VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

  #1  
Old 01-09-2012, 04:37 PM
ccsmith51's Avatar
ccsmith51 ccsmith51 is offline
 
Join Date: Jul 2010
Location: Orlando, FL
Posts: 1,077
Question Bendix dual mag and ACS A-510-2 questions

I have an O-360-A1F6D in my RV-4, and it has the Bendix dual magneto. I believe that one side has an impulse coupling, but I can't find out how to determine which side it is?

I assume that the left mag is on the left side of the mag housing, when viewed from the rear. If that is the case, which side has the impulse coupling?

The question comes from me getting ready to replace my panel and wiring. I have an ACS A-510-2 ignition switch. The installation instructions I downloaded from Aircraft Spruce say to place a jumper between the two lugs at position 1 if the left mag has an impulse coupling. Position 1 in the photo below is the two terminals close together at the 1:00 position. As can be seen, a jumper is not there.



So, what does this mean? Can the impulse coupling be on the right mag, and then a jumper is not used? If the impulse coupling is on the left mag, and the jumper is not on the switch, what issues does that cause?

Finally, there is an ACS Ignition Switch Service Bulletin SB92-01 out, and a service kit available, but I cannot find when it was issued and whether my switch falls under the SB. Does anyone know how I can tell?

Thanks in advance for the help,

PS: during the rewiring all terminals will be replaced with proper types, attached using a ratchet crimper...
__________________
Chris Smith
Maule M5-180C (Sold)
RV-6 O-360 CS (Sold)
RV-4 O-360 FP (Sold)
Full-time in the other type of RV....
Reply With Quote
  #2  
Old 01-09-2012, 05:04 PM
curtis's Avatar
curtis curtis is offline
 
Join Date: Jan 2005
Location: Kansas
Posts: 384
Default

If that mag is the same as on my O-320-H2AD, the impulse coupling is on the end that mounts to the engine and works for both sides at the same time.
__________________
RV-6A Slider
550 hours +

Build it light and cheap
Reply With Quote
  #3  
Old 01-09-2012, 05:13 PM
ccsmith51's Avatar
ccsmith51 ccsmith51 is offline
 
Join Date: Jul 2010
Location: Orlando, FL
Posts: 1,077
Default

Quote:
Originally Posted by curtis View Post
If that mag is the same as on my O-320-H2AD, the impulse coupling is on the end that mounts to the engine and works for both sides at the same time.
Thanks for the input, Curtis. According to Wikipedia the O-320-H2AD has the Bendix D4RN-2O21 dual magneto. According to the same source, the O-360-A1F6D has the Bendix D4LN-2021.

Interesting that the only difference in the numbers is an "R" for yours, and an "L" for mine. Can anyone shed any light on the differences between the two mags?

If in fact the impulse coupling is for both mags, then the question for the electrical experts is do I need the jumper on the ignition switch?
__________________
Chris Smith
Maule M5-180C (Sold)
RV-6 O-360 CS (Sold)
RV-4 O-360 FP (Sold)
Full-time in the other type of RV....
Reply With Quote
  #4  
Old 01-09-2012, 05:32 PM
MartinPred's Avatar
MartinPred MartinPred is offline
 
Join Date: Nov 2005
Location: Overseas
Posts: 158
Default Left Side

For the O-360 (at least on mine), the Impulse Coupling is on the left side. You don't want the right mag to fire during start to prevent kick-back that will eventually tear up the starter.

You can tell the Bendix with the coupling because it looks like it has about a 1.5" spacer between the mag and the engine block--that's the coupling.

My guess is that the jumper is to make sure the right mag will remain grounded when you have the ignition in the START position. I have independent mag switches so I'm not sure about the internal wiring of a combined switch. But you definitely don't want the right side firing with the starter engaged.

