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Is The 787 The Last Airliner Without Bleed Air?  
User currently offlinea380900 From France, joined Dec 2003, 1117 posts, RR: 1
Posted (1 year 10 months 1 day 22 hours ago) and read 5810 times:

If I'm not mistaken, the A350 will have a conventional electric system. Are the battery problems of the 787 the death-knell of all electric airliners? Were the supposed advantages that significant to begin with?

Or is it certain that technological improvement WILL at some point in the future beat conventional solutions? (10, 20 or 50 years away). In other words, is this all-electric technology likely to be a dead-end?

Or put yet another way: will the successor of the 737 have bleed air?

[Edited 2013-01-30 06:21:39]

24 replies: All unread, jump to last
 
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 1, posted (1 year 10 months 1 day 21 hours ago) and read 5799 times:

Quoting a380900 (Thread starter):
If I'm not mistaken, the A350 will have a conventional electric system.

It depends on what you mean by "conventional". It will not power as much using electrics as the 787. However, the A380/787/A350 are all using considerably more modern generators and architectures than predecessor airplanes. I would expect the A350 to be very similar to the A380, just scaled.

Quoting a380900 (Thread starter):
Are the battery problems of the 787 the death-knell of all electric airliners?

No. The battery problems of the 787 have nothing to do with the all-electric architecture because the battery isn't part of any of the new parts of the electrical system that make the all-electric architecture work. The 787, using the same battery and components, would have experienced the same problems with a conventional electrical architecture.

Quoting a380900 (Thread starter):
Were the supposed advantages that significant to begin with?

Yes. There are arguments about how much weight actually got saved, but the efficiency and maintenance benefits (as far as I know) aren't in dispute.

Quoting a380900 (Thread starter):
Or is it certain that technological improvement WILL at some point in the future beat conventional solutions? (10, 20 or 50 years away). In other words, is this all-electric technology likely to be a dead-end?

One of the big arguments for all-electric is that there is a lot of room for technological improvement in electronics (which are being exploited by all the OEM's) while there pneumatics are perceived to have hit the wall...they've been developed for so many decades that they're getting close to the theoretical limit. There will always be a need for a high-energy distribution system on aircraft. Absent a step-change in one of the other very mature technologies like hydraulic, pneumatic, or mechanical and absent an all-new technology (plasma?), electrical is the best bet.

Quoting a380900 (Thread starter):
Or put yet another way: will the successor of the 737 have bleed air?

That's a somewhat different question because of some of the scaling factors involved. For similar reasons that CFRP is better on large aircraft than small, the all-electric architecture may not be able to buy its way onto smaller aircraft.

Tom.


User currently offlineferpe From France, joined Nov 2010, 2805 posts, RR: 59
Reply 2, posted (1 year 10 months 1 day 18 hours ago) and read 5642 times:

The 787 is the first mostly electrical aircraft, not the last.

I don't think there is any question the architecture is better then the classical bleed + electrical, it is just a matter on when you switch and why. Actually the A350 is more electrical then the 787 in the flight controls, it re-uses the A380 2 noraml hydraulic flight control systems + one electrically driven local circuit. So Airbus have also started a more electrical route, just at a different point.

Given that they had a very recent architecture (the A380) that they could reuse for the 350 it made no sense for them to redo all that investment, they could inherit if for the 350 and still be competitive given a more efficient engine (one generation newer then 787). The 787 program did not have this situation, the last program (777) was some 15 years old design-wise in 2003, the bit the bullet, it has some challenges but will pay in the 40 years the 787 architecture will live, we are at year 2 now.



Non French in France
User currently offlinebikerthai From United States of America, joined Apr 2010, 2170 posts, RR: 4
Reply 3, posted (1 year 10 months 1 day 16 hours ago) and read 5523 times:

Quoting a380900 (Thread starter):
Are the battery problems of the 787 the death-knell of all electric airliners?

If the problem with the 787 electric system is just the battery, then there is room for improvement.

Right now battery technology is just at the middle of the development curve. How long did it take for industry to go from Dry-cell, to Alkaline to NiCd, NiMH and now Lithium.

With the massive development of batteries for the Auto industry, I'm pretty sure there would be new breakthrough in the near future that can provide power densities comparable if not better than Lithium. Boeing is doing research on fuel-cell for aircraft use. There may be other technology that will support the electrical needs of future aircraft like the 787.

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineMax Q From United States of America, joined May 2001, 4751 posts, RR: 18
Reply 4, posted (1 year 10 months 1 day 11 hours ago) and read 5328 times:

I certainly hope so:



Two BA Pilots died recently from inhaling toxic fumes at work.


Can't post the link but easy to Google.


