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  #21  
Old 03-11-2019, 05:14 PM
Bavafa Bavafa is offline
 
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Location: Sacramento, CA
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It is interesting that both have broken off right where there is a separation area in the wheel pants. There is hole at the bottom of the wheel pant that needs to be clear of any paint/epoxy to make sure the area can equalize for pressure.

Lastly, I suggest to make sure the stop bracket is installed correctly. VANs had a SB for that a couple of years ago as some folks had installed that backward which allowed for greater turn on the wheel. This could contribute in larger oscillation from stop to stop.
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  #22  
Old 03-11-2019, 05:33 PM
Kyle Boatright Kyle Boatright is online now
 
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Quote:
Originally Posted by Bavafa View Post
It is interesting that both have broken off right where there is a separation area in the wheel pants.
Help me understand what you're saying here.
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  #23  
Old 03-11-2019, 06:12 PM
Bavafa Bavafa is offline
 
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Quote:
Originally Posted by Kyle Boatright View Post
Help me understand what you're saying here.
The nose wheel pants unlike the mains has a barrier inside, made of glass, that makes the back side into a closed off compartment. Under the wheel pant there is 1/8" hole drilled that needs to be kept open to equalize the pressure in that area/compartment.

Both pictures in this thread that show broken wheel pants, seem to have broken off right where that barrier is.

Probably far fetched but it is possible if some moisture accumulates in there and does not drain, thus turning into an additional mass, could exacerbate the force induced by the shimming.

Might not be describing it well, but if you look at the inside of your nose gear fairing, you will know what I am describing here.

Edit: Looking at the pictures again, it looks like the separation/brake line is fore the barrier by at least a couple of inches.
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Last edited by Bavafa : 03-11-2019 at 06:15 PM.
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  #24  
Old 03-12-2019, 04:36 AM
Michael Wellenzohn's Avatar
Michael Wellenzohn Michael Wellenzohn is offline
 
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Quote:
Originally Posted by leok View Post
Was the bracket not captured, or did it pull out with the shimmy? I assume if it puled out, the nut/bolt would be loose.
Im afraid it was not captured.
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  #25  
Old 03-26-2019, 07:09 PM
Tim Lewis Tim Lewis is offline
 
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Quote:
Originally Posted by Michael Wellenzohn View Post
Hi all,

I wanted to share a surprising shimmy experience and would like to know if anyone had ever had a similar experience with the —10.

<snip>

See picture below

https://photos.app.goo.gl/XHUVXg8LSYxd1ZiL8

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Michael
You are not alone. Several folks have reported the same thing. I was lucky to catch mine several years ago at the "crack" stage (prior to separation), in the same place. Following the advice of others, I repaired by adding a couple of layers of fiberglass to reinforce that area (glassed to bulkhead, then forward a few inches). That has proven sufficient to keep my nose wheel fairing from cracking.

In a perfect world, the nose wheel is held off until very low speed, and shimmy is less likely to occur. In the real world we have some landings where the nose wheel comes down at high speed and/or firmer than optimal, shimmy occurs, and the fairing is at risk of breaking right where yours broke.

I suggest adding fiberglass reinforcement in that area on a new or repaired wheel fairing.
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  #26  
Old 03-28-2019, 06:20 AM
togaflyer togaflyer is offline
 
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Cirrus and Van’s have Service Bullitains on tire pressur to help reduce nose wheel shimmy. I run mine about 5 lbs less than spec with good results. FYI, Since this is dated back in 07 there is no mention of the -10. I read the Cirrus SB which also addresses the same issue and recommendation with the nose wheel.

VAN’S AIRCRAFT, INC.
14401 NE Keil Road, Aurora, Oregon, USA 97002
PHONE 503-678-6545 • FAX 503-678-6560 • www.vansaircraft.cominfo@vansaircraft.com
Service Letter: November 9, 2007 Subject: Nose gear
Models Affected: RV-6A, 7A, 8A, 9A
References:
1. Van’s Aircraft Service Letter dated March 10, 2005
http:// www.vansaircraft.com /pdf/letters/nosegear.pdf
2. Van’s Aircraft Service Bulletin 07-11-09 dated November 9, 2007
http://www.vansaircraft.com/pdf/sb07-11-9.pdf
3. NTSB Structures Study, Case No.: ANC05LA123
http://www.ntsb.gov/publictn/2006/RV_Study.pdf
Note: To better understand the topics covered in this service letter, it is recommended that the readers familiarize themselves with the reference material above.
In March, 2005, Van’s Aircraft issued a service letter describing the development and revisions made to the nose gear legs used on all two place, tricycle RVs (see reference 1). This service letter went on to describe the most recent revisions in the nose gear leg design, a shortened gear leg axle and shorter fork. This version of the nose gear leg and fork have been shipped as standard components in Van’s kits since February, 2005. As of October, 2007, there have been no reported nose gear incidents involving this combination of leg and fork.
On June 21, 2007, The NTSB released a Structures Study of the pre-shortened nose gear leg/fork combination (See reference 3). This report concluded that, though the nose gear strut has sufficient strength to perform its intended function, mechanical factors and piloting technique that reduced the nose gear leg strut to ground clearance increased the likelihood of an incident.
In light of the absence of incidents involving the current, shortened nose leg/fork combination and the results of the NTSB Structures Study, Van’s Aircraft, Inc. issued Mandatory Service Bulletin 07-11-09 (see reference #2). SB 07-11-09 requires replacement (or modification) of any U-603-2 (or older) nose gear leg and the replacement of the corresponding fork (WD-630) prior to or during the next annual condition inspection. The upgraded leg/fork combination is notably lighter than the previous version and allows an additional inch of clearance between the fork/axle assembly and runway surface. Instructions for completing this conversion can be found in SB 07-11-09.

