Twin engined flights over long Oceanic routes
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Twin engined flights over long Oceanic routes
Somebody please reassure me about the long Oceanic routes on twin engined airliners.
I have heard of the ETOPS rules but do not entirely understand them.
Is it true that if an engine fails then the aircraft may possibly have to fly up to 750 miles to the nearest airport?
I have heard of the ETOPS rules but do not entirely understand them.
Is it true that if an engine fails then the aircraft may possibly have to fly up to 750 miles to the nearest airport?
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These flights happen many times every day!
Think 757, 777, 767.... I for one have flown over the Atlantic in all three ( I think) and so far have not gone plumeting to the ocean bed...
There is a thing where people think that 4 engines is the only safe way over ocean routes... maybe this is because of Virgins slogan:
"4 engines 4 longhaul" or whatever it is...
Well even they have gone against what they preach and have placed an order for the new 787s!
And guess what... they are two engined beasts =)
If your worried you could wear the life jacket throughout the flight.... at least you would get attention from the hostess
But seriously it will be fine!
(but i do always check that my lifejacket is there and in place by having a quick feel! - anybody else do this or do they just pressume that everyone have done their job...?)
Think 757, 777, 767.... I for one have flown over the Atlantic in all three ( I think) and so far have not gone plumeting to the ocean bed...
There is a thing where people think that 4 engines is the only safe way over ocean routes... maybe this is because of Virgins slogan:
"4 engines 4 longhaul" or whatever it is...
Well even they have gone against what they preach and have placed an order for the new 787s!
And guess what... they are two engined beasts =)
If your worried you could wear the life jacket throughout the flight.... at least you would get attention from the hostess
But seriously it will be fine!
(but i do always check that my lifejacket is there and in place by having a quick feel! - anybody else do this or do they just pressume that everyone have done their job...?)
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There is a thing where people think that 4 engines is the only safe way over ocean routes... maybe this is because of Virgins slogan:
"4 engines 4 longhaul" or whatever it is...
Well even they have gone against what they preach and have placed an order for the new 787s!
"4 engines 4 longhaul" or whatever it is...
Well even they have gone against what they preach and have placed an order for the new 787s!
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Twin engined flights over long Oceanic routes
Not very reassuring yet,
I have seen the vid featuring the Ethiopean owned airliner forced landing on water, it fell to bits!
The chance of being alive to use the life jacket seem remote.
Hopefully some of the airline pilots could explain the ETOPS rules.
I have seen the vid featuring the Ethiopean owned airliner forced landing on water, it fell to bits!
The chance of being alive to use the life jacket seem remote.
Hopefully some of the airline pilots could explain the ETOPS rules.
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Yes be very reassured.
In the 60,s and 70's twin engine jetliners were designed and optimised for short haul routes. Aircraft such as the Caravelle, BAC 111, DC9 and Boeing 737 were designed to fly between city pairs between 100 miles and 1500 miles apart. However with the advent of new technology high bypass engines, the need for 3 or 4 engines on medium sized longhaul aircraft and more recently on large longhaul aircraft became largely redundant.
In the 1980's with the introduction of the Boeing 757 and the jointly developed Boeing 767, there was a new breed of twin engine jetliner that had the range to fly 3500 miles (757) up to 5500 miles (767). This opened up transcontinental and trans oceanic routes to a new breed of twin engine airplane. Previously the rules for flying twin engine aircraft over the sea had restricted them to no more than 60 - 90 minutes flying time from the nearest airport, which given their range was very rarely a problem. Some countries (including the USA) also had very scant requirements concerning the level of safety equipment that had to be carried on board. Life jackets could often be substituted by seat cushions as floatation devices provided the distance flown from shore fell within the regulations. Given the range of the new generation of twin engine jetliners this would clearly be unacceptable, and together with a whole range of other safety related issues (including engine reliability, fire suppression, emergency electrical generation and additional system backups), a set of new rules known as ETOPS (EROPS) was born.
Extended (R)ange (T)win engine OPerationS provides for a whole raft of rules that these aircraft have to comply with to ensure an acceptable and high level of safety. The distance that can aircraft can fly over the sea ( or land) is governed by the time at any point an engine might potentially fail and the time it would take on the remaining engine to divert to an adequate and suitable airport. That is an airport that has adequate runways and other facilities, and where the weather is suitable. This distance as far as ETOPS s concerned is normaly 120 minutes, 138 minutes, and 180 minutes. Sometimes it can be higher and in future generations of aircraft it very likely will be higher. This time is based on the single engine flying speed of the aircraft, which surprisingly is still 80 to 85% of the normal cruising speed. So for a Boeing 757/767 for example it is around 400 kts (460 mph). That means when flying 180 minutes ETOPS the aircraft may fly a route that keeps it within 1380 miles of a suitable diversion airfield. In other words it can a fly a route that is 2760 miles between suitable airfields. Over the North Atlantic and most of the Pacific that leaves very few holes.
