3-engine 747 NAT crossings becoming the norm

[Meikleour]

Notso Fantastic: Did you ever read the AAIB final report on the BA incident?

It was highly critical of the crew`s fuel management ( ie. a BA derived procedure at variance to the Boeing procedures) which led to the eventual declaration of an emergency and diversion into MAN!

[Notso Fantastic]

I'm well aware what went on having flown those 747s for 8 years. What happened at the end of the flight bears no relevance to the decision to continue the flight. The crew made an error in fuel management about 9 hours later! Once again, the crew received no criticism from their flight manager for the decision to continue. A small mistake with more ramifications in the last hour does not affect the decision taken out of LAX.

[Iron Duke]

When operating under "procedural" clearance, any inability to comply with that clearance (i.e. driftdown) requires a distress call on ATC and 121.5.
From 747-200 days I cautiously recall 3 engine cruise involves roughly 14% increase in fuel burn ? If fuel is OK and clearance re-negotiated I cannot see why they should not continue ... they still have 1 more power plant than ETOPS A/C ...

I.Duke

[jackieofalltrades]

Did you ever read the AAIB final report on the BA incident

Does anyone have a link to the report for this? I have heard about it, but don't know the actual dates and flight number, so don't want to spend ages searching numerous pages looking for it.

[49th]

re: #8

John Deakin wrote about The Dreaded Three-Engine 747:
http://www.avweb.com/news/pelican/193882-1.html

[Notso Fantastic]

I hadn't seen that article, but it is a very practical, sensible and pragmatic approach to the issue. Even airline pilots who haven't flown the 747, particularly the 400, don't have knowledge of the power and systems redundancy of the 747, and quite what an amazing aeroplane it is, and they tend to recoil at the prospect of such continuation- hardly surprising when they've been flying twins and the loss of one is a sizeable problem. The experienced 747 pilots know deep in their water that the odds of losing one are small, the odds of losing a second are infinitesimal. If the damage is confined to a stall or minor fault like oil loss, you have no problem whatsoever. I'd still rather be in a 3 engined 747 than a 3 engined Tristar or MD11!

[SeenItAll]

Notso:

I am not trying to be cheeky here, but loss of oil in one engine may not be an instance that is confined just to one engine. Remember the EAL L1011 that had the oil changed in all three of its engines by one mechanic, who forgot to reinstall new O-rings on each of the engines' drain plugs. Low oil indications in one engine were quickly followed by identical indications in the other two.

I am also confused about your statement that you are happier on a 3-engine 747 than on a 3-engine DC-10 or L1011. Can you explain why you think the former is safer?

[TopBunk]

Just to say that I totally agree with NSF.

I have flown BA B74-400's for about 7,000 hours in both seats (and with NSF on 25/8/1998 if he wishes to check his logbook).

The B747-400 has incredible systems redundancy, and hence his comment about ...

I am also confused about your statement that you are happier on a 3-engine 747 than on a 3-engine DC-10 or L1011. Can you explain why you think the former is safer?

is probably because the performance and redundancies offered by a 3-engines B74-400 is (in our view) still greater than that of a fully operational DC10, MD11 or L10-11.

Remember the EAL L1011 that had the oil changed in all three of its engines by one mechanic, who forgot to reinstall new O-rings on each of the engines' drain plugs.

In that scenario, it doesn't matter how many engines you have, surely?


Simply, it is the QOTS with good reason.

[Notso Fantastic]

Ah Narita! Never liked the place. Upside down time, go back to bed after breakfast, always cold, very weird food!

Why is it when pilots say something is dangerous, they get listened to, and when they say something is safe, non-flyers and simmers and non-747 pilots rise up to howl 'it's not safe!' as if they know better? Pilots who fly the 747 have a better understanding of the machine in relation to practical operational experience, having previously flown twins or trijets. Why is it I used to find myself at 30W en route to Canada on 2 (French) engines, and that's OK- 180 minutes ETOPs, and many pilots and even the FAA have decided a 747-400 on 3 is not advisable? In the early 747 days, I must have had half a dozen spells on 3 engines. The -400 was fantastic, in 8 years not once, and a better T/W ratio and more redundancy to boot! I'll like the 777 as much when Boeing puts 2 more donks on it.

