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Whats Wrong With A340 Engines?  
User currently offlineUAEflyer From United Arab Emirates, joined Nov 2006, 1164 posts, RR: 1
Posted (6 years 12 months 4 days 2 hours ago) and read 22701 times:

I was thinking about the four engined aircrafts especially the A340, As the fact says that this model didn't make much success such as the two engine aircrafts like the B777 & A330.
My question is, is it because the four engines of A340 is normal engines not turbo fans or the secret is something else.
To me personally i feel more safer in a four engine aircraft, and the aircraft appearance looks cooler with it.

134 replies: All unread, showing first 25:
 
User currently offlineOceansWorld From , joined Dec 1969, posts, RR:
Reply 1, posted (6 years 12 months 4 days 2 hours ago) and read 22697 times:

Quoting UAEflyer (Thread starter):
is it because the four engines of A340 is normal engines not turbo fans or the secret is something else.

The A340 is powered by four turbofan CFM56-engines.

http://www.cfm56.com/index.php?level2=engines&level3=cfm56-5c

[Edited 2007-12-31 07:27:31]

User currently offlineStitch From United States of America, joined Jul 2005, 31440 posts, RR: 85
Reply 2, posted (6 years 12 months 4 days 2 hours ago) and read 22538 times:
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Quoting UAEflyer (Thread starter):
My question is, is it because the four engines of A340 is normal engines not turbo fans or the secret is something else.

The secret is four engines burn more fuel then two, require more structure to support, and offer twice as many chances for something to break which requires a departure delay to fix.

Quoting UAEflyer (Thread starter):
To me personally i feel more safer in a four engine aircraft, and the aircraft appearance looks cooler with it.

I feel safe enough with two engines, but I do agree with you that the A340 looks better to me then the A330 because it has two more engines which "balances out" her look to my eyes.


User currently offlineVirgin747 From Canada, joined Oct 1999, 319 posts, RR: 0
Reply 3, posted (6 years 12 months 4 days 2 hours ago) and read 22419 times:



Quoting OceansWorld (Reply 1):
The A340 is powered by four turbofan CFM56-engines.

That would be the case of the A340-200/300 series. Where as the 500/600 series uses the Rolls-Royce Trent.
I think the switch was a good move, the CFM56 works great on a 737 or an A320 series airplane. Its a really good fuel saving idea. But climb and speed performace gets sacrificed as a result. The inside joke is the 200/300 series is powered with hair dryers... The 500/600 series benefitted with a larger engine, look at the 500. The only thing that stands in its way of being the totally dominant plane is the 777LR. Both planes can stay aloft for a very very very long time.

As for the safety issue, you dont hear complete engine loss in the media much these days. Engines are tested to the max, and regulations are there to make sure twin jets are a certain distance close to a airport if something should happen. Also bear in mind, historically any time there was a double engine loss on a twin, it was because all three planes (Air Canada 767 1983 ???? Air Transat A330 2001) ran out of fuel. Also there has been a case of a quad jet losing all 4 engines flying through volcanic ash. In conclusion no matter what cards you have, if fate plays its card you're still toast.


User currently offlineBoeingluvr From , joined Dec 1969, posts, RR:
Reply 4, posted (6 years 12 months 4 days 1 hour ago) and read 22290 times:

What series of A340 are we refering to? Perhaps he is talking about the A342 and A343 that have the APU engines and terrible climb performance.

User currently offlineGDB From United Kingdom, joined May 2001, 13254 posts, RR: 77
Reply 5, posted (6 years 12 months 4 days 1 hour ago) and read 22259 times:

No, not APU engines, or such a terrible climbout, just that back in 1987, when A330/A340 were formally launched, CFM-56 seemed the best bet. They did want something else, but the proposed IAE Superfan project never got anywhere.
In fact, Airbus had been mooting a modernised, longer, A300 fuselage cross section airliner, with 4 x CFM's, as far back as 1982, the TA11 proposal.


User currently offlineMD80fanatic From United States of America, joined Apr 2004, 2661 posts, RR: 9
Reply 6, posted (6 years 12 months 4 days 1 hour ago) and read 22196 times:



Quoting Stitch (Reply 2):
The secret is four engines burn more fuel then two,

Not on a thrust per pound of fuel basis....they are the same. You need to compare total thrust vs. total fuel burn to get a fair outlook. 4 GE-90s burn more than two GE-90s...that's apples to apples. To simply say 4 burns more than 2 because 4 is larger than two numerically is leaving out 95% of the comparison.


