March 10, 2014
What happened to MH370?

Has anyone considered if the below FAA Airworthiness Directive could be a clue the MH370 investigation?

A November 2013 FAA Airworthiness Directive for the 777
SUMMARY: We propose to adopt a new airworthiness directive (AD) for 
certain The Boeing Company Model 777 airplanes. This proposed AD was 
prompted by a report of cracking in the fuselage skin underneath the 
satellite communication (SATCOM) antenna adapter. This proposed AD 
would require repetitive inspections of the visible fuselage skin and 
doubler if installed, for cracking, corrosion, and any indication of 
contact of a certain fastener to a bonding jumper, and repair if 
necessary. We are proposing this AD to detect and correct cracking and 
corrosion in the fuselage skin, which could lead to rapid decompression 
and loss of structural integrity of the airplane.

Update 3/12, 16:43:
[Here was an earlier anonymous tip I received saying that the AD did not apply to MH370].
Update 3/13 0:00:
I got an email from a reporter suggesting that the AD did, in fact apply to MH370.
Update 3/13 2:36: 
Latest statement, straight from a Boeing spokesperson:
The antenna covered by the pending AD was not installed on MH370, so that airplane is not subject to the AD or the related Service Bulletin.

So, it has been determined that the AD was not relevant to this plane. However, it served as the key inspiration for an alternative explanation. 

New Summary:
There’s a chance that MH370 flew for hours on autopilot after we lost radar contact with it. The idea is that some kind of decompression event incapacitated the passengers and crew, while also somehow disabling Satellite and Radar communication systems. 
If such a decompression were caused by a rupture in the skin of the fuselage, there’s a chance satellite and/or radar antennas would have suffered direct physical damage from the blowout. 
Original Summary
When I first wrote this, it seemed likely that a fuselage section near the SATCOM antenna adapter failed, disabling satellite based -  GPS, ACARS, and ADS-B/C - communications, and leading to a slow decompression that left all occupants unconscious. If such decompression left the aircraft intact, then the autopilot would have flown the planned route or otherwise maintained its heading/altitude until fuel exhaustion. 
slow decompression (e.g. from a golfball-sized hole) would have gradually impaired and confused the pilots before cabin altitude (pressure) warnings sounded. There’s also the possibility of an extremely-rapid decompression, and it’s described toward the end of this post. 
Hypothesized Chain of events:
  • Likely fuselage failure near SATCOM antenna adapter, disabling some or all of GPS, ACARS, ADS-B, and ADS-C antennas and systems. 
  • Thus, only primary radars would detect the plane. Primary radar range is usually less than 100nm, and is generally ineffective at high altitudes.
If the decompression was slow enough, it’s possible the pilots did not realize to put on oxygen masks until it was too late. (See Helios 522) With incapacitated pilots, the 777 could continue to fly on Autopilot - programmed to maintain cruise altitude and follow the programmed route. Using the Inertial Reference System (gyroscope based), the plane could navigate without needing GPS. 

Other thoughts:
  • The plane was [UPDATE: WAS NOT] equipped with cellular communication hardware, supplied by AeroMobile, to provide GSM services via satellite. However this is an aftermarket product; it’s not connected through SATCOM (as far as I know). 
  • [UPDATE]: However, if the plane flew over or near land, then cellular connectivity is still possible.
  • Interestingly, 19 families signed a statement  alleging they were able to call the MH370 passengers and get their phones to ring, but with no response.
  • When Malaysian Airlines tried to call the phone numbers a day later, the phones did not ring. By this time, fuel would have been exhausted.
Note:  777 Passenger Oxygen masks do not deploy until cabin altitude reaches 13,500. Passengers were likely already unconscious by then, if it was a slow decompression. Also remember that this flight was a red-eye, most passengers would be trying to sleep, masking alarming effects of oxygen deprivation. No confirmed debris has been found in the search area, consistent with the plane having flown for hours after it lost radar contact.
[UPDATE 3/12]:

Issues of Decompression:
Whatever type of decompression happened, it was likely a non-catastrophic decompression that incapacitated the crew. It could have been a slow decompression. (This scenario is more likely if the “mumbles” observed by another MH pilot are legitimate.) It could have also been an extremely rapid decompression, forcing the lungs to exhale more rapidly than they are capable of. Either type of decompression makes it difficult for the crew to respond before becoming incapacitated. 
This table from Carlyle shows that after a moderately rapid (2-6 second) decompression at MH370’s cruise altitude, the crew would have had only 30-45 seconds of useful consciousness unless they started oxygen breathing soon enough.

For all 3 types of (slow, moderate, extremely-rapid) decompression, there is substantial danger to the crew and passengers. 

I was recently asked via Facebook, “Do any alarms go off when unexpected decompression occurs?”
Yes. An alarm in the flight deck is triggered if cabin altitude exceeds 10,000. However, reacting to it (with quick judgement, reasoning, and execution) is far more difficult than it would seem. An “obvious” first thought might seem to “throttle back and configure the autopilot to start descending now; to get to safe altitude.” 

However that first instinct is completely wrong. It takes a surprising amount of training to instill into pilots that what they *need* to do first is put on oxygen masks. To train airline pilots, we often put them into a pressure deprivation chamber, simulate a gradual decompression, and follow up with oxygen breathing from a bottle. Many pilots say they notice an astounding difference in mental performance once they start the oxygen. 
If handling decompression incidents was so trivial and obvious, why else would there be such drastic training?
Historical note: The 777 had an early history of decompressions when the first planes were rolling off the assembly line in 1995, however the incidents were managed safely.
So why does all this matter?
The aircraft may be at the floor of the East China Sea, Sea of Japan, or the Pacific Ocean thousands of miles northeast from the current search zone.  

  • Investigators should obtain data logs from primary radars throughout mainland China that would have been along the planned route. They may be the best clue as to the trajectory of the aircraft.
  • Investigators should obtain all passengers’ cell phone log and location data. The timing of the last successful cellular connection (ring/SMS/data-packet) can predict how long the plane was in the air. iPhone/iOS location (GPS) data may be available from Apple if subpoenaed. Android location data may be available from Google. 
  • Add a secondary search space to include a 300nm+ radius around Beijing, focusing on surrounding bodies of water. Using planned routing trajectory, known autopilot logics, fuel quantities, and weather patterns, it may be possible to define a smaller 50nm * 50nm search space. Consider running the above scenario in MH’s 777-200ER full flight simulator.  
  • Boeing should provide expertise about fuselage/antenna design and autopilot/navigation logic, so as to help plot this second search space. 
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