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.


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

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 08-15-2022, 04:42 PM
greghughespdx's Avatar
greghughespdx greghughespdx is offline
 
Join Date: Nov 2011
Location: Aurora, OR
Posts: 1,225
Default Optional Service Bulletin Kit for RV-12 Main Gear Channel Update

We've released Service Bulletin SB-00040, which can optionally be installed on legacy/original model RV-12 aircraft. The SB-00040 kit includes the parts and instructions needed to proactively add additional reinforcement to the landing gear beam and was developed based on field experience where flight school aircraft subject to repeated hard landings had rivet failure and/or fatigue issues as described in the bulletin.

We have produced a handful of kits that can be used to make the changes described in this service bulletin. Note that this is not a mandatory service bulletin. Van's recommends compliance for operating environments where repeated heavy and unusual landing loads might occur, such as in flight training or on unusually rough landing surfaces.

This service bulletin applies only to the original model RV-12 and is not applicable to the RV-12iS, which utilizes a different design/structure.
__________________
Greg Hughes - Van's Aircraft
Van's web site | Instagram | Facebook
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Building RV-8A since Sept 2014
Dual AFS 5600, Avidyne IFD 440, Whirlwind 74RV, Superior XP IO-360
VAF build thread - Flickr photo album - Project Facebook page
Aurora, OR (EAA Chapter 105)

Reply With Quote
  #2  
Old 08-16-2022, 04:07 AM
rgmwa rgmwa is offline
 
Join Date: Feb 2010
Location: Perth, Western Australia
Posts: 1,722
Default

That looks like quite a bit of work to install. Fortunately, it's not an upgrade that my 12 needs (not yet anyway), but all credit to Vans for putting in the hard work to develop the kit. Listed as $360 on Vans site.
__________________
RV-12LR 912ULS 120346
Reply With Quote
  #3  
Old 08-16-2022, 01:48 PM
Tacco Tacco is offline
 
Join Date: Jan 2017
Location: White Salmon, WA
Posts: 243
Default

If someone had upgraded, or has plans to upgrade, to the gun drilled gear legs, are there any interference or install compatibility issues with this SB kit?
__________________
Steve Morrow
RV-12 N12SM
Builder 121036
White Salmon, WA

2020 Donation Paid
Reply With Quote
  #4  
Old 08-16-2022, 02:23 PM
greghughespdx's Avatar
greghughespdx greghughespdx is offline
 
Join Date: Nov 2011
Location: Aurora, OR
Posts: 1,225
Default

Quote:
Originally Posted by Tacco View Post
If someone had upgraded, or has plans to upgrade, to the gun drilled gear legs, are there any interference or install compatibility issues with this SB kit?
No.

More words to be able to post.
__________________
Greg Hughes - Van's Aircraft
Van's web site | Instagram | Facebook
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Building RV-8A since Sept 2014
Dual AFS 5600, Avidyne IFD 440, Whirlwind 74RV, Superior XP IO-360
VAF build thread - Flickr photo album - Project Facebook page
Aurora, OR (EAA Chapter 105)

Reply With Quote
  #5  
Old 08-17-2022, 09:11 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,780
Default

My aluminum carry-thru gear channel developed cracks at the rear “mouseholes” at ~500TT. I had previously installed SB 12-11-09 per Van’s recommendation. This Service Bulletin added support plates to the bottom side of the u-channel but did not address stress concentrated at the AN5 washer/nut on the top side of the channel.

I’m sure rough landings and/or operating on rough fields adds to this problem, but I have a theory that in-flight loads are also a major contributor.

The spring landing gear leg, with heavy cantilevered wheel assembly, causes an up/down flexing motion – not necessarily fore/aft. Might even happen when airplane leaves the ground, gear drops suddenly, with springing motion up/down before settling. The springing action of the gear leg would be seen by the outboard u-bracket and would be vertical forces at that location. Repetitive up/down force on the u-bracket will cause the thin bottom web of the channel to develop stress cracks that emanates from the mounting holes.

