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DIJKKIJK
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Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 8:28 am

Can the ever progressing technological improvements eventually result in a single engined, widebodied, long range aircraft?

Such an airplane can also be very economical.

Or is there a compelling reason to have more than one engine? Two at the very least?

I can also propose a design. As single engine on the tail - maybe something like a DC-10/L-1011 with no engines on the wing  

What do you think?
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Starlionblue
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 8:39 am

Unless you can make engines much more reliable than today, and I mean much much more reliable than what is already one of the most reliable systems on the planet, you need two for redundancy. You'd need to be sure the engine never fails, which means making it completely fail safe with regards to all failure modes. The problem is that shedding a fan blade is not something a gas turbine can easily recover from.

Every system on the plane needs to either completely reliably not fail (e.g. the wing spars), allow continued operation without (e.g. belly landing in case of landing gear not coming down) or have a backup that allows continued operation (e.g. engines).

Now, if someone invents some other propulsion method that is not a gas turbine, and can be proven to be completely reliable, that is have fail safes for all imaginable failure modes, the story changes.


But all right. Let's assume you have a fabulously reliable gas turbine. By having a single engine, you run into all the issues with tri-jets, but worse. Engine on the tail is a recipe for spectacular CoG issues, as well as putting all that spinning metal right next to very critical control surfaces. The Sioux City accident showed the issues with tail mounted engines far too well.
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Woodreau
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 9:19 am

Quoting DIJKKIJK (Thread starter):
Or is there a compelling reason to have more than one engine? Two at the very least?

At least in the United States, airlines are prohibited from operating single engined aircraft, per 14 CFR 121.159.

http://www.ecfr.gov/cgi-bin/text-idx...03d94&node=14:3.0.1.1.7.8&rgn=div6
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 10:29 am

Yeah, and it would NEVER get certified.
But, especially with the grand GE-90-115, it's theoretically feasible. You could run a light 767 on one of them.
My own theory involves two engines, but one of them stowed, and only used in the event of the primary engine failure.
Of course, there are obvious large drawbacks and hurdles in that design, too.
 
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 10:40 am

I just can´t imagine this possibility with technology availlable today.

How would you define ESOPS ???
(maybe passengers are forced to stick out paddles out of the fuselage like in a boat and start rowing if that single engine stops working ?)

Starlionblue just made it clear - it´s not possible (at least not unless a dramatic leap forward in technology is achieved)
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 10:54 am

Quoting Woodreau (Reply 2):
At least in the United States, airlines are prohibited from operating single engined aircraft, per 14 CFR 121.159.

Isn't Pilatus working to get their PC-12 approved for regional ops? Not sure of the exact reg that applies here..
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Starlionblue
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 11:49 am

Quoting sturmovik (Reply 5):
Quoting Woodreau (Reply 2):
At least in the United States, airlines are prohibited from operating single engined aircraft, per 14 CFR 121.159.

Isn't Pilatus working to get their PC-12 approved for regional ops? Not sure of the exact reg that applies here..

IMHO we are going to see more small single-engined aircraft in commercial service. However a PC-12 can divert to even very small runways, and in a pinch a landing in a cornfield is at least something you could contemplate without assuming almost certain death for the occupants. The same is not true for a widebody. Also no long stretches far from diversions like, say, many 777s.
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tb727
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 1:27 pm

Quoting sturmovik (Reply 5):
Isn't Pilatus working to get their PC-12 approved for regional ops? Not sure of the exact reg that applies here..

Caravans and PC12's are operated under 135 rules.
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rfields5421
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 1:29 pm

Quoting sturmovik (Reply 5):
Isn't Pilatus working to get their PC-12 approved for regional ops?

Part 121 is certification for commercial operators. The PC-12 and other single engine props are certified as commuter aircraft under a different section.

However I'm not aware of any single engine jets certified for non-crew seat passengers.

One company did design and build a single engine business jet in the late 60s / 70s. It used to be on display in a museum in Oklahoma City. However, it could not meet the certification performance standards and the design was abandoned.

