Hope nobody minds that I have dragged this up from the dead.
But the Aux tank limitation as per what I read from a Beechcraft Rep is this.
Good Morning All,
I too, am late to this party and thought I would offer official Beechcraft comments to this discussion regarding fueling procedures on the King Air B200 and B300. Because this question has come up numerous times at King Air Technical Support through the years, we published this article in the 2007-02 King Air Communiqué and I hope that it helps.
King Air Fueling Procedures ATA 28
200/300 Series
Technical Support receives questions regarding the fueling procedures for the King Air 200 and 300 series aircraft. The King Air Pilot’s Operating Handbook has the following warning, although the wording may vary from POH to POH, they generally say the same thing:
Warning
Do not fill the auxiliary tanks unless the main tanks are full.
There are some technical, operational and structural reasons for this warning.
• If you were to fill the auxiliary tanks only and fill the airplane with people and cargo, the
total load would be concentrated in the fuselage and the center section. This is not a
desirable condition since the wings would not be “loaded”. By flying with the wings full of
fuel, the fuel load would act as a shock absorber to the loads exerted through out the
structure of the wings. The total load is also spread across the whole wing spar system.
• The King Air fuel system will empty the auxiliary tanks first to keep the load spread
across the spar system.
Doug Bowlsby
Pacific Northwest Propeller Field Representative
Beechcraft Corp
Hope that answers that question
