Virgin Scaremongering
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If Mr Branson really is saying this then I'd like to hear his view on the code sharing flights that operate with a VS flight number on twin engined aircraft. For example Singapore Airlines flights from Singapore to Brisbane in a B777.
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Actually, your statistical risk of engine failure would reduce the more engines you have - not increase. Someone (actually quite a few people here) slept through their stats classes! Think of it as a firing squad analogy ... if they are selecting every tenth person it's going to take very much longer for them to get to you if there are 1,000 people to choose from than if there are 100... 
However, if you have a problem where all the engines stop (ie you run out of fuel as with Transat) then it doesn't matter whether you have two or twenty.
For what it's worth, I agree with Branson in that logically it has to be safer - both from a perception and statistical viewpoint - to fly tris or quads rather than twins.
It's obviously something that certain airlines prefer as well - apart from the fact that as I have already pointed out, ETOPS certification is a long, drawn out and very expensive process - otherwise why would quads (A340, A380, B747-400) still be produced?
When I did research for the L10 op, there was a very definite preference amongst transatlantic pax for more than two engines.
Willowman - you said "The argument over 2 versus 4 is nonsense! Ask TWA or Swissair or the DC10 at Sioux City. The most likely cause of multiple engine failure is either something catastrophic or fuel contamination - in which case, it matters little as to how many engines you have.
Actually, only one of the incidents cited involved an engine problem (I'm assuming here you're referring to TW800 and SR111) - the DC10 at Sioux City. Considering that the principal problem was the lack of hydraulics rather than the loss of the #2, and the crew steered the aircraft in with variable thrust from 1 and 3, I'd say that you'd have a pretty major problem doing that with a twin that's just lost 50% of its engines!
Charliecossie - ETOPS aircraft require additional engineers (one for each side of the aircraft); additional systems monitoring, dedicated (and quarantined) parts; additional training for ops staff/dispatchers - the list is a long one. And as the recent Transat incident shows, mess up and you lose it - which then required (as in the case of Transat) that you need to change your fleet or lease in alternative tri or quad aircraft (Transat are leasing in World MD11s).
Slim_Slag - are you telling me that a 767's RB211-524B4s generate more than 75,000lbs of thrust each vs an L1011-500's three RB211-524B4s with 50,000lbs output?
I think you should tell Rolls (and BA) this!
However, if you have a problem where all the engines stop (ie you run out of fuel as with Transat) then it doesn't matter whether you have two or twenty.
For what it's worth, I agree with Branson in that logically it has to be safer - both from a perception and statistical viewpoint - to fly tris or quads rather than twins.
It's obviously something that certain airlines prefer as well - apart from the fact that as I have already pointed out, ETOPS certification is a long, drawn out and very expensive process - otherwise why would quads (A340, A380, B747-400) still be produced?
When I did research for the L10 op, there was a very definite preference amongst transatlantic pax for more than two engines.
Willowman - you said "The argument over 2 versus 4 is nonsense! Ask TWA or Swissair or the DC10 at Sioux City. The most likely cause of multiple engine failure is either something catastrophic or fuel contamination - in which case, it matters little as to how many engines you have.
Actually, only one of the incidents cited involved an engine problem (I'm assuming here you're referring to TW800 and SR111) - the DC10 at Sioux City. Considering that the principal problem was the lack of hydraulics rather than the loss of the #2, and the crew steered the aircraft in with variable thrust from 1 and 3, I'd say that you'd have a pretty major problem doing that with a twin that's just lost 50% of its engines!
Charliecossie - ETOPS aircraft require additional engineers (one for each side of the aircraft); additional systems monitoring, dedicated (and quarantined) parts; additional training for ops staff/dispatchers - the list is a long one. And as the recent Transat incident shows, mess up and you lose it - which then required (as in the case of Transat) that you need to change your fleet or lease in alternative tri or quad aircraft (Transat are leasing in World MD11s).
Slim_Slag - are you telling me that a 767's RB211-524B4s generate more than 75,000lbs of thrust each vs an L1011-500's three RB211-524B4s with 50,000lbs output?
