Pre take off calculations
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Joined: Jul 2002
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From: Dunnunda
Pre take off calculations
Trying to pass an exam... ATIS broadcasts an 18kt headwind
The wind components given to establish "MAX BRAKE RELEASE WEIGHT" are NIL, 10HW, 20HW, 30HW.
I understand that I should use the lesser HW which in this case is 10HW but what do I use for the VI Corrections?
In the PTOC that we use under V1 CORRECTIONS it states +1/15kts HW.
Do I use the 10kt HW and not apply a correction to VI or do I apply the +1kt correction due to 18kts being broadcast on the ATIS?
The wind components given to establish "MAX BRAKE RELEASE WEIGHT" are NIL, 10HW, 20HW, 30HW.
I understand that I should use the lesser HW which in this case is 10HW but what do I use for the VI Corrections?
In the PTOC that we use under V1 CORRECTIONS it states +1/15kts HW.
Do I use the 10kt HW and not apply a correction to VI or do I apply the +1kt correction due to 18kts being broadcast on the ATIS?
Joined: Jun 2004
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From: Australia
If interpolation is forbidden (which the multiple choice answer options seem to indicate)...................
Calculate MBRW from the most conservative wind component, i.e. 10 Kt Headwind,
Calculate V Speeds according to the environmental conditions and the actual weight, i.e. 15 Kt Headwind.
Boeing's recommendation for most B777 operations -
(1) Obtain the RTOW from the Airport Analysis according to the most conservative wind,
(2) Enter the actual wind into the FMC, (which makes the V1 allowances that you allude to), and use the FMC speeds.
Airline policy may vary.
Regards,
Old Smokey
Calculate MBRW from the most conservative wind component, i.e. 10 Kt Headwind,
Calculate V Speeds according to the environmental conditions and the actual weight, i.e. 15 Kt Headwind.
Boeing's recommendation for most B777 operations -
(1) Obtain the RTOW from the Airport Analysis according to the most conservative wind,
(2) Enter the actual wind into the FMC, (which makes the V1 allowances that you allude to), and use the FMC speeds.
Airline policy may vary.
Regards,
Old Smokey
Joined: Sep 1999
Posts: 5,552
Likes: 25
From: ME
Use the 10kt column for the weight, apply 2/3 of the 1kt V1 correction and round down.
We use Zero Wind charts with the use of a headwind weight correction subject to Captains discretion, unless of course its and Airbus
Old Smokey, interesting to see that you use FMC speeds, do you also carry paper v-speed tables for calculations beyond the limits of the FMC? (ie, CDL corrections?
Mutt......
We use Zero Wind charts with the use of a headwind weight correction subject to Captains discretion, unless of course its and Airbus
Old Smokey, interesting to see that you use FMC speeds, do you also carry paper v-speed tables for calculations beyond the limits of the FMC? (ie, CDL corrections?
Mutt......
Joined: Jun 2004
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From: Australia
Hi Mutt,
Yes we do use FMC V speeds during normal Dry Runway Balanced Field operations. Wet runways, unbalanced field (not too many), Assumed Temperature above the environmental limit, and CDL items come from paper V-speed tables.
Like yourself, it's normal policy to use zero wind with the Captain's discretion for use of any Headwind component. Naturally, the worst Tailwind MUST be considered.
FMC speed use is limited to agreement within 3 knots of the Airport Analysis speeds. I don't like it at all, but accept that some (not all) of the possible 3 knots arises from establishing RTOW from "worst case" data blocks in the Airport Analysis, and using actual environmental conditions within the FMC. Also a bit more because the ATOW is rarely right on the Airport Analysis data block limit, but the problem is, "OK, I can understand where this possible 3 knot differential is coming from, but I can't verify any of it in the cockpit"
Then we can get down to obstacle effect upon EOL whilst ADSR is not affected, or interpolation between data sets when multiple obstacles exist.
