octupus rtow charts

[ssflying]

hi,just a basic question.Presently on our A319s we use the weight entry octupus charts.I want to know for a weight like 59 t,do we interpolate between the boxes for 58t and 60 t even if they have different limit codes for eg 2/7 and 3/7.Intially in our ground school we were taught that we could only interpolate between the weight boxes which had similar limit codes.In case of different codes we were asked to simply move on to the higher weight boxes and to extract the speeds and flex.However in the last two years we have been advised that interpolation between weights with diff codes is allowed although no reasons were given for this change in the procedure.Thanks

[john_tullamarine]

Generic answer as I don't have the specific data.

The short answer should be "no".

The problem is that the two limits will have different curves and, unless you plot both lines, you have no idea where the lines are going.

Interpolating between two points, one on each line, is somewhat meaningless as there is no line between the two points ?

[Hoangminh90]

Do you have any document for explaining the limitation codes . I do not understand it clearly

[vilas]

ssflying
The Airbus answer is given below:


•Yes, because


4the automatic temperature chart used to build the weight chart is accurate enough (slight trend below Tref, step of 2°C above Tref)

[Bkdoss]

I can understand the predicament. I was confused for a while too until I stumbled upon this ppt. I'm sharing the link here. This should help you I guess. Airbus clearly says you can interpolate for different limiting codes.

http://dream-air.ru/new/pilotam/WebConference-01-RTOLW_FAQ_takeoff.ppt

But the question which I've not been able to find an answer to is, how can we do an accurate interpolation when you are left with very little time to calculate as most of the time the trim and loading sheet comes in at the last minute. In such a scenario isn't it advisable to take the speeds for the higher take off weight because it can never happen that the speeds for a higher take off weight can adversely impact flight safety.

Say in a typical scenario suppose speeds for 52t are 113,129,134 and for 54t are 133,135,141 there's a wide spread between the figures and if I, in haste, erroneously interpolate for 53t on the lower side then I might not have sufficient stall margins for v2. Isn't it judicious in such a condition to take the speeds for higher weights?

Ssflying... Are you 'Nelly' by any chance?

[vilas]

The answer I gave is from the same presentation.