When planning an ETOPS or indeed any longhaul flight there are 3 potential emergency scenarios that have a major role in fuel planning. The first is engine failure in accordance with route or the ETOPS rules, the second is a depressurisation and a descent to 10,000ft, and the third is an engine failure and a depressurisation and descent to 10,000ft. Surprisingly perhaps, from a fuel point of view the worst case scenario is the second, the depressurisation and descent to 10,000ft. At this altitude (and it would be required) the fuel burns are very high. This is especially so on a 3 or 4 engine aircraft, and to that end the problem may be as bad if not worse for 3 or 4 engine aircraft than for ETOPS aircraft.
The degree of engine reliability for ETOPS certified aircraft and their high bypass tubofans is extremely high and the loss of one power unit is very rare. The loss of 2 engines due to non common events (fuel starvation or flying through volcanic ash etc.) is infinitesimally small.
In addition to this, there are much higher planning weather minima laid down for ETOPS flights, Crew have additional certification. The aircraft has to carry extra safety equipment, and the aircraft has to have additional ETOPS related systems and system components which must be serviceable prior to and during the ETOPS segment of each and every flight.
I have being flying ETOPS over the Atlantic, Pacific and Indian Oceans for the last 22 years and only ever had to divert once and even that was related to a slow leak in an Oxygen system. ETOPS is extremely reliable and a normal, common and routinely employed method of oceanic flying today. You should be very relaxed and very confident on your flight.
In the 60,s and 70's twin engine jetliners were designed and optimised for short haul routes. Aircraft such as the Caravelle, BAC 111, DC9 and Boeing 737 were designed to fly between city pairs between 100 miles and 1500 miles apart. However with the advent of new technology high bypass engines, the need for 3 or 4 engines on medium sized longhaul aircraft and more recently on large longhaul aircraft became largely redundant.
In the 1980's with the introduction of the Boeing 757 and the jointly developed Boeing 767, there was a new breed of twin engine jetliner that had the range to fly 3500 miles (757) up to 5500 miles (767). This opened up transcontinental and trans oceanic routes to a new breed of twin engine airplane. Previously the rules for flying twin engine aircraft over the sea had restricted them to no more than 60 - 90 minutes flying time from the nearest airport, which given their range was very rarely a problem. Some countries (including the USA) also had very scant requirements concerning the level of safety equipment that had to be carried on board. Life jackets could often be substituted by seat cushions as floatation devices provided the distance flown from shore fell within the regulations. Given the range of the new generation of twin engine jetliners this would clearly be unacceptable, and together with a whole range of other safety related issues (including engine reliability, fire suppression, emergency electrical generation and additional system backups), a set of new rules known as ETOPS (EROPS) was born.
Extended (R)ange (T)win engine OPerationS provides for a whole raft of rules that these aircraft have to comply with to ensure an acceptable and high level of safety. The distance that can aircraft can fly over the sea ( or land) is governed by the time at any point an engine might potentially fail and the time it would take on the remaining engine to divert to an adequate and suitable airport. That is an airport that has adequate runways and other facilities, and where the weather is suitable. This distance as far as ETOPS s concerned is normaly 120 minutes, 138 minutes, and 180 minutes. Sometimes it can be higher and in future generations of aircraft it very likely will be higher. This time is based on the single engine flying speed of the aircraft, which surprisingly is still 80 to 85% of the normal cruising speed. So for a Boeing 757/767 for example it is around 400 kts (460 mph). That means when flying 180 minutes ETOPS the aircraft may fly a route that keeps it within 1380 miles of a suitable diversion airfield. In other words it can a fly a route that is 2760 miles between suitable airfields. Over the North Atlantic and most of the Pacific that leaves very few holes.
When planning an ETOPS or indeed any longhaul flight there are 3 potential emergency scenarios that have a major role in fuel planning. The first is engine failure in accordance with route or the ETOPS rules, the second is a depressurisation and a descent to 10,000ft, and the third is an engine failure and a depressurisation and descent to 10,000ft. Surprisingly perhaps, from a fuel point of view the worst case scenario is the second, the depressurisation and descent to 10,000ft. At this altitude (and it would be required) the fuel burns are very high. This is especially so on a 3 or 4 engine aircraft, and to that end the problem may be as bad if not worse for 3 or 4 engine aircraft than for ETOPS aircraft.
