787 "teething troubles" statistics?

[MrSnuggles]

Where do people get this stuff from?

AERO - 787 No-Bleed Systems

[One Outsider]

Which have absolutely nothing to do with "Many of the battery troubles are because of the new bleedless design that affects battery performance" which is nonsense. It's one thing to link to something on the internet, it's quite another to understand it.

[Bye]

oddly enough the so called "no Bleed" system would mean that you can't run close enough to the surge line to be efficient and when the VFSG comes on load the engine would be prone to surge especially if accelerating N2 or N3.

so of course to counter this and allow operation a bit closer to the surge line, the Trent 1000 "no Bleed" engine has 5 bleed valves, 3 at IP8 and 2 at HP3.

these bleed valves are scheduled by N2, N3 rpm, T24 IP inlet Temp, and VFSG load, and dump into the by-pass duct rather than the cabin.

[TURIN]

Almost all jet engines have bleed control valves. Nothing to do with it being a bleedless aircraft design.

There is one bleed on the engine for the engine inlet cowl anti-ice system by the way.

[Bye]

Almost all jet engines have bleed control valves. Nothing to do with it being a bleedless aircraft design.

then why claim its a bleedless engine in the first place

it has everything to do with the claim of being a bleedless "engine" if you understand the claims made for why its bleedless.

There is one bleed on the engine for the engine inlet cowl anti-ice system by the way

the HP3 take off butterfly valve for anti-ice is not considered a bleed, it is a deliberate take off, selectable by the pilot of hot air, there are many such take offs of air through the gas path for various uses non of which are considered or even described in the drawings as "bleeds" even though the gas ends up overboard if used.

you may call it a bleed, that is your right but it is not a bleed.

bleeds are generally used to described un-intentional or un-wanted loss of gas flow, removing the gas from the 5 bleeds is not for use but is to manage the surge risk and is thus un-wanted as when in operation they lower the efficiency of the compressor and thus increase the fuel consumption.

on the T1000 as we now waste that energy dumped over board, instead of using it to pressurise the cabin, that energy has to come from somewhere else, that being the VFSG. fortunately in the cruise phase the bleeds will stay shut and the engine is operating at optimum for the phase for the longest time.

[DaveReidUK]

you may call it a bleed, that is your right but it is not a bleed

Engine air take-off for ECS and ice protection has been called bleed air by the industry for as long as I can remember.

[Bye]

The diagram you show is not a Trent 1000 so is of course irrelavant to the thread.

The diagram you show has the anti-ice taken off the bleed so is correctly known as bleed air.

The TRENT 1000 does not use BLEED air for the anti-ice.

The reason is that to improve cruise efficiency of the compressor, the bleed valves remain closed. this means there is no air available from the bleeds for anti-ice.

So we put a separate air off take at HP3 on the compressor to feed the anti-air.

Look at your own diagram and then you might understand how the off take on it is from a bleed source and is correctly called bleed air.

But the T1000 does NOT use bleed air for anti-ice and is not the same as the diagram you produce.

[DaveReidUK]

But the T1000 does NOT use bleed air for anti-ice and is not the same as the diagram you produce.

You'd better tell EASA and the FAA, then.

The Trent 1000 Type Certificate specifies the "Maximum Permissible Air Bleed Extraction" (for engine cowl anti-ice), expressed as the maximum % of core mass air flow for various TET values.

[Bye]

it actually states.


10. Maximum Permissible Air Bleed Extraction:

The Trent 1000 does NOT supply compressor air for airframe ventilation (Cabin Bleed), but does supply
compressor air for the purpose of preventing ice build-up on the engine nacelle (Cowl Thermal Anti-Ice
(CTAI)).

The nacelle thermal anti-icing flow demand is modulated via a regulating valve.

item 10 is a category on the certificate, the statement below clearly says it does not supply cabin bleed, and clearly calls it compressor air, NOT BLEED.

and the following table is just a generic table that is common to the certificates allowing people like yourself to have a comparison to older engines.

Cowl Thermal Anti-Icing Bleed Off takes for Normal and Abnormal operation

Engine Power Setting
TET (K)
Maximum Cowl Thermal Anti Ice Flow
% Core Mass Flow (W26)
Idle to 1430 2.67
1430 to 1785 2.67 to 1.25 varying linearly
1785 to 1820 1.25 to 0.54 varying linearly
1820 and above 0.54

NB “W26” represents the air mass flow through the core of the engine.

Boeing also call it a bleed and many other people will also call it a bleed, but the manufacturer of that system does NOT.

In the industry we do not call modulated air off takes a bleed anymore, there are reasons for this, a lot of money was spent on marketing the "bleedless" engine and it will take time to change the industry to get to grips with it.

alongside the marketing there are other reasons.

as i said before if you want to call it a bleed, go ahead its up to you. we can only try to educate people as to the correct nomenclature and hope the people who resist change will eventually get on board with the correct terminology. and for the record i can point to a lot of variations on certificates to manufacturers terminology, like calling a battery a battery when it is not a battery at all, but there you go.

We have tried to differentiate the T1000 system by not calling it a bleed anymore.

on the T1000 it is modulated flow on demand, where as bleed flow is not, its waste air flow to avoid surge.

