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happens on the ground, and that if you are able to get fuel streaming through the FCU, it will keep going. In other words, if you can keep your oil temperature from going too high, you’ll keep your fuel temperature in a viable range for proper FCU function. Once the FCU gets going, it won’t quit.
Inside the FCU is a labyrinth of diaphragms that cannot operate properly with super-heated fuel. The goal is to keep the fuel from becoming too hot before the engine is asked for full takeoff power. Once the FCU gets going, there is so much fuel going through the oil-to-fuel heater that the fuel cannot become super-heated.
So what happened to that King Air pilot with the urgent call? Here is what he did: He asked the tower for at least one minute after receiving clearance to take off. He taxied out on one engine only with his ice vanes stowed (up). After receiving clearance for takeoff, he started his “problem” engine. In doing so, he kept the oil temp down enough for the fuel temp to be acceptable to the FCU. The engine came up to full power and he was good to go.
He had suggested flying over to my shop but I told him he would be better off flying home and having his oil-to-fuel heater addressed there. Once safely home, he called me and thanked me profusely.
A Safe Work-Around
Before I go any further, let me stress here that I am all about safety. I do not advocate risky procedures or maverick bravado in the cockpit in any way, shape or form – period. That said, if you understand the systems that operate your King Air, there are certain instances where you can safely work around a problem until proper maintenance can be done. This is one of those instances, provided you diagnose it correctly.
First you must troubleshoot the fuel bowl on the HP fuel pump. Do not, under any circumstances, simply assume that you have an oil-to-fuel heater problem. You must check that fuel bowl after a 10-minute ground run. If it’s boiling hot, you’ve got a bad vernatherm in your oil-to-fuel heater. Next, you let everything sit and cool down. Your oil temp needs to get down to at least 40oC.
Let the tower know that once you receive clearance for takeoff, you’ll need an additional minute to get going. Taxi out on your “good” engine only, with the ice vanes up (this helps keep your oil temp from red lining, which in turn keeps your fuel from super heating). Once you receive clearance, fire up the other engine. If you get all the proper indications, and you see that engine is now making power, it means you have ample fuel streaming
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22 • KING AIR MAGAZINE
AUGUST 2024