HighFlyer9790 From United States of America, joined Jul 2005, 1236 posts, RR: 0 Posted (7 years 10 months 2 weeks 5 days 8 hours ago) and read 4081 times:
Does anyone know whether the triangular shaped inlets on the underbelly of all 747s serve a purpose? In the photo you can clearly see the 3 of them in front of the under carriage and by the leading edge
CitationJet From United States of America, joined Mar 2003, 2229 posts, RR: 3 Reply 1, posted (7 years 10 months 2 weeks 5 days 8 hours ago) and read 4046 times:
Based on what I learned from a previous thread, they are ram air intakes for cooling the heat exchangers for the air conditioning packs.
PhilSquares From , joined Dec 1969, posts, RR: Reply 2, posted (7 years 10 months 2 weeks 5 days 7 hours ago) and read 4005 times:
They are the inlets for the air conditioning packs. If you look further aft, to about 3 feet prior to the body gear doors you will see the exit doors, they're louvered and will automatically position, just like the inlet doors.
FlyinTLow From Germany, joined Oct 2004, 501 posts, RR: 0 Reply 4, posted (7 years 10 months 2 weeks 4 days 9 hours ago) and read 3734 times:
Yes, air inlets for the a/c. And as mentioned before the outlets are about 10 feet behind that (rather brown in that picture). A very good spot to stand about another 10 feet down the fuselage in the winter when it is cold, cause a lot of hot air comes out there. Not too fancy if it's hot on the tarmac already
Ikramerica From United States of America, joined May 2005, 21026 posts, RR: 60 Reply 8, posted (7 years 10 months 2 weeks 4 days 4 hours ago) and read 3385 times:
Yeah, A and B like to design lots of useless holes into their fuselages. Makes for a greater engineering challenge. And if you don't challenge the engineers, how will they ever learn?
Of all the things to worry about... the Wookie has no pants.
OzLAME From Australia, joined Feb 2005, 338 posts, RR: 0 Reply 9, posted (7 years 10 months 2 weeks 3 days 21 hours ago) and read 3215 times:
These inlets are not quite triangular, they are more a sort of teardrop shape that has the bottom cut off. The generic name for inlets of this shape is NACA Duct, after the National Advisory Commitee for Aeronautics (forerunner to NASA) that came up with the shape. The shape means that drag associated with the opening is minimal; these ducts can be very large, as on the 747, or very small, e.g. an inlet on an engine nacelle. They can be found on all sorts of different aircraft; you can see a NACA Duct on the a/c shown below, forward of the door and below the windscreen.
Areopagus From United States of America, joined Sep 2001, 1356 posts, RR: 1 Reply 11, posted (7 years 10 months 2 weeks 3 days 17 hours ago) and read 2929 times:
The NACA duct was used for the engine air inlets for the North American Aviation F-93, a development of the F-86. See, for example, Wikipedia, but note that their overhead view shows a more conventional inlet that was tried after the NACA inlet turned out not to supply enough air for the engine.
Starlionblue From Hong Kong, joined Feb 2004, 15870 posts, RR: 66 Reply 12, posted (7 years 10 months 2 weeks 3 days 13 hours ago) and read 2770 times:
Quoting CX flyboy (Reply 10): They serve a purpose? I thought they looked pretty. Is that not a good enough reason these days?
Only if the plane has a nice livery and is washed regularly
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
AeroWeanie From United States of America, joined Dec 2004, 1600 posts, RR: 52 Reply 15, posted (7 years 10 months 2 weeks 6 hours ago) and read 2355 times:
Quoting OzLAME (Reply 9): These inlets are not quite triangular, they are more a sort of teardrop shape that has the bottom cut off. The generic name for inlets of this shape is NACA Duct, after the National Advisory Commitee for Aeronautics (forerunner to NASA) that came up with the shape.
They are NACA Inlets, not NACA ducts. Ducts carry air from one place to another. Inlets allow air to flow into a body. They are unique inlets in that they are semi-submerged and still have reasonable, though not great, pressure recovery.
Abhi From Canada, joined Oct 2001, 54 posts, RR: 0 Reply 22, posted (7 years 10 months 1 week 4 days 2 hours ago) and read 2006 times:
You can feel the heat from those outlets when you're working the loader in the aft belly. It feels great in the winter but in the summer I tried working the front belly as much as possible.
Funny thing happened to one of the guys one day. He was bringing a stroller from the gate to put in the bulk load and his hat got sucked into the inlet. This happened on the 340 where you can actually see inside the inlet. They're too high on the 747.
Maintenance had to remove the entire panel to get that hat out. They were quick though: delayed the flight only fifteen minutes.
Sponsor Message: 
From United States of America, joined Jul 2005, 1236 posts, 
From , joined Dec 1969, posts, 
From New Zealand, joined Sep 2000, 4502 posts, 
From Germany, joined Oct 2004, 501 posts, 
From India, joined Jan 2001, 31201 posts, 
From Hong Kong, joined Feb 2004, 15870 posts, 
Sorry your title gave me a laugh but it was a good question.
From Australia, joined Feb 2005, 338 posts, 
These must have opened by accident.
From Canada, joined Oct 2001, 54 posts, 
Sponsor Message: 
Printer friendly format
