The Case Against the Zoom-Climb of TWA Flight 800
On July 16, 1996, TWA Flight 800 was climbing out of JFK when it experienced an explosion of the center fuel tank at 13,800 feet. Everything forward of the wing was blown away. That much everyone agrees upon. This occurred offshore of Long Island within eyesight of thousands of people. The FBI interviewed about 750 witnesses and about 100 of these witnesses saw a bright streak rising towards TWA800 prior to the explosion. In an effort to explain what these 100 witnesses might have seen, the CIA (an agency not noted for aviation expertise but well noted for cover operations) proposed that after the nose was blown off, the aircraft continued to fly and zoom-climb from 13,800 feet to 17,000 feet trailing flames. This was supposed to be the bright streak seen by the eyewitnesses (never mind that the witnesses saw the streak rising from the surface, not a point two and a half miles in the sky). The CIA passed this conclusion to the FBI. The FBI (another agency not noted for aviation expertise) apparently approved the idea and the CIA then prepared a video animation of its concept. When the FBI withdrew from the accident investigation in November, 1997, James Kallstrom hosted a one-hour prime-time national television show on CNN. The CIA video animation was shown on the show as justification that all of the eyewitnesses were mistaken, that there was no criminal activity, and that therefore the need for the FBI was concluded. One month later, the NTSB held a public hearing for TWA 800 in Baltimore, MD. The NTSB supported the CIA animation with its own similar but modified video animation. The eyewitnesses couldn’t contradict these animations because the NTSB (at the FBI’s request) did not allow a single eyewitness to testify at the public hearing.
The part that aroused my interest in the investigation was the zoom-climb. An aircraft that loses all of the weight forward of the wing is completely out of balance. When that happens, an aircraft will immediately pitch up and stall. I am a former Navy pilot (World War II era), a graduate engineer from USC, a United Airlines pilot from 1953 to 1985, and I spent the last 20 years before retirement as an ALPA safety representative which included participation in several accident investigations. Since retirement, I no longer speak for any of those organizations. Nevertheless, all of my training and experience suggests to me that TWA800 did not continue to fly and zoom-climb as portrayed in the NTSB and CIA animations.
Basically, it is a matter of weight and balance. Pilots may not understand all the intricacies of aircraft design, but they do understand the performance of the finished product. An aircraft must be in balance in order for it to fly. I like to compare an aircraft in flight to a teeter-totter (next page). Normally, the CG (center of gravity) is slightly ahead of the CL (center of lift). The CG is balanced at the other end by a downward force of the horizontal stabilizer. If the aircraft gets too slow and stalls (loss of lift), the CG will pull the nose down like an arrow, the aircraft will pick up speed, and the pilot can recover from the stall. However, it is possible to load the aircraft so that the CG is behind the CL. In that case, the horizontal stabilizer needs to develop upward force in order to keep the aircraft in balance. But this is not desirable because now if the aircraft stalls, the CG will pull the aircraft down tail first, and the pilot cannot recover from the stall. The following graphic shows TWA 800 before and after nose separation.
The tail has a limited amount of up or down force that it can exert. That means that the CG must always stay close to the CL so that it doesn’t exceed the maximum balancing force of the tail. If the CG gets too far from the CL, the tail loses all control.
So there you have it. After nose separation, the only way TWA 800 could have continued to fly and zoom-climb was for the CG to stay inside the yellow box. But by Boeing’s own calculations, the CG didn’t even stay in the same ballpark. We would have had to attach another sheet of graph paper to show the CG’s new position at 494,606 lbs and 57.8 % MAC. The only thing the aircraft could do with the CG at 57.8 % MAC was to immediately pitch up and stall.
Well, I am basically a pilot and I did the rough calculations on the teeter-totter diagram. However, Ed Zehr is an aircraft designer who worked on the X-29 (some of Ed’s work can be found at www.twa800.com). Ed was surprised that our calculations agreed so closely since he had used an iterative procedure using Mathcad. Regrettably, Ed has since passed away.
Darrell Hambley, Senior Principle Engineer at General Dynamics, did another independent evaluation of the zoom-climb. He used a spread-sheet approach with a new position calculated every 25 milliseconds. His results showed that it only took one second for TWA 800 to stall, a half second less than my crude calculation.
Brett Hoffstadt is a former Boeing aeronautical engineer with some experience in computational fluid dynamics. He agrees that the zoom-climb was aerodynamically impossible and he believes that the Boeing data required for a NTSB type simulation is commercially available. Therefore, the NTSB’s claim that its zoom-climb simulation is dependent on proprietary information may be invalid. (The NTSB is hiding behind Boeing and claiming that Boeing won’t let them release the zoom-climb information, even though the NTSB itself has already published the critical Boeing information.)
Furthermore, Jan Roskam, a former Boeing engineer and now a professor at the University of Kansas, has published two volumes titled “Airplane Flight Dynamics” which are considered two of the Bibles of the industry. You could almost build a B747 with all of the information in those two volumes.
Commander William Donaldson devoted the last years of his life to the TWA 800 accident investigation. It was a great loss to all of us when we lost Bill. Fortunately, his work is being carried on by his brother Bob through their website at www.twa800.com. Bill calculated how much the aircraft would have appeared to slow down on radar if the forward velocity had been converted into a zoom-climb (using energy from forward velocity rather than engine power is what distinguishes a zoom-climb). There was no such slowdown. The radar plot is consistent with a free fall trajectory. There was no zoom-climb.
I am deeply grateful to all of these gentlemen. However, I still need assistance to persuade the NTSB to release the zoom-climb information. It is information that the public is entitled to know. Any help will be sincerely appreciated.