There is this little door in in 747-400 aircraft but what is it? It is the thing on the left of the hole...
http://news.sky.com/skynews/Home/World-News/Qantas-flight-in-emergency-landing-with-hole-in-fuselage-in-corrision-debate/Article/200807415057026?lpos=World%2BNews_4&lid=ARTICLE_15057026_Qantas%2Bflight%2Bin%2Bemergency%2Blanding%2Bwith%2Bhole%2Bin%2Bfuselage%2Bin%2Bcorrision%2Bdebate

Mate, to me that looks like the port where the fuel hose is plugged in, seems logical because of major fuel corrosion, its right next to the hole, probably leads to the fuel tank

boeing refuels farther in the wing and is not part of the aircraft pressure system. that is either a lavatory service door or an electronic service area not familiar with the 747 much but work on 707, 737, and 757 models and that door forward of the belly fairing is a lav service door

It is an access panel. l do not know what it is to, but that is what it is.

Regards,
Dan

It't the acess panel for the pack inlet door actuator. There r three of them, one on the right side & two on the left side of the plane.

http://airliners.net/photo/Singapore-Airlines/Boeing-747-412/0943035/L/&width=1200&height=810&sok=keyword_%28%27+%22nose%22_+%22gear%22%27_IN_BOOLEAN_MODE%29%29_&sort=_order_by_photo_id_DESC_&photo_nr=7&prev_id=0951762&next_id=0939517

In the picture the triangle opening is the pack inlet. There is a door that opens & closes the opening depending on how much airflow is needed. The motor & actuator to operate the door is behind that panel. Some pictures of that Qantas plane show the foward part of the opening missing.

The lav service panel is about 20 feet behind the main landing gear. One panel to access all four tanks.

Because the one that is missing is called the ''wing to body fairing then the thing next to it or the ram air inlet opening is right next to it and it has a deflector door which closes partially during t/o roll to protect from FOD. yes the guy now is correct it is the panel to access the ram air door actuator.
l think that answer your q.

Thats were the flight attendants who wo not get it on with the pilot get dumped out of,