Shutting Down an Engine to Complete the Flight

[punkalouver]

I thought this was an interesting scenario showing how an event can be handled. I suppose imbalance considerations were part of the whole scenario as well.

"N ------ a Boeing 747-4--F operated by ----------, was conducting cargo flight XX--- from
Anchorage (PANC), AK to Miami Intl. (KMIA), FL. Approximately 1 hour into the flight, the flight
crew observed that the #1 engine was being fed fuel from the #1 main fuel tank instead of the
inboard tanks as was selected. It appeared as though the #1 fuel crossfeed valve was in the closed
position and the flight crew were unable to select it open, leaving the engines only source of fuel
being the fuel remaining in #1 main tank. As this was insufficient to supply the engine for the
duration of the flight, the flight crew contacted the company operations center for guidance, and the
decision was made to shut down the #1 engine and continue the flight to
destination. When the fuel remaining in the tank was sufficient to supply the engine for the
remaining duration of the flight to the destination, the #1 engine was restarted and normal aircraft
operations were resumed. An uneventful landing was completed in KMIA.

Company maintenance subsequently replaced the #1 engine crossfeed valve actuator, and the
aircraft was returned to service."

[Smilin_Ed]

Interesting. Since they had no passengers aboard, they treated the situation as if they were making a three-engine ferry for part of the flight.

[Tango and Cash]

British Airways did it with pax aboard, just a little short of fuel at the end.
https://en.wikipedia.org/wiki/British_Airways_Flight_268

[Meikleour]

To paraphrase the late Eric Morecambe - they had enough fuel but not necessarily in the correct tanks!

The incident reflected poorly on BA's procedures for fuel balancing having differed from that mandated by Boeing.

[wiggy]

Here we go again…..:rolleyes:

Not sure where we are nowadays with flight continuation but certainly once upon a time under some jurisdictions continued flight on a four engined type reduced to 3 engines was acceptable as long as the rest of the route allowed further degradation to 2 engines, so you had to look hard at en-route MSAs vs 2 engined performance, and suitable and available en-route alternates

It was certainly allowable to continue on 3 engines with passengers on-board and I even ended doing it myself on one memorable sector.

As Meikleour says the main reason the BA flight made it into the headlines was fuel handling not an actual shortage of total fuel on board, and I think many of those at the company learnt something from that.

[Bergerie1]

wiggy is absolutely right. I do wish people would stop making mountains out of molehills.

[blind pew]

Both of you are ignoring the engine windmilling certification criteria which even with an undamaged engine they exceeded. This engine failure had unknown damage and even one of the passengers was asked what he observed.
BA had made a mess of the crossfeed drill as they had with the 777 evacuation drill as demonstrated at Heathrow.

[JanetFlight]

Back in the late 70's VIASA did almost the same after took off from Caracas with a little difference/detail...it was a DC10, one less "stove" than the 747 :)

[Locked door]

blind pew

Engine windmill criteria? Twelve years on the 744, never heard of that one.

Categorically, there was no such limitation on RR 744’s.

[YRP]

Perhaps the key factor that was brought up about that BA decision to continue was that the 744 is in fact certified for continued operation on 3 engines.

It wasn’t based on some general philosophy of 4 engine airplanes, rather that the -400 specifically had sufficient redundancy on the other engines, eg electric sources etc.

As I recall the -100 and -200 were not so certified but the -400 was (not sure on the -300).

(This is based on pprune members at the time, can’t personally confirm it).

For this flight it sounds like there can be no concerns as to not being certain of cause of the engine out. Some brought that up for BA although I seem to recall the report fully exonerating that aspect.

[Locked door]

As was pointed out during my conversion course, a 744 on three engines has more redundancy than a 777 on two engines.

Still cat3b no DH, 4x hyd systems, one gen out (three remaining), three bleeds, three packs, the list continues…….

Amazing machine.

[srjumbo747]

Locked door

Many years on the 744.
If the engine is not windmilling it burns more fuel.
Simples!

[wiggy]

Locked door

yeah but on one engine….:E

I flew both (plus the Classic 747s) . I’m not going to dig out time expired FCOMs to check but whilst your equipment count is sort of correct as I recall it the T7 also had some interesting engineering workarounds to ensure redundancy/robustness.

I agree you can’t escape the basics of the engine count but in a funny way that made decision making in some circumstances easier….

