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Statistically, when will a large twin engine jet end up in the drink?

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Statistically, when will a large twin engine jet end up in the drink?

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Old 3rd Jan 2019, 06:27
  #41 (permalink)  
 
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Dick, can you post a link to the expert reports you refer to? Until then, you are wasting my time.

You blindly assert that 4 engines are better than 2, without taking into account the fact that the more engines you have, the greater the likelihood of an uncontained engine failure, with the consequent risk of catastrophic damage to the controllability of the aircraft.

Maybe you are right and maybe you are wrong, but let’s have some evidence please!
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Old 3rd Jan 2019, 06:30
  #42 (permalink)  
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I make no such blind claim.
Look at the heading to this thread.

Why not answer the reasonable question?
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Old 3rd Jan 2019, 06:58
  #43 (permalink)  
 
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Originally Posted by Dexta View Post
I think the point of the original post is to build a logical argument along the lines of;

The Act states that safety is the primary concern.
CASA therefore creates and enforces regulation without consideration of economical factors.
Thus the regulations concerning GA, CSF, SIDS etc. do not take into account economic factors.
BUT
CASA allows ETOPS
Statistically four engines are better than two
CASA has allowed regulations that take into account economic viability FOR AIRLINES
This is against the ACT
SO
Either change the Act to reflect that economic factors should be considered when making and enforcing regulation for ALL LEVELS OF AVIATION.
OR
Stop lying about "Safety comes first".
Dexta,
That is Dick's whole point ---- CASA are very selective in their interpretation of S.9A of the Act.
When it suits them, CASA's interpretation of S.9A is that something called "safety" is THE ONLY CONSIDERATION.
This is the untruth that is peddled to the public, as most of us know, the reality is very different.
Otherwise, how can you have, say, an MEL, shouldn't everything be 100% serviceable?? Full stop!! For "safety".
Tootle pip!!
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Old 3rd Jan 2019, 07:03
  #44 (permalink)  
 
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Imagine...….(An 'oldie', but.....)

The 'early' days of 4 engine aircraft across the Atlantic, on a RPT basis, passenger gets an invite to flight deck, (like they used to then...), and after talking to pilot for a short time, asks....
"Capt., what do you think would the minimum number of engines for a risk free 'comfortable' flight across this vast ocean?"
Capt thinks for a while, then responds, "When the FO says to me, 'Capt, we have a problem - Number 16 is losing oil pressure...'
And I reply, "Oh!.. Which side..??"

As told to me troooly…….
Cheers
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Old 3rd Jan 2019, 07:25
  #45 (permalink)  
 
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Oh dear Dick,

Of course you are claiming that 4 are safer than 2. Go back and read your original post.

And the question you pose in the title of this thread demonstrates a misunderstanding of statistics.

If all you can do is make provocative statements without even trying to back them up with evidence then what is the point of even trying to engage in a discussion with you?
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Old 3rd Jan 2019, 07:38
  #46 (permalink)  
 
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Originally Posted by Bull at a Gate View Post
Oh dear Dick,

Of course you are claiming that 4 are safer than 2. Go back and read your original post.

And the question you pose in the title of this thread demonstrates a misunderstanding of statistics.

If all you can do is make provocative statements without even trying to back them up with evidence then what is the point of even trying to engage in a discussion with you?
Bull,
Go back and re-read ##42 and ##43, you are missing Dick's whole point.
Tootle pip!!
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Old 3rd Jan 2019, 08:31
  #47 (permalink)  
 
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Originally Posted by LeadSled View Post
Bull,
Go back and re-read ##42 and ##43, you are missing Dick's whole point.
Tootle pip!!
No, you're missing the point. Dick is implying that, by allowing twin engine ETOPS, they are making air travel less safe. The statistical data simply doesn't back that up.
Originally Posted by Dick Smith View Post
TDracer. I have not made any claim based on gut feeling.

I take advice from experts. And I use commonsense to decide which advice is correct when there are differences.

I can can see why you post anonymously!
I see, you can't back up your posts with data, so you resort to insults. Nice....
If you'd bothered to talk to actual certification experts, you'd know that 'safe' is clearly defined in the certification regulations - in short is says if the probability of a catastrophic outcome is less than one in a billion flight hours (i.e. 10-9/hr), it's safe. ETOPS regulations are based on that requirement. Every critical system on the aircraft is certified based on that one in a billion requirement.
Any aviation expert worth their salt would know that. Somehow your experts don't. I guess that's why your experts are anonymous.
You repeatedly imply that ETOPS is somehow less safe, but never actually say it in so many words, then proclaim "I have not made any claim" . You clearly have an agenda - you're not fooling anyone.
You could just as well start a thread that asks 'when will a quad end up in the drink?'. It's clearly an unanswerable rhetorical question. Funny thing about random events, no one seems to know when they will happen.
BTW, as far as my handle and posting anonymously, anyone who really cared could figure out who I am in about five minutes - people who know me immediately recognize it as my nickname. Heck it's on my license plate.
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Old 3rd Jan 2019, 08:38
  #48 (permalink)  
 
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Originally Posted by Dick Smith View Post
I make no such blind claim.
Look at the heading to this thread.

