drop a clue as to where to look try the short period approximation The other thing to remember is that a technical discussion has many of the aspects of an intelligence test To respond to reasoned arguments with verbal abuse is suggestive of a room temperature IQ EZ REFERENCES 1 Roskam Jan Airplane Flight Dynamics and Automatic Flight Controls Part I The University of Kansas Lawrence Kansas 1982 2 Brockhaus Rudolph Flugregelung I Das Flugzeug als Regelstrecke Oldenberg Verlag Muenchen Wien 1977 Date Tue 20 Jan 1998 09 53 04 0500 From Edward W Zehr ezehr CapAccess org To cas majordomo pobox com Subject CAS TWA 800 The Simulation TWA 800 PITCHUP THE SIMULATION A while back HSprunt suggested that a simulation would be the best way to determine the validity of the FBI CIA cartoon production of the rise and fall of TWA 800 I scoffed at this notion at the time the idea of simulating an airplane even as it falls apart in the sky did not appeal to me at that point Also the nature of simulations tends to obscure what is going on Simulations are made up of closed loops the calculations go round and round and they come out here The problem is if you rush off to do a simulation without attempting to weigh off the various factors involved in advance you will wind up without a hope or a clue as to what happened and how all those enigmatic results came to be Now it occurred to me early on that a useable answer could be obtained from a 2 degree of freedom simulation known in the trade as the short period approximation piece of cake really but cunning devil that I am I didn t let on I thought it better to lead the reader through the exercise of estimating the time required to stall the aircraft after 38 percent of the forward fuselage had fallen off That way the simulation results could be interpreted in the light of basic physical principles rather than being taken on blind faith The preliminary investigation builds confidence in the final result Having satisfied myself that the estimates I had made were well within the ballpark even if perhaps slightly skewed towards left field I then proceeded to set up a 2 DOF simulation It is a mere bagatelle really taking up less than two pages when implemented in MathCad The signal flow graph shown below gives the essential details Zde U de q 1 s q 1 a 1 s a Mde Mq Za U Ma de delta e elevator deflection in radians Mde M delta e pitching moment due to elevator deflection Zde Z delta e normal vertical force due to elevator deflection Za Z alpha normal force due to alpha closely related to C L alpha the lift curve slope Mq pitch damping largely due to horizontal tail Ma pitching moment due to AOA closely related to static stability U longitudinal velocity constant in short period approximation set equal to airspeed in ft sec 1 s Laplace transform notation for an integration Used here in lieu of a snakesign never mind about Laplace transforms they are handy for converting differential equations into algebraic equations but we won t be doing that here q pitch rate in radians sec qdot pitch acceleration a alpha angle of attack adot rate of change of AOA in radians sec Note I have omitted the mystery coefficient from the diagram although I included it in the simulation C mon you Usenet techies you led us to believe that you know something about this stuff Time to show tell The stability derivatives used in this simulation all have dimensions They were calculated from the dimensionless derivatives given in the cited reference After calculating the coefficients setting up the equations of motion and checking the frequency and damping of the short period oscillation against the published values using the data for the low cruise flight condition 673 ft sec airspeed 20 000 ft I input the values I had been using in the rough calculations I had made to estimate the time from fuselage separation to stall I reduced the weight to 500 000 lb Airspeed 380 kts 641 ft sec altitude 13 700 ft wing area 5 500 sq ft mean aerodynamic chord 27 3 ft and Iy 33000000 slug ft sq In order to simulate the static instability caused by separation of the forward fuselage I changed the sign of M alpha and doubled it The rationale for doing this is the way the coefficient may be calculated C SM C where SM x c Ma La Now SM is the static margin which strictly speaking is a dimensionless quantity calculated by dividing the distance between the center of gravity and the center of pressure x by the mean aerodynamic chord c I sometimes refer to x as the static margin but this is probably confusing to those who are familiar with the correct terminology I have estimated the cg shift at 21 feet which is three times the nominal static margin of 7 feet there I go again That means that the SM has shifted from x to 2x That is why I changed the sign of M alpha and doubled it Ma is calculated from the dimensionless coefficient Cma by multiplying it by a constant Although the magnitude of Ma is relatively small the sign change makes the airframe unstable with drastic consequences as we shall see I also reduced the value of lt the distance from the center of pressure of the horizontal tail to the cg from it s nominal value of 98 ft to 77 ft since the cg had shifted aft Because this reduces the control authority of the horizontal tail I reduced the pitch damping coefficient