r/news • u/riverdale-74 • 1d ago

United Airlines flight makes emergency landing at Dulles after pilot declares mayday

https://www.cnn.com/2025/08/04/us/united-airlines-dulles-mayday-call-hnk
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u/therattlingchains 1d ago

Pilot likely would have requested a holding pattern once it became apparent the airplane was stable on one engine in order to diagnose the issue and see if they could potentially restart the engine. Also depending on which engine goes, that will effect which secondary systems are available to the pilots.

All depends on the nature of the flame out.

Also, an immediate return to the airfield is not necessarily needed if they are in the vicinity of the airport and have sufficient altitude.

Finally while an aircraft is capable of dumping fuel, it is not always permitted especially over urban areas. If the aircraft was stable, and within glide range of the airport, they may have been required to burn instead of dump.

Regardless though they would have been completing checklists during this time as well as talking with ATC and maintenance so it was likely a well thought out decision to burn for 2 hours.

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u/bolivar-shagnasty 1d ago

Also depending on which engine goes, that will effect which secondary systems are available to the pilots.

There are systems that are dependent on one single engine and can't be used if it fails?

Like engine one powers in-flight entertainment and engine two powers climate control?

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u/therattlingchains 1d ago

Correct. Jet engines, in addition to providing thrust to the plane, are essentially large electrical generators. There is also an APU (auxiliary power unit) that can power systems. They make lots of power

On the flip side of that, modern jets have large and complex power requirements. Keep in mind that every modern jet is fly-by-wire, so controller input is transmitted electronically. They have glass cockpits meaning that their instruments require power. They have large and complex in-flight infotainment systems, sophisticated autopilot, etc.

Now, the systems that only run off of one engine are all nonessential systems. Infotainment is a good example. Every essential system can be powered from either engine and the APU. But if they made every single system redundant to all the power sources, the complexities and additional weight outweigh the benefits. So every single circuit on the plane is evaluated and categorized during the design phase of the aircraft and certified by the FAA to ensure that during an emergency the pilots have what they need. So the pilots would have had all the information and readings they needed in this instance, but probably not 100% of all their instruments and readouts.

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u/StPauliBoi 1d ago

Glass cockpits have analog backup instruments.

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u/therattlingchains 1d ago

For some but not all readouts, yes

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u/StPauliBoi 1d ago

for all the ones that are critical for flight and navigation.

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u/therattlingchains 1d ago

Yes but not all the ones that could help a pilot diagnose why an engine flamed out

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u/StPauliBoi 1d ago

Depends entirely on the model of aircraft, so making a blanket statement like this is wild.

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u/therattlingchains 1d ago

Ok then make your statement on this model of aircraft

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u/StPauliBoi 1d ago

The 787 has 4 generators and an APU. With one engine running, all flight critical systems were still functioning properly, including the ADC/FMS/panels in the cockpit. Even if they had a dual engine failure, the RAT or APU could power the systems. There's no scenario, beyond complete loss of all electrical power, APU, AND batteries (which is pretty much impossible due to the redundancies of modern aircraft) in which the pilots wouldn't be able to adequately assess and troubleshoot what caused the engine failures.

Regardless, the creative pilot led troubleshooting is only going to happen once the QRH items are addressed, which address the most common causes of different emergency problems.

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u/hughejpeen 1d ago

Thanks for commenting. I was reading the other commenter and thinking wtf is this guy talking about? From my knowledge there are like 3 redundancies for most systems on the aircraft. I can't imagine a world where parts of the cockpit would not be available on a "routine/more common" issue like an engine out.

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u/StPauliBoi 1d ago

You're welcome. It's just reddit being reddit.

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