VansAirForceForums  
Home > VansAirForceForums

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

- Today's Posts | Insert Pics


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

Reply
 
Thread Tools Search this Thread Display Modes
  #11  
Old 07-12-2018, 06:32 AM
n233va n233va is offline
 
Join Date: Jul 2014
Location: Prescott, AZ
Posts: 27
Default

Prop was dynamically balanced. 882 hrs. on prop when it failed. Sensenich has the hub.

Bob
Reply With Quote
  #12  
Old 07-12-2018, 06:49 AM
n233va n233va is offline
 
Join Date: Jul 2014
Location: Prescott, AZ
Posts: 27
Default

Here is the complete narrative of the circumstances of the hub failure on N233VA. The narrative was provided to Van's.

PROP HUB FAILURE IN FLIGHT

Vans Aircraft SLSA RV12 N233VA Serial # S12007 882 hrs TTSN Hobbs .

On, 6/19/2018, while flying from Big Bear California to Prescott, AZ, at 11500 ft. I experienced a harmonic vibration that was different than anything I have experienced in an RV12. Although running with some harmonic vibration, I was able to safely return to Prescott, AZ.

After returning, I removed the top cowl and the spinner. I suspected the prop but also checked the prop blade pitch. The blades had not moved. Checked the slipper clutch and it was at 456 Inch lbs. Checked the torque on the prop bolts and they were all at 240 inch lbs. While checking the torque on the prop bolts a crack was observed on the front hub. After further examination it was determined that there was a crack on both sides of the hub. Once the prop hub bolts were removed, the front hub fell off in two pieces.

The aircraft is equipped with a Sensenich Ground Adjustable Prop 2A0R5R70EN-V. Hub Serial Number 21193C , Blade Serial Numbers 34421/R70E and 34218 /R70E.

I contacted Sensenich and spoke with Don Rowell. He stated that there was a service bulletin for cracks in the hub of earlier model hubs, such as the one on my RV12. I told him the details of my experience and he asked me to send Sensenich the hub and blades. He advised that Sensenich would replace the Hub with a newer version and also replace the pins in the prop blades to fit the new version. Prop was a ďCĒ hub.

The Prop Blades and Hub were shipped to Sensenich for examination. Van's Aircraft was also notified of this incident.

I checked Vans Support site for bulletins/notifications and could not find any reference to Sensenich prop hubs on Rotax engines. I also checked Sensenich. and found one service bulletin (SB2016-06), "Inspection of adjustible pitch Jabiru hubs for cracks". It also references, "2 blade aircraft hubs with pitch cylinder for Jabiru or other direct drive engines". It does not mention Rotax Engines, which are a geared engine. However, this bulletin does show exactly the crack location and propagation of the cracks that occurred in this aircraft.

Feel free to contact me at 928-899-0277 or by email should you have further questions.

Photos Available.

Robert J. Liddell
3110 Adobe Springs Drive
Prescott, AZ 86301
928-899-0277
boblid@icloud.com or bbliddell@cableone.net
Reply With Quote
  #13  
Old 07-12-2018, 07:15 AM
Piper J3's Avatar
Piper J3 Piper J3 is online now
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 933
Default

I didnít sleep well last night after seeing the picture of the broken prop hub and thinking about what could have happened if one blade separated from the hub. The remaining blade would cause horrific imbalance and most likely shake the engine loose from its mount thus causing an uncontrollable CG shift.

So today I have decided that I will not fly my plane again until the prop hub is replaced with the improved design. It is unconscionable that I should have to examine the prop hub every 50 hours to look for an eminent failure mode that is documented and known to the manufacturer.
__________________
-
Jim Stricker
Hinckley, Ohio
PPL/ASEL 1970 Sport Pilot since 2004
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 370

LSRM-A Certificate 2016
Special Thanks to EJ Trucks
Reply With Quote
  #14  
Old 07-12-2018, 08:47 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 7,617
Default

Quote:
Originally Posted by Piper J3 View Post
I didnít sleep well last night after seeing the picture of the broken prop hub and thinking about what could have happened if one blade separated from the hub. The remaining blade would cause horrific imbalance and most likely shake the engine loose from its mount thus causing an uncontrollable CG shift.

So today I have decided that I will not fly my plane again until the prop hub is replaced with the improved design. It is unconscionable that I should have to examine the prop hub every 50 hours to look for an eminent failure mode that is documented and known to the manufacturer.
Everyone is of course entitled to deal with things like this in their own personal way but I suggest people consider the following......