.and FWIW I had more engine failures on the 744 than I had on the T7…

[43Inches]

Easy to also overlook that if any other engine failed the one that was shut down to conserve fuel could just be restarted if need be for performance. This is not an engine failure, its a choice to shut down to allow that engine to be available for a normal approach and landing at the destination due to fuel constraints.

Definitely mountains of molehill stuff, although a good example of thinking outside the box to get the job done safely.

Also it was flying Anchorage to Miami, its basically within an hour of a suitable landing port the whole journey. Not sure what the issue is here?

[DaveReidUK]

There was no certification requirement for prolonged windmilling to be demonstrated for the RB211-524.

[punkalouver]

I did delete the engine type for de-identification purposes. But seeing as this came up…….it was a CF-6 engine. Don’t remember reading about any max limitation times for this engine in the limitations section.

[Locked door]

FWIW I’ve contemplated something similar for an oil leak coming back from Sao Paolo. The plan was to shut the engine down once the oil reached a certain level allowing for a restart in the descent to have all engines operating for the approach. As it transpired the leak slowed as the quantity decreased meaning we never reached the quantity we nominated for shutdown.

[Good Business Sense]

and FWIW I had more engine failures on the 744 than I had on the T7

For me ..... 747 = 1 and A330 = 2 (not at the same time but both on ETOPS sectors)

so lots of single engine jet time :-)

[B2N2]

Creative solution to a interesting problem.
Sorted with help from MX control, dispatch, operations, so no doubt all legalities were considered.

[parabellum]

I flew the -744 with the P&W4056 engine and had cause to shut one down half way back across the Pacific, SFO to HKG. It was because we were getting a fuel flow filter warning light. The only time I remember windmilling could become a possible problem was if the shut down was caused by loss of oil pressure and/or quantity leading to a windmilling engine without sufficient lubrication.

To get rid of unwanted maintenance messages on the -400 after it had been left unpowered for a while in a humid climate I followed a Boeing engineers advice and selected Alternate Flap switch to 'Alternate' for a few seconds then back to off, messages gone!

[eckhard]

I had another unusual usage of the Alternate Flaps switch several years ago:

After take-off, F/O's F/D fails, all three A/Ps unable to select. Flaps retracted normally.

Solution: Arm alternate flaps for 30 seconds, then disarm.

All APs functioning and F/O F/D works again!

[tdracer]

Perhaps the key factor that was brought up about that BA decision to continue was that the 744 is in fact certified for continued operation on 3 engines.

It wasn’t based on some general philosophy of 4 engine airplanes, rather that the -400 specifically had sufficient redundancy on the other engines, eg electric sources etc.


Further, unless it's rather heavy, a 747-400 or -8 will cruise quite happily at 35k on three engines (higher if it's light) - although it does burn more fuel doing it than on four (like YRP I'm not sure about the older 747s). Good luck doing that on any twin with an engine out...
As I recall, none of the 747-400/-8 engines have windmilling restrictions provided oil pressure remains positive (the windmilling core will provide sufficient oil pressure assuming the oil system is otherwise healthy).
The BA is the best knows case of a 747 crossing the Atlantic after an engine failure at or just after takeoff (presumably because they ran low on fuel and diverted), it's certainty not the only one.

[Telekon]

eckhard

I've also had the "magic reset" ALTN FLAPS button work for all kinds of unrelated faults on the 744. I'd really love to know why that works and what it's doing behind the scenes...

[DaveReidUK]

tdracer

The BA flight requested FL320 for the Atlantic crossing, but that was unavailable due to traffic. Most of the crossing was flown at FL290 after FL350 had been offered, but declined as unable.

[Adverse Jaw]

Operating a DC-10 eastbound across the Atlantic we experienced a slow but steady oil loss which we calculated would not see us to our destination. So at 30W we shut down the engine with sufficient oil remaining and the intention to relight it for our arrival, all engines being obligatory for the auto-land required under the forecast conditions.
However, to our dismay, we discovered that the oil consumption increased drastically with engine out, precluding a re-start. An improvement in the weather saved any embarrassment and we landed engine out. But interestingly, it was explained to us that under windmilling conditions the GE-CF6 labyrinth seals no longer perform and hence the rapid oil loss.

[gums]

Good discussion. And a comment from the peanut gallery of the one-hearts.