User currently offlinePhatty3374 From United States of America, joined Apr 2005, 136 posts, RR: 0
Reply 7, posted (6 years 12 months 4 days 1 hour ago) and read 22127 times:



Quoting Boeingluvr (Reply 4):
What series of A340 are we refering to? Perhaps he is talking about the A342 and A343 that have the APU engines and terrible climb performance.

I assume he was talking about the A342/A343 as they have simply average climb performance with their 'hairdryer-esque' CFM-56's. No reason to knock on the A345/A346 as they are more aptly powered with higher thrust RR Trent engines.

Random question about the CFM-56 powered A340's: I know it's an airline option to add more noise insulation in the fuselage skin (pardon the lack of technical terms), but say one airline has an A343 and an A346 with the same amount of insulation installed; due to the lower thrust of the CFM-56's on the 343, would that plane be noticeably quieter than a 346 of the same company?

Thanks


User currently offline747fan From United States of America, joined Jun 2007, 1192 posts, RR: 1
Reply 8, posted (6 years 12 months 4 days 1 hour ago) and read 22131 times:

Even though the A342/A343 is often considered "underpowered" on this forum, the CFM56 was definitely a good choice for this aircraft. Yes, its not as fuel efficient as an A330, 777, 767, etc., but that's obviously due to the 2 extra engines. But it does come pretty close to matching these planes in efficiency, and is also more efficient than any 747, even the 747-400 - especially on true long haul flights (such as US-Eastern Europe or US West Coast-Europe, not US East Coast-LHR/CDG/FRA, etc.). Not to mention that the CFM is one of the most reliable engines around. So really, there's nothing wrong with A340 engines. CFM-powered A340's may not exactly be vigorous on takeoff like a 767/777 (well, they actually can be on shorter flights such as Olympic's ATH-LHR), but they do get the job done, and are quite efficient on longer-haul flights.

User currently offline747fan From United States of America, joined Jun 2007, 1192 posts, RR: 1
Reply 9, posted (6 years 12 months 4 days 1 hour ago) and read 22038 times:



Quoting Phatty3374 (Reply 7):
I assume he was talking about the A342/A343 as they have simply average climb performance with their 'hairdryer-esque' CFM-56's. No reason to knock on the A345/A346 as they are more aptly powered with higher thrust RR Trent engines.

Even the Trent-powered A346's don't exactly have vigorous T/O/climb performance, although they're an improvement over the A340 "classic." Just go spotting at JFK or ORD in the evening and you'll see that they have comparable performance to a 744 rather than an A330/767/777. The A345's TO performance seems to be quite good, especially when taking off for flights that are not very long compared to their capability, such as JFK-HAM and LHR-AUH. When I spotted at JFK, EK's A345 to HAM put on quite an impressive performance with its short TO run and impressive climbout. Not to mention that those RR Trents sound GREAT! The CFM's have a neat, distinctive growl when taking off as well (especially on the outside), and almost sound eerie when you're spotting them from a distance (such as along the bridge over Jamaica Bay near JFK).


User currently offlineStitch From United States of America, joined Jul 2005, 31440 posts, RR: 85
Reply 10, posted (6 years 12 months 4 days 1 hour ago) and read 22032 times:
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Quoting MD80fanatic (Reply 6):
Not on a thrust per pound of fuel basis....they are the same.

Actually two 100K GE90s would likely burn less fuel then four 50K GE90s, but your general point is taken.

However, I wasn't trying for an answer on a purely technical basis. It is known that the A340's four engines burn more fuel on a similar mission then the A330's and 777's two, even though both airframes use different engines. And that is one of the reasons why the A340's sales are not as robust as the A330's or 777's which is one of the questions the OP had.


User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 11, posted (6 years 12 months 4 days ago) and read 21936 times:



Quoting 747fan (Reply 8):
But it does come pretty close to matching these planes in efficiency, and is also more efficient than any 747, even the 747-400 - especially on true long haul flights (such as US-Eastern Europe or US West Coast-Europe, not US East Coast-LHR/CDG/FRA, etc.).

Not true! The 744 is a very efficient aircraft. Up until the 380 was introduced the 744 had the lowest direct operating costs on a per seat basis, especially at long range. The 777/330 does a better hob on medium range routes.


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 12, posted (6 years 12 months 3 days 23 hours ago) and read 21740 times:



Quoting UAEflyer (Thread starter):
My question is, is it because the four engines of A340 is normal engines not turbo fans or the secret is something else.

They are turbofans, and pretty good ones at that. A major issue with the performance of the original A340 was that it was supposed to have IAE Superfans but IAE pulled out of the project. They had to scramble and find something to recover with.

