Question: what is the calculation to determine TOD?

I think I read about this somewhere - good question Bill.DS CVA3339 / UKD149System: Attlon 900 McW Hamster/Gerbilized Quantum Accessible 55Gig Iodized-Encrusted Four-poster with Mega-brill Farzenhuuven http://vatsim.pilotmedia.fi/statusindicato...tor=OD1&a=a.jpg

With a Lear 24 it's 2:1, 450 to 10 thousand start down 70 miles out at 3500 fpm. Not sure for the 767, maybe a 3:1 at 2500 fpm with people in the back.

I never flew the B767, but the other aircraft I've flown we did the following.The way we used to figure it out was 3 times your altitude for a 3 to 1 glide path.If you are at FL350 you multipy 35 times 3 and get 105 miles, plus 30 extra miles and 5 for the transistion, ie level flight to descent.You want to be 30 miles from the airport at 250 knots at 10,000 feet. That is the the basic rule of thumb.And if everything worked out right, you wouldn't have to touch the throttles until some where between 2000 and 1000 feet.Remember traffic and ATC had a lot to do with it working out just right!But, if you have the luxury of flying a FMS equipped aircraft. Well, just make sure it's program correctly and you don't have to worry about a thing. Isn't the B767 PIC a thing of beauty......it's right on!

>The way we used to figure it out was 3 times your altitude for>a 3 to 1 glide path.well, this rule of thumb is definitely NOT 3 to 1 glide path ... just in case someone takes it literally.Michael J.http://www.reality-xp.com/community/nr/rsc/rxp-higher.jpg

Michael,The rule of thumb is still the same 10,000, 250 knots 30 miles out.The example being at FL350 with an average ground speed of 8 miles per minute.You would have to loose 25,000 feet. Divide 25,000 by your planned rate of descent, which was 2,500 fpm, that gives you 10. Then mutiply 10 times your ground speed, in miles per minute, and that gives you 80 miles, plus the 30 and 5 for the transistion.Start down about 115 miles from your destination.In my original post you would have started down much too early. Thanks for pointing out my mistake.ED

there is one thing I would like to add, that is the basic formula is a three to one. Take the altitude (in thousands), that you need to descend, i.e if you are at 35,000 and need go get to 10,000 you need to shed 25,000 lbs, and divide by 1000--so now you are at 25, multiply by 3 to get 75. So you have that three to one ration mentioned earlier, however there are other factors affecting planes, as different planes have different rules of thumb i wont give specifics, but weight (being over a certain weight, or under, will affect the distance of your descent), and the winds, if you have a headwind, you can start your descent later, and vice versa. The FMC has a complex computer which will calculate this point to begin the descent, if you were to do it by hand, use the 3--1 ratio and then adjust for wind and weight if you have the numbers (and correction ratios) available, if not a 3--1 works fine!

Someone told me to look at it this way.When your aircraft is heavy it will climb slower and cover more distance to reach cruise altitude, than it would when it's lighter.Same holds true for coming down. A heavy airplane will require more distance to get down than a lighter one.

"Same holds true for coming down. A heavy airplane will require more distance to get down than a lighter one."Correct, hence the water ballast we use in our gliders to cover more distance

so 3-1 + 30Excellent

or you can get that performance chart out of it's binder and look it up... (yes, they have those tables)

Hi guys, from the 767-338(ER) Performance Planning manual:Descent to 1500'M.78/300/250(assumes 250kts at 5000', 200kts by 3000')F350 at 120,000kgTime = 17minsFuel = 281kgDistance NAM = 110nmWind Correction per 10ktsHW = 3nmTW = 3nmVNAV will use 10kts/nm for decellerations at 500fpm, therefore a decelleration from 300kts to 250kts will take 5nm in nil wind, and from 250kts to 200kts will take another 5nm.My personal gates in a -300:20,000' at 80nm15,000' at 60nm10,000' at 40nm (prior to decelleration)The most critical:5,000' at 20nm (250kts)If none of this works that's what the speedbrake is for! VNAV is great as long as the correct information is loaded.Cheers.

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