As pointed out in the previous service letter regarding this subject, pilots should always practice good judgement and technique to limit the loads on landing gear structures. Other operational suggestions to help pilots reduce risks are listed below.
Note: If an RV has been modified in any way from the plans supplied by Van's Aircraft, the builder/operator is responsible for determining if the operational changes associated with these modifications will result in safe operation of the aircraft.
1. RV’s are designed to utilize Lycoming engines of specified horsepower and weight. Changes to the aircraft that result in higher static nose gear weights than previously demonstrated by Van’s Aircraft’s testing will result in a higher probability of nose gear incidents.
2. Always operate your aircraft with the nose wheel fairing installed.
3. Nose wheel tire pressure should be maintained between 25psi and 35psi.
4. Keep the stick fully back when taxiing, especially after touchdown.
5. The nose gear on tricycle gear aircraft are not intended nor designed to sustain ‘landing’ loads. The nose gear is NOT a landing gear and is intended for ground maneuvering after touchdown and deceleration.
6. Do not rely on hearsay or second hand information about runway and taxiway conditions. Do NOT operate your aircraft on an ‘unknown’ surface!
7. Be proficient at ‘go-arounds’ in the event a landing becomes unmanageable.
Appendix A of this Service Letter contains charts that allow a pilot/operator to estimate the weight on the nose gear given the CG and aircraft gross weight. Operation within these limits is highly recommended and will provide a greater margin of safety should “mechanical factors and/or pilot technique” add to the normal, gravity induced load on the nose gear.
Using the Nose Gear Weight Charts: (example depicted on RV-7A chart)
1. Calculate your gross weight and CG for a given flight.
2. Identify the chart specific for your aircraft. (RV-6A,7A,8A or 9A)
3. On the chart, follow the appropriate Gross Weight line vertically until it intersects the
appropriate CG line. Move horizontally left from this point to arrive at the estimated
nose gear weight.
4. Gross weight and nose gear weight should both fall within the non-shaded area of the
chart.
5. These charts are estimated using ‘typical’ RV engine and constant speed propeller
configurations for each model.
Appendix A: Nose Weight Charts

RV-6A
Weight on Nose Wheel vs Gross Weight & CG Location
1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 GROSS WEIGHT (lb)
CG = 68.7" aft of datum / 15% chord
CG = 69.86" aft of datum / 17% chord
CG = 71.02" aft of datum / 19% chord
CG = 72.18" aft of datum / 21% chord
CG = 73.34" aft of datum / 23% chord
CG = 74.5" aft of datum / 25% chord
CG = 75.66" aft of datum / 27% chord
CG = 76.82" aft of datum / 29% chord
500 400 300 200 100 0 WEIGHT on NOSEWHEEL (lb)

RV-7A
Weight on Nose Wheel vs Gross Weight & CG Location
Weight on Nosewheel = 369 lb
Intersect
Gross Weight line with CG = 82.18" line
1100 1200
N137RV LOADING EXAMPLE:
Fuel = 42 gallons / 252 lb Pilot = 170 lb
Passenger = 138 lb Baggage = 0 lb
1300 1400
Gross Weight = 1709 lb
CG Location = 82.18" / 21%
1500 1600 1700 1800 1900 2000 GROSS WEIGHT (lb)
Step 1: Draw vertical line at Gross Weight. If Gross Weight > 1800 lb then FLIGHT PROHIBITED Step 2: Locate point where vertical line intersects CG line.
Step 3: Read Weight on Nosewheel opposite Gross Weight / CG intersection point.
If Weight on Nosewheel > 375 lb then FLIGHT PROHIBITED
CG = 78.7" aft of datum / 15% chord
CG = 79.86" aft of datum / 17% chord
CG = 81.02" aft of datum / 19% chord
CG = 82.18" aft of datum / 21% chord
CG = 83.34" aft of datum / 23% chord
CG = 84.5" aft of datum / 25% chord
CG = 85.66" aft of datum / 27% chord
CG = 86.82" aft of datum / 29% chord
500 400 300 200 100 0 WEIGHT on NOSEWHEEL (lb)
Gross Weight = 1709 lb

RV-8A
Weight on Nose Wheel vs Gross Weight & CG Location
1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 GROSS WEIGHT (lb)
CG = 78.7" aft of datum / 15% chord
CG = 79.86" aft of datum / 17% chord
CG = 81.02" aft of datum / 19% chord
CG = 82.18" aft of datum / 21% chord
CG = 83.34" aft of datum / 23% chord
CG = 84.5" aft of datum / 25% chord
CG = 85.66" aft of datum / 27% chord
CG = 86.82" aft of datum / 29% chord
500 400 300 200 100 0 WEIGHT on NOSEWHEEL (lb)

RV-9A
Weight on Nose Wheel vs Gross Weight & CG Location
1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 GROSS WEIGHT (lb)
CG = 77.95" aft of datum / 15% chord
CG = 79.01" aft of datum / 17% chord
CG = 80.07" aft of datum / 19% chord
CG = 81.13" aft of datum / 21% chord
CG = 82.19" aft of datum / 23% chord
CG = 83.25" aft of datum / 25% chord
CG = 84.31" aft of datum / 27% chord
CG = 84.84" aft of datum / 28% chord
500 400 300 200 100 0 WEIGHT on NOSEWHEEL (lb)

Last edited by togaflyer : 03-28-2019 at 06:26 AM.
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