Jesse From , joined Dec 1969, posts, RR: Posted (17 years 1 week 4 hours ago) and read 810 times:
How many g's can a 747-400 take before things start breaking? I think it's around 3.5 or 4 but I don't know for sure. I'm interested in emergency ballistic parasails for the 747 and I need to know what the airframe can handle so the parachutes' opening forces don't rip the plane apart.
Iainhol From , joined Dec 1969, posts, RR:
Reply 1, posted (17 years 1 week 3 hours ago) and read 810 times:
What is recommend and waht they can do are different. We can not turn more then 30 degrees and at sixty you are pushing 2 g's so not that many. On the 777 it will not let you turn more 30 degrees. Also have you seen the movie of the 777 wing test it flexed up 55 degrees if they were doing that in flight that would be a bunch of g's 4 or 5.
BryanG From United States of America, joined May 1999, 446 posts, RR: 0
Reply 2, posted (17 years 1 week ago) and read 813 times:
Fortunately, no one knows the answer to that question, but one flight almost found out:
In 1985 a China Airlines 747SP was 41,000 above the Pacific when one of the engines wound down and flamed out. The other three kept going, and that produced an incredible yaw force on the plane. The autopilot was left on, so its trim held the plane straight and level. When the pilot flicked the autopilot off, the trim relaxed and in a couple seconds the plane was on its back in a full-power dive to the ground. The rate was about 16,000 feet per minute. It barrel rolled for 32,000 feet, and lost big chunks of the tail and elevators, APU, and the antennas, but the plane recovered and landed OK. The max 'g' peaked at +5.5 in the dive, or about twice as much as the design limit. The normal tolerances for a 747 are about +2.5 and -1.0
A similar incident also happened to a 727 after an inadvertant unilateral flap deployment. This plane barrel rolled from 41,000 down to 5,000 feet at about 46,000 feet per minute. The rate peaked for a second at 76,000 feet per minute, and a bunch of passengers in the cabin blacked out because of the 'g' pressure in the dive. The airframe was pushed past 6 'g', but also held together for a safe landing.