Quoting MD80fanatic (Reply 6):
Quoting Stitch (Reply 2):
The secret is four engines burn more fuel then two,

Not on a thrust per pound of fuel basis....they are the same.

No, they're not. Larger engines have better SFC, all other things being equal. If an aircraft needs, say, 100,000 lbs of thrust to meet certification requirements you can do that with 4 x 33,000 lbs or 2 x 100,000 lbs. The twin will have better fuel consumption because a 100,000 lbs engine will have better SFC than a 33,000 lbs one (assuming equal engine generations).

Tom.


User currently offlineSEPilot From United States of America, joined Dec 2006, 7201 posts, RR: 50
Reply 13, posted (6 years 12 months 3 days 22 hours ago) and read 21371 times:



Quoting PhilSquares (Reply 11):

Not true! The 744 is a very efficient aircraft.

According to the charts posted in Tech/Ops this is not true. Many aircraft available today beat it on a cost per seat/mile basis; the A333 and the 77W beat it by a substantial margin, as does the A380. As to the 2 versus 4 engine safety debate, it is my contention that 2 engines are safer than 4, as the most likely engine event that will lead to a crash is an uncontained engine failure, and the chance of that is twice on a quad what it is on a twin. Engine reliability is such that the chance of two unrelated failures occurring on a twin are extremely remote. I do not know of a single case in all the time that commercial jets have been flying that there have been two unrelated failures on any jetliner (counting all the quads that have been flying since the jet age started) and that goes back before ETOPS was even thought of. If anyone knows of a case please let me know.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineLightsaber From United States of America, joined Jan 2005, 13552 posts, RR: 100
Reply 14, posted (6 years 12 months 3 days 22 hours ago) and read 21322 times:
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Quoting Stitch (Reply 2):

The secret is four engines burn more fuel then two, require more structure to support, and offer twice as many chances for something to break which requires a departure delay to fix.

The main issue with the A345/A346 is weight. The airframe was overweight and that wasn't helped by the ~6 extra metric tons of weight a four engine/nacelle airframe has to lift compared to if the A345/A346 had been made a two engine airframe.

Quoting Stitch (Reply 10):
Actually two 100K GE90s would likely burn less fuel then four 50K GE90s, but your general point is taken.

That is very true. Every engine is developed with a certain set of technology. One bit of that technology is the clearance between the blade tips and the casings. This dimension is the same for a 118' diameter engine or a 97.4" diameter engine (like the Trent 500). In other words, it is why the trent 500 has a ~0.030 worse cruise TSFC than the GE-90 despite being a newer technology engine. (0.530 for the GE-90-115, IIRC (I'm going off memory)). 6% is HUGE! Its not that the engines are bad, bigger is just inherently more efficient.

Also, a smaller engine has a greater internal surface area to thrust. Internal 'flow path' surface area can be translated to the layman as 'power loss.' So proportionately, higher thrust engines will always be more fuel efficient.

The 'rule of thumb' in both aerospace and ships is "Three for two." If you want to make something three times as big, it ends up costing twice as much. Now... this isn't 100% true. Why? Big planes end up having a lot more put into them (for range) and their lower production volumes end up hitting the costs too. Its one reason they draw a curve through airframes by size (on the x-axis) to compare their equivalent technology.  spin 

Not to mention the added weight of four engines hurts the A340. Weight is always the enemy of an airframe. Now, due to today's technology limits on engine thrusts, there are airframe sizes upon which four engines is more efficient than a three engine airframe. But we already have a thread a month on "why no more 3-holers." How many times can we talk about the large weight penalty of putting an engine on the tail. Its ok for a business jet... but there is a reason the Hondajet put the engines above the wings.

Quoting Tdscanuck (Reply 12):
Larger engines have better SFC, all other things being equal. I

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Lightsaber



Societies that achieve a critical mass of ideas achieve self sustaining growth; others stagnate.
User currently offlineUAEflyer From United Arab Emirates, joined Nov 2006, 1164 posts, RR: 1
Reply 15, posted (6 years 12 months 3 days 22 hours ago) and read 21073 times:

Now i am confused, are the A340-500 engines turbofan or not?
and what is the difference between the turbofan engines than the normal one, furthermore which one of the is better for the environment, nowadays the global warming is a serious issue and it affected many people including my self.


User currently offlinePlaneInsomniac From Canada, joined Nov 2007, 686 posts, RR: 0
Reply 16, posted (6 years 12 months 3 days 21 hours ago) and read 20826 times:

As far as four vs. two engines is concerned: Here is a, probably quite silly, theoretical consideration.