A single engine wide-body jet type aircraft is going to be at a huge economic disadvantage. A single engine design requires mounting the engine on the centerline. That is going to impact the aerodynamics of the aircraft in a negative manner. The fuselage is going to have to give up passenger and cargo space for the engine mounting. It is going to transmit the engine sound and vibrations to the passengers in a much higher rate/ frequency than current designs. It is going to be noisy and hotter.

Two engines slung under the wings is simply the very best combination of requirements to be most aerodynamic and fuel efficient. A single engine design is going to require so much 'over capacity' to meet go around and emergency requirements that the single engine design would not be more fuel efficient than the current two engine designs.

[Edited 2014-06-09 06:33:14]
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 3:05 pm

Quoting rfields5421 (Reply 8):
A single engine design requires mounting the engine on the centerline. That is going to impact the aerodynamics of the aircraft in a negative manner. The fuselage is going to have to give up passenger and cargo space for the engine mounting. It is going to transmit the engine sound and vibrations to the passengers in a much higher rate/ frequency than current designs. It is going to be noisy and hotter.

Just swap the engines for twin fuselages:
http://www.cardatabase.net/modifieda...earch/photo_search.php?id=00005390

Quoting rfields5421 (Reply 8):
Two engines slung under the wings is simply the very best combination of requirements to be most aerodynamic and fuel efficient.

   It kind of mirrors evolution.
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 5:14 pm

Quoting DIJKKIJK (Thread starter):

Or is there a compelling reason to have more than one engine? Two at the very least?

If you can design and demonstrate an engine that will never ever fail for any reason whatsoever with 100.0% certainty, then I suppose so.

Good luck on that.  
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 5:32 pm

Quoting AA737-823 (Reply 3):
My own theory involves two engines, but one of them stowed, and only used in the event of the primary engine failure.
Of course, there are obvious large drawbacks and hurdles in that design, too.

I have thought about this too. I was thinking two engines where the primary one is used for normal take off and cruise. The secondary is a APU + Primary in low power regimes like taxi etc. + the backup for engine out scenarios. It has a lower thrust and switched to idle in cruise. To address the asymmetric thrust issue, the design will mount the engine under the fuselage, something like the F-16.

Of course there are probably multiple hurdles like FOD susceptibility being the most obvious.

[Edited 2014-06-09 10:35:06]
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 5:57 pm

Quoting rfields5421 (Reply 8):
Part 121 is certification for commercial operators.

Part 121 is for scheduled air carrier service. Commercial operators operate under all kinds of regulations, 121, 125, 135, 137, 91K.

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airmagnac
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 9:40 pm

Depends what you're talking about with the word "engine".
Airplane engines have always been self-contained units fulfilling 2 functions : the generation function (convert stored chemical energy (fuel) into "useful" energy) and the propulsion function (converting the useful energy into kinetic energy, or forward movement of the vehicle).
If you look at a car, the two functions are fulfilled by seperate components : the engine under the hood generates energy from the fuel, which is then transmitted to the wheels which push the car forward. If the car is jacked up and no wheel touches the ground, the car won't go anywhere, no mater how hard you push the gas pedal. And without an engine, nothing will happen either, even if the car has 4 perfect wheels and a full tank of gas.

Until now, all engines have been combustion engines producing mechanical energy (a spinning shaft, usually). Carrying several tens of thousands of mechanical horsepower over any significant distance is difficult to say the least. This implies that the generation must be located as close as possible to the propulsion. Another issue is that it is difficult to modulate and divide it onto several different paths. Thus we have integrated units, with generation & propulsion functions packaged together.

