UA1175 emergency landing Honolulu

[PaxBritannica]

Can't find pictures on the news yet, just this Twitter video from the B777 as it heads back squawking 7700:

https://twitter.com/erikhaddad/status/963545018890821632

What happened to the engine? Doesn't look like a smooth ride for the pax.

[KelvinD]

I watched this on Planefinder earlier and I was sure it showed the aircraft as flying from SFO to Honolulu. ?

[PaxBritannica]

Sorry, you're right. SFO to HNL. Seems to have been about an hour out from landing?

[vapilot2004]

Landed without further incident at HNL. Firefighting equipment and personnel standing by upon landing at pilot's request.

Apparently fitted with a pair of Pratts and looks like this aircraft could be one of the airline's oldest triple sevens.

[2016parks]

So, speculating solely from the pix (and text) in the NYT article (link below), how much engine damage was done, was the engine shut down, what airframe risks did not occur, and was a safe landing in doubt?


https://www.nytimes.com/2018/02/13/us/united-airlines-engine-cover.html

[tdracer]

Educated guess based on the damage and the passenger descriptions is a fan blade separation. That'll cause massive vibration - bad enough that it's been known to cause the inlet to depart...

[newvisitor]

From the photos, I would say it is just a cowling failure including acoustic barrel. I don’t believe there is any damage or failure of blades. Kevlar shroud appears intact, if a bit tired and discoloured.

[Octane]

Why would the Captain have chosen to call for a "Brace" landing?
Would it be standard procedure to send the F/O back to take a look?
I suppose these days you could just ask a flight attendant to take a few photos with their phone..

[Propellerhead]

No
Possibly
Maybe

[roving]

The cowls are secured by a number of latches. Given the sophistication of the systems to ensure cowls do not open and become detached in flight, what would have caused such an occurrence?

fXjXJyRtzwc

[FullWings]

what would have caused such an occurrence?
One option is a “rapid disassembly” of parts inside, such as the front fan. Once the cowling has been seriously damaged, air pressure will do the rest...

[Bahrd]

At least one blade looks damaged: https://youtu.be/J2kHchd6XHw?t=219 - see the 219s of a clip.

[jack11111]

I guess that wasn't his first time with the cowling.

[DaveReidUK]

From the photos, I would say it is just a cowling failure including acoustic barrel. I don’t believe there is any damage or failure of blades.

No, it definitely lost one entire fan blade and about a third of the adjacent one.

http://www.avgen.com/ua1175.jpg

http://www.avgen.com/ua1175(2).jpg

[Janner200]

Towards the end of cruise, the NL will be well below red line so to lose the intake and fan cowl doors as well - presuming the fan blade loss was the primary failure - is unexpected. The reports give the impression that the intake was lost early on and not as a result of sustained out of balance during rundown/shutdown or windmill.

[RickNRoll]

There is video of the other side of the engine. It looks like a fan blade has gone through it and damaged enough of the cowling to cause it to come off.

[Rob Bamber]

The kevlar shroud is damaged on its starboard side (away from fuselage). There is interesting scoring on the inside of the intake duct. Would that be caused by fan movement caused by imbalance? Or indicate an object was caught between fan blade tips and the duct?

[Jet Jockey A4]

On the plus side I can tell my airline to stop bothering with Engine severe damage - seperation - fire checklists and training as no other pilots seem to be trained on that flying Boeing...:ugh:

LMAO... You beat me to it.

[underfire]

the brace, brace, brace chant was unusual..

So was all of them holding their cellphones....

(paxbrit...you can change the thread title by going to edit post..advanced)

[aterpster]

Landed without further incident at HNL. Firefighting equipment and personnel standing by upon landing at pilot's request.

Apparently fitted with a pair of Pratts and looks like this aircraft could be one of the airline's oldest triple sevens.

Doesn't matter how old it is. Seems like we were sold "way back when" that all the extra care done for an ETOPS operation would keep this kind of stuff from happening. This wasn't just a loss of oil pressure.

[wiggy]

Seems like we were sold "way back when" that all the extra care done for an ETOPS operation would keep this kind of stuff from happening.

Nah, as I recall we were told it was highly unlikely to happen twice on the same flight......:8

[Loose rivets]

I recall a boss of Alitalia saying on British TV, "We will never cross the Atlantic on two engines . . . ever."