For all I know, the most critical point for a plane is when it is between V1 and V2 during takeoff. Commercial airliners have to be designed so that they can take off and return safely to the airport if one of their engines fails in this phase. Now, assuming that an airplane requires approx. n pounds of thrust to safely take off, wouldn't that mean that in a two engine plane both engines combined have to produce 2n pounds of maximum thrust? On the other hand, in a four engine plane, all engines combined only have to produce 1.333 * n pounds of thrust? (When one engine fails, the remaining three have to produce n pounds, meaning each has to produce 0.333 * n.)

Now, assuming (possibly quite incorrectly) that the weight of an engine approximately scales with its maximum thrust required in this situation, wouldn't that mean that the overall weight of the engines carried is less for a four engine plane than for a two engine plane? And possibly a similar consideration can be made for fan diameters and associated aerodynamic drag.

I know that this neglects a number of significant factors - engine housings, pylons, wing infrastructure, as well as maintenance costs etc. It is quite obvious that the 777, 330, and of course also the 787 and 350 are far superior to the 340s. However, I would be interested to hear whether my little thought experiment makes any sense at all.



Am I cured? Slept 5 hours on last long-haul flight...
User currently offlineDfwRevolution From United States of America, joined Jan 2010, 1001 posts, RR: 51
Reply 17, posted (6 years 12 months 3 days 21 hours ago) and read 20550 times:



Quoting PlaneInsomniac (Reply 16):
Now, assuming (possibly quite incorrectly) that the weight of an engine approximately scales with its maximum thrust required in this situation, wouldn't that mean that the overall weight of the engines carried is less for a four engine plane than for a two engine plane?

The problem is with your assumption. Engine thrust does not directly correlate to engine weight.

With large turbofan engines, much of the weight is concentrated in the turbine core. Fan blades today are made of exotic materials like hollow titanium and carbon fiber, so there isn't that much weight penalty to scaling up the fan diameter. Granted with a twinjet you have to scale up the core turbine as well, but you will almost always come out ahead versus having four turbines.

If you look at the 777LR and A340NG especially, the four Trent 500 engines weigh more than the two Ge90 engines and actually put out slightly less thrust and burn more fuel.


User currently offlineA342 From Germany, joined Jul 2005, 4722 posts, RR: 3
Reply 18, posted (6 years 12 months 3 days 21 hours ago) and read 20495 times:



Quoting UAEflyer (Reply 15):
Now i am confused, are the A340-500 engines turbofan or not?
and what is the difference between the turbofan engines than the normal one, furthermore which one of the is better for the environment, nowadays the global warming is a serious issue and it affected many people including my self.

EVERY jet-powered airliner in use nowadays has turbofans.



Exceptions confirm the rule.
User currently offlineVega From , joined Dec 1969, posts, RR:
Reply 19, posted (6 years 12 months 3 days 20 hours ago) and read 20083 times:

Since around 2004, the only 340-300 in production is the higher thrust "E" model - A340-313E. Has anyone experienced a significant difference in takeoff performance with the "E" versus the earlier models? In other words, does the 340-300 "hair dryer" tag still apply for the "E".

User currently offlineEBJ1248650 From United States of America, joined Jun 2005, 1932 posts, RR: 1
Reply 20, posted (6 years 12 months 3 days 20 hours ago) and read 19974 times:



Quoting 747fan (Reply 9):
Even the Trent-powered A346's don't exactly have vigorous T/O/climb performance, although they're an improvement over the A340 "classic." Just go spotting at JFK or ORD in the evening and you'll see that they have comparable performance to a 744

A340-600 is a bigger airplane than the A340-500; bigger than the A340 classics too, so it's no surprise it's not as spritely as the -500 or the 767. Still it's a great airplane and it's a shame it hasn't done better on the market than it has.



Dare to dream; dream big!
User currently offline9V-SPJ From United States of America, joined Dec 2000, 752 posts, RR: 0
Reply 21, posted (6 years 12 months 3 days 19 hours ago) and read 19290 times:

The difference between a turbofan and a turbojet is that the turbofan has a large fan which is the first part of an engine the incoming airflow sees. The CFM engines are low bypass ratio engines which means that the ratio of air going through the entire engine ('hot') to the air going through just the fan ('cold') is fairly small. If you look at the GE90, these are high bypass ratio engines. As mentioned above, all civilian aircraft flying today are turbofan engines. By mixing cold and hot exhaust, the noise produced by the engine is reduced significantly when compared to a regular turbojet engine.

