A MD83's cabin climbed about 10;000 ft while on a ferry flight following a 'C' check but the captain...

Narrative:

While in cruise at FL340 on a ferry flight back from a 'C' check; we were three people in the cockpit; the captain; the director of quality control; and me. While en route the cabin altitude indicator started to rise. I called it to the captain's attention; and he replied 'let me know if it reaches 9;000 ft.' a minute after when it reached 9;000 ft I called it to his attention. A couple of seconds after we got the cabin altitude light; when the attention of the captain was directed to the cabin altitude and differential pressure indicator. I noticed the aircraft started to depart our assigned altitude of FL340; so I called it to the captain's attention 'altitude' then for a second time again 'sir altitude we are descending.' for a third time I questioned him if he wanted altitude hold mode. He kept looking at the cabin altitude and differential pressure indicator with the other company employee in the jump seat. During this time we were already 350 ft below our assigned altitude; so I took the action to ask ATC for a lower altitude a second after the captain heard me on the radio he said 'ask for lower;' but don't sound too desperate. At that point ATC gave us clearance to descend to FL280 first then a split second after gave us clearance again to descend to FL240. While the controller was giving me this clearance I told the captain 'altitude' and pointed his altimeter; and he replied '(expletive)' (expletive) what happened' and he was trying to climb back up to FL340 and at that time we were 480 ft below our assigned altitude. I told him 'sir; sir; we are cleared now to FL290' and that split second after I told him; we were cleaered to FL240 'set and arm ' and I replied again 'sir FL240 set and armed' and pointed to the FMA. I just wanted to make sure we were on the same page. During this time I was also monitoring back and forth the cabin altitude indicator when we got the cabin altitude light I got my oxygen mask ready and rapidly turn and told our employee on the jumpseat to put his mask on. While on the descent the cabin rise to 13;400 ft; but when we were below FL280 the cabin started to go down within the limits. When he queried us 'is everything ok ' the captain replied on the mic. 'Yes everything is fine'; we just got an annunciation that's all; but everything is fine.' when I told our employee in the jump seat to get his oxygen mask out I also told my captain; but he was a little confused or distracted by other things in the flight; so I called to his attention. I said 'sir; sir; correct [me] if I am wrong but the regulation calls for if we are in a cabin pressure altitude of 10;000 to 12;500 for more than 30 minutes we have to be in oxygen.' he replied 'that's correct' ; he looked at the cabin altitude and differential pressure indicator and he replied '(expletive) I didn't know it got that high ; because when he looked it was at 11;200 and descending at like 1;200 ft per minute. In the MD83 we get the cabin altitude light when the cabin reaches 10;000 ft. I still don't understand why he said I did not know it got that high; because the moment that light is on you know you are at 10;000 or above cabin altitude.

Original NASA ASRS Text

Title: A MD83's cabin climbed about 10;000 FT while on a ferry flight following a 'C' Check but the Captain were very slow to respond to the anomaly; never donned oxygen nor declared an emergency. The cabin began to descend below FL280.

Narrative: While in cruise at FL340 on a ferry flight back from a 'C' check; we were three people in the cockpit; the Captain; the Director of Quality Control; and me. While en route the cabin altitude indicator started to rise. I called it to the Captain's attention; and he replied 'let me know if it reaches 9;000 FT.' A minute after when it reached 9;000 FT I called it to his attention. A couple of seconds after we got the cabin altitude light; when the attention of the Captain was directed to the cabin altitude and differential pressure indicator. I noticed the aircraft started to depart our assigned altitude of FL340; so I called it to the Captain's attention 'altitude' then for a second time again 'sir altitude we are descending.' For a third time I questioned him if he wanted Altitude Hold mode. He kept looking at the cabin altitude and differential pressure indicator with the other company Employee in the jump seat. During this time we were already 350 FT below our assigned altitude; so I took the action to ask ATC for a lower altitude a second after the Captain heard me on the radio he said 'ask for lower;' but don't sound too desperate. At that point ATC gave us clearance to descend to FL280 first then a split second after gave us clearance again to descend to FL240. While the Controller was giving me this clearance I told the Captain 'altitude' and pointed his altimeter; and he replied '(EXPLETIVE)' (EXPLETIVE) what happened' and he was trying to climb back up to FL340 and at that time we were 480 FT below our assigned altitude. I told him 'sir; sir; we are cleared now to FL290' and that split second after I told him; we were cleaered to FL240 'set and arm ' and I replied again 'sir FL240 set and armed' and pointed to the FMA. I just wanted to make sure we were on the same page. During this time I was also monitoring back and forth the cabin altitude indicator when we got the cabin altitude light I got my oxygen mask ready and rapidly turn and told our employee on the jumpseat to put his mask on. While on the descent the cabin rise to 13;400 FT; but when we were below FL280 the cabin started to go down within the limits. When he queried us 'is everything OK ' the Captain replied on the mic. 'Yes everything is fine'; we just got an annunciation that's all; but everything is fine.' When I told our employee in the jump seat to get his oxygen mask out I also told my Captain; but he was a little confused or distracted by other things in the flight; so I called to his attention. I said 'sir; sir; correct [me] if I am wrong but the regulation calls for if we are in a cabin pressure altitude of 10;000 to 12;500 for more than 30 minutes we have to be in oxygen.' He replied 'that's correct' ; he looked at the cabin altitude and differential pressure indicator and he replied '(EXPLETIVE) I didn't know it got that high ; because when he looked it was at 11;200 and descending at like 1;200 FT per minute. In the MD83 we get the Cabin Altitude light when the cabin reaches 10;000 FT. I still don't understand why he said I did not know it got that high; because the moment that light is on you know you are at 10;000 or above cabin altitude.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	997080
Time
Date	201203
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	MD-83
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Pressurization Control System
Person 1
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP)
Experience	Air Traffic Control Non Radar 5 Air Traffic Control Radar 7 Flight Crew Last 90 Days 190 Flight Crew Total 5180 Flight Crew Type 1285
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Published Material / Policy
Miss Distance	Vertical 0480

A MD83's cabin climbed about 10;000 ft while on a ferry flight following a 'C' check but the captain were very slow to respond to the anomaly; never donned oxygen nor declared an emergency. The cabin began to descend below FL280.