The degree of engine reliability for ETOPS certified aircraft and their high bypass tubofans is extremely high and the loss of one power unit is very rare. The loss of 2 engines due to non common events (fuel starvation or flying through volcanic ash etc.) is infinitesimally small.
In addition to this, there are much higher planning weather minima laid down for ETOPS flights, Crew have additional certification. The aircraft has to carry extra safety equipment, and the aircraft has to have additional ETOPS related systems and system components which must be serviceable prior to and during the ETOPS segment of each and every flight.
I have being flying ETOPS over the Atlantic, Pacific and Indian Oceans for the last 22 years and only ever had to divert once and even that was related to a slow leak in an Oxygen system. ETOPS is extremely reliable and a normal, common and routinely employed method of oceanic flying today. You should be very relaxed and very confident on your flight.
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No, it is an underestimate.
An airplane with 1 engine out travels at about 400 knots.
So, ETOPS 120 means 800 miles on one engine. But there are higher Etopses than Etops 120. Such as Etops 138, Etops 180 and Etops 207. Etops 180 means 1200 miles, Etops 207 means 1380 miles. And Etops 180 is the notional no wind range. One plane actually did fly 192 minutes on one engine because of foul wind.
USA is since 1st of February offering higher Etops as well, but I believe no one has yet taken it up.
An airplane with 1 engine out travels at about 400 knots.
So, ETOPS 120 means 800 miles on one engine. But there are higher Etopses than Etops 120. Such as Etops 138, Etops 180 and Etops 207. Etops 180 means 1200 miles, Etops 207 means 1380 miles. And Etops 180 is the notional no wind range. One plane actually did fly 192 minutes on one engine because of foul wind.
USA is since 1st of February offering higher Etops as well, but I believe no one has yet taken it up.
Reliable
Be reassured by the fact that when you look at mean time between failures... jet engines are some of the most reliable mechanical devices ever made by human beings.
They run for decades in power stations, power ships across oceans.
Thousands of airliners are in the air right now with no risk of them stopping.
They will continue to run (roughly) even after a blade has snapped off (itself a rare event).
They can stand massive ingestions of water without the flame going out; birdstrikes - a high degree of damage, and still function.
The technology involved is amazing.
You should actually be far more worried about the two soft machines sitting in the two front-most seats making a mistake.... aircraft nearly always crash beacuse of brain failure, not plane failure.
They run for decades in power stations, power ships across oceans.
Thousands of airliners are in the air right now with no risk of them stopping.
They will continue to run (roughly) even after a blade has snapped off (itself a rare event).
They can stand massive ingestions of water without the flame going out; birdstrikes - a high degree of damage, and still function.
The technology involved is amazing.
You should actually be far more worried about the two soft machines sitting in the two front-most seats making a mistake.... aircraft nearly always crash beacuse of brain failure, not plane failure.
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Twin engined flights over long Oceanic routes Reply to Thread
Thanks Bealzebub.
For your detailed and reassuringly informed reply.
Perhaps I will fly in a twin across the Atlantic after all.
Maybe my fears stem from having flown as passenger in the venerable Avro Shackleton MR3 which had 6 engines (including two Vipers) during my RAF days.
Cheers
For your detailed and reassuringly informed reply.
Perhaps I will fly in a twin across the Atlantic after all.
Maybe my fears stem from having flown as passenger in the venerable Avro Shackleton MR3 which had 6 engines (including two Vipers) during my RAF days.
Cheers
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If twins where not as say have quads...
Why the hell would they be flying these routes multiple times a day?
Why would there be something like 650 777s in service without taking into account of the 757s and 767s and 330s etc.
Point being.
You will be safe..
Why the hell would they be flying these routes multiple times a day?
Why would there be something like 650 777s in service without taking into account of the 757s and 767s and 330s etc.
Point being.
You will be safe..
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We are all entitled to have our opinions...
Old timer pilot flying with 4 motors, here...
So, nobody will convince me, or most of my colleagues.
Oh, granted, ETOPS is a rather safe concept.
But I am entitled to my opinion. I am a pilot, not a hero.
xxx
The more the engines you have, the more likely you are to get problems.
So, correct, a 747 has twice as many chances of having to shut one down.