You can't really term the A340s as bad performers with respect to their flying qualities. Yes, the 200 and 300 series do have underrated engines, but that only affects their climb performance, not their cruise, descent or landing performance (directly).

9V-SPJ


User currently offlineIrish251 From Ireland, joined Nov 2004, 982 posts, RR: 4
Reply 22, posted (6 years 12 months 3 days 19 hours ago) and read 19126 times:



Quoting 9V-SPJ (Reply 21):
You can't really term the A340s as bad performers with respect to their flying qualities. Yes, the 200 and 300 series do have underrated engines, but that only affects their climb performance, not their cruise, descent or landing performance (directly).

When I read these regular threads about the A342/343 climb performance, I wonder whether those posing the question have ever seen an older jet airliner such as a 707, DC-8 or early 747-100/200, taking off on a long-distance flight. Those aircraft really were sluggish climbers by today's standards, but I don't think it was suggested that this was somehow dangerous. It was accepted as the norm for the time, but once the big modern fans became available, these conferred takeoff performance that was way ahead of what their predecessors could achieve.


User currently offlineViscount724 From Switzerland, joined Oct 2006, 26029 posts, RR: 22
Reply 23, posted (6 years 12 months 3 days 19 hours ago) and read 19099 times:



Quoting A342 (Reply 18):
EVERY jet-powered airliner in use nowadays has turbofans.

If not mistaken, all jet airliners built since about the mid-1960s have used turbofans with one notable exception -- Concorde.


User currently offlineAlangirvan From New Zealand, joined Nov 2000, 2106 posts, RR: 1
Reply 24, posted (6 years 12 months 3 days 19 hours ago) and read 19036 times:

The A340 does not need a brilliant Take Off performance if you have a long enough runway. The original A340 - I think it was called the TA-11- was part of the group of planes that Airbus wanted to do in the early 80s, when they had their first success with the A300. In 1981 you would see the design that became the A320, the A330-300 and they wanted to do the A380 even then (that is, long range planning.)

In those days the A340 was going to be a lot smaller, about the size of an A310 with four engines. But then Business Class was invented, and the A340 had to grow to accommodate all the C or J class passengers.

The A340 was four engines because EROPS was only proposed in the early 80s and TWA and AA started doing it in 1985. Pam Am started doing some EROPS with A310s, but Airbus was always a bit behind Boeing.

Airbus did respond to EROPS by making the A330-200 but they stuck to four engines for their very long range plane. They did not think the 777 would have such a trouble free entry into service.

If Airbus had been worried about the A340 being underpowered, they could have used PW2037s or RB211-535s ( about 37 000 to 41 000lb.) If you compare A340 T/O with first generation planes 707s and DC-8s with JT3DS the performance is respectable.


