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Kiwiguy
21st Nov 2006, 10:10
Hey gang, I'm not an ATPL but want to resolve a very difficult mission for a Boeing 737-200-9 from a very limited 4,490ft (1347m) runway flying 265nm. The divert airfield is en-route and almost directly under the track to final destination.
Distance from take off airport to divert field is 207nm.

According to ICAO Annex 6 (4.3.6.3) The 732 would need to lift off with fuel to reach destination+3% extra en route fuel, shoot two approaches, divert back to diversionary field (58nm) plus fuel for 30 mins at holding speed.

Question: For B737-200-9 arriving overhead destination at 37,045kg weight, what is a reasonable holding speed and what would fuel burn be for that holding speed at say 2,000ft ?

Question: Using dispatch techniques can total fuel reserves be reduced by redispatch at an en-route decision point in the air ?
For example soon after take off establishing if the final destination is open and if necessary deciding early to divert to the airport only 207nm away ?

I estimate the fuel required for the ICAO Annex 6 (4.3.6.3) plan are as follows : taxi 200kg; APU 60kg; En-route fuel 1650kg; IFR reserve 1875kg.

What I am asking is first of all have I over calculated the holding speed fuel (because I calculate that at normal 420 knot cruise) and secondly can the IFR reserve laefully be reduced to give better payload from originating runway ?

In anticipation of a drubbing thanks for your answers.:}

tailwind_on_final
22nd Nov 2006, 10:34
Kiwiguy...may not be able to give you the exact answer but did have 15 years flight planning 737-200 series aircraft for the major NZ carrier some years ago. Have dug into my personal aviation archives (don't ask why I kept these)....but may be able to fill in a few gaps.

At the time we planned to CAA rules (CASO 15) and not the annex for domestic flights. Initially we used flight planning tables but later on moved to a mainframe based system. Fuels below based on Pratt JT8D-15A.

Flight planning (assuming an alternate) consisted of

a) Pre-flight fuel (150kg - this gave 50kg for 30min of APU ops and 100kg for 5min start and taxi fuel)

b) departure fuel if required - calculated at 3min at 139kg if a 180 required after T/O

c) A-B fuel (this was from start of T/O to 1500ft overhead B)

d) 6% contigency fuel of A-B B/O

e) landing fuel - standard 135kg (3min)

f) instrument approach fuel - if straight in then 0 kg. If 'around the corner' 8min at 400kg, if straight in followed by missed approach and a second approach 15min at 770kg. if round the corner and a second go - 23min at 1170kg.

g) B-C diversion fuel

h) 3% contigency of B-C B/O

i) instrument approach fuel at C (as per 'f' above)

j) 30min holding fuel overhead alternate at 1500ft

k) where applicable a PDA allowance which was aircraft specific.

Holding speeds according to the book were 210kt clean. Don't forget the 250kt speed restriction below 10,000ft anyway. The tables I have indicated that at a ZFW of 38,000kgs then 30min hold equated to 1140kgs.

As a quick example I have an old computer fligt plan going NZWN-NZAA divert NZAA-NZHN which appears to be similar to your scenario. With a ZFW of 36300kgs at FL330 A-B calculated B/O was 44min at 1979kg (wind comp P010), B-C B/O was 17min at 887kg and alt reserve was 30min at 1146kg. Extra hold was based on 2400kg/hr.

I don't quite understand your inflight redispatch comment. You can divert to your alternate C on the way to B if you wish but this wouldn't affect your original planned fuel to go A-B. If you are planning A-C to reduce your fuel uplift that is a possibility but in the real world you might be embarrased if B suddenly opened. The other way you could get a bit more payload on departure is to use a higher flap setting eg flaps 5 or 15 instead of 1.

Cheers

rottenlungs
23rd Nov 2006, 22:09
Hey gang, I'm not an ATPL but want to resolve a very difficult mission for a Boeing 737-200-9 from a very limited 4,490ft (1347m) runway flying 265nm. The divert airfield is en-route and almost directly under the track to final destination.
Distance from take off airport to divert field is 207nm.
According to ICAO Annex 6 (4.3.6.3) The 732 would need to lift off with fuel to reach destination+3% extra en route fuel, shoot two approaches, divert back to diversionary field (58nm) plus fuel for 30 mins at holding speed.
Question: For B737-200-9 arriving overhead destination at 37,045kg weight, what is a reasonable holding speed and what would fuel burn be for that holding speed at say 2,000ft ?
Question: Using dispatch techniques can total fuel reserves be reduced by redispatch at an en-route decision point in the air ?
For example soon after take off establishing if the final destination is open and if necessary deciding early to divert to the airport only 207nm away ?
I estimate the fuel required for the ICAO Annex 6 (4.3.6.3) plan are as follows : taxi 200kg; APU 60kg; En-route fuel 1650kg; IFR reserve 1875kg.
What I am asking is first of all have I over calculated the holding speed fuel (because I calculate that at normal 420 knot cruise) and secondly can the IFR reserve laefully be reduced to give better payload from originating runway ?
In anticipation of a drubbing thanks for your answers.:}
Are you thinking of NZNS-NZAA, with a alternate of NZHN? In a 732? Even with hushkits the good people of Tahunanui and Stoke would be less than impressed, I suspect!
Cheers
James