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Title: A Boeing 757 did not hit the Pentagon
Source:
www.scholarsfor911truth.org
URL Source: http://www.scholarsfor911truth.org/ArticlesMeyer3March2006.html
Published: Mar 10, 2006
Author: Michael Meyer, Mechanical Engineer
Post Date: 2006-03-10 13:25:04 by Grumble Jones
Keywords: Pentagon, Boeing
Views: 388
Comments: 17
A Boeing 757 did not hit the Pentagon by Michael Meyer, Mechanical Engineer To the members of the Scientific Panel Investigating Nine-Eleven: I would like to give you my input as to the events on September 11, and why it is a physically provable fact that some of the damage done to the Pentagon could not have occurred from a Boeing 757 impact, and therefore the 9/11 Commission report is not complete and arguably a cover-up. I will not speculate about what may have been covered up, I will only speak from my professional opinion. But I will explain why I do not believe the Pentagon was hit by a Boeing 757. I am a Mechanical Engineer who spent many years in Aerospace, including structural design, and in the design, and use of shaped charge explosives (like those that would be used in missile warheads). The structural design of a large aircraft like a 757 is based around managing the structural loads of a pressurized vessel, the cabin, to near-atmospheric conditions while at the lower pressure region of cruising altitudes, and to handle the structural and aerodynamic loads of the wings, control surfaces, and the fuel load. It is made as light as possible, and is certainly not made to handle impact loads of any kind. If a 757 were to strike a reinforced concrete wall, the energy from the speed and weight of the aircraft will be transferred, in part into the wall, and to the structural failure of the aircraft. It is not too far of an analogy as if you had an empty aluminum can, traveling at high speed hitting a reinforced concrete wall. The aluminum can would crumple (the proper engineering term is buckle) and, depending on the structural integrity of the wall, crack, crumble or fail completely. The wall failure would not be a neat little hole, as the energy of the impact would be spread throughout the wall by the reinforcing steel. This is difficult to model accurately, as any high speed, high energy, impact of a complex structure like an aircraft, into a discontinuous wall with windows etc. is difficult. What is known is that nearly all of the energy from this event would be dissipated in the initial impact, and subsequent buckling of the aircraft. We are lead to believe that not only did the 757 penetrate the outer wall, but continued on to penetrate separate internal walls totaling 9 feet of reinforced concrete. The final breach of concrete was a nearly perfectly cut circular hole (see below) in a reinforced concrete wall, with no subsequent damage to the rest of the wall. (If we are to believe that somehow this aluminum aircraft did in fact reach this sixth final wall.) EXIT HOLE IN PENTAGON RING-C American Airlines Flight 77, a Boeing 757, is alleged to have punched through 6 blast-resistant concrete walls‹a total of nine feet of reinforced concrete‹before exiting through this hole. It is physically impossible for the wall to have failed in a neat clean cut circle, period. When I first saw this hole, a chill went down my spine because I knew it was not possible to have a reinforced concrete wall fail in this manner, it should have caved in, in some fashion. How do you create a nice clean hole in a reinforced concrete wall? with an explosive shaped charge. An explosive shaped charge, or cutting charge is used in various military warhead devices. You design the geometry of the explosive charge so that you create a focused line of energy. You essentially focus nearly all of the explosive energy in what is referred to as a jet. You use this jet to cut and penetrate armor on a tank, or the walls of a bunker. The signature is clear and unmistakable. In a missile, the explosive charge is circular to allow the payload behind the initial shaped charge to enter whatever has been penetrated. I do not know what happened on 9/11, I do not know how politics works in this country, I can not explain why the mainstream media does not report on the problems with the 9/11 Commission. But I am an engineer, and I know what happens in high speed impacts, and how shaped charges are used to "cut" through materials. I have not addressed several other major gaps in the Pentagon/757 incident. The fact that this aircraft somehow ripped several light towers clean out of the ground without any damage to the aircraft (which I also feel is impossible), the fact that the two main engines were never recovered from the wreckage, and the fact that our government has direct video coverage of the flight path, and impact, from at least a gas station and hotel, which they have refused to release. You can call me a "tin hat", crazy, conspiracy theory, etc, but I can say from my expertise that the damage at the Pentagon was not caused by a Boeing 757. Sincerely, Michael Meyer
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#5. To: Grumble Jones (#0)
American Airlines Flight 77, a Boeing 757, is alleged to have punched through 6 blast-resistant concrete walls - a total of nine feet of reinforced concrete -before exiting through this hole. Further, if a mere commercial airliner can penetrate 3-rings, 6 blast resistant walls, 9 feet of reinforced concrete, delivering its entire payload (wings, engines, fuselage, tail and all) inside the building, why so many problems developing bunker buster bombs? Just redeploy some old 727's and use sparks to ignite their center fuel tanks.