I don't do the Performance Engineering for my "own" aircraft, the B777. I do it for other aircraft. For the aircraft for which I'm responsible, most of the work is unbalanced field, and paper V-Speeds and RTOWs are available for all operations, Dry, Wet, Balanced/Unbalanced, Anti-Skid Inop, Reverse Inop etc., it means a few more kilos of paper to carry, but it puts me well inside the comfort zone. For these aircraft I've written into policy that for Dry, Balanced, no CDL operations, acceptance of FMC speeds within 1 knot is acceptable. That's because the paper speeds are calculated for QNH=1013, whilst the environmental conditions entered into the FMC might just nudge the speeds by 1 knot. Also exact halves are rounded differently for V1 and Vr/V2, e.g. V1=140.5 is rounded down to 140, Vr or V2=140.5 is rounded up to 141.
How is your new South American aircraft? T'would be interesting to see the manner of data preparation and provision from south of the Panama.
Regards,
Old Smokey
Yes we do use FMC V speeds during normal Dry Runway Balanced Field operations. Wet runways, unbalanced field (not too many), Assumed Temperature above the environmental limit, and CDL items come from paper V-speed tables.
Like yourself, it's normal policy to use zero wind with the Captain's discretion for use of any Headwind component. Naturally, the worst Tailwind MUST be considered.
FMC speed use is limited to agreement within 3 knots of the Airport Analysis speeds. I don't like it at all, but accept that some (not all) of the possible 3 knots arises from establishing RTOW from "worst case" data blocks in the Airport Analysis, and using actual environmental conditions within the FMC. Also a bit more because the ATOW is rarely right on the Airport Analysis data block limit, but the problem is, "OK, I can understand where this possible 3 knot differential is coming from, but I can't verify any of it in the cockpit"
Then we can get down to obstacle effect upon EOL whilst ADSR is not affected, or interpolation between data sets when multiple obstacles exist.I don't do the Performance Engineering for my "own" aircraft, the B777. I do it for other aircraft. For the aircraft for which I'm responsible, most of the work is unbalanced field, and paper V-Speeds and RTOWs are available for all operations, Dry, Wet, Balanced/Unbalanced, Anti-Skid Inop, Reverse Inop etc., it means a few more kilos of paper to carry, but it puts me well inside the comfort zone. For these aircraft I've written into policy that for Dry, Balanced, no CDL operations, acceptance of FMC speeds within 1 knot is acceptable. That's because the paper speeds are calculated for QNH=1013, whilst the environmental conditions entered into the FMC might just nudge the speeds by 1 knot. Also exact halves are rounded differently for V1 and Vr/V2, e.g. V1=140.5 is rounded down to 140, Vr or V2=140.5 is rounded up to 141.
How is your new South American aircraft? T'would be interesting to see the manner of data preparation and provision from south of the Panama.
Regards,
Old Smokey
Joined: Feb 2000
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From: with the porangi,s in Pohara
Old Smokey
...my question then relates to tailwinds...I fly into Costa Rica,San Jose ..the data on the T/O performance enables me to go with up to a 15kt Tailwind...used to be 10kts,and of course we now take more of a weight penalty...are T/W,s calculated in the same manner as H/W,s?....and if not,how does the T/W component calculated affect FMGC speeds on the A320...we carry the paper versions,yet when I compare the #,s in the paper version as opposed to the FMGC #,s there are sometimes more than 5kts difference....PB
...my question then relates to tailwinds...I fly into Costa Rica,San Jose ..the data on the T/O performance enables me to go with up to a 15kt Tailwind...used to be 10kts,and of course we now take more of a weight penalty...are T/W,s calculated in the same manner as H/W,s?....and if not,how does the T/W component calculated affect FMGC speeds on the A320...we carry the paper versions,yet when I compare the #,s in the paper version as opposed to the FMGC #,s there are sometimes more than 5kts difference....PB
Joined: Jun 2004
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From: Australia
pakeha-boy,
Lousy timing, I'm on the way out the door to some freedom loving people's republic of something or other.
If the paper figures that you refer to are Airport (Runway) analysis speeds, go with them, you may have an unbalanced field.
Tailwind uses 150% of wind component, Headwind uses 50%, the computations are different.
Mutt and John_T can come up with much much more.
The revolutionaries await.....................
Best Regards,
Old Smokey
Lousy timing, I'm on the way out the door to some freedom loving people's republic of something or other.
If the paper figures that you refer to are Airport (Runway) analysis speeds, go with them, you may have an unbalanced field.
Tailwind uses 150% of wind component, Headwind uses 50%, the computations are different.
Mutt and John_T can come up with much much more.
The revolutionaries await.....................
