(1) The Lear series is certificated with a minimum crew of two pilots....
... so the older Captain's health/consciousness would not normally bring this result if he was incapacitated due to his own health issues.
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(2) Smooth handling of the cabin pressurization system is a little tricky...
... there are simplistic automatic profile settings for the anticipated cruise altitude....
.... And manual override controls on the co-pilot's side of the cockpit
Older airframes with many cycles are typically "leaky" --
...and the crew /especially the co-pilot would have to be alert & sharp to catch a subtle "climb" in cabin altitude due to a leaky door seal, f'rinstance.
The Payne Stewart tragedy was a subtle pressurization problem that occurred in its final form at altitudes sufficient to render the crew incapacitated in about 1 minute.
The Jenni Rivera crew should have had sufficient time to don crew oxygen masks and correct the pressurization problems-- including descent and return to the origin airport.
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(3) The Lear series had some midlife issues that revolved around the NiCad battery system overheating and forecfully bursting--
This disintegration was found to cause physical damage to the flight controls AND/OR damaging the fuel lines that passed through the same tight spaces in the back of the rear service compartment.
Several serious crashes were eventually attributed to this system breakdown --
The FAA issued AD's to redesign /reroute the critical fuel lines.... AND
.... Imposed procedural restrictions for use of battery power on the ground...
...With additional periodic maintenance processes for testing /replacement of the battery.
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So the questions are begged...
Were all of the AD's complied and complete??
Certainly -- if the aircraft was operated in the USA....
... If it was "owned" in the USA and only operated in Mexico... MAYBE NOT...
In the wee hours of the morning-- did the crew find it necessary to accomplish battery starts (without an external power cart)??
Did the crew use the checklist correctly and routinely--??
....Or was the young co-pilot just following a salty ol' Capn's orders to start 'em up & blast-off...??
In the wee hours of the morning... was crew duty day /fatigue a factor--did they miss something important on the taxi/takeoff checklists??
The "star" arrives -- and everyone expects the crew to start/taxi & takeoff ASAP...
If the pressurization settings were not set correctly before takeoff...OR there was a slow air leak.....
Did the crew "catch" the cabin altitude problem before they lost useful conscieousness??
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Last but not least possibility--
(4) If the crew exceeded any airframe speed/mach limitations during the climb-- structural compromise /failure of the flight control/trim surfaces -- that would also suffice to send the aircraft plummeting...
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One last thought about investigating the crash...
IIRC --not all (older) "charter" planes are required to fly with the typical "black boxes" like airliners.
(cockpit voice recorders or flight data recorders--etc)
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OK -- just food for thought.... a few possibilities...
This is a sad loss--- prayers for the families of those who perished in this accident.
Good information. Thanks to all for your insghtful posts.