Why not answer the reasonable question?
The question is meaningless. Statistical mathematics can’t answer “when?” It can only give probabilities and the probabilities don’t change based on whether something has or hasn’t occurred. The chance of a coin toss coming up heads is 50%, however if you happen to toss 100 tails in a row your chances of the next toss being heads is still 50%. It hasn’t become “due”, there is no “time when heads is going to appear”. Likewise there is no time when “a twin is going to end up in the drink?”

Stop being emotive, provocative, etc. Talk plainly, state what you mean, don’t ask meaningless questions. Debate with integrity. Once you start doing that, a lot more people will give you the time of day here. And for gods sake let go of this fixation you have with anonymity on this website. Some of us like to have some sort of privacy and it has absolutely nothing to do with the value of our opinions.
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Old 3rd Jan 2019, 08:49
  #49 (permalink)  
 
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The smarter part of my brain suggests that regardless of probabilities, each event is mutually exclusive and two failures could absolutely occur on the one flight and that could be just after takeoff, over water or anywhere for that matter.

If you had told me that five 0’s were going to come up one night at Crown Casino on Roulette, I’d never have believed you, but it did happen.

I feel as though the Swiss cheese effect is more likely to cause the twin failure (at different times on the one flight), rather than 2 x compressor blade / actual physical engine failures for example.
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Old 3rd Jan 2019, 09:14
  #50 (permalink)  
 
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Yep, actual experts please Dick. And that doesn't mean you or GT or BB or other usual suspects.
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Old 3rd Jan 2019, 10:45
  #51 (permalink)  
 
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Originally Posted by tdracer View Post
BTW, as far as my handle and posting anonymously, anyone who really cared could figure out who I am in about five minutes - people who know me immediately recognize it as my nickname. Heck it's on my license plate.
We all know who and what you are... a showboat, who likes the sound of his own engine (or motor as you put it) !

You’re quoting some very small probability figures, but do they include engine shrowds and that type of thing blowing off and damaging the engine causing shutdowns, or by failure, do you mean actual internal turbine failure for example, and does engine failure include hoses blowing off necessitating manual shutdown by the pilots?



Since I retired about 18 months ago, I've been looking to 'reward myself' and buy some sort of 'super car'. As may be guessed from my handle, I'm a big car guy, and I'm especially into the engines - partly an outgrowth of my 40 years as a propulsion engineer at Boeing. Previous examples of my interest in unusual automotive engines have included the original Buick Grand Nation 3.8 liter turbo, four different RX-7 rotaries, and my current 2 liter, 240 HP/8,900 rpm Honda S2000 (some of the racing engines I drove were similarly exotic - including one that I routinely revved to 16k - it sounded wonderful ).
Starting shortly before I retired, I lusted for a Ford GT350 Shelby Mustang and it's 5.2 liter, 526 hp, 8k, flat plane 'Voodoo' naturally aspirated V8. Unfortunately I wasn't the only one, and new GT350 Mustangs were selling for ~$15k over the ~$60 list price - something I was unwilling to pay. Then, about six months ago, while getting my Ford van serviced, I walked into the Ford showroom and discovered they had two GT350 Mustangs in-stock, and were only asking for MSRP. WhooHooo! I took one for a test drive - the motor was as fantastic as I expected and it sounded glorious - but the wife objected. She didn't want me to get rid of the S2000 (she really likes that it's a convertible) - and I couldn't justify having both the Shelby Mustang and the S2000.
So, I'd been looking at various other 'super cars' - Austin Martin, Acura NSX, McLaren, etc., but to get into something I really wanted the price kept escalating yet it would still only be like my S2000 - a nice weather car that I'd be able to drive maybe 4 months per year.
Then BMW introduced a new M5. My current daily driver is a 2007 BMW 328xi (AWD) - I love it, and the AWD means I can drive it year round regardless of the weather, the only real down side is it's on the small side for long road trips (the wife doesn't exactly travel light, and we often take our two dogs along). The new M5 is AWD, significantly more room than my 328, very good handling and a twin turbo V8 producing 600 hp and sub 3 second zero to 60 gives it legitimate 'super car' creds, and if I buy an extra set of wheels fitted with proper snow tires it's a legitimate all weather, daily driver car. I've already arranged to sell the 328xi to an in-law, I keep the S2000 so my wife is happy, and I can give that snooty Tesla 'ludicrous mode' driver a scare My biggest complaint is the motor sound is muted by the turbo (yea, I'm seriously into that sound aspect)
The only problem is it'll be ~six months before my M5 arrives...
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Old 3rd Jan 2019, 11:04
  #52 (permalink)  
 