I think you should tell Rolls (and BA) this!
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In the very recent past I have had two engine failures (not shutdowns) in wide-body ETOPS twins - I fly for a leading carrier. It is an interesting experience (discussed in the debrief in the bar after the event) to be flying around on one engine with approaching 400 pax down the back.
I hope you will forgive me for not joining in the statistical debate as I lie firmly in the "more engines is better camp"
Don't get the idea that I have been freaked out by my experiences, it is just that generally an engine failure on a quad is only a minor inconvenience whereas on a twin options can be very limited
The logistical and communications work load (as you divert to one of the most inhospitable airfields on earth - try Siberia in Winter) on the crew is very high.
The argument of twin over quad v.v. is not about the number of engines - it is where you take those engines. An engine failure in a twin around the US or through Europe is no big problem. You are probably at top of descent for at least 20 major airfields with ATC providing a radar vector and copious amounts of coordination assistance
It is a different story when you are faced with ATC language problems (perhaps on HF), limited airfields (some > 800 nm away and with ATC on an on-call basis - will they be there and do they speak English) and crap weather.
I can assure you that diverting on your ETOPS twin in certain parts of the World can be a lonely experience.
On the bright side FANS, in particular the Comms side of it, will improve things markedly.
I hope you will forgive me for not joining in the statistical debate as I lie firmly in the "more engines is better camp"
Don't get the idea that I have been freaked out by my experiences, it is just that generally an engine failure on a quad is only a minor inconvenience whereas on a twin options can be very limited
The logistical and communications work load (as you divert to one of the most inhospitable airfields on earth - try Siberia in Winter) on the crew is very high.
The argument of twin over quad v.v. is not about the number of engines - it is where you take those engines. An engine failure in a twin around the US or through Europe is no big problem. You are probably at top of descent for at least 20 major airfields with ATC providing a radar vector and copious amounts of coordination assistance
It is a different story when you are faced with ATC language problems (perhaps on HF), limited airfields (some > 800 nm away and with ATC on an on-call basis - will they be there and do they speak English) and crap weather.
I can assure you that diverting on your ETOPS twin in certain parts of the World can be a lonely experience.
On the bright side FANS, in particular the Comms side of it, will improve things markedly.
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Guvnor,
Surely statistically each engine failure is an independent event, if there are 4 engines then each one has an equal chance of failing??
So statistically if one engine fails, the others still have the same chance of failing, they do not somehow become less, or more likely to fail.
I don't think your analogy works, as no matter how many engines you have on your aircraft, there are still the same number of engines overall, and therefore each one still has the same chance of failure.
I am sure if I also slept through my stats class you will let me know !!!
Surely statistically each engine failure is an independent event, if there are 4 engines then each one has an equal chance of failing??
So statistically if one engine fails, the others still have the same chance of failing, they do not somehow become less, or more likely to fail.
I don't think your analogy works, as no matter how many engines you have on your aircraft, there are still the same number of engines overall, and therefore each one still has the same chance of failure.
I am sure if I also slept through my stats class you will let me know !!!
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hi folks.....reminds me of this joke..
the 2-eng pilot and the 4-eng pilot over the north atlantic, discussing what is better and the 4-eng guy asking the other one:
do you want to know why i still fly 4-eng over the north atlantic????because they didn`t build a 6-eng aircraft yet!!
(well... except maybe the b52 and this russian thing)
the 2-eng pilot and the 4-eng pilot over the north atlantic, discussing what is better and the 4-eng guy asking the other one:
do you want to know why i still fly 4-eng over the north atlantic????because they didn`t build a 6-eng aircraft yet!!
