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 04-21-2018, 01:22 PM
rjcthree's Avatar
rjcthree rjcthree is offline
 
Join Date: Jan 2007
Location: Bay Village, OH
Posts: 914
Default AP servo mechanically locked

Preflighting today found my ailerons locked in place. All power to the A/C was off. Troubleshooting led to finding the AP roll servo mechanically locked. Disconnecting the servo arm from the aileron belcrank resumed normal operation of the ailerons. Servo itself remained locked until power was turned on. At that point the servo seemed to act normally, no error codes. I removed the servo. Since removing the servo, I can?t replicate the mechanical locking. It?s going back to Dynon.

Has anyone else experienced mechanical locking of a servo without power? I should note that the AP was used on the previous flight to this one, and functioned normally.
__________________
Rick
RV-9A N183RC/90432: tip-up, O320H2, Ellison, Dynon D180, CPi2, Sen GA, at KLPR
RV-8 83718, wing kit, tanks done, with a four year plus plan - on hold due to home move
2011-2021 VAF contributor
Reply With Quote
  #2  
Old 04-21-2018, 02:21 PM
az_gila's Avatar
az_gila az_gila is offline
 
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
Question

Could the linkage have moved (bumped) into an over-center condition?
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
Reply With Quote
  #3  
Old 04-21-2018, 04:11 PM
rjcthree's Avatar
rjcthree rjcthree is offline
 
Join Date: Jan 2007
Location: Bay Village, OH
Posts: 914
Default Travel limit bracket was in place

Gil, the travel limiting bracket was in place. The servo locked in about the neutral position of both ailerons and servos. Part of me wonders if the limit bracket screws may be path of the question, but I used the Dynon provided screws and spaced with a washer. I?m sending it as installed to Dynon.

I?m worried they won?t find root cause.
__________________
Rick
RV-9A N183RC/90432: tip-up, O320H2, Ellison, Dynon D180, CPi2, Sen GA, at KLPR
RV-8 83718, wing kit, tanks done, with a four year plus plan - on hold due to home move
2011-2021 VAF contributor
Reply With Quote
  #4  
Old 04-22-2018, 01:44 AM
RV10inOz's Avatar
RV10inOz RV10inOz is offline
 
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,284
Default

I will bet, a small chocky frog, that your servo has been corroded internally from condensation build up, and has seized.

It has happened before, and on ROLL.

Make sure you alert this to Dynon's AP engineer Lawrence Doan.

I am not sure how you stop it. These days they have a metallic sticker covering the hole in the end shield of the motor to stop drips getting in, but condensation is hard to stop.

All that you can do is put a drain hole in to let moisture out.

Having done Beta Testing for Dynon in the past, this was not part of the test plan, but I did participate
__________________
______________________________

David Brown

DYNON Authorised Dealer and Installer


The two best investments you can make, by any financial test, an EMS and APS!
Reply With Quote
  #5  
Old 04-22-2018, 05:24 AM
rjcthree's Avatar
rjcthree rjcthree is offline
 
Join Date: Jan 2007
Location: Bay Village, OH
Posts: 914
Default Corrosion

David, corrosion is possible. My hanger isn’t the best when it comes to rain intrusion, and while my airplane doesn’t get wet, it’s humid, especially with the temp swings we’re having day to night. The servo was manufactured in 2010 if I’m reading the motor date code correctly, and it has no sticker over the motor shaft hole. I will contact Dynon as you suggest.

Update: servo Locked up overnight sitting in my kitchen in a box. I didn’t imagine the whole thing. Last evening, it moved freely, this morning locked tight. There is the smallest amount of gear lash in the arm, suggesting the output shaft is free, but beyond that.....

