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Squawks & HeadlinesUnited Airlines makes emergency landing in Idaho

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United Airlines makes emergency landing in Idaho

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POCATELLO, Idaho — A United Airlines 737 flying from Seattle to Houston made an emergency landing in Idaho after one of its two engines apparently shut down. Police say the airplane landed safely at the Pocatello Regional Airport just after 2:50 a.m. Tuesday. The airline said the plane's 116 passengers were waiting at the terminal for a replacement airplane to arrive, which was expected to happen Tuesday morning. The plane also had six crew members. Pocatello airport manager David Allen tells… (bostonherald.com) More...

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sparkie624
sparkie624 3
What is the big deal here.. A light news day... I have had planes to cough an engine Take off and glad to say it never made the news. Things break. If the engine fails, simply road trip a new engine and replace it. We just had one in RIC, No big deal...
PhotoFinish
PhotoFinish 4
Spoken like a true mechanic.
sparkie624
sparkie624 3
Been there for 29 1/2 years... The news media is our worst enemy... That take something routine and make it sound life or death. When I see news articles like that the first thing I ask them is, How many people died? How bad is the plane messed up.. Geez, if I had a news story for every time I had a plane to declare an emergency I could fill the NY Times for a year. I have very little respect for the news media.
PhotoFinish
PhotoFinish 1
Ha!

The other day a Europe-bound United flight returned to their base airport for "pressurization issues". Caught it on the morning news before heading out in the morning.

Got into the car, and the news teaser on the radio was about a "scary/fearful moment at the airport" when in reality "back-up air conditioning unit on the fritz" was closer to describing what was actually happening. I burst into laughter immediately. The other passengers in the car tried justifying the sensationalistic reporting with some passengers were indeed probably afraid.
sparkie624
sparkie624 1
LOL.. That is funny.. Mentioning pressurization, we had one with a pack deferred and climbing through 8000 the LH Pack failed. It was at a hub, so it did an ATB, they swapped to another plane and maint fixed that one.. No big deal...

I remember once time I was on a flight and on approach the captain cycled the gear 3 times... I talked to him afterwards and he tried to deny it... I told him. Look, I have been in the industry over 25 years as a mechanic.. He then said he had a NLG Indication issue.

We kind of laughed and went on... Things happen.
tduggan2010
Tim Duggan 1
Well, if that link is correct, and it is a B737-800, then it was a "former" CAL airplane. And, as far as I know, the "fence" in the CAL/UAL merger is still up -- so that would be "former" CAL pilots.

A bit of background...I'm formerly CAL, by the way...When we had a fleet mix of "Classics" and "Next Gen" the FAA decided that in order to allow a "standard" ability for the airline to train for all variations, the "Next Gen" airplanes (the ones with the MFD screens, similar to the B-767-400 and onward) had to be "downgraded" to show a "traditional" screen, similar to the "Classic" EFIS.

This, in my opinion, was an abortion. Because, I had also been trained on the B-757/767, with the "Differences" training to the B-764, and its MFD configuration.

I think the eventual removal of the B-737-300s and -500s from the fleet mix removed this problem.
PhotoFinish
PhotoFinish 1
Typically one wants to land a commercial airliner full of passengers that is flying on only one engine as soon as reasonably possible.

But I have a question for those more knowledgeable than I, about single engine commercial airliner operation?

How does one engine operation affect the capabilities of the plane at cruising altitude?

(On takeoff a plane past v1 will usually continue takeoff, then come around to land. Also landing doesn't require much power, so the one engine is more than enough.

But at cruise FL, can the plane (in this case the 738) but passenger airliners in general, can the aircraft maintain their altitude with one engine, or does speed have to slow, or altitude decrease to provide enough density for the one engine to provide sufficient thrust to maintain cruise, etc?

I figure that range is limited by fuel that is accessible by the working engine. But if the plane weren't full of passengers, how far can the plane be pushed? Is the aircraft's operation severely limited to finding a safe place to land, or could it continue fairly close to normal capabilities with some limitations (such as altitude, speed or range) if there was not any worry about having engine redundancy?

Thanks in advance for your answers.
sparkie624
sparkie624 1
To answer your questions:

"How does one engine operation affect the capabilities of the plane at cruising altitude?"
At Altitude not too bad, but many times will have to descend altitude to 25,000 because normally 1 pack will be inop and there will be a lot of pressure lost in the bleeds.

"I figure that range is limited by fuel that is accessible by the working engine. But if the plane weren't full of passengers, how far can the plane be pushed? Is the aircraft's operation severely limited to finding a safe place to land, or could it continue fairly close to normal capabilities with some limitations (such as altitude, speed or range) if there was not any worry about having engine redundancy?"
Not correct, They will still have access to the fuel in the other tank. They will have to cross feed fuel for 2 reasons. Range and more so fuel balance. One engine burning normal fuel, and the other not burning will create a heavy wing very rapidly. They should probably be good on the range, but slower.

