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Impact Of Gradient On Takeoff And Landing B777  
User currently offlinempvincent From New Zealand, joined May 2011, 10 posts, RR: 0
Posted (2 years 12 months 3 days 19 hours ago) and read 4126 times:

Hi there

Does anyone have a rough equation I could use to estimate the improvement in takeoff payload of a b777 200er off a runway that is descending and ascending by a certain gradient? I was thinking if I used the Boeing curves from airport manual to work out max tow and then used some relationship between gradient acceleration and velocity to work out how much more speed I would have with a gradient and then back calc to give implied payload?

Unless someone has some take off curves for the 200er varying by gradient?

Thanks.

2 replies: All unread, jump to last
 
User currently offlinemandala499 From Indonesia, joined Aug 2001, 6872 posts, RR: 75
Reply 1, posted (2 years 12 months 2 days 7 hours ago) and read 3834 times:

Quoting mpvincent (Thread starter):
I was thinking if I used the Boeing curves from airport manual to work out max tow and then used some relationship between gradient acceleration and velocity to work out how much more speed I would have with a gradient and then back calc to give implied payload?

Hmmm... that would be a bit more difficult than just looking at some dispatch tables from the FCOM.
Get the runway length, then put in gradient correction and wind correction to get the "corrected runway length", pull that runway length onto a take off vs TOW table and get the max number for that corrected length.
When we're talking about runway length, the TOW is primary weight limit... then, you can calculate the payload from that (if you know how much fuel is on board).

Quoting mpvincent (Thread starter):
Unless someone has some take off curves for the 200er varying by gradient?

You're in luck in that it's a sunday today and I just did this for fun (    ), so take it as is and no implications that it is correct (but I did take the numbers from a 777-200ER FCOM performance dispatch section).
http://www.globalsim.web.id/publicservice/777GradientCorrectionNoWindTakeOff.jpg
Gradients are in percent... + means upslope, - means downslope.

Enjoy,

Mandala499



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlinempvincent From New Zealand, joined May 2011, 10 posts, RR: 0
Reply 2, posted (2 years 11 months 4 weeks 1 day 22 hours ago) and read 3538 times:

Thanks very much.

Cheers


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