Mq by the ratio 77 98 The pitch damping is mostly provided by the horizontal tail Now in order to get the simulation moving it is necessary to stimulate it with some kind of input else your plots will all be straight horizontal lines So I twanged the airframe with a 0 1 radian about 6 deg elevator impulse lasting 0 1 sec When I set the initial conditions to 3 6 degrees of pitch and 3 degrees of AOA as shown on the FDR tape the aircraft stalled in 2 sec Observe that in the signal flow diagram of the simulation that the AOA is fed back multiplied by the coefficient Za divided by U What this actually represents is the effect that angle of attack is having upon lift or more accurately the component of lift that is normal to the longitudinal axis THAT is why I omitted the initial 3 deg of AOA in my preliminary estimate to allow for the reduction in AOA which I did not calculate in my estimate Why does Za reduce the AOA Because pitch in the nose up direction increases the lift causing the a c to move upward that in turn decreases the AOA Moving downward increases it But there is greater significance in the alpha loop The following diagram shows the relationship among pitch angle AOA and flight path angle x alpha V theta gamma The pitch angle theta is the angle that the longitudinal x axis of the aircraft makes with the horizontal The velocity vector V is inclined to the horizontal at an angle gamma known as the flight path angle Alpha the angle of attack is the angle between the velocity vector and the longitudinal axis of the aircraft Thus alpha theta gamma Observe the summing junction at the front of the alpha loop It tells us that alpha dot Zde U de Za U a q We have set the elevator deflection de to zero so that term disappears Za that is Z alpha times alpha is the normal force that results each time we increase alpha DIVIDED BY the aircraft mass m In other words applying Newtons law it is the normal acceleration Now if we divide normal velocity by airspeed approximated here by U the result is the sine of the flight path angle which for small angles is approximately equal to the angle in radians Since U is held constant we can approximate Za U a gamma dot The rate of change of gamma with respect to time The sign is negative because theta is measured positive upward and Z is measured positive downward And since q is equal to theta dot the pitch rate we can now write alpha dot gamma dot theta dot Run that through the integrator and we will get the exact same expression we read from the diagram Thus the alpha loop is a mechanized version of the defining relationship among pitch attack and flight path angles That is a handy thing to remember The short period approximation should now hold few surprises even for the greenest of newbies The really neat thing about having an aircraft simulation up running is that we are now able to investigate the effect of various factors in a systematic fashion It isn t necessary to know the precise magnitude of the parameter being varied an entire envelope of values can be examined This affords the operator great insight into the effect of the significant variables and can be almost as useful as seeing the effect when the exact values are known Such exercises are known in the trade as sensitivity studies I will start the ball rolling with the following simulation results t sec Cma q deg sec alpha deg theta deg 1 5 3 32 70 13 50 21 79 1 7 2 5 29 11 13 18 22 46 2 0 2 25 03 12 69 23 40 2 6 1 5 21 57 12 64 26 56 4 1 1 17 13 12 28 33 97 What I have done here is vary the static margin to determine the effect this will have upon the time required to stall the aircraft I have taken 12 deg of AOA as the stall limit It is important to determine this since we don t know with any real accuracy just how far aft the cg has shifted The nominal value for Cma is given in the reference as 1 0 That is for the cg 7 feet forward of the center of pressure If we move the cg 14 ft aft of the cp the value of Cma will be 14 7 1 0 2 0 Thus I have moved the cg progressively forward toward the cp starting at 21 ft Cma 3 going to 14 ft Cma 2 and finally to 7 ft Cma 1 The time to stall ranges from 1 5 sec to slightly more than 4 sec But whether it takes the aircraft 2 sec or 4 sec to stall is not so important as the vertical velocity attained in this time And how pray do we determine that Dead easy Since both theta and alpha are provided by our simulation we know the flight path angle gamma But gamma is made up of two components the horizontal and vertical velocity The vertical velocity is determined as w V sin gamma For the nominal 2 sec to stall case gamma 23 4 12 69 10 71 deg The corresponding vertical velocity is w 641 ft sec sin 10 71 119 ft sec theta integration gamma U w dt h 1 Z alpha delay of 1 comp interval The climb calculation was done as shown above Values of theta determined by integrating pitch rate q and alpha generated by the short period approximation were combined to produce the flight path angle which was multiplied by airspeed to obtain the vertical velocity w using the small angle approximation sin gamma gamma in radians The vertical velocity was then integrated to obtain the increase in altitude h t sec gamma deg w ft sec h ft Cma 1 5 8 29 92 7 52 0 3 0 1 7 9 28 103 9 66 0 2 5 2 0 10 71 119 8 89 8 2 0 2 6 13 92 155 8 150 2

