18th Jun 2012, 01:34
Just wanting to clarify calculations for W&B and planned fuel burns for flight planning.
I have always used flight fuel (inc reserves etc) as an upper limit and zero fuel as the lower limit. My theory being that if I were to run extremely low on fuel I would know I'm still within W&B limits. You cannot go out of the W&B if your within these values!
It is argued that I should be using only the planned fuel burn for the lower limit? What would the Mr CASA man say??
18th Jun 2012, 01:39
Zero fuel - otherwise your "reserve" would take you out of trim.:hmm:
18th Jun 2012, 02:17
Zero Fuel, accept if you are using fuel as ballast.
18th Jun 2012, 02:27
CASA has, unless now changed, always adopted the view that CG is required to be valid for all fuel loads from empty through to T/O.
Anything else makes not much sense... if you are caught out with a low fuel situation, you really want to add to your problems with W&B worries ?
Ballast situations may dictate a different approach.
18th Jun 2012, 04:43
Always assume worst case scenario, ..... just in case.
So use ZFW and ensure it is still in limits.
As John said, If emergency situation saw you that low on fuel
( into reserves) do you want an aircraft that may very well be now having control and stability issues with an out of envelope cg???
There has been several fatal accidents here in Aust alone where an out of envelope cg has led to those issues and loss of the aircraft, some in cruise flight.
Too frightening a situation for me.:uhoh::uhoh::uhoh:
18th Jun 2012, 06:33
Inputs to the Douglas/Boeing 717 FMC, with regards to W&B and fuel are TOMAC & ZMAC (take off gross wt MAC & Zero fuel weight MAC).
18th Jun 2012, 23:50
Similarly, my mob W&B calcs plot the ZFMAC and TOWMAC.
The only complication I can think of is a low fuel state with unusable fuel trapped by equipment failure in a trim tank somewhere, but I'm sure the manufacturer would have accounted for it in the design.
Maybe someone who flies such a type could add more.