25 N1120A : If you fill the 744, even medium range routes go to the Jumbo. No they don't. The CASM of the 744 was the lowest until the A380 entered service.
26 Thegeek : That's not true. The CFM56 engines are high bypass as well. The GE90's have a bit higher pressure ratios and probably higher turbine inlet temperatur
27 9V-SPJ : I stand corrected! Thanks Thegeek! Just looked it up and found the CFM56's on the A340 have a bypass ratio of 6.0 and the GE90-115B has a bypass ratio
28 Post contains images A342 : The JT-8D is still around in huge numbers. Even the -200 series is generally considered low-bypass. Can you prove it? -------------------------------
29 Cedarjet : Just to explain one thing, a turbofan is, as has been said, the engine type used on every jet transport since the early 60s. The Comet 1 and 4, and th
30 N1120A : Can you disprove it?
31 A342 : Both is possible, and has been done many times, mostly in fighters, but also in some bombers.
32 Post contains links SeaBosDca : I have no problem with the A340, but it's a stretch to claim it has good takeoff performance. I did a thrust-to-weight ratio comparison for another t
33 Tdscanuck : In all current cases, the inlet slows the incoming air to subsonic before it reaches the fan face. So far, there are no production engines that take
34 Thegeek : Good point. I forgot about the MD80 planes. In Australia, there are a single digit number of low-bypass powered airliners, but that's not true in the
35 Post contains images Zeke : Rather simplistic, a A330 with the same range/payload as a A340 would need a heavier wing than the A340 to lift the fuel as the outer engine provides
36 N1120A : Fuel consumption per seat mile is not the only component of CASM. Further, LH's configuration doesn't account for the fact that their 744s are compar
37 RFields5421 : Actually I think the calendar rather than the specifics of the aircraft/ engines have more to do with the A340 relative lack of success vs the B747. B
38 A342 : Sure it's not a STOL aircraft, but comparing its takeoff field length charts to those of other aircraft shows that it can compete well. It is also do
39 Post contains images 747fan : I've seen my share of heavy 747-100 takeoffs, in addition to a few longhaul A340 (classic and NG) departures, and you couldn't be more correct. From
40 Seabosdca : Have you found you have to use full power more often with the 343 than with the 346? The math suggests there is less thrust to spare...
41 Seabosdca : It wasn't able to perform the same longhaul missions as trijets or 767 ER variants, but the A300 was a heavy twin launched in 1972 and in service in
42 PGNCS : I appreciate you pointing this out. I have tried (in vain) to explain the specifics of twin vs. 3 or 4 engine aircraft performance characteristics, a
43 Post contains images UAEflyer :
44 Zeke : True, but when comparing aircraft types within the same airline, fuel consumption is the major operating cost that is different between fleets. The o
45 LuisKMIA : There is also pressure to go "green", one of the reasons Richard Branson ordered the 787 for VS. Luis KMIA
46 F.pier : The program 340 had major hit when the previewed specific engine design was stopped. SO the choice CFM wasn't the top for this airplane.
47 Post contains links Teme82 : That was BA's 742 flying BA9 to Auckland and some ash from Mount Galunggung. http://en.wikipedia.org/wiki/British_Airways_Flight_9
48 Trex8 : the E does not have increased thrust, it has improved emissions and maintenance and avionics almost every modern fighter has an afterburning turbofan
49 Post contains links CitationJet : BN used to fly DAL to HNL using a 747-100 N601BN from an 8,800 runway. This was before DFW was built. I flew that flight many times when the flight w
50 Tdscanuck : Sorry Trex8, SEPilot is right. He's talking about *an* uncontained engine failure, not simultaneous engine failure. The probability of a simultaneous
51 Moo : If I remember my statistics lessons correctly, while doubling the number of engines would statistically increase failure chances, it doesn't double i
52 Trex8 : mea culpa, I see what you guys are saying. but 2x 0.000xxx is still pretty low!
53 Viscount724 : If not mistaken the Tu-144, the Russian counterpart of Concorde, used afterburning turbofans. Of the 65 non-turbofan standard 720s built, I believe o
54 A342 : Indeed, the early Tu-144S did. The improved Tu-144D switched to turbojets, IIRC.
55 PGNCS : Zeke, you misunderstand me. You are EXACTLY right, of course, and you have made my point for me! The fact that a twin will outclimb a quad on all eng
56 747fan : I've seen UPS 747-100's use about 8-9000ft. of runway on SDF-ANC flights (about 6 hours long due to headwind), so I'd imagine they used to use more w
57 SEPilot : Sorry, you remember incorrectly. The probability of an event happening to one of x independent entities is exactly the sum of the probability for eac
58 SpeedyGonzales : Moo is technically correct. The chance of a failure NOT happening with n engines is (1-y)^n, however when y and n are small enough, the chance of a f
59 Zeke : Correct, but the probability of having an engine failure in any aircraft is already so small. A pilot of a modern quad would in my view have the same
60 Post contains images SEPilot : Quite true. It is to me one of the most amazing feats of modern technology that jet engines are so incredibly reliable. Another excellent point.
61 N1120A : Labor costs are still a major part of what it takes to fly an aircraft. Not to mention labor costs, which are more easily spread with more seats. But
62 Post contains images Hiflyer : Well done series of posts...good info. In summary it appears that the first generation...the CFM motors...were just a bit less capable than the curren