Pretty sad.



The best contribution to safety is a competent Pilot.
User currently offlineCARST From Germany, joined Jul 2006, 836 posts, RR: 2
Reply 5, posted (1 year 10 months 1 day 1 hour ago) and read 5139 times:

Quoting Max Q (Reply 4):
I certainly hope so:



Two BA Pilots died recently from inhaling toxic fumes at work.


Can't post the link but easy to Google.


Pretty sad.

I don't understand what is you point MaxQ? I know that the fumes are a hot topic, we recently had the 4U emergency landing here in Germany because of the fumes, but where is the connection to the 787? Please correct me if I am wrong, but AFAIK in the 787 pneumatic and hydraulic systems were replaced by electric systems, but it had no effect on the aircon system. Doesn't the aircon still gets bleedair from the engines? I think when they talk about bleedless engines they just talk about the bleed air used to start the engines on earlier aircraft and now use generators to start the engine. I mean they still need compressed and heated air for the cabin.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17118 posts, RR: 66
Reply 6, posted (1 year 10 months 1 day 1 hour ago) and read 5135 times:

Quoting CARST (Reply 5):
I don't understand what is you point MaxQ? I know that the fumes are a hot topic, we recently had the 4U emergency landing here in Germany because of the fumes, but where is the connection to the 787?

If I'm not mistaken Max Q is answering the question posed in the topic. Is The 787 The Last Airliner Without Bleed Air? And he's saying "I certainly hope so."



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 7, posted (1 year 10 months 22 hours ago) and read 5049 times:

Quoting CARST (Reply 5):
Please correct me if I am wrong, but AFAIK in the 787 pneumatic and hydraulic systems were replaced by electric systems, but it had no effect on the aircon system.

The pneumatic system was replaced. The hydraulic system was not, although hydraulic pumps that on the 777 were driven by the pneumatic system are now driven by the electrical system on the 787.

Quoting CARST (Reply 5):
Doesn't the aircon still gets bleedair from the engines?

No. There is no air duct from the engines to the airplane. The only bleed tap on the engines (other than for engine operation, like surge control) is for the nacelle anti-ice.

Pneumatic-powered hydraulic pumps are now electric.
Pneumatic-powered wing anti-ice is now electric.
Pneumatic-powered ECS is now electric.

If you look at a 787's wing-to-body fairings you'll see the normal NACA scoop on each side for the ram air inlet and, above that, an inlet that's standing proud of the skin like an old-style automotive supercharger intake...that's the air inlet for the ECS system. Electric compressors take outside air directly from this scoop and compress it to provide high-pressure air to the ECS system.

Quoting CARST (Reply 5):
I think when they talk about bleedless engines they just talk about the bleed air used to start the engines on earlier aircraft and now use generators to start the engine. I mean they still need compressed and heated air for the cabin.

No. There is literally no air duct between the engine and the airplane. The compressed and heated air for the cabin comes from four electrically driven compressors in the wing-to-body fairing. Each pair of compressors feeds one ECS pack. Among other things, this totally seperates the cabin air supply from the engines so no type of oil leak or fluid ingestion by the engine will end up in the cabin air.

Tom.


User currently offlinePolot From United States of America, joined Jul 2011, 2314 posts, RR: 1
Reply 8, posted (1 year 10 months 22 hours ago) and read 5046 times:

Quoting Starlionblue (Reply 6):
If I'm not mistaken Max Q is answering the question posed in the topic. Is The 787 The Last Airliner Without Bleed Air? And he's saying "I certainly hope so."

I think he was misreading the question though- the OP is asking if all future airliners will continue with bleed air. His reasoning doesn't really support his answer.


User currently offlinebikerthai From United States of America, joined Apr 2010, 2170 posts, RR: 4
Reply 9, posted (1 year 10 months 21 hours ago) and read 5030 times:

Which brings me to a question . . .

With turbo props, are you taking bleed air from the engines?

If not, then technically speaking the answer is no?

Also technically per Tom, the answer question is irrelevant because the 787 does take bleed air. Except just for only one reason now - inlet anti ice.

Now if we are talking about the excessive electrical power required to power all the other 787 systems . . . then the answer is simple . . . obtain a new power source (fuel cell etc. . . ) . . . add generator capacity (larger or more generators aka Wedgetail).

As we have discussed, the battery issue only peripherally related to the current 787 problem. That can be solved . . .   

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineCARST From Germany, joined Jul 2006, 836 posts, RR: 2
Reply 10, posted (1 year 10 months 21 hours ago) and read 5000 times:

Quoting tdscanuck (Reply 7):
No. There is literally no air duct between the engine and the airplane. The compressed and heated air for the cabin comes from four electrically driven compressors in the wing-to-body fairing. Each pair of compressors feeds one ECS pack. Among other things, this totally seperates the cabin air supply from the engines so no type of oil leak or fluid ingestion by the engine will end up in the cabin air.