So, it came to my attention that the ground effect on Boeing 757s was being debated at: http://www.libertypost.org/cgi-bin/readart.cgi?ArtNum=132408 and I note two issues worth commenting and providing some background. 1) It was argued here Please provide a quote from the report where any individual familiar with Hanjour described him as a competent pilot. "For Hanjour obtaining his pilot's license in three months, see FBI report of investigation, interview of Amro Hassan, Sept. 17, 2001, p. 2. For Hanjour receiving his commercial pilot's license, see FBI report, "Hijackers Timeline," Dec. 5, 2003 (Apr. 15, 1999, entry citing 265A-NY-280350- PX, serial 334)" [excerpted from 911 Commission full report - page 537] It is false to presume that having a "CPL" equates to Hanjour being licensed or skilled to pilot a Boeing 757. A CPL is actually what the FAA terms an "Airman's Certificate" and it merely permits the holder to be compensated for their piloting on a "for hire" basis, even though additional licenses and regulations have to be met to actually engage in "for hire" piloting. A holder of CPL could engage in "for hire" piloting such as "crop dusting", but not fly a Boeing 757 without additional certificates or endorsements. Note the 911 Commission nor the FBI reports did not say that Hanjour in fact received additional certificates, only that he had a CPL. Neither the FBI nor the 911 Commission is imply that by having received a CPL, that Hanjour was able to fly a Boeing 757. To fly a Boeing 757 one must have an "Airline Transport Pilots License" (ATPL) and further have specific ratings for a Boeing 757 and at least 1500 hours flying time in aircraft of a category similar to a B-757 (heavy, multi-engine, jet airliners). Beyond a CPL, the additional certificates, endorsements, and ratings required include: instrument flight, multi-engine, complex aircraft, turbojets, high performance and high altitude, at a minimum. You can for yourself read the related FAA regs click "Web Current FAR by-b) Subpart" and then scroll down to and click Part 61 - CERTIFICATION: PILOTS, FLIGHT INSTRUCTORS, AND GROUND INSTRUCTORS or you can read overviews at: Nor does completing a Boeing 737 simulator course (see page 243 of 911 Commission report) equate to "passing" the course or being sufficiently skilled to pilot a Boeing 757. These are "for fee" paid tuition courses. If one pays the money, one is entitled to attend all sessions through to completion. Nowhere is it alleged that Hanjour had the credentials or training or " license" to actually fly a Boeing 757 under any real-world circumstances. 2) It has been argued repeatedly that "ground effect" is not a factor in the purported flight of Boeing 757 into the Pentagon. An article cited, The Impossibility of Flying Heavy Aircraft Without Training, explains the "ground effect" as an obstacle to be overcome when flying a Boeing 757 in a manner consistent with what the official report declares happened when AA flight 77 (a Boeing 757) flew the last mile into the Pentagon: low enough to clip street light poles, but not so low as to strike the ground and yet impact the Pentagon at the ground floor: I shan57;t get into the aerodynamic impossibility of flying a large commercial jetliner 20 feet above the ground at over 400 MPH. A discussion on ground effect energy, vortex compression, downwash reaction, wake turbulence, and jetblast effects are beyond the scope of this article (the 100,000-lb jetblast alone would have blown whole semi-trucks off the roads. The DVD, 60;Loose Change 51; 1st Edition61; contains an excellent clip of trucks being blown off the end of a runway when a jetliner powers up for take-off.) Let it suffice to say that it is physically impossible to fly a 200,000- lb airliner 20 feet above the ground at 400 MPH. The author, a pilot and aeronautical engineer, challenges any pilot in the world to do so in any large high-speed aircraft that has a relatively low wing-loading (such as a commercial jet). I.e., to fly the craft at 400 MPH, 20 feet above ground in a flat trajectory over a distance of one mile. It has been disputed that "ground effect" is not a problem and further it was argued here that "On a high speed fly by, no matter how low, ground effect will have essentially no effect" which is a link to an article by apparently a small craft pilot, about small craft conditions, not heavy airliners and certainly not aircraft with supercritical wings. Further, that pilot seems to be alone in his thinking as the airline industry and NASA spend a great deal of effort understanding and managing ground effect. Even small craft pilots are inundated with cautionary training about ground effect, especially the false sense of being able to lift off under overloaded conditions, but then cross the end of the runway still unable to climb out of ground effect. Which is why all pilots are concerned about overloading. The extra lift in ground effect at takeoff compensates for the overloading problem