But the common root problem tothe aforemention difficulties lies with the transmission

If we could generate a different "useful" energy, which could be transmitted and controlled relatively easily (say, electrically), then the 2 functions could be seperated.
We could then consider a "single generation/multiple propulsion" architecture. This could be a single big generation unit located somewhere in the aircraft (most likely the tail cone, if we keep the tube-with-wings layout), driving a pair number of fans (to preserve symmetry).
The generator will have to be very "reliable", but that notion depends on the architecture. With current engines, failure often means total loss of thrust. If the "single generator" is a bank of batteries coordinated by power electronics, a failure may only mean a partial loss of thrust. Then again, we could argue about whether or not this is indeed a "single" generato, even if it is packaged as one block of equipment ! A single gas turbine + alternator setup,on the other hand, would have to be extremely reliable (at most 1 failure in 1 billion hours)
Another issue is preventing potential heat, vibrations, noise, and possibly smoke & fire from reaching the cabin. Current planes do have an engine in the tail (APU), but that is a relatively tiny engine compared to what we're talking about (I'd say the output power would be 2 orders of magnitude greater). Aft CG could be an issue too...so maybe a tube with wings would not be adequate after all.

There was a recent article during ILA about work being carried out by the Aibus Group in this general direction, even if it's not exactly a "single generator" concept :
http://www.flightglobal.com/news/art...or-radical-propulsion-leap-399536/

And of course, it's for a small regional aircraft, not a wide-body.


As for "single propulsion", it would be made easier if the generation part(s) can be installed seperately from the propulsion part through the use of another type of transmission. But unless we find a non-air-dependent mean to propulse the aircraft, we will be constrained by aerodynamic integration. Meaning lateral symmetry is better, and a fan installed "around" the fuselage or on some kind of a pole sticking out far behind the tail. Not aerodynamically favorable, I would guess. And there is still the issue that it is a single point of failure.
I just read another article in Flight International last week about a "fuselage fan" concept being looked at in Germany :
http://pro.flightglobal.com/news/art...t-novel-propulsion-concept-399532/
But the aim here is to relieve the main engines, not replace them.

Anyway, there are still many issues with electrical transmission to be solved : power electronics still have margin for improvement, and waste heat management is a major pain in the a$$.



I guess I went all-in with geeky techno-babble, so to summarize :
There is no chance we will see single engine ops with current engine architectures.
It may be possible with new tech to see "single generator" or "single propulsor" architectuers, in particular with electrical transmission which would enable to "split" these parts. But reliability could be an issue, and the performances may not be interesting compared to what we have today. In any case, don't count on seeing an operational machine anytime soon.
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 10:19 pm

Quoting airmagnac (Reply 13):
As for "single propulsion", it would be made easier if the generation part(s) can be installed seperately from the propulsion part through the use of another type of transmission. But unless we find a non-air-dependent mean to propulse the aircraft, we will be constrained by aerodynamic integration. Meaning lateral symmetry is better, and a fan installed "around" the fuselage or on some kind of a pole sticking out far behind the tail. Not aerodynamically favorable, I would guess. And there is still the issue that it is a single point of failure.

Are you by any chance referring to the Lear Fan design with the two turbines feeding a single prop? I doubt the FAA would go for such a configuration.
http://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Two_Learfans_at_Reno_1982_%286579626527%29.jpg/1024px-Two_Learfans_at_Reno_1982_%286579626527%29.jpg

[Edited 2014-06-09 15:20:26]
 
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Starlionblue
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RE: Single Engine Widebodied Aircraft - Possible?

Mon Jun 09, 2014 11:54 pm

Quoting golfradio (Reply 11):

Quoting AA737-823 (Reply 3):
My own theory involves two engines, but one of them stowed, and only used in the event of the primary engine failure.
Of course, there are obvious large drawbacks and hurdles in that design, too.

I have thought about this too. I was thinking two engines where the primary one is used for normal take off and cruise. The secondary is a APU + Primary in low power regimes like taxi etc. + the backup for engine out scenarios. It has a lower thrust and switched to idle in cruise. To address the asymmetric thrust issue, the design will mount the engine under the fuselage, something like the F-16.

It's a neat idea, but you'd be carrying around all that weight without using it. If it is retractable, it takes up a huge amount of space and the retraction mechanism is heavy and complex. If it is "always out" it creates a lot of drag.

Besides, I don't think you'd really be saving fuel.
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RE: Single Engine Widebodied Aircraft - Possible?

Tue Jun 10, 2014 3:03 am

Quoting Starlionblue (Reply 15):
Quoting AA737-823 (Reply 3):
My own theory involves two engines, but one of them stowed, and only used in the event of the primary engine failure.

