Date: 202012
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: EMB ERJ 145 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground ZZZ
Aircraft component: Pressurization Control System
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Communication Breakdown
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural MEL / CDL
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Returned To Gate; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Company Policy; MEL; Procedure; Human Factors
Primary problem: Aircraft

Narrative: This was a rapid pressurization. After single engine start; I asked the FO (First Officer) to accomplish the single engine after start checklist. We received taxi clearance to Runway XXL. I began taxiing about 50 feet and the aircraft began pressurizing immediately. Everyone on the aircraft began feeling their heads squeezed together.  Immediately the EICAS gave a 'PRESN AUTO FAIL' caution. What would you do? Are you going to let the airplane keep pressurizing until it reaches 14;500 ft while simultaneously running the QRH and then aircraft drops masks mid checklist? I used my instincts and immediately stopped the aircraft; set the parking brake and pressed the 'dump' button near the pressurization panel to dump the pressurized air. I only knew to immediately do this because I've personally thought of this scenario plenty of times in situations where the boarding door was closed and external air condition was hooked up. I always thought to myself if the door couldn't open quick enough then I'd need to dump the air; so my instincts reacted as such when this actually occurred. This is not something I was taught; this is not something the company teaches; however it should certainly be a point of emphasis. Moving along; after I dumped the air; the aircraft began depressurizing as expected just enough for about 3 seconds and then immediately began pressurizing again. I unpressed the 'dump' button and pressed it again. Nothing happened. I did this instantly. Afterwards I pressed the manual pressurization button; and rotated it to 11 o'clock position and waited 2 seconds; nothing happened; I then rotated full clockwise but the aircraft kept pressurizing and I wasn't going to wait to run the checklist as the aircraft altitude kept climbing. I have read this checklist before and ran through this procedure on my own time once or twice due to curiosity; so I knew what to do personally. I then pressed the EMER CALL button to the flight attendant; and told him to immediately open the galley door. Keep in mind all of this happened within 15 seconds. I also told him the galley door because I didn't want passengers to panic and run out the boarding door thinking their heads were going to explode. This is how it felt. When the flight attendant opened the door; it slammed open; as expected; despite the pressurization knob fully rotated to the right. Then I ran the QRH. Keep in mind we were not losing pressurization; we were rapidly pressurizing; oxygen masks were not my immediate thought on the ground. The checklist says to don oxygen masks during rapid decompression. I made the PIC authority to open the galley door once the pressure would not dump properly because I knew it would completely depressurize the aircraft. After I ran the QRH; I called Maintenance and they wanted to MEL the Auto Pressurization; and have me continue with the aircraft to ZZZ; an airport with a field elevation of 3200 plus/minus 100 feet. One; I've never controlled pressurization manually in flight; and secondly I've never been to ZZZ; a high elevation airport. So I refused. Nonetheless; we went through the QRH; I ran through the proper steps from instruction from the book; and Maintenance. I did what the QRH said; which I actually did myself already; then I personally went to go close the galley door myself; in case it didn't properly pressurize. I at least considered running through the proper MEL procedure; however I was still not sold on taking the airplane. Once I closed the door; the same thing happened; aircraft began over pressurizing. I immediately opened the door again. I went back on the phone with Maintenance; after a quick discussion with my First Officer & flight attendant; I told Maintenance Control 'I will not take this aircraft.' He said ok; we ended the conversation; then I began coordinating with OPS for a gate return. I did not want to taxi with the galley door open; nor did I feel it was safe to close the door as well; so I simply turned off the #2 engine; the only one running; and asked to be towed back to the gate. I sent an ACARS message to Dispatch 'returning to gate; need new aircraft.' They responded 'copy.'  After a few minutes a tug came; we were towed; I blocked in and I then I called Dispatch and explained to him the situation. He said he'd call me back. In a few minutes he did; he said he spoke to Maintenance and they wanted to MEL the issue and keep the same aircraft; I refused again. The aircraft was not safe to fly. No one knew what the actual issue was; and unless you felt your head being squeezed in an airplane uncontrollably on the ground; you wouldn't know how that felt. I can't imagine what it would have felt like if we were flying at 3;000 feet and the aircraft wanted to over pressurize to a higher altitude and the dump feature didn't work properly; because opening the door inflight; is obviously not an option. A few minutes later Dispatch called and said they'd reach out to the Duty Manager and call me back.  The Duty Manager then called me; he said the same thing the Dispatcher said; to MEL the aircraft; and continue on the same plane. I respectfully refused again. The aircraft was not safe to fly. The Duty Manager then coordinated a new aircraft and I swapped to one about 30 minutes later. I must repeat; if you were not on the aircraft; you do not know how it felt. The crew was light headed; myself included; and the passengers had to have been as well. As a crew I felt we made the right decision; despite pressure to take out the same aircraft. About an hour later; when my new aircraft was being boarded; the previous aircraft was adjacent to us being worked on by Maintenance. In other words; it was not a simple MEL procedure. The aircraft was not safe to fly. Our new plane was just fine; we boarded; and proceeded to ZZZ safely and landed about 2 hours late. The QRH procedure is for inflight; and mainly focused on cabin depressurization; we were being over pressurized.  There wasn't enough time to run a QRH all while solving the issue as the aircraft continued pressurizing on the ground. I wasn't sure how much time I would have. There were children on board; I immediately thought about everybody; and since I knew opening the door would solve the issue; I made the decision to open. I didn't know of any other checklist action item would actually stop exactly what was happening. There isn't even a tab here for cabin over pressuring. You had to be there.




Synopsis: Captain reported returning to the gate and refusing an aircraft that had an uncontrollable cabin pressure issue.