    Original URL path: http://twa800.com/news/zehr.htm (2016-02-13)
    Open archived version from archive

  • cnn-12-5-00
    written statement from U S State Department Spokesman Richard Boucher Included in the agreement are surface to air missiles such as the Stingers and SA 128s The agreement is the product of a two year joint effort by the State Department and the Pentagon and marks the first accord to place multilateral controls on the shoulder fired anti aircraft missiles Boucher said the new multilateral controls are similar to those already used in the United States The countries participating in the agreement all belong to the 33 nation Wassenaar Arrangement which comprises most of the world s major arms exporters The group was established by the Clinton administration in 1996 to promote transparency responsibility and restraint in international transfers of conventional arms and sensitive dual use items Countries participating in the new missile agreement will secure guarantees of end users of the weapons from recipient governments as well as assurances of proper security procedures for their handling and storage Boucher said the agreement will make America and the world safer by keeping the missiles out of the hands of terrorists and outlaws and will reduce the threat of illegal black market acquisitions for use against US troops and aircraft and

    Original URL path: http://twa800.com/news/cnn-12-5-00.htm (2016-02-13)
    Open archived version from archive

  • ap-12-18-00
    left at the post the newspaper said At hearings last week on the crash of Alaska Airlines Flight 261 Hall said he believes President elect George W Bush news web sites should not have to wait to choose a new chairman for the agency Hall called the NTSB the eyes and ears of the American taxpayer This is the best job I ever had he said adding he is unsure of what he will do next Formerly counsel to the Senate subcommittee on intergovernmental relations and an aide to the late Sen Al Gore news web sites Sr father of Vice President Al Gore Hall was appointed to the five member board in October 1993 He became chairman the following June He used the position to bring attention to issues ranging from aging wiring in airplanes to child passenger and pipeline safety Hall directed investigations into the 1996 TWA crash off Long Island N Y that killed 230 people and the safety of Boeing 737 rudders an issue that arose from the 1994 crash of USAir Flight 427 in which 132 people died On occasion he has publicly clashed with the Federal Aviation Administration news web sites accusing the agency

    Original URL path: http://twa800.com/news/ap-12-18-00.htm (2016-02-13)
    Open archived version from archive

  • reuters-12-18-00
    or missile could have been the cause The Pittsburgh crash was blamed on a design fault in the rudder after lengthy analysis of hydraulic systems pilot training and performance Improvements in aircraft design have flowed from both investigations Hall a Democrat from Tennessee who ran Vice President Al Gore news web sites s Senate campaigns joined the safety board in 1993 and became chairman in 1994 Recently appointed safety board member Carol Carmody another Democrat is likely to be named by President Clinton news web sites as acting chairman However President elect George W Bush news web sites is expected to nominate someone of his own choice The men and women of the Safety Board serve our nation with dedication and distinction I will miss my association with them Hall said in his resignation letter to Clinton Other major investigations under Hall have included the crash of a Valujet plane into the Florida Everglades in 1996 the collision of an Amtrak train and a commuter train in Maryland in the same year the loss of a plane piloted by John F Kennedy Jr in 1999 and the crash of an EgyptAir jet off the U S East Coast in 1999

