Air carrier flight crew reported the aircraft's E/E compartment was flooded; from a severe storm; after the forward cargo compartment was left open.
Synopsis
Air carrier flight crew reported the aircraft's E/E compartment was flooded; from a severe storm; after the forward cargo compartment was left open.
Narrative
There had been multiple ops bans and thunderstorms with heavy rain that led to a significantly delayed flight. After the storms cleared we completed a normal preflight and didnt observe any abnormalities. During pushback we received various Yaw Damper messages followed by every IRS (Integrated Standby Instrument System) message and every light on the overhead IRS panel illuminating. At the same time both AFDs (Adaptive Flight Display) showed unusual attitudes and would blank. This behavior occurred multiple times and seemed related to aircraft movement. After consulting with dispatch we performed a block turn back. When we blocked in; Maintenance reported water coming out of every drain on the aircraft. Shortly thereafter Maintenance reported water in the E/E bay and immediately told us to completely shutdown the aircraft and go dark. Maintenance reported that the E/E bay was flooded.I believe the main cargo door was left open during the storms and; in essence; the plane flooded (we were not at the aircraft until after the weather passed). I think more emphasis should be placed on securing the aircraft for severe weather. Also; when its not possible and the aircraft is left open and exposed to heavy rain; then Maintenance should be required to inspect the E/E at a minimum for water and flooding.Thankfully this happened on the ground. If we were airborne when the systems malfunctions occurred in flight we could have ended up with only the ISIS (Integrated Standby Instrument System) as reliable with convective weather in the area - that could have been a very dangerous setup.
Second reporter narrative
We were delayed stepping to the aircraft due to multiple rain storms at the gateway. When we showed to the aircraft; the jet was loaded and the cargo door was closed. Preflight and the walk-around inspection was uneventful. We got clearance to push back and start the engine s from Ramp Control. As we were pushing back; the air craft showed numerous alert and warning indications. Both L & Right Yaw Dampers caution lights illuminated. Additionally; the Left; Center; and Right INS (Inertial Navigation System) advisories illuminated on the EICAS. Of note; both CAs and FOs AFDs (Adaptive Flight Display) showed a climbing right bank while in straight and level on the ground during push back. The CA contacted dispatch and Maintenance and advised them of the indications and the condition. Maintenance requested that we start the engines in order to reposition the aircraft to the ramp. The flight displays intermittently displayed the Yaw Damper and INU (Inertial Navigation Unit) messages a few times upon movement of the aircraft during ground operations. We taxied to our final parking and after shutdown; one of the ground maintenance crew chiefs excitedly told us to cut all the power to the aircraft. The crew chiefs excitement was because of a lot of water draining from the Avionics Electric bay. After securing the aircraft and stepping outside. I noticed a rather large puddle of water pooling under the aircraft. The aircraft was secured on the ground without further incident. Although weather events and ramp loading status can rapidly change access to aircraft and loading; I believe an increased emphasis should be placed on making sure enough personnel are available the close the cargo door. This will help ensure water doesnt enter the aircraft and drain down to the lowest point which happens to be the Avionics Bay. Thankfully we weren't on Take off roll or airborne when these indications happened. Convective activity was still in the local area and were lucky we didnt have these indications during IMC conditions.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.