Has happened to me a few times. Real failure, or precautionary shut-down.
Each time, we continued... to destination. Passengers not even aware.
Three engines remaining is no problem...
Even ferried (yes, takeoff...) with an engine out a few times.
xxx
Sure, high level of reliablility and excellent maintenance on ETOPS machines.
Only two motors to worry about. Half the likelyhood of problems.
But I would not dream of driving a 767 to KEF one hour or so on one engine.
With KEF visibility at minimum RVR and icebergs with smiling pinguins under us.
xxx
The best solution is... 3 engines... best trade.
For them too, they can continue towards destination, or elect to come back.
I flew 727s... I did feel safe overwater with them.
xxx
Think about the A-330 glider to the Azores...
If a plane ever ditches because an engine is out... it will be a twin.
And 2,000 threads by Pprune accident investigators, that day...
It will not be a 1011 or a A-340, a 747 or a A-380...
Maybe airport security will permit you to have sharkfins in your carry-on...
The way airlines go nowadays, they will find a way to operate single engines with single pilot soon.
Personally, I dont care - Soon to be retired, and counting the weeks.
xxx
Happy contrails (or contrail if 1 engine is out on your aeroplanes...) -
So, nobody will convince me, or most of my colleagues.
Oh, granted, ETOPS is a rather safe concept.
But I am entitled to my opinion. I am a pilot, not a hero.
xxx
The more the engines you have, the more likely you are to get problems.
So, correct, a 747 has twice as many chances of having to shut one down.
Has happened to me a few times. Real failure, or precautionary shut-down.
Each time, we continued... to destination. Passengers not even aware.
Three engines remaining is no problem...
Even ferried (yes, takeoff...) with an engine out a few times.
xxx
Sure, high level of reliablility and excellent maintenance on ETOPS machines.
Only two motors to worry about. Half the likelyhood of problems.
But I would not dream of driving a 767 to KEF one hour or so on one engine.
With KEF visibility at minimum RVR and icebergs with smiling pinguins under us.
xxx
The best solution is... 3 engines... best trade.
For them too, they can continue towards destination, or elect to come back.
I flew 727s... I did feel safe overwater with them.
xxx
Think about the A-330 glider to the Azores...
If a plane ever ditches because an engine is out... it will be a twin.
And 2,000 threads by Pprune accident investigators, that day...
It will not be a 1011 or a A-340, a 747 or a A-380...
Maybe airport security will permit you to have sharkfins in your carry-on...
The way airlines go nowadays, they will find a way to operate single engines with single pilot soon.
Personally, I dont care - Soon to be retired, and counting the weeks.
xxx
Happy contrails (or contrail if 1 engine is out on your aeroplanes...) -
When TWA first started flying 767s across the Atlantic (LGW/STL) I was very doubtful. In fact, they hosted me on a visit to their computer centre in Kansas City and I refused to use the 767 route and insisted on going via Chicago. Full marks to them that they permitted me to do that.
Then my brother in law (a BA pilot) switched from 747s to 757s and subsequently dual qualified on 767s. Talking to him I came to better understand the rules and reasons why twins were now allowed across the oceans. I think the 2 that stand out for me are (1) the exceptional reliability of modern engines (2) a difference in rules between ETOPS flight planning and the rules used by triples and quads - as I understand it a twin has to be within x minutes of an airport that is predicted to be open whereas a triple/quad simply has to have nominated alternates (there is no requirement for them to be open). Add in various rules about detection of hold fires and how to extinguish them and an enhanced maintenance regime and I now fly twins with equanimity.
Longest twin flight so far has been BUE/LGW on a BA777.
Then my brother in law (a BA pilot) switched from 747s to 757s and subsequently dual qualified on 767s. Talking to him I came to better understand the rules and reasons why twins were now allowed across the oceans. I think the 2 that stand out for me are (1) the exceptional reliability of modern engines (2) a difference in rules between ETOPS flight planning and the rules used by triples and quads - as I understand it a twin has to be within x minutes of an airport that is predicted to be open whereas a triple/quad simply has to have nominated alternates (there is no requirement for them to be open). Add in various rules about detection of hold fires and how to extinguish them and an enhanced maintenance regime and I now fly twins with equanimity.
Longest twin flight so far has been BUE/LGW on a BA777.
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Some idiots in General Aviation even dare to cross the Atlantic with one engine...
after all...it doesn't know it's over water...