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Here is a genuine question: in the last 10 years how many twin engine aircraft have crashed in circumstances where they would not have crashed had they had 4 engines? I can think of a couple of examples involving shutting down the wrong engine but Dick’s beef seems to be more related to mechanical unreliability. So, how many in that category?​​​​

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Old 3rd Jan 2019, 11:09
  #53 (permalink)  
 
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Originally Posted by Squawk7700 View Post
We all know who and what you are... a showboat, who likes the sound of his own engine (or motor as you put it) !
Don't know who he is, but I am an aeronautical engineer (Chartered Engineer) who has (at various times) focused on both airworthiness certification and supportability engineering - a field that includes reliability and maintainability engineering (as it happens I have a masters degree in supportability engineering). I have been involved in the process of certifying aeroplanes many times, including undertaking the fault-tree anaylsis that determines the probability of single and multiple events leading to undesirable end-effects like death, serious injury and significant damage (this is a large chunk of the statistical process people have mentioned above). Each case is different, but these days it is a very common finding that (once you strip out the common-mode causes like fuel feed failure/leaks/contamination, maintenance-induced failures etc) the probability of a double-engine failure is much, MUCH lower than the probability of other events which would bring down a particular aeroplane. This is because modern engines have become so reliable and because they are much better instrumented with prognostic health monitoring systems so that a potyential failure is mitigated before it causes a disaster. And yes, I have seen cases where adding additional engines INCREASES the probability of aircraft loss due to risks like engine fractricide and uncontained fire/burst etc.

As a result in most cases it is simply more rational to spend effort/money on eliminating failure causes that are more probable than it is burdening aircraft with physical and financial features relating to much less likely events.

Sorry to contradict you on this Dick, because it's something you clearly have strong and passionate views on. But I am labouring under the distinct disadvantage of actually knowing what I'm talking about.

PDR

Last edited by PDR1; 3rd Jan 2019 at 11:11. Reason: Added quote context to make it clear which post I was responding to
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Old 3rd Jan 2019, 11:58
  #54 (permalink)  
 
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PDR1, With all due respect, you dont understand. You are dealing with the tin-foil hat brigade. Your professional qualifications are merely the source of suspicion and contempt. Much more comforting for the lumpen internet dross to be reassured that their grievances are real and evidence to the contrary is proof of a conspiracy.
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Old 3rd Jan 2019, 12:02
  #55 (permalink)  
 
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Originally Posted by tdracer View Post
No, you're missing the point. Dick is implying that, by allowing twin engine ETOPS, they are making air travel less safe. The statistical data simply doesn't back that up.
.
tdracer,
You should re-read Dick's very first post, that started this thread.
And I have no idea who you are.
Tootle pip!!
PS: I do know something about the subject, having been closely involved in the introductions of EROPS in Australia --- including much discussion on the statistical issues, and the reasons for the engineering mods. that made an ordinary B767 an ER. And the problems we experienced.
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Old 3rd Jan 2019, 12:03
  #56 (permalink)  
 
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Don't know who he is
All I know is he worked at Boeing, designed or fitting engines to their contraptions, and is now earning a well deserved retirement. His posts are often well informed and full of technical engineering porn.

The leading edge in manufacturing (and often it's the aviation industry) are constantly breaking new barriers, which includes operating huge CNC milling machines, 3D printing, growing structures in crystallite form, new composite materials, bonding techniques, computer assisted modelling... the list goes on - it's now a young man's game (under expert guidance of course).
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Old 3rd Jan 2019, 12:40
  #57 (permalink)  
 
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In the late 1980's I attended a Boeing conference where a briefing on the planned B777 was given. At the time I was not too concerned about the A310 and the A300 as they were regarded as regional operation aircraft. (The early Emirates services to MEL were operated by the A310 to/from SIN) Likewise the B757 and B767 whilst longer range were not capable of trans pacific operations (The B767-200ER was capable).