    Original URL path: http://twa800.com/news/reuters-12-18-00.htm (2016-02-13)
    Open archived version from archive

  • wp-12-18-00
    a section that presents alternative scenarios the study says it is also possible that globalization could divide the world into haves and have nots fueling frustrated expectations inequities and heightened communal tensions while triggering the spread of organized crime and weapons of mass destruction The networked global economy will be driven by rapid and largely unrestricted flows of information ideas cultural values capital goods and services and people the report concludes In contrast to the Industrial Revolution the process of globalization is more compressed Its evolution will be rocky marked by chronic financial volatility and a widening economic divide Developed in the past 15 months at a series of conferences held by universities corporations and think tanks the report is most provocative in its inclusion of eight significant discontinuities that the experts considered unlikely but possible Among them A de facto geo strategic alliance between China Russia and India to counterbalance U S influence A collapse in the U S European alliance as a result of trade disputes political differences and conflict over how to handle global security issues Formation of an international terrorist coalition with diverse anti Western objectives and access to chemical biological and even nuclear weapons Serious upheaval in the Middle East caused by deteriorating standards of living in major Arab nations and a failure by Israel and the Palestinians to reach a peace accord Far more likely is a cold peace between Israel and a new Palestinian state said the experts who also predict that Japan s economic influence will wane and that Russia will struggle on virtually all fronts as it drifts toward authoritarianism In stark demographic terms the report paints what is in many ways a distressing portrait of planet earth in 2015 with the world s population having surged from 6 1 billion people today to 7 2 billion Ninety five percent of the growth will be in developing nations with nearly all of that occurring in urban areas the report says The population of mega cities larger than 10 million will double to 400 million Divergent demographic trends the globalization of labor markets and political instability and conflict will fuel a dramatic increase in the global movement of people through 2015 the report says Legal and illegal migrants now account for more than 15 percent of the population in more than 50 countries These numbers will grow substantially and will increase social and political tension and perhaps alter national identities even as they contribute to demographic and economic dynamism Food supplies will be adequate to feed the world s population though famine will persist because of politics war and poor distribution systems the report says Energy demands will increase by 50 percent but supplies will be sufficient with 80 percent of the world s oil and 95 percent of its natural gas still in the ground untapped Water supplies will be far more problematic with 3 billion people living in water stressed countries mostly in Africa the Middle East South Asia and

    Original URL path: http://twa800.com/news/wp-12-18-00.htm (2016-02-13)
    Open archived version from archive

  • st-12-18-00
    sources say President Clinton is set to name board member Carol Carmody as vice chairman elevating her to acting chairman when Hall leaves However Carmody is a Democrat and it is considered a certainty that President elect Bush will eventually name a Republican as chairman Hall said last week that his last official act will be to break ground for a new safety training academy at the Loudoun County Va campus of George Washington University which will also be home to the rebuilt hulk of the Trans World Airlines Boeing 747 that crashed into the Atlantic Ocean in 1996 as Flight 800 Hall said he considers the training academy one of his proudest accomplishments TWA Flight 800 was perhaps the most controversial crash investigation in safety board history To this day some groups and individuals say the board s conclusion that a fuel tank explosion brought down the 747 is a smoke screen to cover up a missile attack Board investigators insist there is not a shred of missile evidence Hall s most sweeping change was establishing the Family Affairs Office to care for relatives of crash victims Partly reacting to criticism that family care might detract from the board

    Original URL path: http://twa800.com/news/st-12-18-00.htm (2016-02-13)
    Open archived version from archive

  • radio-12-19-00
    York City s WBAI 99 5 FM Triangulation exercises have placed the origin of the streak at the closest ship to the crash This ship was tracked by radar but never ID d by the FBI Thirty plus other ships have been identified just not this one said former FBI Assistant Director Lewis D Schiliro See http flight800 org nat security htm for details regarding ships near TWA Flight 800

    Original URL path: http://twa800.com/news/radio-12-19-00.htm (2016-02-13)
    Open archived version from archive



  •