To be fair BelArgUSA if one is going to run out of fuel (in the case of the two twin gliders I can remember) then it doesn't really matter how many engines you have, especially if you leave cross-feed valves open
.
after all...it doesn't know it's over water...To be fair BelArgUSA if one is going to run out of fuel (in the case of the two twin gliders I can remember) then it doesn't really matter how many engines you have, especially if you leave cross-feed valves open
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After both engines on Boeing 777 BA 038 into Heathrow failed to respond to controls last week and stopped providing thrust simultaneously, I am NOT flying twins over long water legs in the future.
Everybody told us that this thing could never happen ( like Bealzebub), reality caught up with us.
At least you have the 747, A 340 and in the future A 380 alternatives.
I will preferably book these flights ( and I would even be prepared to pay a couple of bucks extra for it ).
Believe me, 4 engines DO have a higher intrinsic reliability.
So I totally agree with Belarg , > 3 engines = safety ; twins only make beancounters and shareholders happy.
Frank
BelargUSA quote: "If a plane ever ditches because an engine is out... it will be a twin". I agree
Everybody told us that this thing could never happen ( like Bealzebub), reality caught up with us.
At least you have the 747, A 340 and in the future A 380 alternatives.
I will preferably book these flights ( and I would even be prepared to pay a couple of bucks extra for it ).
Believe me, 4 engines DO have a higher intrinsic reliability.
So I totally agree with Belarg , > 3 engines = safety ; twins only make beancounters and shareholders happy.
Frank
BelargUSA quote: "If a plane ever ditches because an engine is out... it will be a twin". I agree
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After both engines on Boeing 777 BA 038 into Heathrow failed to respond to controls last week and stopped providing thrust simultaneously, I am NOT flying twins over long water legs in the future.
One would assume that if whatever fault caused the BA 777 incident were to occur on an identical triple or quad (apart from the number of engines of course), all 3 or 4 engines would've died anyway, so its meaningless having 2, 3, 4, 6 or 8 engines...same result...
4 engines DO have a higher intrinsic reliability
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Not very reassuring yet,
I have seen the vid featuring the Ethiopean owned airliner forced landing on water, it fell to bits!
I have seen the vid featuring the Ethiopean owned airliner forced landing on water, it fell to bits!
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At the end of the day, 777 diversions do occur, and tend to strand the passengers and the frames in interesting places like Irkutsk.
Or how´d you like to spend some weeks on Easter Island, because the wreck of your 777 sits in the dead middle of the Mataveri runway and no one is getting out or in till some watership shows up over the oceans?
Or how´d you like to spend some weeks on Easter Island, because the wreck of your 777 sits in the dead middle of the Mataveri runway and no one is getting out or in till some watership shows up over the oceans?
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Fendant,
What I actually said was a factual reply with a quick historical background, based on my 22 years of actually doing the job. I can assure you that there have been more accounts of simultaneous engine failure on 4 engine jets where the common event has been fuel starvation or contaminent ingestion and to this end it doesn't matter how many engines you have.
Another point to bear in mind is that 3 and 4 engine jetliners do not have the 3rd and or 4th engines as spares or for safety reasons. They have them because they need them. During certification ( and in service) an aircraft is required to be able to lose one of its power units at a critical speed and still be able ( at its maximum take off weight) to be able to safely climb away. For a twin engine aircraft ( with particular relevance to the ETOPS twins we are talking about), this means that having lost half of its power it can still climb away safely. That is not the case necessarily with a 4 engine aircraft which might need 75% of its available output to climb away safely.
I cannot believe you, because I have flown 4 engine aircraft, and they didn't. On what do you base this statement ?
Why ? For the reasons I have already stated in the first paragraph a twin with an engine failure and a 50% power loss still has to meet the same minimum performance criteria as a 3 or 4 engine jet with a 25% power loss. The latter doesn't have the extra engines for "comfort", it has them because it needs them.
I respect your opinion, choice and prejudices, but they are simply not rooted in fact. The accident at Heathrow airport is subject to an investigation and there has been no determination as to the cause. When the cause is determined it might well be the case that the common event would have been equally true to a 3 or 4 engine aircraft, we will just have to be patient and wait for the findings.
The aircraft you quote (747, A380, A340) have 4 engines because they need 4 engines to meet certification. The 747 has been a fine aircraft, but its role has now largely been replaced by the 777. The A340 has been outsold by its stablemate the A330. The A380 has 4 engines because there is no existing powerplant available to enable such a heavy aircraft to operate on two. Nevertheless to save weight thrust reversers have been stripped from 2 of the 4 engines. This aircraft is now and in the future going to be massively outsold by the smaller Boeing 787 and its own stablemate the A350 series.