63 Seabosdca : What Zeke wrote above is totally correct, so I wouldn't worry about engine problems regardless of aircraft... but if you want to feel better about be
64 Hiflyer : Went right up to a failure on a 330 and saw the damage....and since only two motors the hyds were blown as well as electrical and so on and so on. Ta
65 RedFlyer : Interesting (and glowing) information about the A340. So, in your opinion, why is it the model has been pretty much marginalized? I thought you said
66 Zeke : I dont think they are, its still pretty hard to get your hands on one, "marginalized" is what I would apply to similar generation aircraft like the M
67 SEPilot : Don't all twins have full electrical and hydraulic sources on each engine? As I mentioned before, the El AL 747 that crashed in Amsterdam (and the si
68 AirbusA6 : Over 200 A343s have been sold, which is fairly respectable when compared with it's direct rival the 772ER (which has sold 450ish) so it was hardly a f
69 LMML 14/32 : Not APU engines, of course, but they are just upgraded 320 engines. Regarding the terrible climbout, I flew an LH340-200 when it was first introduced
70 RedFlyer : It's hard to get your hands on a new-build airframe? Really?
71 Zeke : For ETOPS yes. I dont think it would not have happened on a 340 either, not the first case of a 747 dropping an engine, JAL done it in ANC as well, b
72 RedFlyer : Something tells me the next step in your line of argument will be to blur the lines between the A330 and A340 so that it appears the A340 had its bes
73 Zeke : I am not having an argument, if you are trying to pick one, pick someone else. I don't have time for your games. I have just answered your questions,
74 Seabosdca : Neither aircraft is really a "derivative" of the other, but the A340 was developed first and was expected to sell better. Airbus badly misestimated t
75 MarkC : It happened about 6 years ago. A300-600. Two unrelated, non simultanious internal engine failures shortly after takeoff. The plane did not crash as p
76 Thegeek : Wow!! Do you have a link?
77 Post contains images RedFlyer : Not sure what you're talking about regarding games. I originally asked you what in your opinion was the reason the A340 was marginalized when you cla
78 Post contains links MarkC : This mentions it. http://www.flyertalk.com/forum/showthread.php?t=290972
79 ERJ135 : A simple answer to your original question of "Whats wrong with A340 Engines", is Nothing at all! There are thousands of these engines in operation all
80 Zeke : You know the answer to that question already, performance alone is not used for determining what airframes to order. If performance alone was the onl
81 Post contains links PlaneInsomniac : According to both the Airliners.net history section and Wikipedia, the A330 and the A340 were literally launched and developed in parallel, with a la
82 RedFlyer : I do. As do most people.
83 AirbusA6 : The A343 is to the A333 what the 772ER is to the 772A models, therefore it's unfair to look at it by itself. Besides, if you compare current A343 sal
84 Tdscanuck : The rolling moment isn't a problem. The aircraft has to have enough roll authority to withstand a fuel tank puncture due to an engine failure at take
85 SEPilot : Several 737's have had an engine fall off; none of them have crashed. What caused the crash of the El Al plane was not the loss of the engines but th
86 PlaneInsomniac : I do not think this sentiment is limited to pilots. As a passenger, I also feel safer aboard a 4 engine aircraft than on a 2 engine aircraft. I would
87 SEPilot : In fact "regular" engine failures are also extremely rare, hence the acceptance of twin engine operations over long overwater routes. The thing is th
88 Thegeek : You're forgetting the El Al B747 in 1982 (#1862), and Concorde. The latter is arguable whether it would still have gone down if it were a twin. If th
89 Post contains links PlaneInsomniac : I do not contest that modern jet engines are very reliable, a fact that made ETOPS possible in the first place. Moreover, modern twins are obviously
90 Pihero : "Captain, engine #17 has some oil pressure fluctuation and the N1 vibration seems to be getting worse" "Number 17 ? On which side ?"
91 SEPilot : That was one of the 747's I was specifically referring to; I said so in an earlier post. My point exactly. On which planet? Whether or not you find i
92 Thegeek : You seem to be completely missing the point. Perhaps you just don't want to see it. UA232 was a CRASH which happenned on a runway. Just because the p
93 Post contains links Zeke : Engine mass has always been greater than the maximum fuel imbalance limitations I have seen. Not with swept wings, besides it is the pitch thrust cou
94 SEPilot : That could well be. Certainly all the ones I know of were quite a while ago, hence probably -200's. Light twins are supposed to be able to continue f
95 KensukeAida : Sorry, but that's BS. What brought UA 232 down and necessitated the differential thrust WAS the loss of all hydraulics. Not the uncontained engine fa
96 Post contains images Zeke : That is false. There is nothing in the FAR certification of light multi-engine aircraft which says they must fly (maintain altitude) while in the tak
97 SEPilot : Also zero 737NG's, 757's, 777's, MD-80's, MD-90's, 717's, A300's, A310's, A320's, & A330's. So what? An absolutely valid reason to go to a quad. [Edi
98 Post contains links Tdscanuck : This is true, but it's not particularly interesting. Due to they way airplanes are certified for enging-out conditions, an engine "failure" is an eco
99 SEPilot : Thanks for the support; I was beginning to think that I was a voice crying in the wilderness. This is one of many instances where a cold look at the
