B767 - Fuel Jettison system
 

We operate two B767-300, which have a low capacity jettison rate (Only one pump in each dual pump unit is activated). For those aircrafts the manual mentions that: “Flaps 25 or 30 should not be selected when using a low capacity jettison system”.
Could someone please enlighten me as to what is the reason behind this reasoning? :confused:
Thanks in advance. :)

At the flap setting you mention the turbulent air coming from the wings/flaps causes the jettisoned fuel to spray over the empanage
Apparently this is not ideal :ok:

Thanks for your reply.

Indeed, it sounds quite right, however why the precaution with the low capacity jettison rate system only; is this not so ideal situation avoided with the high capacity jettison system?

dont quote me
 

from memory it also has to do with the fact that fuel will hit the horizontal stab due to the turbulent air from the flaps and cause a buffetting sensation

I can't confirm now but on the fleet of 767 I work with, all have the same limitation whether the jettison system be high or low capacity .

It could just be for standardisation across the fleet because the low capacity came first with the high capacity arriving on aircraft a few years later.

Need to keep it simple:ok:

you will also notice that the jettison tubes have had an extension of 10 inchs, this was a beoing ei to try and direct fuel away from stab,originally they were straight now they have a 20 degree offset

Thank you much for your replies. :ok: