VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 05-10-2019, 04:29 PM
P51krause P51krause is offline
 
Join Date: Jan 2019
Location: Camarillo
Posts: 2
Default D180 oil pressure

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.
Reply With Quote
  #2  
Old 05-10-2019, 05:41 PM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,823
Default

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.
__________________
Joe Gores
RV-12 Flying
Reply With Quote
  #3  
Old 05-10-2019, 05:53 PM
MMiller MMiller is offline
 
Join Date: Oct 2010
Location: Babylon NY
Posts: 45
Default

Your system is functioning correctly. On the D-180 version the oil pressure sensor is powered from the EFIS fuse and is activated with the avionics switch. It looks like Vanís updated the the start procedure with a sequence that is not compatible with the D-180 beginning with POH-R10.

You need to turn your avionics switch ON before cranking the engine.
Reply With Quote
  #4  
Old 05-10-2019, 06:23 PM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,823
Default

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.
__________________
Joe Gores
RV-12 Flying
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 01:06 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.