(well... except maybe the b52 and this russian thing)
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I would like to know what right that w*****r Branson has to critisize anyone's safety if there is no safety issue there in the first place. BA/UA/AA/AC/KL/AZ/AF/SAS and dozens of others have flown SAFELY accross the pond everyday in twins so where does he get his s**t from. There are more twins then quads flying the Atlantic. He is in the same class as EasyBleak, always crying and throwing his toys out of the cot when he doesn't get his own way. Very poor up bringing and smacks of a bad case of 'only child syndrome'. He is a very desperate man and will do ANYTHING to discredit any company in order to try gain the advantage. And in case you are wondering, I am a 747 pilot, and No, I can't stand the man! He so needs to GROW up. 'My Opinion' 
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Exactly Mode 7, getting back to the point of this thread! The debate on the safety of 4 eng. over two is not really the issue here. Aren't you more likely to be killed by a bee sting than an air accident? What I find pretty disgusting, as I've said before, is Branson's rather desperate, headline grabbing, comments. How would he feel if National Express coachs were to advertise there services as safer than traveling by train?
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The Guvnor
'Fraid you are speaking b******S !
If PK 1 eng fail = 10-3 / hr (say), then for 2 Eng ac PK an engine failure is a little less than 2 x 10-3 (in fact 10-6 less). In a 4 eng ac it is a bit less than 4 x 10-3 i.e. as you would expect, all else being equal about twice as likely you would have an engine failure on a quad than a twin.
When you have finished revising your stats, get your aerodynamics books out! You go on to imply the choice between twin and quad is purely preference. It is not. The original A330 / A340 were almost identical bar the A330 was a twin and had no centre tank. Why? Lack of Wing Bending moment relief due no OB engines. So for long range, it is easier in a quad due to the OB engines...
NoD
'Fraid you are speaking b******S !
If PK 1 eng fail = 10-3 / hr (say), then for 2 Eng ac PK an engine failure is a little less than 2 x 10-3 (in fact 10-6 less). In a 4 eng ac it is a bit less than 4 x 10-3 i.e. as you would expect, all else being equal about twice as likely you would have an engine failure on a quad than a twin.
When you have finished revising your stats, get your aerodynamics books out! You go on to imply the choice between twin and quad is purely preference. It is not. The original A330 / A340 were almost identical bar the A330 was a twin and had no centre tank. Why? Lack of Wing Bending moment relief due no OB engines. So for long range, it is easier in a quad due to the OB engines...
NoD
From memory, BA average 0.3 million crashes per million flights. The risk in taking a flight is thus infinitesimally small. I subjectively prefer 4 engines, but 2 is safe enough for me.
Also from memory, KAL is 38 per million flights. I would rather be on a BA twin than a KAL jumbo. If I catch a flight every day for 72 years I have an evens chance of getting killed on KAL. Again, infinitesimmaly small, though it could be tomorrow. Personally, I would rather not fly KAL, but then perhaps I am just being silly.
Most passengers, whether subjectively or because they have thought about it, don't give a toss how many engines the plane has. Equally, most will say they prefer 4 engines.
So people who pick a flight based on seat spacing and cabin service are actually being more objective than those who count the engines!
Also from memory, KAL is 38 per million flights. I would rather be on a BA twin than a KAL jumbo. If I catch a flight every day for 72 years I have an evens chance of getting killed on KAL. Again, infinitesimmaly small, though it could be tomorrow. Personally, I would rather not fly KAL, but then perhaps I am just being silly.
Most passengers, whether subjectively or because they have thought about it, don't give a toss how many engines the plane has. Equally, most will say they prefer 4 engines.
So people who pick a flight based on seat spacing and cabin service are actually being more objective than those who count the engines!
Paxing All Over The World
At the moment, I am rather more concerned about what kind of tail fin the machine has, rather than how many engines it will shake off when it fails. 
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As had been pointed out, Guv, your statistics are not correct. You may be thinking of the probability of a particular engine failing given that one will fail.
Also, the Sioux City DC10 that crashed was UA232. The hydraulics lack was a direct result of catastrophic failue of the #2 engine.
Also, the Sioux City DC10 that crashed was UA232. The hydraulics lack was a direct result of catastrophic failue of the #2 engine.
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Its dog-eat-dog in the industry now so I'm not surprised someone has come out with a statement like this.
I'm equally not surprised that it was Branson who put his head above the parapet first. (What was that about fools and angels?)
