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Applying Bleedless Engines To Current Aircraft  
User currently offlineRoberta From , joined Dec 1969, posts, RR:
Posted (12 years 4 weeks 1 day 1 hour ago) and read 2376 times:

How easy would it be to put bleedless engines on current aircraft such as the A330 and 747. Would the whole wing design need to change or can you simply modify an existing model to fit bleedless engines.

9 replies: All unread, jump to last
User currently offlineGreasespot From Canada, joined Apr 2004, 3104 posts, RR: 19
Reply 1, posted (12 years 4 weeks 23 hours ago) and read 2276 times:

It would be very hard. First you would need to modify the electrical system because all the stuff that used bleed air will now require power to run. The Aircond packs which use bleed air to pressurize and heat and cool the cabin would have to be modified. All the anti ice systems that use bleed air would have to be changed.

I am not saying that it cannot be done just that it would be expensive.


Sometimes all you can do is look them in the eye and ask " how much did your mom drink when she was pregnant with you?"
User currently offlineAV757 From Colombia, joined Apr 2004, 667 posts, RR: 5
Reply 2, posted (12 years 4 weeks 18 hours ago) and read 2154 times:
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Just as Greasespot said in the above posted message, all those modifications needed to install, adapt, fit and redesign the new systems to the aircraft itself will require mayor changes; both structurally and to the internal systems themselves having a very high cost to implement and maybe a long downtime of the airplane.

And most important of all, who is going to assume the high costs of recertification of the aircraft so it can get its new airworthiness certificate once more after all the changes are made so it can be operated once more?.

It seems to me that it will just be plain simpler and cheaper to buy the new airplane with its new systems and technology built in than to retrofit existing airplanes.


User currently offlineRoberta From , joined Dec 1969, posts, RR:
Reply 3, posted (12 years 4 weeks 18 hours ago) and read 2128 times:

I didnt mean converting an actual individual aircraft into a bleedless engine user. I was thinking more of making an NG model which uses bleedless engines.

I probably should have explained that a bit more clearly

User currently offlineBoingGoingGone From , joined Dec 1969, posts, RR:
Reply 4, posted (12 years 4 weeks 18 hours ago) and read 2125 times:

Just for a starter, although a different system. Dornier was curious about Honeywell Primus Epic for the 328/428 in lieu of Primus 2000 to simplify avionics when the 328/428/528/728/928 family was in the works.

Certification price tag... $23 Million, for a simple swap of a box, cards, wiring and proving flights.

It would probably be cheaper to design and build a new bird. Especially with todays computer modeling.

User currently offlineAV757 From Colombia, joined Apr 2004, 667 posts, RR: 5
Reply 5, posted (12 years 4 weeks 17 hours ago) and read 2073 times:
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You bet, it is simply much better to desing and build a new airplane with all the new advancements in aerodynamics and technology from scratch than to try to stretch the useful life of a proven concept.

An example would be the venerable DC-9 series that Douglas and later on McDonnell Douglas tried to advance without any major changes; only streching the fuselage and applying newer generation electronics and powerplants. It is not a bad idea in principle, but everything has its limits in time; and you can´t over stretch those.

User currently offlineDfwRevolution From United States of America, joined Jan 2010, 1224 posts, RR: 51
Reply 6, posted (12 years 4 weeks 17 hours ago) and read 2037 times:

Would the whole wing design need to change or can you simply modify an existing model to fit bleedless engines.

From what I understand, the wing profile could remain the same but all wing systems must be redesigned. Meaning all the fun stuff Greassepot mentioned.

If Airbus wanted to update the A330, or Boeing the 747, it would require a signifcant investment. An analogy that comes to mind was Boeing's choice to not implement FBW in the 737NG- Boeing estimated it would cost hundreds of millions of dollars to add FBW, it would hinder reliability, and only for a marginal performance gain so they stayed with traditional controls.

User currently offlineAvObserver From United States of America, joined Apr 2002, 2485 posts, RR: 8
Reply 7, posted (12 years 4 weeks 16 hours ago) and read 1960 times:

Recently, Boeing was talking about using bleed-air versions of 7E7 engines in the proposed 747 Advanced, scotching our hopes the new version would have major systems revisions. It's all about costs, of course and to so radically change the 747 would significantly increase its' price, something Boeing can't allow in marketing a largely legacy design. Apparently the difference in economics between the bleedless and bleed-air engine versions is too small to justify revamping 747 systems for it.

User currently offlineSAA-SAL From Belgium, joined Nov 2000, 356 posts, RR: 3
Reply 8, posted (12 years 4 weeks 5 hours ago) and read 1863 times:

Excuse my ignorance but I'm not familiar with the term bleed-air and bleedless.
Can someone please explain what the difference is

SAA B747 SP, Luxavia B747 SP
User currently offlineSabenapilot From Belgium, joined Feb 2000, 2748 posts, RR: 46
Reply 9, posted (12 years 4 weeks 4 hours ago) and read 1797 times:


A very brief explanation of this new 'hype' of bleedless engines.

An engine basically has 2 tasks:
The first is the most obvious one; i.e. to push the plane forward by converting fuel into thrust,
Secondly, an engine also supplies many vital aircraft systems with hydraulic power, air pressure, air conditioning etc...
All these secondary consumers of power are called engine bleed, since they require fuel to be burned without any propulsion resulting from that, which might be seen as a waste (although you need the systems which are dependent on this 'waste')

The idea behind this bleedless concept (which is already as old as the jet engine itself BTW) is to find alternative ways of supplying these aircraft systems so as to reduce the fuel flow of the engine. The alternative seems to be found by having these systems supplied by the electrical system rather than by engine bleed. Electricity, which also has to be generated by the engine, thus also constitutes a kind of indirect bleed BTW.

Therefore, bleedless in a wrong name, as the aircraft becomes more dependent on electrical power, which is also made by the engines (also a kind of bleed) and besides the engines will still need to supply bleed air, for instance for the air conditioning system.

Over the past decades many theoretical experiments have been done to see if a shift from direct bleed as it is most commonly used now to a less bleed dependent engine would make any sense and the conclusions then were that it is technically possible and is will indeed reduce the FF of the engine by a few percent, but that it makes the plane more complicated to maintain, less redundant in operations and requires more maintenance. Back then, it was deemed not a really good idea.

However, it seems people in aviation research and design are convinced that with today's technology they can make this concept work cheaper than the current bleed engines, but that remains to be seen.

Anyway, what we will most probably see is that engine manufacturers will (re)design their engines in such a way they can be installed both on airplanes requiring bleed as well as on future bleedless planes.... The later will benefit from all improvements, the first one will also, except from the gains made through the bleedless concept which are only part of the overall improvements expected on new engines.

[Edited 2004-04-29 12:57:45]

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