Xms3200 From Sweden, joined Apr 2005, 101 posts, RR: 0 Posted (4 years 6 months 2 days 14 hours ago) and read 3505 times:
I was wondering how many jacks are needed to jack up a 747 (all models) off the ground for a gear swing. i know on the 737's, 3 are needed, and the nose jack is installed after all jacking operations are done, mostly as a secondary jack.
Quoting 474218 (Reply 1): I have never seen more than three! Two (wing) jacks and one (1) nose jack.
I agree that three is the usual (minimum) number of jacks used, but if it is a 747, it would be two wing jacks and a tail jack. The wing jacks are located under the forward spar of the wing centre section, thus, to maintain balance; a tail jack must be used. The 767 / 777 are similar. A nose-jack can be used if desired, but this is for additional stability only. As far as I know, Airbus is different. The main jacks are located towards the trailing edge of the wing, so a nose jack is used to maintain balance.
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 10 Reply 3, posted (4 years 6 months 2 days 10 hours ago) and read 3437 times:
Quoting JetMech (Reply 2): I agree that three is the usual (minimum) number of jacks used, but if it is a 747, it would be two wing jacks and a tail jack. The wing jacks are located under the forward spar of the wing centre section, thus, to maintain balance; a tail jack must be used. The 767 / 777 are similar. A nose-jack can be used if desired, but this is for additional stability only.
Thanks for the clarification. I thought that the tail jack on the 747 was for stabilization, not the front. You learn something new every day.
BAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0 Reply 5, posted (4 years 6 months 1 day 22 hours ago) and read 3315 times:
Did any of you ever see that programme (it was on UK terrestrial TV recently but probably came from Discovery originally) where they dismantled a 747?
It was the first one these guys had done - they were used to smaller birds - and if I remember correctly they used no less than four jacks and two fixed stands (one jack and one stand under each wing, one jack at the front, one jack at the rear). Having done this, they balanced the whole thing on stacks of railroad ties then deflated the jacks and unwound the stands and pulled them away - while running like hell.
I don't know whether they used so many beause they were being cautious or what.
On a further note, my new cat is called Jack. He's about a foot tall and weighs 12.5 pounds. I don't know how many of him you'd need to 'jack' up a 747 but I bet it's more than four.
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