Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human-Machine Interface
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Overcame Equipment Problem
Aircraft; Procedure
While climbing above FL320 to FL400 we 'out-climbed' the pressurization ability of the aircraft and received a DIFF PRESS Warning message. The cabin pressure did not exceed 8.6 PSI. About 30 seconds before the warning; I noticed our climb rate to be above 3;000 feet per minute. I glanced at the cabin pressure and saw it was at 8.4 PSI with a 600 FPM climb. I asked the FO (First Officer); who was pilot flying; to reduce the climb rate as there had been company communication recently that it was possible to exceed the cabin pressure differential limitation while flying with few passengers during the pandemic. We had four passengers aboard. About 10 seconds after the FO went into vertical speed mode to reduce the climb rate; we received the warning. We followed the QRH procedure which got the pressure differential under control and controlled the pressurization in manual for the remainder of the flight as per the QRH. I sent an ACARS to the Dispatcher and to Maintenance and had [them] meet the aircraft at the arrival airport. The recent pandemic has seen us carrying fewer and fewer passengers and as such; we are seeing aircraft performance everyday that we would have rarely seen. As such; we are not conditioned to look at the climb rate of the aircraft in regard to the pressure differential. There had been some recent company communication that reminded us of this issue which I remembered when I saw the rate of climb of the aircraft versus the rate of climb of the cabin pressure. I merely noticed and asked the FO to reduce the rate of climb too late to stop the warning from occurring. After the event; I went and looked at the memo again and will pay more attention to reducing my rate of climb once above FL300 from now on. The QRH procedure works well in reducing the pressure differential. The problem is that it does not address this particular situation (out-climbing the pressurization). Once we got the differential under control the QRH guides you to manual pressurization operation for the remainder of the flight even though I assume there is nothing actually wrong with the pressurization. Perhaps adding a line into the QRH to direct you back to automatic pressurization if you simply out-climb the system would reduce the workload of the pilot monitoring versus having to operate the system manually while maintaining the same level of attention required of the pilot monitoring.
As we were climbing through FL320; a 'cabin differential pressure' warning message populated. Pressure was 8.6 and never exceeded 8.6. Both the Captain and First officer were able to detect an increase in differential pressure due to the high climb rate resulting from low passenger and cargo load. First Officer was correcting high climb rate when the warning message populated. Later the Captain addressed the message with the QRH. Aircraft was in control at all times and the error was detected successfully with no negative consequences.Differential pressure warning message due to very low passengers and cargo load; resulted in excessive high climb rate above FL320.Suggestions: Better monitor climb rate during low passenger loads.
Air carrier flight crew reported that during climbout; the aircraft rate of climb exceeded the pressurization system rate of climb resulting in a warning message. The crew reported an extremely light passenger and cargo load due to the COVID-19 pandemic contributed to the event.