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Shutting Down an Engine to Complete the Flight

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Shutting Down an Engine to Complete the Flight

Old 16th Nov 2021, 17:46
  #21 (permalink)  
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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!
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Old 16th Nov 2021, 18:13
  #22 (permalink)  
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Originally Posted by YRP View Post
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 wasnít 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.
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Old 16th Nov 2021, 19:25
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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...
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Old 16th Nov 2021, 19:43
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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.
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Old 16th Nov 2021, 20:48
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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.
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Old 16th Nov 2021, 21:12
  #26 (permalink)  
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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.
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Old 17th Nov 2021, 04:38
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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.

Last edited by blind pew; 17th Nov 2021 at 04:50.
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Old 17th Nov 2021, 06:59
  #28 (permalink)  
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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 ?
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Old 17th Nov 2021, 08:01
  #29 (permalink)  
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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.
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Old 17th Nov 2021, 09:39
  #30 (permalink)  
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If the aircraft didnít 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.
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Old 17th Nov 2021, 09:56
  #31 (permalink)  
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Incorrect. Some aeroplanes have four engines so they can continue on three.
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Old 17th Nov 2021, 16:50
  #32 (permalink)  
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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.
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Old 17th Nov 2021, 19:27
  #33 (permalink)  
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I knew that that would happen, that is start on the BA 747-400 OEI across the pond.
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Old 17th Nov 2021, 19:52
  #34 (permalink)  
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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 ?

Last edited by zambonidriver; 17th Nov 2021 at 21:23.
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Old 17th Nov 2021, 23:42
  #35 (permalink)  
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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.
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Old 18th Nov 2021, 19:53
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Originally Posted by Capt Fathom View Post
If the aircraft didnít 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 itís perfectly safe on three.
Iím simplifying a bit, naturally.
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Old 18th Nov 2021, 22:30
  #37 (permalink)  
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An extension of that logic is the twins would only need one.
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Old 19th Nov 2021, 06:09
  #38 (permalink)  
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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.
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Old 19th Nov 2021, 06:43
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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?
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Old 19th Nov 2021, 07:12
  #40 (permalink)  
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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…

Last edited by wiggy; 19th Nov 2021 at 08:55.
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