[Espada III]

I'm confused!

I understand that two engines (say B777) is more efficient to operate than four engines (say A340), but when safety and efficiency are factored in, an A340 on three engines is inherently more safe than a B777 on one engine. This implies that if one engine fails on a twin, the response is to get down asap (within ETOPS rules presumably) whereas a three engined A340 or B747 could simply continue with the flight.

So - what am I missing?

[Groundloop]

So - what am I missing?

Cheaper operating costs of a twin more important than "safety in numbers".

Also the number of times a twin has to divert because of an engine failure is so small that overall the odd diversion is far cheaper than operating all flights with a 4-engined aircraft.

[Meikleour]

Notso Fantastic: You have skirted around my point again!

The decision which was valid at the time it was made was contingent on the crew being able to successfully manage the fuel distribution in order to safely finish the flight. This they patently failed to do due, in main part, to the then BA derived procedures.

I have 13 years on the B747 and was a TRE so I found the AAIB conclusions quite enlightening to say the least. I was never questioning the safety of flying on on 3-engines. At the end of the day, 400kgs of fuel in one main tank plus a MAYDAY declared plus diversion short of the intended destination whilst all the time having sufficient fuel remaining can hardly be claimed as a satisfactory operation!

[SeenItAll]

While I understand that 3-engines on a 747 is perfectly safe for extended flight. What I am querying is why this is considered safer than 3-engines on a DC-10 or L-1011. With the two 3-holers, you can lose one and still be quite safe (although likely not as safe as losing one on a 747), but if you are on a 3-engine 747 and lose an additional one so you are down to two, my understanding is that you are likely in an extremely difficult situation -- and that depending on terrain or possible distance from a suitable airfield, possibly catastrophic.

While certainly the possibility of this occurring is rare, in my earlier post I just wanted to note that because of possible linkages between the ill-health of one engine and the likely health of the others (e.g., maintenance error in oil plugs - EAL, ice blocking fuel pumps - BA, fan blade failure taking out adjacent engine QF, etc.), the conditional probability that another engine will fail given that one has already failed is much larger than the unconditional probability that any engine will fail.

Please note that I am not disputing that the 747 may have additional features (e.g., 4 hydraulic systems rather than 3, etc.) that make it absolutely more secure. I am only wondering about whether given that one of its significant systems has failed, it remains more secure than a jetliner designed with this reduced number of systems -- but which has all of them operating.

[SeenItAll]

Quote:
Remember the EAL L1011 that had the oil changed in all three of its engines by one mechanic, who forgot to reinstall new O-rings on each of the engines' drain plugs.

In that scenario, it doesn't matter how many engines you have, surely?

Actually, I think it did. If my recollection serves me right, the first engine to indicate low oil was the center one, so it was shut down in-flight and the return commenced on Nos. 1 and 3. But as it progressed, both Nos. 1 and 3 showed low oil but were not shut down, and so they failed. While gliding dead stick, the crew was able to get No. 2 restarted (because it still had some oil in it), and gained enough altitude to make it back to MIA. My understanding is that once on the taxiway, No. 2 then permanently gave up the ghost.

Thus, having more than two engines allowed the crew to handle their failures diversely, and this may have been the key to a successful outcome.

[Groundloop]

While I understand that 3-engines on a 747 is perfectly safe for extended flight. What I am querying is why this is considered safer than 3-engines on a DC-10 or L-1011. With the two 3-holers, you can lose one and still be quite safe (although likely not as safe as losing one on a 747), but if you are on a 3-engine 747 and lose an additional one so you are down to two, my understanding is that you are likely in an extremely difficult situation -- and that depending on terrain or possible distance from a suitable airfield, possibly catastrophic.

the conditional probability that another engine will fail given that one has already failed is much larger than the unconditional probability that any engine will fail.

SeenItAll, you may have just answered your own question. Losing a second engine on a 747 still leaves you with two - but losing a second on a TriStar, DC-10 or MD-11.... !

