Date: 201908
Local time of day: 1201-1800
Location: SEA.Airport, WA
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: APU
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Communication Breakdown; Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Illness / Injury
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: General Flight Cancelled / Delayed; General Work Refused
Contributing factors: Weather; Procedure; Company Policy; Staffing
Primary problem: Company Policy

Narrative: On our third leg of the day with no APU; we had ground air attached to the airplane. We started boarding the aircraft even though it was warm hopeful the ground crew would be ready to start the engine as soon as everyone was onboard. After about halfway through boarding we started getting complaints from the passengers and Flight Attendants. We tried calling Operations to stop boarding but they didn't call the gate. I ran up to the gate told them to stop boarding; they continued anyway. I; once again; asked Operations why they never called the gate and we need a Supervisor immediately. No Supervisor was available or not quickly enough. Boarding finished; it was over 90 degrees in the cabin and nothing was being accomplished on the ground. I was worried about the crew and passengers health. I tried calling Dispatch but received very little help other than we will back you up if needed. I finally made the announcement for the passenger to expeditiously leave the airplane in the interest of safety and leave their belongings to make this process faster. Passengers were thanking us that we made the call and we said their safety is paramount. I let Dispatch and Operations know what happened and I called the FODO (Flight Operations Duty Officer). (FODO) was supportive and understanding. I asked if we started an engine at the gate in order to help cool down the cabin; if that would be acceptable. He said it would be ok but gave advice to help mitigate other problems. I called Dispatch to give them my plan; talked with the flight attendants; talked with the ground crew and the gate team. Everyone was in agreement and we waited for fuel to facilitate running the engine for upwards of 40 plus minutes. The fueler only added 400 lbs. when asked for 2000 lbs. The FO (First Officer) walked around again and coordinated on the ground with the ground crew. We finally started the left engine; ran it for 20 minutes and got the cabin to between 74; 78; 76 degrees. The flight attendants were satisfied and we commenced boarding. After everyone was on board with an engine running we received a call from scheduling asking us to extend; we both refused because we weren't feeling well from the heat exhaustion and the long day with a broken airplane that required extra handling. A new crew was found and it only took another 10 minutes. I explained the scenario to the next set of pilots and handed over the aircraft; with the engine running; to the FO (First Officer) at the controls than the CA (Captain). I left aircraft to the new set of pilots with a comfortable cabin.This was an excessively unsafe situation. Despite saying ready safe go; we were being pushed to leave. We had no APU; no ground air even with a new jet bridge. It clearly wasn't work properly and we had very little ground staff available. The passengers were beginning to complain and one person felt faint. When we asked for we were being pushed even more. It started with a broken airplane; long scheduled day and finally broken ground equipment. This was not a good situation and it wouldn't surprise me if complaint with the DOT aren't filed. When the flight attendants says it's too hot to board that must be taken to heart and they shouldn't be pushed.




Synopsis: Captain reported that on third leg of the day with an inoperative APU; it became too hot for safe operations and crew refused extension.