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BeechPapa

777 Equipment Cooling Override

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Was looking out the starboard window, and heard a bunch of alarms going off.  When I turned around I saw a few yellow EICAS messages related to the engine, but they went by too fast for me to read them. I was also distracted by the fact N1 had dropped to idle. Finally the EICAS settled on a single warning: EQUIP COOLING OVRD, and then n1 was restored. I followed the EQUIP COOLING OVRD checklist and the warning went away. The remainder of the flight was uneventful. No failures were active through this event. 

 

Any ideas why the system would go into override mode? The FCOM/QRH don’t explain why this mode occurs, nor the strange engine behavior. Any insight is appreciated. 

 

2014_10_27_10_52_57_848.jpg

 

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Any ideas why the system would go into override mode?

 

The forward cooling system will go into override mode if the supply fans have shut down, there is low airflow, the EQUIP COOLING switch is off, smoke is detected or the FWD CARGO FIRE switch is armed.

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I was not touching anything except for the view hat when the alarm went off, and the only thing next to the view hat is my trim switches, so I don't think I could have accidentally armed FWD CARGO FIRE or turned off the EQUIP COOLING switch (which was verified in the on position when I started running the checklist).

 

The only thing I can remember doing was turning the cabin and cockpit temp knobs a little toward C. I was flying LAX-MIA mid day so the temps were warm. This warning happened over the eastern part of the Gulf of Mexico, where the weather started to get warmer. Could that, in combination with the colder air conditioning demand, have reduced the airflow to the equipment, and incited the warning?  

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No failures were active through this event. 

When saying this, did you actually check in the CDU, or did you just set up the sim to not have any failures?

The reason I ask is this: The 777 has Service Based failures built in. In other words, the plane ages and failures happen based on usage.

The only way to change this is through the CDU, it's not part of the random failures, and it is ON by default.

 

Just checking.

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When saying this, did you actually check in the CDU, or did you just set up the sim to not have any failures?

The reason I ask is this: The 777 has Service Based failures built in. In other words, the plane ages and failures happen based on usage.

The only way to change this is through the CDU, it's not part of the random failures, and it is ON by default.

 

Just checking.

 

I actually checked the CDU. I experimented with random errors 2 flights previously and thought maybe I forgot to turn it off. Nothing was activated. I do have service based failures on rate 2x but I am 122 hours away from my next service. Even if it was a service-based failure, it would show up in the CDU, wouldn't it?

 

I'm not quite sure it was technically a failure either, since I never lost anything permanently (no recirculating or equipment cooling fan failures) equipment cooling was just turned off temporarily by the plane and the checklist was only a restart of the equipment cooling system which, thankfully, worked.     

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The ECAIS systems you saw flash were the original cause of some sort of electrical problem. EQUIP COOLING OVRD is the automatic reconfiguration of a B777's Electrical Equipment bay ("MEC") which commands a vent to open to outside ambient air sucking smoke or electrical fumes from the MEC. This also draws air pressure from the cabin. 

It exposes the cabin supply ducts to ambient air pressure therefore is also designed to inhibit and silence cabin pressure alarms. The MEC vent will normally close once smoke is no longer detected.

Worth noting too that whilst the MEC has fire and smoke detection there is no fire or smoke alarm provided to pilots except in the Cargo Freighter version of the B777

 

 

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