In the approach phase, engine 1 of [Cathay Pacific flight 780](https://en.wikipedia.org/wiki/Cathay_Pacific_Flight_780) got stuck at about 70% N1 and it forced the crew to do an overspeed landing (230knots).

Why didn't they shut it off by turning the fuel pumps off? Is there a backup mechanism if the fuel valve fails like in this scenario?
['https://aviation.stackexchange.com/questions/59303', 'https://aviation.stackexchange.com', 'https://aviation.stackexchange.com/users/36788/']
You can find the [full incident report here](https://www.webcitation.org/6Rk7TGDPW?url=http://www.cad.gov.hk/reports/2%20Final%20Report%20-%20CX%20780%202013%2007%20web%20access%20compliant.pdf) and this topic is touched upon briefly, but in short they had little to no time to entertain any other options but a full speed landing.

> 
> It was not until the aircraft [was] on the final descent for landing that
>  the Commander realised they could not reduce the thrust on the number
>  1 engine. The speed was not controllable and from that point, there
>  was no time for the crew to consider other strategy nor procedure to
>  cope with such emergency situation.
> 
> 
> 

and more in the conclusion section... 

> 
> **t.** At that stage, there was no time for the flight crew to consider other
>  strategy nor procedure to cope with such emergency situation. The
>  flight crew concentrated on flying the aircraft for a safe landing.
> 
> 
> 

First off, the engine was throwing errors throughout the flight and they were talking to the maintenance team at other points. Ultimately, the proper steps were taken and everything was done by the book. They were prepared for an engine-out landing. When you have a runaway engine malfunction (or throttle stuck at full) shutting down prior to landing *may* not be the right decision if the running engine provides no immediate safety risk. If you shut down a problematic engine in flight you run the serious risk of not being able to get it started again.

Considering that most airports have a bit (or a lot) of extra runway, [EMAS systems](https://en.wikipedia.org/wiki/Engineered_materials_arrestor_system) and often land at the end of the runway, coming in overspeed and burning through your tires and brakes may be safer than cutting the engine and potentially falling short of the runway.
Engine #2 wasn't doing its job either
-------------------------------------

Had the situation just been engine #1 stuck at high thrust, with engine 2 normally controllable, than what you describe would be a reasonable response to the situation. However, that was *not* the case with CX780 -- during approach, Engine #2 was stuck at 17% N1 (or rather below idle) and thus delivering effectively nil thrust.

As a result, the pilots dared not shut down engine #1 until they were safely stopped on the ground.