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Comment by f233f2 | Hacker News Reader

>Federal officials allege Joseph David Emerson tried to shut down the engines in midflight and had to be subdued by the two pilots.

Why couldn't he? Does it take a long time to press the button, do you need several people to press it at once...?

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I know nothing about airplanes, but surely it would be a multi-step process involving override modes, power-down phases, klaxons, red blinking lights, warning messages, physically separate switches, and so forth?

Two steps: Pull the fire handle, then turn the fire handle.

It's a valid question if that is safe enough. Once you release the fire suppressant into the engine, I think engine restart becomes impossible.

On the 175, pulling the handle cuts fuel, hydraulics, and bleed air. Turning the fire handle discharges a bottle. Turning it the other way discharges the other bottle. It has been reported that in the Sim turning the handle back re-establishes fuel, hydraulics and bleed air, and engine restart is theoretically possible, however it's never really been done in the air before. I don't think it's documented anywhere what really can occur - since once you've established that the engine is on fire you aren't in any scenario going to try to bring it back online afterwards.

Do it for both engines. Yikes. That's a lot of workload.

I would hope that the button would not be responsive if the plane is literally midflight, or have some failsafes to prevent exactly this kind of situation.

Obviously I'm not a pilot but I can't imagine many scenarios where a commercial flight would want to actively shutdown the engines with just a simple command while midair. But I'm willing to be corrected if thats not the case.

> I can't imagine many scenarios where a commercial flight would want to actively shutdown the engines with just a simple command while midair.

The scenario has already been mentioned elsewhere in this thread: an engine fire. If the engine is actually on fire, you want the flight crew to shut it down as quickly as possible, because the plane could be seconds away from a jet fuel explosion.

The engine shutdown is there in case of engine fires. Gliding without engine power is a bad situation, but being on fire is worse.

And usually it's just one engine that's malfunctioning, so you shut that one down and fly to the nearest airport on the remaining engine.

Even if he could shut down the engines, the plane doesn’t fall immediately from the sky. They would have plenty of time to turn them on again.

Discharging the fire bottle into the engine complicates things a bit.

That depends a lot on the flight phase. Losing all engine power seconds after take-off is very often not recoverable.

It turns out there was enough fuel in the lines to keep the engines running until his action could be reversed after subduing him.

I think First Officer can override the decision in these situations

No. There are two fire handles in the overhead panel, one for each engine (and a similar one for the APU on some types). You pull it, that immediately shuts off fuel, hydraulics, generators etc on that engine. Twist it to discharge the fire extinguishers on that engine. No override, no extra steps.

In case of an engine fire the procedure is to put a hand on the handle, the other pilot checks and confirms, and then you pull it.

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