wrote

In accounts of the crash of the Cypriot airliner in Greece,

My thoughts on yesterday's accident.

The way the regulations require that it be done.

First........During the preflight, someone ensures that the emergency
oxygen bottles in the lower cargo holds have their valves opened and are
ready for use.

Second...During the cockpit preflight, each pilot tests his oxygen mask
for proper operation and for pressure delivery of oxygen.

Then.......With the engines running and before takeoff, the air
conditioning and pressurization system is turned on (pack valves opened)
and the cruising altitude set in the controller by a crewmember and
verified by the checklist.

The system then functions normally, maintaining a cabin pressure of about
8,000 feet until starting descent.

However if something goes wrong and the cabin altitude rises
uncontrollably............

First.......At 10,000'cabin altitude, A VERY loud warning sounds to alert
the crew. If at cruise altitude, this MANDATES first, immediate donning
of the pilot's oxygen mask followed immediately by an emergency descent
to 14,000'.

Second.. At 13,000' cabin altitude, the outflow valves automatically
close in an attempt to maintain cabin pressure if the system has been
properly turned-on before takeoff. If the system was not properly
turned-on before takeoff, the warning should have occurred during climb.

Third.....At 14,000' cabin altitude, the passenger oxygen masks
automatically drop.

All of these systems are independent. News reports indicate that the
passenger O2 masks did deploy. If so....

Did the warning sound? If it did why was there no emergency descent?
Why was pressure not maintained when the outflow valves closed? Perhaps
the pack valves were not opened before takeoff? Had the pilots O2 bottle
been replaced and the valve not opened or checked during preflight?

Looks like a lot of human error to me. Just speculating.

Bob