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I was not surprised this article buries the 787 deep inside where no one will read it. Honestly the bleedless air system of the 787 is one of the things that ma

I was not surprised this article buries the 787 deep inside where no one will read it. Honestly the bleedless air system of the 787 is one of the things that makes me enjoy flying it.

Aeolun 6y ago
It’s weird they do that. It’s one of the largest red flags that indicate it actually is a problem.
- ashtonkem 6y ago
  Exactly! Boeing can't claim that engine bleed air is clean on one hand, and tout that a bleed-less air system improves air quality. It's either one, or the other, not both.
  - rowanG077 6y ago
    Of course they can. Air quality is not binary. Air can be clean yet it could also be cleaner.
    - waiseristy 6y ago
      I don't think Boeings primary reason for switching to no-bleed air was air quality reasons anyway. Electrically powered air is way lighter, more reliable, efficient, etc...
      - benhurmarcel 6y ago
        It's not that straightforward. I work in that domain and the general consensus is that the 787 system is about as efficient as a conventional bleed system would be. It doesn't offer any significant efficiency advantage. The mechanical power offtake affects the engine fuel consumption less than the equivalent bleed offtake, but on the other hand their system is significantly heavier, and creates a lot more drag. Basically, the engine compressor is the best compressor you will find aboard. To provide air supply you need pressurized air. So it makes sense to directly take the compressed air you already have with that excellent compressor. With their bleedless system they add 2 large extra electrical compressors, and 2 large extra air intakes (to take the air to be compressed). So of course there are advantages to the electrical route, but efficiency isn't a given.
testfoobar 6y ago
Not entirely rational - but I still haven't flown on a 787. Long term behavior of composite construction concerns me.

I was not surprised this article buries the 787 deep inside where no one will read it. Honestly the bleedless air system of the 787 is one of the things that makes me enjoy flying it.

Aeolun 6y ago

It’s weird they do that. It’s one of the largest red flags that indicate it actually is a problem.

ashtonkem 6y ago
Exactly! Boeing can't claim that engine bleed air is clean on one hand, and tout that a bleed-less air system improves air quality. It's either one, or the other, not both.
- rowanG077 6y ago
  Of course they can. Air quality is not binary. Air can be clean yet it could also be cleaner.
  - waiseristy 6y ago
    I don't think Boeings primary reason for switching to no-bleed air was air quality reasons anyway. Electrically powered air is way lighter, more reliable, efficient, etc...
    - benhurmarcel 6y ago
      It's not that straightforward. I work in that domain and the general consensus is that the 787 system is about as efficient as a conventional bleed system would be. It doesn't offer any significant efficiency advantage. The mechanical power offtake affects the engine fuel consumption less than the equivalent bleed offtake, but on the other hand their system is significantly heavier, and creates a lot more drag. Basically, the engine compressor is the best compressor you will find aboard. To provide air supply you need pressurized air. So it makes sense to directly take the compressed air you already have with that excellent compressor. With their bleedless system they add 2 large extra electrical compressors, and 2 large extra air intakes (to take the air to be compressed). So of course there are advantages to the electrical route, but efficiency isn't a given.

testfoobar 6y ago

Not entirely rational - but I still haven't flown on a 787. Long term behavior of composite construction concerns me.