A serious challenge arises if the fuel supply to the only motor you have is a problem, hence ... Our first Sluf loss was a peaceful ferry mission with a rare fuel transfer problem and the pilot did not use the emergency fuel transfer feature the plane had. The Navy model did not have a way to correct the problem if the main tank feeding the motor failed, but our new "D' models did. Later, similar feed problems were handled easily using the "alt feed" doofer which shut off the ejector doofers and everything went to gravity feed for the motor. Used that for missions where we encountered heavy AAA and such, but it limited power above 15K or so. The Sluf used fuel pressurized venturi things to move the gas around and if one of the "ejectors" was clogged, the fuel stopped flow from that tank. Hence our new guy's problem, and he ran outta gas from the sump tank before using the new feature.

Someone brought up the windmilling criteria, and that is one thing to consider. One jet I flew was so over powered that we could cruise or loiter on one motor of the two. However, we had to re-start every half hour or so to keep all the shaft bearings lubricated. So unless the motor was on fire when you shut down, you cranked it back up and let the other one windmill.

[blind pew]

Somewhere in the incident report the investigators mentioned the demonstrated certification criteria which BA ignored. It was obviously included for a purpose. My first flight on a BA classic was DH to Nairobi to pick up a VC10, after the Concorde lounge, first class dinner and some more sherbert my head hit the pillow to be stirred by a rumbling through the airframe somewhere over Africa as an engine went bang..we turned around and flew home.
From my early days including Hamble, I’ve been appalled at the blame someone else and cover up mentality in aviation. One of my first instructors was involved in the prosecution of Glen Stewart (?) of the Heathrow flypast fame who committed suicide after being hung out to dry. It would never had happened if an illegal dispensation for the approach had been authorised by a BA manager. My first solo I got into a PIO as I hadn’t been taught what to do with a bounce by said instructor, a real Walter Mitty character.
This then BA culture goes back to BEA and the Munich disaster, through Staines, Manchester.......
The fact is that the engine had failed, there was unknown damage and the crew had no way of ascertaining the potential consequences of continued flight; they took an unnecessary risk which the FAA didn’t condone. They weren’t the brightest as they didn’t understand the fuel system and got into a panic it would seem on approach into Manchester. They didn’t do any favours to the reputations of the profession.

[DaveReidUK]

Originally Posted by blind pew
Somewhere in the incident report the investigators mentioned the demonstrated certification criteria which BA ignored.

There were indeed several references to certification criteria in the report:

In order to meet certification requirements for multi-engined public transport aircraft, the loss of an engine at the most adverse point is a design case that is catered for by redundancy. The B747 has an appreciable level of systems redundancy and no evidence was found to suggest that the aircraft systems would be affected by the loss of an engine.

Detailed information on the possible adverse consequences of a long period of flight with a damaged engine that had been shutdown was sought during the investigation. The engine manufacturer noted that engine certification regulations generally did not require a prolonged windmilling to be demonstrated and this was the case for the RB211 -524. However, the qualification testing for the type had included 3 hours of engine windmilling operation, related to the 180 minutes Extended Twin Operations (ETOPS) clearance, with no bearing damage expected. In accordance with this, the manufacturer’s Maintenance Manual permits an engine to be ferried, whilst windmilling, with no restriction except with relation to FAFC low temperature limits.

As a 4-engined aircraft the B747 is designed and certificated to tolerate the loss of a second engine following an initial IFSD, without losing essential systems or necessary performance capabilities. The likely effects on systems would include the need to shed non-essential electrical loads, such as galleys, and to limit bleed air supplies in order to maintain adequate performance from the operating engines. There would also be a loss of the auto-land capability with two engines inoperative on one side of the aircraft. Aircraft performance implications would include a substantial further loss of altitude capability, but it is intended that route planning after the first IFSD would cater for this eventuality. The probability of the loss of a third engine, during the diversion that would subsequently follow the second engine loss, is considered below.

Modern public-transport aircraft design has included target maximum rates for engine failure and IFSD in order to achieve an acceptably low risk of a potentially catastrophic loss of aircraft propulsion. For design and certification a risk level of “Extremely Improbable”, or 1 x 10-9 per flight hour, is generally used.

Systems operation should not be affected significantly following an IFSD; the level of redundancy would be reduced but the aircraft was designed and certificated to tolerate the loss of a second engine without losing essential systems. Previous experiences of the effects of engine surge suggest that it was likely that damage would be confined to the affected engine. Furthermore, the manufacturers did not foresee any problems with the extended windmilling of a damaged engine and previous cases had not resulted in significant additional damage.

