Narrative:

Enroute; we experienced a cabin altitude amber cas message that caused us to defer the automatic function of the cabin pressurization system. The system was not reacting appropriately to the schedule when in hi elev mode and displayed the message inappropriately; we thought; given the information in the operations manual and the QRH. Mx shared with us an identical account by a crew on a different tail number. While the sic was delivering a forgotten box to our inbound passenger and fielding questions from a charter crew looking for assistance in getting their passengers to their destination after an aog; I completed the deferral and began to tackle another possible mx issue. With that resolved; I began to review the operations manual procedures regarding the use of manual mode of the pressurization system. The sic soon joined me in the cockpit where I reviewed with him the procedures and asked that he peruse the OM [operations manual] to make sure I didn't miss or misconstrue anything. I briefed the sic of the note (in the fs ptm) regarding placing the cabin altitude toggle switch into either up or down for more than 6 seconds 'causes a pronounced and startling change in the rate of cabin climb or descent'. The OM [operations manual] doesn't note this; however; elsewhere; it notes a 'dramatic' change in rate. Since we were at 9;000 MSL for takeoff we briefed not climbing out at an excessive rate so as to be able to keep up with the cabin altitude adjustment. We were also aware of the fact that we didn't wanted to delay a normal climb from the airport. We discussed that we were unaware of how the manual mode would react and the effort it was going to take to adequately control the cabin. The sic expressed some reservation conducting the flight given the lack of training in the actual operation of the manual mode. After takeoff; given the climb rate of the jet and the need to immediately control the cabin down to below airport elevation; I found it difficult to set an acceptable rate. Frustrated; I found myself controlling the manual mode into the 'startling and dramatic' range and the cabin went to a below sea level range. I managed to get it back to a positive climb rate as we continued our climbout. As we were passing FL250; I felt that the cabin was at lower altitude than normal and began to raise the cabin. It was difficult to adjust the rate up beyond the current climb rate with short toggle applications. I directed the pilot flying to manage the radios as I maintained attention to the system. We were passing FL275 for FL290 when the pilot flying asked to return to FL270. ATC cleared us back to that altitude. We were thinking a stable altitude and power setting would ease control of the system. Once again; I controlled it into the 'startling and dramatic' range. The cabin climbed dramatically setting off the red cabin altitude message. The pilot flying pushed the nose over to begin a descent and we donned the masks. I believed we could simply get to FL270 and regain control of the cabin instead of an emergency descent. The pilot flying descended to FL260 and leveled off since I was asking why he was descending. The cabin rise and call to ATC to get a return to FL270 by the pilot flying couldn't have happened together at a worse time. The two of us were working separate issues at that precise time and I feel that it divorced us of the greater picture if not for a brief span of time. At FL260; I informed ATC that we were trying to manage a pressurization issue and asked to descend to 17;000. Once at 17;000 [feet] we felt we had stabilized the cabin and continued to [destination].do this in the sim. Startling and dramatic doesn't even describe how fast the rate changes. While I felt like I didn't get close to the six seconds of input I wonder if repeated attempts close together pushed it towards that threshold. The sic and I discussed the flight after we landed. While I felt informed about the procedures and he felt 'untrained' we should have reached out to the fleet director for additional information and advice.

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Original NASA ASRS Text

Title: CE680 flight crew reported difficulty controlling the cabin pressure using the manual backup system; and the FO reported pain in his eyes and ears as a result of the pressure fluctuations.

Narrative: Enroute; we experienced a CABIN ALTITUDE amber CAS message that caused us to defer the AUTO function of the cabin pressurization system. The system was not reacting appropriately to the schedule when in HI ELEV mode and displayed the message inappropriately; we thought; given the information in the Operations Manual and the QRH. MX shared with us an identical account by a crew on a different tail number. While the SIC was delivering a forgotten box to our inbound passenger and fielding questions from a charter crew looking for assistance in getting their passengers to their destination after an AOG; I completed the deferral and began to tackle another possible MX issue. With that resolved; I began to review the Operations Manual procedures regarding the use of Manual Mode of the pressurization system. The SIC soon joined me in the cockpit where I reviewed with him the procedures and asked that he peruse the OM [Operations Manual] to make sure I didn't miss or misconstrue anything. I briefed the SIC of the Note (in the FS PTM) regarding placing the CABIN ALT Toggle Switch into either UP or DOWN for more than 6 seconds 'causes a pronounced and startling change in the rate of cabin climb or descent'. The OM [Operations Manual] doesn't note this; however; elsewhere; it notes a 'dramatic' change in rate. Since we were at 9;000 MSL for takeoff we briefed not climbing out at an excessive rate so as to be able to keep up with the cabin altitude adjustment. We were also aware of the fact that we didn't wanted to delay a normal climb from the airport. We discussed that we were unaware of how the Manual Mode would react and the effort it was going to take to adequately control the cabin. The SIC expressed some reservation conducting the flight given the lack of training in the actual operation of the Manual Mode. After takeoff; given the climb rate of the jet and the need to immediately control the cabin down to below airport elevation; I found it difficult to set an acceptable rate. Frustrated; I found myself controlling the Manual Mode into the 'startling and dramatic' range and the cabin went to a below sea level range. I managed to get it back to a positive climb rate as we continued our climbout. As we were passing FL250; I felt that the cabin was at lower altitude than normal and began to raise the cabin. It was difficult to adjust the rate up beyond the current climb rate with short toggle applications. I directed the Pilot Flying to manage the radios as I maintained attention to the system. We were passing FL275 for FL290 when the Pilot Flying asked to return to FL270. ATC cleared us back to that altitude. We were thinking a stable altitude and power setting would ease control of the system. Once again; I controlled it into the 'startling and dramatic' range. The cabin climbed dramatically setting off the red CABIN ALTITUDE message. The Pilot Flying pushed the nose over to begin a descent and we donned the masks. I believed we could simply get to FL270 and regain control of the cabin instead of an emergency descent. The Pilot Flying descended to FL260 and leveled off since I was asking why he was descending. The cabin rise and call to ATC to get a return to FL270 by the Pilot Flying couldn't have happened together at a worse time. The two of us were working separate issues at that precise time and I feel that it divorced us of the greater picture if not for a brief span of time. At FL260; I informed ATC that we were trying to manage a pressurization issue and asked to descend to 17;000. Once at 17;000 [feet] we felt we had stabilized the cabin and continued to [destination].Do this in the sim. Startling and dramatic doesn't even describe how fast the rate changes. While I felt like I didn't get close to the six seconds of input I wonder if repeated attempts close together pushed it towards that threshold. The SIC and I discussed the flight after we landed. While I felt informed about the procedures and he felt 'untrained' we should have reached out to the Fleet Director for additional information and advice.

Data retrieved from NASA's ASRS site 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.