Even now, but particularly in the coming years, if you will only fly overwater on 4 engine aircraft, your choice of destinations will be very limiting indeed. ETOPS is proven safe, has a 23 year unblemished safety record, is a product of modern technology and is here to stay.
In summary you can labour under whatever prejudice or opinion you choose. the threads author wanted reassurance on the safety of twin engine ETOPS aircraft over oceanic routes. My reply was to truthfully and factually supply that reassurance. BELARGUSA's reply was by his own admission slightly tongue-in-cheek and based on accounts of his favourite aircraft. If you don't accept the factual reality then that is fine, however your argument is fairly devoid of actual or factual reference and based on faith ( "Believe me").
What I actually said was a factual reply with a quick historical background, based on my 22 years of actually doing the job. I can assure you that there have been more accounts of simultaneous engine failure on 4 engine jets where the common event has been fuel starvation or contaminent ingestion and to this end it doesn't matter how many engines you have.
Another point to bear in mind is that 3 and 4 engine jetliners do not have the 3rd and or 4th engines as spares or for safety reasons. They have them because they need them. During certification ( and in service) an aircraft is required to be able to lose one of its power units at a critical speed and still be able ( at its maximum take off weight) to be able to safely climb away. For a twin engine aircraft ( with particular relevance to the ETOPS twins we are talking about), this means that having lost half of its power it can still climb away safely. That is not the case necessarily with a 4 engine aircraft which might need 75% of its available output to climb away safely.
Believe me, 4 engines DO have a higher intrinsic reliability.
If a plane ever ditches because an engine is out... it will be a twin". I agree
I respect your opinion, choice and prejudices, but they are simply not rooted in fact. The accident at Heathrow airport is subject to an investigation and there has been no determination as to the cause. When the cause is determined it might well be the case that the common event would have been equally true to a 3 or 4 engine aircraft, we will just have to be patient and wait for the findings.
The aircraft you quote (747, A380, A340) have 4 engines because they need 4 engines to meet certification. The 747 has been a fine aircraft, but its role has now largely been replaced by the 777. The A340 has been outsold by its stablemate the A330. The A380 has 4 engines because there is no existing powerplant available to enable such a heavy aircraft to operate on two. Nevertheless to save weight thrust reversers have been stripped from 2 of the 4 engines. This aircraft is now and in the future going to be massively outsold by the smaller Boeing 787 and its own stablemate the A350 series.
Even now, but particularly in the coming years, if you will only fly overwater on 4 engine aircraft, your choice of destinations will be very limiting indeed. ETOPS is proven safe, has a 23 year unblemished safety record, is a product of modern technology and is here to stay.
In summary you can labour under whatever prejudice or opinion you choose. the threads author wanted reassurance on the safety of twin engine ETOPS aircraft over oceanic routes. My reply was to truthfully and factually supply that reassurance. BELARGUSA's reply was by his own admission slightly tongue-in-cheek and based on accounts of his favourite aircraft. If you don't accept the factual reality then that is fine, however your argument is fairly devoid of actual or factual reference and based on faith ( "Believe me").
I've flown across the Atlantic numerous times on 2 & 4 engined planes as simple SLF and, even with the additional security of ETOPS approval, I do feel better looking out of my window and seeing 2 engines hung under the wing.
So where I have a choice and providing it isn't much more expensive I will always pay for the 4 engined option if available.
And, even though it is early days and a report isn't out yet, the BA 777 twin engine out at LHR has meant that I will keep this policy going for a while yet!
So where I have a choice and providing it isn't much more expensive I will always pay for the 4 engined option if available.
And, even though it is early days and a report isn't out yet, the BA 777 twin engine out at LHR has meant that I will keep this policy going for a while yet!
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During certification ( and in service) an aircraft is required to be able to lose one of its power units at a critical speed and still be able ( at its maximum take off weight) to be able to safely climb away. For a twin engine aircraft ( with particular relevance to the ETOPS twins we are talking about), this means that having lost half of its power it can still climb away safely. That is not the case necessarily with a 4 engine aircraft which might need 75% of its available output to climb away safely.
The aircraft you quote (747, A380, A340) have 4 engines because they need 4 engines to meet certification. The 747 has been a fine aircraft, but its role has now largely been replaced by the 777. The A340 has been outsold by its stablemate the A330. The A380 has 4 engines because there is no existing powerplant available to enable such a heavy aircraft to operate on two.