Which one(s) are you saying was/were ignored ?

[Locked door]

Blind Pew, so many inaccuracies and assumptions it’s difficult to know where to begin.

The 744 was designed by Boeing to be able to continue to destination OEI if certain criteria are met. The FAA mistakenly threw their toys out the pram, presumably because those involved had twin engine experience. There was a rumour part of their motivation was because not many quads were operated by US based airlines they wanted to level the playing field and remove the advantages provided by having four engines. Whether that rumour is true I have no idea. They subsequently wound their necks in once shown the Boeing FCTM.

Just FYI, all BA 744’s had real time remote engine monitoring by both RR and BA power plant with many more parameters than available on the flight deck, and a remote health check of the remaining engines was also possible (and more than once on the 744 I received an ACARS about a possible issue before it was apparent on the flight deck). I wasn’t on board but I suspect the crew knew exactly why the engine failed and how healthy the remaining three were. 744 crews were trained to continue while gathering information and decision making in the knowledge that a return or diversion were always options.

The decision to continue was justified, within the rules and safe, the issue with fuel balancing that meant the crew ended up in Manchester was unfortunate but the BA change to the procedure was Boeing approved. For your information there was no fuel shortage, however the crew found they were unable to move some of it to the tank they wanted it in so decided to nominate it as unusable.

Despite being shown references, I don’t doubt you’ll continue to disagree.

[Capt Fathom]

If the aircraft didn’t need 4 engines, it would have been designed with only three!
When an engine fails, you land. As soon as it is safe and practicable. Continuing is clouded with unknowns.

[Locked door]

Incorrect. Some aeroplanes have four engines so they can continue on three.

[Miles Magister]

Well back in the day on the venerable old Hawker 801 we used to routinely shut 2 down to save fuel once we were light enough to climb up to safety altitude on one engine, did it on most flights. Otherwise at least one was shut most of the time.

I have also shut an engine down to isolate a fuel leak and continued on 3.

One thing to be aware of when writing manuals, procedures and permissions in modern EASA land is that if a crew are required to to normally, not an emergency, carry out a non-normal procedure they must be Maintenance Check Flight trained. Whether this applies in the case mentioned above will be an interesting discussion to watch from a distance.

[Pugilistic Animus]

I knew that that would happen, that is start on the BA 747-400 OEI across the pond.

[zambonidriver]

To get back to the matter at hand am I the only one seeing a significant difference between a freighter coasting along the US east coast and a passenger plane crossing the Altlantic ?

[tdracer]

DaveReidUK

Yea, given they lost the engine during takeoff, they would be pretty heavy with fuel for a trans-Atlantic flight so 35k would have been pretty tough until they burned off some fuel.

[OldLurker]

If the aircraft didn’t need 4 engines, it would have been designed with only three!AFAIR (but those who were there will correct me) the 747, and other four-engined aircraft, were designed with four engines so that they could get off the ground at max weight in a reasonable distance. But they were also designed, as all multi-engined airliners must be, so that having reached takeoff speed, if one engine fails the aircraft can continue takeoff and climb. Thus, the 747 does need four engines, but only to get off the ground! After that it’s perfectly safe on three.
I’m simplifying a bit, naturally.

[megan]

An extension of that logic is the twins would only need one.

[wiggy]

Not really…:} …

A 747 with an engine failure after take off retains the capability to land at the nearest suitable airfield should another engine fail.

A Twin with an engine failure after take off is in a slightly different situation should another engine fail.

[Bergerie1]

DaveReidUK and Locked door (posts 28 and 29 above) have both provided the correct and definitive answers. The 747 was designed with an incredible amount of redundancy, more than any aircraft had had before. Is it now time to close this thread before even more nonsense is posted by people who do not know all the facts?

[wiggy]

I suspect one issue here is that continuation on 3 has perhaps happened more frequently than people realise. it maybe only became something worthy of note/discussion when the BA event went high profile for reasons various, and now some regard any continuation as being an example of poor judgement or worse….sure as night follows day we rapidly get to the “ah but Corbyn BA” comments.

On the one occasion I was involved in flight continuation we were over a part of the world where there were alternates but going to the nearest would have been interesting politically…On examination it was obvious we had plenty of options further ahead, right through to destination and no terrain issues……as a result we got to destination about three hours after the event without the passengers ever knowing number X had been shutdown, with plenty of fuel, and so didn’t make the papers…

[Locked door]

I remember one 744 shutting down an engine across the Atlantic and after exiting the track, descending and subsequently being cleared to rejoin the track at a lower level, a voice piped up on 123.45 and said “hey Speedbird, how come after losing an engine you’re still higher than us and faster than us?”, to which the response was “we’ve still got one more engine than you!”

