I would like to present my theory of what happened to Flight MH370, using more sound judgement and scientific reasoning. I received my degree in Aerospace Engineering from Iowa State University, where I specialized in Flight Mechanics and Structural Failure and Fatigue. I began my career working at NASA's Johnson Space Center in Houston where I worked in the Flight Design and Dynamics Department for the Mission Operations Directorate. There, I specialized in crew flight procedures, radar, and navigation systems. After NASA, I worked for Boeing on the V-22 flight control system, then later for Motorola specializing in radio frequency communications and how RF signals propagated.
What most likely happened to Flight MH370, was that fatigue cracking occurred on the Boeing 777-200 series aircraft. On July 23, 2012, The FAA published an Airworthiness Directive (AD) (FAA-2012-0149-0004) for Boeing Company Model 777-200, which was prompted by reports of fatigue cracks in the lap joints, and an Airworthiness Directive to detect and correct such fatigue cracking, which could grow large and cause sudden decompression and the inability to sustain limit flight and pressure loads. This AD was updated on April 15, 2013 to include scribe lines where external decals have been applied or removed across lap joints and large cargo door hinges. In addition, on April 2, 2009 the FAA issued an airworthiness directive (AD 2009-02-05) regarding the airplane information management system (AMS) to prevent an unannunciated loss of cabin pressure, which if an undetected loss of pressure event were to cause an unsafe pressure in the cabin, the flight crew could become incapacitated.
The last known position of MH370 was at 1:21 AM at 35,000 feet, roughly 90 miles off the east coast of Malaysia. At around 1:30 a.m., the aircraft's transponder stopped responding. Under the theory that a sudden decompression occurred at that time due to fatigue cracks, the pilot and copilot would have had 15 - 30 seconds of consciousness to quickly address the problem. If they were aware of the decompression through an annunciation loss of cabin pressure, they would have put on their oxygen masks, turned off the autopilot, begin their descent to below 10,000 feet, and head for the nearest landing spot. If they did not place their oxygen masks on first before they began their descent, or if they attempted to troubleshoot the issue before putting on their oxygen masks, they would have lost consciousness before they reached 10,000 feet.
With the plane not on auto-pilot, in a descent with unconscious pilots, one may think the plane would crash, but this is where flight mechanics, aircraft stability and flight controls play a role in what happened to flight MH370. As the plane descended on its own, (without auto-pilot and unconscious pilots) it would continue to pick up speed to a point where the increasing speed creates more and more lift over the wings. When more and more lift is created, this force causes the plane to pitch up. The plane may have descended to 23,000 feet before it began the pitch up maneuver. At that point, the aircraft is pitched up and begins a climb. It will continue to climb until the atmosphere becomes thinner and thinner and less and less lift is produced over the wings. This would typically occur at 45,000 feet. This roller coaster ride would continue between those two altitudes until the aircraft no longer has fuel to power the engines.
This pitching up and climbing and then pitching down and descending, accompanied by speeding up and slowing does is one of the basic flight dynamics modes of aircraft, and is called the phugoid mode. I have to thank Dr. Pearson at Iowa State University for drilling this into me in his flight controls class and Dr. P.J. Herman who taught flight performance where we flew a plane and demonstrated the speed stability of an aircraft by placing it into a phugoid mode.
Few may remember Payne Stewart who died in October 1999 when his plane experienced rapid decompression and his plane continued to fly for almost four hours after a rapid decompression had occurred and the flight crew was incapacitated. Two North Dakota Air National Guard F-16 intercepted the plane and identified that the cockpit window was iced over and there was no movement of the control surfaces of the plane. During the plane's flight, the aircraft's altitude reached a maximum of 48,900 feet. The NTSB added a commentary on the cause of the accident that stated.
Following depressurization, the pilots did not receive supplemental oxygen in sufficient time and/or adequate concentrations to avoid hypoxia and incapacitation. A possible explanation for the failure of the pilots to receive emergency oxygen is that their ability to think and act decisively was impaired because of hypoxia before they could don their oxygen masks. Research has shown that a period of as little as 8 seconds without supplemental oxygen following rapid depressurization to about 30,000 feet may cause a drop in oxygen saturation that can significantly impair cognitive functioning and increase the amount of time to complete complex tasks.While the transponder was shut down at 1:21 AM, this could have been caused by the rapid decompression and an electrical failure, or by the pilot, in a hypoxia state attempting to set the transponder code to 7500 to indicate an emergency, and accidentally turning it off in confusion.
With regards to the Aircraft Communications Addressing and Reporting System (ACARS), most commercial pilots would have no idea how to disable all of the communications systems. More than likely additional structural failures occurred during the 5 - 7 hour flight while the plane was experiencing high stresses as a result of the phugoid mode that the aircraft was experiencing.
The reason the aircraft has not been located using ACARS is because one can only determine the distance the aircraft is away from the satellite based on the communications angle, it does not have enough information to determine the bearing, and thus based on the range of the aircraft, it could have flown north through China, or south in the Indian Sea. Since no radar contact occurred if the plane was on a northerly route, the plane is more than likely took the southerly route, and continued flying until 8:11 am, when the last confirmed ACARS transmission occurred.
According to a map released by Malaysian officials, the aircraft's location was along a constant declination from the ACARS satellite of approximately 40 degrees:
And given the assumption the aircraft would have been spotted by radar along the northerly trajectory, the most probable location is in the south Indian Sea, away from any land or radar.