Thanks for correcting me Tom, I must have really misread that when discussed before.

So MaxQ is 100%, lets hope the Dreamliners design philosophy gets adapted for all new aircraft getting rid of the polluted cabin air.


User currently offlineMax Q From United States of America, joined May 2001, 4751 posts, RR: 18
Reply 11, posted (1 year 10 months 14 hours ago) and read 4846 times:

Quoting Starlionblue (Reply 6):

If I'm not mistaken Max Q is answering the question posed in the topic. Is The 787 The Last Airliner Without Bleed Air? And he's saying "I certainly hope so."

Correct.



The best contribution to safety is a competent Pilot.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17118 posts, RR: 66
Reply 12, posted (1 year 10 months 11 hours ago) and read 4764 times:

Quoting tdscanuck (Reply 7):
Quoting CARST (Reply 5):
Doesn't the aircon still gets bleedair from the engines?

No. There is no air duct from the engines to the airplane.

Question: Does the 787 thus use the same arrangement as on the DC-8, which had two airscoops in the nose?

Quoting bikerthai (Reply 9):
Which brings me to a question . . .

With turbo props, are you taking bleed air from the engines?

I can't speak for all turboprops, but yes sure. Even a turboprop as small as the Cessna Caravan uses engine bleed air for cabin heating



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinerwessel From United States of America, joined Jan 2007, 2392 posts, RR: 2
Reply 13, posted (1 year 10 months 11 hours ago) and read 4747 times:
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Quoting bikerthai (Reply 9):
With turbo props, are you taking bleed air from the engines?

It depends. Some do, some don't (usually only the smaller ones don't).

Quoting bikerthai (Reply 9):
Also technically per Tom, the answer question is irrelevant because the 787 does take bleed air. Except just for only one reason now - inlet anti ice.

That's a fairly small use, and very local. Also remember that basically all modern jet engines have bleeds for operational reasons - you can't get them to run reliably in all conditions otherwise. But the total bleeds for the 787 are tiny compared to the more conventional architecture.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 14, posted (1 year 10 months 9 hours ago) and read 4703 times:

Quoting Starlionblue (Reply 12):
Question: Does the 787 thus use the same arrangement as on the DC-8, which had two airscoops in the nose?

Basically, yes. The scoops are in physically different spots (and I think the DC-8 used pneumatic turbocompressors rather than electric compressors) but the architecture is basically the same as far as I know.

Quoting rwessel (Reply 13):
Quoting bikerthai (Reply 9):
Also technically per Tom, the answer question is irrelevant because the 787 does take bleed air. Except just for only one reason now - inlet anti ice.

That's a fairly small use, and very local.

That's the big reason it was done...you could easily do electric nacelle anti-ice (you're already running a ton of power out there to anti-ice the wing). But the nacelle is *right there*, needs a small tube, doesn't need a precooler, and doesn't really care about duct burst/overheat/all-the-other-fun-pneumatic-failure-modes. As soon as you bring that air supply up into a precooler and through a giant duct into the leading edge, the fun really starts.

Tom.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17118 posts, RR: 66
Reply 15, posted (1 year 10 months 6 hours ago) and read 4629 times:

Quoting tdscanuck (Reply 14):
I think the DC-8 used pneumatic turbocompressors rather than electric compressors

Hang on. Pneumatic turbocompressors? The DC-8 used air pressure to compress air? Awesome.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinebikerthai From United States of America, joined Apr 2010, 2170 posts, RR: 4
Reply 16, posted (1 year 9 months 4 weeks 1 day 21 hours ago) and read 4535 times:

Quoting tdscanuck (Reply 14):
you could easily do electric nacelle anti-ice

I think not if you keep the inlet lip as all aluminum. When you can do a composite inlet lip with all its ramifications, then you'll have a shot of an electric nacelle anti-ice. (Maybe a titanium inlet with induction heating?)  

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlinerwessel From United States of America, joined Jan 2007, 2392 posts, RR: 2
Reply 17, posted (1 year 9 months 4 weeks 1 day 19 hours ago) and read 4475 times:
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Quoting bikerthai (Reply 16):
I think not if you keep the inlet lip as all aluminum. When you can do a composite inlet lip with all its ramifications, then you'll have a shot of an electric nacelle anti-ice. (Maybe a titanium inlet with induction heating?)