Like I said, an amazing machine.

[Bergerie1]

wiggy and locked door, I agree with you both and, like you, I have done the same - no problem at all so long as you keep looking at en-route alternates and plan accordingly. It all depends on why the engine was shut down - if there is no damage there is no problem. I believe the BA flight in question had an engine surge, it looks spectacular but hardly ever does any lasting damage. The inflight engine monitoring that was being done by RR and BA would have revealed whether or not it was safe to continue, but I don't know all the facts since it occurred long after I had retired.

The only time I ever became slightly worried was when we were doing a 3-engine ferry and one of the remaining engines started to lose oil and it looked as though we might need to shut it down. As we had already planned for a possible third engine shut down, taking account of safety heights and en-route alternates, it was no real problem. Fortunately, it never got down to the minimum so we carried on to London.

There really is no need to make mountains out of molehills!

[Uplinker]

Never flown the 747, so a quick question:

In the case of this OP with a limited fuel supply to one engine; would it have been an option to keep the affected engine running but only at idle, complete the crossing on three engines, then spool up the affected engine again for approach and landing? That way, the systems provided by the compromised engine, and its oil circulation etc would have been maintained?

[Locked door]

Good question, it would depend on how much fuel was in the tank.

You don’t gain anything in the way of ancillary systems by keeping the engine running though, you still have the increased fuel burn of being one engine inop (approx +10% per failed engine) plus the fuel burn of an engine at idle. The associated hyd system doesn’t need the engine, there’s a back up demand pump on all four systems that takes over if the engine driven pump fails (the 744 has ten hyd pumps, four engine driven, four back up and two for ground use). Having four generators is no different to having three, there’s no load shedding, having four bleeds is no different to having three. Even if you can’t restart it one engine inop makes no difference to the approach capability, it’s CAT3B no DH either way. There’s no oil lubrication issue with a windmilling engine with RR engines. It’ll fly just fine two engine inop even with both out on the same side, it just becomes Cat 1 only with reduced GA climb performance (IIRC approx 1000agl is the lowest you can GA 2EI) and really high MSA’s are an issue which is why both issues are assessed among other things as part of the continuation policy.

I think I’ve just talked myself out of keeping it running!

[Uplinker]

Thanks :ok:

10 hyd pumps..........? Wow !

[mustafagander]

B747 series beautifully over-engineered.
One of the design criteria, as I have been informed by those "in the know" was that the aircraft can always make it back to base, no single fault/failure should stop her.
Just FYI, the hydraulics had 4 engine driven pumps, 4 air/electric pumps as backup and 2 aux pumps - Sys #1 and #4 - for push back.
The rest of the systems were similarly engineered. Marvelous to operate this aircraft.

[DaveReidUK]

Well, yes (barring unforeseen structural failure, obviously).

But are you suggesting there are other aircraft types in service, or in the past, where that wasn't a design criterion?

[mustafagander]

If you're referring to me, Dave, I fail to see the thrust of your question.

[DaveReidUK]

I was suggesting that the design criterion you referred to was pretty universal and by no means specific to the 747.

[Uplinker]

@mustafagander; "B747 series beautifully over-engineered. One of the design criteria, as I have been informed by those "in the know" was that the aircraft can always make it back to base, no single fault/failure should stop her."

That is the case for most commercial passenger aircraft - even twins nowadays. But what a wonderful aircraft the B747 is. Truly Boeing at its very best, and such a shame that the company has now fallen so low, owing to greed and the desire to make money rather than make good aircraft.

I still occasionally look at the fold-out diagrams of the B747 classic in my copy of 'Handling the big jets' by Davies, and marvel at the engineering and built-in redundancy. Today, though, such over-engineering is not necessary; technology has advanced reliability to the stage where two engines are good for most operations. The 747 is effectively two aircraft within one airframe:- double sets of main gears, double the number of engines, double the number of hyd pumps, etc, etc. As someone mentioned, the fourth engine is only really needed for take-off at high weights, and the same probably goes for the body main gears.

But nevertheless, an awesome aircraft and a game changer; deservedly in the aviation hall of fame.