Page 25 - April24

You are exactly right: Most POHs do indeed contain this Fuel System Limitation. From an engineering design standpoint, however, I am also right. Namely, the size of the crossfeed line and the supply capability of the boost pump allows for both engines to be fed from one side’s nacelle tank. Please realize, as has been stated by me in previous articles that the POH’s crossfeed limitation comes from legal, not engineering, concerns. Let’s look at this in a bit more detail.
Suppose that one day the FBO’s Jet-A truck breaks down after it had topped the filler caps on the left side but had not yet finished filling the right side. We are left with, say, a 500-pound imbalance. The 300-series has a 300-pound imbalance limitation and the C90B and C90GT-series have a 200-pound limit. (Both of which, in my opinion, are unnecessary.) For the other models, we are still good to go with the 500-pound imbalance. So off we go – with a little aileron trim cranked in – and when safely in cruise we decide to balance the fuel. We do this by crossfeeding, sending fuel from the side with more fuel to both engines until the greater fuel quantity equalizes with the lesser quantity. Step 1: Make sure the electric pump on the feeding side is on. Step 2: Open the crossfeed valve. Step 3: Make sure the electric pump on the other side is off. Step 4: Monitor the fuel quantity gauges over a period of at least 15 to 30 minutes to verify that indeed the side with more fuel is going
down and the side with less fuel is not changing. Step 5: Keep monitoring fuel quantity and stop crossfeeding when balance is achieved!
OK, I admit it. You caught me again, caught me in not following the manufacturer’s checklist. Realize that this article is meant to cover every King Air model. The individual differences are many. For example, in the F90-, 200-, and 300-series, moving the crossfeed switch laterally toward the side to which you want to feed the fuel not only should send power to the NC crossfeed valve and cause it to open but also should turn on the feeding side’s standby pump. It does not, however, turn off the receiving side’s standby pump if it happened to be already on. Another example of differences: In the C90 and earlier style systems the pilot will definitely have to turn off the receiving side’s boost pump since it is normally running at all times. The E90, A100 and B100 probably follow the procedure written above most accurately.
But realize this, readers: There is never a Step 4 or Step 5 in the POH and they are both critically important! There is absolutely no way to truly know that fuel is going from the high side to both engines until the decrease in the higher fuel level is confirmed! Does the POH address this? No! Have you been taught this? Maybe.
As for Step 5, this is where most of the legal team’s liability worries arise. Suppose that an asleep-at-the-
Break through with Ice Shield® Wing De-Ice Boots
22 29 6
High Quality, Reliable Wing De-Ice Boot. Contact an authorized Distributor today for purchase!
IceShield.com • 800-767-6899 • info@iceshield.com
APRIL 2024
KING AIR MAGAZINE • 23