I'm equally not surprised that it was Branson who put his head above the parapet first. (What was that about fools and angels?)
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I thought I would throw my two cents in regarding ETOPS. I think everyone would prefer 4 engines over 2 while flying over inhospitable terrain. There are a few points that ought to be considered though. One is that you are more likely to have an engine failure on a 4 engine transport, both statisticaly, and the fact that they don't have to be maintained according to ETOPS criteria. Secondly, and more importantly, 4 engine transports are not required to have long term fire suppression systems installed in their cargo compartments. ETOPS aircraft are. It has to be able to suppress a cargo fire for the duration of whatever ETOPS length it is certified to fly. Given the fact that we have had more accidents as a result of cargo fire than engine failure it is an important point to consider if you are talking about 4 vs. 2 engines.
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Of course, it doesn't matter how many engines you have if several people crowd your cockpit and slot your throat with boxcutters.
I have heard anecdotal evidence that passengers are drifting away from the airlines that are perceived to have sloppy practices regarding locking the cockpit door.
The industry needs to sort this issue out. It has become both a terrorist and a commercial threat.
I have heard anecdotal evidence that passengers are drifting away from the airlines that are perceived to have sloppy practices regarding locking the cockpit door.
The industry needs to sort this issue out. It has become both a terrorist and a commercial threat.
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Etops rules are not consistent....... American aircraft require two maintenance teams , one for each side of the aircraft, whereas European/British do not stipulate this except for certain items like IDG and Back up generators maintenance.
Nigelondraft : Difference in RB211-524G/H standard for Etops .......component parts and also EGT margin, I have several times pulled a 211 from a 767 with a reduced EGT margin as a serviceable engine for it to be put on a non-Etops a/c.
Nigelondraft : Difference in RB211-524G/H standard for Etops .......component parts and also EGT margin, I have several times pulled a 211 from a 767 with a reduced EGT margin as a serviceable engine for it to be put on a non-Etops a/c.
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SLF3 "From memory, BA average 0.3 million crashes per million flights. The risk in taking a flight is thus infinitesimally small.
I think BA might take exception to your arithmetic!
Think this belongs in the 'I know what you meant' department
I think BA might take exception to your arithmetic!
Think this belongs in the 'I know what you meant' department
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First time I've said this (joining a big club)....
Guvnor, you don't know what you're talking about.
Every day, I carry out ETOPS checks. I've done the following - UA, MK, LI, BA, US, CO, HM, BI, UM, LA and Martinair (forgot their code). Big enough list for you?
Anyway, only CO require two individuals to carry out the check. The rest are all happy with one person.
Nigel:
If you look at the 767 DDM there are really not a lot of things that kill it's ETOPS ability entirely. Some things reduce it to 138, some reduce it to 120. Even a dead APU is a non-event! (120 ETOPS).
Regarding the engines - reduced EGT margins is hardly a maintenance issue, it's a worn engine issue. They're always gonna wear out. AFAIK, all BA 211G/H's are the same i.e. built to ETOPS standard with ETOPS components.
[ 20 November 2001: Message edited by: charliecossie ]
Guvnor, you don't know what you're talking about.
Every day, I carry out ETOPS checks. I've done the following - UA, MK, LI, BA, US, CO, HM, BI, UM, LA and Martinair (forgot their code). Big enough list for you?
Anyway, only CO require two individuals to carry out the check. The rest are all happy with one person.
Nigel:
If you look at the 767 DDM there are really not a lot of things that kill it's ETOPS ability entirely. Some things reduce it to 138, some reduce it to 120. Even a dead APU is a non-event! (120 ETOPS).
Regarding the engines - reduced EGT margins is hardly a maintenance issue, it's a worn engine issue. They're always gonna wear out. AFAIK, all BA 211G/H's are the same i.e. built to ETOPS standard with ETOPS components.
[ 20 November 2001: Message edited by: charliecossie ]
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Guys,and Gals, (sorry)
We can argue the point of 2 vs. 4 engines untill the cows come home. I just got back from a long trip over grey cold water in a twin engine (oops almost started).