I've always been puzzled by the complete dismissal of Murphy's law. Or indeed the mathematical logic which seems to be saying something alters the Universe when one engine fails and affects the probability of a failure on the other engine.

[NWA SLF]

Did the pilot give the passengers an accurate account of what, in the crews opinion, happened? I watched videos of "passengers preparing to die." The vibration from the missing blade and a half was shaking the plane like moderate chop. If the pilot doesn't say something I'd think the worst. Should be on check list. We have an engine failure but are prepared. The ride will be bumpy the rest of the flight but we will arrive in Honolulu on schedule." Or, "We don't want die any more than you do so we guarantee we will bring this plane into a safe landing in Honolulu."

[Jet Jockey A4]

Did the pilot give the passengers an accurate account of what, in the crews opinion, happened?

Well I would think the captain would have used the PA to give some information on the situation to the passengers to help relieve their fears.

We have an engine failure but are prepared. The ride will be bumpy the rest of the flight but we will arrive in Honolulu on schedule.

Not even the "Sky Gods" of the old days could accomplish that with one engine out and reduced airspeed. :ok:

[FLCH]

Did it “narrowly miss” the ubiquitous school building chock full of youngsters?

[number0009]

The jury will be out for some time. Having an airline line maintenance background I would not be surprised if debris from the nose cone separation caused the missing blade to snap off, damage the other blade as seen in the photos and the compromised fan cowl doors departed. Blade separation shouldn't result in nose cone departure unless already compromised?
......

[ExXB]

Age 23, 4th built , N773UA, part of test program. 1st flight Oct/94 but not delivered until Jan/96. 16th delivered and UA's 10th.

[aterpster]

Nah, as I recall we were told it was highly unlikely to happen twice on the same flight......:8
Yes. And, when one failed it wouldn't have the potential to penetrate the cabin (explosive decompression), rupture the wing, cause some other serious structural compromise, etc.

[newvisitor]

No, it definitely lost one entire fan blade and about a third of the adjacent one.



I stand fully corrected. Only photos available early on were from inside the cabin. Definitely a blade failure, which likely took the 1/3 off the neighbouring blade with it - impact and perforation of Kevlar shroud would be a significant event that could easily have enough residual energy and displacement to tear the outer cowling/acoustic barrel off. Forward momentum of separated blade would focus event on front. Very lucky that blade happened to separate pointing away from wing and cabin. Somebody is going to be running lots of LS-DYNA models.

[Checkboard]

the brace, brace, brace chant was unusual..
It's actually taught that way. If it isn't "chanted", then it's hard to hear AND you get many reports of "The Cabin Crew panicked" when they were actually following their procedures to shout commands.

Having an airline line maintenance background I would not be surprised if debris from the nose cone separation caused the missing blade to snap off, damage the other blade as seen in the photos
What nose damage are you talking about?

https://lh3.googleusercontent.com/U3wRbhHDxrClWyjxYECBnxVGthlF979nIEkF2D1p6frCpqIH7z4vTJ1-3M_l-wbujVVztgIJI9Qw6QENPRPWj5Qiz6NbwLswze-IItXH0N3pJkRL4WRwfqLoWxT6h5HUUHFxoRUuG8KNeVdW4nZhtthwaQMKCmU yHrJE3Y3zvoFRm70EqNqkcu3WQkR4wIxp4aVY6GqgLqhz8xJFCTlAIF-VK0BVfvO-1_lHnfmemaEMMEZVhBVp9yGhi2n0zCs6aqtXS0HqQqX2dDK0ruQw99N8h89D ZRGakpp9Nz0sLF_KGQ8ig44H_PEetbh-N-ReHjPOmq769ENzlBC6X5mvvfn7odNFp_3HdaTiAeARNxyNv0NaXNoOajJieP u3ttKXn4nHyaiDvuNY3NgccPiWe_5zk6bMgOGEcVshuhiXyTN4FfVAtbsD4b 5Fb8DgzHwCpf7cFr8uujP868c6jyTBI5rMiUqF0YL4PuZp0S61xxx9BWb1gb ne1h0p7cH8qkfZGg-d_vLKxqGxEcn7Ewio8IMO5x4QQ8WFZgNx6xy2rp4UiOSr-G_MWohha2Pvr28g1io1i5IJkyPsbTsCZtSN8kE4PVjUqqdagzKGDkA=w548-h414-no

but we will arrive in Honolulu on schedule. Not even the "Sky Gods" of the old days could accomplish that with one engine out and reduced airspeed. :ok:
Well, they were nearly at top of descent, and if they were running a few minutes early - perfectly possible. ;)

[NWA SLF]

Well I would think the captain would have used the PA to give some information on the situation to the passengers to help relieve their fears.



