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borism
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Ugly Thing Near 787 Packs

Mon Jul 19, 2010 2:37 pm

I've always wanted to ask this but never got to it: what are those two ugly noticeably standing out things situated under aircon pack entrances on the 787 wing box? They look like another air openings complimentary to pack entrances but they seem to have some kind of ramp in front of them.
 
tdscanuck
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RE: Ugly Thing Near 787 Packs

Mon Jul 19, 2010 11:13 pm

Quoting borism (Thread starter):
I've always wanted to ask this but never got to it: what are those two ugly noticeably standing out things situated under aircon pack entrances on the 787 wing box? They look like another air openings complimentary to pack entrances but they seem to have some kind of ramp in front of them.

Cabin air compressor inlets. The "ugly noticeably standing out things" are actually the aircon pack entrances...the scoops above them are the ram air inlets.

On aircraft with bleed-based air conditioning, the only inlets you see are the ram air inlets...the actual air to the packs is coming from a duct from the engine, which you can't see from outside.

Tom.
 
zainmax
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RE: Ugly Thing Near 787 Packs

Tue Jul 20, 2010 6:32 pm

This air is used on higher altitudes mixed with the bleed air for Cabin air conditioning
 
Tristarsteve
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RE: Ugly Thing Near 787 Packs

Tue Jul 20, 2010 9:05 pm

Quoting zainmax (Reply 2):
mixed with the bleed air

We are talking about a B787, there is no bleed air!
 
tarzanboy
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RE: Ugly Thing Near 787 Packs

Tue Jul 20, 2010 9:18 pm

Can someone please post a picture with the Packs on?
 
zainmax
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RE: Ugly Thing Near 787 Packs

Wed Jul 21, 2010 3:09 am

Quoting Tristarsteve (Reply 3):
We are talking about a B787, there is no bleed air!

Is there any new method introduced in B787 for ar conditioning ?
I m talking about the bleed air from engine, ofcourse we are using it.
 
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PITingres
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RE: Ugly Thing Near 787 Packs

Wed Jul 21, 2010 11:53 am

Quoting zainmax (Reply 5):
Is there any new method introduced in B787 for ar conditioning ?

It's all-electric. There is no bleed from the engines on the 787.
 
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Jetlagged
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RE: Ugly Thing Near 787 Packs

Wed Jul 21, 2010 1:28 pm

Quoting zainmax (Reply 2):
This air is used on higher altitudes mixed with the bleed air for Cabin air conditioning
Quoting Tristarsteve (Reply 3):
We are talking about a B787, there is no bleed air!

Even on traditional bleed air systems, cooling air from the ram air inlets is never mixed with bleed air.
 
Tristarsteve
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RE: Ugly Thing Near 787 Packs

Wed Jul 21, 2010 2:06 pm

Quoting zainmax (Reply 5):
Is there any new method introduced in B787 for ar conditioning ?

No an old method is reintroduced.
On the large pressurised piston aircraft there was no air to bleed. So they used air compressors to collect ambient air and pressurise it for the cabin. (This was separate from the supercharger for the induction air) This same idea using Rootes Blowers was on early jet aircraft as well, and about its last main use was on the Vickers VC10. Since then, engine bleed has been used with varying success. Good on most aircraft but not on the Bae 146 series.

Now the B787 goes back to this idea. Air is scooped from outside, and pressurised with big compressors and sent into the cabin.
 
zainmax
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RE: Ugly Thing Near 787 Packs

Wed Jul 21, 2010 4:28 pm

Quoting PITingres (Reply 6):
It's all-electric. There is no bleed from the engines on the 787.

Thanks for letting me know this thing, I have found the system and read it in Boeing's Aero magazine.
Would like to see the inlet pictures and illustration of the system.

Cheers
 
aviopic
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RE: Ugly Thing Near 787 Packs

Wed Jul 21, 2010 8:22 pm

Quoting zainmax (Reply 5):
Is there any new method introduced in B787 for ar conditioning ?

It's more like back to the future  
Quoting Tristarsteve (Reply 8):
On the large pressurised piston aircraft there was no air to bleed.

Not only on piston aircraft.

View Large View Medium
Click here for bigger photo!

Photo © Willem Honders


1958 and bleedless.
2 generators and 1 compressor per engine.
 
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Francoflier
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RE: Ugly Thing Near 787 Packs

Thu Jul 22, 2010 3:57 am

Quoting Aviopic (Reply 10):
2 generators and 1 compressor per engine.

Make that 2 generators, 1 compressor and 1 blower...  
The compressor was for the compressed air system for gear and brakes, the blower was for the aircon, and was pretty ineffective too.
 
Tristarsteve
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RE: Ugly Thing Near 787 Packs

Thu Jul 22, 2010 8:26 am

Quoting francoflier (Reply 11):
The compressor was for the compressed air system for gear and brakes, the blower was for the aircon, and was pretty ineffective too.