Why would it matter if the inlet leading edge were aluminum?


ed: spelling

[Edited 2013-02-01 09:35:37]

User currently offlinebikerthai From United States of America, joined Apr 2010, 2170 posts, RR: 4
Reply 18, posted (1 year 9 months 4 weeks 1 day 17 hours ago) and read 4436 times:

Quoting rwessel (Reply 17):

Aluminum is a great conductor of heat. The inlet lip of these engines are huge and you may not need to heat all of it. When you use electrical energy to generate the heat, you want to put it only where it is needed. If you can localize this energy using a "composite" design you can reduce the energy required.

Titanium doesn't conduct heat as well, so it may work better, although I have no analysis to say it would work either.

Steel would be good also because you can efficiently heat the steel using induction heating . . . although the lip would be heavier.

I'm sure some great minds are working on this problem right now.

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlinesweair From Sweden, joined Nov 2011, 1831 posts, RR: 0
Reply 19, posted (1 year 9 months 4 weeks 1 day 3 hours ago) and read 4291 times:

The question should be if any new pneumatic airplane will be done after the A350 and C series.. Next question when will aircraft have electronic motors instead of hydraulic?

User currently offlineStarlionblue From Greenland, joined Feb 2004, 17118 posts, RR: 66
Reply 20, posted (1 year 9 months 4 weeks 1 day 3 hours ago) and read 4288 times:

Quoting sweair (Reply 19):
Next question when will aircraft have electronic motors instead of hydraulic?

First of all, it is electric, not electronic. To answer your question, it will take a long time. Hydraulic has many advantages.

I'm not a huge expert on hydraulics but here goes. Any expert feel free to correct me as usual!

Hydraulic is a very efficient way of transferring force. Even a hydraulic system the size of the 380s loses hardly any force even if the power pack is at one end and the actuator is at the other end of the aircraft. The disadvantages are weight, the requirement for it to be sealed against water, and complexity.

It is also easy to exert force quickly. AFAIK Electric motors have a hard time being as fast and strong without using large amounts of power.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinesweair From Sweden, joined Nov 2011, 1831 posts, RR: 0
Reply 21, posted (1 year 9 months 4 weeks 1 day 3 hours ago) and read 4286 times:

Quoting Starlionblue (Reply 20):

But I guess the electric motors have a lot more future potential than hydraulic? In what area do we see most progress?

Maybe in 30 years airliners will be almost complete electric?


User currently offlinerwessel From United States of America, joined Jan 2007, 2392 posts, RR: 2
Reply 22, posted (1 year 9 months 4 weeks 1 day ago) and read 4245 times:
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Quoting bikerthai (Reply 18):
Aluminum is a great conductor of heat. The inlet lip of these engines are huge and you may not need to heat all of it. When you use electrical energy to generate the heat, you want to put it only where it is needed. If you can localize this energy using a "composite" design you can reduce the energy required.

The panels are also pretty thin, and the conduction issue you're worrying about would only be along the "thin" direction, and would be very small compared to what was conducted from the heaters on the inside of the panel to the outside (opposite side) of the panel.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17118 posts, RR: 66
Reply 23, posted (1 year 9 months 4 weeks 10 hours ago) and read 4049 times:

Quoting sweair (Reply 21):
Quoting Starlionblue (Reply 20):

But I guess the electric motors have a lot more future potential than hydraulic? In what area do we see most progress?

Maybe in 30 years airliners will be almost complete electric?

Electric motors have been around for a while. Unless we see some breakthrough in conductors, I don't know if the improvements are predicted to be so huge. And hydraulic can also be improved, for example with higher system pressures and new fluids.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinebikerthai From United States of America, joined Apr 2010, 2170 posts, RR: 4
Reply 24, posted (1 year 9 months 3 weeks 5 days 22 hours ago) and read 3759 times:

Quoting rwessel (Reply 22):
The panels are also pretty thin, and the conduction issue you're worrying about would only be along the "thin" direction,

Those lips are thicker than you would think. This is because of requirements and manufacturing process.

The lip have to take damage from bird strike. You don't want to significantly distort the flow by a damaged lip which may cause the engine to stall at the most critical time - take off.

Most lip are currently formed - the forming process usually have the thickest skin at the fastener row and the thinnest skin at the lip apex - where you need to be damage tolerant.

Quoting rwessel (Reply 22):
and would be very small compared to what was conducted from the heaters on the

Small comparatively, yes, but not insignificant . . .

But of course, you are right that if you design a system clever enough, you can account for the heat bleed-off as part of your "anti-ice" zone and regain the efficiency.

Now you just have to figure out an efficient and robust way to get electrical heat to the inlet . . . induction heating is efficient, but the amount of iron involved may make it too heavy.

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
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