Not even the "Sky Gods" of the old days could accomplish that with one engine out and reduced airspeed. :ok:

Checkboard took the words out of my mouth. Was near the top of descent. Engine failure. Landing very likely to be sooner than planned unless descent speed sets up abnormal control/vibration.

[PaxBritannica]

the brace, brace, brace chant was unusual..

So was all of them holding their cellphones....

(paxbrit...you can change the thread title by going to edit post..advanced)

Thanks.

I've been once in a cabin with the crew yelling 'Brace! Brace!" and it was like being hit with bricks. I bet the pax were surprised to say the least.

[old,not bold]

I make no apologies for being sceptical about ETOPS, which has always struck me as an accountant's idea, and in that spirit I wonder how things might have worked out had this particular incident occurred on an ETOPS B777 at a point 180 minutes from the nearest diversion field, calculated for single-engine operation but otherwise clean.

Was the post-incident performance worse than that used for ETOPS planning? Did this failure compromise any ETOPS significant systems? I don't know, just asking.

[Checkboard]

which has always struck me as an accountant's idea
Well, it's really an engineer's idea. As engineers have improved the power and reliability of engines, airlines have been able to take advantage of that.

Which would you rather be on? A 777 with two modern, computer controlled and remote monitored engines or a 707 with four smokey turbojets with only 15% of the thrust and controlled by a hydromechanical unit using ten times the moving parts and serviced at whatever intervals?

[Checkboard]

All command courses should include the video reconstruction of the BA B747 that discovered flying through volcanic ash is not good for your engines nor your stress levels.

Mmmm. When the Purser came into the cockpit, Moody pointed at the instruments and said "Get the picture?!" (Intending to indicate the loss of all engine power, perhaps.)

The Purser went back to the cabin with no idea what was going on, wether a ditching was possible, or they were going to land. When passengers started donning lifejackets he joked "You must know more than me."

So .. maybe not.

[WindSheer]

Some pilots will be stronger than others coping and communicating under pressure. We have no idea which bracket this team fall under so don't undermine what they have achieved here.

Cabin Crew - in this day and age of everyone thinking they know best via social media, yell, scream and command your customers attention! It will help to offset some of the adrenalin. Because guess what, cabin crew are human and have families, and will probably never see an engine failure either.

There are some class A IDIOTS posting on this forum!

[Checkboard]

Cabin Crew - in this day and age ... yell, scream and command your customers attention!
Or follow your training, be professional at all times and don't panic people with screams from the professional CC. ;)
It will help to offset some of the adrenalin. Because guess what, cabin crew are humanSo will good training and experience.

When was the last time you told firefighters to yell & scream and worry about their adrenaline?

[dogsridewith]

A USA major network TV account this am showed an in-plane video of the bared engine rocking, with the windmilling fan center moving like a drill bit chucked up a bit crooked. It included the "...plane was shaking like a washing machine..." expression heard after a prior one of these sorts of events some months ago.
One male passenger said the engine was progressively loosing pieces, with bolts hitting the fuselage.

[lomapaseo]

Single engine failure, fan blade contained within the engine cases. Subsequent debris out the inlet and fan discharge. Engine rundown safely with no fire or distress to its mounting.

Damage to engine cowling expected and confined to the affected engine. Remaining airworthiness questions are to aircraft structures or systems.

[Herod]

Generally the cabin crew don't "scream". Yes, they shout. "jump and slide" or "one leg, then the body" or similar. Would you sooner, in the chaos of an emergency hear "excuse me, could you possibly jump onto the slide?". It's called taking command of the situation.

[Gauges and Dials]

The cowls are secured by a number of latches. Given the sophistication of the systems to ensure cowls do not open and become detached in flight, what would have caused such an occurrence?


Based on the information available to us at the moment, we can conclusively state that what caused the occurrence was that something went wrong. :ugh:

[rxsazabi]

Aircraft is registered as N780UA, it went to China, Hong Kong to do 'C check' maintenance and modifications like all United aircraft. Not sure if the maintenance was done properly.

[tdracer]

This mishap is B-777.

