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  # 2357015 18-Nov-2019 22:12
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Is all this engine business more or an issue now because we have these big long haul planes, but only twin engine.   Where with 747s etc the had 4, which gives a bit more leeway for dropping an engine. 





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  # 2357027 18-Nov-2019 22:45
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davidcole:

Is all this engine business more or an issue now because we have these big long haul planes, but only twin engine.   Where with 747s etc the had 4, which gives a bit more leeway for dropping an engine. 



I think it's more like
Lighter, higher combustion chamber pressures, more reliable - pick two.




Involuntary autocorrect in operation on mobile device. Apologies in advance.


 
 
 
 


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  # 2357029 18-Nov-2019 23:15
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DjShadow:

 

How hard would it be to modify a 787 to run GE engines instead of Rolls Royce?

 

 

 

 

The recent order of 787-10's (larger but slightly shorter range) that AirNZ just confirmed (as opposed to the 787-9's currently in the fleet) have been ordered with the GE engines so they are covering their bases as such.

 

https://www.airnewzealand.co.nz/press-release-2019-airnz-announces-multi-billion-dollar-investment-in-new-fuel-efficient-boeing-787-10-dreamliners

 

Of course GE engines are not perfect either, they are responsible for significant delays in the launch of the 777-X -

 

https://www.flightglobal.com/news/articles/analysis-ge-wraps-up-ge9x-trials-as-777x-flight-tes-462145/

 

The bottom line is the current engine technology has pretty much been pushed to the limits of available materials and technologies so its pretty hard to make them work with the reliability and longevity predicted. The next generation (adaptive) will be about 5 years to get to fighter use, and then likely another 10 years to make it to civil use.

 

https://www.flightglobal.com/news/articles/usaf-starts-work-on-defining-adaptive-engine-for-fut-450053/

 

 

 

Airframers (Boeing/Airbus) have largely relied on demanding more for less out of the engines for the last two generations of aircraft (787/A350 excepted), and that day is largely done until adaptive engines become viable.

 

 

 

 


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  # 2357149 19-Nov-2019 10:53
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Batman:
davidcole:

 

Is all this engine business more or an issue now because we have these big long haul planes, but only twin engine.   Where with 747s etc the had 4, which gives a bit more leeway for dropping an engine. 

 



I think it's more like
Lighter, higher combustion chamber pressures, more reliable - pick two.

 

How about in practice, pick all?

 

FWIW, safety measured in terms of deaths per trillion revenue paying kilometers travelled, is about 2000% (20 times) better now (when most longhaul aircraft are twin engine) than in 1980, when longhaul flights were in 3/4 engine planes.

 

IIRC the maximum short term (takeoff) thrust rating of each of twin engines has to exceed what's required per engine in 3/4 engine planes, so in normal operation there's more in reserve. (IOW they're running at lower % of maximum - less stressed) There's also an offsetting factor, all other things being equal you're twice as likely to have uncontained engine failure with 4 engines.

 

If there had been real safety concerns because of crashes, people would boycott the planes. 

 

It'll be interesting to see how "flyer reluctance" impacts on 737 max operators - if and when they ever get them back in the air.  IIRC people on this forum have said they'll never fly on one.


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  # 2357159 19-Nov-2019 11:07
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Meanwhile, Musk's going to be taking to people to Mars and back with one main engine, and if that engine so much as farts for a couple of seconds at a critical time, you're either going to crash on a planet or miss your destination completely, spending the last of your days lost in space waiting to run out of food/air/water.


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  # 2357163 19-Nov-2019 11:12
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Fred99:

 

Meanwhile, Musk's going to be taking to people to Mars and back with one main engine, and if that engine so much as farts for a couple of seconds at a critical time, you're either going to crash on a planet or miss your destination completely, spending the last of your days lost in space waiting to run out of food/air/water.

 

 

 

 

Anyone going to Mars who it relying on making the return trip is fooling themselves, and lets be real, its unlikely to happen in our lifetimes anyway.


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  # 2357211 19-Nov-2019 12:23
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noroad:

 

Fred99:

 

Meanwhile, Musk's going to be taking to people to Mars and back with one main engine, and if that engine so much as farts for a couple of seconds at a critical time, you're either going to crash on a planet or miss your destination completely, spending the last of your days lost in space waiting to run out of food/air/water.

 

 

 

 

Anyone going to Mars who it relying on making the return trip is fooling themselves, and lets be real, its unlikely to happen in our lifetimes anyway.

 

 

 

 

Getting to mars is easy....it's stopping and landing that's difficult.  Bloody humans and their bag of meat bodies.





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  # 2357290 19-Nov-2019 15:03
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davidcole:

 

noroad:

 

Fred99:

 

Meanwhile, Musk's going to be taking to people to Mars and back with one main engine, and if that engine so much as farts for a couple of seconds at a critical time, you're either going to crash on a planet or miss your destination completely, spending the last of your days lost in space waiting to run out of food/air/water.

