Home > VansAirForceForums

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

- Today's Posts | Insert Pics

Go Back   VAF Forums > Model Specific > RV-12/RV-12iS
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Thread Tools Search this Thread Display Modes
Old 01-08-2019, 08:47 AM
John C's Avatar
John C John C is offline
Join Date: Mar 2005
Location: Moundridge, KS
Posts: 149
Default Effect of fuel pressure on float height

Originally Posted by NinerBikes View Post
Any ideas on if that additional fuel pressure is a consideration in Carb floats on the Bing Carbs turning into sinkers instead of floats? Does that fuel pressure cease to exist once the fuel enters the float bowl, since at that point, the carb jets are now creating lower pressure due to air stream through the throttle bore of the carb.
Fuel pressure at the float needle pushes down on the float arm. The net effect is about 1/3 of the float weight. The depth of the float will increase as the fuel pressure increases.
John Clark
Moundridge, KS
RV-9A 90512 N6699 Sold
RV-12 120323 N6699Z 410 hours
dues paid 2018
Reply With Quote
Old 01-11-2019, 04:49 PM
AJSWA AJSWA is offline
Join Date: Sep 2011
Location: Paraburdoo Western Australia
Posts: 52
Default low fuel pressure

John C and RVBuilder2002 check your PM please.
RV 120573
Reply With Quote
Old 02-03-2019, 05:53 AM
Piper J3's Avatar
Piper J3 Piper J3 is online now
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,025
Default Vapor Lock

I read Kathryn?s Report for continuing safety education. An accident in 2015 in California involved a Czech built LSA with Rotax 912ULS engine. The NTSB said the cause of the accident was attributed to fuel vapor lock which has been discussed many times in this forum.


The airplane manufacturer didn?t include a fuel return line with restrictor as Rotax installation requires. The airplane apparently flew successfully for 300TT and then developed vapor lock.

My takeaway on this accident is that this is analogous to shutting off the electric fuel pump in a RV-12. This topic has been discussed very thoroughly and can be searched for in this forum.

For what it?s worth, I?ll restate my opinion that the RV-12 electric fuel pump should run all the time as designed by Vans Aircraft in order to mitigate vapor lock.

See also?
Jim Stricker
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 610

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
Reply With Quote
Old 02-03-2019, 07:29 AM
Mich48041 Mich48041 is offline
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,058

Quote from NTSB report.
An examination of the fuel system revealed that when pressurized air was fed through the fuel filter, the air would not escape from the upper "y" fitting. Disassembly of the junction revealed that after the fuel filter there was a metered orifice installed that blocked air from continuing through the system
The NTSB report does not say that vapor lock was the cause of the accident.
Joe Gores
RV-12 Flying
Reply With Quote
Old 06-03-2019, 01:30 PM
Join Date: Aug 2014
Location: Mount Vernon, WA
Posts: 81

Originally Posted by John C View Post
The airplane first flew in 2016.

It is good to hear that some using mogas are not having a problem.
I own a 2015 RV-12 SLSA with 220 hours. I have been using high octane no ethanol fuel purchased at KAWO except when I couldn't and then used 100LL. I've never had a fuel pressure problem until I had to start using 100LL last month. Yesterday in a climb it went quite low into the yellow zone and I turned around and landed. My questions are: could the switch to 100LL be part of the problem? What is the risk of the engine quitting during a climb with very low fuel pressure?
RV-12 KBVS Washington State
Due Paid
Reply With Quote
Old 06-03-2019, 05:33 PM
Mich48041 Mich48041 is offline
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,058

The switch to 100LL is likely unrelated. Chances are that the fuel pressure is not really low. Instead the fuel pressure sensor is inaccurate. Verify the fuel pressure before blaming the fuel or fuel pump.
Joe Gores
RV-12 Flying
Reply With Quote

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 02:09 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.