B737 MAX Series Undifferentiated
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance; Ground Event / Encounter Weather / Turbulence
General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
During pre-flight in heavy snow and wind; the APU generator dropped off line; and became available again within about 10 seconds. This happened twice; about ten minutes apart. Also; the APU bleed air pressure dropped to lower than usual; then recovered about 30 seconds later. We advised maintenance; the mechanics checked our plane (737 MAX) and the 737 MAX on another gate; and informed us that the APU does that in heavy snow; likely due to snow entering the inlet door. The APU was operating normally. We planned to start one engine at gate (to keep ground power available; just in case APU dropped offline; similar to starting without an APU).  Flight eventually cancelled due to weather; we did not ever start an engine or leave the gate. If this is a known issue to the local mechanics; it should be in our manuals; or the problem should be addressed in some way. The APU is operating normally; but if the power can drop offline due to snow; that could be very problematic during pushback and engine start in snowy conditions; and potentially a safety issue if the aircraft is effectively stranded after pushback with only battery power in snowy conditions.  Our plan to start one engine at the gate with ground power available would be a proposed workaround; but that should probably be codified somewhere. Filing to indicate a potential safety issue.
Air Carrier Check pilot reported the APU on their 737 MAX continued to shut down while in service at the gate while in a heavy wet snow storm. The pilot also stated that another MAX aircraft at an adjacent gate was experiencing the same scenario.