Tech Thoughts on Flight 370
Tech Thoughts on Flight 370
By Bill Reesler
As one of those rare individuals who has experienced a rapid decompression at altitude (30,000 ft), I have a somewhat different take on the disappearance of Flight 307. As a former crewmember with nearly 7000 flying hours over a span of 20 plus years, I have spent no little time in the air. I also taught aircraft equipment and egress (escape).
The RD (as it's called) left a lasting impression on me, and its cause (a failure in what is known as an "out flow valve") left an indelible marker in my memory. I remember the bang, everything going white (water vapor condensing out of the air) all the cabinet doors blowing open spewing their contents, and the air escaping out of my nose and mouth, and the pressure on my ear drums. Air Force crewmembers are trained for this and must go through altitude decompression training every 5 years. Commercial pilots and other crewmember have no such requirements.
Someone experiencing it for the very first time - despite the academic preparation - would be quite surprised and disorientated, resulting in a delayed reaction. Assuming this was not intentionally done (more on this later). Talking and reading about it, are far different from the real experience.
Before I go further I feel a quick review of a a RD (rapid decompression) is in order. The human span of consciousness' (the time you stay awake) at 30,000 feet is only about 30 to 60 seconds. In this time you must find your oxygen mask, done it in a tightly fitting manner, regain control of the aircraft, and start an emergency decent to 10,000 feet or below. You also start for the nearest usable airfield. This is necessary for a host of reasons, a primary one being the passenger oxygen systems on a 777 have only a 30 minute maximum duration. The crew system, being liquid oxygen will run considerably longer. A triple 7 has the pilots’ oxygen mask and smoke mask combined into one unit that is located in small compartment that must be manually opened. Getting it open and putting one on properly takes some practice.
This brings us to the mystery of Flight 370. As it was about to enter Vietnamese air space, it now appears to have made an abrupt left turn and started a slight "descent." We also now know that the ACARS "ping" system continued functioning for as much as 4 more hours indicating that the engines ran at least this long. The information come from Boeing connected satellites. Unfortunately Malaysian air did not purchase the data package that would have reported now critical information about the flight. The last "official" radio communication was a "good night". However there is a report from another airline pilot in the area who reported hearing "mumbling" in response to his calls to the missing aircraft. He made the calls in response a Vietnamese request for him to attempt contact when flt 370 failed to enter Vietnamese air space as scheduled. He stated that he believed the mumbles were from the copilot. The basis for his making this assertion was not given.
The turn and the descent are consistent with procedures for an RD. The mumbles would be consistent with someone suffering from oxygen deprivation. Did this plane suffer an RD that slowly (or quickly) incapacitated the pilots? Did the autopilot just keep it flying long after the crew and passengers were dead? Was the plane intentionally depressurized (a 2 step process on Triple 7's) by either a mad man or in response to a high jacking? The outflow valves (2) can be manually opened or can fail. Did this happen?
The transponder being turned off is a problem for the aircraft mechanical failure theory. The transponders either failed (not likely on an aircraft that flew for as many as 4 more hours), or were intentionally turned off. Transponders can transmit a high jacking in progress signal. There was no such signal. To avoid such a transmission one would have to carefully turn them off. And their being off did not stop the radar returns to ground radar, but did stop the identification associated with the returns. Some somewhat familiar with the aircraft would probably have to do this. Cockpits are intimidating places for those unfamiliar with them.
It may take years to find out. The Indian Ocean is vast and not heavily used. You can fly hours without seeing or hearing another plane or sighting a ship. The ocean just a vast, featureless plane which I fear has swallowed flight 370.
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