The most critical time for an engine failure is at take-off. During take-off, a jetliner is generating enough thrust to compensate for the complete loss of thrust from one engine. For a twin, that is 200% of the minimum thrust required to allow climb-out after engine failure at Vr. If you have a back-up engine for "just in case", it would have to deploy and spool-up pretty quick to compensate for a failure just as the wheels leave the runway or soon after.
 
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RE: Single Engine Widebodied Aircraft - Possible?

Tue Jun 10, 2014 4:27 am

Quoting FrmrKSEngr (Reply 16):
For a twin, that is 200% of the minimum thrust required to allow climb-out after engine failure at Vr. If you have a back-up engine for "just in case", it would have to deploy and spool-up pretty quick to compensate for a failure just as the wheels leave the runway or soon after.

Which means you would have to have an engine that could withstand going from a dead stop to full thrust in about a second -- sounds like a rocket to me.
 
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RE: Single Engine Widebodied Aircraft - Possible?

Tue Jun 10, 2014 4:54 am

Quoting 7BOEING7 (Reply 17):
Which means you would have to have an engine that could withstand going from a dead stop to full thrust in about a second -- sounds like a rocket to me.


And the structure to withstand the impulse of 0lbs thrust to 64K lbs thrust in a second.

So, now we also have to add the rocket fuel system, just in case we need to use the rocket. Solid motor won't work as you need to be able to throttle back to make the approach. So liquid fuel tanks, pumps, etc. with the related safety concerns.
 
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Starlionblue
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RE: Single Engine Widebodied Aircraft - Possible?

Tue Jun 10, 2014 6:07 am

Quoting FrmrKSEngr (Reply 18):

Quoting 7BOEING7 (Reply 17):
Which means you would have to have an engine that could withstand going from a dead stop to full thrust in about a second -- sounds like a rocket to me.


And the structure to withstand the impulse of 0lbs thrust to 64K lbs thrust in a second.

So, now we also have to add the rocket fuel system, just in case we need to use the rocket. Solid motor won't work as you need to be able to throttle back to make the approach. So liquid fuel tanks, pumps, etc. with the related safety concerns.

Liquid fuel rockets are typically more controllable ("safer") than solid fueled ones. Not that either would be a good idea. 
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airmagnac
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RE: Single Engine Widebodied Aircraft - Possible?

Tue Jun 10, 2014 9:21 pm

Quoting LH707330 (Reply 14):
Are you by any chance referring to the Lear Fan design with the two turbines feeding a single prop? I doubt the FAA would go for such a configuration.

I wasn't actually thinking of any particular real-world design, but that's a good illustration.
Note that if we are to believe wiki, the reason the FAA didn't certify the design was not because of the layout itself, but rather because of worries about the mechanical transmission setup, namely the gear mixing the outputs of the 2 engines.
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DocLightning
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RE: Single Engine Widebodied Aircraft - Possible?

Tue Jun 10, 2014 10:44 pm

Quoting airmagnac (Reply 13):
If we could generate a different "useful" energy, which could be transmitted and controlled relatively easily (say, electrically), then the 2 functions could be seperated.
We could then consider a "single generation/multiple propulsion" architecture. This could be a single big generation unit located somewhere in the aircraft (most likely the tail cone, if we keep the tube-with-wings layout), driving a pair number of fans (to preserve symmetry).

One potential such arrangement involves a high-temperature fuel cell cracking hydrocarbon fuel at about 60% efficiency (as opposed to about 30% for modern combustion) to directly produce electrical energy. Two (or more) electrical fans could then be operated off this output (and the rest of the electrical needs of the aircraft).

Presumably, the FAA would still require two fuel cells and two electric motors in case one fails, especially if the aircraft is designed to fly over any body of water wider than a creek.
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airmagnac
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RE: Single Engine Widebodied Aircraft - Possible?