 

 

 

 

Anyone going to Mars who it relying on making the return trip is fooling themselves, and lets be real, its unlikely to happen in our lifetimes anyway.

 

 

 

 

Getting to mars is easy....it's stopping and landing that's difficult.  Bloody humans and their bag of meat bodies.

 

 

 

 

I expect it would have to land in a similar way too the lunar landers. Although it would probably need to be a combination with a parachute to initially slow it down enough. I don't think it is a huge issue. But i think anyone initially going, it is likely to be a one way trip, as so many things can go wrong. 


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  # 2357299 19-Nov-2019 15:19
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davidcole:

 

Is all this engine business more or an issue now because we have these big long haul planes, but only twin engine.   Where with 747s etc the had 4, which gives a bit more leeway for dropping an engine. 

 

 

 

 

I personally would feel a lot safer on a 4 engined plane, especially now. If one engine goes on a twin engined plane, then you have no redundancy if the other one goes.  


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  # 2357303 19-Nov-2019 15:31
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Fred99:

Meanwhile, Musk's going to be taking to people to Mars and back with one main engine, and if that engine so much as farts for a couple of seconds at a critical time, you're either going to crash on a planet or miss your destination completely, spending the last of your days lost in space waiting to run out of food/air/water.


Starship/Superheavy will (at this stage) have 41 engines.
35 for the superheavy launch rocket and 6 for the Starship spacecraft.

Musk is smart/nuts, and he seems to be able to achieve nearly anything he sets his mind to.




Location: Dunedin

 


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  # 2357313 19-Nov-2019 15:48
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Fred99:

 

...IIRC the maximum short term (takeoff) thrust rating of each of twin engines has to exceed what's required per engine in 3/4 engine planes, so in normal operation there's more in reserve. (IOW they're running at lower % of maximum - less stressed) There's also an offsetting factor, all other things being equal you're twice as likely to have uncontained engine failure with 4 engines.....

 

That was kind of the problem first time round with the RR's - they are fine when under-stressed in cruise but they wouldn't last long enough on one engine at wide open throttle.

 

I'm not so sure I agree with where your unconstrained engine theory is heading. There is no question that 4 engines is better for your survival than 2. ETOPS 240 is a very good reating for a twin jet (ETOPS 180 is more common) and is hard work for an airline to maintain, but the standard B474-8 is rated at ETOPS 330 straight out of the factory, so the regulators are far more confident the 747's ability to get you there after an engine failure (or 2 😃) than a twin jet. 


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  # 2357316 19-Nov-2019 15:55
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Paywalled on Herald

 

But looks like they might get another wet-lease back on to fill some of the gaps back up again.

 

Punters won't appreciate HiFly if they are back again. Fiji have LionAir at present. Cancelled their US based Miami crews after 2? accidents


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  # 2357339 19-Nov-2019 16:18
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I personally would feel a lot safer on a 4 engined plane, especially now. If one engine goes on a twin engined plane, then you have no redundancy if the other one goes.  

 

 

 

 

As someone who spent a lot of time fixing planes I completely agree. The on P3 Orion we would shut down one of the three engines as a matter of course during patrols to save fuel, sometimes even just flying on two to really extend time on station. Sure is nice to have more than one left working over the deep Pacific if something goes wrong. Unfortunately two large engines are just way more efficient than three or four, they just have to be really reliable.  https://en.wikipedia.org/wiki/ETOPS

 

 


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  # 2357352 19-Nov-2019 16:57
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noroad:
Anyone going to Mars who it relying on making the return trip is fooling themselves, and lets be real, its unlikely to happen in our lifetimes anyway.

 

mattwnz:
... But i think anyone initially going, it is likely to be a one way trip, as so many things can go wrong.

 

 

 

I thought that part of the 'deal' was that the initial trips will be one way.
This is in the same sense that the first Irish, Scottish and English settlers to Australia - mostly not volunteers, admittedly - were on a one-way trip. It wasn't a kamikaze-style suicide trip or a death sentence, but the cost and likelihood of ever going 'home' are such a high barrier that most of the people going out never expected to go back, and indeed very few did.


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  # 2357356 19-Nov-2019 17:06
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PolicyGuy:

 

noroad:
Anyone going to Mars who it relying on making the return trip is fooling themselves, and lets be real, its unlikely to happen in our lifetimes anyway.

 

mattwnz:
... But i think anyone initially going, it is likely to be a one way trip, as so many things can go wrong.

 

 

 

I thought that part of the 'deal' was that the initial trips will be one way.
This is in the same sense that the first Irish, Scottish and English settlers to Australia - mostly not volunteers, admittedly - were on a one-way trip. It wasn't a kamikaze-style suicide trip or a death sentence, but the cost and likelihood of ever going 'home' are such a high barrier that most of the people going out never expected to go back, and indeed very few did.

 

 

 

 

I think people who initially went to the moon probably expected that they may not return either. That is also using 50 year old technology and a lack of knowledge of space, where things should have improved significantly. 


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