B737-800 flight crew reported a fumes event during preflight while executing a special procedure for operating ground air and starting engines. After a delay the flight ultimately departed.
Synopsis
B737-800 flight crew reported a fumes event during preflight while executing a special procedure for operating ground air and starting engines. After a delay the flight ultimately departed.
Narrative
Aircraft X arrived in ZZZZ with a deferred APU bleed valve and was positioned at a ramp level gate with portable ground equipment. During boarding; we discovered the need to add an MEL requiring additional fuel; and were advised it would take an additional 20+ minutes for the fuel truck to return. Cabin air temp was not being adequately maintained by the ground air conditioning cart; so we elected to switch to the 'huffer' external air cart to provide air to the packs for increased cooling during the additional delay. After several attempts by the ground crew to get the cart to supply air; it began to provide adequate air supply. Soon after; an acrid smell began to fill the cabin and a light haziness was visible throughout. We selected the packs off and asked the ground crew to turn the external air cart off. The decision was made to deplane due to poor air quality and rapidly increasing cabin temperature. Some difficulty was experienced communicating effectively with gate and ramp personnel to initiate this process. Once it was understood that this was both necessary and a priority; we were able to deplane without further incident. Dispatch; maintenance control; and the Chief Pilot were notified. After the airplane was inspected by maintenance and returned to service; I verified with each crew member that they were not experiencing any symptoms; felt in good health and verified verbally with each that they were 'fit to fly.' No passengers indicated to the crew any physiological symptoms from this event. After a fresh aircraft security search was accomplished; Aircraft X; boarded and departed uneventfully. This event; while more nuisance than [critical].; required a great deal of crew interaction and awareness to overcome threats introduced by scheduled operations with supplemental air systems and engine start procedures to a hot; humid; international environment. Decreased physical comfort; and barriers in communicating with ground personnel greatly increased workload. While I believe we ultimately managed this situation thoroughly and appropriately; there is always a possibility that details could have been missed; mishandled; or not communicated to us along the way.Ultimately; my primary recommendation is to avoid dispatching aircraft with deferred APU; APU bleed source; or other [non-]dispatchable but nonetheless non-routine procedures to destinations with extreme air temperatures; performance considerations; or regional differences. When issues arise with seldom used ground equipment; cabin temperatures can quickly become intolerable; creating an additional distraction for crews and an uncomfortable and potentially hazardous cabin environment for all. Additionally; the language challenges introduced by international operations make communications during non-routine operations more difficult; exacerbating already challenging situations; increasing potential errors; and delaying efficient reaction to adverse situations. In our case; even while using simple; straight forward language; we were often having to repeat and reconfirm numerous times that individuals understood what was needed. This often led to delayed response and increased discomfort for our crew and guests.
Second reporter narrative
While checking [initial flight release] at the hotel and in the van to the airport we noticed that this aircraft; [Aircraft X] had [a] MEL for an inoperative APU bleed valve. Arriving at the gate it was noticed that external air was not connected to the aircraft. Maybe there was confusion by the ground crew who likely heard the APU and figured the cabin air was being conditioned so we explained the need for a ground air conditioning cart to be connected; and quickly. ZZZZ Operations complied and by the time we boarded the aircraft external air was connected. It was also apparent that operations did not know of the need for an external air cart to start engine #1. For reference the airplane was parked at position XX with no jet way access. Checking the logbook we discovered the inbound crew had to defer the B-System Autopilot with an MEL. Further inquiry into the MEL we noticed the need for [an additional] MEL to also be applied for the Altitude Alerting System. This unfortunately prevented us from flying in RVSM airspace and required an additional 1;000 pounds of fuel. Operations advised this was to going to take roughly 20 minutes.At this point there were numerous complaints of excessive cabin temperature. We discussed and decided it was prudent to transition to the external air cart per Supplemental Procedure X.XX to operate the PACKS to try and cool the cabin. Conditioned ground air was disconnected and the external air cart was connected. Unfortunately there was confusion trying to get the air turned on which further heated the cabin. At about the point we were about to deplane due to excessive cabin heat the external air-cart began to provide sufficient pressure to turn on and operate the PACKS. While the PACKS did begin to cool the cabin it did not take long for the two of us to notice both a strong acrid odor and a visible haze throughout the cabin. At this point we turned the PACKS off. While the odor did slowly begin to dissipate we felt strongly about having passengers disembark until the cabin temperature and air quality were under control. Naturally at this point the fuel truck arrived and station ops wanted us to quickly fuel and transition to starting the engines. We objected and a few minutes later passengers were headed into the terminal. We did not sense the need to evacuate given with the PACKS off the air quality was stabilizing.At this point we felt it prudent to make a logbook entry for the air quality event and felt we endured a Level 2-3 air quality contamination. Our suspicion was that the source of the contamination was the external air cart and it likely having not been used in conjunction with the aircraft Pack's often in ZZZZ. Per Dispatch; Chief Pilot and maintenance control advice we wanted to make sure that our suspicions were true and that there was not an issue with the aircraft itself. The remainder of the events were uneventful as we successfully started engines; ran the packs; observed aircraft cooling and improved air quality. Unfortunately our flight was re-dispatched to ZZZ1 for late night customs control and two new pilots with legal rest; but the customers all made it safely to ZZZ2 at around XA:30am. I feel confident that our interactions as a crew ultimately led to the right decisions being made. This scenario provided numerous distractions; namely the addition of an MEL; additional fuel; non RVSM operations; a language barrier; excessive cabin heat; frequent calls from the cabin regarding potable water; starting an engine with an external air source and an air quality event. I feel our priorities never swayed from our interest in passenger and crew safety and operating the aircraft in an airworthy fashion. That said this scenario provided numerous irregular operations and there is the potential we may not have thought of everything. I completely understand that aircraft scheduling is complex and not always visible to crews. That said; not having APU bleed air ina tropical location definitely causes passenger and crew discomfort even when all ground external air carts and ground conditioned air operates normally. With the addition of a language barrier and equipment not operating seamlessly this caused numerous threats and the potential risk to passenger and crew health. ZZZZ Operations had the best of intentions and definitely was doing everything they could to accommodate our demands. Given the non-routine nature of having to start an engine with an external air source and the inability to clearly communicate; dispatching aircraft to tropical locations in a foreign country doesn't make sense to me. I have no doubt the ground crew in ZZZZ is appropriately trained to handle these events; but my suggestion would be to limit reliance on the use of such equipment to aircraft that happen to break in these locations and not be dispatched to these locations with similar MEL's.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.