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If the vernatherm inside the oil-to-fuel heater is bad, it continues to heat the fuel as if the aircraft was at altitude and not on the ground with a triple digit OAT. This doesn’t allow the FCU to function and the engine will not make power.
through the oil-to-fuel heater and it won’t have time to super heat on its way to the FCU. Once airborne, the air going over the oil cooler will keep the oil temp down and the engine will operate normally.
Many of you who operate routinely in cooler climates could have a bad vernatherm in an oil-to-fuel heater and have no clue. It will never rear it’s ugly head until you get into really hot conditions on the ground.
When In Doubt, Don’t Go
A little knowledge can be a dangerous thing, and so it is with a measure of trepidation that I even address this topic of working around a bad vernatherm in an oil-to-fuel heater.
My mantra is “When in doubt, don’t go.” If you are unclear about how an FCU operates – don’t go. If you do not understand exactly what the oil-to-fuel heater does and why – stay put. If you cannot describe how the oil cooler works, please, stay on the ground.
Imagine that you encountered a no-power situation on the ground in hot weather, you felt certain it was correctly identified as an oil-to-fuel heater problem, but you still
don’t feel comfortable with the work-around procedure; again, I say don’t go! Wait until early the next morning when the OAT is at its lowest. Check the problem engine to see if it fires up normally. If it does, then use your best judgment on how to proceed at that point. If you have any doubts, anywhere along the line, then don’t go. Do whatever it takes to get a knowledgeable mechanic on the aircraft to take care of things.
The good news is: It’s fixable. It’s a King Air. They’ve been around for a while.
Keep cool and fly safely. KA
Dean Benedict is a certified A&P, AI with 50 years experience in King Air maintenance. He was an inaugural inductee to the King Air Hall of Fame. He owned and ran Honest Air Inc., a “Beechcraft maintenance boutique” with a strong following of King Airs, for 15 years. Currently, with BeechMedic LLC, Dean and his wife, Lisa, consult with owners, pilots and mechanics on King Air maintenance issues, troubleshooting and pre-buys. Dean performs Expert Witness work on request. He can be reached at 702-524-4378, or via email at dr.dean@beechmedic.com.
AUGUST 2024
KING AIR MAGAZINE • 23