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On the Qantas Flight 32 incident, the Airbus A380's number two engine encountered an uncontained rotor failure and partially damaged the controls of number one engine as well.

According to Wikipedia, engines one and four entered a 'degraded mode' after the explosion, and number one could not be shut off after landing.

So it seems that in case an engine loses all communication signals from the aircraft's control systems in the cockpit, it could somehow remain operational. To me that definitely sounds a lot safer compared to shutting down and risking losing all thrust.

So do jet engines, by design, keep producing thrust in case they lose contact with the control systems?

florisla
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General rule here: the engine will remain at its last power setting should the FADECs lose comms with the flight deck controls (in your A380 case) or the thrust lever cables come unhooked (in the case of an older aircraft with mechanical cable-and-pulley controls).

However, the fire handle will kill the engine even if the main controls fail -- it operates the firewall fuel and hydraulic shutoff valves. In QF32, this didn't happen because the cable for the #1 engine fire handle itself was damaged by shrapnel entering the wing.

UnrecognizedFallingObject
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    That sounds like a horribly bad design: an accident that causes an engine fire may also cause the fire suppression system to fail. The usual norm is fail-safe: if the safety shutoff valves become uncontrollable for whatever reason (implies significant unforeseen damage) then they should fail closed. Of course, this implies that there should be redundant control of those valves lest they become a SPOF for an engine. – MSalters Jan 13 '15 at 21:22
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    @MSalters -- two points. First is that an uncontained engine failure (such as QF32) is essentially a game of roulette as to what suffers from the shrapnel bombardment the plane just received -- one day it may be the fire handle cable for the engine next to it on the wing, the next day it might be a hydraulic line feeding the outboard slat actuator. Second, engine mountings in modern jets are designed for the most part (center engines in trijets are the only exception that's newer than the very first jetliners) to come off the aircraft cleanly if they do experience an uncontrolled fire, AIUI. – UnrecognizedFallingObject Jan 20 '15 at 02:23
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    @MSalters In this case it isn't clear whether fail closed is the fail safe option. If we were discussing a power plant turbine or a ship board engine I'd agree. But in the unique operating envelope of an aircraft shutting an engine unwarranted may have equal or greater damage potential than not being able to shut down an engine. – curious_cat Jan 31 '16 at 00:50
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    @curious_cat Especially when it's the remaining engine on the side where you already lost one engine. QF32 would have been in serious trouble had the #1 engine shut down in flight. They were having a hard time controlling it as it was. – reirab Feb 05 '16 at 19:56
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    @reirab Good example. The point is that fail safe isn't always fail closed. – curious_cat Feb 06 '16 at 02:39
  • "In QF32, this didn't happen because the cable for the #1 engine fire handle itself was damaged by shrapnel entering the wing." So why not put the valves in the fuselage (where they should be safe, or, at the very least, saf_er_, from engine shrapnel) rather than the wing? – Vikki Apr 21 '18 at 17:33
  • @Sean -- because the valves need to be at the engine firewall in order to isolate the engine from the rest of the plane – UnrecognizedFallingObject Apr 21 '18 at 17:42
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    @Sean Adding to what UnrecognizedFallingObject said, there's also a metric crapton of jet fuel in the wing tanks of many modern airliners. You'd need to cut off the engine feed from those tanks, and you might not want to pump all that into the fuselage and then back again just so you can have a cutoff valve within the fuselage (which may or may not do its job properly after an uncontained engine failure, even if it wasn't for the possibility of a fuel leak directly from the tanks...). – user May 03 '18 at 18:30