Best Regards,
Old Smokey
Joined: Sep 1999
Posts: 5,552
Likes: 25
From: ME
A 5 kt difference is too much, suggest you investigate if the FMGC speeds are balanced while the paper weight/speed are optimized. Strongly suggest that you use the paper weight/speed combination.
Old_smokey,
Will you please explain this....Assumed Temperature above the environmental limit. Why do you not use the FMC?
The jungle jet comes with one of the best software suites that i've ever seen. Digital AFM, Runway Analysis, Enroute and all manuals available in PDF format. The output was defined by us for commonality, so at least for the purpose of takeoff charts they are identical to our Boeings. Let me know if you have a buddy coming here and i will give you a set.
Hope you enjoyed visiting the revolutionaries
Mutt
Old_smokey,
Will you please explain this....Assumed Temperature above the environmental limit. Why do you not use the FMC?
The jungle jet comes with one of the best software suites that i've ever seen. Digital AFM, Runway Analysis, Enroute and all manuals available in PDF format. The output was defined by us for commonality, so at least for the purpose of takeoff charts they are identical to our Boeings. Let me know if you have a buddy coming here and i will give you a set.
Hope you enjoyed visiting the revolutionaries
Mutt
Joined: Jun 2004
Posts: 1,843
Likes: 0
From: Australia
Hi Mutt,
Not a cop-out, but as I said "I don't do the Performance Engineering for my "own" aircraft, the B777. I do it for other aircraft". As an operating pilot I have a thorough knowledge of the B777 performance aspects, but not the 'deep' knowledge that is required for the other aircraft that I do the P/E for.
Conversation with the Boeing performance people (whilst engaged in discussions on the "other" aircraft) indicates that whilst the aircraft is not certified beyond the environmental envelope, the engines are, and the thrust level attainable at, for example 60°C, is proven, and may be applied to the aircraft operating within the envelope. Their indication is that the FMC does not appropriately address any performance beyond the environmental envelope. You can put your own interpretation on that statement, but in creating programmes myself for other aircraft, things can go awfully awry when it's necessary to exceed the environmental envelope parameters (unknown break points etc.). I've always been too busy to develop the conversation further than that.
On the practical side, however, operations at an assumed temperature of 60°C applied to TO-1, does produce some wildly differing FMC speeds from the Airport Analysis (I've seen up to 10 knots), so I'm happy to accept their rather basic explanation, and operate at the Airport Analysis speeds.
Regards,
Old Smokey
Not a cop-out, but as I said "I don't do the Performance Engineering for my "own" aircraft, the B777. I do it for other aircraft". As an operating pilot I have a thorough knowledge of the B777 performance aspects, but not the 'deep' knowledge that is required for the other aircraft that I do the P/E for.
Conversation with the Boeing performance people (whilst engaged in discussions on the "other" aircraft) indicates that whilst the aircraft is not certified beyond the environmental envelope, the engines are, and the thrust level attainable at, for example 60°C, is proven, and may be applied to the aircraft operating within the envelope. Their indication is that the FMC does not appropriately address any performance beyond the environmental envelope. You can put your own interpretation on that statement, but in creating programmes myself for other aircraft, things can go awfully awry when it's necessary to exceed the environmental envelope parameters (unknown break points etc.). I've always been too busy to develop the conversation further than that.
On the practical side, however, operations at an assumed temperature of 60°C applied to TO-1, does produce some wildly differing FMC speeds from the Airport Analysis (I've seen up to 10 knots), so I'm happy to accept their rather basic explanation, and operate at the Airport Analysis speeds.
Regards,
Old Smokey
Joined: Sep 1999
Posts: 5,552
Likes: 25
From: ME
Sorry Old_smokey, this one kinda slipped away
Their indication is that the FMC does not appropriately address any performance beyond the environmental envelope Operating 5 Boeing aircraft types that utilize the FMC for speed calculations up to 60°/69° (Douglas/Boeing), I’m surprised by that statement. If this is the case, I would have expected a limitation in the AFM.
Mutt
Their indication is that the FMC does not appropriately address any performance beyond the environmental envelope Operating 5 Boeing aircraft types that utilize the FMC for speed calculations up to 60°/69° (Douglas/Boeing), I’m surprised by that statement. If this is the case, I would have expected a limitation in the AFM.
Mutt