?? Didn't TBC & FAA change the certification testing
----> cost $aving
-- prior to the B-777 cert' ??

Earlier FLIGHT TEST program, B-767, ~ 1982:

One of the most spectacular flight tests
aboard VA3 [aka B-767 JT9D-7R4G ? N602UA]
was the intentional shedding of ice,
a cowl-ring & Bullet-dome full of natural ice
into the LHS Engine -- then drive back to BFI
with that damaged engine still operating
(lots of damage, & shaking)

That video -- fixed camera (as flight test instrumentation)
was perhaps the most impressive test result.

Difference : planned DAMAGE inflight to test aircraft-engine,
and flight back-to-base
proving that engine would hold together.

.

Big difference between icing testing and fan blade out. Fan blade out testing has ALWAYS been done on a test rig (at least since the JT9D). Not only is it considered excessively dangerous to perform in-flight (what if it's not contained), it would be impractical to apply the level of instrumentation and video on a flight test that they use on the test rig. BTW it was a JT9D-7R4D (the -7R4G went on the 747)

I don't recall any specific issues when they did the fan blade out testing on the PW4084 during the 777 certification. The GE90 was a different issue - the blade was contained, but the inlet and a lot of the engine accessories broke loose due to the massive vibrations. They had to beef up the inlet and accessory attachments as a result of the test (and the FAA updated their requirements for fan blade out pass/fail to address the failures on the GE90). Once the inlet is gone, it's not surprising the aero loads combined with the continued vibrations caused more of the nacelle to depart. Obviously no first hand experience, but apparently the aircraft vibrations after a fan blade out are horrendous (even after the engine has run down) - stories of flight crew nearly unable to read the gauges/displays things were shaking so bad, and the FAA updated the regulations a while back to require various parts of the aircraft (especially the remaining engine(s) ) can withstand several hours of the extreme FBO vibrations.

Damage to engine cowling expected and confined to the affected engine.
Actually no, per the regulations the inlet is not allowed to come off - big bits departing the aircraft is a no-no since it can damage other structure (like the tail surfaces). My former co-workers will have some serious work to do to make sure the inlet and such stay put in case there is a future PW4084 fan blade out event.

[stilton]

Well, it's really an engineer's idea. As engineers have improved the power and reliability of engines, airlines have been able to take advantage of that.

Which would you rather be on? A 777 with two modern, computer controlled and remote monitored engines or a 707 with four smokey turbojets with only 15% of the thrust and controlled by a hydromechanical unit using ten times the moving parts and serviced at whatever intervals?


A 707 without a doubt, it can fly a lot further
after losing two engines

[4 Holer]

I WOULD RATHER BE IN ANY 4 ENGINE JET ANYDAY WAY OUT OVER THE PACIFIC...... If they were 180 minutes ETOPS they would ALL be dead today... Fact
Only a matter of time until a big twin is in the water way out in the middle of nowhere...

[tdracer]

I WOULD RATHER BE IN ANY 4 ENGINE JET ANYDAY WAY OUT OVER THE PACIFIC...... If they were 180 minutes ETOPS they would ALL be dead today... Uninformed Opinion

There, fixed that for you...

[4 Holer]

Tick Tock, splash..... just wait we will meet again......4 holes for long haul.

[Highway1]

Tick Tock, splash..... just wait we will meet again......4 holes for long haul.

I stand to be corrected but the only twin that has had both engines stop over water ran out of fuel - in that case you could have been on a B52 with 8 engines and it wouldn't have helped.

[b1lanc]

Well, it's really an engineer's idea. As engineers have improved the power and reliability of engines, airlines have been able to take advantage of that.

No, it's a business decision. Wonder if the P&W NEO EAD would have been issued if the NEOs had four engines?

[Capn Bloggs]

A 707 without a doubt, it can fly a lot further after losing two engines
Very good! :D

[Volume]

Age 23, 4th built , N773UA, part of test program. Most probably no single part on the pylon will be original anymore. Engines and nacelles rotate through the fleet, you normally replace items which need repair with parts from stock, and after the repair you put the item onto another airplane.

[arketip]

Tick Tock, splash..... just wait we will meet again......4 holes for long haul.

Are you hoping for hundreds of people to die to be proven right?

[vapilot2004]

Doesn't matter how old it is.