On the other hand it was kinda nice hand flying it this smorning, not having the temptation to use the AP.
__________________
Rick
RV-9A N183RC/90432: tip-up, O320H2, Ellison, Dynon D180, CPi2, Sen GA, at KLPR
RV-8 83718, wing kit, tanks done, with a four year plus plan - on hold due to home move
2011-2021 VAF contributor

Last edited by rjcthree : 04-22-2018 at 11:53 AM.
Reply With Quote
  #6  
Old 04-22-2018, 11:26 AM
Ironflight's Avatar
Ironflight Ironflight is offline
VAF Moderator / Line Boy
 
Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,397
Default

Quote:
Originally Posted by rjcthree View Post
David, corrosion is possible. My hanger isn?t the best when it comes to rain intrusion, and while my airplane doesn?t get wet, it?s humid, especially with the temp swings we?re having day to night. The servo was manufactured in 2010 if I?m reading the motor date code correctly, and it has no sticker over the motor shaft hole. I will contact Dynon as you suggest.

Update: servo Locked up overnight sitting in my kitchen in a box. I didn?t imagine the whole thing. Last evening, it moved freely, this morning locked tight. The is the smallest amount of gear lash in the arm, suggesting the output shaft is free, but beyond that.....

On the other hand it was kinda nice hand flying it this smorning, not having the temptation to use the AP.

Just a suggestion - when you pack it up, put labels and signs and notes that are imp0ossible for the ?unpacker? at Dynon to ignore that say ?don?t move the output arm until on a test bench?. Since you?ve managed to recreate the problem, wouldn?t it be nice for the technician to see it that way, and not have someone in the mail room grab it and ?unbind it? without thinking......

Curious about the root cause for this!

Paul
__________________
Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
Reply With Quote
  #7  
Old 04-22-2018, 12:04 PM
rjcthree's Avatar
rjcthree rjcthree is offline
 
Join Date: Jan 2007
Location: Bay Village, OH
Posts: 914
Default Thanks and ?

Paul, good suggestion. I see cardboard surgery in my future! It beats cleaning the garage.

David, what in the great googly-moogly is a chocky frog? I?m leaping to a Harry Potter reference?
__________________
Rick
RV-9A N183RC/90432: tip-up, O320H2, Ellison, Dynon D180, CPi2, Sen GA, at KLPR
RV-8 83718, wing kit, tanks done, with a four year plus plan - on hold due to home move
2011-2021 VAF contributor
Reply With Quote
  #8  
Old 04-22-2018, 02:33 PM
Jesse's Avatar
Jesse Jesse is offline
 
Join Date: May 2005
Location: X35 - Ocala, FL
Posts: 3,683
Default

THis type of situation is exactly why these servos have sheer screws. I haven?t seen this before on a Dynon servo, but I have with another brand, although not a tight lock up, just significant drag. Whoever at Dynon gives you the RMA, make sure hey know the symptoms and make sure they note in the RMA notes that it sometimes does and sometimes doesn?t lock up.
__________________
Jesse Saint
Reply With Quote
  #9  
Old 04-22-2018, 04:43 PM
rjcthree's Avatar
rjcthree rjcthree is offline
 
Join Date: Jan 2007
Location: Bay Village, OH
Posts: 914
Default Lock torque

I can’t tell you exactly what the breakaway torque was, but while it was still installed I opted to remove the push rod from the servo arm with a torque wrench. While not perfect in technicqe, as it’s a click type, it’s calibrated and the removal torque was greater than the 25 in-lb setting, and the servo did not move. The other end connecting to the bell crank was already free. I admit I didn’t lean on it too hard while it was still connected. I wasn’t going to fly it that way even if it broke loose.

It’s boxed, pushrod protected from bumping.
__________________
Rick
RV-9A N183RC/90432: tip-up, O320H2, Ellison, Dynon D180, CPi2, Sen GA, at KLPR
RV-8 83718, wing kit, tanks done, with a four year plus plan - on hold due to home move
2011-2021 VAF contributor
Reply With Quote
  #10  
Old 04-22-2018, 10:44 PM
RV10inOz's Avatar
RV10inOz RV10inOz is offline
 
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,284
Default

https://www.cadbury.com.au/products/...ry/freddo.aspx
__________________
______________________________

David Brown

DYNON Authorised Dealer and Installer


The two best investments you can make, by any financial test, an EMS and APS!
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 10:58 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.