I found the compressor not much good either.
When I worked at BAH we operated an F27 shuttle to DHA (old Dharan airport) every two hours. But the flight time was only about 10 mins, and we had to pump up the air system every time it landed in BAH.
 
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Francoflier
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RE: Ugly Thing Near 787 Packs

Thu Jul 22, 2010 11:15 am

Quoting Tristarsteve (Reply 12):
I found the compressor not much good either.

Don't remind me... I remember the days when we had to sit forever on the ramp all buttoned up with 40 deg C outside waiting for the pressure to get back to 1800 for Take Off.
Which, ironically, also outlined the severe inadequacy of the blowers at the same time...

The good old days.

Anyhow. I figure (and hope) the technology has improved significantly since then and the 787 won't suffer from the hot cabin syndrome.
 
soon7x7
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RE: Ugly Thing Near 787 Packs

Thu Jul 22, 2010 1:24 pm

Quoting jetlagged (Reply 7):


It was on the A300, ironically I was reading last night about the AC systems on the A300, the conventional rapid cooling of hot air via air recycling machines modified with heat from bleed air to accurately control the 4 on board zones. But the A300 by today's standards is now part of the geriatric community...sadly. Interesting that the 787 does not utilize bleed air..no doubt a weight savings attribute?...No?...Si?
 
slz396
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RE: Ugly Thing Near 787 Packs

Thu Jul 22, 2010 1:37 pm

Quoting soon7x7 (Reply 14):
Interesting that the 787 does not utilize bleed air

Mind you, there's still bleed air from the engines for engine anti-icing purposes, so saying the 787 is bleedless in actually not correct.

As others have pointed out in the mean time, the concept isn't as revolutionary either, in fact it is very old school (dating back to piston engines, and last used on the VC-10), yet the hope is that technology has evolved enough to be using this once not so very reliable technique again, while benefiting from its weight reductions.

Another thing the 787 has 'stolen' from long time ago is the bleedless start of its engines: it is said the 787 starts it engines with an electric starter motor, just like the Bae146. If I have understood it correctly, the generator IS also the starting motor on the 787, so just how do you start the engine then in case a generator is inop then, or is that no longer allowed under MEL like on most other planes? And how do you restart an engine in flight, should you even have to do so after a previous generator failure? Or can you not restart a flamed out engine in flight if you have lost also a generator in flight?

[Edited 2010-07-22 06:46:58]
 
tdscanuck
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RE: Ugly Thing Near 787 Packs

Thu Jul 22, 2010 5:06 pm

Quoting slz396 (Reply 15):
Mind you, there's still bleed air from the engines for engine anti-icing purposes, so saying the 787 is bleedless in actually not correct.

Engine anti-ice is entirely within the nacelle. There is no pneumatic connection in the strut and the airplane doesn't take any air from the engine...that's what they mean by "bleedless."

If you really want to go hard-over, no engine can be bleedless because you always have surge control valves in the engine.

Quoting slz396 (Reply 15):
If I have understood it correctly, the generator IS also the starting motor on the 787, so just how do you start the engine then in case a generator is inop then, or is that no longer allowed under MEL like on most other planes?

Each engine has two generators. Either one can start the engine.

Quoting slz396 (Reply 15):
And how do you restart an engine in flight, should you even have to do so after a previous generator failure?

Using the working generator, or windmill start.

Quoting slz396 (Reply 15):
Or can you not restart a flamed out engine in flight if you have lost also a generator in flight?

You can.

Tom.
 
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bikerthai
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RE: Ugly Thing Near 787 Packs

Thu Jul 22, 2010 6:35 pm

Quoting tdscanuck (Reply 16):

Each engine has two generators.

Oh, so that is how they are able to get extra power to drive the electrical system that replaced the bleed driven system . . . and then some (a laptop at every seat?).

bikerthai
 
aviopic
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RE: Ugly Thing Near 787 Packs

Thu Jul 22, 2010 6:56 pm

Quoting francoflier (Reply 11):
Make that 2 generators, 1 compressor and 1 blower...

Ok, you win  
Quoting francoflier (Reply 11):
The compressor was for the compressed air system for gear and brakes, the blower was for the aircon, and was pretty ineffective too.
Quoting Tristarsteve (Reply 12):
I found the compressor not much good either.

If the system is well maintained it didn't have much problems.
Although an air system is more sensitive for "rough" mechanics more used to the oily bits.

Quoting Tristarsteve (Reply 12):
But the flight time was only about 10 mins, and we had to pump up the air system every time it landed in BAH.

Not raising and lowering the gear might have done the trick without pumping  
Quoting slz396 (Reply 15):
Another thing the 787 has 'stolen' from long time ago is the bleedless start of its engines:

No body is stealing anything.
It's just that everybody is looking at each other and using their idea's as it always has happend.