"I figure that range is limited by fuel that is accessible by the working engine. But if the plane weren't full of passengers, how far can the plane be pushed? Is the aircraft's operation severely limited to finding a safe place to land, or could it continue fairly close to normal capabilities with some limitations (such as altitude, speed or range) if there was not any worry about having engine redundancy?"
I think the first 2 answers can probably cover this one.
PhotoFinish
PhotoFinish 1
Thanks Sparkie for the answer.

I used to think that fuel could easily be crossfed, but had learned that on some airliner(s) [don't remember which, maybe 74 or 75 or a bus] if the middle tank is empty (eg. on shorter flights that don't use the full range capabilities of the aircraft), that crossfeeding is severely limited and that all fuel would not be available to one or the other engine. That is what led me to believe that, in some circumstances, there would be a limited range issue, and as you mention a fuel balance issue, that could lead a pilot to want to set down asap.

So as far as one engine op, you're saying that the plane's speed would be limited flying on just one engine, and altitude might be somewhat limited by having only one pack operational. But that otherwise the plane could operate mostly as normal, just without the
typical engine redundancy that we're used to.

Thanks again for the answer.
sparkie624
sparkie624 1
It really depends on the planes.. I know the 737 series, they can simply flip a switch and cross feed the fuel or transfer from tank to tank. Requires a little piloting skills to juggle it, but it will work... What are you going to do in the middle of the ocean on a 777, 15 hour flt and no where to go and you loose a motor... Simple.. You follow your QRH, and fly the plane.

I know all Boeings can cross feed to any engine. Most boeings use the center tank until empty, however the 727 is different in the fact they use the wing tanks first because of weight and balance.

As far as Airbus, I do not know... I am sure they have perverted some automated system so the crew does not have to think about it.

As far as speed limited, yes, you only have 1/2 the power, so if you have 2 engines at full power producing 20,000 lbs thrust, use a cruise power of 15,000lbs each, you loose one, bring the other to full power to sustain it and now you only have 20,000 vs 30000 total thrust, plus a YAW issue to deal with requiring sustained rudder input and this may in some cases put you into a speed restricted zone.. In some situations, you may have an APR (Automatic Power Reserve) usually just for takeoff that will give you an extra 10% out of the motor.

As for the crossfeed, you can see what I am talking about at the following link.
http://www.b737.org.uk/fuel.htm
tduggan2010
Tim Duggan 1
Sparkie, your answers to Photo were mostly correct, although in the case of a twin, one engine out at cruise altitudes results in a descent NOT due to pack/pressurization issues, but because 37,000 feet (for example) cannot be maintained on just one engine.

For all commercial airliners there is a "drift down" scenario with loss of engine thrust, yes even in the MD11, B747, A340 or A380. (And DC8, B707, or any other 2+ engined airplane still being operated today).

Here's a "down and dirty" PDF for the B737:
http://www.b737mrg.net/downloads/b737mrg_enginefailure.pdf
(Page 6 ^ ^ ^)

For modern jets, the FMC has all the info calculated for the crew, based on actual temperature, altitude and gross weight.

Furthermore, your mention of 25,000 feet with on A/C pack INOP is a dispatch limitation, usually. Depending on the airplane type, the APU can be used for pack operation, but the max altitude for this also varies per airplane.

B738 APU Limitations: http://www.b737.org.uk/apu.htm#Limitations_&_Operating_Techniques

The B737 (all series, based on APU manufacturer) APU can be operated all the way to the airplane's max certified FL, but if you want to use it for pneumatics/bleed air, then the MAX ALT is 17,000 feet.

Of course in the case here of UAL 1172, as in all cases, for any twin when an engine has failed then the rule is divert to the "Nearest suitable airport, in point of time".




Finally, and it's been a LONG time since I flew the B727, but indeed we burn from the Center tank first, then the wings. Just as with most Boeing designs, the Center fuel pumps are "over pressure" outputting, and there are various check-valves built into the fuel system to allow the higher pressure fuel to feed from the Center, until depleted. At which point the "Low Press" lights illuminate, and then the crew switches the pumps off.
PhotoFinish
PhotoFinish 1
Thanks. You guys helped in answering 2 questions.

1. An airliner can safely operate with one engine for long distances (though the SOP is to land at nearest suitable airport). That fact should help assuage passengers' concerns regarding engine reliability.
2. It is possible to figure out when an aircraft experienced engine failure by reviewing the flight log data. There is clearly defined altitude and airspeed driftdown that indicates single engine operation.
tduggan2010
Tim Duggan 1
Yes, PF ('Pilot Flying'! Hah!) you can see on the UAL 1172 track log starting at 01:19 PDT a slow rate of descent begins. That is the drift-down profile. They settled near 28,000 feet before beginning a "normal" descent for arrival at KPIH.