Well you're right, Aterpster, it shouldn't. The year of manufacture was interesting to me, being so close to roll out, and of course the engines are going to be newer than the airframe as it is.

Seems like we were sold "way back when" that all the extra care done for an ETOPS operation would keep this kind of stuff from happening. This wasn't just a loss of oil pressure.

This is not the first time United has been on the ETOPS merry go round, with one not so long ago over the Pacific. As we know, statistics are what run this particular show and theoretically backs up what "we were sold".

[old,not bold]

......Which would you rather be on? A 777 with two modern, computer controlled and remote monitored engines or a 707 with four smokey turbojets with only 15% of the thrust .....

But that isn't the choice, is it? I think that my last flight on a smokey 707 must have been in 1971, but I'm not sure.

I would rather be on a modern aircraft with four modern, computer controlled and remote monitored engines, and luckily for me they exist and I have that choice available, at least on long over-water sectors, so that when one of the modern, computer controlled and remote monitored engines decides to pack up or, as in this case. shed most of its front end, there are 3 more instead of just the one.

One of my problems with ETOPS, apart from the imminent prospect of approval for 420 minutes s/e diversion time (ie 7 long hours over the freezing Southen Ocean hoping the remaining engine won't suffer a failure and that the aircraft's remaining ETOPS significant systems** will continue to perform in accordance with a set of statistical assumptions), is the way that ETOPS maintenance procedures are designed to make an ETOPS aircraft safer than one that's not ETOPS certified. By and large, I would rather that the extra care is applied to every aircraft used on commercial air transport. The regulations essentially acknowledge - admit - that this is not the case.

** On that subject, has anyone ever tested the assumption that the ability to maintain 3% halon concentration in the cargo hold for 7 hours continuously (in the worst case) will suppress a fire that would otherwise spread to other areas including the cabin? As a layman, I don't get it. What is "suppress" supposed to mean in this context? It isn't "extinguish"; if it were they would say "extinguish", wouldn't they? What happens, exactly, when you "suppress" a fire for 420 minutes? Fires consume fuel, if they don't go out they spread.

[Loose rivets]

When I went all probability-philosophical back there, I didn't even introduce the added burden on the remaining engine. The concept of hundreds of people being over non-survivable ocean for hours on one engine is something dreamed up by people that are sitting in a warm room - but drowning financially.

That Alitalia executive's heart was in the right place, but then, things were not always as rosy as we'd like to believe.

The 727 drift-down comes to mind, with its subsequent hosing in of fuel.

[scifi]

I wonder if Sully would have got wet if he was flying 4 engines. Maybe so, and the loss of more Geese.

[Sailvi767]

I WOULD RATHER BE IN ANY 4 ENGINE JET ANYDAY WAY OUT OVER THE PACIFIC...... If they were 180 minutes ETOPS they would ALL be dead today... Fact
Only a matter of time until a big twin is in the water way out in the middle of nowhere...

How do you call this fact. The aircraft would have flown just fine for 180 minutes. Would have flown fine for decades statistically on 1 engine.

[aterpster]

Appears in today's federal register:

[TURIN]

But that isn't the choice, is it? I think that my last flight on a smokey 707 must have been in 1971, but I'm not sure.

I would rather be on a modern aircraft with four modern, computer controlled and remote monitored engines, and luckily for me they exist and I have that choice available, at least on long over-water sectors, so that when one of the modern, computer controlled and remote monitored engines decides to pack up or, as in this case. shed most of its front end, there are 3 more instead of just the one.

One of my problems with ETOPS, apart from the imminent prospect of approval for 420 minutes s/e diversion time (ie 7 long hours over the freezing Southen Ocean hoping the remaining engine won't suffer a failure and that the aircraft's remaining significant systems will continue to perform in accordance with a set of statistical assumptions), is the way that maintenance procedures are designed to make the aircraft safer than one that's not ETOPS certified. By and large, I would rather that the extra care is applied to every aircraft used on commercial air transport. The regulations essentially acknowledge - admit - that this is not the case.
FAA now assert ETOPS standards for all large aircraft. That's why ETOPS now means ExTended OPerationS instead of Extended Twin OPerationS.

[rog747]

FAA now assert ETOPS standards for all large aircraft. That's why ETOPS now means ExTended OPerationS instead of Extended Twin OPerationS.

well all large new build designs are twins except the 380 and 747-8i

[NWA SLF]

Are statistics available showing how many 3 engine wide bodies (DC-10, MD-11, L1011) suffered two engine failures in flight and landed due to one engine remaining? I know of the Eastern maintenance issue where they lost all 3 but were able to get one restarted after cooling enough to free the engine so it would turn but it was going down if not close to an airport). I also know of multiple 747 hull losses with 2 engine failures on one side (ElAl, China) and numerous 707/DC-8 losses due to two engine failures. Wasn't the 767 finally allowed ETOPS due to proven reliability of other wide bodies plus domestic flights. Notice how many fewer fatal accidents there have been as the industry has moved from quads to twins. Engine problems we see in the latest designs are a concern - pushing the envelope too far in order to compete on fuel economy just like the JT9D was a stretch on the first 747s.

[EDML]

Well, Eastern L1011 was a maintenance error (missing gaskets) - that would have been the same on 2,3 or 4 engines.


All losses of 2 engines on the same side of a 4 holer have been connected and caused by an uncontained failure of one engine (or ripping of one engine and hitting the other one).


I never heard of any failure of 2 engines on a modern jet on the same aircraft due to different reasons. It is either connected (uncontained failure) or maintenance related (Eastern L1011).


Marcus

[panda-k-bear]

FAA now assert ETOPS standards for all large aircraft. That's why ETOPS now means ExTended OPerationS instead of Extended Twin OPerationS.

And there was me thinking it meant Engines Turn Or Passengers Swim :8

[oldchina]

Polar Bear Repellent.

Is it required for some ETOPS?
Would you feel better having it ?
Get out of your comfy chair and imagine. Are they hungry ?

[ethicalconundrum]

Since this thread has migrated a bit into the 2 vs 4 engine and ETOPS concerns, I will share a little of what likely influenced decisions on 2 engine jets over the past decade. I'm an EE by trade, but much of my work involves load determination and speeds/feeds. I've been using some interesting tools which have been developed very well since the late 80s in stochastic process(probability), and Poisson distributions.

Without going all into the math of it, the stochastic process attempts to build a model of two or many more independent, and random variable events or outcomes. If we consider the failure of engines to be both random and independent(one engine not taking out the other, contaminated fuel, etc) events, there is a model using the MTBF that will provide an index or deflection point that will give some indication of likelhood(I know, that's a lot of qualifiers).

I did a quick google(because I had no idea) of jet engine MTBF and came up with a number of inflight shutdowns of less than 0.01 per 1000 hours for EDTO > 180 min, 0.02 per 1000 hours for EDTO < 180 min, and 0.05 per 1000 hours for EDTO < 120min. Note, that this is not really the MTBF, but is the best I can find without going wild. Based on independent probabilities for a flight of 3 hours, I came up with a probability of 1.6e-9 (.0000000016).

While this sounds very small, taken into account all the various flight events we have around the world each year, this is a reachable event. I'm actually kind of surprised it hasn't happened - yet. I suspect there is not an actual independence at play, because should one engine fail on a jet, the flight will not typically proceed as planned, and the change in event duration window would be cut way down, unless over water. Even in cases of over water, the destination may be inland, and I'm guessing that an engine shutdown over water would mean diversion to the closes landing point, notwithstanding destination. So, that - and several other things would certainly influence the decline of the dual engine failure probability.

[lomapaseo]

I never heard of any failure of 2 engines on a modern jet on the same aircraft due to different reasons. It is either connected (uncontained failure) or maintenance related (Eastern L1011).


Marcus

Well a few have occurred. Most were not in ETOPs operation (e.g birds).

Taking into account independent failures the quad is 2.5 times more (than a twin) likely to lose two or more in an ETOPS flight. However the numbers are so low that all other failure conditions beyond the powerplants alone drive the FEDs to make rules.

The passenger can pick and choose but their choices are getting more and more limited by the science of the aircraft designer and the operator's needs

[BRE]

An uncontained failure can take out other parts. Would you rather have two or four of these potential bombs?

[BRE]

A 707 without a doubt, it can fly a lot further
after losing two engines

Is that so?

My understanding is that in both cases, for the V2 scenario, a single engine out is considered. This means that a 4-holer must be able to climb out safely on three engines, whereas a twin must on one. Hence one engine on a twin has considerably more thrust reserves than two on a quad.

[number0009]

Single engine failure, fan blade contained within the engine cases.
Anybody else notice that close to 90% of the inlet nose cone is missing? Not a simple blade failure.
......

