Shutting Down an Engine to Complete the Flight
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.
Like I said, an amazing machine.
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!
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!
Last edited by Bergerie1; 19th Nov 2021 at 09:54.
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?
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?
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!
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!
Last edited by Locked door; 20th Nov 2021 at 12:15.
Thanks 
10 hyd pumps..........? Wow !
10 hyd pumps..........? Wow !
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.
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.
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?
But are you suggesting there are other aircraft types in service, or in the past, where that wasn't a design criterion?
@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.
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.