Things designed and manufactured by humans fail.
Failures can be caused by many different things.
As far as I am aware, this mentioned case is the only failure like this with the Sensenich prop installed on a Rotax 912.
It is entirely possible that this one cracked because of a manufacturing defect.
Because the cause is not immediately known, it is entirely appropriate for Sensenich to issue the S.B., but just because they have, doesn't mean that failure is imminent on every Sensenich prop with this style hub.
__________________
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #15  
Old 07-12-2018, 09:10 AM
DHeal DHeal is offline
 
Join Date: Sep 2006
Location: Windsor, California
Posts: 693
Default

I inspected my front hub cover i/a/w the SB and found what appeared to be two cracks in the areas indicated in the SB -- the cracks are very difficult to see. I shipped the hub to Sensenich for their evaluation. My 4.5-year-old RV-12 has 650 hours, the prop was dynamically balanced, and the prop has not been used for pushing/pulling the aircraft on the ground. It will now be interesting to see how Sensenich responds to this issue and how long impacted aircraft will be grounded.
__________________
David Heal - Windsor, CA (near Santa Rosa)
EAA #23982 - EAA Technical Counselor and Flight Advisor; CFI - A&I
RV-12 E-LSA #120496 (SV w/ AP and ADS-B) - N124DH flying since March 2014 - 650+ hours (as of July 2018)!
VAF donation through June 2019.
Reply With Quote
  #16  
Old 07-12-2018, 09:14 AM
BigJohn BigJohn is offline
 
Join Date: Nov 2008
Location: Gloversville, NY
Posts: 1,509
Default Just adding to what Scott said...

... it seems to me that if Sensenich finds that this incident was an anomaly due to manufacturing defect or other cause, the SB for 50 hour inspections might be recinded, or at least eased. I hope the community is kept informed as the analysis by Sensenich proceeds.

Addition: I was still typing when Dave posted just above. Maybe not an isolated incident then. I hope Sensenich is able to react quickly to this situation.
__________________
John Peck, CFII, A&P, EAA Tech Counselor, Flight Advisor.
RV-12 N37JP 120176 Flying since 2012.
VAF paid through 10/2018. Best bargain in town.

Last edited by BigJohn : 07-12-2018 at 09:18 AM.
Reply With Quote
  #17  
Old 07-12-2018, 09:30 AM
Piper J3's Avatar
Piper J3 Piper J3 is online now
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 933
Default

Quote:
Originally Posted by rvbuilder2002 View Post
Everyone is of course entitled to deal with things like this in their own personal way but I suggest people consider the following......

Things designed and manufactured by humans fail.
Failures can be caused by many different things.
As far as I am aware, this mentioned case is the only failure like this with the Sensenich prop installed on a Rotax 912.
It is entirely possible that this one cracked because of a manufacturing defect.
Because the cause is not immediately known, it is entirely appropriate for Sensenich to issue the S.B., but just because they have, doesn't mean that failure is imminent on every Sensenich prop with this style hub.
The possibility of a blade departing, when even a single hub has failed, is too risky for me. Could be manufacturing defect. Could be improper installation. Bottom line is hub design needs to be robust. Sensenich redesigned the hub and eliminated the large hole - we don't know the reason, but suffice to say, the original design is no longer available.
__________________
-
Jim Stricker
Hinckley, Ohio
PPL/ASEL 1970 Sport Pilot since 2004
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 370

LSRM-A Certificate 2016
Special Thanks to EJ Trucks

Last edited by Piper J3 : 07-12-2018 at 09:38 AM.
Reply With Quote
  #18  
Old 07-12-2018, 09:37 AM
Piper J3's Avatar
Piper J3 Piper J3 is online now
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 933
Default

Quote:
Originally Posted by DHeal View Post
I inspected my front hub cover i/a/w the SB and found what appeared to be two cracks in the areas indicated in the SB -- the cracks are very difficult to see. I shipped the hub to Sensenich for their evaluation. My 4.5-year-old RV-12 has 650 hours, the prop was dynamically balanced, and the prop has not been used for pushing/pulling the aircraft on the ground. It will now be interesting to see how Sensenich responds to this issue and how long impacted aircraft will be grounded.
People keep talking about dynamically balancing prop. Yes, this is good practice but not required by the manufacturer. Prop hub is (should be) designed to withstand significant weight difference in a pair of blades. Manufacturer would do over-stress testing for a critical safety-of-flight product.
__________________
-
Jim Stricker
Hinckley, Ohio
PPL/ASEL 1970 Sport Pilot since 2004
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
RV-12 E-LSA #120058 AWC Jul 2012 - Bought Flying Oct 2015 with 48TT - Hobbs now 370

LSRM-A Certificate 2016
Special Thanks to EJ Trucks
Reply With Quote
  #19  
Old 07-12-2018, 10:13 AM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,245
Default

With this type of failure is it feasible that the blade(s) would depart as long as the bolts continue to clamp the ends of the shanks?

Iím not suggesting the problem is not severe or something not to be taken seriously. I am just asking the question.
Reply With Quote
  #20  
Old 07-12-2018, 10:19 AM
AirHound AirHound is offline
 
Join Date: Oct 2006
Location: OFallon IL now, everywhere before
Posts: 198
Default

Quote:
Originally Posted by RFSchaller View Post
With this type of failure is it feasible that the blade(s) would depart as long as the bolts continue to clamp the ends of the shanks?

Iím not suggesting the problem is not severe or something not to be taken seriously. I am just asking the question.
My take they are fixed by thru bolts so immediate BLEW blades less likely...

On the same note....I'll bet cracks will be a challenge to discern....maybe need 10x magnification and or penetrant...All just guessing..
__________________
Doug
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 04:26 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.