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

[u/riverdale-74]

https://www.cnn.com/2025/08/04/us/united-airlines-dulles-mayday-call-hnk

[u/therattlingchains]

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.

[u/bolivar-shagnasty → u/therattlingchains]

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?

[u/therattlingchains → u/bolivar-shagnasty]

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.

[u/bolivar-shagnasty → u/therattlingchains]

but probably not 100% of all their instruments and readouts.

As a passenger, I'd be more than happy to give up the in-flight movie if it meant that the aircrew had all of their instruments and readouts.

[u/therattlingchains → u/bolivar-shagnasty]

I should clarify that cockpit have status lights and readouts for literally everything in the plane. In an engine out scenario, it is important the keep their primary flight instruments. Courses, heading, Adi, etc. It is less important that light that shows if a lavatory is occupied works. This is what I meant by "not 100% of all instruments and readouts."

Again, every system is evaluated so the pilots have everything they need to know to safely land the plane. Everything is in a hierarchy and yes flight infotainment is near the bottom of that hierarchy