In the picture. below the leading edge wing root you have the ram air/heat exchanger inlet, below that is the compressor intake and just forward of the gear well are the ram air/heat exchanger exhaust doors.

Florianopolis wrote:

*By the explicit text of your question, you could be describing the right engine.

Florianopolis wrote:

Assuming I'm correctly guessing what you're asking about*, it's intakes for the air conditioning and pressurization system.







viewtopic.php?t=776339

In the picture. below the leading edge wing root you have the ram air/heat exchanger inlet, below that is the compressor intake and just forward of the gear well are the ram air/heat exchanger exhaust doors.

*By the explicit text of your question, you could be describing the right engine.

putthoff wrote:

What is the object directly below the inlet? It doesn't look like two pieces with a small gap in between? On the Qatar picture you provided, it is clearly shown.

The reason the inlets stand off from the fuselage is to ensure no contaminants from the skin (e.g. de-icing fluids) can be ingested into the cabin air circuit. If a NACA duct were used, all kinds of contamination would be continuously washed into the packs whenever it flew through rain. The cleaner air feeding the cabin is one of the expected advantages of the 787 system - no potential for engine odors & contamination from a compressor bleed source.

is open when the packs are running and the airplane is on the ground and when flying at low altitudes.. They prevent objects thrown up from the runway, as well as birds from being ingested into the inlet.

you need them on the compressor inlets because the first thing you hit if you go down that duct is the spinning face of the compressor.

Florianopolis wrote:

putthoff wrote:

What is the object directly below the inlet? It doesn't look like two pieces with a small gap in between? On the Qatar picture you provided, it is clearly shown.

From an old thread: viewtopic.php?t=531465&start=110

The reason the inlets stand off from the fuselage is to ensure no contaminants from the skin (e.g. de-icing fluids) can be ingested into the cabin air circuit. If a NACA duct were used, all kinds of contamination would be continuously washed into the packs whenever it flew through rain. The cleaner air feeding the cabin is one of the expected advantages of the 787 system - no potential for engine odors & contamination from a compressor bleed source.

In re the blocker door that swings out in front of the inlet:

is open when the packs are running and the airplane is on the ground and when flying at low altitudes.. They prevent objects thrown up from the runway, as well as birds from being ingested into the inlet.

you need them on the compressor inlets because the first thing you hit if you go down that duct is the spinning face of the compressor.

putthoff wrote:

Perfect! Thanks for the pictures and explanation. I understand how it works and the purpose. However, it seems like other planes have had such inlets without this flap? DC-* nose, the 727 on the tail, etc? How was this dealt with before compared to this design? And I guess, the real question for me is the aerodynamics of this setup. It seems like it would create significant drag? It is not inset to the body like the one above?

fr8mech wrote:

putthoff wrote:

Perfect! Thanks for the pictures and explanation. I understand how it works and the purpose. However, it seems like other planes have had such inlets without this flap? DC-* nose, the 727 on the tail, etc? How was this dealt with before compared to this design? And I guess, the real question for me is the aerodynamics of this setup. It seems like it would create significant drag? It is not inset to the body like the one above?

Not sure what you mean about the B727 having it on the tail. The PACK system on the B727 is contained in the belly, with the ram air scoops straddling the centerline.

As for dealing with contaminants; that answer lies in the design of the PACK system. The aircraft that have come before, B727, B757, A300, DC10, etc. All use ram air as a cooling meduium. The air flows across the heat exchangers. Ram air is NOT used in the airframe for purposes of conditioning and pressurization, engine bleed air is. I suspect (suspect: since I have no B787 experience), with the absence of a bleed air system, ram air is used inside the cabin for pressurization and conditioning. That is why there is a contamination concern on the B787.

Each of those chin scoops have three holes. There is a large opening in the middle which takes in air for the air-to-air heat exchanger on that side. There are also two smaller holes that are the individual inlets for the turbocompressors. On the DC-8, there are a total of 4 turbocompressors.

A small amount of engine bleed air was used to spin turbo-compressors which drew in fresh air, compressed it and raised it's temperature. This air, cooled via heat exchangers and freon units, was directed to the cabin distribution system.

The Boeing 727, 737, and DC-9 generation of planes using JT8 series engines were the first to use bleed air from the engine itself, through air conditioning "packs" to directly pressurise the cabin and for temperature control.

putthoff wrote:

And I guess, the real question for me is the aerodynamics of this setup. It seems like it would create significant drag? It is not inset to the body like the one above?