Noting on the Track Log the last portions "Estimated", due to no radar and Tower being closed at that late hour. (The *star* on the Airport Diagram Chart indicates a non-24 hour operation).

It would be interesting to know the cause of the engine failure, as depending on circumstances this has potential to affect ETOPS certification.
samsterflight
samsterflight 2
Well, I'd be tickled pink if I got diverted to PIH or any other off-beat airport as a passenger. What UA needs to work on, however, is providing hotels in cities they don't serve. There are a number of hotels at PIH, although I have no way of knowing how many rooms were available at the time. Nonetheless, one would think that it would not be difficult for UA to call them up from ORD or IAH and buy out all the rooms paying with a credit card.
onceastudentpilot
tim mitchell 1
UAL does serve PIH
samsterflight
samsterflight 1
Tim, I am sorry, the only airline currently providing scheduled service at PIH is SkyWest Airlines (OO) in affiliation with Delta Airlines (DL).
onceastudentpilot
tim mitchell 1
I must have seen the planes being shuffled around due to this maint. issue.
MrWidgeon
Bill Bailey 1
I don't know if WX was in the mix, but we had overnight thunderstorms in southern Idaho between where I live (KTWF) and KBOI.
If any of those were between his engine out posit. and KBOI, then Poky was his best choice.
tyketto
Brad Littlejohn 1
I wonder *where* en route did that engine shut down.. I wonder if they could have made it back to KBOI, where they would have had facilities and crew to accommodate.
RRKen
Kenneth Schmidt 1
It does not look as if that terminal could hold all those people. Even if you included floor space. No food since the terminal closes at 1830 local. And I bet Domino's Pizza was closed too. Chalk it up to an adventure in flying.
PhotoFinish
PhotoFinish 2
Good thing the engine just stopped and didn't fall off the plane and out of the sky. Otherwise we'd have a large mess of mashed patotoes and/or riced potatoes (depending on whether the lost engine were still spinning at moment of impact).
bentwing60
bentwing60 1
The drift down started about 150 NM NW of PIH. They were about 70 miles from BOI, off the right wing and astern. It was closer, I'd guess, but I guess he likes landing at dark airports. See the track and graph for lat. longs of where the descent started. Then you can look it up on google earth. Or a map.
jkirk420
jkirk420 1
Over mountainous terrain we get dispatched under terrain clearance or driftdown, so depending on which segment of the route they were on, the single engine alternate is predetermined based on the single engine net ceiling. We don't do "nearest suitable airport". All the thinking has been done in a cubicle somewhere.
PhotoFinish
PhotoFinish 1
Yeah, hard to tell since they didn't have to change their heading between their climb from Seatyke and their descent into Pocatello.

Since they landed at the nearest suitable airport, it is easy to surmise that they were at least past the halfway point between KSEA and KPIH. Otherwise, they clearly would've returned to SEA if it were the closest suitable airport, just fir that reason alone. Plus, there are the other reasons that that you listed.

If anyone looks up the ATC radio transmissions, please kindly attach a link here. Those transmissions, if available, would provide some insight as to where.
PhotoFinish
PhotoFinish 1
"But I guess he likes landing at dark airports"
Ha!!

BOI does seem possibly closer. I wonder if the mountains in close proximity to Boise are an issue with single engine operation at low altitude. Who wants terrain issues when you're down an engine and only have half the normal power available.
PhotoFinish
PhotoFinish 1
"Pocatello airport manager David Allen tells KPVI-TV that an engine on the airplane shut down and Pocatello was the closest suitable airport to make an emergency landing."

Closest suitable airport ought to take into consideration significant variables such as single engine terrain clearance/driftdown, trailing thunderstorms.

The driftdown began about an hour into the flight and the remaining flight time was up to an additional 40 minutes. If driftdown began at moment of engine failure, then it seems they were slightly closer to their forward heading airport. SEA should've been possible (if thunderstorms aren't an issue) but wasn't the closest suitable airport for that segment in which the engine failure occurred.

But unless the pilots make the decision to turn around immediately when engine issue occurs, each additional minute of flight brings them closer to the eventual pokey destination airport, and less likely will turn around, to avail themselves of the additional resources available at SEA.
tyketto
Brad Littlejohn 1
That's why I was thinking KBOI. If going off of where they started that drift, they could have made a right 180, and been nearly on a 50 - 60 straight in final to the 28s at KBOI. Again, this is if they had the time and the engine would make the distance.

alternatively, if they had remained on their original heading, then turned right, they would have been on roughly a 50 - 60 straight in final to the 17s at KSLC. Again, not knowing how much time they had, they made the right choice. But conditions notwithstanding, it is safe to say that they were within range of other options.