VansAirForceForums  
Home > VansAirForceForums

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

- Today's Posts | Insert Pics

  #1  
Old 07-18-2017, 01:50 PM
kstone kstone is offline
 
Join Date: Jun 2016
Location: Houston, Tx
Posts: 40
Default Mag check

Relatively new owner of a bought -7A. Recently, the left mag shows zero RPM drop during mag check. Could this be an issue? Appreciate any feedback!
Reply With Quote
  #2  
Old 07-18-2017, 01:53 PM
vic syracuse vic syracuse is offline
Super Moderator
 
Join Date: May 2005
Location: Locust Grove, GA
Posts: 2,627
Default

Zero RPM drop could be an indication that the P-lead is broken or the switch is not working properly.
A quick check is to see if the engine will turn off at idle by using the switch. That will verify that the P-lead is good if it turns off. If it stays running then check the P-Lead.
If it does turn off, then I would suspect the switch.

Vic
__________________
Vic Syracuse

Built RV-4, RV-6, 2-RV-10's, RV-7A, RV-8, Prescott Pusher, Kitfox Model II, Kitfox Speedster, Kitfox 7 Super Sport, Just Superstol, DAR, A&P/IA, EAA Tech Counselor/Flight Advisor, CFII-ASMEL/ASES
Kitplanes "Unairworthy" monthly feature
EAA Sport Aviation "Checkpoints" column
EAA Homebuilt Council Chair/member EAA BOD
Author "Pre-Buy Guide for Amateur-Built Aircraft"
www.Baselegaviation.com
Reply With Quote
  #3  
Old 07-18-2017, 02:00 PM
JonJay's Avatar
JonJay JonJay is offline
 
Join Date: Jan 2007
Location: Battleground
Posts: 4,348
Default

Be careful. That Mag could be HOT !
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.

RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
Reply With Quote
  #4  
Old 07-18-2017, 02:23 PM
AndyRV7's Avatar
AndyRV7 AndyRV7 is offline
 
Join Date: Sep 2007
Location: Hudson County, NJ
Posts: 1,092
Default

I'm no expert but you reminded me of my own experience. MY mags were barely dropping during run-up. I had bought the plane as well and after getting some "issues" worked out, it turns out she really needed some attention. At any rate, my mechanic rebuilt the mags and they were way off on timing (among other issues I think). They have been very consistent at around 50 rpm drop now after almost 400 hours.

It seems like you are in need of a rebuild (re-timing at a minimum) or you are running on one mag. Either one should get some quick attention I would think.
Reply With Quote
  #5  
Old 07-18-2017, 02:33 PM
drainge drainge is offline
 
Join Date: Jan 2017
Location: Alameda, CA
Posts: 29
Default

Lean the engine so that you can just get it to 1700rpm, then try the mag check. This will cause a much more significant drop in rpm on the mag check (if the mag is working).

If you still get no drop then, as others have said, you likely have a broken p lead and should be very careful as you have a hot mag.
__________________
Dan Ainge
RV-7A N375M
2019 =VAF= dues paid
Reply With Quote
  #6  
Old 07-18-2017, 02:59 PM
kstone kstone is offline
 
Join Date: Jun 2016
Location: Houston, Tx
Posts: 40
Default

Thanks so much for your responses. Thought I might have been asking a dumb question, but looks like I might have a serious safety problem.
Reply With Quote
  #7  
Old 07-18-2017, 03:33 PM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,687
Default

If you have an electronic ignition on the left 0 drop is normal.
__________________
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, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
Reply With Quote
  #8  
Old 07-18-2017, 03:36 PM
JonJay's Avatar
JonJay JonJay is offline
 
Join Date: Jan 2007
Location: Battleground
Posts: 4,348
Default

If last time you flew and things where fine, and then all of a sudden they are not, my guess is a broken P-lead, usually the terminal. Do Vic's test. Of course this is all assuming standard mags.
If you do find it is a broken terminal, here is a thread that may help avoid this in the future.
http://www.vansairforce.com/communit...ailed+terminal
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.

RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
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 07:03 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.