B737 Descent profile calculation.
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B737 Descent profile calculation.
Can someone please assist wrt working out basic TOD profiles, factoring in wind component, delta weight, deceletation distance as well as normal and high speed descents.
Thanks in advance!!!
Thanks in advance!!!
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250 kts 3 NM per 1000 Feet
280 kts 2.5 NM per 1000 Feet
320 kts 2 NM per 1000 Feet
1 NM per 10 kts wind ( 50 kt tailwind add 5 nm, 50 kt headwind subtract 5 miles)
Slowing add 1 NM for every 10 kts. (Slowing from 320 kts to 250 kts = 7NM)
280 kts 2.5 NM per 1000 Feet
320 kts 2 NM per 1000 Feet
1 NM per 10 kts wind ( 50 kt tailwind add 5 nm, 50 kt headwind subtract 5 miles)
Slowing add 1 NM for every 10 kts. (Slowing from 320 kts to 250 kts = 7NM)
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Basic TOD point still works with 3 x Altitude = Distance to start TOD from the destination. You may begin descent slightly early but this allows for the slow down to 250kts and then back to flap / gear schedules. Also allows use of partial thrust in descent for gradient changes. Using speed brake latter in descent to fix speed/height problem is more inefficient than a slightly early descent point. Aim for 5000ft @20nm to run at 250kts. Next gate 3000ft @10nm 180kts.
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35NM 10000' 250kts
20 NM 6000' clean speed
10 NM 3000' Flaps 5 speed
That's the conservative gate figures as per my bosses. If you're asking for a sim check, I'd stick to that to keep things nice and smooth.
In real life, what mangatete gave is more like it.
P
20 NM 6000' clean speed
10 NM 3000' Flaps 5 speed
That's the conservative gate figures as per my bosses. If you're asking for a sim check, I'd stick to that to keep things nice and smooth.
In real life, what mangatete gave is more like it.
P
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Weight
Weight is a factor also. A much heavier plane will glide further.
I think it's very important - as was mentioned - to go through the mental gymnastics of working out reasonable "how goes it" gates for every descent. You can work out the descent rate to a gnat's ass - and be totally surprised when you get to the bottom of a descent path, if you didn't check a couple of times along the way. You can make very fuel efficient adjustments on the way down - and avoid that - "Uh - I don't think we can make this next altitude", or drivin' it in at 3000' for 50 miles.
If you do the math consistently, it becomes second nature.
That being said it is also important to find out the likely descent rates for your A/C as you are doing.
LL
LL
I think it's very important - as was mentioned - to go through the mental gymnastics of working out reasonable "how goes it" gates for every descent. You can work out the descent rate to a gnat's ass - and be totally surprised when you get to the bottom of a descent path, if you didn't check a couple of times along the way. You can make very fuel efficient adjustments on the way down - and avoid that - "Uh - I don't think we can make this next altitude", or drivin' it in at 3000' for 50 miles.
If you do the math consistently, it becomes second nature.
That being said it is also important to find out the likely descent rates for your A/C as you are doing.
LL
LL
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Thanks for the info to all!!!.
Have very recently converted onto B733/4. Am still trying to find my way round both types. Have a similar 3 deg slope system working from the bottom up, depending on the speed, weight, and wind I then apply corrections and it works pretty well, until ATC intervene. Then only speed intervention assists in mantaining a reasonable descent without unnecessary thrust application.
Have very recently converted onto B733/4. Am still trying to find my way round both types. Have a similar 3 deg slope system working from the bottom up, depending on the speed, weight, and wind I then apply corrections and it works pretty well, until ATC intervene. Then only speed intervention assists in mantaining a reasonable descent without unnecessary thrust application.