100 YULWinterSkies : This has a lot to do with the fact that the final P&W engine project for the A340 never came out. They were supposed to be a lot better than the CFM56
101 PlaneInsomniac : Well, except that none of you has actually provided any data. All that is being discussed here are the same few incidents involving both twins and qu
102 SEPilot : To the best of my knowledge there have been four crashes that stemmed from engine problems of any kind on tri's and quads and four on twins. Since wh
103 Pihero : By your logical reasoning, a single engine is less likely to have an uncontained failure than two and you may pursue this line in saying that a singl
104 RedFlyer : Although a very interesting perspective, it's not quite on the spot simply because on a theoretical single you then lose redundancy. And the key to s
105 Bond007 : Correct...and there are some of us that also believe that smaller single engine piston/turbines ARE safer than a comparably sized (and operated) twin
106 SEPilot : A very valid point. It is one thing to discuss the probabilities of events happening and quite another to live through them. I may firmly believe tha
107 Tdscanuck : -For the uncontained failures, it's a simple matter to look at the number of known events and normalize by flight hours on the type -Nobody has sugge
108 Pagophilus : A safety culture should look at worst-case scenario, not just probability. In a twin with one engine inop, should something go wrong with the other en
109 Bond007 : Unfortunately you somewhat contradict yourself there. A worse-case scenario is ALL four-engines on a quad failing ... not just two of 'em. Fortunatel
110 Pagophilus : The probability of which is far less likely than all engines on a twin. But is still not a glider!!! My car has 12 airbags, ABS and traction control.
111 PlaneInsomniac : Ok, then try to come up with such figures for the A330, A340, B767, B777, and B747, which is the current generation of widebodies. You can find the a
112 Post contains images Bond007 : But far more likely .... which was the discussion. .... and to be honest, it's arguable whether a quad losing 2 engines is much 'safer' than a 'glide
113 Thegeek : It is no doubt true that engine reliability is a greater factor than their number, but their number remains a factor. As for two engines out on a quad
114 PlaneInsomniac : [Please see discussion below][Edited 2008-01-07 15:02:31]
115 Bond007 : But neverthless, it doesn't take an engineering genius to point out that an uncontained engine failure on a quad is FAR more likely to affect another
116 Post contains images Bond007 : Uh ha .... not unheard of Still not sure where you get this number from? ummm.... no, you are twice as likely to have an engine failure on a quad tha
117 SEPilot : As I pointed out earlier, the same argument can be applied to light twins versus singles. The accident rates and insurance rates say otherwise. Your
118 PlaneInsomniac : Ok, I'll grant you I was wrong there. Of course that likelihood is greater in a quad. However, the impression created by the previous poster that a f
119 Tdscanuck : First of all, you can't calculate probabilities off of zeros because it's certainly not true that there is zero probability of an uncontained engine
120 Thegeek : Don't think I was making that comparison.
121 SEPilot : I totally agree with this. I believe that the probability of a quad losing two engines (assuming that the probability of failure of each engine is th
122 MarkC : Uncontained failures are more common than listed above. But, rarely do they result in a loss of life. But, hypothetically....if a turbine blade came o
123 KensukeAida : How do you know that? They're going by accident/incident reports. Not news stories. Correct. Worldwide, you can count the number of deaths on one han
124 Pagophilus : And the worst case scenario of all 4 engines inop is much less likely than all 2 inop on a twin. What I'm trying to argue here is that arguments from
125 Pihero : so,redundancy stops at a factor of two and then safety goes down if the factor is upped to three and four. Is that correct ? After all we are humans,
126 SEPilot : At least on my part they are based primarily on the fact that the same number of twins have crashed from engine related problems as planes with more
127 Zeke : My problem with ETOPS in such a situation (where bean counters dont have their backside strapped in the seat making decisions), is that ETOPS to some
128 SEPilot : I cannot type a superscript on this forum, so I used old computer notation to indicate "to the power of" by **. Perhaps that will make my math cleare
129 Bond007 : I understand, but earlier in the thread you suggested we should look at worse-case scenarios rather than statistics. I was just pointing out that the
130 RedFlyer : Again, you bring up a very interesting perspective! Let me ask you this: If more is better, would an airliner with 10 engines be even more desireable
131 Tdscanuck : Pretty much. When you're talking about things with very low and independent failure rates, the probability of dual failure becomes incredibly remote.
132 Post contains images Pihero : The several hundred are fine by me. And those instances where the crisis unit were assembled were about single engine diversions. Normality, indeed !
133 Post contains links Zeke : You must have access to NTSB information which has not been made public. http://www.ntsb.gov/ntsb/brief.asp?ev_id=20060809X01126&key=1 The public onl
134 Tdscanuck : No comment. That was a monstrous typo on my part...I meant "both engines would not have been taken out." Obviously, the engine that suffered the roto
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