[lomapaseo]

Anybody else notice that close to 90% of the inlet nose cone is missing? Not a simple blade failure.

The photos show one complete blade and the tip of another. It's the tip that skids forward into the soft skin of the cowl and cuts a slash in the inner cowl.
It's the extent of these slices that is important and the ability to sustain the boom noise and the rundown vibration.

[old,not bold]

FAA now assert ETOPS standards for all large aircraft. That's why ETOPS now means ExTended OPerationS instead of Extended Twin OPerationS.Hmmm.....not quite as simple as that, in my understanding (which is getting increasingly addled); EDTO covers all aircraft, ETOPS regs cover twins as a subset.

If someone comes along to say that's not right either I won't be at all surprised. But for the moment, here's EASA's take on it all;

AMC 20-6 rev. 2
Extended Range Operation with Two-Engine Aeroplanes ETOPS Certification and
Operation (https://www.easa.europa.eu/sites/default/files/dfu/Annex%20II%20-%20AMC%2020-6.pdf)

[vapilot2004]

I recall it was decided nearly two decades ago that engine reliability no longer drives the ETOPS argument of 2 v 4 engines. Considerations of inflight fire suppression capabilities and weather diversions outweighed the turbine reliability concerns. Can anyone point to an incident or accident where an ETOPS twin lost both power plants due to engine failure? I cannot.

Thus, the statistics hold true where they state: there's a small chance you might lose one, but the odds go well into the stratosphere when we run the probability on losing two. ETOPS certified aircraft systems, capabilities, procedures, and maintenance practices are all designed to handle the loss of one engine with practically no demonstrated loss in safety margins.

I guess for some, the question remains, are we on borrowed time, or is this issue not worth debating considering the reliability of modern turbine engines?

[ethicalconundrum]

The other part of the probability equation is the risk-based management of outcome. Back in my field, if one of my networks goes down, we have a workaround that may delay some users from getting their data in 1/2 second, or 1.5 second. Meh - our ability to accept the loss of one system is much more tolerant than aviation. There used to be several quality ideals that were put forth, like SixSigma, and Five-9s, etc. Most of them have been replaced by the moving target of continuous process improvement. Aviation uses this, and it's one of the foundations of the US aircraft AD system.

Lastly, the two things about probability is that its a best guess, based on what we think is valid input data. In many cases, choosing valid input data is critical, and margin bands for probabilities(sometimes called the R^2 value), or chi-square of variability is an important factor(low R^2 factor means that the measured statistic has a wide variability, or poor prediction of event(s)). Second, all probabilities are not static! This is a common failing. Process control, product changes, systemic changes, and more constantly change the probability data. So, what I gave only a few minutes ago, may not be remotely accurate once the latest gen engines hit the market. A whole new plot of data will be done for that.

[ph-sbe]

I also know of multiple 747 hull losses with 2 engine failures on one side (ElAl, China)

The ElAl incident in Amsterdam was not caused by an engine failure. It was caused by fuse pin failures. All four engines were producing full thrust and when the pins failed the number 3 engine broke free and slammed into the number 4. In that process, the leading edge of the wing and some hydraulic systems were damaged. The crew was able to line up with the runway, but lost control when deploying flaps.

Engine failure had nothing to do with this.

[DaveReidUK]

The ElAl incident in Amsterdam was not caused by an engine failure.

Nor, indeed, was the other cited accident (assuming it's a reference to the China Airlines -200F).

[Start Fore]

Still, I'll stick to my 4 burner ta very much.

[NWA SLF]

You may not call it an engine failure but the FAA did. Specifically they stated that the loss of 2 engines on one side of a 4 engine airplane should not result in loss of control. It did not matter to them if the fan failed, turbine failed, or in the China and ElAl cases the entire engine falls off. The fuse pins were designed to let the engine fall off in the case of a very hard landing preventing a fire. Due to a design error they failed resulting in 2 hull losses and one major damage (NWA failure on landing in Tokyo). But we are getting way off the subject. I remember responding to somebody's statement that 3 engine airliners were going to return due to recent engine failures (not hull losses) on twin engine wide bodies - after 30+ years of wide body twins flying with no hull losses due to both engines failing. However there have been hull losses of 4 engine planes resulting from loss of power from both engines on one side.