which becomes all too evident after the runway ends and they still can't climb - because they're overloaded (duh). Regardless, here then is some background on the "ground effect" as regards Boeing 757s: NASA - Manual Manipulation of Engine Throttles for Emergency Flight Control (see page 22) B-757 Simulations (see page 21) During attempted flaps-up landings the airplane would begin to float at 200 ft above ground level (AGL). Several 700 ft/min glide slopes were flown with no throttle or flight control inputs to study the ground effect model. At 200 kn with no flaps, the airplane leveled off and climbed as it reached 200 ft. With FLAPS 1 at 187 kn, the float began at 50 ft, and at FLAPS 5 at 170 kn, the sink rate went from 700 to 300 ft/min going through 100 ft and stayed there, making a smooth touchdown. It appeared that the no-flaps ground effect model may be in error. Ground effect was a big issue in both the F-15 and MD-11 flight tests. The lift change is important, but the pitching moment change is probably more important, and is often not properly modeled in simulations. Flare and Touchdown (see page 46) For a runway landing, hold the constant approach path to touchdown, reducing thrust only after ground contact or if floating just a few feet above the runway. As ground effect is entered, there may be a pitchdown or pitchup, depending on configuration, airspeed, and flap setting. It may be better to accept a moderate sink rate (50051;600 ft/min) rather than to try to flare and possibly balloon or float in ground effect. Then use reversers if available and wheel brakes if available for directional control and deceleration. With underslung engines, there are two typical but improper pilot responses on a first actual TOC landing. One is to reduce thrust to idle as the runway is approached52;this will increase the sink rate to possibly dangerous levels and may cause a roll input as well if there was any throttle stagger required to hold wings-level. The other reaction is to add thrust just prior to touchdown to reduce the sink rate. A little thrust pulse may be warranted, but if too much, this causes a balloon which may force a go-around. For underslung engines, a go- around after a balloon should still be possible. Flight Safety Digest - Data Show Wake Turbulence Accidents Most Frequent at Low Altitude and During Approach & Landing (see page 21 & table 1) Note under the column headed "height of ground effect aircraft gear & flaps retracted" that a B-757-200 (the model with the wingspan of 124 ft as discussed) enters ground effect at 49 feet. The approach speed used was 150 knots. NTSB AIRCRAFT ACCIDENT REPORT - UA 232 MD DC-10, SIOUX CITY, IOWA JULY 19, 1989 (Appendix D): Aircraft Control with Complete Hydraulic Power Loss (page 124) 1.11 Ground Effect. Before discussing the landing, a review of the phenomenon known as "ground effect" will be useful. As an aircraft comes in close proximity to the ground, a slight increase in lift and decrease in drag occurs at an altitude beginning about 1/2 the wing span. Another tendency in ground effect, generally not as obvious, may be a nose down pitch moment as the aircraft enters ground effect, which is a function of sink rate and configuration. The DC-10 begins to enter ground effect at about 100 feet A.O.L. and the effect increases exponentially as altitude decreases. Without elevators, the only means of controlling the ground effect pitch change is with a sharp power advance followed by a throttle retard. This is a matter of judgement and is mentioned as a necessary step in reducing what could be an excessively high sink rate at touchdown. Obviously, an approach above the glideslope with a rapid sink rate coupled with ground effect could result in a very hard touch down. 1.12 Final Approach. If the final approach is stable from about 500 feet A.G.L., a landing should be attempted, but extreme vigilance is required from all crew members. The pilot may find it useful for the pilot not flying to call radio altitude, sink rate, and sink rate increasing or decreasing trends from the outer marker (or equivalent distance) inbound. As the aircraft nears the runway, sink rate and sink rate trend are sufficient, and in ground effect sink rate trend only. The pilot not flying and the second officer are in a good position to judge pitching tendencies by watching the horizon in relation to the glareshield. This can be critical information when approaching touchdown. Because the ground effect may increase the rate of descent near the ground, it is apparent that the touch down aiming point must be moved to compensate for this tendency. Simulator trials have shown that if the aiming point is moved toward the far end of the runway the touch down will have a better chance of occurring in the normal first third of the runway. In an unstable approach when the aircraft is in a phugoid oscillation, three things can happen: (a) the aircraft can touch down on the pitch down phase of the phugoid, which means a hard impact when coupled with a possible pitch down due to ground effect; (b) the aircraft can enter the pitch up phase of the phugoid during final approach and not touch down at all (in which case a go-around should be attempted); or, (c) it can touch down somewhere in between the two extremes. The likelihood of touching down smoothly is highly unlikely. Consequently, it is recommended to attempt only to reduce the rate of descent before touch down as much as possible. 