Wed Jun 11, 2014 6:22 pm

Quoting DocLightning (Reply 21):
the FAA would still require two fuel cells

Fuel cells are usually arranged in stacks. Considering only the stacks themselves, and not the heating/cooling and other associated components :
If a failure could affect a complete stack at once and its surroundings, then there would be a need for 2 physically seperate stacks.
If a failure that only affects the electrical circuit of a single stack for example, there would be a need for a second stack, but this could be packaged in the same "box" as the first one, so from the outside you would just see one single unit.
Otherwise, if only individual cells can be lost with a limited loss of power, a single stack might be enough.

As I said before, we're playing a little with the definition of "single-generator". It's the fun (but challenging) thing with electrical tech : it's so easy to combine and divide signals, and share functions among different parts, that it's difficult to define exactly where one thing stops and another one begins. I'd expect doctors to have the same issue with the human body  
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RE: Single Engine Widebodied Aircraft - Possible?

Fri Jun 13, 2014 4:17 pm

Quoting airmagnac (Reply 20):
I wasn't actually thinking of any particular real-world design, but that's a good illustration.

Another would have been the Ayres LM-200:
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RE: Single Engine Widebodied Aircraft - Possible?

Fri Jun 13, 2014 5:19 pm

Just remember that not that long ago people scoffed at the idea of ETOPS. Go back 50 years and people would laugh at large jet without a flight engineer for safety's sake, let alone a drone.
 
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RE: Single Engine Widebodied Aircraft - Possible?

Fri Jun 13, 2014 5:31 pm

Quoting vzlet (Reply 23):
Ayres LM-200

Didn't know that one, thanks
And people say the A380 is fugly...   
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DocLightning
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RE: Single Engine Widebodied Aircraft - Possible?

Fri Jun 13, 2014 5:48 pm

Quoting Penguins (Reply 24):
Just remember that not that long ago people scoffed at the idea of ETOPS. Go back 50 years and people would laugh at large jet without a flight engineer for safety's sake, let alone a drone.

ETOPS is a much different animal.

For single-engine passenger operations, you are talking about an engine that will never fail in billions of flight hours for just about any reason except fuel starvation or volcanic ash. It even has to be able to continue running flawlessly after ingesting a flock of birds.

First of all, how are you going to practically demonstrate that the engine will not fail in billions of flight hours without flying it for billions of flight hours? One billion seconds is about 33 years, so how long is your testing program going to last? Centuries? Millenia?

Second, no matter how advanced our technology gets, as long as we are dealing with materials made of protons, neutrons, and electrons, there *will* be failures.

Third, there are symmetry issues with mounting a single engine. Where are you going to put it? It's going to have to be huge (possibly as large as the fuselage itself). How are you going to transport it for AOG? Actually, that's a moot point because the engine must never fail for any reason. Do you see how absurd that gets?
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Starlionblue
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RE: Single Engine Widebodied Aircraft - Possible?

Sat Jun 14, 2014 5:29 am

Quoting Penguins (Reply 24):
Just remember that not that long ago people scoffed at the idea of ETOPS. Go back 50 years and people would laugh at large jet without a flight engineer for safety's sake, let alone a drone.

Certainly. However ETOPS is demonstrated and certified safe due under very strict conditions. If you can demonstrate and certify the same safety level for a single-engined widebody, then we're talking. But I don't see how that can happen given today's level of technology.

As DocLightning says, you'd have to prove that an engine never ever fails. That's a tall order.
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FrmrKSEngr
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RE: Single Engine Widebodied Aircraft - Possible?

Sat Jun 14, 2014 5:54 am

Quoting Starlionblue (Reply 27):
ETOPS

You need to be able to glide for 180 minutes and land after an engine failure.  
 
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Starlionblue
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RE: Single Engine Widebodied Aircraft - Possible?

Sat Jun 14, 2014 6:32 am

Quoting FrmrKSEngr (Reply 28):

Quoting Starlionblue (Reply 27):
ETOPS

You need to be able to glide for 180 minutes and land after an engine failure.

Strap a solid rocket booster to the belly. Just in case. 
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Faro
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RE: Single Engine Widebodied Aircraft - Possible?

Sat Jun 14, 2014 8:07 am

Quoting DocLightning (Reply 10):
If you can design and demonstrate an engine that will never ever fail for any reason whatsoever with 100.0% certainty, then I suppose so.

