HighFlyer9790 From United States of America, joined Jul 2005, 1241 posts, RR: 0 Posted (10 years 10 months 3 weeks 2 days 19 hours ago) and read 6537 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
PhilSquares From , joined Dec 1969, posts, RR:
Reply 2, posted (10 years 10 months 3 weeks 2 days 18 hours ago) and read 6461 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, 542 posts, RR: 0
Reply 4, posted (10 years 10 months 3 weeks 1 day 20 hours ago) and read 6190 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
OzLAME From Australia, joined Feb 2005, 338 posts, RR: 0
Reply 9, posted (10 years 10 months 3 weeks 1 day 8 hours ago) and read 5671 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, 1380 posts, RR: 1
Reply 11, posted (10 years 10 months 3 weeks 1 day 4 hours ago) and read 5385 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.
AeroWeanie From United States of America, joined Dec 2004, 1612 posts, RR: 51
Reply 15, posted (10 years 10 months 2 weeks 4 days 17 hours ago) and read 4811 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 (10 years 10 months 2 weeks 1 day 13 hours ago) and read 4462 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.