RB is not stupid he may be broke (just over extended), however he is focusing his press release on his fare-paying customers, and he is making a point the average Joe would prefer to look out the window of his reclining seat to see two engines on either side. The more the merrier!!
RB is not as bad off as BA (700+ mill. loss) and I am sure his far-east backer must have had some say in this "open letter".
I have been on several reposition flights across bodies of water (and mountain ranges...) in twin engine aircraft and choose a respectable airline hoping their mx is as reliable as my outfit. September 11 has woken up most PR departments in trying to find an edge over the competition,
Lovely 'uncle sam' ad from Ryanair,
Every other low cost 'no frill' following with 'sales'
BA working it's *ss off getting the concorde airborne,
I am afraid to admit it has become a war of the words and RB found an angle WE may not agree with but the average schmuck can probably identify with.
Now lets hear it from the statiticians out there....
edited to stay politically correct, sorry girls...
[ 20 November 2001: Message edited by: lrjt45 ]
We can argue the point of 2 vs. 4 engines untill the cows come home. I just got back from a long trip over grey cold water in a twin engine (oops almost started).
RB is not stupid he may be broke (just over extended), however he is focusing his press release on his fare-paying customers, and he is making a point the average Joe would prefer to look out the window of his reclining seat to see two engines on either side. The more the merrier!!
RB is not as bad off as BA (700+ mill. loss) and I am sure his far-east backer must have had some say in this "open letter".
I have been on several reposition flights across bodies of water (and mountain ranges...) in twin engine aircraft and choose a respectable airline hoping their mx is as reliable as my outfit. September 11 has woken up most PR departments in trying to find an edge over the competition,
Lovely 'uncle sam' ad from Ryanair,
Every other low cost 'no frill' following with 'sales'
BA working it's *ss off getting the concorde airborne,
I am afraid to admit it has become a war of the words and RB found an angle WE may not agree with but the average schmuck can probably identify with.
Now lets hear it from the statiticians out there....
edited to stay politically correct, sorry girls...
[ 20 November 2001: Message edited by: lrjt45 ]
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Probability:
Lets say the probability of any single engine failing is 0.1 (for arguments sake)
So... on a twin the probabiltiy of losing any one engine or 50% of available thrust is 0.1x2 (two engines) or 0.2
The probabilty of losing 100% thurst ie engines 1 & 2 is 0.1x2 (the prob of 1 engine failing in the 1st place)multiplied by 0.1 (the probability of the remaining engine failing)or 0.02
On a quad the probability of losing any one engine (or 25% of available thrust) is 4x0.1 or 0.4 - That is: twice as likely for a single engine failure.
However probability of losing two engines or 50% of available thrust is (4x0.1)x(3x0.1)=0.12 This is almost half the probability of a failure resulting a 50% thrust reduction on a twin.
The probability of a quad losing 100% thrust or all 4 engines is (4x0.1)x(3x0.1)x(2x0.1)x(1x0.1) or 0.0024.
Nearly 100 times less likely!
[ 20 November 2001: Message edited by: Theo Racle ]
Lets say the probability of any single engine failing is 0.1 (for arguments sake)
So... on a twin the probabiltiy of losing any one engine or 50% of available thrust is 0.1x2 (two engines) or 0.2
The probabilty of losing 100% thurst ie engines 1 & 2 is 0.1x2 (the prob of 1 engine failing in the 1st place)multiplied by 0.1 (the probability of the remaining engine failing)or 0.02
On a quad the probability of losing any one engine (or 25% of available thrust) is 4x0.1 or 0.4 - That is: twice as likely for a single engine failure.
However probability of losing two engines or 50% of available thrust is (4x0.1)x(3x0.1)=0.12 This is almost half the probability of a failure resulting a 50% thrust reduction on a twin.
The probability of a quad losing 100% thrust or all 4 engines is (4x0.1)x(3x0.1)x(2x0.1)x(1x0.1) or 0.0024.
Nearly 100 times less likely!
[ 20 November 2001: Message edited by: Theo Racle ]