Page 26 - April24

wheel pilot gets distracted and fails to stop crossfeeding when balance is achieved. In fact, he forgets the fuel panel totally and runs the feeding side’s nacelle tank dry. Since this tank is feeding both engines, they both quit nearly simultaneously! Darn! I hate it when that happens!
“But wait!” says our hapless pilot. “I still have fuel on the other side. I’ll use that to get the engines running again!”
Quiz time: Is it easier for the engine-driven pump to suck vapor (air) or liquid (fuel)? I think we can all agree that the engine-driven pumps will draw air before fuel. Only if we turn on the electric boost pump/standby pump on the side with fuel remaining – so that our common fuel manifold, our crossfeed line, is full of pressurized liquid and no air – do we have a chance for an airstart to be successful. Hard to do? No! A critical step that is easy to overlook? Yes!
Now let’s review the “proper” use of crossfeed. Suppose we are returning from Europe and on our leg from Reykjavik to Goose Bay we lose oil pressure and shut down the right engine. The airports in Greenland are below minimums and we have enough fuel to continue to Goose Bay. (By the way, in most cases our range just went up, not down!) As we continue with only the left engine running, the left fuel is decreasing while the right fuel is remaining at the level it had when the engine was secured.
When the left side gets down to, say, 500 pounds, but with the right side still showing 800, we decide to send the fuel from the right side to the left engine. Easy. Right boost pump on, crossfeed open, left boost pump off. Now the right fuel quantity starts decreasing and the left fuel quantity does not change ... just as it should.
A reminder: For you fortunate pilots flying a member of the F90-, 200- or 300-series, the “right boost pump on, crossfeed open” steps mentioned are both done by merely moving the crossfeed switch left toward the engine we wish to feed.
“But wait, something’s wrong! The right fuel pressure warning annunciator is still illuminated!” Relax. That’s normal. When you conduct your first-flight-of-the-day fuel panel checks it is correct for both left and right fuel pressure annunciators to extinguish. But with the right engine actually shutdown and all of the proper checklist “cleanup” steps completed, the right Fuel Firewall Shut- off Valve has been closed. Thus, the pressure from the operating pump cannot be felt at the pressure switch since it is mounted on the fuel filter downstream of the shut-off valve. So how do we know the right pump is really pumping? For all of the models with engine- driven boost pumps, we don’t know ... until enough time has elapsed to confirm that the proper side’s fuel level is decreasing. (For the C90-style fuel system – the system without engine-driven boost pumps – we know the right pump is operating since the left fuel pressure annunciator remained extinguished after we turned off the left boost pump.)
We fly for another couple of hours and now the gauges read 500 pounds left and 200 pounds right. We stop crossfeeding and return to feeding the left engine from its own nacelle tank. Ah, there’s Goose Bay! We make an uneventful single-engine landing and now face the hardest task ... getting to the ramp on one engine!
One last point to mention: Do not worry about fuel being lost even if we failed to close the Fuel Firewall Shut-off Valve on the engine we secured. The condition lever being in cutoff will prevent any fuel from reaching the dead engine’s combustion chamber and then draining overboard.
I hope this review has been enlightening. Questions? Please write and ask them; I will be happy to respond. KA
King Air expert Tom Clements has been flying and instructing in King Airs for over 50 years and is the author of “The King Air Book” and “The King Air Book II.” He is a Gold Seal CFI and has over 23,000 total hours with more than 15,000 in King Airs. For information on ordering his books, contact Tom direct at twcaz@msn.com. Tom is actively mentoring the instructors at King Air Academy in Phoenix.
If you have a question you’d like Tom to answer, please send it to Editor Kim Blonigen at editor@blonigen.net.
24 • KING AIR MAGAZINE
APRIL 2024