Quoting bikerthai (Reply 17):
Oh, so that is how they are able to get extra power to drive the electrical system that replaced the bleed driven system . . . and then some (a laptop at every seat?).

Probably not.
The more electrical power you derive from the engine the more fuel it will use.
 
slz396
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RE: Ugly Thing Near 787 Packs

Thu Jul 22, 2010 8:27 pm

Quoting tdscanuck (Reply 16):
Engine anti-ice is entirely within the nacelle. There is no pneumatic connection in the strut and the airplane doesn't take any air from the engine...that's what they mean by "bleedless"

Doesn't matter: it is still a significant air bleed, so the engine isn't fully bleedless and yes, engines can be entirely bleedless (some of the bleedless engines of 50 years ago were entirely bleedless), but those on the 787 aren't contrary to what is widely believed...
 
tdscanuck
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RE: Ugly Thing Near 787 Packs

Fri Jul 23, 2010 1:57 am

Quoting Aviopic (Reply 18):
The more electrical power you derive from the engine the more fuel it will use.

True, but extracting electrical power is way more efficient than extracting pneumatic power, so the fuel hike is considerably smaller.

Quoting slz396 (Reply 19):
Doesn't matter: it is still a significant air bleed

Nacelle anti-ice is probably the smallest pneumatic load on the entire aircraft (in a conventional bleed architecture). It's not "significant" compared to what's saved by not running wing anti-ice, engine start, or air conditioning off bleed air.

Quoting slz396 (Reply 19):
so the engine isn't fully bleedless

Of course not. Nobody claimed the *engines* were bleedless.

Quoting slz396 (Reply 19):
but those on the 787 aren't contrary to what is widely believed...

Anyone who believes the 787 runs bleedless engines just isn't paying attention to engine architecture. Boeing has always said the 787 has a "bleedless architecture" and that's true.

Tom.
 
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Jetlagged
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RE: Ugly Thing Near 787 Packs

Mon Jul 26, 2010 12:53 am

Quoting soon7x7 (Reply 14):
It was on the A300, ironically I was reading last night about the AC systems on the A300, the conventional rapid cooling of hot air via air recycling machines modified with heat from bleed air to accurately control the 4 on board zones. But the A300 by today's standards is now part of the geriatric community...sadly. Interesting that the 787 does not utilize bleed air..no doubt a weight savings attribute?...No?...Si?

The A300 system is conventional in that ram air cools bleed air by means of a heat exchanger. This ram air does not mix with the bleed air passing through the ACM.

There is a separate emergency ram air inlet in front of the cooling air inlet of pack 1. It provides fresh air to ventilate the cabin during unpressurised flight. The A300 is not unique in that respect.
 
wingscrubber
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RE: Ugly Thing Near 787 Packs

Mon Jul 26, 2010 2:31 am

So Tom, why then were the larger, heavier, less reliable bootstrap hydraulic reservoirs chosen on the 787 instead of the typical bleed-air pressurized air-over-oil reservoirs that boeing's used for years? Seems that if engine-inlet bleed air is allowed in boeing's 'no-bleed architecture' then reservoir pressurization bleed air could have been as well?
 
tdscanuck
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RE: Ugly Thing Near 787 Packs

Mon Jul 26, 2010 3:55 am

Quoting Wingscrubber (Reply 22):
So Tom, why then were the larger, heavier, less reliable bootstrap hydraulic reservoirs chosen on the 787 instead of the typical bleed-air pressurized air-over-oil reservoirs that boeing's used for years?

Well, for one, the bootstrap reservoirs aren't larger and I rather suspect they're more reliable in this case, although obviously only time will tell on that front.

The major reason, I would assume, is so that they can use the same reservoir design for all three hydraulic systems.

Quoting Wingscrubber (Reply 22):
Seems that if engine-inlet bleed air is allowed in boeing's 'no-bleed architecture' then reservoir pressurization bleed air could have been as well?

Having air-over-oil would require a pneumatic duct from the engine to the airplane...and there isn't one. That's the essence of what they mean by "no bleed architecture"...the airplane doesn't have an air connection to the engine. A whole lot of the savings of having no pneumatics is not having to worry about the ducting and associated leak detection hardware and failure modes. Given that the engine inherently has all that hardware and failure modes anyway (since nobody's even thought of how to design a jet engine that doesn't contain hot compressed air), using pneumatics for the nacelle anti-ice imposes essentially no additional burden. Taking pneumatics off the engine and to the airplane is where all the trouble starts.

Tom.
 
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bikerthai
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RE: Ugly Thing Near 787 Packs

Mon Jul 26, 2010 2:21 pm

Quoting tdscanuck (Reply 23):
using pneumatics for the nacelle anti-ice imposes essentially no additional burden.