As stated above, I think the root cause of the problem is flight loads and not necessarily ground operations. When the airplane is on the ground all the force loaded onto the gear is in one direction - up. I don’t think heavy braking is to blame because this would impart a vertical force in the “up” direction at the rear mounting bolts. If braking was a contributor, we would see tearing at the front mounting holes. Also, the wheels have an “instant center” when they contact the ground on landing. Even a smooth landing has violent forces when the wheel spins-up at the instant center point of contact on the ground.

In turbulent air, the gear leg flexes up/down with the heavy cantilevered wheel assembly at the far end of the spring gear leg. Constant up/down repetitive forces caused by flight turbulence could easily cause fatigue cracking that we see. This would explain why there is damage even when plane is landed correctly most of time.

Upward motion of the gear leg (i.e. – landing) puts force into vertical web of channel which is good. Downward force of the gear tries to “tear” the u-bracket bolts through the channel floor. The upward force is spread somewhat with the face of the u-bracket that straddles and supports the outboard gear mounting. The downward force is isolated to the AN5 washer and lock nut. It is this small concentrated area of force in the downward direction that is trying to rip and tear the AN5 bolt thru the thin base of the aluminum u-channel. The landing gear is not visible from inside the airplane – but there is a lot of motion going on below the wing during flight. My theory is that the downward force of the landing gear in turbulent flight is trying to rip the AN5 main gear bolts down thru the 3/16” thick extruded aluminum channel. Force is localized at the face of the washer and needs to be spread over a much larger area on top of the channel to eliminate stress concentration. It looks like this new SB finally addressed the root cause of the problem.

Several years ago, a small group of local RV-12 owners developed a set of steel “sandwich plates” that are designed to spread all the forces from the u-bracket into a large area of the carry-thru channel in order to mitigate stress concentration at the AN5 bolt holes. I installed a set of these plates at ~500TT and consider the problem solved...
__________________
-
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 815

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
  #6  
Old 08-17-2022, 05:33 PM
jrock836's Avatar
jrock836 jrock836 is offline
 
Join Date: Nov 2020
Location: Burleson, Texas
Posts: 365
Default

Interesting theory Jim, but I don't see myself doing that extensive SB. I guess everyone has opinions and I fall on the side of believing enough in Van's engineering of the RV12 to be confident that my landing gear is strong enough to handle aerodynamic loads while flying. I guess time will tell for me..
__________________
Joe
2013 RV-12ULS
Fort Worth, TEXAS!
LSRM-A

EAA #1409566
Reply With Quote
  #7  
Old 08-17-2022, 06:02 PM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,906
Default

Quote:
Originally Posted by Piper J3 View Post
The spring landing gear leg, with heavy cantilevered wheel assembly, causes an up/down flexing motion – not necessarily fore/aft. Might even happen when airplane leaves the ground, gear drops suddenly, with springing motion up/down before settling. The springing action of the gear leg would be seen by the outboard u-bracket and would be vertical forces at that location. Repetitive up/down force on the u-bracket will cause the thin bottom web of the channel to develop stress cracks that emanates from the mounting holes.

As stated above, I think the root cause of the problem is flight loads and not necessarily ground operations.
I agree that there are vertical loads applied at this point in flight but disagree that it is a root cause of crack development in the channel.

The loads induced by ground operations are orders of magnitude higher than what would be induced by the gear leg mass in flight, but instead of debating with theories we can look at actual data.
If your theory was correct, every high time RV-12 would be developing cracks in the channel just from all of the flight hours, but they aren't. Otherwise it would not have been offered as an optional change.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop
FAA/DAR
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #8  
Old 08-17-2022, 08:15 PM
PilotBrent PilotBrent is offline
 
Join Date: Dec 2011
Location: Hackettstown, NJ
Posts: 536
Default

Cudos to Van's for making the sig. investment of time to develop and test this optional SB. After reading through 19 pages, I won't be taking it on, but I'll definitely remind myself on short final to avoid slamming the aircraft down on the runway. Those pictures were disturbing - should be shown to every new RV-12 pilot.
__________________
---------------
Brent Connelly
Hackettstown, NJ
RV-12, N913BC - EAA Light Plane Silver Lindy (2016)

2021 VAF Donation, please make yours too!

Check out & subscribe to my Youtube channel for latest RV-12 flying videos...
https://www.youtube.com/channel/UCxQ...Px2I7jmazGdLqg
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 12:15 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.