[Notso Fantastic]

Thankyou- said far more eloquently than I could! I have 18 years on all models 747 except -300, from 1977 when engine failures were 'not unusual'. At that time, I had approximately half a dozen IFSDs for various reasons, mostly unrecoverable surges. Never with a problem that extended further to other engines.
We have to be careful we don't go striving for academic statistical nuances here, rather stick to practical experience. Incidents such as El Al/AMS double IFSD are exceedingly rare. I believe it right to say that a large proportion of double IFSDs can be actually put down to shutting fuel off on the wrong engine. As stated, nice to still have 2 left rather than 1, even if the T/W ratio is very slightly poorer!
Having said all that, bottom line considerations (and A340 experience) confirm that the 4 engine jet cannot compete with widebody twins (like that nasty common, but bloody efficient 777). They are now dinosaurs, but re-assuring dinosaurs!

[PPRuNeUser0171]

Interesting discussion. I'm an airchair pilot so have more of an understanding of this stuff than your average passenger but certainly not as much as you guys who do this stuff day in and day out.

Now, My thoughts on this are that the flight deck crew did the right thing. Really, what is the issue on flying on three engines? I'd assume that right after the engine shutdown various checks would be carried out to ensure that the problem was limited to single engine?

I'd also assume that even though this jet might not be subject to ETOPS type operation it would still be good airmanship to have diversions planned for the Atlantic flight and to review those after the engine failure?

I'd also assume that this wasn't just the decision of the Captain but of the Captain and first officer and anyone else who was operating the flight - CRM and all that? I'd further assume that the lower altitude flight and planned diversions would have been checked by both crew members and company operations?

Now, with all that checking, cross checking and with the information available on a modern flight deck I'd say that the flight was perfectly safe. More so than flights just 20 or 30 years ago with all four engines working.

Finally, I believe it was the FAA themsevles that made a comment about the engine reliability being so good that they had no issues with >240minute ETOPS being introduced.

As I said, this is just my thoughts as an armchair pilot.

[Rotorgoat8]

In response to treadigraf;
Yes, you are correct regarding maintaining altitude---Loss of an engine in the 747 would normally result in a need to descend to a lower altitude. It could be requested to ATC and an emergency declared if the altitude requested was said to be unavailable.

[Notso Fantastic]

williamsg, the Flight Management System gives continual (and accurate) fuel predictions. When you select 'Eng Out', it will reprogram at the attainable cruise altitude new fuel predictions. On the 747, you would program new lower winds, and you will get an answer straight away as to whether continuation is feasable. The crew took the decision after consultation with BA main control on satphone. Operations would have looked at all en route weather and diversion options (this is BA!) and even calculated a new flight plan. The crew were professional enough to study all enroute diversions in the event of a further failure- this is part of the job anyway. It was not a spur of the moment decision by one person- it was standard BA procedure- on a 4 engined aeroplane, loss of one is no sweat.
On a classic 747 in the early days of 747 ops, we lost one over Labrador. Absolutely no thought of diverting to Gander, Goose or any other Canadian bird-sounding airport, we descended to 25,000' and continued to Chicago. After losing one flying LHR-NBO over the toe of Italy, we turned and returned to LHR. All in consultation with main control. It's no help to anyone to dump a 747 load in an unusual place with 400 people and no hotel rooms. The best answer was after 6 hours flying to get back to home base and wheel out another 747 (and another crew!). In all cases, the faults were either isolated unrecoverable surges or loss of oil. The LA one was a surge. Isolated fault. People who haven't a clue are the ones who criticise loudest! BA knows what it is doing- never lost a 747 yet*! But at the end of the day, as you said, you are an armchair pilot and basically don't understand fully the issues involved, so a decision on the whole procedure should be taken with great caution, like I would be sparing on decisions taken by other professionals in their various industries (that I don't really understand!).

*-Excluding the Kuwait one blown up by Saddam

[PPRuNeUser0171]

Notso - thanks for that and I am agreeing with you!! What I was (badly) trying to say is that this wouldn't be a single person making the decision it would be a group discussion before a decision is reached and with todays FMC's the information thats available is a heck of a lot more accurate.