During the B777 presentation it was obvious Boeing were proceeding at break neck speed to introduce the go anywhere B777. Most pilots at the presentation where aghast at the prospect of a B777 being approved for say LAX-AKL and LAX-SYD. I was concerned about the prospect of up to 200 minutes nail biting on a single engine and the resultant engine bearing damage. (When a heavy twin suffers a shutdown both engines are usually replaced)

I suggested the B777 could have a CFM56 engine in the tail and be regarded as a tri-jet. The CFM56 would be used for take-off and shutdown at the top of climb. The engine could be shuttered for aerodynamic purposes when not required. In the event of a shutdown or worse the CFM would be fired up and provide centre line thrust and possibly electrical power and pressurisation. My suggestion was shot down by the Boeing attendees as being too expensive and adding weight to the aircraft.
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Old 3rd Jan 2019, 13:44
  #58 (permalink)  
 
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Originally Posted by B772 View Post
In the late 1980's...

...I was concerned about the prospect of up to 200 minutes nail biting on a single engine and the resultant engine bearing damage. (When a heavy twin suffers a shutdown both engines are usually replaced)

I suggested the B777 could have a CFM56 engine in the tail and be regarded as a tri-jet.... My suggestion was shot down by the Boeing attendees as being too expensive and adding weight to the aircraft.
What is this bearing damage of which you speak? In a turbojet engine? Its called Maximum Continuous Thrust for a reason, and the rotating elements of the bearing are subjected to slightly higher velocities but still within their design envelope.

Regarding your aux engine idea: I have heard at the bar: “The only reason I prefer four engines is that there are no five-engined planes” . I guess time has shown that our earlier luddite outrage was misplaced.

Thinking back to the original loooong range aircraft, they went from ten engines (B-36) to eight (B-52). All of that was dictated by take-off performance. Their mission hasn’t changed, yet the new bombers are twins.

Engines share more than just fuel. They share air, containing freezing precip, ice crystals, hail, ash, birds, non-TCAS traffic. They also share oil and maintenance. They share manufacturer, including flaws, bad metallurgy, bad design. They also share a common parts stream which may be open to counterfeits. They also share operators, including people who forget anti-icing, screw up the fuel scheduling, etc. All of the foregoing is true regardless of the number of powerplants.

Oh yeah....engines also share the duties of carrying around people with evil intent, pallets of lithium batteries and flights planned through war zones. The entire enterprise is based on odds which I reckon are about 9 to 5 against.








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Old 3rd Jan 2019, 13:45
  #59 (permalink)  
 
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Of course the B777 has now been in service for 24 years, with most of that time having a large number of aircraft flying at very high utilisation rates, racking up the flying hours. In that time I count 3 ground fires due to engine failures, one ground fire on refuelling, 2 major electrical faults (one on the ground, 1 in the air), one crash due to iced fuel filters, one lost to a missile, one in-flight crew death and two lost due to crew actions (if you include MH370, which I tend to). There isn't a single one of these where adding a third (let alone a fourth) engine would have changed the outcome, but if the weight/cost/effort were deemed necessary sacrifices there could have been significant benefit from more extensive fire detection/surpression capabilities. There might also be tangible benefit in beefing up the zonal inspections to spot electrical chafing. But on the reliability performance from its first quarter-century there would be more justification in adding a third (or fourth) pilot than extra engines, so those who shot you down were almost certainly justified in doing so.

But you are also talking about stanby redundancy rather than active redundancy - this is a whole different skillet of sardines. A 3/4 engined aeroplane has "active" redundancy in that all the engines are rrunning but the system can still perform if one or more stop. But "standby" redundancy involves carrying a spare engine that would only be foired up in an emergency, which means you have toi consider the probability that this engine will work WHEN YOU NEED IT, rather than whether a working engine will fail shortly after a fraternal failure. The probability sums here are very different. If you do the maths you usually find that a standby system has to be at least eight times more reliable than the active system to provide any significant reduction in hazard rate. This becomes even more extreme with complex heat machines like gas turbines because they characteristically tend to fail the most on start-up (probability of failure of a gas turbine on start up is five times greater than probability of failure during periods of cruise power). So you were probably shot down because the engineers present could show that your proposition made overall reliability worse rather than better, even if just due to the increased parts count.

PDR
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Old 3rd Jan 2019, 21:16
  #60 (permalink)  
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It’s clear that the prime reason for the move from 4 engined to two engined is not to improve safety but to improve participation levels and airline profits- and it has clearly worked.

Thanks for all the written evidence I require to show that.

CASA is clearly not complying with “the lie” in the act!

One day the act act will be changed to reflect the truth.
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