1.14 Landing. When entering ground effect with the intention of landing, be aware of, and be quick to respond to, the necessity to add power to keep the nose from falling. Remember that the speed at touchdown will be a function of the phase of the phugoid oscillation, and could be well over 200 knots. It is most important to increase thrust, to raise the nose if necessary thereby decreasing the sink rate--even if this results in an increase in touch down speed. Maneuver the power as necessary up to maximum thrust to reduce the sink rate to an acceptable value. 2.6 Preparation for Touchdown. Adjust the touchdown aim point toward the far end of the runway as before, and continue to fly the thrust for speed control and stabilizer trim to maintain the desired pitch attitude/flight path angle. Smooth deliberate throttle adjustments for speed control while far out on the approach will make the task of trimming the stabilizer easier due to the slower than normal rate of trim. Begin the transition from stabilizer trim to thrust for flight path angle control on the final part of the approach (about 500 feet AGL). Aggressive power application (ie rapid accelerations followed by immediate throttle chops) will allow the small changes in pitch attitude necessary to maintain the touchdown aiming point without significantly changing the speed, assuming the approach is stable in the pitch axis. Throttle adjustments may need to be more aggressive as the airplane enters ground effect. Once again, there should be no attempt to accomplish a smooth landing, but simply reduce the sink rate as much as practical without ballooning or skipping. The point of the foregoing is that Boeing 757s in flight configuration with gear up and flaps retracted do in fact experience "ground effect" which is entered anywhere between 50-100 feet and which both lifts the plane and tends to pitch the nose down, but the extent of the pitching moment is highly dependant on aircraft model, configuration, and loading. Further note the variation in response between type of aircraft in ground effect, and that the actual impact of the tendancy for nose pitch down is more significant than the simulator models would indicate and, if I understand correctly, the preferred compensation (assuming working hydraulics) is to raise the nose to increase the angle of attack (but not to the point of stall) which inturn increases drag and decreases lift and also throttle up slightly to compensate for the increased drag, and this is how an airliner normally descends through ground effect to touchdown. To fly a Boeing 757 into the Pentagon at 400 mph in ground effect (low enough to clip light poles) would seem to require a sustained nose-up pitch and some throttle increase over that last mile of approach, and sustaining that attitude (let alone level flight) seems even further beyond the skill of someone who at most paid for and attended 737 simulator training. I'm not aware of any computations that purport to show the ground effect or flight conditions on a B-757 at 400 mph at 20ft AGL. The closest seem to be the NASA simulator studies and the tower fly-by measurements done on B-757s. In his article The Impossibility of Flying Heavy Aircraft Without Training, Nila Sagadevan wrote "I shan57;t get into the aerodynamic impossibility of flying a large commercial jetliner 20 feet above the ground at over 400 MPH". I wish he had. I wish someone would step us all through the science and math of that specific scenario. Perhaps we could get some "heavy" pilots and/or engineers to contribute what really happens to a 757 (ideally with some modelling) during a 400 mph gear & flaps up approach, in ground effect for one mile.
Let me ask valis to weigh in on this..
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Top • Page Up • Full Thread • Page Down • Bottom/LatestWe are lead to believe that not only did the 757 penetrate the outer wall, but continued on to penetrate separate internal walls totaling 9 feet of reinforced concrete. The final breach of concrete was a nearly perfectly cut circular hole (see below) in a reinforced concrete wall, with no subsequent damage to the rest of the wall. (If we are to believe that somehow this aluminum aircraft did in fact reach this sixth final wall.)
#8. To: All, Grumble Jones, Elliot Jackalope, Zipporah, SKYDRIFTER, valis, tom007, FormerLurker, Orangedog, who knows what evil, Neil McIver (#5)
#9. To: Starwind, valis, *9-11* (#8)
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