[MrSnuggles]

It's one thing to link to something on the internet, it's quite another to understand it.

I admit, my choice of words may have been inappropriate to a native English speaker.

Still:

Bleedless engines ==> more battery power needed to do stuff*.

I hope that is clear enough.


*"Stuff" that was previously done by using bleed air in some form. Some of these stuffs are mentioned very well in my link. But OK, among them are cabin pressurisation, some cockpit instruments, some hydraulic pumps and de-icing systems.

I will now leave this discussion to the more fluent English persons.

[DaveReidUK]

Boeing also call it a bleed and many other people will also call it a bleed

Thank you, my point precisely.

As the Bard said, "a rose by any other name..."

[Bye]

Engine air take-off for ECS and ice protection has been called bleed air by the industry for as long as I can remember.

no that was your point i believe, which was factually innacurate in that engine cowl de-ice air off take on the Trent 1000 is not called a bleed by the manufacturer, but is mistakenly called so in a couple of places including a Boeing article and by you.

which you obviously now agree with by your bard quote.

As the Bard said, "a rose by any other name..."

Juliet argues that the names of things do not matter, only what things "are"

and what things are, are not a bleed, but as i said people can call it what they like, but "are" not a bleed.

[TURIN]

Bye,
I think you are in a minority of one there.
Whether it is a surge bleed valve or a systems bleed valve is irrelevant.
The anti ice bleed valve is selectable in exactly the same way as the HP bleed valve, or modulating pressure control valve.
Yes, the Trent 1000 is more efficient because it does not use bleeds for air con or running hydraulic pumps, but it still has surge bleed control valves like any other engine.

Mr Snuggles.
The 787 battery does not replace any of the pneumatic systems previously powered by bleebyd air from the engines.
The APU battery will start the APU and run some external lights during battery only towing.
The main battery powers essentials instruments, some external lights (during towing) and emergency brakes.

[Bye]

Whether it is a surge bleed valve or a systems bleed valve is irrelevant.

very wrong indeed.

The anti ice bleed valve is selectable in exactly the same way as the HP bleed valve

wrong again, the HP anti surge valves are NOT pilot selectable, the anti ice air take off is. and is available continuously for selection.

Yes, the Trent 1000 is more efficient because it does not use bleeds for air con or running hydraulic pumps

wrong again, the Trent 1000 is more efficient for other reasons, the transfer of HVAC from the cabin bleed does not use less fuel, it uses more for the same amount of cooling as the generating system and HVAC compressors are less efficient as a system, what it does allow though is better modulation of the HVAC system when less people are on board or less cooling is required.

Again with the hydraulic its the overall system that allows more efficient use, but for the same energy consumption the engine uses more fuel.

also as the radial shaft now has to carry over 500 HP it is less efficient as a power take off system.

but it still has surge bleed control valves like any other engine.

which is exactly what i said in my first post on this subject

and emergency brakes.

what emergency brakes ?

the brakes are electrically actuated and can be operated by battery power alone, i'm not aware of any emergency brakes being fitted to the aircraft.

but then i'm in a minority of one

[DaveReidUK]

but then i'm in a minority of one

Don't worry about it, we realised that more than a year ago when you spent several days here on PPRuNe trying unsuccessfully to convince the world that momentum was a force.

http://www.pprune.org/tech-log/501013-why-heavier-aircrafts-take-longer-slow-down-air-5.html#post7538238

[TURIN]

Troll alert!
Back under your bridge Bye.

Its a shame because there are genuine aircraft enthusiasts who lurk here and enjoy the "facts".
But every now and again, a "Bye" turns up.

Sad.

Seeya.

[Bye]

funny how people like you and William resort to insults when you are wrong.

shows us everything we need to know about you.

GB

[TURIN]

Oh for crying out loud!
You don't know the difference between a surge bleed control valve and a HP bleed valve.
You claim that because the T1000 uses bleedless architecture, it needs surge bleed control valves. Utterly bogus. All engines have surge bleed control valves. The 787 is different, the Trent 1000 & GENx have no utility bleeds except the cowl anti ice. But they still have surge bleed control valves (and VIGV/VSBs but that's another story).
I did not insult you, I call you a troll because you display the attributes of a sciolist in your argument.



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[TURIN]

Originally Posted by Bye

Quote:

Whether it is a surge bleed valve or a systems bleed valve is irrelevant.

very wrong indeed.

Quote:

The anti ice bleed valve is selectable in exactly the same way as the HP bleed valve

wrong again, the HP anti surge valves are NOT pilot selectable, the anti ice air take off is. and is available continuously for selection.



Quote:

and emergency brakes.

what emergency brakes ?

the brakes are electrically actuated and can be operated by battery power alone, i'm not aware of any emergency brakes being fitted to the aircraft.

but then i'm in a minority of one

Here, you are confusing the surge bleed control valves (which are controlled automatically and scheduled by the ECS) and a HP valve which is selected by cockpit switches. The 787s do NOT have HP VALVES.

Emergency brakes POWER is from the battery. Jeesus what a pedant!



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