For argument's sake, let's suppose where in 2050 and engine reliablity is 100 times greater than what it was in 2014...I doubt the regulators will allow it...but one suspects that they will at least start thinking about it...


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DocLightning
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RE: Single Engine Widebodied Aircraft - Possible?

Sat Jun 14, 2014 7:05 pm

Quoting faro (Reply 30):
For argument's sake, let's suppose where in 2050 and engine reliablity is 100 times greater than what it was in 2014...I doubt the regulators will allow it...but one suspects that they will at least start thinking about it...

With two engines, you can statistically calculate the failure rate over billions of hours without actually having to fly those billions of hours to prove it. With one engine, there is no way to demonstrate that sort of failure rate without actually flying for billions of hours. Even with many engines, such a program would take centuries.

And remember, we're talking about designing an engine that can ingest a rock or a flock of geese and not fail. There would be no blade-off testing because blade-off must never happen.

Even the newest engines, like the PW1000 just tested or the brand new Trents on the QF A380 have had catastrophic failures. GENx, too. If you think that in another 35 years we'll be able to build engines that are failure-proof...well, then we'll have to disagree.

The only way I could see this happening is some high-strength, high-heat nanotechnological materials that rapidly self-repair under fully-loaded conditions so that they could stop a crack before it leads to failure. I think that's more than 35 years off.
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RE: Single Engine Widebodied Aircraft - Possible?

Sun Jun 15, 2014 11:44 am

If I understand correctly, ramjet engines do not have moving parts (except for the fuel pumps), und should be much more reliable.

But they need more than turtle speed to get going...


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mandala499
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RE: Single Engine Widebodied Aircraft - Possible?

Sun Jun 15, 2014 9:07 pm

Quoting LH707330 (Reply 14):
Are you by any chance referring to the Lear Fan design with the two turbines feeding a single prop? I doubt the FAA would go for such a configuration.

We had since the Ayres LM-200, and the proposed Soloy Twinpac for the Caravan...

Quoting airmagnac (Reply 20):
Note that if we are to believe wiki, the reason the FAA didn't certify the design was not because of the layout itself, but rather because of worries about the mechanical transmission setup, namely the gear mixing the outputs of the 2 engines.

Yes, it was the gearbox reliability... if we think single propeller with multiple engines won't work... we wouldn't be having multi-engine helicopters now would we...   

Quoting flyingturtle (Reply 32):
If I understand correctly, ramjet engines do not have moving parts (except for the fuel pumps), und should be much more reliable.

But they need more than turtle speed to get going...

Being silly here... But why not have the single engine to fan the ramjet so we have only 1 complex engine assisting 2 simpler ones?   
Yea yea yea, I know... old concept...
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Posts: 3900
Joined: Sat Aug 09, 2003 7:27 pm

RE: Single Engine Widebodied Aircraft - Possible?

Tue Jul 01, 2014 10:40 pm

I hope not! Look, I feel an airliner, rather it is a widebody, narrow body or reginal jet, need at least two engines and two pilots. I just started to somewhat like twin engine wideodies in the last couple of years.
 
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DocLightning
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RE: Single Engine Widebodied Aircraft - Possible?

Wed Jul 02, 2014 5:19 am

Quoting flyingturtle (Reply 32):

If I understand correctly, ramjet engines do not have moving parts (except for the fuel pumps), und should be much more reliable.


It's true. Most ramjet designs have figured a single engine. Although they all assume that there is a fan engine to get it up to speed.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
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lpdal
Posts: 1970
Joined: Sat Mar 24, 2012 9:49 pm

RE: Single Engine Widebodied Aircraft - Possible?

Thu Jul 03, 2014 6:36 am

The Cirrus Vision is a single engine VLJ slated for later release with a single jet engine. I'm surprised nobody has mentioned it yet.


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flyingturtle
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RE: Single Engine Widebodied Aircraft - Possible?

Thu Jul 03, 2014 11:43 am

And the Diamond D-Jet (a project that is currently halted, but not cancelled according to Wikipedia):



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Reading accident reports is what calms me down

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