[Bahrd]

Without going all into the math of it, the stochastic process attempts to build a model of two or many more independent, and random variable events or outcomes. If we consider the failure of engines to be both random and independent(one engine not taking out the other, contaminated fuel, etc) events, there is a model using the MTBF that will provide an index or deflection point that will give some indication of likelhood(I know, that's a lot of qualifiers).

I wonder whether it makes sense (in order to increase independence) to mount the engines drawn from different production lots.
The recent PW's troubles seem to suggest so.

[Hokulea]

My apologies for posting here, I'm not a pilot and can't add to the technical discussion, but thought some might be interested in some footage that has been shown on a local TV station regarding the engine that failed. I haven't seen this posted before:

Flight makes emergency landing - Honolulu, Hawaii news, sports & weather - KITV Channel 4 (http://www.kitv.com/clip/14126458/flight-makes-emergency-landing)

At around the 1:30 mark you get a good view of the front of the failed engine while still in flight. To my completely untrained eye, the engine has been shut down and the blades are windmilling but causing a lot of vibration.

Not sure if this is useful but thought I'd share in case it hadn't been seen by people on this thread before. Thanks for indulging me.

[Capn Bloggs]

Impressive, Hokulea. Also for the effect on the pax.

[rog747]

Hokulea

goodness that vibration is something - thankfully occurred near the end of the flight and HNL was nearby - i would not want to be on that for any longer than ness to get down to the ground PDQ
had it happened halfway across the pacific with 2-3 (ETOPS) hours of flying time it would have been awful for the pax & crew

[tprop]

Looks like the camera is shaking a lot more than the engine.

[Hokulea]

I wouldn't be suprised if the camera was shaking. Vibrations in the airframe and the photographer being a bit scared might do that. But compare the engine with the side of the window frame. The engine was vibrating significantly.

[stilton]

Is that so?

My understanding is that in both cases, for the V2 scenario, a single engine out is considered. This means that a 4-holer must be able to climb out safely on three engines, whereas a twin must on one. Hence one engine on a twin has considerably more thrust reserves than two on a quad.

Apples and oranges, you’re describing a completely
different situation, engine failure on departure in a twin
nearly always mandates an immediate return with a possible
exception of weather minimums being adequate for departure
but not a return in which case you’re going to your
departure alternate

And yes, of course performance on one in
that case will be better than a four engine aircraft that
has lost two

I was referring to the en-route phase, a long way from
land or over hostile terrain I’d be far happier in a B707
that has lost two than ANY twin that is down to one
operating engine

[mustafagander]

It must also be kept in mind that the gradients required to satisfy the T/O climb segments are significantly less for twins than for quads.

[stagger]

I was referring to the en-route phase, a long way from
land or over hostile terrain I’d be far happier in a B707
that has lost two than ANY twin that is down to one
operating engine

Can a 707 stay airborne on 1 engine? If not then in both cases - either with the 707 flying on 2 engines or the twin flying on 1 engine - you are still just 1 engine failure from getting wet.

And even putting aside differences in engine reliability between old turbojets and modern turbofans - you've got double the chance of having that further engine failure in the 707.

[lomapaseo]

It's a little worse than that when you consider your chance of a any engine failure on a quad is increased, then after that you have more combinations etc.

But it all fades to nil when you consider the chance of you being on a long-haul B707 today are extremely low :}

[Heathrow Harry]

"The cowls are secured by a number of latches. Given the sophistication of the systems to ensure cowls do not open and become detached in flight, what would have caused such an occurrence?"

this must be different from the Delta 777 I was on at LHR last year when the guys trying to close & lock the cowling appeared to be using a hammer, a small screwdriver and a Swiss Army Knife - and lots of sweat.

[Volume]

We are not talking about the cowl doors here, but about the fixed inlet cowl which is bolted to the fan case with probably 100 bolts. This can not be opened and has no latches. Once this part is missing, air flows under the cowl doors and breaks them, irrespective of the latches.
The big question is: Did the nose cowl fail and was partly ingested, damaging the fan, or did a fan blade fail and destroy the noce cowl ? Not easy to tell from the pictures.
As there is no debris visible behind the fan, I tend to believe in the second scenario, but this is just an educated guess.

[Zeffy]

Associated Press quotes NTSB.

Broken fan blade cited in United jet’s engine failure https://www.seattletimes.com/business/broken-fan-blade-cited-in-united-jets-engine-failure/