The amount of titanium/nickle alloy ducting from the engine to the inlet cowl is much less than from the engine to the fuselage  

And I would think that given the opportunity, if there was a viable alternative, they would have got rid of the requirement for bleeding air for the engine inlet anti-ice also.

bikerthai
 
tdscanuck
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RE: Ugly Thing Near 787 Packs

Tue Jul 27, 2010 1:50 am

Quoting bikerthai (Reply 24):
And I would think that given the opportunity, if there was a viable alternative, they would have got rid of the requirement for bleeding air for the engine inlet anti-ice also.

That's my guess also, but I can't see how that trade would ever work out...all the power handling panels are in the EE bays, so you're talking about running wires from the engine to the fuselage, through a controller, then back out to the nacelle lip skin. The way it's currently implemented you've got a very short pneumatic duct run that's totally contained on the engine in a space that's already got overheat detection and fire protection.

Tom.
 
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bikerthai
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RE: Ugly Thing Near 787 Packs

Tue Jul 27, 2010 2:18 pm

It would only work if you can tap directly from the generator with a system that is robust enough not to require "clean" power. Also you would not need the inlet lip forward bulkhead to be titanium (weight and cost savings?).

Too bad induction heating doesn't work well with aluminum . . .
I wonder if induction heating works with a titanium inlet lip?

bikerthai
 
tdscanuck
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RE: Ugly Thing Near 787 Packs

Wed Jul 28, 2010 5:34 am

Quoting bikerthai (Reply 26):
I wonder if induction heating works with a titanium inlet lip?

My head is spinning at the idea of trying to certify an induction heater that close to a bunch of antennas, wiring, and critical computers.

Tom.
 
wingscrubber
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RE: Ugly Thing Near 787 Packs

Fri Jul 30, 2010 4:30 am

As a matter of fact Tom, I've just done a trade study for the air/oil reservoirs vs bootstrap at work. Air/oil reservoirs have no internal moving parts, plus they can be more compact for a given fluid volume (smaller envelope)due to having no protruding master piston (pressure side).

I asked the question because at one point (back in '07) Boeing still intended to use the traditional air/oil reservoirs that they've made in house for years, but they subsequently changed their minds and selected a Parker bootstrap reservoir.

Bleed air take-off for a reservoir alone is very small - smaller than inlet anti ice, would have been no more difficult than a hydraulic line, plus reservoirs can sometimes be located in the engine pylon. (not sure where they are on 787)

Just seems puzzling when Boeing has an in-house capability for a cheaper, lighter, more reliable component but decided to farm out anyway just to be more 'bleedless'!
 
tdscanuck
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RE: Ugly Thing Near 787 Packs

Fri Jul 30, 2010 4:50 am

Quoting Wingscrubber (Reply 28):
Air/oil reservoirs have no internal moving parts, plus they can be more compact for a given fluid volume (smaller envelope)due to having no protruding master piston (pressure side).

Gotcha...I thought you meant they required less fluid volume. You're right that the physical envelope is larger, although total volume is probably about the same because you're trading air volume against master piston volume.

Quoting Wingscrubber (Reply 28):
Bleed air take-off for a reservoir alone is very small - smaller than inlet anti ice, would have been no more difficult than a hydraulic line, plus reservoirs can sometimes be located in the engine pylon. (not sure where they are on 787)

I doubt the issue was the amount of bleed takeoff and I strongly disgree that it would be no more difficult than a hydraulic line. Hydraulic lines don't need overheat detection, and you already have a hydraulic line there from the EDP while there's no preexisting pneumatic line. The fan case already needs fire detection, so the duct for the inlet has no additional protection requirements beyond what's already there...that's not necessarily true for the strut (where the L & R reservoirs are) and definitely not true for the wing-body fairing (where the C reservoir is). To do air-over-oil on the C system would require a pneumatic run all the way to the body...there's no way the additional weight of the ducts + overheat detection, plus installation cost and increased part count, would beat out the delta for the bootstrap over the air-over-oil.

Quoting Wingscrubber (Reply 28):
Just seems puzzling when Boeing has an in-house capability for a cheaper, lighter, more reliable component but decided to farm out anyway just to be more 'bleedless'!

I think you're looking at one component when you need to look at the whole system. *If* you already had a full pneumatic system, you'd already have all the pneumatic infrastructure and an air-over-oil reservoir would win the trade. But if you start as a given that you're trying to run everything electronically and avoid bleeds, then you can't presuppose that infrastructure is in place. The air-over-oil reservoir on the C system (and the L&R to a lesser extent) would have to "pay for" the pneumatic system all by themselves, and there's no way that trade study would close.

The inlet anti-ice effectively has no cost, and probably actually still wins, because it's so close to the pneumatic source and already has overheat/fire protection. That's not true of the L/C/R hydraulic reservoirs.

Tom.

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