What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

D180 oil pressure

P51krause

Member
Hi there. Question regarding POH and D180. POH has you power on D180 first using back up battery. After start look for oil pressure to 12psi within 10 seconds. Then turn on avionics master. I have found no oil pressure on back up battery, but as soon as I turn on the avionics master switch, presto Oil pressure. Previous thread notes sending unit is not powered until the avionics master switch is on. Is this a typo or POH mistake? Any thoughts appreciated. Cheers and fly safe. Long time listener first time poster.
Michael.
 
It is not a typo, but it is a mistake. Shutting off the avionics was a good idea back in the 1950s shortly after transistors were first invented. The voltage sag during engine cranking destroyed those early transistors. Modern transistors and avionics have no such vulnerability. But the advice to shut off avionics during engine start keeps being passed on from instructor to student because that is what they were always taught. I do not know of any avionics manufacturer that recommends shutting off their units prior to engine start. If you find one, please post the name of the manual and page number. And do not buy their inferior products. I have started my engine hundreds of times, always with the avionics turned on, except once when my biennial-flight-review instructor told me to turn it off. I have since removed the avionics switch from my RV-12. It is an unnecessary single point of failure. By the way, there is no such thing as a voltage spike while engine cranking. It is a voltage sag.
Read Bob Nuckolls' post in THIS THREAD.
 
Shutting off avionics to reduce the load on the battery during starting is not a valid reason. Adding 10 amps to hundreds of amps of starting current is not going to make any difference unless the battery is low. In that case, the battery should be charged or replaced prior to flight.
 
Back
Top