-Matt
402BD
Reply With Quote
  #5  
Old 01-09-2012, 05:46 PM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,340
Default

If both mags have an impulse coupler you do not need the jumper which is how your switch appears to be wired.
__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
Reply With Quote
  #6  
Old 01-09-2012, 06:24 PM
curtis's Avatar
curtis curtis is offline
 
Join Date: Jan 2005
Location: Kansas
Posts: 384
Default

The "L" vs "R" MIGHT be the rotation direction of the drive end?? More research is needed and my magneto book is out at the airport.
__________________
RV-6A Slider
550 hours +

Build it light and cheap
Reply With Quote
  #7  
Old 01-09-2012, 06:28 PM
aerhed aerhed is offline
 
Join Date: Dec 2008
Location: Big Sandy, WY
Posts: 2,567
Default

The L&R refer to the magneto rotation. Since both mags are on a common shaft the impulse coupling retards both mag halves. This means you don't need the little jumper tab on the switch. Both mags will be retarded at start, so both can and should be firing.
__________________
Actual repeat offender.
Reply With Quote
  #8  
Old 01-09-2012, 06:36 PM
Bubblehead's Avatar
Bubblehead Bubblehead is offline
 
Join Date: Jul 2007
Location: Keller, TX
Posts: 1,553
Default shield ground to switch?

I noticed that in the picture the shields for the P-leads are going to the GND post on the switch.

The diagram that ACS has for the switch (shown below) does not show the ground from the P-leads going to the switch GND post. The shields (I think) are grounded to the engine and the engine to the frame and going to the OFF position on the switch grounds the P-leads.

I don't know if having the shields attached to the GRD on the switch does anything bad. My plane (which I bought already built) was wired that way but I changed it to agree with the ACS diagram. I did not notice any change in performance and shut down the engine the first flight of every month using the switch to make sure neither mag stays hot with the switch in OFF. It has always worked correctly.



As an aside, I have the same engine but mine has fuel injection added, and therefore have the same mags and have been wondering the same thing. Do I need the jumper? Right now my key switch does not have it and after 4 years and 350 hours of flying and many starts I have not had a kick back (thankfully).

My experience seems to confirm what Walt and aerhead posted.
__________________
RV-8 180 hp IO-360 N247TD with 10" SkyView!

VAF Donations Made 8/2019 and 12/2019
"Cum omni alio deficiente, ludere mortuis."
(When all else fails, play dead.)

Last edited by Bubblehead : 01-09-2012 at 06:37 PM. Reason: edited for clarity, hopefully
Reply With Quote
  #9  
Old 01-09-2012, 06:56 PM
ccsmith51's Avatar
ccsmith51 ccsmith51 is offline
 
Join Date: Jul 2010
Location: Orlando, FL
Posts: 1,077
Default

Thanks for all the input. It appears that my switch is wired correctly for my particular engine.

Bubblehead, the shields are atached to the ground terminal on the switch, and that terminal is grounded to the airframe close by. The diagram you showed, which is the same diagram that I use, says to ground the shield to the nearest structural member. That is kinda how mine is wired, so I think it will be OK.

Thanks again, all, ain't VAF great!!
__________________
Chris Smith
Maule M5-180C (Sold)
RV-6 O-360 CS (Sold)
RV-4 O-360 FP (Sold)
Full-time in the other type of RV....
Reply With Quote
  #10  
Old 01-09-2012, 06:58 PM
mannanj's Avatar
mannanj mannanj is offline
 
Join Date: Jan 2005
Location: Mtns of N.E. Georgia
Posts: 1,322
Default Mags

I have the same mag. and others are correct in that mag drive retards both the "L" & "R" mags.

I start mine on "both" hoping for better starts. You can start on "L" "R" or "both". I'm guessing that if you jumper from "L" to "R" you wont be able to do a mag drop test. Not studying the prints well, looks like Killing one will probably kill both sides.
__________________
LAUS DEO
Mannan J.Thomason, MSGT. USAF (RET)
VAF788
"Bucket List" checkoff in progress!
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 01:43 AM.


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.