Page 22 - January 2015 Volume 9, Number1

from one tank, run the tank empty, and perhaps have a replay of the 1974 accident! Setting a timer, sticking a post-it note on the instrument panel, moving your watch to the other wrist ... any “bugging” technique such as one of these is a great idea to remind you to go back to normal operation when balance is achieved.
Let me conclude by giving a brief tutorial about sending fuel from one nacelle tank to the opposite engine, or to both engines if you do not have an engine shut down. Although the fuel always originates from the outlet of the nacelle tank, realize that how the wing fuel gets into the nacelle varies quite a bit between the various models. For models with a filler cap near the wingtip, the nacelle tank is simply the lowest member of the set of fuel tanks that comprise the main system. For the LJ-series, the nacelle tank must be fed via the transfer pump or gravity flow, and gravity flow causes 28 gallons on that side to become unusable.
Because of a checkvalve that prevents flow into a nacelle tank from the crossfeed line, also realize that we never flow fuel from the tanks on one side into the tanks of the opposite side. No, we only feed engines with fuel in the crossfeed line, we never flow that fuel into tanks.
So, to crossfeed, first we need a shove coming from the bottom of a nacelle tank, and that push can only be
supplied by an electric boost pump or standby pump. Second, we need a path to the other side: An open crossfeed valve and line. Third, we need to guarantee that an opposing shove is not coming from the other side.
For the LJ-serial number series, just move the crossfeed switch to Open and turn off the boost pump on the low fuel side. For E90s, A100s, and B100s, turn on the high side’s standby pump, move the crossfeed switch to Open, and make certain the low side’s standby pump is off. For the F90-, 200-, and 300-series, merely move the Crossfeed switch left or right, towards the lower side, and verify that both standby pump switches are off.
Here is something of significant importance: Since, with the exception of the 350 model, the crossfeed annunciator only indicates that power is being sent to the valve, not that the crossfeed valve actually opened, we could have a failure of the valve, leading to no crossfeed taking place, yet the annunciator could still illuminate. Similarly, if the feeding standby pump were to stop operation, crossfeed would cease but fuel flow would continue normally, each side feeding its own engine.
Therefore, there is only one 100% accurate verification that you are indeed feeding the high side fuel to the opposite engine or to both engines: The high side fuel quantity goes down and the low side fuel quantity remains constant. Make absolutely certain that you check the fuel gauges regularly and confirm carefully that indeed the high side is decreasing.
Twice in my 42-years of King Air experience, I have discovered airplanes in which crossfeed worked backwards! One case, a 200 had the crossfeed switch mis-wired such that it turned on the incorrect, opposite, standby pump. The other situation, a 350 had the left fuel gauges connected to the right side tanks and vice versa!
In closing, please realize that this article is instructional in nature, meant to increase the reader’s systems knowledge. Be careful out there! KA
About the Author: King Air expert Tom Clements has been flying and instructing in King Airs for over 41 years, and is the author of “The King Air Book.” He is a Gold Seal CFI and has over 22,500 total hours, with more than 15,000 in King Airs. For information on ordering “The King Air Book,” go to www.flightreview.net.
If you have a question you’d like Tom to answer, please send it to Editor Kim Blonigen at kblonigen@cox.net.
20 • KING AIR MAGAZINE
JANUARY 2015